down pipe twin dump or single
04 December 1999, 05:38 PM
#1
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my friend firefox has been giving me a lot
of tuning tips - very helpful
advice was to get a down tube and then move on to vf-23 turbo.i see two options
scoobysport single dump or mrt twin dump
bmp at 900 aud- too rich for me
pe at 282 bp - same.
is there any difference in preformance between the two, single dump or twin dump?
eitan
of tuning tips - very helpful
advice was to get a down tube and then move on to vf-23 turbo.i see two options
scoobysport single dump or mrt twin dump
bmp at 900 aud- too rich for me
pe at 282 bp - same.
is there any difference in preformance between the two, single dump or twin dump?
eitan
04 December 1999, 06:29 PM
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This has been of interest to me, and something I have asked ScoobySport and PE about....(why doesnt that surprise you..groan..)
Hows about we discuss the pros and cons of each..I doubt we'll arrive at a "this is best for sure" answer..
Background.
Have a looksie at the back of the turbo. The gases exit from 2 possible locations..the turbo-impeller blades (J - whats this really called?) and the wastegate. The wastegate is smaller so we can assume less flow is required here - certainly excess exhaust gases only exit here when full boost is achieved.
The wastegate is opened/closed by a small flap connected ultimately to the actuator/diaphragm. When fully open the flap is at quite an acute angle..approx 30-40 degrees ?
So consider what will happen to the exhaust gas exiting the wastegate. It will hit the flap and be directed off at an angle. If you look at the twin-dump design you might argue that the flap obscures the exit hole ! Also, wouldnt the gas be directed off towards the other (main) exit hole ?
look at the PE design..
When quizzed as to why PE exhausts fare better than SS Dave had the following to say :
"I suspect more because of the pipe size than the design of the twin dump."
sounds logical given the above..
lets look at the ScoobySport design..
Pete's theory is reflected in the above comments - how would the gases be directed towards the separate pipe ? Why not just combine them and have a decent, larger, no-cat downpipe ?
MRT have come up with their solution - retain the twin-dump design and split the gases so they are directed towards the relevant exits..
BPM have gone down the same road..
So..given the evidence, whats the conclusion ??
Well, I would say that for outright performance a separate wastegate with a non-restrictive exit would be best - J..is that what they use on WRC cars ?
The floor is now open for comments
[This message has been edited by Lee (edited 04-12-1999).]
Hows about we discuss the pros and cons of each..I doubt we'll arrive at a "this is best for sure" answer..
Background.
Have a looksie at the back of the turbo. The gases exit from 2 possible locations..the turbo-impeller blades (J - whats this really called?) and the wastegate. The wastegate is smaller so we can assume less flow is required here - certainly excess exhaust gases only exit here when full boost is achieved.
The wastegate is opened/closed by a small flap connected ultimately to the actuator/diaphragm. When fully open the flap is at quite an acute angle..approx 30-40 degrees ?
So consider what will happen to the exhaust gas exiting the wastegate. It will hit the flap and be directed off at an angle. If you look at the twin-dump design you might argue that the flap obscures the exit hole ! Also, wouldnt the gas be directed off towards the other (main) exit hole ?
look at the PE design..
When quizzed as to why PE exhausts fare better than SS Dave had the following to say :
"I suspect more because of the pipe size than the design of the twin dump."
sounds logical given the above..
lets look at the ScoobySport design..
Pete's theory is reflected in the above comments - how would the gases be directed towards the separate pipe ? Why not just combine them and have a decent, larger, no-cat downpipe ?
MRT have come up with their solution - retain the twin-dump design and split the gases so they are directed towards the relevant exits..
BPM have gone down the same road..
So..given the evidence, whats the conclusion ??
Well, I would say that for outright performance a separate wastegate with a non-restrictive exit would be best - J..is that what they use on WRC cars ?
The floor is now open for comments
[This message has been edited by Lee (edited 04-12-1999).]
04 December 1999, 06:39 PM
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Lee,
I really like the fact that you have added pictures to your comment. Makes things more clearly. However I have one question on the PE downpipe.
Does the version shown include a high flow cat??
If so, and it has the same (or better results) as the SS it's more desirable for the ones who don't want to tinker on the car everytime we have to undergo an emissiontest.
Regards,
Nico van Steen
Netherlands
I really like the fact that you have added pictures to your comment. Makes things more clearly. However I have one question on the PE downpipe.
Does the version shown include a high flow cat??
If so, and it has the same (or better results) as the SS it's more desirable for the ones who don't want to tinker on the car everytime we have to undergo an emissiontest.
Regards,
Nico van Steen
Netherlands
04 December 1999, 06:50 PM
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I believe the PE downpipe does NOT have a cat in it, however PE do 2 different mid-sections..one without cat..and one with a claimed super-cat that will pass an emissions test.
As regards cats (maybe should start another thread) - are they really any use to a performance car on full throttle ? I was under the impression that they were only useful under light loads when the ECU was running in closed-loop operation (ie monitoring lambda and adjusting accordingly)
As regards cats (maybe should start another thread) - are they really any use to a performance car on full throttle ? I was under the impression that they were only useful under light loads when the ECU was running in closed-loop operation (ie monitoring lambda and adjusting accordingly)
04 December 1999, 07:27 PM
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Another point worthy of consideration is the diameter. A 3" system has far superior gas flow and heat eradication and when you approach 300bhp, a smaller system strangles the turbo and you start hitting a brick wall.
The standard equipment is 2.5" which creates back pressure and this is a big no no in a turbocharged engine.
When seen on dynos it is prudent to note that the apparently massive gains of an aftermarket down pipe come from removing the biggest restriction, the cat.
So, any aftermarket downpipe, as long as it is de-catted, will provide huge gains.
Kind regards
Ben
The standard equipment is 2.5" which creates back pressure and this is a big no no in a turbocharged engine.
When seen on dynos it is prudent to note that the apparently massive gains of an aftermarket down pipe come from removing the biggest restriction, the cat.
So, any aftermarket downpipe, as long as it is de-catted, will provide huge gains.
Kind regards
Ben
Trending Topics
04 December 1999, 10:44 PM
#9
Ecu Specialist
IMHO, just my two penneth,
Whilst its fair to say that a turbo engine needs a free flowing exhaust system it also needs some back pressure, basic fan laws illustrate this, a turbo will be very "laggy" irrespective of size if no back pressure at all is present so its a matter of getting the right balance.
All the aftermarket down pipes described above ( well done Lee) have their merits so at the end of the day "you pays your money"
as they say.
IMHO the best result I've seen is Mark Aigins car which has had several different downpipes fitted ... he stuck with the Scoobysport one and having driven his car I can see why.
I understood that the dyno day of the 11th was going to "debut" several different types ... maybe thats the info we all need to decide. I also am in the market for a downpipe as my standard one is throttling my Link system. Hopefully the 11th may provide some help on making a decision.
Bob
Whilst its fair to say that a turbo engine needs a free flowing exhaust system it also needs some back pressure, basic fan laws illustrate this, a turbo will be very "laggy" irrespective of size if no back pressure at all is present so its a matter of getting the right balance.
All the aftermarket down pipes described above ( well done Lee) have their merits so at the end of the day "you pays your money"
as they say.
IMHO the best result I've seen is Mark Aigins car which has had several different downpipes fitted ... he stuck with the Scoobysport one and having driven his car I can see why.
I understood that the dyno day of the 11th was going to "debut" several different types ... maybe thats the info we all need to decide. I also am in the market for a downpipe as my standard one is throttling my Link system. Hopefully the 11th may provide some help on making a decision.
Bob
04 December 1999, 11:20 PM
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BPM has pushed for side by side dyno and we would still like to see this eventuate. We have tested against these designs above, especially the MRT in Australia and we have outperformed them. The fact of the matter is the longer you keep the wastegate gases seperate to the turbine the better the flow since the less turbulance is created.
Since Lee has offered his vehicle once before why don't we move to a dyno day which tests every exhaust and plan it early next year. This would prove to be an intersting event to say the least. To re-iterate our design works since we do not use a "seperator". Prodrive doesnt , they use a separate pipe and the size of the wastegate dedicated pipe is "huge". Why change a winning formula?
If you have any further queries , please do not hesitate to email me or we can chat online with
ICQ (45940764)
Greg Nikolettos
BPM Marketing Division
Phone: (617) 3272 8885
Mobile: 0410 678 989
Fax: (617) 3218 8880
bpm@bpmsports.com
Since Lee has offered his vehicle once before why don't we move to a dyno day which tests every exhaust and plan it early next year. This would prove to be an intersting event to say the least. To re-iterate our design works since we do not use a "seperator". Prodrive doesnt , they use a separate pipe and the size of the wastegate dedicated pipe is "huge". Why change a winning formula?
If you have any further queries , please do not hesitate to email me or we can chat online with
ICQ (45940764)
Greg Nikolettos
BPM Marketing Division
Phone: (617) 3272 8885
Mobile: 0410 678 989
Fax: (617) 3218 8880
bpm@bpmsports.com
05 December 1999, 09:08 AM
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For those '99 owners like me..something I should have mentioned...
I have heard time and time again that a performance exhaust will provide much better increases on cars with huge turbos, modified cars, STi's etc
I don't really think you can expect massive gains on a stock 99 car since it has the smallest turbo going and fairly tame cams.
The replacement system should be considered as part of an overall package.
This is what Bob has just confirmed..having used the Link to tune the car the exhaust is now the bottleneck.
I have heard time and time again that a performance exhaust will provide much better increases on cars with huge turbos, modified cars, STi's etc
I don't really think you can expect massive gains on a stock 99 car since it has the smallest turbo going and fairly tame cams.
The replacement system should be considered as part of an overall package.
This is what Bob has just confirmed..having used the Link to tune the car the exhaust is now the bottleneck.
05 December 1999, 08:10 PM
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A few questions from someone who knows just a little about these things, folks.
1) Am I right saying that we should be making a distinction between 2 separate issues here - one being that the elimination of the cat in the downpipe is an improvement anyway - and the other being the approach to the turbo end, etc. of the downpipe itself?
2) What about thermal issues here? I very much like the HPC coating BPM products have as I would not like to have temperatures considerably higher around the turbo and engine bay without all the shielding the standard downpipe has? My apologies, but I drive my car every day and not on track days, so I have to be a little more practical here.
3) What about the position of the Lambda sensor fitting? I see from the pictures Lee posted (good one!) that the debate continues - some have it close to the turbo, some at a similar or same distance as the standard one.
4) As an extremely happy user of the PossumLink on my Sti5 I wonder whether I even need to change the downpipe in order to gain some degree of the ADDITIONAL improvement as the engine already breathes beautifully and on the lightest touch on the throttle starts gathering boost and momentum even below 2500rpm. Should I stay legal and leave things that work or want more, retune the whole thing, have more noise (by the way can someone tell me how MUCH MORE noise? I heard PC's car and it seemed quiet) and a little bit more??
Hope my thoughts will help this discussion, possibly from all those who already have de-cat non standard items. Offline communication also welcome.
Many thanks.
q.
[This message has been edited by quattro (edited 05-12-1999).]
1) Am I right saying that we should be making a distinction between 2 separate issues here - one being that the elimination of the cat in the downpipe is an improvement anyway - and the other being the approach to the turbo end, etc. of the downpipe itself?
2) What about thermal issues here? I very much like the HPC coating BPM products have as I would not like to have temperatures considerably higher around the turbo and engine bay without all the shielding the standard downpipe has? My apologies, but I drive my car every day and not on track days, so I have to be a little more practical here.
3) What about the position of the Lambda sensor fitting? I see from the pictures Lee posted (good one!) that the debate continues - some have it close to the turbo, some at a similar or same distance as the standard one.
4) As an extremely happy user of the PossumLink on my Sti5 I wonder whether I even need to change the downpipe in order to gain some degree of the ADDITIONAL improvement as the engine already breathes beautifully and on the lightest touch on the throttle starts gathering boost and momentum even below 2500rpm. Should I stay legal and leave things that work or want more, retune the whole thing, have more noise (by the way can someone tell me how MUCH MORE noise? I heard PC's car and it seemed quiet) and a little bit more??
Hope my thoughts will help this discussion, possibly from all those who already have de-cat non standard items. Offline communication also welcome.
Many thanks.
q.
[This message has been edited by quattro (edited 05-12-1999).]
06 December 1999, 09:11 PM
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1) elimination of cats can only be a good thing performance wise ! So yes there are 2 issues..the decatting and the design of the pipe.
2) Thermal issues..I don't know what has been done in the past but I would take the opportunity (before the new pipe is on the car) to enclose it in exhaust-wrap. This keeps the heat in and may to some extent provide a small bit of deadening.
3) Lambda sensor..depending on car its fitted before or after the turbo ! Since they have a working temperature range you need to avoid giving it an almighty roasting ! See your possum manual about relocating it and spacing it out of the airflow.
4) Since you are now producing more gases from the engine a downpipe will be of more benefit. There is a possibility that you would lose some low-down torque but the increases are there to be had. Removal of all cats means you can run your Link in open-loop mode all the time which may offer advantages..speak to Bob!
I have driven PC's car and I must say, that for a car with a 100% performance system the sound is not intrusive, but simply GORGEOUS !
Since PE do a mid-section super-cat that supposedly passes emissions you could try that..failing that its a swap come MOT time..
2) Thermal issues..I don't know what has been done in the past but I would take the opportunity (before the new pipe is on the car) to enclose it in exhaust-wrap. This keeps the heat in and may to some extent provide a small bit of deadening.
3) Lambda sensor..depending on car its fitted before or after the turbo ! Since they have a working temperature range you need to avoid giving it an almighty roasting ! See your possum manual about relocating it and spacing it out of the airflow.
4) Since you are now producing more gases from the engine a downpipe will be of more benefit. There is a possibility that you would lose some low-down torque but the increases are there to be had. Removal of all cats means you can run your Link in open-loop mode all the time which may offer advantages..speak to Bob!
I have driven PC's car and I must say, that for a car with a 100% performance system the sound is not intrusive, but simply GORGEOUS !
Since PE do a mid-section super-cat that supposedly passes emissions you could try that..failing that its a swap come MOT time..
06 December 1999, 11:01 PM
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Thanks for your 'answers', Lee. I am sorry you really believed I did not now that much about downpipes, but this is what happens when I (for once) try to be less serious!
You are pretty much spot on with most of what you have said. While I would not wrap up anything (this attracts all dirt, residue and other unwanted objects like a magnet when hot) I would have HPC coating applied which even can be done through some companies in the UK. Also, I know very well where the lambda sensor is on the standard, SS and PE downpipes and it I feel it should be away from the turbo rather than closer to it. Looking at the Australian ones I either do not see where it is supposed to be, or it looks pretty close to the turbo.
I most certainly do not want to lose torque at any expense and (for me) there are no advantages to gain if torque at low/mid band is lost even a little bit. That is for others who like to dance around the red line.
Well, we shall see when more Possums are in use on Phase II engines. The rumour has it that we will suddenly witness a rapid increase of 'ingenious mappers' and maybe Ladbrokes should become interested in thinking about some odds??
Lee, thanks again for your kind assistance. The more I look into this the more I feel I have already achieved at least as much with the standard downpipe (thanks to Possum) as others have with those 'special' ones. I am sure this will change as more experience becomes available and the usually certain benefits of a good downpipe will be more than evident.
Good luck in your quest around the Possum.
q.
[This message has been edited by quattro (edited 06-12-1999).]
You are pretty much spot on with most of what you have said. While I would not wrap up anything (this attracts all dirt, residue and other unwanted objects like a magnet when hot) I would have HPC coating applied which even can be done through some companies in the UK. Also, I know very well where the lambda sensor is on the standard, SS and PE downpipes and it I feel it should be away from the turbo rather than closer to it. Looking at the Australian ones I either do not see where it is supposed to be, or it looks pretty close to the turbo.
I most certainly do not want to lose torque at any expense and (for me) there are no advantages to gain if torque at low/mid band is lost even a little bit. That is for others who like to dance around the red line.
Well, we shall see when more Possums are in use on Phase II engines. The rumour has it that we will suddenly witness a rapid increase of 'ingenious mappers' and maybe Ladbrokes should become interested in thinking about some odds??
Lee, thanks again for your kind assistance. The more I look into this the more I feel I have already achieved at least as much with the standard downpipe (thanks to Possum) as others have with those 'special' ones. I am sure this will change as more experience becomes available and the usually certain benefits of a good downpipe will be more than evident.
Good luck in your quest around the Possum.
q.
[This message has been edited by quattro (edited 06-12-1999).]
07 December 1999, 07:45 PM
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Front pipe ... all started from the turbine housing..... is it????
The subaru turbo is running wit integral wastegate which dump exhaust gases behind the exducer and create high turbulance. When this happen ... the exducer is not having a good time to spool at its full potential.
This is aim mainly for the IHI turbocharger. Well... whomever is using TD05H ... U will not have this problem cos the Mitsubishi TC ... has its own splitter between the exducer and the wastegate.
So.... by having an extra pipe for the wastegate is better then having all in one type of system..... from the lovely pix... I think BPM, MRT and PE design r better.
My choice would be POSSUM downpipe .... sorry I dont have the pix.
As for the extra pipe... BPM system ... it might perform very well if the lenght and size of the pipe is correct.
Another option.... for good sound ... vent the wastegate pipe to ATM. Sound great .. make the car sounded very fast.
As for the back pressure .... TC car need backpressure to be at the back(muffler)not at the manifold or frontpipe..... my opinion.
Something to think about-Wat is the correct backpressure for performance????
Cheers.
The subaru turbo is running wit integral wastegate which dump exhaust gases behind the exducer and create high turbulance. When this happen ... the exducer is not having a good time to spool at its full potential.
This is aim mainly for the IHI turbocharger. Well... whomever is using TD05H ... U will not have this problem cos the Mitsubishi TC ... has its own splitter between the exducer and the wastegate.
So.... by having an extra pipe for the wastegate is better then having all in one type of system..... from the lovely pix... I think BPM, MRT and PE design r better.
My choice would be POSSUM downpipe .... sorry I dont have the pix.
As for the extra pipe... BPM system ... it might perform very well if the lenght and size of the pipe is correct.
Another option.... for good sound ... vent the wastegate pipe to ATM. Sound great .. make the car sounded very fast.
As for the back pressure .... TC car need backpressure to be at the back(muffler)not at the manifold or frontpipe..... my opinion.
Something to think about-Wat is the correct backpressure for performance????
Cheers.
07 December 1999, 10:45 PM
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Oh..Oh.... I know this one.... oh..
you need 24.673bar for the best back pressure...
venting to ATM is best.. but bloody load..illegal... and a bit warm on the old feet...suppose its ok for winter though... lol
J.
you need 24.673bar for the best back pressure...
venting to ATM is best.. but bloody load..illegal... and a bit warm on the old feet...suppose its ok for winter though... lol
J.
08 December 1999, 08:56 AM
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Eitan,
Why not just get rid from the CATs?
It's not the best way but it's VERY cheap (about 350NIS), does NOT void your warranty (at least here in Israel) and make your car fly (and sound) like a bee.
You are welcome to check my car,
Eran Dukas.
Why not just get rid from the CATs?
It's not the best way but it's VERY cheap (about 350NIS), does NOT void your warranty (at least here in Israel) and make your car fly (and sound) like a bee.
You are welcome to check my car,
Eran Dukas.
08 December 1999, 04:35 PM
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hey
i got some pics from bpm
that down pipe is one beautiful piece of work
might be worth the extra cash.
bpm says its going to be ready for shipping next week . i will give it a try.
i got some pics from bpm
that down pipe is one beautiful piece of work
might be worth the extra cash.
bpm says its going to be ready for shipping next week . i will give it a try.
08 December 1999, 07:53 PM
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Hello Chaps
Here's the crack on back pressures. To back up what we are saying here we will in the near future be measuring the pressures to actually quantify them but these are the facts anyway and we are talking de-catted here.
From the engine to the turbo the turbo creates an awful lot of back pressure. The exact amount we will measure but expect it to be between 20 & 30psi.
This is because the turbo is a massive restriction. After the turbo you DO NOT WANT ANY BACK PRESSURE WHATSOEVER.
The reason for this is you have to shift the exhaust gas and heat as fast as possible. The ideal solution would be a fat pipe going out the side of the car. This however is impractical for obvious reasons of packaging, noise etc.
Not only that but since you have no backpressure the turbo will be smoking and dumping a little oil out the back.
So, we have aftermarket exhausts that deliver back pressure due to the nature of their natural restriction.
We will measure the differences in back pressure between a 2.5" system and a 3" system and we might find one is 5psi and the other 2.5psi. We won't know the true figures until we have tested and the differences only really start to matter as you approach 300bhp.
So, whomever believes or promotes the idea of backpressures being desirable from the turbo out are completely misunderstanding the point and are wrong.
Where there is the pressure build up in front of the turbo why try and make it difficult for the gasses to get out?
Remember, this is not a normally aspirated car where you need back pressure. Every time people have bench tested exhaust systems and introduced back pressures the motors HAVE LOST POWER.
Some people might now say, "Well I want driveability not power" Well lets put a big restriction in then that stops the one thing that creates the power and torque from doing its job properly? Please!
Back pressure stops the turbo working at its best and the turbo gives you the torque and power you are after.
A turbo that spins up more slowly due to back pressures is therefore by definition more laggy.
Hope I have enlightened and helped.
Kind regards
Ben
[This message has been edited by Scooby Mania (edited 08-12-1999).]
Here's the crack on back pressures. To back up what we are saying here we will in the near future be measuring the pressures to actually quantify them but these are the facts anyway and we are talking de-catted here.
From the engine to the turbo the turbo creates an awful lot of back pressure. The exact amount we will measure but expect it to be between 20 & 30psi.
This is because the turbo is a massive restriction. After the turbo you DO NOT WANT ANY BACK PRESSURE WHATSOEVER.
The reason for this is you have to shift the exhaust gas and heat as fast as possible. The ideal solution would be a fat pipe going out the side of the car. This however is impractical for obvious reasons of packaging, noise etc.
Not only that but since you have no backpressure the turbo will be smoking and dumping a little oil out the back.
So, we have aftermarket exhausts that deliver back pressure due to the nature of their natural restriction.
We will measure the differences in back pressure between a 2.5" system and a 3" system and we might find one is 5psi and the other 2.5psi. We won't know the true figures until we have tested and the differences only really start to matter as you approach 300bhp.
So, whomever believes or promotes the idea of backpressures being desirable from the turbo out are completely misunderstanding the point and are wrong.
Where there is the pressure build up in front of the turbo why try and make it difficult for the gasses to get out?
Remember, this is not a normally aspirated car where you need back pressure. Every time people have bench tested exhaust systems and introduced back pressures the motors HAVE LOST POWER.
Some people might now say, "Well I want driveability not power" Well lets put a big restriction in then that stops the one thing that creates the power and torque from doing its job properly? Please!
Back pressure stops the turbo working at its best and the turbo gives you the torque and power you are after.
A turbo that spins up more slowly due to back pressures is therefore by definition more laggy.
Hope I have enlightened and helped.
Kind regards
Ben
[This message has been edited by Scooby Mania (edited 08-12-1999).]
08 December 1999, 09:47 PM
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Ben'scoobymania' - Thanx for the info.... Back pressure in tc car exhaust system is BAD!!!!!!!... learn something new today.
As for the exhaust manifold ... internal streamlining and flow velocity is very important..... need a smooth constant velocity for the exhaust gas to travel.
I agree .... any objection on this matter??
Would be interesting to know the back pressure and sound level figure though .... on all the 'good exhaust system' in the market.... for road car of course .... road legal too. Is good for the end user.
Anyone running wit Anti-reversion system on their exhaust system???
Cheers.
Firefox - As for the back pressure figure ... could <2psi at the tail pipe be the answer???? ...... wit cat on.
[This message has been edited by DYNT (edited 08-12-1999).]
As for the exhaust manifold ... internal streamlining and flow velocity is very important..... need a smooth constant velocity for the exhaust gas to travel.
I agree .... any objection on this matter??
Would be interesting to know the back pressure and sound level figure though .... on all the 'good exhaust system' in the market.... for road car of course .... road legal too. Is good for the end user.
Anyone running wit Anti-reversion system on their exhaust system???
Cheers.
Firefox - As for the back pressure figure ... could <2psi at the tail pipe be the answer???? ...... wit cat on.
[This message has been edited by DYNT (edited 08-12-1999).]
08 December 1999, 11:10 PM
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Hey Bro..
Anti-reversion on the headers you mean ? In relation to the pulses ?
Not me dude... lol
Have the standard headers got a cunning design secret ?
2psi ? stuff that.. I want BAR...2+ bar will do me... ie...stuff a banana up the tube.. lol
J.
Anti-reversion on the headers you mean ? In relation to the pulses ?
Not me dude... lol
Have the standard headers got a cunning design secret ?
2psi ? stuff that.. I want BAR...2+ bar will do me... ie...stuff a banana up the tube.. lol
J.
09 December 1999, 11:12 AM
#22
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I thought it had been decided that 'anti reversion' was at best theoretical and then arguably so at that?
I doubt anybody in the UK has used it, it would be interesting to see the results if they have.
I think J. has tried using his Turbo impellor blades as anti-reversion inserts in his headers.
(Sorry J. couldn't resist it).
Mike.
[This message has been edited by Mike Tuckwood (edited 09-12-1999).]
I doubt anybody in the UK has used it, it would be interesting to see the results if they have.
I think J. has tried using his Turbo impellor blades as anti-reversion inserts in his headers.
(Sorry J. couldn't resist it). Mike.
[This message has been edited by Mike Tuckwood (edited 09-12-1999).]
10 December 1999, 07:06 PM
#23
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Ben
Your comment on diameter after the turbo is correct... only if you are tuning a car for rolling road numbers.
Different diameters have a dramatic effect on pulse/wave scavenging and will greatly influence peak torque (how much and where).
If you can tune the sweet spot from scavenging to the point where the turbo is starting to spool up, you get better much better engine efficiency and hence better throttle response and higher boost at low rev's.
Most WRC teams use smaller sections after the turbo for tarmac events (good low down torque required) and larger bores for gravel (less requirement to squirt out of corners, but high rolling resistance to overcome).
What matters is driveability.
We have had STi's in at work, with 4" exhausts. They are not a patch on a standard UK car, until you are at the very top of the rev range.
A car with good mid range response will always be quicker across country than one with mad top end power but poor engine efficiency from 2000 to 5000 rpm.
Your comment on diameter after the turbo is correct... only if you are tuning a car for rolling road numbers.
Different diameters have a dramatic effect on pulse/wave scavenging and will greatly influence peak torque (how much and where).
If you can tune the sweet spot from scavenging to the point where the turbo is starting to spool up, you get better much better engine efficiency and hence better throttle response and higher boost at low rev's.
Most WRC teams use smaller sections after the turbo for tarmac events (good low down torque required) and larger bores for gravel (less requirement to squirt out of corners, but high rolling resistance to overcome).
What matters is driveability.
We have had STi's in at work, with 4" exhausts. They are not a patch on a standard UK car, until you are at the very top of the rev range.
A car with good mid range response will always be quicker across country than one with mad top end power but poor engine efficiency from 2000 to 5000 rpm.
10 December 1999, 08:07 PM
#24
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Hi Pete
Now how did I know you were going to say that!!
Looks like we completely disagree then! A couple of points though. There are many reasons why a WRC car in tarmac spec uses different specs, not least a matter of packaging.
In a tarmac car ground clearance is critical and so very often the teams will put on a different "shape" pipe that enables the car to sit lower and negotiate any jumps or obstacles. In the Escort Cosworths the pipes were oval for that very reason.
A 4" downpipe?!! WooHoo! I would have loved to have seen that. Did it fit ok?
Kind regards
Ben
p.s. Not really interested in rolling roads but they are a fun day out!
[This message has been edited by Scooby Mania (edited 10-12-1999).]
Now how did I know you were going to say that!!
Looks like we completely disagree then! A couple of points though. There are many reasons why a WRC car in tarmac spec uses different specs, not least a matter of packaging.
In a tarmac car ground clearance is critical and so very often the teams will put on a different "shape" pipe that enables the car to sit lower and negotiate any jumps or obstacles. In the Escort Cosworths the pipes were oval for that very reason.
A 4" downpipe?!! WooHoo! I would have loved to have seen that.
Did it fit ok?Kind regards
Ben
p.s. Not really interested in rolling roads but they are a fun day out!
[This message has been edited by Scooby Mania (edited 10-12-1999).]
10 December 1999, 11:54 PM
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I love this discussion. The fact it is mostly academic (meaning: pointless and without any practical or other use) and it's only aim is for the 'winner to take it all", it as absolutely amazing how some people learn everything about physics, thermodynamics, mechanical engineering, not to mention psychology, manipulation and cheap thrills overnight or quieker. But what do I know, this must be the way the rest of us who do not pretend to have collected all the 'accolades' feel and have to moan about.
I wish, dear boys, if this was all as simple as some of you are trying to make it look and sound (after all this IS a downpipe?). However, as PC said (and I am, regretfully so, not either his PR or bodyguard as yet) and I said somewhere else before, some of us drive out on the roads and some need rolling road certificates to look into. Which, of course, has nothing to do with the fact that unless the car, it's engine and lots of other things (including the operator) are healthy and working properly, you can have a triple dump downpipe and whatever else you want, and it will still be no good.
The only problem is there would nothing to 'talk' about then, would it?
Love you all and have a great weekend.
q.
[This message has been edited by quattro (edited 10-12-1999).]
I wish, dear boys, if this was all as simple as some of you are trying to make it look and sound (after all this IS a downpipe?). However, as PC said (and I am, regretfully so, not either his PR or bodyguard as yet) and I said somewhere else before, some of us drive out on the roads and some need rolling road certificates to look into. Which, of course, has nothing to do with the fact that unless the car, it's engine and lots of other things (including the operator) are healthy and working properly, you can have a triple dump downpipe and whatever else you want, and it will still be no good.
The only problem is there would nothing to 'talk' about then, would it?
Love you all and have a great weekend.
q.
[This message has been edited by quattro (edited 10-12-1999).]
11 December 1999, 12:56 PM
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Eitan
You might have got bored with the how technical this got or was it just me. Basically you are getting rid of a cat which is good. Then you have to decide which down pipe to buy. I just got one today from Scoobysport and am very happy with it. The was big improvement that I have noticed while driving it home. I was hoping for traffic just so I could get on the trottle again.
Go get one.
Chewy
You might have got bored with the how technical this got or was it just me. Basically you are getting rid of a cat which is good. Then you have to decide which down pipe to buy. I just got one today from Scoobysport and am very happy with it. The was big improvement that I have noticed while driving it home. I was hoping for traffic just so I could get on the trottle again.
Go get one.
Chewy
11 December 1999, 05:59 PM
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I've just had a Scoobysport style Downpipe fitted to my MY93 WRX today, and I can highly recommend it.
The car picks up quicker, and sounds excellent. In adittion, when changing up from 2nd, the car cracks and lobs a small flame out...no bad thing in my opinion!!
Anyway, hope this helps anyone making a decision at present.
Richie.
ICQ 51592233
The car picks up quicker, and sounds excellent. In adittion, when changing up from 2nd, the car cracks and lobs a small flame out...no bad thing in my opinion!!
Anyway, hope this helps anyone making a decision at present.
Richie.
ICQ 51592233
12 December 1999, 01:41 PM
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For info, i have had a scoobysport downpipe fitted to my UKMY99 with the Prodrive Pack.
I was at PE yesterday, and i was VERY suprised to see that i had LESS power and torque than before the downpipe.
I cant understand this as the car is much quicker/stronger/more responsive all of the time. I guess this just goes to show you how different days affect numbers, or maybe Merv needs to dyno it!
Dont conufse my statement, what I AM saying that my car now has so much grunt and go, i cannot believe it!.....there is no way in hell that i have less than before..the effect on driveability is staggering....Thnaks PC!
Whatever the debate - single/twin/seperator or not....i am over the moon with my SS pipe.
Regards
PS...Lee....wanna race?
[This message has been edited by sunilp (edited 12-12-1999).]
I was at PE yesterday, and i was VERY suprised to see that i had LESS power and torque than before the downpipe.
I cant understand this as the car is much quicker/stronger/more responsive all of the time. I guess this just goes to show you how different days affect numbers, or maybe Merv needs to dyno it!
Dont conufse my statement, what I AM saying that my car now has so much grunt and go, i cannot believe it!.....there is no way in hell that i have less than before..the effect on driveability is staggering....Thnaks PC!
Whatever the debate - single/twin/seperator or not....i am over the moon with my SS pipe.
Regards
PS...Lee....wanna race?
[This message has been edited by sunilp (edited 12-12-1999).]
13 December 1999, 02:21 PM
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Hi Guys!
One important thing to bear in mind with regards to comparing power/torque figures before / after mods is that the government moved the super-unleaded goalposts recently, so the quality of fuel has dropped significantly over the previous 98 ros stuff. If you ran your car on 98 before, and have 97 and new mods now, the figure may well be handicapped by the drop in octane level as well as the atmosheric conditions!
Moray
One important thing to bear in mind with regards to comparing power/torque figures before / after mods is that the government moved the super-unleaded goalposts recently, so the quality of fuel has dropped significantly over the previous 98 ros stuff. If you ran your car on 98 before, and have 97 and new mods now, the figure may well be handicapped by the drop in octane level as well as the atmosheric conditions!
Moray