front mounted i/c or exhaust manifold?
14 July 2001, 03:32 AM
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I own a 99 scooby WRX. I have done the usual breathing mods and added an electronic boost controller and an oil cooler. Next I am thinking of either installing a front mounted intercooler or an equal length exhaust manifold.Which one do you guys think is more appropriate? Any views welcome.
Cheers
Piravlos
Cheers
Piravlos
16 July 2001, 04:49 AM
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I don't mind about losing the burbling sound. With the manifold on, the car will sound like a GSXR. I also intend to up the boost up to 1.2 bar. My question is whether with an exhaust manifold my car will be more powerful and responsive than with a fmic at 1.2 bar.
16 July 2001, 08:59 AM
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Personally, I don't agree with the comments Theo has copied from the other thread, re- headers. That person is no longer with the company he was representing, and I have no idea what he was basing his info on.
There are various different designs of headers, each giving different results, depending on what the manufacturer was aiming to achieve. Some headers are designed to give MAX power, others are designed to increase low to mid' range.
It's pointless going for the "max power" design, unless the turbo is able to flow sufficient air at high rev's. The TD04 (UK cars) is already struggling at 5500rpm.
It would also be worth looking at "unequal length" headers. Tests have shown these to give very good gains, and retain some of the "boxer " sound.
Before I went and spent circa £1200 on headers, I'd recommend people port their standard headers. You'll be surprised at the results......
FMIC: Again, the TD04 struggles with a FMIC. I found it very laggy, especially through the gears. A larger turbo would solve most of this.
IMHO, I'd port the headers, and get a bigger turbo. I'd recommend a Turbo Dynamics VF series hybrid.
A bigger turbo, will give a big improvement to power, reduce the intake temps, and flow enough air to hold boost to the red line.
Then if you go for a FMIC, you'll be able to get the best from it.
Mark.
There are various different designs of headers, each giving different results, depending on what the manufacturer was aiming to achieve. Some headers are designed to give MAX power, others are designed to increase low to mid' range.
It's pointless going for the "max power" design, unless the turbo is able to flow sufficient air at high rev's. The TD04 (UK cars) is already struggling at 5500rpm.
It would also be worth looking at "unequal length" headers. Tests have shown these to give very good gains, and retain some of the "boxer " sound.
Before I went and spent circa £1200 on headers, I'd recommend people port their standard headers. You'll be surprised at the results......
FMIC: Again, the TD04 struggles with a FMIC. I found it very laggy, especially through the gears. A larger turbo would solve most of this.
IMHO, I'd port the headers, and get a bigger turbo. I'd recommend a Turbo Dynamics VF series hybrid.
A bigger turbo, will give a big improvement to power, reduce the intake temps, and flow enough air to hold boost to the red line.
Then if you go for a FMIC, you'll be able to get the best from it.
Mark.
16 July 2001, 09:06 AM
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I have the Powerengineering exhaust manifold (equal lenght), and I have between 1.2 and 1.3 bar without changing the ECU. Results are very good, but you don't have an increase of 25 bhp. The increase of bhp lays in the fact that you have more bhp in lower revs! Results: (before/after)
16 July 2001, 12:11 PM
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DID YOU LOSE ALSO YOUR ENGINE?
"You can't get 25bhp without increasing boost.
A power manifold may lower backpressure in front of the turbo and therefore you will get some gains but not 25bhp.
Are you sure about the figure? We sell front headers as well and I would advise against such a conversion unless you are running serious power that has involved some engine building.
Kind regards
Ben"
Edited by Scooby Mania:
"You can't get 25bhp without increasing boost.
A power manifold may lower backpressure in front of the turbo and therefore you will get some gains but not 25bhp.
Are you sure about the figure? We sell front headers as well and I would advise against such a conversion unless you are running serious power that has involved some engine building.
Kind regards
Ben"
Edited by Scooby Mania:
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16 July 2001, 03:16 PM
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You live in Cypros koubare? So IMHO your first priority is cooling. This will also be useful for 60% of cypriot weather same as here if not warmer. Oil cooler = good move can u tell me the type as I wanna fit one, cheers
Stelios
Stelios
16 July 2001, 04:15 PM
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piravlos,
I would strongly recommand the change of exhaust manifol. It is problably the most important mod since you already had the rest of breathing sections done. As R19KET mentioned, there are 2 types of exhaust manifol. 4 into 1 which are good for high rev, high speed use like at track. Where the other type is 4 into 2 into 1 which provides very good low to mid range response and i would strongly suggest this type to you. Assuming you have not touch you ecu yet, if no intension to do so just yet, i would recommand you to install a fuel pressure regulator and increase a bit of pressure than standard to give you an extra 5 to 10% fuelling, more safty.
If you were to do any further mod in future. If budget allows you to do so, i would than suggest you to change to a bigger turbo + FMIC + ecu remap (a must at this stage) at the same time. If..... budget is a problem or want to experience the difference item by item so.... If no intention for huge turbo, than change turbo first (of course remapping your ecu at the same time). If.... want a huge turbo end of the day, then might as well get the fmic first.
p/s: For big turbo, make sure your air-flow sensor can handle that much air.
Hyper
[This message has been edited by Hyperex (edited 16 July 2001).]
I would strongly recommand the change of exhaust manifol. It is problably the most important mod since you already had the rest of breathing sections done. As R19KET mentioned, there are 2 types of exhaust manifol. 4 into 1 which are good for high rev, high speed use like at track. Where the other type is 4 into 2 into 1 which provides very good low to mid range response and i would strongly suggest this type to you. Assuming you have not touch you ecu yet, if no intension to do so just yet, i would recommand you to install a fuel pressure regulator and increase a bit of pressure than standard to give you an extra 5 to 10% fuelling, more safty.
If you were to do any further mod in future. If budget allows you to do so, i would than suggest you to change to a bigger turbo + FMIC + ecu remap (a must at this stage) at the same time. If..... budget is a problem or want to experience the difference item by item so.... If no intention for huge turbo, than change turbo first (of course remapping your ecu at the same time). If.... want a huge turbo end of the day, then might as well get the fmic first.
p/s: For big turbo, make sure your air-flow sensor can handle that much air.
Hyper
[This message has been edited by Hyperex (edited 16 July 2001).]
16 July 2001, 09:00 PM
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R19KET
"It would also be worth looking at "unequal length" headers. Tests have shown these to give very good gains, and retain some of the "boxer " sound."
Do you have test result from exhausts manifolds? If yes please post it here, I am interesting for these changes to my car, but there is nobody with such experiences to help me!
Turboke
"I have the Powerengineering exhaust manifold (equal length), and I have between 1.2 and 1.3 bar without changing the ECU. Results are very good, but you don't have an increase of 25 bhp"
You mean that the exhaust manifold increases the boost pressure? If yes what pressure must expect from my car with the PPP fitted?
There is any problem at all?
Thanks in advice, Jim.
[This message has been edited by JIM THEO (edited 16 July 2001).]
"It would also be worth looking at "unequal length" headers. Tests have shown these to give very good gains, and retain some of the "boxer " sound."
Do you have test result from exhausts manifolds? If yes please post it here, I am interesting for these changes to my car, but there is nobody with such experiences to help me!
Turboke
"I have the Powerengineering exhaust manifold (equal length), and I have between 1.2 and 1.3 bar without changing the ECU. Results are very good, but you don't have an increase of 25 bhp"
You mean that the exhaust manifold increases the boost pressure? If yes what pressure must expect from my car with the PPP fitted?
There is any problem at all?
Thanks in advice, Jim.
[This message has been edited by JIM THEO (edited 16 July 2001).]
17 July 2001, 02:42 AM
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Hi Piravlos!
You have identified two products which have the potential to increase the power output of your engine considerably, but by somwehat different means...
An exhaust manifold may improve the natural volumetric efficiency of the engine; in other words more fuelmix gets drawn into the cylinders as a result of less "left over" gas, because there is less back pressure. There are more designs than you can shake a stick at, and each "works best" in a certain area of the rev band, but make no mistake, it would be VERY unusual to see an improvement in VE across the board, you'll lose out somewhere, but that may be insignificant compared to the gains you get in the improved areas....
It is important to make a disticntion between various types of manifold....
The OEM part is a weird hybrid... you have 2 into 1 from the right feeding a 3 into 1 collector on the left... it's certainly unequal length, and it's "technically" a 4 into 2 into 1.
Most after market manifolds are 4 into 2 into 1 manifolds.... That is to say that there are two pipes from the right hand side of the engine which join into 1 at the left; similarly there are a 2 from the left that join into 1. The resulting 2 pipes join at some point, either at the bottom of the engine, at the turbo, or somewhere inbetween.
Although many manifolds claim to be equal length, most are NOT, since there isn't the room in the Scooby to coil the pipes from the left hand side round... the term "equal length" means that the length of pipework from each of the exhaust ports to the turbo (or the point where the manifold joins to just one pipe) is equal. There are also some 4 into 2 into 1 designs which are (purposely) unequal in length, typically these have shorter pipes from the left hand side (saves coiling them up!).
There are also some interesting "hybrid" designs where the 2 pipes from the right side merge half way across the engine, this is preferable to the Subaru collectors but not quite as optimal as joining on the right.
I have never seen a 4 into 1 manifold for the EJ20 engine which works with the turbo in its normal location, although JUN have got a 4 into 1 manifold on their trick 2.6 litre 530 BHP monster
For the most part, 4 into 1 isn't worth the agro.
So what are the advantages?
Equal length (or as close as you can get to it) will trash the boxer sound, but with create a nice VE plateau around its designed rev range.
Unequal length will retain (to some extent) the boxer sound. Because it has unequal length primaries, each will have a different optimal rev range; the result is slightly lower VE, but over a wider range, this will be excellent for road use and make a very driveable car. Equal length although devastatingly effective are a bit peaky.
4 into 1 (if you're mad enough) further increases the pulse tuning by completely removing the secondaries and any smoothing that they may have brought about. This is a pure race manifold, VERY peaky, but you simply cannot improve VE any more... it is entirely possible to get get VE BEYOND 100% with such a design... coupled with a turbocharger this combination would be almost undriveable on the road, IMVHO, but in a narrow peaky power band on track, it would be a sure winner (given sufficient driver skill to exploit it).
As a cheap alternative, it is possible to port the Subaru headers a little... as one of (if not the first) nutter in the UK to try this, I can report that it DOES make a difference, the VE characteristics DO change, and I needed to add fuel to my PossumLink map as a result. As a side effect, the engine actually ran *quieter* rather odd but true.
Another interesting point to note is that EGT drops markedly with a decent manifold (guess that cooling is better, or the gas just "lingers" in the manifold for less time?). I recorded up to 150 degrees C less at the entry to my turbo when I fitted an equal (almost, anyway) length manifold. This opens to possibility for pushing the limits where before you were about to fry the turbo
As for intercoolers, you are improving VE "by other means", rather than having the engine "naturally" draw in more fuelmix, you are making the same charge more dense, so for the same volume you are getting more air and fuel, so more power. Keeping things cool is never a bad thing (well, within reason).
But all of these things will be pretty much in vain if your turbo isn't up to the job of flowing enough air. If by WRX you mean it's Japanese car, then it will have a VF28 turbo, which should be OK for 340BHP before you need to look at a bigger unit. If you mean WRX as in the Australian WRX (which is like the UK Turbo 2000) then you will have an MHI TD-04L turbo, which is minute.... it is by far the greatest restriction in the exhasut system (so a manifold that flows better will just get "choked" by it) and the impeller will be WAY out of it's optimum operating regime... expect it to a) impede flow out of the engine and b) generate lots of heat in the intake which you need to get rid of. It's not up to serious power applications.
It's also worth mentioning that with intercoolers you are chasing a target you will never achieve, you will only approach it asymptotically.... basically you'de like the IC to be 100% efficient. The only intercoolers that achieve 100% or more efficiency are either one-shot (ice of CO2 cooled) or marine intercoolers (which can cool air down below ambient if the water they are in is below ambient).
With normal air-air intercooler, every small increase in efficiency comes at a huge price (in terms of core area, ambient air flow restriction to the radiator etc)... if you're getting 85% or more, you're doing well, and you'll probably get better "value for money" improving the engine's inherent breathing ability by fitting a manifold and/or high flow exhaust system. If your IC is still quite crude then you'll get better results by improving the IC.... certainly anything less than 70% efficient belongs in the garage not on the car
Hope this (rather long winded guff) help.
Cheers,
Pat. (About to fit the maddest intercooler ever )
You have identified two products which have the potential to increase the power output of your engine considerably, but by somwehat different means...
An exhaust manifold may improve the natural volumetric efficiency of the engine; in other words more fuelmix gets drawn into the cylinders as a result of less "left over" gas, because there is less back pressure. There are more designs than you can shake a stick at, and each "works best" in a certain area of the rev band, but make no mistake, it would be VERY unusual to see an improvement in VE across the board, you'll lose out somewhere, but that may be insignificant compared to the gains you get in the improved areas....
It is important to make a disticntion between various types of manifold....
The OEM part is a weird hybrid... you have 2 into 1 from the right feeding a 3 into 1 collector on the left... it's certainly unequal length, and it's "technically" a 4 into 2 into 1.
Most after market manifolds are 4 into 2 into 1 manifolds.... That is to say that there are two pipes from the right hand side of the engine which join into 1 at the left; similarly there are a 2 from the left that join into 1. The resulting 2 pipes join at some point, either at the bottom of the engine, at the turbo, or somewhere inbetween.
Although many manifolds claim to be equal length, most are NOT, since there isn't the room in the Scooby to coil the pipes from the left hand side round... the term "equal length" means that the length of pipework from each of the exhaust ports to the turbo (or the point where the manifold joins to just one pipe) is equal. There are also some 4 into 2 into 1 designs which are (purposely) unequal in length, typically these have shorter pipes from the left hand side (saves coiling them up!).
There are also some interesting "hybrid" designs where the 2 pipes from the right side merge half way across the engine, this is preferable to the Subaru collectors but not quite as optimal as joining on the right.
I have never seen a 4 into 1 manifold for the EJ20 engine which works with the turbo in its normal location, although JUN have got a 4 into 1 manifold on their trick 2.6 litre 530 BHP monster
For the most part, 4 into 1 isn't worth the agro.So what are the advantages?
Equal length (or as close as you can get to it) will trash the boxer sound, but with create a nice VE plateau around its designed rev range.
Unequal length will retain (to some extent) the boxer sound. Because it has unequal length primaries, each will have a different optimal rev range; the result is slightly lower VE, but over a wider range, this will be excellent for road use and make a very driveable car. Equal length although devastatingly effective are a bit peaky.
4 into 1 (if you're mad enough) further increases the pulse tuning by completely removing the secondaries and any smoothing that they may have brought about. This is a pure race manifold, VERY peaky, but you simply cannot improve VE any more... it is entirely possible to get get VE BEYOND 100% with such a design... coupled with a turbocharger this combination would be almost undriveable on the road, IMVHO, but in a narrow peaky power band on track, it would be a sure winner (given sufficient driver skill to exploit it).
As a cheap alternative, it is possible to port the Subaru headers a little... as one of (if not the first) nutter in the UK to try this, I can report that it DOES make a difference, the VE characteristics DO change, and I needed to add fuel to my PossumLink map as a result. As a side effect, the engine actually ran *quieter* rather odd but true.
Another interesting point to note is that EGT drops markedly with a decent manifold (guess that cooling is better, or the gas just "lingers" in the manifold for less time?). I recorded up to 150 degrees C less at the entry to my turbo when I fitted an equal (almost, anyway) length manifold. This opens to possibility for pushing the limits where before you were about to fry the turbo
As for intercoolers, you are improving VE "by other means", rather than having the engine "naturally" draw in more fuelmix, you are making the same charge more dense, so for the same volume you are getting more air and fuel, so more power. Keeping things cool is never a bad thing (well, within reason).
But all of these things will be pretty much in vain if your turbo isn't up to the job of flowing enough air. If by WRX you mean it's Japanese car, then it will have a VF28 turbo, which should be OK for 340BHP before you need to look at a bigger unit. If you mean WRX as in the Australian WRX (which is like the UK Turbo 2000) then you will have an MHI TD-04L turbo, which is minute.... it is by far the greatest restriction in the exhasut system (so a manifold that flows better will just get "choked" by it) and the impeller will be WAY out of it's optimum operating regime... expect it to a) impede flow out of the engine and b) generate lots of heat in the intake which you need to get rid of. It's not up to serious power applications.
It's also worth mentioning that with intercoolers you are chasing a target you will never achieve, you will only approach it asymptotically.... basically you'de like the IC to be 100% efficient. The only intercoolers that achieve 100% or more efficiency are either one-shot (ice of CO2 cooled) or marine intercoolers (which can cool air down below ambient if the water they are in is below ambient).
With normal air-air intercooler, every small increase in efficiency comes at a huge price (in terms of core area, ambient air flow restriction to the radiator etc)... if you're getting 85% or more, you're doing well, and you'll probably get better "value for money" improving the engine's inherent breathing ability by fitting a manifold and/or high flow exhaust system. If your IC is still quite crude then you'll get better results by improving the IC.... certainly anything less than 70% efficient belongs in the garage not on the car
Hope this (rather long winded guff) help.
Cheers,
Pat. (About to fit the maddest intercooler ever
)
17 July 2001, 03:38 AM
#12
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Thanks a lot Pat, This is more than helpful. My car is indeed a Japanese WRX with the VF 28 turbo on. The manifold I have in mind is the JUN 4-2-1 item.I have heard very good comments about it. It transforms the car at low and mid revs dramatically. I suppose I will go for the manifold and change the ic when I get the bigger turbo.
17 July 2001, 01:20 PM
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I have the Scooby Sports equal length manifold on a P1, with complete SS exhaust system, and this made a very noticeable improvement in mid range power.
The sound of the engine changes to more of an F1 car like crackle instead of the rumble of a normal Scooby - still sounds good though.
The sound of the engine changes to more of an F1 car like crackle instead of the rumble of a normal Scooby - still sounds good though.
17 July 2001, 10:05 PM
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Pat
We keep hearing about intercoolers. Any comments on Charge coolers? - would this be a better alternative?
Does anyone know anywhere in the Southwest that can port the standard headers at a reasonable price and know what they are doing - Powerstation?
Rgds
Steve
We keep hearing about intercoolers. Any comments on Charge coolers? - would this be a better alternative?
Does anyone know anywhere in the Southwest that can port the standard headers at a reasonable price and know what they are doing - Powerstation?
Rgds
Steve
17 July 2001, 11:38 PM
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I second post my question:
Does the exhaust manifold increase the boost pressure?
I have already fitted the Prodrive Performance Pack (1.2 bar).
There is no answer to my question
?
[This message has been edited by JIM THEO (edited 17 July 2001).]
Does the exhaust manifold increase the boost pressure?
I have already fitted the Prodrive Performance Pack (1.2 bar).
There is no answer to my question
?[This message has been edited by JIM THEO (edited 17 July 2001).]
18 July 2001, 12:48 AM
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Whether a chargecooler works better than a large front-mounted air/air unit has a lot to do with your driving environment - if you live in London or the South East (fairly low average speed), it will almost certainly be more efficient.
Tracks or less congested areas, the front mounted intercooler would probably be a better bet.
Apparently, in very hot ambient conditions, Prodrive have apparently recommended at least one person to use a chargecooler -
Tracks or less congested areas, the front mounted intercooler would probably be a better bet.
Apparently, in very hot ambient conditions, Prodrive have apparently recommended at least one person to use a chargecooler -
18 July 2001, 12:04 PM
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Steve,
Ah, the age old topic of charge coolers My *personal* feeling is that I do not like the idea, using two heat exchangers just "feels wrong", that's not to say that it's not possible to get good results.
Unless you spend a lot of time and energy investigating what works well, the intercooler and the charge cooler serve different purposes on the Impreza, IMVHO. A charge cooler will get the temps lower than an air-air intercooler.... for a while... this is perfect for drag racing, but for the track, the water will heat soak, unless the volume of water is quite significant, and the circulation is very good.
An air-air intercooler will cool down much more rapidly once the source of heat (ie the boost) is removed; there is significant thermal energy stored in the water of a charge cooler system, which can cause it to stay warm for longer, unless the water radiator is very good... so one has to ask the question "would an intercooler of similar dimensions work better than the water radiator?" and I think in the case of the Impreza, the answer is yes...
The charge cooler does have one HUGE advantage though. It allows the water radiator to be exposed to the air at the front of the car; water pipes are much smaller than IC pipes and therefore can fit through where otherwise plumbing for an FMIC would be troublesome.
You pays your money and takes your pick...
As for header porting, have a chat with Pete @ Scoobysport, he's done quite a few sets Other than that, I only know of J and myself who have attacked the poor little collectors with die grinders
With regard to boost pressure, fitting different headers SHOUDL NOT affect boost pressure, because boost should be a closed loop feedback function; ie the ECU will do what it has to in order to maintain it's pre-programmed boost targets. That's the theory. In practice, you are altering the VE of the engine, and thereby the boost response characteristc. The OEM boost control system was designed an open loop response which is typical of the normal headers, so it will not match the new ones. This may cause overboost, slugged boost or any number of other interesting side effects... it's not easy to predict. Fortunately you can play around with the restrictors to adjust the boost response, so don't worry too much about it... if it does tend to runa bit too high, you can always fit a different restrictor to calm it down again
Cheers,
Pat.
[Edited 'coz I forgot to answer a few questions]
[This message has been edited by pat (edited 18 July 2001).]
Ah, the age old topic of charge coolers
My *personal* feeling is that I do not like the idea, using two heat exchangers just "feels wrong", that's not to say that it's not possible to get good results.Unless you spend a lot of time and energy investigating what works well, the intercooler and the charge cooler serve different purposes on the Impreza, IMVHO. A charge cooler will get the temps lower than an air-air intercooler.... for a while... this is perfect for drag racing, but for the track, the water will heat soak, unless the volume of water is quite significant, and the circulation is very good.
An air-air intercooler will cool down much more rapidly once the source of heat (ie the boost) is removed; there is significant thermal energy stored in the water of a charge cooler system, which can cause it to stay warm for longer, unless the water radiator is very good... so one has to ask the question "would an intercooler of similar dimensions work better than the water radiator?" and I think in the case of the Impreza, the answer is yes...
The charge cooler does have one HUGE advantage though. It allows the water radiator to be exposed to the air at the front of the car; water pipes are much smaller than IC pipes and therefore can fit through where otherwise plumbing for an FMIC would be troublesome.
You pays your money and takes your pick...
As for header porting, have a chat with Pete @ Scoobysport, he's done quite a few sets
Other than that, I only know of J and myself who have attacked the poor little collectors with die grinders With regard to boost pressure, fitting different headers SHOUDL NOT affect boost pressure, because boost should be a closed loop feedback function; ie the ECU will do what it has to in order to maintain it's pre-programmed boost targets. That's the theory. In practice, you are altering the VE of the engine, and thereby the boost response characteristc. The OEM boost control system was designed an open loop response which is typical of the normal headers, so it will not match the new ones. This may cause overboost, slugged boost or any number of other interesting side effects... it's not easy to predict. Fortunately you can play around with the restrictors to adjust the boost response, so don't worry too much about it... if it does tend to runa bit too high, you can always fit a different restrictor to calm it down again
Cheers,
Pat.
[Edited 'coz I forgot to answer a few questions]
[This message has been edited by pat (edited 18 July 2001).]
18 July 2001, 07:31 PM
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i thought i would add something in regards to the standard radiator and the APS FMIC that i have. water temps on the link tunning module have not changed at all, i still get 88c in traffic and 84-86 on full blast which is exactly what i used to get before.
strange i know !!!
strange i know !!!
18 July 2001, 07:51 PM
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Sam,
How fast does the water temp sensor react? I suspect a slow acting sensor would have trouble keeping up with short bursts of heat that may occur during on boost driving... although these spikes should be dampened by the volume of liquid in the cooling system.
Moray
How fast does the water temp sensor react? I suspect a slow acting sensor would have trouble keeping up with short bursts of heat that may occur during on boost driving... although these spikes should be dampened by the volume of liquid in the cooling system.
Moray
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