Bleed valves - why oh, why oh, why?
24 February 2002, 01:28 PM
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Trout, marketing is a strong force ... and you can get them in anodized blue ! 
I don't have much left standard in my car, but I'm still using the poxy standard dumpvalve (MY99).
Would remove it but I don't think the VF23 would take that kindly ... hmmm, maybe the VF30 would ?
Theo
I don't have much left standard in my car, but I'm still using the poxy standard dumpvalve (MY99).
Would remove it but I don't think the VF23 would take that kindly ... hmmm, maybe the VF30 would ?
Theo
24 February 2002, 01:43 PM
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Theo,
well, I am merely overwhelmed by this rush to fit Bleed Valves - a rose would still be as sweet by any other name, etc. Spice it up with FCDs, mmmmmmmmmm!
Is waiting for some new posts soon - it didn't quite work as expected - oooooopps.
Trout
[Edited by Trout - 2/24/2002 1:49:41 PM]
well, I am merely overwhelmed by this rush to fit Bleed Valves - a rose would still be as sweet by any other name, etc. Spice it up with FCDs, mmmmmmmmmm!
Is waiting for some new posts soon - it didn't quite work as expected - oooooopps.
Trout
[Edited by Trout - 2/24/2002 1:49:41 PM]
24 February 2002, 03:08 PM
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Oops ... brain fart 
Ermm... don't mind my previous reply ... I read dumpvalves, doh.
Need a few days off I think. Wait, just had them
OK, the bleedvalve / FCD combo (where the FC is lifted, not removed) is a crude way of tuning, but it is certainly not stupid.
It is not something I would do, but you can get pretty good results with them. It's also a budget thing I suppose.
In a way it is all very personal. I for example don't understand why people rave about the PPP (but I wouldn't slag it, to each their own)
The real danger with bleedvalves / FCD's is not knowing where to stop, which causes holes in pistons etc.
I'm all for proper tuning, but let's not forget that the Impreza ECU (pre MY01) just easily allows for upping the power without changing much.
There is no technical proof that using bleedvalves (well, the Dawes is not entirely a bleed valve) is in any way more damaging to the cars than fitting a PPP or a Link, given that you stay within safe limits (which are different for each car etc, and talking UK cars).
That said, having the power to adjust boost maps, ignition and fuelling is worth the money.
You want controversy ? You got it
The next one on this bbs that is going to use the term "fooling the ECU" etc should have the decency to explain exactly what the MY01 PPP does.
Theo
Ermm... don't mind my previous reply ... I read dumpvalves, doh.
Need a few days off I think. Wait, just had them
OK, the bleedvalve / FCD combo (where the FC is lifted, not removed) is a crude way of tuning, but it is certainly not stupid.
It is not something I would do, but you can get pretty good results with them. It's also a budget thing I suppose.
In a way it is all very personal. I for example don't understand why people rave about the PPP (but I wouldn't slag it, to each their own)
The real danger with bleedvalves / FCD's is not knowing where to stop, which causes holes in pistons etc.
I'm all for proper tuning, but let's not forget that the Impreza ECU (pre MY01) just easily allows for upping the power without changing much.
There is no technical proof that using bleedvalves (well, the Dawes is not entirely a bleed valve) is in any way more damaging to the cars than fitting a PPP or a Link, given that you stay within safe limits (which are different for each car etc, and talking UK cars).
That said, having the power to adjust boost maps, ignition and fuelling is worth the money.
You want controversy ? You got it
The next one on this bbs that is going to use the term "fooling the ECU" etc should have the decency to explain exactly what the MY01 PPP does.Theo
24 February 2002, 03:59 PM
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MY01 PPP - can't imagine what you are alluding to
Was just creating a conversation - my thought is that if you go to an ECU change then you either try and get a specialist to sort if for you, or you understand what can be done - except in a few cases!
I was puzzled by your Dump Valve comment I have to admit!
Trout
Was just creating a conversation - my thought is that if you go to an ECU change then you either try and get a specialist to sort if for you, or you understand what can be done - except in a few cases!
I was puzzled by your Dump Valve comment I have to admit!
Trout
24 February 2002, 05:11 PM
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But the factory solenoid is a recirculating bleed valve controlled rather badly by the ECU?
I suppose they tune the boost and they do it cheaply. Up to fuel cut some ECUs seem to cope rather well. Some seem to do OK afterwards for a short way too.
[Edited by john banks - 2/24/2002 5:13:03 PM]
I suppose they tune the boost and they do it cheaply. Up to fuel cut some ECUs seem to cope rather well. Some seem to do OK afterwards for a short way too.
[Edited by john banks - 2/24/2002 5:13:03 PM]
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24 February 2002, 05:14 PM
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Badly...quite a strong word..it gets tailed off after 5-5500 rpm...but that's more of a safety feature innit?
...and the overboost peeps experience is more due to breathing mods...
/J - who also would like to remove the shiny Forge BOV he's got.
[Edited by SecretAgentMan - 2/24/2002 5:15:24 PM]
...and the overboost peeps experience is more due to breathing mods...
/J - who also would like to remove the shiny Forge BOV he's got.
[Edited by SecretAgentMan - 2/24/2002 5:15:24 PM]
24 February 2002, 05:19 PM
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Badly because it does not do a good impression of full closed loop control and does not significantly ramp up the duty cycle during spool up, as well as being pi$$ poor slow The latter being most peeps reason I guess. But to the first neither does a bleed valve. So best do it properly then
The latter being most peeps reason I guess. But to the first neither does a bleed valve. So best do it properly then
24 February 2002, 07:13 PM
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John,
so best get an ECU or EBC that allows you to tailor the boost response AND ensure you get boost control in all conditions. Whilst a mild tune with a bleed valve may seem all to the well and good on the road - what happens when the poor sucker goes on track and suddenly the car is overboosting like a Tory at a Party Conference shindig and BANG...........oops!
It has happened.
Trout
so best get an ECU or EBC that allows you to tailor the boost response AND ensure you get boost control in all conditions. Whilst a mild tune with a bleed valve may seem all to the well and good on the road - what happens when the poor sucker goes on track and suddenly the car is overboosting like a Tory at a Party Conference shindig and BANG...........oops!
It has happened.
Trout
24 February 2002, 07:38 PM
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You pays your money, you take your chances. I've got in the region of 320 bhp from my WRX for under 500 pounds. I recon I could buy myself a new engine and have change, from what some spend on a "pro" job 
24 February 2002, 07:49 PM
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Trout - that is why I am working on an EBC design that will do all the things you mention for oh, about £15 I need to get round to coding the RPM mapping, but other than that it works. Adding an RPM dependent adjustment to the MAF signal is also possibly on the cards in case I fetttle the turbo, but I'll need a DAC which will probably add another £5 Of course I don't include the FAR more expensive development time, but it is a hobby so not an issue.
With a ball-spring and a bleed hole of the correct size along with tweaks to your actuator you can get a pretty good boost curve to your liking, with good part throttle. I think there is a lot going for it, to the point that some commercial tuners use MBCs with their Unichips in the US with excellent results.
I'm uncertain why on a track you would suddenly get overboost with a manual boost controller - either bleed or ball spring? You can test it at full load on the road? Intake temps are another matter entirely.
I need to get round to coding the RPM mapping, but other than that it works. Adding an RPM dependent adjustment to the MAF signal is also possibly on the cards in case I fetttle the turbo, but I'll need a DAC which will probably add another £5 Of course I don't include the FAR more expensive development time, but it is a hobby so not an issue.With a ball-spring and a bleed hole of the correct size along with tweaks to your actuator you can get a pretty good boost curve to your liking, with good part throttle. I think there is a lot going for it, to the point that some commercial tuners use MBCs with their Unichips in the US with excellent results.
I'm uncertain why on a track you would suddenly get overboost with a manual boost controller - either bleed or ball spring? You can test it at full load on the road? Intake temps are another matter entirely.
24 February 2002, 08:05 PM
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John,
I don't personally - however I have seen it on other cars - also cars using this strategy with Unichip. It seems to be related to heat - when the car gets very hot the boost control seems to go haywire and overboost can be extreme.
Also on track you will regularly be booting the throttle at 5-6,000rpm and getting overboost in places that you simply do not reach on the road, at every corner!
As I say this is what I have observed on other cars, to the point at which one let go. Was this the primary cause - high possibility - tho not definate.
So have you tested your set up on the track as it is a very different to being tested to the limit on the road - significantly more demanding and hostile - requiring a different mapping approach and boost control. I need to change my boost parameters on track to get satisfactory control - not something you can do with a mechanical device.
Personally I went for the expensive route
Trout
[Edited by Trout - 2/24/2002 8:06:58 PM]
I don't personally - however I have seen it on other cars - also cars using this strategy with Unichip. It seems to be related to heat - when the car gets very hot the boost control seems to go haywire and overboost can be extreme.
Also on track you will regularly be booting the throttle at 5-6,000rpm and getting overboost in places that you simply do not reach on the road, at every corner!
As I say this is what I have observed on other cars, to the point at which one let go. Was this the primary cause - high possibility - tho not definate.
So have you tested your set up on the track as it is a very different to being tested to the limit on the road - significantly more demanding and hostile - requiring a different mapping approach and boost control. I need to change my boost parameters on track to get satisfactory control - not something you can do with a mechanical device.
Personally I went for the expensive route
Trout
[Edited by Trout - 2/24/2002 8:06:58 PM]
24 February 2002, 08:12 PM
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Trout
We probably all want and get the same thing in the end. We just choose different routes DIY or PRO. Both can achieve good results.
Not everyone just wants to go race, some of us (me for one) get just as much, if not more, pleasure from carrying out the work ourselves.
cc
We probably all want and get the same thing in the end. We just choose different routes DIY or PRO. Both can achieve good results.
Not everyone just wants to go race, some of us (me for one) get just as much, if not more, pleasure from carrying out the work ourselves.
cc
24 February 2002, 08:19 PM
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I've not tested it on track yet as I haven't been on track yet - but will be doing both this year I can't see a properly setup MBC or EBC car being any worse than the OEM boost controller?
Certainly my EBC code already successfully (ie it works on the road) uses four different strategies simultaneously (proportion, integral, differential and static) to get to target boost without overshoot whereas one works satisfactorily on the road (static - this is also the way the Unichip boost controller works but is RPM mapped also). So I hope it will be good.
Most aftermarket EBCs appear to use between two and four strategies, the OEM ECU seems to use two (static and integral).
Perhaps if a valve or ball-spring gets very hot it could work differently, but from most assumptions I would think it would boost lower, but it would depend on where exactly it is installed.
I can understand a car with increased boost letting go on the track because of increased temperatures, but why would it overboost? On the road I have tested by running at high revs/full load repeatedly by finding a suitable stretch of deserted road and making full use of my brakes. How is this different to the track? Any insights you have will be useful to me in my design, also what settings do you have to change?
For example, I can get no spikes by turning the proportional gain down or the differential gain up. Getting the balance right you can get no spike at all. If this changes into a 1 PSI spike on the track I can just adjust it a bit more, but use the same integral and static DCs, which are a bit below what is required to allow the system to control with PID which is most effective.
EDIT - CC you arguably get better results after seeing your 12.8 today on a 95 WRX on the std ECU, turbo and TMIC. Incredible, better than all the remapped Scoobies Not knocking remaps of course. I am not also convinced that a remap on a MY99/00 gives substantially better results than raising the fuel cut by 2 PSI and running a boost controller of your preferred type.
[Edited by john banks - 2/24/2002 8:23:14 PM]
I can't see a properly setup MBC or EBC car being any worse than the OEM boost controller?Certainly my EBC code already successfully (ie it works on the road) uses four different strategies simultaneously (proportion, integral, differential and static) to get to target boost without overshoot whereas one works satisfactorily on the road (static - this is also the way the Unichip boost controller works but is RPM mapped also). So I hope it will be good.
Most aftermarket EBCs appear to use between two and four strategies, the OEM ECU seems to use two (static and integral).
Perhaps if a valve or ball-spring gets very hot it could work differently, but from most assumptions I would think it would boost lower, but it would depend on where exactly it is installed.
I can understand a car with increased boost letting go on the track because of increased temperatures, but why would it overboost? On the road I have tested by running at high revs/full load repeatedly by finding a suitable stretch of deserted road and making full use of my brakes. How is this different to the track? Any insights you have will be useful to me in my design, also what settings do you have to change?
For example, I can get no spikes by turning the proportional gain down or the differential gain up. Getting the balance right you can get no spike at all. If this changes into a 1 PSI spike on the track I can just adjust it a bit more, but use the same integral and static DCs, which are a bit below what is required to allow the system to control with PID which is most effective.
EDIT - CC you arguably get better results after seeing your 12.8 today on a 95 WRX on the std ECU, turbo and TMIC. Incredible, better than all the remapped Scoobies
Not knocking remaps of course. I am not also convinced that a remap on a MY99/00 gives substantially better results than raising the fuel cut by 2 PSI and running a boost controller of your preferred type.[Edited by john banks - 2/24/2002 8:23:14 PM]
24 February 2002, 08:56 PM
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Trout, why ask such an insane question. The people tuning thier cars *SHOULD* know the risks of fitting a bleed valve, or whatever name it is being called this week. If they dont, why are they tuning?
It's the greatest thing since sliced bread, until one goes bang!!!
Dan
[Edited by Danny Fisher - 2/24/2002 9:30:37 PM]
It's the greatest thing since sliced bread, until one goes bang!!!
Dan
[Edited by Danny Fisher - 2/24/2002 9:30:37 PM]
24 February 2002, 09:35 PM
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Danny & Trout,
Can you explain to me in technical terms why you would get overboost with a Unichip or bleed valve on track, and not with a Link or Motec ?
Serious question, as 5 other cars running the same setup as me & playing at the Ring almost every weekend have not seen this strange phenomena yet.
Neither did my car during 3 hours non stop at Zolder last October.
I'm not saying it's completely impossible, but I'm at a loss why technically such a thing would happen.
What is the rational behind it ?
Theo
Can you explain to me in technical terms why you would get overboost with a Unichip or bleed valve on track, and not with a Link or Motec ?
Serious question, as 5 other cars running the same setup as me & playing at the Ring almost every weekend have not seen this strange phenomena yet.
Neither did my car during 3 hours non stop at Zolder last October.
I'm not saying it's completely impossible, but I'm at a loss why technically such a thing would happen.
What is the rational behind it ?
Theo
24 February 2002, 09:49 PM
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Sorry Theo cross posted! RPM based duty cycle as you find is more susceptible to peaks and offsets than more complex methods, but like you I don't know why it would suddenly go completely haywire. The pneumatic system using a bleed valve is still mechanically closed loop after all.
It seems more to do with the operator/tuner of the method than the device. I would rather have a fuel cut lifter and whatever valve you care to mention done by someone that understands what they are doing than a Motec programmed by a Muppet, although this is an extreme example and a Muppet Motec tuner would hopefully last about 5 minutes and no longer. I would argue that a bad mapper could do far more damage with an aftermarket ECU mapped too aggressively in unrepresentative conditions on a device which does not have the same safety features as the original ECU than someone increasing boost with a manual boost controller on a UK MY99/00 by 2 PSI up to 16 PSI where the thing chucks in plenty of fuel and the timing is sensible. Correctly applied I would contend that all tuning methods from the "free" to the 5 figures have a place depending on what you want. Also a superficially appearing simple approach does not prove that appropriate downsides and safety considerations have not taken place.
If someone runs a big turbo, front mount and a FCD and a bleed valve instead of their solenoid all on the original ECU and they have checked the safety data and are happy with it and know the risks why not? Their choice, their engine. Anyone tuning should know they are increasing the risk of premature engine failure, and if they don't accept the risks invovled and find their level they are stupid.
[Edited by john banks - 2/24/2002 9:51:16 PM]
It seems more to do with the operator/tuner of the method than the device. I would rather have a fuel cut lifter and whatever valve you care to mention done by someone that understands what they are doing than a Motec programmed by a Muppet, although this is an extreme example and a Muppet Motec tuner would hopefully last about 5 minutes and no longer. I would argue that a bad mapper could do far more damage with an aftermarket ECU mapped too aggressively in unrepresentative conditions on a device which does not have the same safety features as the original ECU than someone increasing boost with a manual boost controller on a UK MY99/00 by 2 PSI up to 16 PSI where the thing chucks in plenty of fuel and the timing is sensible. Correctly applied I would contend that all tuning methods from the "free" to the 5 figures have a place depending on what you want. Also a superficially appearing simple approach does not prove that appropriate downsides and safety considerations have not taken place.
If someone runs a big turbo, front mount and a FCD and a bleed valve instead of their solenoid all on the original ECU and they have checked the safety data and are happy with it and know the risks why not? Their choice, their engine. Anyone tuning should know they are increasing the risk of premature engine failure, and if they don't accept the risks invovled and find their level they are stupid.
[Edited by john banks - 2/24/2002 9:51:16 PM]
24 February 2002, 10:17 PM
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Just a quick note....
I know everyone is focused on the norm of upping boost ....wise or unwisely ....with such a device...but lets not forget that a bleed valve could be used as a precationary measure if you wanted to limit the boost and it has certainly calmed some serious over boost I have been experiencing with a Group N exhaust.
Also if unexpected overboost has been seen whilst using a bleed valve on a track day.... I am with John... setting this up is no easy matter, and if you have seen it perhaps it was not setup right to begin with. I recon you need the engine HOT ....high speed and I mean high and pick an average day temperature wise. Not p*****g down with rain on a cold day. Try setting your blled then do 120mph, coast for 2 secs then floor it and check any over shoot. The latter is possibly worst case .... but ,most prudent if you are relying on a fixed bleed to keep things together.
So if I am stating the obvious ..... but it helps for clarity.
Julian
I know everyone is focused on the norm of upping boost ....wise or unwisely ....with such a device...but lets not forget that a bleed valve could be used as a precationary measure if you wanted to limit the boost and it has certainly calmed some serious over boost I have been experiencing with a Group N exhaust.
Also if unexpected overboost has been seen whilst using a bleed valve on a track day.... I am with John... setting this up is no easy matter, and if you have seen it perhaps it was not setup right to begin with. I recon you need the engine HOT ....high speed and I mean high and pick an average day temperature wise. Not p*****g down with rain on a cold day. Try setting your blled then do 120mph, coast for 2 secs then floor it and check any over shoot. The latter is possibly worst case .... but ,most prudent if you are relying on a fixed bleed to keep things together.
So if I am stating the obvious ..... but it helps for clarity.
Julian
24 February 2002, 10:20 PM
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... and the very issues you have had on your car are the very reasons I keep telling people not to use Dawes on imports. The UK MY99/00 cars are completely different animals.
24 February 2002, 11:03 PM
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John,
I am not a theoretician, however I am reflecting on observed behaviours on cars. You get good results, great, you have obviously thought about this a lot and understand some of the underlying theory.
I have seen cars set up using devices as you describe, by tuners of good reputation. On the road and RRs they are great - on track they are dangerously useless.
So two points emerge - for DIY tuners who know what to look for - and LINK and Motec are included in this - then the maps - whether physical or electronic can be adjusted accordingly. For example on my car I adjust the the WG Base duty cycle downwards on track to stop the boost rising so quickly - never a problem on the road - but a hot car on track - awful.
However for those who do not know what to look for - or do not understand the limits, as you say yourself, then trouble is only one throttle press away. Although the cars that have been Linked/Moteced professionally by tuners typically have a safety margin tuned in so that track work requires little or no adjustment - in theory.
Yes I was provoking a debate with this post as I seen many people who are not as smart as you jump on the bandwagon to get more power - people who due to price or understanding are much less likely to buy a Link, Motec or an EBC, whack it in and start fiddling. Although that can happen too!
Anyway - my question - why would a bleed valve work on a MY99 and not an Sti V? Or is this purely because the JECS in the STi V has very poor fuelling, especially in key areas, like 7,000rpm?
Trout (<12.8)
I am not a theoretician, however I am reflecting on observed behaviours on cars. You get good results, great, you have obviously thought about this a lot and understand some of the underlying theory.
I have seen cars set up using devices as you describe, by tuners of good reputation. On the road and RRs they are great - on track they are dangerously useless.
So two points emerge - for DIY tuners who know what to look for - and LINK and Motec are included in this - then the maps - whether physical or electronic can be adjusted accordingly. For example on my car I adjust the the WG Base duty cycle downwards on track to stop the boost rising so quickly - never a problem on the road - but a hot car on track - awful.
However for those who do not know what to look for - or do not understand the limits, as you say yourself, then trouble is only one throttle press away. Although the cars that have been Linked/Moteced professionally by tuners typically have a safety margin tuned in so that track work requires little or no adjustment - in theory.
Yes I was provoking a debate with this post as I seen many people who are not as smart as you jump on the bandwagon to get more power - people who due to price or understanding are much less likely to buy a Link, Motec or an EBC, whack it in and start fiddling. Although that can happen too!
Anyway - my question - why would a bleed valve work on a MY99 and not an Sti V? Or is this purely because the JECS in the STi V has very poor fuelling, especially in key areas, like 7,000rpm?
Trout (<12.8)
24 February 2002, 11:07 PM
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CC,
I am completely with you mate, and John for that matter - I am concerned, altruistically, about the guy who whacks in his bleed valve and his FCD for 47p or whatever. Gets his fabulous result on the rollers, and knowing no better decides to go a track day and comes home on a transporter.
Yeah, everyone pays there money and takes their choice - I guess this is just a very long 'caveat emptor' for readers.
Avuncular mode off!
Trout
I am completely with you mate, and John for that matter - I am concerned, altruistically, about the guy who whacks in his bleed valve and his FCD for 47p or whatever. Gets his fabulous result on the rollers, and knowing no better decides to go a track day and comes home on a transporter.
Yeah, everyone pays there money and takes their choice - I guess this is just a very long 'caveat emptor' for readers.
Avuncular mode off!
Trout
25 February 2002, 06:49 AM
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Trout - you scaremongerer
Me no understand why a correctly installed MBC will cause problems on track? On track all that happens is things get hotter - but this applies to all cars. I think it's safe to say that 80% of people playing with this sort of thing monitors for at least knock, most likely AFR too.
But then, so do people running a link, no? I guess BRD strongly recommend fitting both with the link - wouldn't surprise me if they made it statutory
Any sort of tuning pushes the envelope, requiring you to monitor in case of problems. There are those that don't, but hopefully they don't go on track!
An MBC on an import is not good 'cos the ecu is mapped for 100ron, giving less adjustment within the map.
Richard
Me no understand why a correctly installed MBC will cause problems on track? On track all that happens is things get hotter - but this applies to all cars. I think it's safe to say that 80% of people playing with this sort of thing monitors for at least knock, most likely AFR too.
But then, so do people running a link, no? I guess BRD strongly recommend fitting both with the link - wouldn't surprise me if they made it statutory
Any sort of tuning pushes the envelope, requiring you to monitor in case of problems. There are those that don't, but hopefully they don't go on track!
An MBC on an import is not good 'cos the ecu is mapped for 100ron, giving less adjustment within the map.
Richard
25 February 2002, 08:01 AM
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Richard, what possibly can happen ... we saw this time & time again whilst finetuning my map : you go out for a quick setup, and set boost to 1.2 bar... then trash it more & more and you slowly see the boost creep to 1.3 bar.
Possible reasons would be : cooler engine temps at prolonged boost (strange, but true, if your map is set on safety, the fuel dumps on full boost will actually cool the engine/EGT's) and maybe also the fact that you burn off all possible carbon deposits on the spark plugs (from driving slowly / cold engine)
So you really really need to push the car *hard* before setting maximum boost. On a RR, due to inlet temps, this may not be possible.
Oh, the joys of having a German autobahn near you Really warm up the car, and do a few heavy bursts in 5th... that's the peaks you will get on track as well.
Trout, caveat emptor is always good, especially when playing with engines. Also agree it's a good thing you can adjust your own boost control with the Link/Motec when going on track. Which now makes me think about adding a bleed valve to my Unichip setup LOL ... not what you intented when you started this thread I'm sure
Theo
Possible reasons would be : cooler engine temps at prolonged boost (strange, but true, if your map is set on safety, the fuel dumps on full boost will actually cool the engine/EGT's) and maybe also the fact that you burn off all possible carbon deposits on the spark plugs (from driving slowly / cold engine)
So you really really need to push the car *hard* before setting maximum boost. On a RR, due to inlet temps, this may not be possible.
Oh, the joys of having a German autobahn near you
Really warm up the car, and do a few heavy bursts in 5th... that's the peaks you will get on track as well.Trout, caveat emptor is always good, especially when playing with engines. Also agree it's a good thing you can adjust your own boost control with the Link/Motec when going on track. Which now makes me think about adding a bleed valve to my Unichip setup LOL ... not what you intented when you started this thread I'm sure
Theo
25 February 2002, 08:16 AM
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Thanks Theo
Didn't notice this at Nurburgring - was only running 1.1bar at the time.
Interesting though - I shied away from running full boost down all the straights and actually backed off to half throttle once over 170 or so. You think EGT's actually lower if you keep it floored with a PPP ecu too (also very rich)?
Really must sort an egt gauge....
Richard
Didn't notice this at Nurburgring - was only running 1.1bar at the time.
Interesting though - I shied away from running full boost down all the straights and actually backed off to half throttle once over 170 or so. You think EGT's actually lower if you keep it floored with a PPP ecu too (also very rich)?
Really must sort an egt gauge....
Richard
25 February 2002, 08:18 AM
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How about a valve instead of your restrictor Theo then you could turn the boost down as well as up? Then you won't have the shame of telling people you have a bleed valve At present as I understand your system the net effect to your wastegate diaphragm is a combination of your restrictor and your duty cycle.
At present as I understand your system the net effect to your wastegate diaphragm is a combination of your restrictor and your duty cycle.
25 February 2002, 11:00 AM
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One of the reasons you can overboost on the track is that the exhaust gas turbine on the turbo only reaches maximum efficiency at higher temperatures. This means that for a set wastegate opening you will produce more boost with a hot turbo than a warm one. (say 700 vs 400 deg C EGT)
25 February 2002, 11:41 AM
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John, from a purely theoretical point of view, I dont understand why you have four parameteres controlling boost targets.
Even if you do, a properly set up PID controller, regardless of how it achieves its goal, requires thecorrect coeffeicients to act quickly, how did you attain these figures.
On top of this, the best possible response from a PID controller operating on error, is critical damping defined as the lowest possible time to reachthe target. Graphically this appears as a slight overshoot, follwed by an undershoot finally settling on the correct target value.
The standard setup using an integral and static controller, is in fact the safest way theoretically as it doesnt generate over boost at all, but if yours is setup to work as a PID controller should when optimal, then it is trying to overboost in order to reach critical damping.
This is not a criticism at all, please dont take this as an attack, I just want to know how you can achieve the target boost at a fast enough speed without overshooting and hence over boosting.
Even if you do, a properly set up PID controller, regardless of how it achieves its goal, requires thecorrect coeffeicients to act quickly, how did you attain these figures.
On top of this, the best possible response from a PID controller operating on error, is critical damping defined as the lowest possible time to reachthe target. Graphically this appears as a slight overshoot, follwed by an undershoot finally settling on the correct target value.
The standard setup using an integral and static controller, is in fact the safest way theoretically as it doesnt generate over boost at all, but if yours is setup to work as a PID controller should when optimal, then it is trying to overboost in order to reach critical damping.
This is not a criticism at all, please dont take this as an attack, I just want to know how you can achieve the target boost at a fast enough speed without overshooting and hence over boosting.
