Boost question for Impreza WRX
Discussion
Apologise for my lack of knowledge on this subject. Have tried to do a few searches but can't find anything particular on this topic. Had a lot of work done on my MY05 car a few months ago including uprated turbo, injectors, pump, induction kit and re-map. On the rolling road increased output to 347 BHP with 18 PSI max boost. After some spirited driving hit rev limiter on one occasion and engine warning light came on for a bit and then went off again. Seems to have been driving ok but just had some defi guages fitted and had a few questions.
1. What is the significance of the negative boost figures?
2. I only ever seem to reach peak boost when accelerating in top gear. Is this normal?
3. What is the significance of the warning light and beeping at peak boost and should I be worried about this?
4. Does anyone have a link to what I should expect to see on the boost guage under hard acceleration as there is not much info in the instruction manual and I have a suspicion that the dump valve may be dumping too early as the boost only seems to be maintained for a couple of seconds at the most.
Once again I apologise if these are really stupid questions but any help would be greatly appreciated. After the re-map the boost was running at 18 - 19PSI between 3500 and 6000 rpm
1. What is the significance of the negative boost figures?
2. I only ever seem to reach peak boost when accelerating in top gear. Is this normal?
3. What is the significance of the warning light and beeping at peak boost and should I be worried about this?
4. Does anyone have a link to what I should expect to see on the boost guage under hard acceleration as there is not much info in the instruction manual and I have a suspicion that the dump valve may be dumping too early as the boost only seems to be maintained for a couple of seconds at the most.
Once again I apologise if these are really stupid questions but any help would be greatly appreciated. After the re-map the boost was running at 18 - 19PSI between 3500 and 6000 rpm
Socr8s said:
Apologise for my lack of knowledge on this subject. Have tried to do a few searches but can't find anything particular on this topic. Had a lot of work done on my MY05 car a few months ago including uprated turbo, injectors, pump, induction kit and re-map. On the rolling road increased output to 347 BHP with 18 PSI max boost. After some spirited driving hit rev limiter on one occasion and engine warning light came on for a bit and then went off again. Seems to have been driving ok but just had some defi guages fitted and had a few questions.
1. What is the significance of the negative boost figures?
2. I only ever seem to reach peak boost when accelerating in top gear. Is this normal?
3. What is the significance of the warning light and beeping at peak boost and should I be worried about this?
4. Does anyone have a link to what I should expect to see on the boost guage under hard acceleration as there is not much info in the instruction manual and I have a suspicion that the dump valve may be dumping too early as the boost only seems to be maintained for a couple of seconds at the most.
Once again I apologise if these are really stupid questions but any help would be greatly appreciated. After the re-map the boost was running at 18 - 19PSI between 3500 and 6000 rpm
Best thing you can do is go back to the people that did the work on your car and talk to them. Without knowing exactly what your setup is and how it's been mapped it's very difficult to say anything about what boost, power figures, etc you should expect to see.1. What is the significance of the negative boost figures?
2. I only ever seem to reach peak boost when accelerating in top gear. Is this normal?
3. What is the significance of the warning light and beeping at peak boost and should I be worried about this?
4. Does anyone have a link to what I should expect to see on the boost guage under hard acceleration as there is not much info in the instruction manual and I have a suspicion that the dump valve may be dumping too early as the boost only seems to be maintained for a couple of seconds at the most.
Once again I apologise if these are really stupid questions but any help would be greatly appreciated. After the re-map the boost was running at 18 - 19PSI between 3500 and 6000 rpm
Negative boost means power loss, positive boost means you're making power therefore i can only deduce that there is either a restriction in your induction system somewhere or you are leaking air possibly from a hose that's blown off or perished.
Impreza's would normally make peak power in 3rd or 4th gear so making it in top gear i think isn't right, and i'm willing to be proven wrong here if anyone knows any better.
The light and beep from your boost guage is just telling you you have reached peak boost so i wouldn't worry about it, and if you are worried just back off the throttle but it sounds like your turbo is probably capable of making a bit more. What did they fit?? VF35 or hybrid?? 18-19psi is easy VF35 capability but it will go to 1.5bar (21.7psi) no probs.
As for the dump valve....Subaru's have a perfectly good recirculating dump valve and not worth changing until you are making some real power, probably over 400bhp. Does your dump valve go 'pssssshhhht'??
At 347bhp i would have said that is as much as you would want to go on a standard internals MY05 WRX and probably right at the safe limit. In fact i probably wouldn't have gone that far long term and i'd have left it at about 330bhp for reliability. It's a 2.0L isn't it?
To get real figures and an answer to all your questions you would have to do some serious datalogging to see what the engine is really doing but as i said initially, talk to your engine modders/mappers.
By the way....who did the mapping?? I'm interested because i do all my own mapping
Yes the dump valve is an atmospheric one. My main worry was that I had caused some damage to the turbo when the engine warning light came on. It is a 2L and the turbo is a VF34. I got all the work done at scoobyclinic a few months ago and have just been back there to get the dials done and a service. Was thinking it may be an idea just to stick it on a rolling road to see what is happening but am in Essex and as I've just done the journey up to Chesterfield would be happy to go somewhere nearer for diagnostic purposes. Where are you based scoobywrx?
I'm based in Northampton.
Chesterfield seems like a long way to go when you have companies like Zen Performance (Subaru Tuning Masters) in Wellingborough who have a brand new DASTEK Dyno, APT Performance Tuning in Norwich who run a rolling road and tune mostly Mitsubishi/Nissan but have a lot of performance tuning experience, GRD in Surrey (scooby specialists) who use the Surrey Rolling Road Dyno next door to them, and even closer to home is Engine Advantages in Witham that have a 4x4 Dyno.
There are plenty to choose from within close reach of you but you do need to understand what Scooby Clinic have actually done in terms of mapping. A good tuner with a decent 4x4 rolling road will be able to tell you exactly what the score is, or you could get the appropriate hardware and software to allow you to datalog your vehicle dynamics on the road.
EcuTek DeltaDash (not something i use though) is a good way forward if you have EcuTek mapping on your car, but will cost you, although at least that way you will always have a means by which to measure your engines performance and log different parameters like BHP/Torque, Air Fuel Ratios, Wastegate/Injector Duty cycles, Turbo Boost, Timing, Knock correction etc...etc...
In my humble opinion on-the-road tuning/datalogging is more accurate than a rolling road as it reflects real-world engine dynamics as opposed to measuring a static car on rollers, and besides non of us drive on rolling roads so surely it's better to know what the car is doing in the real-world.
Dyno's however do allow you measure the engines output/dynamics in a controlled environment that will generate consistent results everytime. On-the-road has too many constantly changing variables to to give you consistency so it's horses for courses really. Depends on what you want to find out, and if you don't have experience in datalogging and interpreting those results stick to a rolling road and let the experts tell you what's going on and how to fix it.
Have scoobyclinic gone for out and out power at the top end or have they made it more driveable and more torquey bottom end/mid-range?? A few Dyno power runs will give you an idea of where you are with the car right now and if anything has changed since your initial Dyno runs immediately after mapping. I assume you still have the original Dyno printout to compare to.
Hope this helps
Chesterfield seems like a long way to go when you have companies like Zen Performance (Subaru Tuning Masters) in Wellingborough who have a brand new DASTEK Dyno, APT Performance Tuning in Norwich who run a rolling road and tune mostly Mitsubishi/Nissan but have a lot of performance tuning experience, GRD in Surrey (scooby specialists) who use the Surrey Rolling Road Dyno next door to them, and even closer to home is Engine Advantages in Witham that have a 4x4 Dyno.
There are plenty to choose from within close reach of you but you do need to understand what Scooby Clinic have actually done in terms of mapping. A good tuner with a decent 4x4 rolling road will be able to tell you exactly what the score is, or you could get the appropriate hardware and software to allow you to datalog your vehicle dynamics on the road.
EcuTek DeltaDash (not something i use though) is a good way forward if you have EcuTek mapping on your car, but will cost you, although at least that way you will always have a means by which to measure your engines performance and log different parameters like BHP/Torque, Air Fuel Ratios, Wastegate/Injector Duty cycles, Turbo Boost, Timing, Knock correction etc...etc...
In my humble opinion on-the-road tuning/datalogging is more accurate than a rolling road as it reflects real-world engine dynamics as opposed to measuring a static car on rollers, and besides non of us drive on rolling roads so surely it's better to know what the car is doing in the real-world.
Dyno's however do allow you measure the engines output/dynamics in a controlled environment that will generate consistent results everytime. On-the-road has too many constantly changing variables to to give you consistency so it's horses for courses really. Depends on what you want to find out, and if you don't have experience in datalogging and interpreting those results stick to a rolling road and let the experts tell you what's going on and how to fix it.
Have scoobyclinic gone for out and out power at the top end or have they made it more driveable and more torquey bottom end/mid-range?? A few Dyno power runs will give you an idea of where you are with the car right now and if anything has changed since your initial Dyno runs immediately after mapping. I assume you still have the original Dyno printout to compare to.
Hope this helps
Edited by ScoobieWRX on Thursday 3rd July 12:47
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