Turbo boost kick
06-20-2003, 07:12 PM
#1
Three Wheelin'
Thread Starter
Turbo boost kick
What needs to be changed for the 951 to have a real kick when the boost hits? Wastegate? Electronic boost controller? My car reaches the desired boost, and I have the boost enhancer to prevent bleeding to the wastegate, but the car still gradually comes to full boost. Is this a wastegate issue?
06-21-2003, 09:45 AM
#4
Burning Brakes
You don't won't boost to kick in big time. The whole point of a 951 turbo is that it doesn't feel like a turbo powered car at all. Any racer will tell you that smooth is the way - you can spend more time concentrating on getting the bends right! This is why our cars are so good - puting power smoothly on the road with no drama -speed increasing fast - just stopwatch the figures and compare to other cars!
06-21-2003, 04:08 PM
#5
Instructor
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by SimonK:
<strong>You don't won't boost to kick in big time. The whole point of a 951 turbo is that it doesn't feel like a turbo powered car at all. This is why our cars are so good - puting power smoothly on the road with no drama -speed increasing fast - just stopwatch the figures and compare to other cars!</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Simon/Mike, my experience has been the opposite. I'm only running .95-bar boost, and my 951 pulls like a freight train above 3500 RPM. Granted, I have some minor mods (see signature), but one of the things that struck me about the car when I first got it was how abrupt the transition was from off-boost to full boost (refined motoring is not part of my engine's vocabulary). The only time that my car made a relatively smooth (but very, very slow) transition in this regard was when I had a vacuum hose slip and disconnect. Reconnecting it restored power and brought back the familiar turbo kick that Mike referenced in his post. Consequently, I'd recommend checking vacuum line connections. If you have stock chips though, absence of drama may be part of the equation.
Hope it's something simple in any event.
<strong>You don't won't boost to kick in big time. The whole point of a 951 turbo is that it doesn't feel like a turbo powered car at all. This is why our cars are so good - puting power smoothly on the road with no drama -speed increasing fast - just stopwatch the figures and compare to other cars!</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Simon/Mike, my experience has been the opposite. I'm only running .95-bar boost, and my 951 pulls like a freight train above 3500 RPM. Granted, I have some minor mods (see signature), but one of the things that struck me about the car when I first got it was how abrupt the transition was from off-boost to full boost (refined motoring is not part of my engine's vocabulary). The only time that my car made a relatively smooth (but very, very slow) transition in this regard was when I had a vacuum hose slip and disconnect. Reconnecting it restored power and brought back the familiar turbo kick that Mike referenced in his post. Consequently, I'd recommend checking vacuum line connections. If you have stock chips though, absence of drama may be part of the equation.
Hope it's something simple in any event.
06-21-2003, 05:36 PM
#6
Three Wheelin'
Thread Starter
OK, let me tell a little more about what I mean. First of all, my car is an '86 951 with an APE MAF, APE stage 3 chips, LBE, stock wastegate and 12psi (due to leaky seals - soon to be replaced.). My thoughts on the LBE were that it was designed to help give the turbo a little more of a kick (help the turbine spool up faster by blocking all signal to the WG). Is this the confusion? A turbo that spools up faster does not necessarially punch you back into the seat, rather gradually smash you into it, just at lower RPMs. I think it's becoming clearer now. The gradual push is not bad by any means. 
I've just ridden in some turbo cars that break the tires free when the boost hits. But it sounds as thought that is a HP/PSI issue. Any other comments?
I've just ridden in some turbo cars that break the tires free when the boost hits. But it sounds as thought that is a HP/PSI issue. Any other comments?
06-22-2003, 05:26 AM
#7
Race Director
"My thoughts on the LBE were that it was designed to help give the turbo a little more of a kick (help the turbine spool up faster by blocking all signal to the WG). Is this the confusion?"
No confusion, just that the LBE acts on the wastegate. But if the wastegate was faulty, there's nothing the LBE can do. Such as if you had a weak spring that doesn't hold back exhaust pressure. This wastegate would then open prematurely and leak exhaust that could've driven the turbo (even with zero pressure on the diaphragm).
One way to test the boost-controller is to clamp-shut or disconnect the hose going to the wastegate. Gently do several runs with increasing throttle each time (1st one should be 1/4 throttle only). Does the boost come on quicker? If so, your LBE is leaking and causing the wastegate to open.
If not, you've got either a wastegate or a clogged cat issue, or bad turbo bearings, bent shaft, etc.
No confusion, just that the LBE acts on the wastegate. But if the wastegate was faulty, there's nothing the LBE can do. Such as if you had a weak spring that doesn't hold back exhaust pressure. This wastegate would then open prematurely and leak exhaust that could've driven the turbo (even with zero pressure on the diaphragm).
One way to test the boost-controller is to clamp-shut or disconnect the hose going to the wastegate. Gently do several runs with increasing throttle each time (1st one should be 1/4 throttle only). Does the boost come on quicker? If so, your LBE is leaking and causing the wastegate to open.
If not, you've got either a wastegate or a clogged cat issue, or bad turbo bearings, bent shaft, etc.
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06-23-2003, 11:08 PM
#8
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The boost delivery on my car is now much smoother than when I purchased it last year. I attribute it to some combination of replacing vacuum lines, installing the Reliaboost controller, and bypassing the cycling valve.
Ron
Ron
