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Discussion Starter #1
Does anyone know why Cedric's dyno has such an unusual slope? It keeps building power whereas many of the other dyno's build power and then seem to level off at some point.
 

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carcnoid said:
Does anyone know why Cedric's dyno has such an unusual slope? It keeps building power whereas many of the other dyno's build power and then seem to level off at some point.

My SP60 dynos were done at low to medium boost. The turbo still had plenty left so the slope was still climbing when I let out. The guys at the dyno noticed that too and kept wanting me to turn the boost up.
 

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My SP63 made peak hp at 6700 rpm (where I let off). I think the difference is that a single turbo with a good boost controller will hold boost all the way to redline. The boost on stock twins will fall off well before redline causing the power to drop.

Later, Steve
 
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What I mean by my question is that Cedric's car seemed to reach peak HP and TQ way after other turbos. A T78, for instance, makes peak HP and TQ at 4500 RPM, while the Cedric's car was nowhere near that.

Is there something wrong with your boost controller?
 

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I may be wrong, but I think your seeing two different bottlenecks. On a stock twin car you will not make peak hp at high rpm because the turbos can't push enough air. On a car with a big turbo you are pushing more air than the heads/cams (and possibly the intake manifold) can flow. This makes the power drop off at higher rpm. On SP57-SP63 cars you have a turbo that at 20-23psi is capable of holding boost to redline, but doesn't out flow the head/cam. This is just my theory and other people on the forums are more knowledgeable than me on this subject. Hopefully others will reply.

Later, Steve
 

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Oh, ok now I understand what u mean. More than likely the A/F ratio is the culprit. When my turbo comes online at full boost my car goes extremely rich causing me to lose power. As the ECU adjusts to the boost levels my A/F normals up a bit and I start making better power as the RPM's increase. I have tried using the AFC to clean this up a bit but it is still not where I want it. The car seems to run fine and is still quicker than a BPU Supra even from a stop(tested it out) so the graph may be a bit misleading. I think that my front O2 sensor is bad. I will know more when I get a chance to check my codes. I will re-dyno after that and post what I get.
 
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Thanks! Sorry for the confusion :/ Your car makes full boost around 4500 RPM right? Mine makes it a tad bit earlier than that. I will put her on a dyno when I get back in the states. I will be sure to post the results :).
 

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carcnoid said:
Thanks! Sorry for the confusion :/ Your car makes full boost around 4500 RPM right? Mine makes it a tad bit earlier than that. I will put her on a dyno when I get back in the states. I will be sure to post the results :).
With the SP60 I hit full boost at about 36-37k. With the SP63 I hit it at about 39 to 40k.
 

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Cedric,

When you did 560 on stock fuel, How many #'s of boost was that?
What precautionary measures did you take,if any? Not just on that dyno run but, on the street. How many #'s of boost could you run safely on pump gas?

Thanks Matt
 

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M Miller said:
Cedric,

When you did 560 on stock fuel, How many #'s of boost was that?
What precautionary measures did you take,if any? Not just on that dyno run but, on the street. How many #'s of boost could you run safely on pump gas?

Thanks Matt
It was at 1.57 KG/CM2...not sure of the psi on that one. I had been tuning the car for 2 hrs before doing a full boost pull and I slowly increased boost while checking the A/F ratio. I could run 1.2 kg/cm2 on pump gas which was a lil over 500rwhp.
 
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Hi Cedric

I spoke to you over the phone a long time ago, back when you had your red MKIV.

Anyhow, 1.2 kg/cm^2 is approximately 17.64 psi.

1.57 kg/cm^2 is approximately 23.079 psi.

Stan
 
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