My Visa Gti Mi16 Rolling Road Graph Query

[VisaGTi16v 1]

Hi,

 

I had my Visa sprint/hillclimb car rolling roaded at Sanspeed back at the start of last season. The graph I got from them was in 4th gear, kilowatts at the wheels against speed in kmh. I have just painfully plotted and calculated this into mph, bhp and torque using its known ratios etc. I then applied David Bakers (pumaracings) estimated flywheel power formula to get the below graph.

 

I think its ok power wise as its a 90k old bottom end, the head is a Hiflow heads "stage 2" whatever that means, light porting and gas flowing I think. It then has some 264 duration Piper fast road cams. Only other modification is a k&n. The timing has not been checked but I run it on Super unleaded. The exhaust manifold was ported when I got it, straight through exhaust to a ~55mm exit rear box (since replaced with a OMP 50mm Grp N one)

 

My query is relating to the power curve at the end of the scale, from about 6600 it basically goes flat until the standard 7200 limiter. The camshafts "Range" is quoted as 1500-6500 so is it likely to be due to them? Or could it be a lack of fuel or something like the injectors are running flat out as when new are only rated to 180bhp (or something I read somewhere)?

 

Any comments would be useful thanks

 

Darren

http://www.visagti.com

[Rippthrough 98]

That's an amazing torque curve if that's right!

[VisaGTi16v 1]

Well thats another thing. It doesnt feel like it pulls that well at low revs compared to say my Xsara VTS road car but then theres so much noise and stuff going on due to it being totally stripped out that its hard to judge, plus the speedo isnt connected so can only go by the rev counter. I plotted torque = bhp x (5252/rpm) and copied and pasted what was off my print out from the rolling road and the bhp curve seems to go up in a "normal" manor but I do agree, it is quite flat

[VisaGTi16v 1]

This is a graph I found years ago somewhere apparently of a standard Mi16 which also shows quite a flat curve once you are over 2500 which can be seen on mine as well

[VisaGTi16v 1]

They both have the same torque dip at 3600rpm, wonder why that is?

[welshpug 1,632]

standard characteristic of a psa 16v engine

[Sandy 191]

It's probably true to say that the Puma Racing wheels to Fly formula (which is strictly an estimate of course), only really works around peak power. The constant element is going to throw it out at lower rpm.

[VisaGTi16v 1]

Ok. I did plot a graph of wheel figures which were 141.5bhp and 113.3ft/lb at the same rpm as above. The graph curves are the same though which is what im really interested in, not the figures/power. A friend has reminded me that he has one of those exhaust gas temperature devices for me to use as im told if its running lean at high revs the exhaust gas temp will go up which could show a fueling problem. I am just curious about why it goes flat thats all at 6600 up.