3.9i Dyno Results

[jomeo]

Hey guys.
Had our V8 Rolling Roaded today to see what was going on. All in all a good session with some interesting outcomes. Im pretty sure its all in order and running well. Smooth power curve but there is a area of slight concern.
if anyone knows what it could be it would be really cool to know.

As far as we know this is a standard engine so im guessing power figures and torque are about right????

The thing thats got me is AFR (Sorry bout the orientation)



On all 3 power runs at 2750 exactly every time its leaning off i think down to below 12.5. ok this is having a effect on the torque curve which pops up slightly at this point and it does level out after that point but the fact it does this on every run leads me to think that it could be something in the ECU map but id like some feedback as to what people are thinking?? and how this could be addressed without affecting the smoothness of the engine at the mo.



Would be interesting to get some feedback on this.
Thanks guys.
Joe

[katanaman]

if its stock ECU could it be that the factory has leaned it out for emissions? Never seen a stock AFR print so wouldn't really know what they are meant to look like.

[CastleMGBV8]

John,

If thats a standard 3.9 on hotwire it looks to be in a good state of health.

It is in fact going a little rich at 2750 RPM and putting a dent in your torque curve, it would appear to be running slightly lean between approx 3100 - 4000 RPM for WOT but not really anything to worry about and just a factor of the standard ECU probably.

Kevin.

[jomeo]

Yes as far as we know its totally standard.
Is it worth getting it mapped to take out the issue at 2750 or would that do more harm than good as its running very well at the moment??

[CastleMGBV8]

You would spend over £400 for a Mark adams chip and then the rolling road costs of setting it up for very little gain.

For that money you could get yourself a pair of stage 1 heads which would give you another 30-35BHP with no need to modify the ECU

Look up Peter Burgess site for Rover Econotune (Stage 1) heads, they make all the difference.

Just to clarify, an AFR of 12.5 is relatively rich, the lower the number the richer the mixture. Cruise at 16.0 + is lean for economy on a light throttle.

Kevin.

[JSF55]

Isn't 3000 rpm where they normally hold the engine at for the emissions tests on the MOT ? ideal candidate to go for mappable injection ?