Hi everyone!

I recently got my car road tuned and out of curiosity I got it dynoed to see what power it was putting down. The dyno was at a mechanic different to the one that did the tune so I expected him to try and fault the tune. On the attached dyno graph he said that the tune was way too lean around 4,000rpm where the AFR is ~12.4. He said that it should be around 11.9 and that if I tracked the car like I wanted to the engine would blow at those AFR levels. Is this guy just being dramatic or does he have a point?

Thanks for any help!

George

 

Hey mate,

Who road-tuned the car?
Did they leave lean-spool switched on? If so, this may be just the workings of that and unless the dyno operator did either 2-3 runs back to back or loaded it up for 4-5 seconds hard prior to commencing the power run, the first pull will always be quite lean.

Honestly, thats what looks to be taking place judging by the AFR graph.

Its very hard to comment if the existing tune will 'blow up' without seeing a log of knock, timing trace etc.

 

12.4 is no good. might blow. you should target around 11.2 ish to make power and be safe.

 

Let's start with the basics....what type of fuel?

 

I've read and been told to tune for about 11.5-11.1 on pump (93).

 

The tuner was Meek Automotive who has a good reputation for working on Evos. Benja, not too sure what the lean-spool switch is so can't say whether that was causing these results. The fuel used was BP 98 octane.

The dyno operator had a few minutes between the 3 pulls done and once changing into 4th they immediately went into the pull so they didn't excessively load it up.

The 12.4 AFR is at 4,100rpm but then it comes off to low 11s. What I was worried about was that on a track you'll probably be in that 4000 rpm zone a fair bit coming out of corners etc. and this mechanic advised that I didn't go to the track with the way the tune is now. So you guys reckon that having an AFR that lean at that point in the tune is risky?

 

12.5 to 12.7 afr is mainly for a car with meth on 93 oct, which is what mine was tune to.
What fuel you are using my friend? I don't think 12.4 will kill your motor as you say it gets richer on top. I am not a tuner but from what I know once your afr is on point at wot then you should be fine.

 

Check the AFR on the street. Do a datalog. The load on the dyno could be different than the street, which could skew the readings.

 

This cause that will be a lot closer to what it really does. It also depends on the timing so you should check that and knock. Regardless if this is going to the circuit the tune needs to be more conservative than a drag or street pull car since you need it to hold up for 20min+ sessions.

 

Is the dyno wideband a tail pipe one? Cuz they can read leaner then it actually is if there any small leaks in the exhaust system or if the sensor is not into the tail pipe deep enough.

 

Guys thanks for the replies. Yeah I've got an AFR gauge so will take it to a quiet spot and see what it's doing through the rev range. I don't have any equipment to log it or look at the knock count unfortunately.

@ Boosted Tuning: They put something in the tailpipe which I assume was the wideband. Not too sure if it was deep enough or not.

Seems like there are loads of factors that could affect that dyno reading and whether that AFR is something to be concerned about or not. It could probably be a lot worse though I guess! It could just be a case of the dyno mechanic being sore over the fact that the car was tuned at a competing mechanic and wanted to criticise the work done.

 

If you need, I can sort it for you.
I'm up in Newcastle.