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Practical Reflash Tuning

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I'm currently tuning a 370z that has had a pair of 2860 turbos (-5 I'm pretty sure) attached. It has bigger injectors, GTR AFMs that are blow through, and water meth injection. 2 x 275ml/min nozzles. Also has a G7 IPC boost controller set up. (Has a digital input connected to the WMI low level switch so that it can drop the boost to gate pressure (4psi) when the WM is empty)

Okay so 10psi of boost, lots of timing! (14-17 degrees from 4k to 7k rpm). IATs are around 47-55 degrees. Engine temps are around 105 degrees, and AFRs are 11.5:1 average on WOT. Earlier on it was making the same / more power with about 6-8 degrees less timing which is unusual. It did make 430rwhp one run, but I am unable to replicate that power again.

The best it can do is 400rwhp. I am told this should be closer to 500rwhp at 10-12psi.(Dyno has been tested and is quite accurate. Its a Dynotech.

We have removed the filters, boost leak tested (pressurised the intake), no wheel spin on the dyno etc.

Sprayed water on the intercooler, and just generally checked everything. It's driving us mad.

I have the plex knock kit connected, and I am not hearing knock and the engine is not pulling timing due to knock via the logs.

I have also eased off the cam advance in the higher RPM to allow it to breathe better.

it seems to fluctuate about 10 degrees engine temp per run, and each run it loses almost 10hp each time.

I have not touched the VVEL yet. I am also using the ARC features and the simplified timing map.

I have turned on the launch control and that doesn't even work when switched on and set.

The vehicle has only done 40,000km since new. It is in showroom condition.

If you can give any advice please let me know. I would be very grateful.

Sounds like a pretty interesting issue.

My first thoughts would be, can you ensure it is actually getting the timing you're commanding? Does the logging show it is accurate?

The fact you have added another 6-8degs and it is making the same power and not knocking suggests you aren't?

I have tuned quite a few turbo and supercharged 350Z Using UpRev and can't say I have seen this issue other than when it goes into the knock map.

If you have a copy of the tune feel free to put it up and I can have a look for you.

I haven't done any of the 370z motors turbo or SC although I would expect more than 400hp, also with the amount of timing you say it is taking.

Is the engine internally stock and hasn't been touched?

Thanks for the reply Chris. We managed to get it sorted. I noticed the power wasn't consistent. When we filled the water meth up, I left the hatch open and did a few runs. then... I could smell burning rubber.

With some adjustments to the straps, and a little tweaking, I was able to get 440rwhp at 10psi.

I was still a little frustrated at the power because it should have been making more, but then the workshop owner let me know that his dyno has been reading 10% less than all dynos around town (proven with back to back tests of other cars going straight to the other dyno just to do a power run and test)

So technically this thing should have closer to 480-500rwhp. And after a run on the street, it certainly does feel like that!

I have uploaded the dyno graph. I spent some time tweaking the cams to get a nice smooth curve.

It is a little embarrassing realising the issue was something as simple as wheel-spin, but it was a weird one because there was no rubber coming from the tyres. They were just shiny. Good tyres too. We also let them down and then started to get better traction.

Attached Files

Got some screenshots showing your intake VTC position and your VVEL angles?

Also, post screenshots of your main VVEL and VTC tables.

Glad you got it sorted Jono! I've had similar on our Mainline a few times where the wheel spin has not been perhaps as obvious as you'd expect. A good trick is to look at the relationship between engine rpm (with an external tacho input) and wheel speed as these should be close to a straight line. If you suspect wheel spin then this can really quickly confirm your suspicion.

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