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Supercharged xr8 tuning


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Just wanting to pick the brains of the tuners on here as to what they would be looking at tune wise for my car.

It's a built boss 260 with a side mount charger, 6 spd manual, bigger throttlebody, 1000cc injectors, bigger fuel system etc.

I have a tune in it that I have written and some of that tune came from a shop who tuned it  previously and then I modified it in places as I wasn't happy with it and I also changed from auto to manual and changed charger brands.

I am still not completely happy with and feel like I am missing something, so I was just wondering what people's thoughts were and the things they would be starting with.

Sorry for the long post and thanks in advance for any help. Scotty

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What in particular aren't you happy with?

WOT, AFRs, Cold start, return to idle, boost? 

I find a lot of issues can be remedied with dialing in injectors and fueling as these often cant and wont be 100% from a tuner in the short time they have with the car unless they provide the injectors and have a good understanding in how they work in a setup.  Do you have a fuel reg where you can see fuel pressure?  This will help too.

I would start there in any case and see how it all feels after that.

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Idle, return to idle are the things I am mostly unhappy with.

I did have injector issues but they are dialed in pretty well now. I have got an adjustable fuel pressure reg and gauge and it's sitting on 4 bar.

I am thinking it's probably more air flow issues that are giving me dramas esp with the size of the tb and the boost from the side mount.

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2 hours ago, scotty said:

I did have injector issues but they are dialed in pretty well now.

Can you post up a scatter plot showing your LTFT vs air flow or load? A lot of people say this but they are still swinging 20% in places. 

What actually happens, does it stall? Or does it hunt?

If you can take some datalogs of the problem and highlight exactly where in the datalog the problem occurs this will help, datalog everything relevant, eg throttle, rpm, injector pulsewidth, fuel trim. Otherwise we will be guessing.

At a guess it's possible your supercharger bypass is causing the idle system to fight at idle.

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The problems are slowing too return to idle and hunting at idle. I will get a datalog in the next couple of days and post it for you.

Manifold size maybe an issue as well as it has a 302 manifold on it and I am unsure of it's size.

The bypass shouldn't be causing an issue as it's either open or closed. That's the information I have been given by the supplier anyway. 

Thanks Scotty

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