Adjusting tune for added boost?

justinschmidt1 · Oct 23, 2008

How would you adjust the tune for a couple psi more boost?

Ive heard that pulling some timing and adding some fuel will do the job?

Im wondering because im running like 10 psi.

If I added a boost pipe I might add 1-2 psi and I dont really want to pay for a re tune.

Would it be OK to just go in with the sct and remove a couple degrees of timing and add some fuel?

04YELLOWGT · Oct 23, 2008

You pretty much need to check the A/F if you add boost. I would rather spend $150 for a retune than spend few grand for a rebuild.

justinschmidt1 · Oct 23, 2008

I understand that...but my car is already tuned to be at like 11.4 a/f with 10 psi.

All my tuner would do is bump the fuel up and maybe remove some timing and make sure the a/f is good.

Im just wondering how much of a differance 1 psi makes.

Would I need like 5% more fuel or 10% more fuel to keep the same a.f?

Of course its best to take it to a tuner but it seems like a waste if all I need to do is add 5% more fuel at wot.

tag4car · Oct 23, 2008

good thread, i'm wondering the same things

Mikie · Oct 23, 2008

Do you have access to a wide band?

That is really the only way to know. You could just do the pipe and pay your tuner $50 or so to just pull the car with the sniffer in the tail pipe to let you know.

04YELLOWGT · Oct 24, 2008

I know I picked up about 2lbs with my MPH Boost pipe. When I called Tim at MPH I told him I was buying the pipe and he told me to send him my tuner so he could load up a tune for the pipe. He did it for free so I guess he thought the tune needed tweaked or he wouldn't have told me to send it back.

justinschmidt1 · Oct 24, 2008

04YELLOWGT said:
I know I picked up about 2lbs with my MPH Boost pipe. When I called Tim at MPH I told him I was buying the pipe and he told me to send him my tuner so he could load up a tune for the pipe. He did it for free so I guess he thought the tune needed tweaked or he wouldn't have told me to send it back.

Yea, the tune needs to be tweaked but its not like a new tune...they just add a bit more fuel and maybe take some timing out

Don 95Vert · Oct 24, 2008

If it was tuned properly, you should be fine with added boost the way it is. Properly means tuned to calibrate the MAF curve so it is accurate and tuned with the spark curve properly normalized. If these things were done, then the MAF will sense more air automatically and the A/F ratio should remain fine. If it was tuned with fuel 'adders' then all bets are off. If the spark curve was properly normalized, then as boost goes up, calculated engine load also goes up and in most cases, timing advance goes down. Without anyone having to retune anything. There are a couple of 'gotchas' and they are, you have to make sure the MAF is not pegging with the added boost, the fuel pump is still able to deliver and you are not running out of injector. Now if it were my car, I'd get it on the dyno just to datalog those things to be sure it was done right and I was not running out of any critical things. Sometimes with added boost it is also required that the spark plug gap be a bit less too.

Hope this helps.

Don

justinschmidt1 · Oct 24, 2008

Don 95Vert said:
If it was tuned properly, you should be fine with added boost the way it is. Properly means tuned to calibrate the MAF curve so it is accurate and tuned with the spark curve properly normalized. If these things were done, then the MAF will sense more air automatically and the A/F ratio should remain fine. If it was tuned with fuel 'adders' then all bets are off. If the spark curve was properly normalized, then as boost goes up, calculated engine load also goes up and in most cases, timing advance goes down. Without anyone having to retune anything. There are a couple of 'gotchas' and they are, you have to make sure the MAF is not pegging with the added boost, the fuel pump is still able to deliver and you are not running out of injector. Now if it were my car, I'd get it on the dyno just to datalog those things to be sure it was done right and I was not running out of any critical things. Sometimes with added boost it is also required that the spark plug gap be a bit less too.

Hope this helps.

Don

Thanks...I honestly dont know if it would considiring its on an extender and is close to pegging as it is.

Adjusting tune for added boost?

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