Race gas tuning question.

[davidm_sh]

Hey I was wondering if I could get some pointers on tuning for race gas (104 unleaded vs. my 91 pump gas map).

I was thinking about leaning things from 11.5:1 to 12-12.5:1 range and maybe adding 1-2 degrees of timing? Should I leave the A/F alone and just add timing or maybe just lean it out and not touch the timing or both?

Just to give some point of reference I am thinking about running 21-22psi. Right now I can run about 20.5psi (from 4400-4600rpm and then the boost drops off to 18ish psi by redline) on 91 octane pump gas with no detonation on my current map.

Thanks in advance.

12's will be mine this Wednsday .. OH YES 12's will be mine :).

[Brian]

Just for reference i'm told that the only changes the vw chip makers make between 91 and race gas is more timing... There is a supposedly something like a 30 hp difference between the two as well.

[john]

You will get more power out of race fuel than pump gas at any given boost level, say, 20psi.

Do you have a datalogger of some sort? How do you add timing on your motor - is it mechanical or electrical? Timing is always your friend, and if you can get away with adding a few degrees and NOT have the ECU pull it out on the big end, more power to you.

104 is a great choice. I can run 28psi on 104 with the big turbo. Is that 21-22 psi all the turbo can make? If so, then you are probably going to have timing pulled out due to high intake charge temps, due to the turbo working so hard to make 21-22 psi. Do you have a FMIC, or big SMIC?

You may be better off backing off the boost just a bit and adding a couple degrees of timing - just for a comparison.

[Brian]

john I believe he has an air/water intercooler.

[davidm_sh]

Originally posted by john
You will get more power out of race fuel than pump gas at any given boost level, say, 20psi.

Do you have a datalogger of some sort? How do you add timing on your motor - is it mechanical or electrical? Timing is always your friend, and if you can get away with adding a few degrees and NOT have the ECU pull it out on the big end, more power to you.

104 is a great choice. I can run 28psi on 104 with the big turbo. Is that 21-22 psi all the turbo can make? If so, then you are probably going to have timing pulled out due to high intake charge temps, due to the turbo working so hard to make 21-22 psi. Do you have a FMIC, or big SMIC?

You may be better off backing off the boost just a bit and adding a couple degrees of timing - just for a comparison.

Ahhh I used to worry about things like that with the stock ECU ;). Here is the setup I have. I have a standalone ECU (Link ECU) so I can adjust the timing and fuel all that I want to. I still have knock detection and it will pull timing a bit if it starts knocking but I also have a "knock" gauge in the car as well.

The only problem is that I think the turbo is working it's arse off running that kind of boost. Although the boost taper seems to be a fixed amount of taper and not a absolute amount; meaning when I peak at 1.4bar by redline it will be about 1.3bar and if I peak at 1.3 bar it will be at 1.2bar by redline.

I also have a air-to-water intercooler which so far is the MAIN reason i can get away with running 20psi last night IMHO.

I know some guys up in Denver with big FMIC and similar setups as mine and I am honestly just not impressed with them. They add about 300-500rpms of lag and when they do get full boost it honestly doesn't feel any faster than Jay or I's car. In fact they feel a tad slower :)... but then again they only run high 13's too [heh].

So now that you know all that what would you suggest. Personally right now I think I am going to add a few degrees of timing right around the midrange (peak torque) and lean things out just a bit in the same area 11:1 to about 12:1.

[john]

Cool. Leaning out from 11:1 to 12:1 will make a pretty significant difference, AFAIK.

[newt2]

I'd go for timing advance before adjusting fuel but really the best is to optimize both and save the map as a seperate file for when you run race gas.


I'm assuming the link ecu has much of the same capabilities as my AEM EMS right?

[Brian]

I concur, I think most of your gains will be from the timing so get that handled first then lean the fuel map out for some added power.