d15b7

hello all; hope this is the correct forum for this question! i recently aquired a 2003 EVO (my new daily driver), and in two weeks will be taking it to a Drivers Ed event with the PCA (i am an instructor for the PCA, BMW CCA, Ferrari Club, etc.). i wasn't planning on ever taking it to a road track (i have 3 other dedicated race cars) but is feels sooooo good on the street, i just have to take it to a track and see what she'll do!

its all stock, with the exception of the following:
- rear muffler delete (straight pipe)
- r-nr downpipe & cat delete

thats it; no boost control (all stock controlled by the computer, which is fine with me!). safety first!

i just finished wiring in a HKS Super AFR; it is set right now to all zeros.

i have a wideband O2 meter that i can tune it on.

i've done alot of reading on the subject, and understand that the EVO stock runs very rich, especially in the higher rpms. like 10:1 rich.....

for my naturally aspirated cars, i usually tune them to 12.3-12.8:1. i realize this is not rich enough for safety in a turbo car like the EVO. i have been reading posts that say tune to 11.5:1; but i am not sure if this is for a drag car that is doing a 12 second burst, or a street car driving to work..... i will be doing 25 minute sessions of HARD HARD running; don't want any engine damage!

we get good 93 octane gas around here (east coast). what air fuel ratio should i shoot for, guys?

thank you for your insights!

todd
d15b7@aol.com

992gnt

iTrader: (5)

I'll be interested to hear what others have to say on this subject, but I wbo2 tuned my Evo at the dragstrip to 11.7:1. There is power to be had by leaning it out a bit more, but I don't like to chance it. I have driven two DE's with it running 93 octane and the same tune with no troubles. I have just permanently installed my wbo2 display so I'll be able to peek at it once in a while while on track. BTW, I am not an "A" level driver, yet.

shiv@vishnu

iTrader: (20)

Hard question to answer since a lot depends on o2 sensor type, placement, gasoline type, boost levels, conditions, etc,. But our One Lap car, for instance, has been known to run in the 10:1 to 11:1 range on the track running c16 at 25-28psi of boost. This is read from an LSM11 o2 sensor and interpreted by an Autronic wideband module. Leaning it out is certainly good for more power (40-50whp to be exact) but I'd be more worried about long term motor integrity. This is the difference between tuning a drag car, which only runs for seconds at a time, and a road racer that needs to be thermally stable lap after lap after lap.

regards,
shiv

d15b7

thanx for the info, shiv! and hearty congratulations on your recent victory!

boost level is stock (spike to 19 psi and tapers down to about 16-17 psi). wide band o2 meter is the Innovative motorsports LM-1, with the wideband o2 sensor screwed into the secondary o2 port.

sounds like you think that i should probably not go any leaner than 11:1, i guess?

thanx again.

todd

shiv@vishnu

iTrader: (20)

what gas octane?

shiv

d15b7

here on the east coast, we get 93 octane. sunoco carries Ultra 94 octane at all its stations, too. i generally buy 93 octane, as there is a Texaco right down the street from my house, and it is 93 octane...

shiv@vishnu

iTrader: (20)

If you're goning to be doing sustained track driving with your car, and will run on 93 octane only, no reason to run leaner than ~11:1 to 11:5 under boost. However, this will leave a bit of power on the table when you drive around on the street. In this case, you might want to still shoot for ~11.5:1 to 12:1 while adding in a few gallons of race gas to your tank. The few extra octane points will keep the car knock free and consistent lap after lap. Howevever, these numbers refect a car which have modified timing maps. If you're running a fuel-only computer, don't be surprised if you have to run a lot richer or will a lot more race gas to keep the car knock-free. This is where ignition timing changes come in very handy and are very important for long-term safety margin and consistency.

Just my 2c,
shiv