AFR targets: Turbo vs. NA while pulling vacuum

98vtec · Post by **98vtec** » Mon Sep 15, 2008 11:39 pm

I'm curious to how everyone tunes their boosted setups while pulling vacuum. I dont see any reason why you cant run a target AFR like an NA motor on a boosted setup that is not creating boost. Can running mixtures like NA damage the turbo? I firmly believe that you can run a boosted motor like an NA motor as long as its pulling vacuum. Can anyone help confirm this for me? thanks

Post by **Gaskleppie** » Tue Sep 16, 2008 1:55 am

you can run NA AF mixtures in vacuum columns if you want. A lot of stock factory boosted cars run very lean mixtures at wot also, just for fuel economy. Only the high performance applications need to run richer. If you eez up a bit with timing you can run quit high AF numbers if you want without damaging your engine. I advise to check your plugs a lot when tuning like that thou....

Post by **calvin** » Tue Sep 16, 2008 10:56 am

I run NA afr into boost

Orthello · Post by **Orthello** » Tue Sep 16, 2008 1:08 pm

Frank... how lean is lean? I'm driving 100% open loop for a while now and like it a lot. (still N/A) But... now it's getting colder I see AFR are rising a bit. It's not much higher then 15.0:1 yet, but it will get past 15.5 maybe 16.0 when it gets really cold. What is the absolute minimum AFR while cruising a steady speed of say 140 km/u? With medium and maximum load it's still around 13.0 to 13.5 so now worry there. Only the cruising part.

Post by **Bugermass** » Tue Sep 16, 2008 2:26 pm

its ok to run leaner, in vac areas up to WOT reguardless if your turbo or not. If yoru AFRS are leaning with colder temps, you may want to adjust your IAT fuel tables to compensate for this. High 15s are ok, but 16-17 I think may be a bit too lean.. EDIT: I wouldn't do it with high compression engines, like 11.0 and up..

98vtec · Post by **98vtec** » Wed Sep 17, 2008 12:18 am

thanks guys

butch11a · Post by **butch11a** » Wed Sep 17, 2008 10:46 am

what a/f do you guys usually run at, say at 1.2bar full boost, mine is at 11.6 to 11.8 range on pump gas, was thinking of trying low 12's. my other car was running on high 12's to 13 a/f and it feels a bit stronger, but thats on a toyota with a steel block, don't know if my honda can handle lean mixtures under full boost...

Post by **Bugermass** » Sat Sep 20, 2008 12:13 pm

on pump gas I ususally stay in the 11.50 range for safety. You can run into the 12s and 90% of the time it'll be just fine, but I just like to have that extra cusion on stock pistons and pump gas.

Almighty-Si · Post by **Almighty-Si** » Sat Sep 20, 2008 1:40 pm

My A/F at highway speeds (65-75mph) is 14.2-13.9. Coming back to NY from my trip to North Carolina this passed summer I went 303 miles at just under a half a tank of gas. Had to stop to use the facilities and eat so thought might as well fill up and it took 7.1 gallons to fill the tank again. Calculating it when I got home, it equalled something like 42mpg

Pretty sweet, the only thing though, my EGT was a bit high...1300-1325 F, so if you're going to tune for gas mileage watch those. I'm going to get out on the highway with a friend and see if I can lower that a bit.