510 Inj./Hacked MAF

[4G63dsmpwr]

I have 510s and I was wondering how much more they flow then 450s? Is it 13% more? Just checking the math. And my MAF has the entire lower section removed (not just the honeycomb). Does anyone have any idea how much more (%-wise) this would allow into the engine. B/c I'm trying to figure if I had a totally stock setup I would be running approx. -13 accross the AFC right? Now with the Hacked MAF (lets say it allowed 20% more ait into the engine) Then +7 would be a good starting point and fine tune from there. B/c I'm running like +38 @ 18lbs of boost on my high-throttle maps and it seems like I'm dumping a lot of fuel. I'm not sure if this even makes ANY sense lol - Erick

[4G63dsmpwr]

Any ideas anyone???

[pneumo]

The hacked MAF flows 25% more uncounted air than stock. Hacking the MAF also changes the airflow profile, and make it count air non-linearly. The MAF will count much less air at idle than at WOT. So you need to richen it more at low airflow settings. For example my AFC settings on my hacked maf at low throttle start at +43 at 1000 rpm, +12 @2000, +4% @3000, then the rest at +3%. High throttle settings go from -3 (negative) @1000 rpm up to +18 @ 7000 going almost in a line up the bar graph. I'm offering this to give you an idea of the correction CURVES! Not the actual NUMBERS. (I'm not telling what size injectors and fuel pressure I run ) All cars are different. Make sure you have the correct gages to monitor the engine so you don't blow it up. Have Fun!

[4G63dsmpwr]

If the MAF flows 25% more air, and my 510s dump 13% more fuel then roughly my Hi-Throttle maps should be at +12 (for stock 11lbs of boost?)? The reason I ask is beacause my Hi-Throttle maps are averaging +38 which is tons of fuel and I'm wondering if there is something wrong or this is just the way its gonne be. Thanks

[Silent2g]

first. all fuel systems and ecu's are different {had to change it}

i ran a mas with a lower section removed. 510 inj's. stock fuel pump w/rewire.
running 16 psi. the o2's never dropped below .90 knock at 0 {from a 25 mph rollon in second gear to 4th gear}

i personally think the best thing to do is get a logger. or borrow someones for a day or so to get the car set up right.

i personally don't see why you are dumping +13 in fuel on stock boost. but thats just me

[4G63dsmpwr]

See thats the thing, I did get a logger and at WOT my 02s are .90. With 0-5 knock sums, so I don't get it b/c +38 is A LOT of fuel and it seems to be running right.. But everyone says that its too much fuel. I was wonderng if there might be a problem causing this?

[4pistons]

If you're using a logger back the fuel settings down in small increments until the knock starts coming up and your timing goes down. Use the O2 as a reference but don't depend on them only. Your timing, knock and EGTs are better benchmarks for tuning.

Rick - '91 GSX

[4G63dsmpwr]

Ok well I don't have an EGT guage yet, so should I just keep dropping the Hi-Throttle settings by 1% until I see some knock and less timing?

[BatmanGSX]

Originally posted by pneumo
The hacked MAF flows 25% more uncounted air than stock. Hacking the MAF also changes the airflow profile, and make it count air non-linearly. The MAF will count much less air at idle than at WOT. So you need to richen it more at low airflow settings. For example my AFC settings on my hacked maf at low throttle start at +43 at 1000 rpm, +12 @2000, +4% @3000, then the rest at +3%. High throttle settings go from -3 (negative) @1000 rpm up to +18 @ 7000 going almost in a line up the bar graph. I'm offering this to give you an idea of the correction CURVES! Not the actual NUMBERS. (I'm not telling what size injectors and fuel pressure I run ) All cars are different. Make sure you have the correct gages to monitor the engine so you don't blow it up. Have Fun!

That's an excellent answer. Most people don't grasp that the change is nonlinear. These are the people that think you can run a 2G MAS/hacked MAS, 550s and no AFC.