Defined Autoworks Header Install!

NoDOHC · 01-02-2012, 12:11 AM

That is a good question, I compared fuel maps and I only added about 12% to the fuel to get it back, so I am guessing that the engine was misfiring. I have trouble keeping the AFR constant at 1800, 2400, 3600 and 7200 RPM. The AFR moves between 13.2:1 and 15.2:1 right now at 7200 rpm, I had to put a filter in the E8 for the MAP sensor, as it was seeing 5 kPA boost at 7200 (the MAP was jumping around about 10kPA).

This is the effect that I was not expecting. The headers dramatically change the VE, I had to move my RPM points around to fix a newly acquired '3600 rpm hesitation' which results from the MAP reading being very unstable at this speed. The VE peak (about 5%) is very narrow, as I need a 3550, 3600 and 3650 rpm point in my map. I was able to get around the 1800 and 2400 peak by just letting the engine go lean there, but the 3600 rpm VE peak was actually causing a misfire.

I may have to revisit the 2400 rpm MAP dance later, as it becomes a little problem when I am trying to cruise at 60 MPH (I usually don't drive 60 mph, but I was in traffic at that speed yesterday and there are still some driveability issues at that speed).

I haven't gotten to the dyno, so the 7200 rpm point is still running 'close' I can't tune that spot on the street, as it revs way too fast in second gear to do anything and I would be going > 100 MPH in 3rd.

The 5,500 rpm point is very weird, as I get misfires there even now, but my AFR is good above and below this point. I really need to get to the dyno, as even 5,500 rpm is a little fast for street tuning, although this could possibly be done in 3rd gear.

EDIT: With the minimal overlap this engine has, I thought that a MAP tune would be ok, now it is looking like a TPS tune may be the best solution again. (I hate TPS tunes because they are so temperamental.)

j9fd3s · 01-12-2012, 03:13 PM

hmm i don't really like MAP tunes on NA engines, it seems like cruise and idle are always the same spot! the last car i did though was a 56 chevy so it doesn't rev over 2000rpm until about 50mph!

i've actually thought about running some sort of air flow meter next time, a modern one, like an Rx8 or something, it SEEMS like it might be a little simpler to tune.

-mike

01-02-2012, 12:11 AM	#1
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 18	That is a good question, I compared fuel maps and I only added about 12% to the fuel to get it back, so I am guessing that the engine was misfiring. I have trouble keeping the AFR constant at 1800, 2400, 3600 and 7200 RPM. The AFR moves between 13.2:1 and 15.2:1 right now at 7200 rpm, I had to put a filter in the E8 for the MAP sensor, as it was seeing 5 kPA boost at 7200 (the MAP was jumping around about 10kPA). This is the effect that I was not expecting. The headers dramatically change the VE, I had to move my RPM points around to fix a newly acquired '3600 rpm hesitation' which results from the MAP reading being very unstable at this speed. The VE peak (about 5%) is very narrow, as I need a 3550, 3600 and 3650 rpm point in my map. I was able to get around the 1800 and 2400 peak by just letting the engine go lean there, but the 3600 rpm VE peak was actually causing a misfire. I may have to revisit the 2400 rpm MAP dance later, as it becomes a little problem when I am trying to cruise at 60 MPH (I usually don't drive 60 mph, but I was in traffic at that speed yesterday and there are still some driveability issues at that speed). I haven't gotten to the dyno, so the 7200 rpm point is still running 'close' I can't tune that spot on the street, as it revs way too fast in second gear to do anything and I would be going > 100 MPH in 3rd. The 5,500 rpm point is very weird, as I get misfires there even now, but my AFR is good above and below this point. I really need to get to the dyno, as even 5,500 rpm is a little fast for street tuning, although this could possibly be done in 3rd gear. EDIT: With the minimal overlap this engine has, I thought that a MAP tune would be ok, now it is looking like a TPS tune may be the best solution again. (I hate TPS tunes because they are so temperamental.) __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic) Last edited by NoDOHC; 01-02-2012 at 12:15 AM.

01-12-2012, 03:13 PM	#2
j9fd3s Rotary Fanatic Join Date: Mar 2008 Posts: 123 Rep Power: 18	hmm i don't really like MAP tunes on NA engines, it seems like cruise and idle are always the same spot! the last car i did though was a 56 chevy so it doesn't rev over 2000rpm until about 50mph! i've actually thought about running some sort of air flow meter next time, a modern one, like an Rx8 or something, it SEEMS like it might be a little simpler to tune. -mike