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Discussion Starter · #1 ·
Here is my current setup. I am having a problem running lean from max boost(4000rpm) on up. Anyways, I belive it is lean, the shady autometer A/F guage reads red when i feel the car "chug". However, when i richen the fuel to rediculous amounts it does nothing to fix it. In otherwords it still chugs. I have tried every setting on the VAFC from -15 to -40% with out success. Is it possibly the fuel filter? Im in a rut because i would like to get this poor thing tuned but I am afraid I will waist a trip if it can not be tuned in the first place. Any suggestions whatsoever will be appreciated guys. Thanks.

edit: I am using dsm 450's with my setup. Also, this all of a sudden started happening. It WAS running fine for awhile...shrug
 

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there have been some posts here talkin bout the dsm 450's, i am not sure exactly what the answer is but search aroudn because if i remember right someone else said they were running lean and figured the dsm 450's were the issue
 

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What is your base fuel pressure and timing set at? Also with the 450's you should have a resistor box wired in because they are peak and hold.

You also said that you have been running this setup for awhile. How long? Maybe the weather has changed and you need to setup everything to run with the current weather. This can be a big problem with the AFC and bigger injectors.
 

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Discussion Starter · #4 ·
it is stock fuel pressure and timing. It is a good idea to get a fuel pressure guage though. I used the radio shack resistors 20ohm. The weather has changed somewhat but not to bad. It runs with out 'bucking' if i turn the boost down to .45 bar however so it seems i just cant seem to get the fuel to it. I dunno, im so confused
, i want to tune the poor baby hehe
 

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you're problem is that you're using a narrowband (read: useless) A/F reading and the ass-dyno to tune a turbo car.

Throw it on a dyno with a wideband before it pings and snaps a rod in half.
 

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Discussion Starter · #6 ·
br1t1shguy i agree, the damn thing is useless. It's a worthless piece, however, i can not enrichen the fuel one way or another so it would be pointless to try to tune it correct? Unless i am mistaken about something. However I find it hard to belive that the VAFC with 450cc injectors set to -10% today was not enough fuel. But since i respect your advice, if you say so, ill go to Bermingham and try to tune it.
 

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br1t1shguy on Feb/17/04 said:
you're problem is that you're using a narrowband (read: useless) A/F reading and the ass-dyno to tune a turbo car.

Throw it on a dyno with a wideband before it pings and snaps a rod in half.
this is what i was going to say.
you say you don't want to waste a trip to get it tuned, because they may not be able to. why would they not be able to tune it? they can tune the afc, and teh fuel pressure.
 

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Discussion Starter · #8 ·
the problem is the VAFC is not, or can not enrichen the fuel enough past a cirten point. I would like to know why, its not that the VAFC is not enrichening, when idleing i can stall the car out with fuel... however when ever i hit max boost ~4000 rpm and 8psi, it starts bogging while the crappy A/F meter reads lean. So, if the VAFC cant richen up the fuel mixture above above a cirten volume, then it seems like something is impending the fuel flow. What could it be??? fuel filter? bad injectors? crap in the fuel line? worn out fuel pump? unless it is something entirely unrelated...
 

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since the air fuel meter is useless you could very well be putting too much fuel into the car, and that may be causing it to bog. you will need to make sure your wiring is done right with the injectors also. if you have not had it tuned, you should do that befor you do anything else. i am positive that tuning will make your car run right
 

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I just had a thought. Maybe your ecu is seeing boost. Therefore your ecu goes into limp mode and the engine runs like ass. Do you have a missing link or check valves in place? If you go past I think it is -35% then the MAP sensor voltage will read over 3V with the 440's causing your ecu to see positive pressure. Which is not a good thing.
 

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Quote: I just had a thought. Maybe your ecu is seeing boost. Therefore your ecu goes into limp mode and the engine runs like ass. Do you have a missing link or check valves in place? If you go past I think it is -35% then the MAP sensor voltage will read over 3V with the 440's causing your ecu to see positive pressure. Which is not a good thing. [/quote]
that's where i'd start looking.

also, you said you are using 20 ohm resistors from radio shack, correct? if so, this means you are trying to drive injectors that are meant to be driven with between 1 and 5 amps with a mere 500mA. the main reason larger injectors are peak and hold style is because the armature weighs more and takes more power to open quickly. you're using half that power if you're running 20 ohm resistors (I=V/R) and chances are you are losing fuel delivery because your injectors are taking much longer to open, while closing at the same time. this could be a significant portion of your injector's open time.

the first thing i would do is get rid of those 20ohm resistors. replace them with 10 ohm.
 

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to add to that, during opening is when injectors have the worst spray pattern. you want them to open as quickly as possible. the longer it takes them to open, the less atomized your fuel mixture is and the easier it will drop out of suspension before it makes it to the combustion chamber. for all we know, you may be delivering all the fuel necessary, but the spray pattern is so bad that only 80% of it is actually burning in the combustion chambers. it astonishes me that no one has developed a peak and hold conversion driver for the 450's yet. maybe i'll have to do it..

anyway, i would change the resistors before you even drive it again, much less before you dyno it. i guarantee they are compromising your driveability in some way. i would swap them before you hit the dyno, it's one less thing to throw off the tune/investigate.
 

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Discussion Starter · #14 ·
I checked on the resistors and i just remembered it wrong. I have 10watt 10ohm's installed. Damn. As for the VAFC settings, i did have the narrow throttle settings when idleing set to -27 percent or so... i was playing around with it to smooth out the idle. Its now set to -35%. Ill test it out after the wife gets of my back
And thanks for all the help guys, I really appreciate it. I just wish i could get this thing running well.

on a side note it may be unrelated but ya never know. When holding the throttle at a steady point, say 20%, the rpms climb and fall instead of holding steady.
 
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