MAFT install, BACKFIRE AT 4400?

[3kgt2dsm]

ok so heres my setup,
big 16G @15lbs now
550cc injectors
wally 255 pump
maft blowthrough mode
3.5 mas
supra sidemount
disconnected safc (got the green/blue wire hooked back up properly)
new o2 sensor IS THERE A GROUND FOR THIS that i dont know about?
heres whats going on

af gauge is in the green the whole time im on it untill i get up to 4-45oo rpm then the gauge PINS lean and the car backfires like a bastard
big black puff

it runs mint up till 4500
i got my MAFT settings at 4 0 2 and 3 and it still leans out at upper R's
anyone got an idea what the hell is going on? any help is appreciated.

 

[Mike Licht]

What are you using for a logger and what do your fuel trims look like? You likely need to add fuel in the base. What is your fuel pressure?
Mike

 

[3kgt2dsm]

mike, i dont have a clue what the fuel pressure is. its a 255 that isnt rewired.

im not logging at all, i have the blue wire mod on the safc. thats about it. i know before i get flamed, i should have these things. i got the palm. i just dont have the software yet.

i unplugged the 02 sensor and it seemed to run a little bit better up top. usually you can feel the timing pull when the sensor is pluged in. i may have found the problem.

mike, does the car have to be ON when you turn the knobs? or will it not recognize the change?

 

[Mike Licht]

Doesn't matter if the car is running or not. The "blue wire mod" has been know to cause problems. Disconnect that and hook up the O2. add some fuel
Mike

 

[Benji]

Originally posted by Mike Licht
Doesn't matter if the car is running or not. The "blue wire mod" has been know to cause problems. Disconnect that and hook up the O2. add some fuel
Mike

I am not sure about adding fuel! According to his mod list he has a 255LPH Pump but no FPR ... *hint*

I could be wrong though!

 

[3kgt2dsm]

i dunno about the fpr. i know cars that are running 11.70s with NO fpr and a wally 255. i DOUBT thats the problem

 

[Mike Licht]

That might be true but those same cars might be quite a bit faster with an adjuable reg, a fuel system that is in control and a better tune up. No flame, just opinion.
MIke

 

[3kgt2dsm]

oh for sure, he got one for the 11.70s car, just waiting to get her all back together, he had an 8count for timing, at the desired 30.......... well, 10 second car all day.

anyway. my fuel pump is ASTRONOMICALY loud, like it drowns out the exhaust its so loud. anyone think thats got anything to do with it?

i hooked up the o2 sensor, which im being told is most likely the wrong part for the car as there were 4 different part numbers for first gens. will this effect anything?

and i disconnected the blue wire, its not any different. im frustrated as HELL right now, it cant be the rpm wire for the MAFT, could be the o2, could be fuel delivery (more than likely) BUT is it the pump or the injectors? how to test?

anymore help will be appreciated.

btw, where can i get a cheap fpr that i can bolt up to the stock rail?

 

[jake98gst]

Originally posted by 3kgt2dsm
btw, where can i get a cheap fpr that i can bolt up to the stock rail?

B&M racing....afpr for like 75 bucks i think...check:
extremeturbo.com
machv.com
dsmotorsport.com
etc.

 

[3kgt2dsm]

i think whats going on is im over runing my stock fpr.
i have been doing research. im running 15lbs and have a 255lph with the stock fpr.
i think i found the problem. what are your thoughts.

 

[3kgt2dsm]

how bout this theory, the 255 raises base pressure right? so if im running 15lbs with 550cc injectors and the fuel pump is making them work harder already from the get go. my duty cycles must be hitting 100% at 4500 rpm. they just cant flow anymore gas? what do you guys think on that?

 

[hostile]

To get a backfire, you need to have a rich condition. Your either have a boost leak, a exhuast leak, or something wrong where your running too rich.

I would check your o2 sensor on a datalogger.

I would also reccomend the AFPR. There are many wrong ways of doing things that will work, but there are only one right way to do things.

Having a fuel pressure regulator with a large pump is just one of thoose things you gotta do if you want it to be 100% right.

Sure you can try and tune around weird fuel delivery, or you can regulate the fuel pressure and tune normal.

 

[3kgt2dsm]

its more of a lean back fire, the gauge pins lean at 4500 rpm and i get fuel cut, thats what i was thinking the back firing was. its lean not rich.
thanks guys, what else do you all think?

 

[hostile]

Well then your getting fuel cut, and not getting a backfire. Backfire is cause by unburnt fuel.

What you having is fuel cut which could happen if you dont have the maft setup right or your just plain running out of injector for the airflow you have.

 

[hostile]

Well then your getting fuel cut, and not getting a backfire. Backfire is cause by unburnt fuel.

What you having is fuel cut which could happen if you dont have the maft setup right or your just plain running out of injector for the airflow you have.

 

[3kgt2dsm]

hmm, i got the 3.5 sensor, 550injectors and 15lbs right now and its still cutting at 4500. what should i check? the o2 sensor perhaps?

 

[kpt4321]

Oh boy, this is going to take a while.

1. The O2 sensor does not effect WOT performance, that is not the problem.

2. Disconnect the blue wire mod. It sucks.

3. What are the percentage corrections on your MAFT? With the 550's, start out by putting the base knob at "4" and leaving the rest at zero.

4. This sounds a lot like a misfire to me. How voilent is it? If you have a misfire, the A/F gauge will drop to lean because of excessive oxygen in the exhaust. The O2 sensor (A/F gauge) measures oxygen content, not overall A/F mixture.

5. The B&M FPR is NOT what you want. It only attaches to the stock FPR and lets you turn the fuel pressure up. You need something with a larger return hole, such as an Aeromotive or SX FPR, or the Buschur one.

6. While an AFPR probably is a good idea for you, any FPR overrun yuou might have will not really cause anything under the conditons you describe. They are really only a problem at idle.

....Kyle T.

 

[3kgt2dsm]

im getting fuel cut, thats what its gotta be, i found out i DO infact have the wrong o2 sensor in there so any af reading is inaccurate,

my settings on the MAFT are 4 0 1 2

anyhelp there is appreciated

 

[Mike 99GSX]

Originally posted by 3kgt2dsm
im getting fuel cut, thats what its gotta be, i found out i DO infact have the wrong o2 sensor in there so any af reading is inaccurate,

my settings on the MAFT are 4 0 1 2

anyhelp there is appreciated

The O2 sensor has nothing to do with the cars performance at WOT just like kyle T said! You should do a boost leek test. What plugs are you running. BPR7ES? Check your plugs and wires. It sounds like a boost leek.

 

[3kgt2dsm]

where are some places a boost leak can occour to cause this? if its after the mas, its in blow through setup, everything is tight. the onlything i can think of is the coolant holes in the TB arent plugged i bypassed the coolant to the tb but havent plugged off the lines there, are there any other places too look? im out of ideas. btw im thinkin this is just fuel cut.

 

[3kgt2dsm]

good news! i found the solution to the problem. remember how i mentioned theat the fuel pump was really loud?

progressivley the situation was getting worse in regards to the car leaning out at specific rpms, was 4500 now 3300?

well i went and took the walbro out of the car and to my dismay the fuel pickup was BLACK! i mean so bad that when i put it under a faucet, no water would travel through it. im surprised that the car even ran at all.

i also got a new o2 sensor in the car today (the proper part number) and all is WELL, the car pulls like ive never felt before.

just a heads up to anyone who has an ABNORMAL loud fuel pump. check the pickup.

 

[jake98gst]

was it just installed wrong? or how did the pickup go bad?

 

[3kgt2dsm]

pickup (filter thingy) went bad, tons of shit floating around in my gas tank, i need a new one bad.
lots of rust.

 

[nine5raptor]

usually we call that pre-pump filter the strainer. And yeah, if you actually clogged it up, you need to get a new tank pretty bad. How many miles on the car and did it ever sit in water or without any gas in it for a while?

 

[3kgt2dsm]

yea its pretty hosed, i need a tank all kinds of bad