Apexi AFC, Air Flow Converter

i165mk

New Member
Mar 31, 2007
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FLushing Queens
would i be ok running a walbro 255 with that? or what about a stock fuel pump would i benifit anything from running the Apexi AFC, Air Flow Converter or would i be just running tooo lean
 

suprahero

naughty by nature
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Aug 26, 2005
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Roll Tide
Just because you have the AFC doesn't mean your going to run lean. You don't need a Walbro 255 with stock injectors either though. Have you replaced your stock injectors with larger ones?
 

i165mk

New Member
Mar 31, 2007
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FLushing Queens
nope but inventually i wil. just wondering if it could help me in anyway stock injectors rebuilt motor portandpolish and apexi intake + apexi exhaust
 

TobyCat

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Jul 14, 2006
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Vancouver BC
I wouldn't put a walbro in until you have a new fuel pressure regulator. Stocker may complain :( There is no point without new injectors that require that kind of volume.

I think you're mistaken on what the SAFC does. It basically intercepts the AFM signal, adjusts, and sends to the ECU. This way, you can either richen/lean your mixture. My car with stock fuel, and after market intake/exhaust saw a ~22HP/20tq improvement just from tuning with the SAFC.

Be careful though, if you don't know what you're doing then you can cause serious damage to your car by screwing around with it. I went down to a local dyno and paid to have somebody with experience tune my precious ;)
 

i165mk

New Member
Mar 31, 2007
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FLushing Queens
could i be able to run that with stock fuel and stock injectors. looking for some tunning to be done. just wondering if that was a good airflowcomp to run on my car. would it be better to run that or dont get it ?
 

TobyCat

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Jul 14, 2006
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Well it all depends on what you're planning on doing with the car. Lots of people are ditching the SAFC to go with the Maft-pro. It doubles as a tuning piggy back and also a boost controller. I don't know a whole lot about how they work but there are some pretty comprehensive write-ups here in the Tech sections.

For me, I don't plan on going much past 12psi boost @ 310hp. It's done the job for me, I got some good gains to warrant keeping it so I'd recommend it to anybody looking at just tweaking their A/F for modest gains. You can pick them up here quite regularly from people going to maft-pro setups and they usually go for ~$200.

Now for the fuel upgrades, you really need to know why you want to upgrade your fuel pump before you just go ahead and do it. Simply dropping in a walbro without doing the proper preparations will lead to absolutely no 'tweakability' and will most likely cause problems elsewhere.

So let's start from the beginning. The only reason to upgrade your injectors is because you are running higher boost. The stock 440s are fine for me @ 12psi, and I'm still running slightly rich. If you plan on upgrading your turbo to go beyond that then that's generally when people will also upgrade their fuel system. And that's what you'll here a lot around here. "...upgraded XXX turbo with supporting mods..."

This in most cases are: 550cc (or higher) injectors, adjustable fuel pressure regulator, upgraded fuel pump, bypassed/drilled out J-tube. This will allow you to provide 'nuff fuel for most upgraded CT26s @ moderate boost. Example fuel calculations were done recently by Supracentral and I think is now stickied in the 7MGTE tech section.

At higher boost with stock AFM, you'll hit fuel cut at ~13psi (at least I did). It depends slightly on air temp, altitude, car etc. But that's a general idea where you'll need to ditch the AFM or get around it somehow. The 'traditional' way of getting around this was to run a Lexus V8 AFM. The only difference between ours and the Lex is the size, thus allowing more air to enter the turbo. You old electronics can be used. This is where you will definitely need some sort of tuning capability as you now have a car that has no idea what to do with these parts (fuel upgrades, Lex AFM, higher boost). The old way (archaic) was to use an adjustment screw on the side of the AFM to limit the amount of air in. This was replaced with the SAFC which tricks the ECU into responding with a certain amount of fuel by telling it how much air is coming in. The most recent and best trend is to ditch the AFM and go maft-pro. This replaces the AFM with a MAF from GM (I think?) cars. This method is the best from a piggy back standpoint (IMO) as it allows a far greater amount of tuning than the SAFC does.

So, in short you need to decide what your goals are with the car. If you plan on upgrading your turbo then you'll need to choose a route to go with. In either case, you'll need:

Upgraded Injectors (how big depends on how high of boost you want)
Upgraded fuel pump (how much flow depends on which injectors you choose)
Fuel pressure regulator (The Aeromotive one seems to be a common choice)
Fuel pressure gauge (need to see what the fuel pressure is while tuning!)

Then the electronics as described above:
Either
A) SAFC/Lexus AFM upgrade
or
B) MAFT-pro kit
or
C).........Z) there are quite a few other options you could read about.

So in short, read read read then decide from there.

Hope this wasn't too lengthy,
-Chris