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Full Version: A:F ratio using my stock GT fuel pump for my gen4 swap
6G Celicas Forums > 6th Generation Celica > Forced Induction
ILoveMySilly97
There's people saying all over the internet that the GT fuel pump will run lean for a 3sgte swap and a 255lp swap is required. Will I've been driving mine around for a month now around 700 miles. So far I'm fine. Punched it here and there. Here's a link to my video of my car WOT in 4th gear. You can see the A:F ratio yourself.

https://www.youtube.com/watch?v=TtUUGGkV6KU
Ryouxrs
That video almost makes me wonder if somethings is off with my car now.... I have cams and no tune though so that may be my issue. My swap is running a 255 pump and your a/f looks the same as mine besides at idle. We may also have strange data differences because I'm at 5,000ft elevation vs you being at sea level. I'm at 14-15 at idle instead of 16 like yours. But besides that in hard boost I'm at 10 flat aswell. I say keep it just like it is.
ILoveMySilly97
At idle when it's warmed up. It'll be at 15ish.
lagos
The pump is sufficient for 10 psi, but might not be able to supply the fuel required at higher boost levels. Turn the boost up to 15 psi and see how it does.
Ryouxrs
Lagos has a point, I'm running 18psi in 4th gear with those a/f numbers. It's worth a shot, factory boost settings where 14-15 psi stock on my swap.
ILoveMySilly97
Yea. Ima make another video with 12psi and 14psi.
Starlet119
Get a 255 pump and turn the boost up to 20 psi.
presure2
i dont understand the hesitation to install the fuel pump ken. it takes less than an hr, is super easy to install.
just google mr2 fuel pump test to see proven #s, to how the stock pump (even the turbo pump) gets weaker as you turn up the boost, because of the elevated pressure.
every psi of boost adds 1 psi to your fuel pressure. so @ 15psi, the pump thats been running for 20 years @ 36psi or whatever stock pressure is, is now @ 51psi, and struggling to keep up with flow demands.
you already said that it was leaener when you were running higher boost before, that just proves what ive been telling you on facebook.


also, just because its hitting 10:1 now, doesnt mean its safe either. if that sh*t 91 octane that you guys get in cali causes any knock events (which you may not even feel driving) the ecu will retard timing, and dump fuel like your seeing under boost now as well, and will continue that for a few cycles till the ecu determines that there arnt more knock events happening and slowly ramps things back up (you would hardly notice any of this happening in real time, BTW)

heres the flow chart of the diffrent pumps...look at how the na pump really looses flow as pressure goes up.

Click to view attachment
ILoveMySilly97
It's not that I don't want to switch fuel pump. I have the walbro in my garage. I'll be swapping into later. I'm just testing the stock gt fuel pump. Since people always says it's required for a 3sgte swap. I want to do this because there are some people who just wants to swap and go at a minimum. Doing this for future swappers who wants to see real life time lapse of the gt fuel pump in work.

Besides. I'm not planning on big power. Just 14 psi and basic bolt ons.
Smaay
Amy's car with the 3rd gen is running the stock GT pump, at 15psi its rich. in the high 10s low 11s
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