SC300 12v Fuel Mod w/ Pictures - FAQ
Pole Position
Joined: Apr 2006
Posts: 2,873
Likes: 0
From: South Florida
OK, here is my Dyno chart.
Boys and girls, this is what we are talking about.....
As you can see, I have problem right before, during and right after the big turbo is on! It becomes stable as soon as both turbos are fully boosting.
Actually, my engine ran lean during transition!
Scary!
The Supra TT fuel pump is capable of supporting up to 800 HP.
I am going to dual feed TT fuel pumps (like my Z32TT) when I single it.
That's all the fuel I need.
I rather bet on TT fuel pump than Walbros.
Especially, when I am boosting requiring more fuel.
I rather spend little bit more money than blowing up my engine.
I am correcting this transition problem by installing the AFC and tuning it.
The stock supra pump is bigger than a sc pump but it cannot supply fuel for a 800 hp car .Those pumps wasen't built for 800 hp .This is where a walbro comes in ,there is no way a supra pump is gonna flow more fuel than a walbro fuel
pump. If this was right then why mostly everyone with supras/boosted sc are running walbros .A smart tuner won,t even touch a car with stock fuel trying to pull 600 hp.
Pole Position
Joined: Apr 2006
Posts: 2,873
Likes: 0
From: South Florida
One more this that was not mentiones is that this fp mod is not a good idea for a daily driver because the constant 12 volts will cause the pump and relays to run hot and your mpg will go down.
cause what relays to make what mpg to go down? I wasnt aware any relays in the car affected mpg.
Supra pump wont handle 800hp; that is some serious misinfo there. It flows more than a GS341 Walbro does; but twin GS341s will cure that issue and the price difference is pretty heft; Supra pumps cost more than twice of the GS341
dejacky,
there's already a fuse inline from when the fuelpump relay begins supplying power to the pump.
sc250tt - the fuel pump may run hotter, but with the increased voltage it will still have a higher flow capacity at higher fuel pressures. Its life will be shortened, but not within the lifetime of ownership of the car more than likely.
Supra pump wont handle 800hp; that is some serious misinfo there. It flows more than a GS341 Walbro does; but twin GS341s will cure that issue and the price difference is pretty heft; Supra pumps cost more than twice of the GS341
dejacky,
there's already a fuse inline from when the fuelpump relay begins supplying power to the pump.
sc250tt - the fuel pump may run hotter, but with the increased voltage it will still have a higher flow capacity at higher fuel pressures. Its life will be shortened, but not within the lifetime of ownership of the car more than likely.
Pole Position
Joined: Apr 2006
Posts: 2,873
Likes: 0
From: South Florida
cause what relays to make what mpg to go down? I wasnt aware any relays in the car affected mpg.
Supra pump wont handle 800hp; that is some serious misinfo there. It flows more than a GS341 Walbro does; but twin GS341s will cure that issue and the price difference is pretty heft; Supra pumps cost more than twice of the GS341
dejacky,
there's already a fuse inline from when the fuelpump relay begins supplying power to the pump.
sc250tt - the fuel pump may run hotter, but with the increased voltage it will still have a higher flow capacity at higher fuel pressures. Its life will be shortened, but not within the lifetime of ownership of the car more than likely.
Supra pump wont handle 800hp; that is some serious misinfo there. It flows more than a GS341 Walbro does; but twin GS341s will cure that issue and the price difference is pretty heft; Supra pumps cost more than twice of the GS341
dejacky,
there's already a fuse inline from when the fuelpump relay begins supplying power to the pump.
sc250tt - the fuel pump may run hotter, but with the increased voltage it will still have a higher flow capacity at higher fuel pressures. Its life will be shortened, but not within the lifetime of ownership of the car more than likely.
Bean, i did not mean the relay will affect the gas milage .I meant apart from the relay overheating you will also suffer low gas milage. As for the fuel pump going bad it happened to my 92 sc400 ,The previous owner was spraying a 200 shot of nos on the v8 and i guess for more fuel pressure he by passed the ecu .To no avail the pump died the first week i owned the car. This car had 220,000 miles on the dash ,You might be right about the pump not dying within the lifetime of ownership but keep in mind that alot of cars on here have high mileage ,so it might pertain to some owners on here .
Lead Lap
Joined: Oct 2006
Posts: 581
Likes: 0
From: texas
Hey,
This might be a little off topic. But I think its somewhat related. I recently installed a walbro fuel pump as an upgrade. I had to cut and crimp wires and I must admit that I'm pretty new with wiring. Haha to the point where its really the first time I spliced anything. Anyways, It works fine but sometimes it bogs down then dies and, sometimes, it won't start back up. I removed the back seats so I can hear the pump. It seems that it struggles to keep on sometimes. At first I'm thinking that it might be just bad crimps, but whats the possibility that this could be it?
This might be a little off topic. But I think its somewhat related. I recently installed a walbro fuel pump as an upgrade. I had to cut and crimp wires and I must admit that I'm pretty new with wiring. Haha to the point where its really the first time I spliced anything. Anyways, It works fine but sometimes it bogs down then dies and, sometimes, it won't start back up. I removed the back seats so I can hear the pump. It seems that it struggles to keep on sometimes. At first I'm thinking that it might be just bad crimps, but whats the possibility that this could be it?
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Lead Lap
Joined: Oct 2006
Posts: 581
Likes: 0
From: texas
once again big wiring noob here 
. I have solder and shrink wrap at the ready just in case. I was just wondering what the chances are. Besides.. I used what came with the kit.. Whihc were 2 crimps and... thats it
. I have solder and shrink wrap at the ready just in case. I was just wondering what the chances are. Besides.. I used what came with the kit.. Whihc were 2 crimps and... thats it
Lexus Champion
Joined: Sep 2006
Posts: 1,626
Likes: 8
From: Kansas City
Isn't it a bad idea to put a big Walbro in there if you're bone stock? I have a few NA mods on the car and with the stock fuel pump and stock fuel pressure I still had to take out a bunch of fuel at WOT to keep it from running super pig rich.
Anyway, I did the 12v mod tonight (well...this morning? I guess I've been in the garage doing various things to the car off and on for about 7 hours now) and I'll find out later on in the day how things change. I can hear the pump come on key-on now for the first time.
Anyway, I did the 12v mod tonight (well...this morning? I guess I've been in the garage doing various things to the car off and on for about 7 hours now) and I'll find out later on in the day how things change. I can hear the pump come on key-on now for the first time.
Lexus Test Driver
Joined: Aug 2003
Posts: 887
Likes: 0
From: California
I have no problems as a daily driver with my 12v mod on TT pump. Regarding the fuel mileage, it is solely foot related. My mpg can go as high as 27 mpg hwy no boost staying out of throttle at 65. I don't think I've seen it under 16mpg even on wot track days.
Pole Position
Joined: Apr 2006
Posts: 2,873
Likes: 0
From: South Florida
Me myself never had any with it until i drove a couple hundred miles that day,made a stop tried starting the car and all i can hear is fuel bubling in my tank .I swapped out the relay and the problem was gone .I havent had the problem since but i put 10 miles a day so the pump wont overheat . Next time i put a couple hundreds miles on her again i will see it it was the 12v mod that caused it. As for the gas milage im auto....... so i wont the same gas milage as you.
