I know that it is generally accepted as a good idea when running higher boost levels. But does the individual setup make any difference when determining if it is necessary?

I have a Walbro 255 with AFPR, 550cc injectors on an EVO III 16G. Currently running 18-19 psi max but over the course of this next year I plan to do some other mods and then hopefully take the boost levels as far into the 20's as I safely can. I will be keeping the 550's but I already have a water/meth injection kit. I just measured voltage at FP. At idle it showed 12.25V. At the battery terminals it was 14.33V.

All opinions are welcome.

I don't see why you wouldn't. It's cheap insurance and it's easy to do. Especially when the battery is in the trunk Needed or not, it's one of those things I would do just because I could. I think answered your own question, you had 14v charging, but only 12 at the pump. I realize a 255 at 12v is still pushing more fuel than a stock pump at 12v. You paid for a bigger pump, why not use all of it?

Agreed. It's extra insurance and you'll be running your pump at the voltage it was designed to operate at.

Do it Romeen! It's too easy to pass up. Look here for some additional info and tips. Please, if you have any questions with your 2G GS-T, please ask me.

Yes, do the rewire. Probably will get away fine without one currently but will need it in the future & its cheep/easy to do, so might as well do it now & be on the safe side. Fuel pump flow is directly related to voltage & you already know what you are currently seeing with the stock wiring & what you should be seeing

I did the rewire today. The results are actually even better than I had anticipated. Idle voltage at battery terminals was 14.36V today. Using the exact same spots that I used to check FP voltage yesterday (12.25V before rewire) I now got a rock steady 14.22V!

Thanks for the responses guys and also thanks for convincing me to do it.

One thing surprised me a bit. I thought that I would have to readjust my base fuel pressure after the rewire. With the increased voltage being delivered to the FP it should now be pumping a larger volume of fuel and this should raise my BFP (I assumed). It actually stayed about the same, maybe an increase of 1 psi. Maybe I am missing something simple or some other compensatory mechanism.

If anyone can explain I am curious as to why there was so significant change in the BFP.

romeen said:

One thing surprised me a bit. I thought that I would have to readjust my base fuel pressure after the rewire. With the increased voltage being delivered to the FP it should now be pumping a larger volume of fuel and this should raise my BFP (I assumed). It actually stayed about the same, maybe an increase of 1 psi. Maybe I am missing something simple or some other compensatory mechanism.

If anyone can explain I am curious as to why there was so significant change in the BFP.

Click to expand...

A FPR is exactly that, a regulator. It doesn't matter what psi is put into it, it will always see (nearly)the same psi it is adjusted to(as long as it is less than or equal to the input pressure) besides the 1:1 rising/lowering rate. It is the same concept as a regulator on an air compressor, but works almost backwards since a FPR regulates pressure by bleeding it back into the return line.



This is a diagram of a FPR similar to yours, but without a rising/lowering rate.

The pressure from the rail is seen from the bottom line, and presses on the diaphragm, which is resisted by the spring. If the pressure in the rail rises, it will push the diaphragm back a little more, opening the pathway to the return line on the left, and bleed off a little more pressure to compensate.

Mr Peepers said:

If the pressure in the rail rises, it will push the diaphragm back a little more, opening the pathway to the return line on the left, and bleed off a little more pressure to compensate.

Click to expand...

That's the process that I was missing. Thanks.

No problem, glad to hear the rewire results

romeen said:

I did the rewire today. The results are actually even better than I had anticipated. Idle voltage at battery terminals was 14.36V today. Using the exact same spots that I used to check FP voltage yesterday (12.25V before rewire) I now got a rock steady 14.22V!

Thanks for the responses guys and also thanks for convincing me to do it.

Click to expand...

SOB... I forgot to test mine before the process.