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Upgrade from 255 Walboro to bigger?

Posted: Sat Apr 09, 2022 9:21 pm
by G. Wiffington
Hey do you guys think I should upgrade from a 255 Walboro to a bigger pump to lower duty cycle? I have attached two datalogs.

I have the old fat body style RC 750cc's & the fuel pump is not relayed by the pump, so I am just using the stock wiring as of now. Would a relay setup at the pump help give more pressure?

I also have a JDM stock fuel rail so I used a longer, skinnier -4AN hose for the rail to stock fuel filter line. I was wondering if that is way too restrictive causing the duty to be higher.

I do have a stock fuel regulator & no fuel pressure sensor. I guess I should Install those? (fuel pressure gauge & adjustable regulator)

Setup is F22B non vtec stock head & bottom end, 98 EK hatch chassis.

Finally spun third pretty good on street tires Hankooks (9psi, 82% duty 13 degrees timing).

Re: Upgrade from 255 Walboro to bigger?

Posted: Mon Apr 11, 2022 10:09 am
by Spunkster
You need to see what the pressure is doing. You may need larger injectors. This is something you may want to discuss with your tuner.

Re: Upgrade from 255 Walboro to bigger?

Posted: Tue Apr 12, 2022 2:46 pm
by G. Wiffington
I am my tuner in this case lol. Still learning for sure

Okay I will see what the fuel pressure is doing.

Thank you!

Re: Upgrade from 255 Walboro to bigger?

Posted: Fri May 06, 2022 6:58 pm
by G. Wiffington
Okay update:

I have an adjustable fpr now installed & it is set at base 43psi. The duty cycle is a little lower about 82% for the same pull as I uploaded before.

Would 50psi base pressure on RC750's too high?

Re: Upgrade from 255 Walboro to bigger?

Posted: Mon May 09, 2022 8:53 am
by Spunkster
It is probably ok.

Re: Upgrade from 255 Walboro to bigger?

Posted: Sun May 15, 2022 9:03 am
by G. Wiffington
Thank you.

Raised the pressure a little more & looks like I definitely lower the duty cycle.

Here is another pull finally hitting 11lbs.

New wastegate with 7-8lbs spring, the old one had a rip in the diaphragm & the spring was only about 4lbs.