jdmz

I'm upgrading my walbro 255 to a walbro 450 in hope that I can push 450-500whp with a aem fpr to raise the fuel pressure.

I tested my fuel pressure with 255 and Id1000 on the stock Fpr and it measured 54 psi idle with vac connected and 59 psi without vac. Is this normal? I thought stock ap1s are supposed to be 43.5 psi?

Anyway, I am installing a 450 to run e85 at 14 psi and was wondering what's a good base fuel pressure to set it at.

Charper732

the stock fpr with a walbro 450 will produce 54 psi as well. If you don't already have a FPR, you really dont need to waste the money on one.

jdmz

Do you mean my Id1000 should flow enough for 14 psi without bumping the fuel pressure? The reason why I got an fpr is to bump the base pressure to flow more fuel for the higher demand with e85. I was already at 65% duty cycle on my stock fpr and walbro 255 at 12-13 psi on 91 octane. With more boost and 30% more fuel required from e85 I will max my injectors out.

yamahaSHO

Fuel pressure is going to be related to your tuning... If you were tuned at that high pressure and swap a pump, you will need to match that same base pressure. Standard pressure is 43.5 PSI, so if you set your base pressure to that, you will want to check over the tune.

jdmz

Thanks all, I got it sorted with Jeff Evans.

He explained if you swap to a higher performing fuel pump with the stock Fpr, there will be a rise in fuel pressure because the more powerful pump is going to try to squeeze more fuel through the same orifice.
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yamahaSHO

I thought I read that were using an AEM FPR. Yes, the stock regulator will be overrun.

s2000Junky

So to bring back to point, if you/Evans thinks you can reach your power goal/fuel demands with the 450 at 54psi fuel pressure and ID1000, then you don't need the AEM adjustable fpr.

yamahaSHO

That depends what the fuel pressure is doing once the injectors start using fuel. Generally, pressure drops.

I would ALWAYS recommend a better FPR.

jdmz

Yea he recommended running higher base since I'm maxing out my Id1000 cc injectors. I'm running 59 psi with vac connected which is surprisingly high with just 255 and stock fpr.

I got the aem fpr for a good deal locally. The only thing I wish I would have done was buy the "high pressure" version of the walbro 450.

jdmz

Wow after installing the walbro 450 it went to 73 psi on stock fpr.