axr6

I've already posted that my replacing of the stock cat converter with a home built E-Bay MP - Metallic substrate cat converter combination had given me boost creep.

Also, I am running on the ragged edge of fuel injector duty cyces to maintain 11.2 AFR at 8K, 12 psi boost.

Immediate plans:

1) Purhased a set of Supertrapp disk only set. I have extensive experience with Supertrapps starting with my first FD where I used them tofine control backpressure when I went to a MP to my numerous racecars for each of which I tended to use them for sound control. I plan to weld the Supertrapp base mounting piece to a 3" pipe that I will insert into the 6" long, 4.5" diameter sewerpipe exhaust outlet on my Corksport canister, to match up with the 3" inside diameter of the Corsksport. The supertrapps will mount to the end of this 4.5" pipe which will actually look better than that huge pipe alone. I also plan to drill holes in the 3" pipe from the Supertrapp to the canister and pack the space between the 3" and 4.5" pipes with stainless steel wire mash for a silencer effects. This, combined with the Supertrapp should make a noticable effect on the sound levels. (I think)

Now, for the fuel. I know I should switch to 1300 secondaries but being lazy to remove all the junk to get to it, I try to reserve that as my last option. What if I install a second Fuel Pressure Regulator in the return fuel line and have that take control of my fuel pressure to the injectors (keeping the original FPR in place per Max Cooper's solution.)

Question is, what is a reasonable amount of inrease over stock fuel pressures that I can get away with without stressing injectors or else?

Also, my car runs perfect AFRs in the low RPM non-boost ranges right now. Much of my PFC injector settings are 1.00 at that range. Can I actually drop below 1.00 to lean out that region when I increase the fuel pressure?

Has anyone done this fuel pressure increase solution and have postitive or negative experiences to report?

Would greatly appreciate any answers.

Changes and work will have to wait, as I'm sitting here with a broken neck, and spine, given to a ridiculously arrogant 150' pine tree that got in my way 12 days ago on the ski slope while doing tricks. HUGE direct hit to the head, thank heavens for helmets.

Thanks

Albert

maxcooper

I read somewhere (RC Engineering web site, or Maximum Boost -- can't remember which, or even if my memory is correct ) that no more than 85 psi of fuel pressure is recommended. I suppose that is "rail pressure" (rather than base pressure), so that would be 70 psi base pressure if you plan on running 15 psi of boost, for example.

However, your fuel pump probably won't produce much flow at that pressure, so your fuel pump is most likely the limiting factor.

I suggest figuring things out in this order:
1. how much fuel flow do you need? X gal/hr
2. how much pressure would you need to run to get that amount of flow with the injectors you plan to use? Y psi
3. can your pump supply the required flow at the required pressure? yes/no

My fuel calcs page can help:
http://maxcooper.com/rx7/how-to/fuel_system/calcs.html

I just read the last para -- Sorry that happened. I hope you feel better soon and recover fully.

-Max

axr6

Max

Your great calculator, combined with a flow chart for the Walbro GSS 341 tells me that my pump will be able to provide sufficient fuel flows with stock injectors for r 50 psi effective fuel pressure.

I guess, I've answered my other question when I've just checked my PFC Commander fuel injector map adjustment range being from 0.500 - 1.496. Been running up at the very top right now with high 90% duty cycles. Should be able to lower the duty cycles and the injector correction numbers with an increase of 10 psi fuel pressure while, should be able to lean out the lower end if it gets way too rich as the result of the increased fuel pressure.

Does that make sense?

Yes, the head, neck is pretty bad and just now it did not do much good to squeeze into my 7 and tilt my head to read the Commander. Oh, well....

Thanks

Albert