Fuel Pressure, A/F interesting tidbits. vrg3?

[scuzzy]

Hey guys.

Finally got my under-the-hood fuel gauge installed.

reads 25-26PSIg at idle - which is expected since -20inHg is about 10PSIa lower than atmosphere (engine vac)

Interesting thing is that when I leave the car off, fuel pressure drops to 0psig. I know it's not running through leaky injectors because I've got no trouble starting or idling or anything of that nature. I assume the issue is with my fuel pressure regulator?

Either way, not inclined to believe it's much of a problem really.

I did find it easy to clamp down on the output hose (return back to the fuel tank) and get the idle pressure up to 40-50PSI. the pump will hold it, but when you rev the engine the pressure DROPS.

This is the stock N/A pump, so I expect it can handle the pressure, but not the flow; hence for the pressure falling.


Other interesting things is that I'm running this engine (turbo and all, @ 5PSI) on the stock N/A engine management with N/A injectors and whatnot. I installed an Innovative Motorsports O2 wideband gauge, controller and sensor recently...

The ECU manages to control the fuel at idle to achieve nearly a 14.7:1 mix, and even under light load it's around the low to mid 14's.

When under moderate load (part throttle, sub 4500 rpms, building 5PSI boost) the A/F drops to about 11-12; after 4500 rpms and wide open throttle the A/F peaks to 15.5, sometimes it's hit 16 and I start getting det and ignition retard; but now I can keep a close eye on it and drive the car in the 10-13AFR 'safety range'.

Funny, I didn't think the ECU would be able to fuel this at all on boost, but it looks like it's running the injectors static to do so.

Hope to have new engine management soon.

[BXSS]

+1 on the N/A pump not being able to flow enough (volume) @ higher pressure levels to keep the fuel pressure up.
A Walbro 255 HPHV pump will have no probs with keeping the pressure up.

I think some of the folks with "turbo kits" on MAF cars used to run a FMU with a small plate in order to keep AFRs safe throughout the RPM range.
They way the newer "turbo Kit" guys are doing it now is e-manage.

My own Ghetto-Turbo'd OBS is MAP so I can't give you MAF specifics, but I use a tiny FMU plate, & a 1000cc alky injection jet with progressive controller - & it works/runs very well.

[93forestpearl]

Its normal that your fuel pressure drops back to zero after a while. It should slowly go back to zero though.

It take s at least an hour for me to go from 60psi back down to zero, maybe more as I've never actually timed it.


Oh, and don't worry. My fuel pressure will be back down to normal once I get the 900's in.

[CFK]

Old Thread I know, but just curious what the best ratio for a FMU in a turbo car ? Do you buy a specific ratio or I guess a Rising rate FPR ( FMU )

[Legacy777]

Personally, I feel the stock fuel pressure regulator is adequate. If you need more fuel, you should upgrade the pump and injectors.

A rising rate fuel pressure regulator with the stock injectors may work ok, but may not give you the consistency and proper fueling under all conditions.

What mods do you have that would warrent getting a RRFPR?

[CFK]

Mods:

- TD04
- TMIC
- MBC
- FCD
- 3" TBE
- LC-1 WB A/F Gauge

The car hasn't even been insured yet as Im buying more parts than I can keep up with, but I ended up buying a TD04 (in the mail) and I will be buying a fuel pump of some sort. I was reading an old thread where Vikash had stated that he was running a RR FPR W/ bypass and Supra F. pump with the stock injectors he said it seemed to work well. So if the ECU can't properly control any other injectors, but you can just control the stock ones with the FPR that makes sense to me.

The stock ECU cannot adequately control any injectors other than the stock ones.

I am running my stock injectors and stock ECU. My fuel system upgrades consist of the aforementioned pump and a Vortech RRFPR with an adjustable bleed valve to control the amount of fuel pressure rise. If you want a simple solution, I highly recommend this one.

Thread containing info:
http://bbs.legacycentral.org/viewtopic.php?t=34681

I already purchased a Aeromotive RR FPR cause it was on Ebay and Im very impatient .
If I don't go that route I can always just get some NA rails and JDM sidefeed grey top's then use the FPR on my Jetta build and sell my adjustable one.

Your thoughts Josh , I know your running a TD05. What injectors and management do you have

[Legacy777]

I am running the STi yellow 550's and have a Link stand alone management.

Regarding Vikash's comments and the RRFPR. I'm not going to say it can't be made to work, but it may not be an optimal setup and you may have to spend some time tweaking things to get it to run it the best.

All you can do is give it a shot and see how you like it.

[CFK]

For sure, I just figured with SOHC heads, and a TD04 around 14-16 psi the yellow tops might just be a little oversized.

Once I get everything installed I will just see what the A/F ratios are and go from there

Thanks Josh