obZidian

iTrader: (2)

Ok folks;

Specifics on the car:

2001 Corvette Auto
Stock LS1
Maggie @ 10psi (3.0" upper)
Stock returnless system
42lbs. Injectors, swapped for 60lbs. injectors (P# 107961, GB data)
Stock Pump, swapped for a Walbro 450lph
BAP (removed)

So I've been helping out a friend tune his. Car was purchased with the maggie, 42lbs. injectors, a BAP and the stock fuel system including the fuel filter/regulator, pump, wiring. etc.

All was well until we swapped the pulley and about finished the dialing in the MAF-high region. On the last run, the car misfired/detonated really bad. (Compression test turned out fine, no hurt cylinders) The log indicated that the perhaps the pump for the blower stopped working since the IAT's went through the roof. 200 iat's.

After that run, the vehicle has been seeing a constant fuel pressure drop from 56psi stock pump to about 52psi at WOT.
58-59psi Walbro 450lph to about 52psi a WOT.

What has been done to diagnosis the issue:

1. Fuel Filter/Regulator replaced for a new one. No Change.
2. Swapped the pump to a Walbro 450lph. No Change.
3. With BAP. No Change.
4. Removed the BAP. No Change.
5. Used 60lbs. cleaned and flown. (used) No Change.
6. Installed 42lbs. and Data. No Change.

So, last night we tried the injector swap to see if the used injectors, even after been clean were causing all our problems... that turned up to be just another dead end.

Am I/we missing something? I did at one point checked the voltage at the pump harness with and without the BAP and that seemed fine. 12v's, climbed the about 17v's with BAP.

The tune, from the beginning of the first run to the last one only saw changes to the maf table and enabling/disabling LTFT's. (BTW: MAF ONLY, HPTuners.. I have all logs and files if anyone cares to take a look)

So... as the title says: I'm stumped. Beyond relocating the fuel pressure regulator to after the rails, and adding a return back to the tank, I just cannot seem to think of anything else.

Obviously the fuel pressure drop is not normal. She should be steady a 58psi. I WILL NOT HACK THE PE TABLE TO COMPENSATE.. that is a bandaid, a potential problem waiting to happen and not the right way of doing things.

Let me know if anyone wants to see the scans.

A.

obZidian

iTrader: (2)

Anyone?

Lonnies Performance

iTrader: (16)

The stock regulator cannot accutately control the pressure at the engine. It cannot compensate for the line restriction at high fuel flows. It is fine for a normal powered car, but will drop pressure at large power levels.

obZidian

iTrader: (2)

Yeah, seems like that is the only variable left to address.

Given that the stock system has a return to the tank by the filter, could one plumb a regulator after the rails and run a return back to that stock "return" from the regulated filter? Seems straight forward.

The rails on the maggie have crossovers on the front and rear of the rails. I'm thinking we can run the regulator and return from the rear passenger rail back to the tank. Could you pm me with the cost of a regulator and some fittings lines?

Thanks.

EDIT:

One question though.

Before the car started to loose fuel pressure, we did about 3-4 full wot runs to 140mph+ without any issues then suddenly she started the drop pressure. Wouldn't the pressure drop immediately happen? Why would it need a few runs to suddenly develop this problem?