Makes sense... I wonder why my alldata manual only shows and describes 3.

 

Here is a link to an older sticky that has a lot of good info on dual walbro, wiring, parts, and general fuel info.

https://www.camaroz28.com/forums/sho...my+dual+walbro

 

Actually no, I don't think that will help increase the hp possibility for a pump... only injectors. You can up the psi at the regulator (so less gas returns to the tank) to increase the amount of fuel that goes through an injector of a given size, but messing with the regulator does not affect the amount of gas a pump can actually push through the lines.

A pump's maximum flow/delivery is relatively unaffected by the fuel pressure regulator.

Now voltage is a different matter entirely, but you alrady covered that one (hot-wire feed from alt, better ground strap, volt booster like Casper's Electronics sells to up the alternator voltage 10% to the entire car when 70+% throttle is useful, as would be a boost-a-pump design upping voltage just to the pump).



My siggestions for a sticky: the formula for converting injector ratings for different pressures.

Also, maybe a mention that injector rating has nothing to do with hp/fuel demands under nitrous as it does with turbos and blowers that get their additional fueling through the injectors. Nitrous wet kits depend on pump and lines only... not injectors.

Oh yeah... and the difference between EV1 and EV6 injector bodies, as well as the diff between USCAR and ummm, the "other" injector connector style.

lastly... I'd suggest a link to shoebox's site for fuel pump schematics and locations.

 

I agree with that - but thats what I meant in the first place. I should have been more specific - I was referring to the system and not the pump itself.

 

I figured as much... just thought I'd clarify for those who read this later.

 

The system pressure has an effect on pump performance. The pump has a flow curve, that generally shows that as discharge pressure increases, flow rate decreases. As a result, increasing the system pressure can reduce the HP level the pump can support, if the flow vs pressure curve is steep enough. You may be bypassing less, to keep the pressure higher, but the pump output may fall off more the the bypass reduction saves.

 

True, however as you said, increased line pressure decreases fuel pump flow rates / efficiency... increasing line pressure doesn't benefit the pump in any way. If your pump is maxed out, increasing line pressure won't do squat... you need to up the voltage or go to another pump.

Here's a great comparison of pump flow rates (in lph) accross various line pressures... at various voltages. This graph/link may be a good inclusion for the sticky.

http://www.stealth316.com/2-fuelpumpguide.htm
Note: the link above is comparing Dodge Stealth / Mitsu 3000GT pumps. Due to their turbo set up, the fuel rail pressure will be 43psi + boost (so the 43psi differential between the rail pressure and the manifold pressure is kept constant... to keep the injectors accurate).

Beyond about 30psi of boost (74psi total rail pressure) you have to consider injector lock up in a NA application, though the turbo guys can get away with it since the differential pressure (which the solenoid has to open the pintal against) is still only 43psi. Upping a rail pressure to the same 74psi in a NA application is way more risky and not reccomended.

As you can see from the graphs, upping the voltage can be better than going to a bigger pump... hense the benefit of a hotwire/ground upgrade and a voltage booster.

Upping a stock LT1's rail pressure by 10psi (to 53psi) reduces the PUMP's flow rate by ~5%... though the injectors get an 11% increase in fuel flow:

FRold(NewP/OldP)^0.5 = 24(53/43)^0.5 = 26.6 psi

So yes, pressure can up fuel delivery though small injectors, but only until the pump can't keep up or the pressure gets so high the injector solenoids can't open against the rail pressure (estimates range what that max is... but ~80psi is usually tossed around as scarey ).

At 20psi increase, the injector increase is 21% more fuel through the injectors, while max fuel flow from the pump is reduced only about 8%... so there will be a point where the most fuel can be pushed through injectors and pump... but I'd personally prefer a 43psi system with less back-pressure on the pump and the max fuel flow being controlled by the injectors... you never want your pump to limit fuel flow since the PCM doesn't control it nearly as effectively as injectors.

If your pump was at max flow and a pressure increase in the rails (say under boost or from an adj regulator) you will be starving the system, however no system should EVER be at that point or you were already in trouble... the pump should always be able to supply more fuel than the rails/injectors can deliver or else pressure will drop off and you risk lean conditions with a slight voltage drop. A 5% loss in pump flow shouldn't affect your fuel system unless you were already in trouble... a rail pressure change should never be enough to reduce pump preformance enough to kill an engine if set up right, but it does have a large effect on injector delivery rates which is why I generally assume a) injector-killing pressures will be avoided anyway, so max pump loses shouldn't exceed ~10% and b) there should be significant excess fuel flow from the pump to keep the injectors/rails well feed and pressurized... implying a small fuel flow reduction shuold be tolerated fairly well anyway.

I've also had a feeling (though no actual data) that pump life is shortened by higher rail pressures... but it's just a hunch.

 

Avoid Casper's Volt Blaster like the plauge. Been chasing down a miss/rev limit at 5500rpms on my 396 build up.

Speed Secrets took The Silver Dragon out for some logging and tracked down the cause in no time flat. At 62% throttle (TPS) the alternator was putting out 13.6v as expected.... the next frame showed the miss, a 0% TPS reading, and a system voltage of 15.6v.

Even without triggering a code (DTC) for voltage out of range (16.5v is the code trigger point I belive), the high voltage played havoc with the TPS readings. Also, the sensor malfuction prevented the engine from going into PE mode (for obvious reasons... the PCM assigned TPS to 0%).

I removed the voltage blaster on their reccomendation and now the TPS can go all the way to 100% without problems.

While the voltage gain may help the ignition, fuel pump, and headlights (yes, you can tell when the Volt Blaster kicks in when driving at night)... it takes a dump on engine sensors. Why do sensors fail to register correctly at voltages that don't throw a code? I dunno... go figure.

For the sticky: Until GM releases a 0-5v TPS that can handle a 16v input...DON'T use a system voltage over 15 volts! 14.x volts seems fine. If you need more fuel pump voltage after installing a hot-wire upgrade... use a direct boost-a-pump system. Same goes for ignition... if you need more juice either close the gap a touch or get a hotter coil.

 

For the 93's (reprinted GM code sheets in Howell Engineering Developments manual), DTC 53 for system over voltage is 17.1 V for 2 seconds.

The PCM supplies the regulated 5 V reference. It would appear the source can not operate at the high voltages you were using. What happened to the other devices that use the PCM regulated 5 V reference, like MAP, coolant temp, etc?