[JimM]

Anyone know anything, or have any opinion on this: http://www.racepumps.com

Thinking such a thing might be nice on my TBI, but wondering if/how it would work.

System needs 4 psi at idle, rising to 21 psi at WOT.

[Doug F.]

TBI needs a constant fuel pressure. The main issue I've heard about the racepumps is initial priming.

[JimM]

Originally Posted by Doug F.

TBI needs a constant fuel pressure...

Maybe I need to read the directions again... The first 3 times I read them, it said the regulator was referenced to manifold vacuum, to set it for 14 psi at idle, and it would go to 21 at WOT.Also seem to recall it said if there was boost, the pressure would rise 2 psi per lb.

[JimM]

Originally Posted by Doug F.

The main issue I've heard about the racepumps is initial priming.

cranking for even a few seconds before lightoff would bother me...

[scblucam]

This is what I have been looking for, some ideas on how do it. It makes perfect sence if it will hold initial pressure while shut down. An electric pump will or will not do it.

[JimM]

The efi systems are set up so the instant the key goes to run from off, the electric pump is run for a couple seconds to pressurize the system.

[wiskeesour]

cant you install a relay to get pressure before light off?

[JimM]

The racepump is mechanical. It replaces the stock engine mounted pump, and it can develop up to 150 psi, but only when the engine is turning.

[RickD]

The concept of the racepump appeals to me, Jim, but I've read on chevelles.com of some issues that would stop me from getting one at this time. Loss of pressure when sitting over night and, I believe, some heat issues even when using their insulator block. Their website is pretty good for info and threads.

[Doug F.]

All EFI runs at a constant pressure with caviots. A N/A engine runs with a fixed regulator pressure. For applications where the injectors are in manifold vacuum, it is desirable to vacuum reference the regulator. This maintains a fixed pressure differential pressure. The gauge pressure when vacuum is applied is "lower", but the differential pressure is the same. TBI's are not vacuum referenced as the injectors do not see manifold vacuum.

With boost, most regulators are a 1:1, 1 psi of boost = 1 psi of additional fuel pressure. This is the SAME deal as the vacuum above. 1 psi of vacuum removes 1 PSI of pressure seen in the diaphragm. FMU's are a different beast and have a different rise curve.

Some new cars like Fords have PWM returnless pumps. They actually mimic the pressure curve of a vacuum referenced regulator.

None the less, you need a constant pressure with EFI.

[Everett#2390]

Originally Posted by Doug F.

None the less, you need a constant pressure with EFI.

Agreed, need a constant, er, continual flow, not repititive pumps.

[Rodder]

GM GenIII and newer smallblock EFI uses a constant pressure regulator--it's not vacuum/boost referenced. Instead they recalculate the injector flow as manifold pressure varies.