Can fuel pressure drops between gears be prevented?

[sqr]

Can fuel pressure drops between gears be prevented?

I have heard of a regulator that maintains the pressure between shifts in a boosted application. Anybody have any info?

 

[blackberry]

The fuel pump will keep a constant pressure as long as there is a constant voltage going to it. Our cars have some problems keeping a constant fuel pressure, because of low voltage to the pump. A simple rewire should work.

 

[sqr]

The fuel pump will keep a constant pressure as long as there is a constant voltage going to it. Our cars have some problems keeping a constant fuel pressure, because of low voltage to the pump. A simple rewire should work.

Don't the turbo cars have a rr regulator? If the boost drops between shifts wont the pressure drop and than have to rebuild when the boost come back up.

 

[Absit]

Yes, get an automatic transmission.
I think it was Gixxerdrew that was looking to run a constant pressure fuel regulator but I don't know what came of it, it's an extremely difficult task.

Why are you concerned with it?

 

[Colt4G63 also]

The pressure is dependent on boost refrence at the pressure regulator. The pressure difference between the manifold side of the injector and the fuel rail side of the injector is kept constant at all times. If the base pressure is 43 psi at zero vaccum, then it would be 63 psi at 20 psi of manifold pressure. 43+20=63. Therefore the fuel is still at 43 psi more pressure than the manifold it's injecting it into. Same goes for a vaccum situation; the pressure is lowered.

The ECU expects this, and uses this expectation to maintain a pecisely metered amount of fuel injected into the engine. Try NLTS if you don't want to loose boost (and fuel pressure) between shifts.

Since fluid doesn't compress, the fuel pressure should be able to react (theoretically) more quickly than the manifold pressure that's controlling it.

 

[Absit]

The pressure differential between the manifold side of the injector and the fuel rail side of the injector is kept constant at all times.

You should mention that this is in a perfect world where the turbo spools abolutely no faster than the fuel pressure regulator can react without "bouncing" - as was the topic of the thread about a constant pressure system.

 

[Colt4G63 also]

I never noticed bouncing fuel pressure on my setup, and I have a fuel pressure gauge on my dash. My e316g spools pretty quickly too. I wonder if there was some other factor playing into that condition.

In my perfect world there's no air leaks in my regulator or vaccum lines .

 

[Absit]

For us mere mortals I'm sure it's never an issue. For a full on road racing build that he had, maybe..

 

[Colt4G63 also]

I'm sure whatever issue he had could have been solved by redesigning some vaccum lines or adding a fuel pressure accumulator.

 

[sqr]

The car in question is actually a Conquest (Starion), so the ecu calibration is not as good as a dsm. I always got a lean spike after shifts. Not sure if that is an issue on dsm's.

I had heard of a way to delay the pressure drop off. I see some cars use an accumulator in the regulator?

This is my first track log of fuel pressure.

I am not sure why the fuel pressure is lower in first and second. That is a 5-6 psi difference in pressure from 1st to 4th.

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The fuel pressure seems to play catch up a little after shifts. Notice how the lean spike after the missed shift is worse.

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