Who has used the kenne bell fule rail pressure disc?

[zonk22]

Who has used the kenne bell fuel rail pressure disc? Did you modify your tune because of it?
Kenne Bell 99-04 Mustang Fuel Rail Pressure Disc [FRPDISC] - $15.99 : Performance Parts - Ford Mustang - Cobra - Dodge Viper - Chevy Corvette - C6 - LS1

 

[TRBO VNM]

have you searched? seriously?

a thread was just posted about this within the past week or something. I have seen people posting about it a few times in the past month.

so yes, people are using it.

 

[zonk22]

thanks, I'll search again. I'm just trying to figure out whether or not a no tune is required.

 

[Ironhand]

See sig. Yes Im using one. I started using one after I popped an FRPS with a fuel pressure spike of 78psi. The proper fuel setup though shouldnt need to have one. I think the Fore Rails have it built in.

 

[FAsnakes]

When i was running an FRPS i had the disk and didn't have a problem pop'ing the FRPS.. .

I've since deleted my FRPS - but don't see why you would need a tune..

 

[zonk22]

I was just worried that it may effect my fuel curves

 

[FAsnakes]

I was just worried that it may effect my fuel curves

Just call your tuner to be sure.. .

 

[cobracide]

I was just worried that it may effect my fuel curves

It will NOT. The FRPS is at the end of the rail and the disc has no effect on fuel pressure to the injectors, just the FRPS. Get it.

 

[zonk22]

I just assumed that the sensor helped the computer adjust for fuel needs. And I assumed that the disc may effect its ability to do so.

 

[cobracide]

I just assumed that the sensor helped the computer adjust for fuel needs. And I assumed that the disc may effect its ability to do so.

Following Bernoulli's Principle, with a capped pipe at the end (FRPS) - pressure remains constant at any given point in that capped pipe UNTIL it narrows. ie - no change in pressure until AFTER the disc. This will have no effect on the tune.

Correction: This is a closed system regulated by the PCM. Therefore pressure is constant throughout in an ideal system.

 

[Jimmysidecarr]

Following Bernoulli's Principle, with a capped pipe at the end (FRPS) - pressure remains constant at any given point in that capped pipe UNTIL it narrows. ie - no change in pressure until AFTER the disc. This will have no effect on the tune.

So will the sensor "see" less pressure than what is actually in the rail, since it is after the restriction and "tell" the PCM that less pressure is in the rail?

Wouldn't the PCM then drive slightly more pressure into the rails to "see" the pressure it expects for those conditions?

Wouldn't this result in a slightly richer condition than what the PCM is calibrated for?

Or would the O2s tell the PCM of the actual richness and over ride the pressure information and just adjust for stoich.

I suspect that the pressure is the SAME on both sides of the resistor because there is no flow volume of any significance and therefor no pressure drop through the resistance of the orifice.

But I have no proof.

 

[broke7]

no


I will even go 1 step further, if your not blowing frps's on a regular basis dont even bother putting one in. Per KB, the original concept behind the disc was to get rid of hesitations experienced with the returnless sytems, not to prevent failures.

 

[cobracide]

So will the sensor "see" less pressure than what is actually in the rail, since it is after the restriction and "tell" the PCM that less pressure is in the rail?

Wouldn't the PCM then drive slightly more pressure into the rails to "see" the pressure it expects for those conditions?

Wouldn't this result in a slightly richer condition than what the PCM is calibrated for?

Or would the O2s tell the PCM of the actual richness and over ride the pressure information and just adjust for stoich.

I suspect that the pressure is the SAME on both sides of the resistor because there is no flow volume of any significance and therefor no pressure drop through the resistance of the orifice.

But I have no proof.

The disc narrows the pipe diameter to effectively LIMIT the pressure to the FRPS. As long as the pressure is limited below the FRPS failure threshold there will be no detrimental effects. A capped pipe has equal pressure EVERYWHERE as you have assumed. Thus all injectors see the same pressure.

 

[cobracide]

no


I will even go 1 step further, if your not blowing frps's on a regular basis dont even bother putting one in. Per KB, the original concept behind the disc was to get rid of hesitations experienced with the returnless sytems, not to prevent failures.

Maybe you have inside knowledge of why the disc was created but the purpose remains the same. To limit the pressure to the FRPS, return or returnless concept matters not as long as the disc limits the pressure to below the FRPS failure point. Which it does.

 

[Jimmysidecarr]

Maybe you have inside knowledge of why the disc was created but the purpose remains the same. To limit the pressure to the FRPS, return or returnless concept matters not as long as the disc limits the pressure to below the FRPS failure point. Which it does.

Not in all cases, I have heard of some failures even after installing the disc, though I can not provide any proof links and it is my understanding that they were extremely RARE occurrences.

You have not addressed the "would it alter the air fuel" question.

Does it limit pressure only above the failure point and not below?

And if so how is that possible?

If it limits pressure wouldn't it limit pressure across the board?

Or is it large enough that under a certain point it poses no restriction so it does not alter the pressure reading?
(this is what I suspect)

 

[cobracide]

So will the sensor "see" less pressure than what is actually in the rail, since it is after the restriction and "tell" the PCM that less pressure is in the rail?.

I neglected to take into account the scenario of a capped pipe with a returness system. In this case the pressure remains the same throughout the system. FRPS failures are accounted for by instantanious pressure spikes.

Wouldn't the PCM then drive slightly more pressure into the rails to "see" the pressure it expects for those conditions?

See above - A capped pipe system sees the same pressure everywhere.

Wouldn't this result in a slightly richer condition than what the PCM is calibrated for?

Same pressure everywhere in a closed system.

Or would the O2s tell the PCM of the actual richness and over ride the pressure information and just adjust for stoich.

I suspect that the pressure is the SAME on both sides of the resistor because there is no flow volume of any significance and therefor no pressure drop through the resistance of the orifice.

Absolutely not, the resistor again limits the fuel flow spikes that are above the frps operating threshold. Remember that the PCM regulates the fuel pressure and it is the same throughout a returnless fuel system. The disc just protects against abnormal spikes.

But I have no proof.

 

[Jimmysidecarr]

Thank you for attempting to clear this up.

If it limits pressure wouldn't it limit pressure across the board?

Or is it large enough that under a certain (pressure)/point it poses no restriction so it does not alter the pressure reading?
(this is what I suspect)

I believe I may be correct with the above understanding?

IE: That there is no delta(difference) below a certain pressure?

 

[cobracide]

In the normal returnless system the fuel pressure remains constant so there should be no need for a pressure disc. Reality tells us that there are abnormalities that occur in the system where the fuel pressure spikes and exceeds the frps capacity. The disc merely limits that pressure to a threshold that will not destroy it. Sorry for not being so clear in earlier posts.

 

[cobracide]

I've corrected my error in post #10 for clarification. Thanks for the help Jimmy, I very much respect your knowledge on our Cobras!

 

[zonk22]

I still don't know if I should get this car re-tuned or not