So based on this, Shiv, should I purchase an adjustable FPR? I had already considered the upgraded fuel pump and possibly larger injectors. Thanks for your assistance.

Chris

 

Why would you want an adjustable FPR? Unless, of course, you wanted to do fuel tuning yourself on the dyno by adjusting the screw that preloads the FPR diaphram.

 

Unless you have a fuel pressure gauge, you won't know if you are having fuel pressure problems at idle. On dsms the 255 flows too much and the stock fpr can't flow enough fuel away from the rail to lower the pressure. The problem is also in the small diameter and restrictive fuel return line. I was just curios if the evo's fpr and return line were better equiped to handle the increased load at idle.

 

I am asking this because in a previous post you made it sound as if the stock FPR wasn't up to the task. I am trying to make my car more reliable as well as more powerful - what do I need to do to upgrade the fuel system to support ~400whp max?

 

Sorry if i wasn't clear. The stock EVO FPR is up to the task. The only thing you will need to upgrade is the pump.

Shiv

 

Thanks for the clarification, Shiv.

 

I blew a motor up utilizing a FPR without a FP gauge.

 

So you get 42 to 45psi of fuel pressure in the fuel rail with the FPR boost line disconnected from the FPR? And 33psi at idle with the FPR boost line connected?

 

Josh,

Is this a question or a probe for a response to which you already have an answer? I respect your knowledge of the 4G63 and I am getting ready to install the Walbro 255 pump for a Stage1+ car per recommendations on this forum. It seemed as though it would be a no brainer until the FPR overun issue surfaced.

What has your experience been, what is your recommendation, and why?

Thanks,

 

The FPR on the EVO is adequate unlike the one they fit to the 210 Hp DSM

 

It was a question. The same question I ask anyone who has installed a larger fuel pump.

On my DSM, the Walbro 255 overran the stock fuel pressure regulator, and I got fuel pressure creep in low load/low IDC situations. I had to install an aftermarket FPR.

I was just wondering if the measurement had been done. Some people only want to know if it is adequate. Some people want to know why.

If the measurements are the same as stock after the fuel pump upgrade, then the FPR is fine.

 

That is a very good point and I told a friend with a 1g DSM to do the 190 pump because the 255 from what I understand will over run it. I think Shiv said that it will be fine for the evo.

 

Thanks for the clarification. I, like you, would also like to know why but I bet that comparative measurements have not been done.

 

I had a fuel pressure gauge hooked up to my EVO a while back and noticed no such abberant fuel pressure irregularities after the pump upgrade. Same with the WRX. I suspect this is because modern cars have multi-speed pump systems that drive the pump slowly (lower voltage) at idle/low load and ramp them up to full spin (12v) only when needed under higher loads. I don't know if the DSMs had this. If they didn't, this could have been the cause of the "backing up" they saw with fuel pump upgrades.

My 2c,
shiv

 

Thanks for reminding me about that, Shiv. I read that in the Evo tech manual a while back, but I wasn't sure if it would be enough. The Evo Tech manual doesn't specify the resistance that is used to lower the supply voltage. It is a pretty cool feature, though, since it means heating up the fuel less when there isn't any need for it.