Hmm...

 

The stock fuel pressure regulator cannot bypass enough fuel to keep the fuel pressure down to the same levels as the stock pump, because the walbro flows so much more fuel.

Brian

 

I am still wondering why Buschur Racing keeps the stock pump in their first 3 Stages(340whp/329tq). They don't change the pump until Stage 4(371whp/372tq). I also read that on Evomoto's how to on fuel pump install that you don't really need to change it until you are nearing the 325whp mark. I am not trying to start anything. I am just curious why some tuners change them early in modding and some later.

 

So what's the fix to this? Change the FPR also when changing the fuel pump or can a flash take care of it?

 

You can change to a higher quality fuel pressure regulator that can bypass more fuel volume. This will keep the fuel pressure in check even with the higher output Walbro pump.

The flash can take care of it. Al can change the open loop fuel maps to reduce the duty cycle where the car is running to rich because the fuel pressure is higher than it should be. On the top end at WOT, the car should be using enough fuel that the stock FPR can handle the return volume that is required to maintain the correct fuel pressure.

Brian

 

I don't sell walbros or have stock in them - there is no reason why I recomend them other than I want every one's evo to run well - especially my customers

 

I called up Lancershop.com and asked about the stock fuel pump. A rather knowledgeable staff there named Chris told me that the stock fuel pump flows 220lph. He said that they were not that bad stock. I have no intentions on having more then 250 whp anyways, so I dunno if the Walboro would really be a sound investment to begin with.

 

If you buy a fuel pressure gauge and occassionaly observe that the fuel rail pressure is not falling off on the top end under boost then you will never need to upgrade the pump - the bigger pump is only an insurance policy to prevent against the fuel starvation that we have seen in 6 or 7 cars so far

 

How much power were those cars making?

 

Many of them were bone stock 100%

 

 

I recall reading in one of the tuner magazines ( I think it was Modified ), that they did a fuel pump test. They included the Walbro, and the stock EVO pump along with a few other after market units. The results were that the stock EVO pump was really good, up until the very top end. I wish I could find an online copy of the article. I think everyone agrees that the extra $90 for the pump is money well spent on insurance. However, I'll have to disagree with you on how the pressure regulator and pump combo work. The stock FPR can handle the flow just fine. It isn't until you are getting into the 450+ WHP ranges that you will need to change out more than the pump from what I've read.

 

I think everybody is sweating this a little too much.

The original question was - "Do you need a reflash if you get a pump ?"
It is evolving into "Do I need a pump; is the stock one crap; is my car in danger?"

Pump problems were seen in a handful of cars for various reasons.
Does that mean that all evos are running around waiting for the engine to
grenade because of pump failure ?? Of course not.

I'm sure that 99.9% of all evos will drive on the stock pump in blissful ignorance with no problems.

Getting a pump is cheap insurance, particularly if you are modding in other areas anyway, and
you can get all your mods taken care of in one retune.

 

The stock evo pump is more than sufficient for stock or mildly modified evos - the fuel flow is ample to support up to about 300 - 310 whp

The PROBLEM is that we see the stock evo pumps either binding - wearing out or failing to put out the normal out put under certain conditions

We have seen this several times

When it happens the car runs super lean

If you have a fuel pressure gauge you will quickly spot the problem - however without a guage you may never know till its too late if your evo is one of the very few that have this condition going on

Thats why we recomend the walbro

1 - as a saftey measure to prevent the fuel starvation condition we have seen several times

2 - to provide more fuel for guys with cams that need the increased capacity

3 - to lower injector duty cycles on high whp cars

I find it strange that you have the walbro pump listed in your mods and yet you keep following me about the forums questioning my advice to replace the fuel pump

 

I agree the incidence rate is very low - and HOT climates seen to make the incidence greater

Out of 230 custom tuned Dyno Flashes - we have seen 6 or 7 cases where we wound up replacing the fuel pump and having a lean condition be resolved

The bad think is that now 90% of the custom tunes I am doing are taking my advice and we are doing almost ZERO tuning on stock fuel pumps at this time