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fuel system

mountaineerjeff

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Oct 21, 2008
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west virginia
is it safe to run 550s on a stock fuel system? id still be running stock boost.
im having keydiver make me a chip to take car of the injectors, I just wasnt sure if they would run fine on stock fpr and pump.

second question, I have a new pump, ( currently MIA), can I install it one my stock fpr if I am also continueing to run stock boost? the pump is a wally 255

If not then ill have the chip made to run with my 450s until I can get a AFPR

thanks
 

prove_it

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You'll be fine. You can run any injector you want with, as long as you reprogram the ecu, since you said you are, your good there.
Go ahead and install the pump once you find it too. Your stock regulator will be fine. It will still return excessive fuel the same way. Upgrading the fuel regulator is really only needed once you hit high power levels or change to E85. Or I guess if you didn't want to change to ecu to add more fuel then you can run a raising rate regulator.
So yea, run the 550's and your pump with the keydiver chip and you'll be happy. You won't notice any bad effects.
 

4orced4door

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The 550s are fine, the 255 will overrun the stock FPR. You'll notice decreased mileage, but just crank up the boost to compensate for it. This is a very typical upgrade path.
 

beaner

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The problem with a 255lph and the stock regulator is you get inconsistent fuel pressure at different loads/rpm. You simply can't tune it out because it's never the same, it all depends on load and RPM of the engine. Load and RPM are infinitely variable so it's just not possible to tune it out with a chip or AFC.

When you have a 255lph pump you need an AFPR. You should not buy the pump with out the regulator. Thats like rims without tires. Just because you can put the rims on and maybe get the car to move, doesn't mean thats the way it's supposed to be.
 

4orced4door

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That's a good point, it's definitely not easy to tune that way. But it's also possible to "get by" just fine, like that. But an AFPR should be one of your next mods.
 

mountaineerjeff

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Quoting Beaner:
The problem with a 255lph and the stock regulator is you get inconsistent fuel pressure at different loads/rpm. You simply can't tune it out because it's never the same, it all depends on load and RPM of the engine. Load and RPM are infinitely variable so it's just not possible to tune it out with a chip or AFC.

When you have a 255lph pump you need an AFPR. You should not buy the pump with out the regulator. Thats like rims without tires. Just because you can put the rims on and maybe get the car to move, doesn't mean thats the way it's supposed to be.




this is exactly what I thought. I got the pump cheap, so I bought it, but I havent got a AFPR yet, thats why I was wondering if I could use the pump. but I guess the answer is no. so my new pump will over run my stock AFPR. and I know that injectors overun the stock pump. but everyone agrees that I wont have a problem with stock fuel system with 550s, right?

Im also upgrading to an evo mas with 3" intake at the same time, I dont know if this needs to be taken into consideration for the fuel or not.
 

4orced4door

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You might lean out with the 550s and the stock pump if you are running a lot of boost or running the 550s close to max DC.

I personally would get the chip setup for the 255 and 550s, and keep the boost around 16-18 or so. Then when you get the AFPR, you don't have to reburn your chip, and you can up the boost some more and properly tune with an AFC or whatever.

The Evo MAS and larger intake will increase the flow of air which needs to be compensated for with more fuel. Your tired stock pump may not be up to the job. Be sure and keep the boost low until you upgrade the pump, or at least watch knock closely.
 

mountaineerjeff

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well the boost will remain at stock.will I have a knock, or lean problem on stock boost?
 

prove_it

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Quoting Beaner:
The problem with a 255lph and the stock regulator is you get inconsistent fuel pressure at different loads/rpm. You simply can't tune it out because it's never the same, it all depends on load and RPM of the engine. Load and RPM are infinitely variable so it's just not possible to tune it out with a chip or AFC.

When you have a 255lph pump you need an AFPR. You should not buy the pump with out the regulator. Thats like rims without tires. Just because you can put the rims on and maybe get the car to move, doesn't mean thats the way it's supposed to be.



I guess I didn't realize that our cars had variable fuel pump control and variable pressure regulators. Wait a minute, we don't. The pump runs at a constant pressure/volume. The pump speed doesn't speed up and slow down. Also the regulator is a closed, open valve, it doesn't vary with load. ONLY under vacuum does it reduce pressure. Now I'm not saying that you can't overrun the regulator, BUT it is completely controllable and tunable. Worse case scenario is it runs a bit more pressure and you run a bit richer. Better scenario than not having enough fuel and going lean! Around my city here there are more TEL's running around than anything else. I've installed 255 pumps with stock pressure regulators before on several cars. Guess what I tuned them all. They ran fine. They ran solid air fuel through all gears at WOT and cruise.
In other words, go for the injectors and pump. You'll be just fine, just don't goodyear do the work. /ubbthreads/images/graemlins/wink.gif
 

mountaineerjeff

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what they are saying is that the valve cant hold the pressure of the new pump. the stronger pump overpowers the 20 year old regulator. then you have spikes and surges.

around here we dont go by how many times it has worked, we go by how many times it failed. if it CAN mess it up, and you are fine without it, then why do it?
 

prove_it

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I've never seen them fail
 

Barnes

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Well. 'Prove_it' has not really done his job. Sure you can put a 255 in without an AFPR, but it is NOT recommended. The car will behave much better with the AFPR on the 255 pump.
 

Quoting prove_it:
Now I'm not saying that you can't overrun the regulator, BUT it is completely controllable and tunable.



You are giving out bad information here. It is very well documented that the stock FPR has too tiny of an orifice inside to return enough fuel to the tank fast enough to avoid overrun with anything but a stock pump. Even my dinky Denso 165 lph overran my stock FPR. I had the same fuel pressure with the vacuum line on or off.
It has nothing to do with the valve inside, or the spring. Its completely an issue with the size of the hole that the fuel has to squeeze through to get to the return line. It is VERY, VERY small! /ubbthreads/images/graemlins/banghead.gif
 

icurunnin

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Fort Worth Tx
I know that my TRE 255lph fuel pump over ran my stock fpr very quickly. It was at the point where I almost didnt make it home from running so damn rich. it was bucking and wouldnt idle for crap within the first 5 minutes of install. When I pulled the pump back out it was VERY hot and had a ton of pressure that backed up.
As soon as I put the stock pump back in all my problems went away. I then installed the TRE with a aeromotive afpr and had no problem at all.
Point being, listen to who you want but if the guy who is programming your chip is also telling you that you will over run the stock fpr then take that into consideration.
 

prove_it

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didn't realize people have had problems. We've dyno'd a few cars that were running the stock regulator, and they turned out ok. Both second gens and first gens. That's why i love this forum, even when you a lot you can still learn new things and not get beaten down about it.
 

belize1334

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Prove_It: You are spreading false information. Due some research on the subject before you start commenting.

At high loads there is no issue since you're using most of the fuel coming from the pump so the regulator is only having to bypass a small volume. The issue is driveability at low loads when you're not using much fuel. Then the regulator is having to bypass most of it. With a large pump this is an issue because the orifice is too small and the fuel pressure becomes uncontrollably high. If you have a speed density setup it doesn't matter since you tune based on load and rpm anyway and those are the things that will affect the overrun condition. BUT, if you're running an airflow type ECU (like the stock ECU or MAFT or ECMLink) you will not be able to tune it out and you WILL have to get an AFPR to make it work.
 

Barnes

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Quote:
At high loads there is no issue since you're using most of the fuel coming from the pump so the regulator is only having to bypass a small volume. The issue is driveability at low loads when you're not using much fuel. Then the regulator is having to bypass most of it. With a large pump this is an issue because the orifice is too small and the fuel pressure becomes uncontrollably high.



+Juan
 

mountaineerjeff

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Oct 21, 2008
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west virginia
well my 550s fell through, and I thought I found a set of evo 560s but that didnt go as planned either. I threw up a WTB ad. but anyone got a set of old evo 560s around? I thought Id have a set so I got keydiver making a chip for them. I got 135, but thats it, so i need like 20 to get new seals. somebody help me out.
 

prove_it

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Keep an eye out for deals on the evo forums and dsm forums. If I see something I'll let you know.
 
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