Changing stock fuel pump for a 255 lph, do I need a new tune?
01-03-2008, 09:18 AM
#1
Changing stock fuel pump for a 255 lph, do I need a new tune? Will I need a new tune/would I benefit from a new tune from changing out the stock fuel pump for a Walbro 255 lph in tank pump?
I am guessing most will say it won't be worth the cost, but thats not what I am interested in. I need to know if it would hurt me at all from doing it and not getting it re-tuned, or if it would benefit me any more power.
I am guessing most will say it won't be worth the cost, but thats not what I am interested in. I need to know if it would hurt me at all from doing it and not getting it re-tuned, or if it would benefit me any more power.
01-03-2008, 02:06 PM
#5
Anyone have knowledge on this?
01-03-2008, 02:17 PM
#6
Why would it run rich though? Your fuel pressure regulator should keep the fuel pressure constant no matter what the pump is should it not? I am not sure on this, but as I understand it, the PCM will tell the regulator what fuel pressure is needed, then it is up to the pump to keep up with the demands.
Anyone have knowledge on this?
Anyone have knowledge on this?
The PCM doesn't tell the regulator what pressure to put out. The regulator is a mechanical piece that sits back in the tank and regulates the pressure at the fuel rails from the back of the car. From my personal experience, it doesn't do a good job of it.
2. Search.
There are a lot of people that report seeing higher rail pressure after switching to a higher output fuel pump.
3. Experiment.
Install a fuel pressure gauge that you can watch as you go WOT, and you might be surprised at what you see (most likely a drop in pressure at WOT). You can use that same gauge to see what your pressure is before the pump swap, and after. If the pressure has changed more than 1 psi or so, you need a retune.
01-03-2008, 02:40 PM
#7
Instead of Stop, Search and Experimenting, I'd rather just get the info from people that have experience on this and who would know (lol). You say "from your personal experience" the stock regulator doesn't keep fuel pressure constant. Can anyone else back this up? I guess I have never heard of the LS1 regulators not keeping fuel pressure constant.
There has to be evidence or someone who knows for certain that if by installing a new fuel pump it will change the fuel pressure for sure. If it does so in one car, it should do it in all cars given that everything is working properly. I'm not going to go buy a fuel pressure gauge and install it just to find out.
The whole reason I ask this is because I plan on getting a tune with mods I plan on doing in the spring, and I haven't decided if I am going to go with a 255 lph fuel pump yet or not. If it is a fact that by installing the pump after the tune it will throw the tune off, then I will just install it prior to the tune, however if it won't change anything, then I would rather do it later.
Does anyone else have info on this?
There has to be evidence or someone who knows for certain that if by installing a new fuel pump it will change the fuel pressure for sure. If it does so in one car, it should do it in all cars given that everything is working properly. I'm not going to go buy a fuel pressure gauge and install it just to find out.
The whole reason I ask this is because I plan on getting a tune with mods I plan on doing in the spring, and I haven't decided if I am going to go with a 255 lph fuel pump yet or not. If it is a fact that by installing the pump after the tune it will throw the tune off, then I will just install it prior to the tune, however if it won't change anything, then I would rather do it later.
Does anyone else have info on this?
1. Stop.
The PCM doesn't tell the regulator what pressure to put out. The regulator is a mechanical piece that sits back in the tank and regulates the pressure at the fuel rails from the back of the car. From my personal experience, it doesn't do a good job of it.
2. Search.
There are a lot of people that report seeing higher rail pressure after switching to a higher output fuel pump.
3. Experiment.
Install a fuel pressure gauge that you can watch as you go WOT, and you might be surprised at what you see (most likely a drop in pressure at WOT). You can use that same gauge to see what your pressure is before the pump swap, and after. If the pressure has changed more than 1 psi or so, you need a retune.
The PCM doesn't tell the regulator what pressure to put out. The regulator is a mechanical piece that sits back in the tank and regulates the pressure at the fuel rails from the back of the car. From my personal experience, it doesn't do a good job of it.
2. Search.
There are a lot of people that report seeing higher rail pressure after switching to a higher output fuel pump.
3. Experiment.
Install a fuel pressure gauge that you can watch as you go WOT, and you might be surprised at what you see (most likely a drop in pressure at WOT). You can use that same gauge to see what your pressure is before the pump swap, and after. If the pressure has changed more than 1 psi or so, you need a retune.
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01-03-2008, 06:54 PM
#14
Given that mine has been consistant in running well, it should act how they all should act given that they are running properly. This shouldn't be a "can't tell for sure" thing. Changing a good working stock fuel pump for a Walbro 255 lph will either increase your fuel pressure or it won't. I don't see how it can be a "maybe, but not for sure" thing.
01-07-2008, 03:49 PM
#16
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Do you think that a pressure difference might only show up on a car with bigger rails or injectors, or maybe that a massed produced factory pump may drop a couple PSI on one car and not another. Or maybe that if someone had a nearly stock car as I assume you do that the only reason they put a 255 in is because their stock pump went bad and they couldn't check initial pressure? What are your exact mods-that could make a difference... maybe, but I'm not sure!
01-07-2008, 04:32 PM
#17
The way I see it, the fuel pressure regulator should keep it at a constant fuel pressure. However, since you are not putting a stock pump back in, and one capable of a much higher flow rate, it is possible (and seems to be the norm from what I am hearing) that the stock fuel pressure regulator has a hard time regulating the fuel pressure to that of where the stock fuel pressure was with the stock pump.
Basically, I am going to get at tune after the fuel pump installation just to be on the safe side.
Basically, I am going to get at tune after the fuel pump installation just to be on the safe side.
01-08-2008, 09:02 AM
#18
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Yes, it will increase fuel pressure... and yes, it will make the car run rich... install it just before getting the tune - you will be fine for a short time of part throttle driving as the O2s will lean it out where it should be once it goes into closed loop... how's that for a straight answer 
01-08-2008, 09:07 AM
#19
Yes, it will increase fuel pressure... and yes, it will make the car run rich... install it just before getting the tune - you will be fine for a short time of part throttle driving as the O2s will lean it out where it should be once it goes into closed loop... how's that for a straight answer
