crazy afpr?? (rich down low perfect up top)

[byebyev8]

I set the base pressure to 43psi with the vacum line off on my 2g, because when I first installed it, it was set to 20psi. Crazy part at lower psi the car runs richer at idle when I raise the pressure it runs leaner. Which seem to be the opposite, WOT AFR's are pretty much the same at all the pressure's I've set it at. Only difference at 43psi base than around 30base was at 43psi the car runs pig rich when I first get on it, were at the lower levels it's around 10.5 when I first get on it. This is 28+psi on e85 with the arf set at 12.1. Yes I have reset the ecu

 

[GVR4592]

What are you using for a vacuum source for the regulator?

 

[forcefed86]

I set the base pressure to 43psi with the vacum line off on my 2g, because when I first installed it, it was set to 20psi. Crazy part at lower psi the car runs richer at idle when I raise the pressure it runs leaner. Which seem to be the opposite, WOT AFR's are pretty much the same at all the pressure's I've set it at. Only difference at 43psi base than around 30base was at 43psi the car runs pig rich when I first get on it, were at the lower levels it's around 10.5 when I first get on it. This is 28+psi on e85 with the arf set at 12.1. Yes I have reset the ecu

It all has to do with injector dead time and chip settings. It is more difficult for the injector to pulse at higher pressures. This will slow down the injector.(leaning it out) This is especially noticable at idle.

WOT AFR's should not be anywhere near the same unless your ECU is "trimming" out the changes made. Set base pressure to the reccommended settings on your chip, tune fuel trims to 100 from there.

 

[95blackGsTurbo]

Here is an idea. Bolt on the stock regulator and run that. As long as it is in decent shape it will be fine.

 

[forcefed86]

Here is an idea. Bolt on the stock regulator and run that. As long as it is in decent shape it will be fine.

Ever had a gauge on your car with the stock regulator? Base pressure is really high due to teh tiny restrictor in the returnline.

This may work well with E85, due to the high demand for fuel at idle. This is what I was told by many reliable sources anyway. I still never bothered to put a gauge on my stocker. But When I installed my AFPR I had to richen up the idle quite a bit.

 

[95blackGsTurbo]

Ever had a gauge on your car with the stock regulator? Base pressure is really high due to teh tiny restrictor in the returnline.

This may work well with E85, due to the high demand for fuel at idle. This is what I was told by many reliable sources anyway. I still never bothered to put a gauge on my stocker. But When I installed my AFPR I had to richen up the idle quite a bit.

Why yes I do thank you for asking. I have a gauge on my filter. I am aware of the restrictor in the return line and people's want to modify it. I am not currently on E85. Just on pump gas with a 255hp. No problems at all. The problem arises from a weak spring/diaphragm that causes this "overrun" condition. If you get the "overrun" condition, simply replace it with a new OEM one.

 

[forcefed86]

Why yes I do thank you for asking. I have a gauge on my filter. I am aware of the restrictor in the return line and people's want to modify it. I am not currently on E85. Just on pump gas with a 255hp. No problems at all. The problem arises from a weak spring/diaphragm that causes this "overrun" condition. If you get the "overrun" condition, simply replace it with a new OEM one.

Not trying to be rude, I was just curious what the pressures were.

After seeing this picture. It makes sense to me that factory FPR would cause excessivly high pressures with a larger pump. Not saying it did 100%. Just that it made sense. What kind of pressure do you see at idle?

Thanks!

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[95blackGsTurbo]

Dead on 43psi. That restrictor can cause problems. But if the spring and diaphragm are in proper working condition. It doesn't have a problem. An EVO and 2g FPR are almost identical. Little outside difference but the same inside. There are guys running dual 255hp's with no issues, 255hp with an inline and big inline pumps with no pressure issues at all. Mostly because the regulator in those cars are almost 10 years newer.

 

[forcefed86]

Dead on 43psi. That restrictor can cause problems. But if the spring and diaphragm are in proper working condition. It doesn't have a problem. An EVO and 2g FPR are almost identical. Little outside difference but the same inside. There are guys running dual 255hp's with no issues, 255hp with an inline and big inline pumps with no pressure issues at all. Mostly because the regulator in those cars are almost 10 years newer.

Is there any advantage running that high of a base FP? Seems to me if your going to spike past 30psi or so you'd be right on the ragged edge of the 255HP's max pressure. Not to mention as pressure goes up flow goes down on the 255. Then there's wear and tear from excessive pressure on the pump, injectors, FPR etc...

Again, not trying to be rude here. Just getting some opinions. It's not like 10psi or so is going to make or break a pump, but every little bit helps. In a perfect world I'd like to use the minimal amount of FP required to get the job done?

Just a thought...

Here is an example of what I was stalking about. Obviously the numbers will be higher at higher voltages. But you can see a healthy drop as pressure increases.

Walbro "255 High Pressure" LPH GSS-342 12.5V 43psi 7amps 233.4 Ltr/Hr
Walbro "255 High Pressure" LPH GSS-342 12.5V 58psi 9amps 210.10 Ltr/Hr
Walbro "255 High Pressure" LPH GSS-342 12.5V 73psi 10.5amps 189.3 Ltr/Hr

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[95blackGsTurbo]

Yes this is true and I have quoted that chart before to people trying to run 60psi base fuel pressure instead of buying the proper upgrades. Industry standard is 43.5psi. That is what everything is flow tested at pretty much. So in this case there is no real issue with a 255hp. If you are making enough power to max out the pump at 43psi, your making enough to max it out at 37psi. If the OP wants to though, he can just purchase a new OEM 1g regulator. They have a weaker spring so are more prone to going bad.

 

[forcefed86]

Yes this is true and I have quoted that chart before to people trying to run 60psi base fuel pressure instead of buying the proper upgrades. Industry standard is 43.5psi. That is what everything is flow tested at pretty much. So in this case there is no real issue with a 255hp. If you are making enough power to max out the pump at 43psi, your making enough to max it out at 37psi. If the OP wants to though, he can just purchase a new OEM 1g regulator. They have a weaker spring so are more prone to going bad.

I can agree with that.

But when you have a adjustable FPR and know your going to be pushing 30+psi, I don't see any problem with setting your base FP at 30psi. It's where I've run mine on my grand national for years now. The difference in flow between 60psi and 75psi is quite a bit.

I'm not saying anything you said was wrong and I really not trying to prove any kind of point. Just wondering what the "Ideal" setup would be.

 

[95blackGsTurbo]

Ideally yes, but if it can save him $200 to spend elsewhere on the car I am all for it. I am sure the vendors aren't too happy to hear all of this about not NEEDING an AFPR since they have so many kits available.

 

[bsbllfit7]

so all your saying is that i need to get a new oem fpr? Im about to upgrade to a 255 and was contemplating which afpr to get. lemme know asap please!

 

[DSMDirkah]

To the OP:

I would be interested in what the o2 trims are when this is happening. You might be past the point of correction through the ECU. Still would not think that it would swing AFR's in that manner. Give more detail of exactly what AFR corresponds to what. Is the o2 sweeping properly?

I agree on the stock FPR. I can vouch that the stock FPR can control a walboro 255. I have also seen a car where the FP over ran the stock one. They are just getting old and raggety.

The question about the advantages of running a higher fuel pressure:

I have noticed that with some big injectors, it is good to run a bit higher than stock fuel pressure for better atomization qualities at idle. It really depends on the injector and car though.

 

[rstchris]

The gss342 will make 115psi, I found that out on an rs with an fmu. It takes a LOT to make a wally want to fail and most injectors won't jam until over 95psi. I have seen 5 wally 255hp pumps on 2 1g and 3 2g stock fpr with no idle fuel pressure issues. I hear all the time "oh if you got a wally 255 you gonna need an afpr bro unless you get the 190lph" Raising base fuel pressure is a great way of making overhead as long as you don't get carried away. Back in the day it was the only affordable way of boosting n/a's.