Options for Adjustable Fuel Pressure Regulator

[tig]

I want an adjustable fuel pressure regulator for my '87 535is (Vlad). The current motor is a stock M30B34 (with headers). My dyno runs today show that it is running lean, even with the stock 059 ECU and AFM.

I don't really need it for this engine except for academic reasons.

But I probably will for my M30B35 which will be 10:1 compression and will use 24lbs injectors. Since this whole escapade is about learning, I've decided I want to get one along with a wideband gauge.

I've searched around for AFPRs and found the following:

• Apparently BavAuto used to sell one; I can't find one on their site now.
• Ireland Engineering sells one. $165. Says something about 'remote mounting' due to engine bay clearance issues. http://www.iemotorsport.com/bmw/E28-E24 ... djreg.html
• One thread mentioned Bell, and that its the original and best. $229. http://www.bellengineering.net/product_ ... ducts_id=2
• A guy at a local tuner shop recommended Aeromotive. They have several different models. I think the 13101 will work. Base pressure adjustable from 40-75 PSI. - $158 on Amazon.
• There's also an option for the Aeromotive 13129 regulator, which is only $118 on Amazon. "30-70 PSI and fuel pressure rises on a 1:1 ratio with boost."

The IE and Aueromotive 13101 units are about the same price. The IE unit looks more home-grown but comes with all that hardware for 'remote mounting', which I think is for an E30. I'll buy a dial indicator too, like this one.

I don't know what the "A1000" in the 13101 stands for. Anyone?

Any other suggestions>

Are any of these NOT going to work (e.g. physical fitment or basic incompatibility)?

I also plan on getting a AEM EUGO wideband gauge but that's a different subject.

(I've searched and there's no good, recent info on this topic so I'm starting a new thread).

[pldlnr]

There are a couple of ways to enrich the mixture. Raising fuel pressure is one of them. Have you checked the output of your AFM signal? You can always loosen the mainspring inside the AFM to enrich the mixture. I recently did it with my 533i to improve a lean mixture. I would find a spare AFM. You may already have a spare if one came with your b35. Loosen the spring one or two clicks and see what happens. You may need to adjust the idle mixture after loosening the spring, though.

I ran an adjustable regulator on my e34 535i for a while. The car has a Schrick 284/280 and a few other mods. It was the Bav Auto Regulator and I found it to be a piece of junk. I put a stock regulator back on it and tuned the AFM and the car feels better than ever.

[tig]

There are a couple of ways to enrich the mixture. Raising fuel pressure is one of them. Have you checked the output of your AFM signal? You can always loosen the mainspring inside the AFM to enrich the mixture. I recently did it with my 533i to improve a lean mixture. I would find a spare AFM. You may already have a spare if one came with your b35. Loosen the spring one or two clicks and see what happens. You may need to adjust the idle mixture after loosening the spring, though.

I ran an adjustable regulator on my e34 535i for a while. The car has a Schrick 284/280 and a few other mods. It was the Bav Auto Regulator and I found it to be a piece of junk. I put a stock regulator back on it and tuned the AFM and the car feels better than ever.

Thanks Paul. I'll post all the deets later but I ran two different AFMs and the Miller MAF on the dyno today, and they all were lean. The MAF the worst of the bunch, FWIW.

[TodB]

I've got the one from Ireland engineering and it works great. My motor is modded a bit including a miller MAF and warchip. I run 50 PSI.

It does require remote mounting which looks a bit fast and furious but its nice to see the actual pressure when you are adjusting it and the adjustment and mounting is easy. The only drawback is that it comes with piece of crappy fuel hose to use. Get a good piece.

[foolish]

I have a lightly used IE unit for sale.

[tig]

I've got the one from Ireland engineering and it works great. My motor is modded a bit including a miller MAF and warchip. I run 50 PSI.

It does require remote mounting which looks a bit fast and furious but its nice to see the actual pressure when you are adjusting it and the adjustment and mounting is easy. The only drawback is that it comes with piece of crappy fuel hose to use. Get a good piece.

Any chance you could post pics of your setup?

[TodB]

PM sent

[WVe28]

Sorry for resurrecting this thread from the dead but I wanted to throw another option on here from a source that has never been mentioned on MyE28 before.

I have been looking for a while for an adjustable FPR and one of my goals was to maintain a somewhat stock look, which some of the ones out there (IE) do not allow. I came across a model from Kirban Performance that seems like it will fit the bill. I ordered mine today, so I'll have to report back with my review at some point, but I have a feeling several of you will be interested.

Features:
Direct replacement for stock regulator on M10/M20 and M30 engines/fuel rails.
100% American made.
100% all billet aluminum construction.
100% rebuild-able.
Viton 3-layer diaphragm rated at 100 psi constant and 300 psi burst.
Totally adjustable from 30 psi to 100 psi.
Separate vacuum port, no removing the line to adjust.

Cost was $149.95 + $14 shipping.

The product number is 4037. They do not list it on their website but promptly replied to my request when I inquired via their website contact form.
You can also contact them directly via christina@kirbanperformance.com.


*NOT MY ENGINE* vv

[Ju@n]

Looks stockish! Might need a coat of black paint to make it invisible
A question while we're talking FPRs, something I never understood, a FPR manages fuel return to maintain a certain pressure differencial between the intake manifold and the fuel rail, right? When one goes possitive pressure, does the stock FPR maintain that differential? or does it only work on negative/equal pressure?

[WVe28]

A question while we're talking FPRs, something I never understood, a FPR manages fuel return to maintain a certain pressure differencial between the intake manifold and the fuel rail, right? When one goes possitive pressure, does the stock FPR maintain that differential? or does it only work on negative/equal pressure?

A properly-functioning FPR should work both ways on a 1:1 ratio. Under vacuum the fuel is being pulled from the injectors at less than atmosphere so fuel pressure is lowered so as to not overfuel. Conversely, under boost the fuel is being pushed back into the injector so pressure must be increased at the rail to maintain the constant flow. The only time the FPR is at exactly its rated pressure is at atmosphere (full throttle on a naturally aspirated engine and/or engine off, fuel pump running).

[Ju@n]

A question while we're talking FPRs, something I never understood, a FPR manages fuel return to maintain a certain pressure differencial between the intake manifold and the fuel rail, right? When one goes possitive pressure, does the stock FPR maintain that differential? or does it only work on negative/equal pressure?

A properly-functioning FPR should work both ways on a 1:1 ratio. Under vacuum the fuel is being pulled from the injectors at less than atmosphere so fuel pressure is lowered so as to not overfuel. Conversely, under boost the fuel is being pushed back into the injector so pressure must be increased at the rail to maintain the constant flow. The only time the FPR is at exactly its rated pressure is at atmosphere (full throttle on a naturally aspirated engine and/or engine off, fuel pump running).

Is there a top or bottom limit to this?

[WVe28]

Is there a top or bottom limit to this?

Theoretically, of course. But unless you’re pushing past 5 or 600 HP on a stock FPR I can’t imagine you’d ever hit it. Normal vacuum on a healthy engine is generally less than 11 psi so any regulator should handle that with ease. In the above adjustable FPR, it’s rated for 100 psi constant and 300 burst, so you could run 70 psi and 25 lbs of boost and not come close to maxing out the regulator. Maybe some of the high-power turbo guys can chime in if they’ve ever busted one, but I’d imagine if you had spent the money to produce that much power, you probably upgraded the FPR along the way.

[Ju@n]

Great! thanks Chris that cleared my doubts

[tig]

Sorry for resurrecting this thread from the dead but I wanted to throw another option on here from a source that has never been mentioned on MyE28 before.

As the official thread starter I fully support your hijack. I'm eager to hear what you find out.

[MrZ]

Bump for a follow up on this.

[WVe28]

The Kirban FPR was a straight bolt-on swap and works great.

I highly recommend it.

[MrZ]

Righteous, just send them an email.