This is under the airbox at the back of the motor. I want to replace it because of all the corrosion, but what is it? Does not look like any regulator I have seen:


P.O. told me he installed a Kirban adjustable fuel pressure regulator, but I thought that was the front one (which I have adjusted myself):



And don't worry, the fuel gauge is going too.

((Edit: below are some motor specifics, in case it helps. Motor went through various upgrades from stock during the 2005-2007 timeframe, including block and head work by Doc Brown with final assembly in Florida:

a) 30 lb injectors

b) Kirban adjustable fuel pressure regulator.

c) head porting and multi-angle valve job on S4 valves

d) Devek Level 2 Headers

e) All-aluminum (Devek?) Radiator

f) Exhaust Air Pump delete with Euro idler in its place

g) Oil pan spacer

h) Smaller starter

i) Moldex stroker crank

))


Anyone recognize what's in the top picture? I want to replace it with a better equivalent.

Thank you, in advance!

 

That is a Kirban adjustable regulator. There is not a regulator in the front of the engine, but a damper. Should not be adjustable.

If you tell me the fuel pressure the engine is running at (vacuum to Kirbin regulator disconnected), I can send you a new design regulator, with the appropriate hoses.
I can also provide you with new dampers, calibrated for what fuel pressure you are running.

 

Thank you, Greg. I will measure that, but honestly, where ever it's at is based on my adjustment which was just a guessed bandaid placement to compensate for a lean condition before getting to SharkTuning, which has not happened yet.

The injectors are Ford Motorsports 30# injectors. Is there such a thing as a happy place for these injectors? Drivability is a priority for me and it is an Automatic, in case that helps.

Either way, I will measure.

My adjustment was a long time ago, but I would have sworn it was to that slotted protrusion at the front of the front damper? I could be mis-remembering or I could have somehow misconstrued changes to the fuel pressure at the gauge to whatever the heck I thought I was doing on that damper!

 

This item is the evaporative emissions control valve (PN 944 110 429 00). it diverts fuel vapors from the tank to the charcoal canister. It has nothing to do with fuel pressure. Either you miss remember where you adjusted the fuel pressure, or you didn't adjust the fuel pressure.

 

Thank you, FJ. I just traced the routing around it, and indeed, it ties into the 86.5 cam cover hoses.

I also found the front fuel damper Greg indicated and, sure enough, there is no adjustment on it.

All this information is a relief since I was trying to wrap my head around how two adjustments to the fuel pressure could possibly work together.

 

If you are going to Sharktune, an adjustable FPR is not only unnecessary, but not desirable
Use a standard 3.8 bar or 4.0 bar regulator, with matching dampers, and tune.

Note that.even stock dampers differ when fuel pressures change. The lower fuel pressure '85/'86 dampers are different than the higher fuel pressure '87-'95 dampers, because of the different fuel pressures. People that toss a 3.8 bar regulator onto an '85/'86 engine and don't change the dampers have pressure surge problems at various rpm's, because the dampers are not correctly matched with the fuel pressure.

 

Meh. Damper matching sounds like it could be a thing, but I never experienced any surges and no significant problems have been reported, at least by people who don't make up stuff.

 

I posted extensive ST logs and plots of the water hammer effect from mistuned injectors, pressures, and dampers...and its a somewhat understood thing in FI.

 

Allow me to propose an amazingly simple question:

Since the '85/'86 dampers are exactly the same externally as the '87 to '95 dampers, why would Porsche offer different parts for the different models?

I build replacement dampers.....built exactly like all of my products....as perfect as possible.
The "ability" to do this required me to study what the dampers actually were doing....and when....and why. (Not guess, like some do.)
The dampers control fuel pressure surges in the system....end of story.
And the difference between the different model years is internal...because of the different fuel pressures between the S3 and S4 models.

And, if you put a 3.8 bar fuel pressure regulator on an '85/'86 engine, without addressing this, the pressures in the fuel systemwill surge, causing lean mixtures at certain rpm ranges.
It's simple stuff to see, with a Sharktuner and a fuel pressure plot.

 

In the S4 Porsche could not completely eliminate resonance with their specified dampers fitted in their batch fired motor. Sharktuner dat logs when exposed on Joms Shharktuner programme demonstrate very clearly how the fuelling leans out mid cell range at two different rpm points. Start dicking around with such things blindly and the chances are the outcome is not going to be better. I doubt I would have been aware of this matter had I not had ST2 but I do and it is a real world phenomena.

If Porsche were on top of their game maybe they could have changed the cell ranges so that the narrow bands involved could have been fuelled up some to compensate- the kind of problem Ken would probably have solved. Whether or not Porsche even knew such was going on would be an interesting point of info.

 

Thank you, Greg. I believe John Speake-th of this as well. I have the updated Sharktuner 1 and I will verify that I can set it to the 87+ fuel pressure levels.

Once upon a time... when I was looking into motorcycles, I recall reading about the difficulties of bringing fuel injection to motorcycles due to surging issues causing driveability issues.

It may be that some setups are more sensitive to mismatches than others. I like the idea of a matched system, even if it is not absolutely necessary.

 

When we built our replacement dampers, we increased the volume, to help with this issue.
Even so, minor changes in fuel pressures require paying attention to the dampers.

 

Judging by the mass of S3 cars out there with the upgraded early 87 FPR, and all running perfectly well, this is not a major issue or we would all know about it.

 

While it's clear that neither Ken nor you have ever watched/recorded the pressure surges in an S3 system when running an S4 regulator. (I have.)

I'll keep it civil and simply (nicely) ask you the same exact question, that I asked Ken:
Why do you suppose that Porsche changed the dampers, when they increased the fuel pressure in the S4 engines?
Externally, the dampers are exactly the same for the S3 or S4 application.....with only internal changes for the increased fuel pressure of the S4.
Either one works in either application?
One part number (for the front damper and another part number for the rear damper) fits all the vehicles from 1985 to 1995?

A more direct question about your logic that there are lots of S3 cars working perfectly with S4 regulators, that you mention above:
Have you, all these years, sold the correct dampers for the model year of the car, or do you only sell either the '85/'86 dampers or the '87-'95 dampers to everyone?

Because, from your logic above, you are saying that it doesn't matter....


Rear dampers. S4 on left, S3 on right.
Externally, 100% exactly the same!
Interchangeable?
Not even close to accurate!
Different, internally, to deal with the difference in fuel pressure, between the two different model vehicles.
You change the fuel pressure regulators, you must change the dampers to control the fuel pressure surges.




Front dampers. S4 on left, S3 on right.
Externally, 100% exactly the same!
Interchangeable?
Not hardly!
The difference is internal, to deal with the difference in fuel pressure between the two different model vehicles.
You change the fuel pressure regulators, you must change the dampers to control the fuel pressure surges.





I'm actually kinda shocked, at this discussion....
I thought everyone knew and understood the basics about what is happening in the fuel rails!

 

The fact that the dampers are included at all speaks to Porsche's (and Bosch's) discovery that there will certainly be harmonics present in the batch-fired injection system we enjoy. There's inertia of the flowing fuel, the start-stop nature of the fuel flow, and a natural resonant frequency of the pressure regulator. Excite the regulator at the correct frequency and amplitude, and you'll see changes in local pressures at different spots in the system. The idea that you don't see the pulsations on a single gauge at a single spot in the system doesn't mean they don't happen, it just means that you didn't see them happening on that particular gauge in that spot. Consider also that bourdon tube pressure gauges are purposefully dampened with a very small restriction to prevent the tube from fracturing from pulsations. Want to see the pulses? Use an electronic pressure transducer, maybe with a piezo element (think "microphone") and monitor it electronically.

The coordination of the placement of the regulator and dampers, plus the springs used in each, is done with some serious consideration. Get one piece wrong, and the dampers can easily exacerbate the pulsations reflecting back from the pressure regulator.

In service, a system with resonant pulsations risks having fuel flow completely stop in different places in the "fuel loops". With all the injectors firing together, the problem will manifest itself as what appears to be random lean (or rich) cylinders as the local fuel pressure above an injector varies with the resonating elements. Unless you happen to be monitoring combustion temps in the individual cylinders, you may never see the power-robbing effects of the pressure and flow changes.


Moral of the story: use care when changing regulators and dampers, particularly in high-load high-flow applications. I've designed in some interesting cross-section changes in process piping to help solve destructive flow resonances and some unwanted interaction among valves. There's a whole engineering discipline dedicated to this stuff. Blind ignorance and casual assumptions are poor substitutes for a well designed system. Yes, maybe you get lucky. Enough folks don't to keep specialists busy. Unless you know more than the engineers who designed the working systems we enjoy, tread carefully when you casually adjust a piece of the system.


My two cents....