User 52121

Ok, so I know what a fuel pressure regulator is, and what it does.

Right now, my car has pretty much all the stock hardware, save for a shimmed wastegate (to "Turbo-S spec" per the previous owner, whatever THAT means), Weltmeister chip, and a 3" exhaust.

I'm assuming the stock FPR on a 951 is a 2-bar? (So it'll work up to 14.7psi?)

I'm ordering a Lindsey Boost Enhancer, just to get quicker spool-up. I don't want to add more peak boost from whatever it's already running (I know.. I know.. "get a boost gauge!") I figure, the motor was rebuilt and gone through by a reputable shop and was set up how it is, it's most likely safe the way it sits. I don't want any more power, I just want it quicker.

Do I really need to think about a 3-bar FPR if I don't plan to add more boost?

blown 944

and chips to match.

May as well go with injectors too..maf,turbo,clutch..
...
....


....... you have now fallen down the slippery
slope I'm sorry

alex_cristocea

does anyone have the bosch p/n for the 3bar FPR? Thanks

TheRealLefty

Ahhhhhh, the dark side is winning with you already, padawan This subject is always fodder for lively discussion on Rennlist. There are clearly many who would donate a major organ as a fair swap for boost at 3,000 RPM instead of 3,800. Honestly it not easy trick to conclusively obtain faster boost without more boost...but can be done obviously.

The LBE option with single port WG or a dual port WG with MDC or EBC can help control top side boost and encourage faster build up by keeping a firmer hold of the WG before it opens begins to dump boost out the exhaust. Gaining mechanical or electronic control of this function definitely works in the direction of earlier boost. Although only tested by this author with the butt dynamo, I can testify to the positive outcomes of a simple MBC controlled 38 mm dual port Tial toward this end. Good boost at 3,200 once in the upper gears at WOT.

Others can tell you more about the benefits of lower inertia in the Turbo itself, stand alone electronic systems and upgraded fuel delivery.

I think many here would be interested in some technical exchanges on your core question...making boost come on faster without investing megabucks and without turning the power unit into a hand grenade. A good 951 is just plain silly fast on the throttle, the question of better performance and enjoyment is how much power is easily available at a spirited pace.

choinga

The short answer to your question is no. If you set the LBE to boost no higher than 10-11PSI then you shouldn't need a 3BAR. For $80 or whatever it is though, not a bad idea. And dialing in 12-13 will make a difference to your 'butt dyno' vs stock.

I dunno anything about the Welt chip or what the max PSI is that it supports - presumably 15PSI. If you don't know or aren't comfortable going there then dialing in for 12PSI is safe with stock FPR. Just watch it to make sure you don't overboost by setting your LBE with your foot to the floor in 3rd and 4th gear. If you set your LBE in 1st or 2nd for 10PSI you'll be at 15-17 by 4th gear, for sure.

TurboTommy

Firstly, the stock FPR is a 2.5 bar unit.
Secondly, why do YOU think you need a 3 bar FPR?
How much fuel pressure you run has nothing to do with how much boost you're running; it has to do with what the chips are mapped for. Which brings us to the third issure: if you have a complete weltmeister chip kit it comes with the computer chip(s), the wastegate shim (which you said you had, and should give you max boost of 14 - 15 psi ), and it actually comes with a 3 bar FPR.
I think that some, or maybe all, of the bosch 3 bar units were black in colour.

User 52121

Hmmm. You bring up a good point, Tommy - maybe I should look into whether or not I already have a 3-bar FPR. Are there any easily identifiable marks?

(This is the main reason why I never bought a car in the past that was already modded... *sigh*... oh well, still love the car!)

User 52121

So if the stock unit is 2.5bar, that should be good for ~21psi. In my experience, fuel pressure alterations via an FPR are directly proportional to boost pressure, typically with a boost/vacuum line running to it. Is the 951 different? Based on my experience (I've built a lot of turbo cars, just never a 951), you'd only need a bigger FPR then if the chip was calling for >21psi boost... and with the 1:1 ratio of boost to increased fuel pressure @ the FPR, adding a 3-bar won't make a difference (below 21psi), as it'd still be a 1:1. Now if these 3-bar FPRs are actually rising rate of gain... then we're on to something different.

So why do I think I need a 3-bar FPR? I don't think I do. Based on my experience, it's not necessary unless I plan to run 20+psi (which, I don't.) I don't see very many people here running 20+ psi, either. Which makes me wonder why everyone is upgrading to a 3-bar FPR... and hence why I asked the question. Based on my past experience, it makes no sense and isn't necessary.

Now, if the 951 is just different from every other turbo car I've seen (which is entirely possible, not trying to be a smartass), then I hope to be educated here.

JohnKoaWood

Stock is unfinished metal, and is stamped 2.5 bar on the top side (visible on the car).

MY bosche 3 bar is black gloss, and has a sticker on the side, has to be read from drivers side, or with your neck all cranked over and what not...

OK, enough of my 2C...

User 52121

Dark side? Yes and no. Been there, done that. Not looking for 400hp this time. Just boost a little quicker is all. My buddy's '86 951 has the "Lindsey 270hp kit" on it, and it spools up a LOT quicker than my car. Based on my knowledge of how the boost enhancer works (I used to build 'em for $5 out of Grainger catalog parts back when I had my Omni, kills me to pay 80 bucks for one now, but eh... I'm lazy), it's mostly the boost enhancer that's helping his spool-up time.

Jusii

Part numbers http://www.alanara.fi/Possu/ENosat.html

BWM part is black and the other one looks just like stock.

Darwantae951

Do you have stock injectors?

TheRealLefty

I've had good luck with the Lindsey billet adjustable FPR. Used them on two different cars with no glitches:

http://www.lindseyracing.com/LR/Pors...S/LR-4037.html

Rogue_Ant

OmniGLH,
You are miss-understanding how the FPR works... the 2.5bar or 3bar does not indicate how much boost you can run.

Using a 2.5bar simply sets the fuel pressure to ~36.25psi.
A 3bar unit sets fuel pressure to 43.5psi.

Both are 1:1 ratio units. So every psi of boost raises fuel pressure the same. And psi below atmosphere lowers fuel pressure the same.

The [main] reason for switching to a 3bar FPR is to gain a little bit more flow from the injectors (about 10% more). But as stated before, the FPR/injectors need to match whatever the chips are setup for.


-Rogue

User 52121

No, I understand how a FPR works. Perhaps I didn't explain it clearly in my post, but I understand. As you stated, the FPR *raises* fuel pressure 1psi per 1psi of boost over a static setting. My point was, if, say, you had a FPR that could only read to 7psi, you'd be fine so long as you kept boost under 7psi, or else you won't get the proper, expected pressure increase (and therefore increase in fuel mixture) when going above 7psi. So my thought was, if the stock FPR is good for ~22psi, then why need a 3-bar that can read to 29?

But now I see what the difference is... the 3-bar has a different "0" point (that is, static fuel pressure when at 0 boost, 0 vaccuum) with higher fuel pressure @ 0 with the 3-bar. Should have thought of that possibility earlier. That makes sense, and especially why you'd need to match it to the chipset. That is the clarification I was looking for. (At least we had some interesting conversation in the meantime ) I was thinking that the 2-bar and 3-bar had the same pressure @ 0, just with a wider range on the 3-bar.

From the looks of my car, and the descriptions here in this thread, I have a stock FPR. I dug around on the Weltmeister site, and I think the chip that includes a new FPR is for the "S" cars ('88 TS and '89 T.) So most likely, my car's chipset is expecting a stock FPR. It runs a little fat anyways, based on the occasional whiff of exhaust I get.

I'm fairly certain my car has stock injectors. Poking through the receipts, I don't see anything that points to updated injectors. Are these things typically running close to max duty cycle stock? Is that why most chips expect you to run a 3-bar FPR - not a lot of headroom on the injectors to add more fuel?