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I see you recomend this fuel pressure regulator. Is it bolt on? Which one from the website fits an 86 951? Do I need to buy anything else from this website to make it fit? Thanks a lot

 

Mark,

I have one of these in my possession but I have not yet put it on the car. I bought it used from Rob Langley on FL. I believe it is the 2022 model which is adjustable for initial pressure and for rate of rise. It has a restrictor on the vacuum line which is necessary (Rob said it went to 100psi without it. oops.) You do have to use it in-line with a stock regulator unless you modify the fuel rail. Rob mounted it on the bulkhead behind the intake manifold, I'm going to mount it on front of the battery box where the cruise motor used to be. It is a fairly large unit so that is a good spot for it and it's right above the fuel return line also. It's a really nice machined chunk of Aluminum and mine's anodized black also. I'm looking forward to trying it and seeing if it affects my fuel curve the way I want it to. Good luck.

 

Thanks, I'm glad you told me I need the restrictor. That would have been bad! Anyone else have experience installing these?

 

Over 300$ for a FPR seems to me quite expensive.I don't thing you got so much advantages to cover that price.It looks quite nice unit though!
Danno is using Bosch 3 bar FPR on Guru Racing's kits

 

Mark,

Thinking more about it, mine might be the 2025. Ask the folks who make it about the differences between those two models and get the one with more adjustment, I think that is the "aftermarket turbo" one.

Ollie,

Yes it is a bit steep, I'm glad I didn't pay that much, but it is a very nice unit and has adjustment for the rate of gain which the $160 ones don't have. I have a 3 bar with APE chips and I don't exactly like it (probably the chips fault.) I would like to try Danno's chips if I had the extra money...

 

Yeah, that's a nice FPR unit and is the only true rising-rate regulator out there. It allows you to adjust the minimum and maximum pressure (range) that is sent to the injectors. While this may be used to combat the high-end lean problems that plague modified 951s, it is difficult to adjust it just right to get a perfectly flat 12.5:1 air-fuel ratio, if that's even possible.

One thing you need to get is an electronic fuel-pressure gauge so you can monitor the fuel-pressure rise from inside the cabin. Setting static idle fuel-pressure with the vacuum disconnected can be done just like the other FPRs, but it's the transistion or 'break/knee-point' where it transitions from linear rising-pressure into rising-rate operation that you really need to adjust. Also the rate-of-rise needs to be monitored and adjusted as well.

Next comes in determining how to adjust these factors to match your car's air-flow patterns. The typical flat air-fuel curve that suddenly takes a straight-line towards lean at a 30-degree angle can be caused by two factors.

One is maxed out fuel-injectors at high-RPM (typically from 5500rpm onwards). A rising-rate FPR actually won't help this situtation at all unfortunately. That's because the FPR increases fuel with boost-pressure, however, once you hit max-boost, at say... 3500rpm, the fuel-pressure in the rail will remain constant. The only way to increase fuel-delivery is increasing the injectors' duty-cycle. But once they hit 100%, they're not going to be pumping out any more. Even worse, with the faster dropping boost-curves on modified 951s using the stock turbo, the fuel-pressure will end up dropping due the drop in boost. Combined with the injectors @100%, your mixture will get leaner and leaner as RPM and air-flow increases.

The second cause of the high-end lean tendency is improperly mapped chips for the flow patterns. This is typically caused by using AutoThority Stg.2 chips, which were mapped for a banjo-bolt restrictor modification to gain higher max-boost. But this boost drops off to normal levels after a couple seconds and 4500rpm+. The problem comes in when you use some other method of holding max-boost such as a manual-controller like the LBE, our Boost-Maximizer, a Hallman unit or an electronic controller. In this case, you'll have higher flow in the upper-RPMs than AutoThority had accounted for in their chip programming. Again, it doesn't appear that adjusting the FPR would make a difference since boost-levels would remain constant or even drop off as you encounter the high-RPM lean conditions.

If you want to use an adjustable FPR of some sort to adjust linearity of your air-fuel curve (not just shift it up and down as a whole), you'll need to devise some way to have the FPR adjust fuel-pressure based upon RPM, not boost-pressure... hmm..

 

Thanks danno! So you are saying that if I have a bigger turbo, new fuel pump and injectors, this FPR, and custom mapped chips I will be all set? I plan on doing these mods along with freeflow 3" exhaust and then having a good shop tune everything to the best of their abiltiy. I have the autothority chips so i will probably have to send them back for $100 and have them custom mapped. Does this sound good to everyone?

 

yeah, it should work out OK. You'll probably want to set the rate-of-rise to be 1.1 to 1.2x boost then do a baseline dyno run. Verify that you don't go over 80% injector duty-cycle at redline (some Fluke multimeters have injector duty-cycle function). Then send the resultant dyno-chart with air-fuel ratio curve back to AutoThority and they should be able to give you a new chip mapped for your particular configuration to get 12.5:1 across the board.

Once you've got fuel nailed down, it's time to start advancing the ignition just up to the point of knock & detonation, then back off a bit (like 1 degree).