Brett B

Hello all,

I would like to buy an adjustable fuel pressure regulator that drops into the stock fuel rail. From search it seems to be a common mod, but I haven't found anybody mentioning where to buy one. If you know a good vendor that has them in stock please post their info.

Thanks,
Brett

hal m

I got mine from ViperBob, so give him a call or send an email.

ttAmerica RoadsterAWD

I got mine from Todd Knighton, Protomotive

Jaime

ACEparts_com

Under what circumstances is it a good mod? Surely not as a stand alone mod? When does one need to upgrade?

hal m

I added mine because I went with an upgraded turbo and wanted to make certain there would be no fuel starvation issues.

Woodster

ditto, to hal for my old 993TT, not necessary for stand alone.

MK

ttAmerica RoadsterAWD

There has to be a NEED as seen by the engine. More power required more fuel, sometimes not stoichiometrically. The stock fuel maps in the stock ecu does not need a higher pressure regulator. If, however, you get a ecu remap done, along with bigger turbos, perhapse aggressive cams, then it will be wise to get a higher rating regulator.

Otherwise, it would be like strapping a Holley 750 double pumper carburator on a stock 327 engine. Too much fuel, no real NEED. Not a balanced system. Poor performance.

Geoffrey

A 5bar fuel pressure regulator will provide approximately 14% additional fuel over the stock 3.8bar fuel pressure regulator. This additional fuel is seen EVERYWHERE in the map UNLESS the ECU has been reprogrammed to account for the additional fuel added mechanically (higher fuel pressure). This means that at idle for instance where the air fuel ratio should be 14.7:1 it will now be richer by 14% which is not a good thing. O2 sensors can only trim fuel within a small range, usually 5-10 percent and then, only within a small window of air fuel ratios due to the narrow band sensors that are used in the 993tt engine.

Brett B

Thanks for the responses all. I sent a PM to ViperBob yesterday, I'll try and get ahold of Todd as well.

I should probably clarify a bit, I do not have a stock TT. I'm running a custom single turbo setup on an originally NA car. I am also running an AEM standalone ecu, so fuel map adjustments are easy. I don't want to just put in a 5 bar regulator, I would like an adjustable unit so I can set the fuel pressure where I want it. I am beginning the upgrades to the fuel system, and a drop-in adjustable regulator was one part I hadn't found yet. Here are a couple pictures of the car:

Acropora

Neat setup.

johnneurauter

totally badass! i would leave the bumper off and show the world your cookies!!! damn that's cool.

Jean

Brett,

Amazing setup.

With your Garrett GT40 turbo (?), you are good to about 500+ FWHP. Depending on your injector size, if they are the typical 44lb, the 3.8 FPR is more than enough for your setup. Cheers

ACEparts_com

We have a turbo like that up the road from me, it sit on top of a hill and when the wind blows it grinds wheat!

I would have a clear bumper made - bit like how the ferraris have for their engines.

Brett B

Thanks for the kind words guys. I did some more tuning runs last night, the car is an absolute blast. I will try and get some vids soon.

Jean, the GT4088 that I am using (65mm wheel) will actually support much more then that, but not until the built motor is done of course. Even a GT35R will support 500 rwhp on a 3.6 air cooled motor.

I am currently running 450cc/min injectors since I could get them quickly and cheaply. The 3.8 FPR is working ok for now, but I am having to increase injector duty cycles more then I should on the top end, so can tell I'm dropping rail pressure a bit. I will be going with bigger injectors and a bigger pump in the near future, so I prefer to have an adjustable regulator once those are installed. Being able to adjust the pressure up or down a bit is often advantages when running really large injectors.

Jean

Brett

You have the 88mm 0.72AR I believe?.. While agree that these turbos are huge and can flow important cfms, on these rather older cars they are limited somewhere around that HP level that I mentioned..

On these air cooled turbo engines you need to run your turbos about 70% efficiency levels, if you go below that you will be generating a lot of heat and no HP. What you get between 1.0- 1.2 Bar is 55lbs of air/min at those efficiency levels, meaning about 495 FWHP. Just remembered that you have a N/A engine, therefore you have better specific air consumption (about 10ish-11), so you can maybe see 550FWHP.

If you base the assumptions on a quick chassis dyno reading with little load, you will certainly see more than that, but the engine won't in reality, so if your injectors are close to the typical 44lbs (sorry don't know the conversion to c.c.) you will not need more than a 3.8 Bar FPR, which will put you around 570-590HP. As Geoffrey mentioned, the 5bar FPR will get you another 15% or so, and is an overkill.

I suggest you have a word with Todd K., he knows these Garretts , their threshold and fuel requirements pretty well, I am just an aficionado, I would not want to be misleading you.
Cheers
Jean