mpsig226

Hi everyone! Just kicking the idea of upgrading my fuel pressure regulator. I have a 2003 996 TT that just turned 30K miles. Engine/Trans are out. I'm sent my turbos K16's to gpops for rebuilding and upgrading to billets. Car has GT2 intercoolers, Evo diverters/intake system. Fabspeed GT2 single piece muffler and 100 CEL Cats. I read someone upgraded fuel pressure regulator to 5 Bar but not sure if injectors were upgraded as well. I believe mine are stock and am not contemplating on upgrading. 5 BAR regulator may give me a little more umph. I also read somewhere that upgrading the N75 valve to a VW/Audi 06A-145-710-N or newer will improve lag and boost. Clutch is very strong, original. Any and all comments are welcome. Thanks !!!

2fcknfst

This should be a good thread; I asked the same question awhile ago and there seem to be two schools of thought on this;

1) Peeps seem to like the upgrading of injectors to 1600cc units. This requires programming and is expensive.

2) The same/new injector matched to the engine (in my case Bosch 0280158117) and a 5 bar FPR (Bosch 0280B02722-03) which works well within the original design of the engines fuel system.

If you plan big power, I think the fuel system (pump, injector, regulator) need to be looked at as a whole rather than single pieces. If you want reliability and are going to stay under 600hp (Like me!) new injectors and a slightly higher pressure FPR are a way more cost effective solution, that is inline with goals and daily driving duties.

32krazy!

5 bar is a band aid . if your motor is out upgrade the injectors and do it right the first time

s65e90

Yea if the motor is coming out, leave the stock FPR and just upgrade the injectors. Guys upgrade to the 5 bar as a way to bump the pressure up on stock injectors.

2fcknfst

I did say injectors AND FPR...

The fellows at Bosch did recommend the injector part number as well as a new FPR, part number also attached.

mpsig226

Cool guys, FPR and Injectors. I had already planned to send my 3rd gear data pulls to have it programmed. Much appreciated, even got the part numbers!

32krazy!

If your upgrading inj stay with a 3.8 fpr

2fcknfst

How does that work? The replacement injector I noted from Bosch is a 52lb unit, versus the 44lb unit that came with the car originally - going to a 5 bar fpr may not add any power, but does add a level of serviceability/reliability to an injector that is almost 25% larger than originally designed.

Additionally, if you chip the car (any car for that matter with a turbo...) and up the boost, the rest of the fuel system has to step up to the new ecu demands, which most certainly is now performing outside of what Porsche had in mind.

32krazy!

stay with oem fpr on oem dme with upgraded inj. adding a 5 bar to larger inj puts a larger strain on the fuel pump. just add 1300 cc inj and sclae them for driveability. any competent tuner can do this. no need to run 70 psi fuel pressure for 5-600 hp

oem fpr is at approx 55 psi plenty of pressure for most upgrades up to 1300 cc inj.

2fcknfst

The fpr is vacuum controlled; more load equals a rise in fuel pressure, and a 5 bar regulator will behave exactly the same way as a 3.8, but will be more reliable when you ask the car to produce 25% more power. I do not understand how a scaled 1300cc injector can work properly at this level when only being called upon for a 30% duty cycle, not to mention the fundamental change in asking an injector this big to perform at the same level with only a 55psi feed to it; in order to maintain reasonable, efficient, atomization with a 1300cc injector working at a 30% duty cycle, one would think the more pressure behind that injector, the better.

I am not sold on this practice. One, because of the cost, and two, because I am not seeing an engineered solution - you speak of adding a 5 bar fpr as a 'band aid', however, the numbers at the 575/600hp level actually support going to a 52lb injector and a higher operating pressure (better atomization/higher duty cycle of the injector/reliable fuel delivery at high or sustained load) - this would not have an adverse effect on the fuel pump, nor would it impact the fuel coolers ability to keep up, versus throwing in a grossly oversized injector and scaling it through software - pretty daring, and hard to track (changes and impacts on the rest of the connected system, not race...)

What I could understand is using a large injector to aid in cylinder cooling for high horsepower applications where efficiency isn't a great concern; I have a 2.5l boxer with a GT35 turbo on it that once made silly amounts of power until I blew it up, then during the rebuild, in order to avoid the lean condition that killed it the first time, I dialed back the boost and used a 1000cc injector intentionally set to run 'richer' in normal driving in order to help keep the temps down. Now, this works, and is reliable, but my mileage is in the toilet. In this application, I am running 68psi fuel pressure through an adjustable fpr with a Walboro 450lph fuel pump, with no fuel cooler. The duty cycle of the injector, under load, is in the 79 to 86% range at 21psi (1.5 bar) of boost - and there is still tons of soot in my exhaust!

So, help a guy out and please explain to me how just plugging in a 1300cc injector in place of where a 440cc injector once sat, applying software and expecting it to operate as it did when it was stock - it just doesn't seem to add up to me.

mpsig226

This changes the whole "enchilada". I will need to wait and see more chimes to decide what to change or just leave it stock (little fun). I want to be on the safe side regarding upgrades or no change at all. 550 HP and torque to go with it would be nice though. These cars are designed with modifications allowed (if desired), driven hard, and enjoyed.

32krazy!

When you add a 5 bar you are still pushing more fuel thru a small inj. You will Inc flow slightly to approx 550cc from the 480cc inj but your pushing it beyond safe idc which should stay at no more than 85%. Using a 5 bar also strains the single small pump in the tank and unnecessary adds heat to the fuel. Using larger inj gives you the headroom needed without inc flow and stressing the pump. Scaling inj to run as a 480 would is no issue. I suggest 1300 since mods change. I started at oem went 72 lbs then 1300 then 2000. Major pain to swap out. Remember you may Inc flow but the lines are still small and pressure is building. FWIW I run 55psi base pressure 2000cc inj an8 lines and twin walbro 485 pumps with a Weldon adj fpr and car isles and drives like oem .

2fcknfst

So then, you would fall into the 'heavily modified' category. That certainly makes more sense, however, isn't the fuel cooler meant to keep the fuel cool?

32krazy!

fuel cooler only works with a/c on and when you run wide open throttle the a/c compressor kicks out so its a kool but ineffective tool. mine is disconnected and i use e85 for cooler burning fuel.

while my car is heavily modded the premise of bigger inj. still works. if you have no plans to go above say 600 hp you could use a 1000 cc inj and be safe. going from 480 to maybe 550 just isnt worth the cheddar considering the work involved. when it comes to modding more fuel is always the best bet to have. use the base of only running 85% max idc. i use 75% to give me a larger safety zone. i ran a brushless pump setup on e85 and ran out of pump at only 750 hp. needed 2 pumps to see 1000 rwhp

2fcknfst

Brushless pumps are a nice touch. So if I understand this correctly, your 2000cc injector is running at 75% dc for an available 1500cc's worth of fuel for 750hp? That, to me, sounds very good in that it will cycle the injector as it was designed to be cycled. So now, you are running 1000whp (1200-ish crank?) with two pumps, e85, and some serious programming... does it drive on the street?