996 TT Tuning: FPR vs Injectors

[ok51mon]

Having my TT has taken me on a rather interesting journey, as result Im potentially looking at implementing a tuning package if decide to keep it.


I do however have some questions of what way to go regarding fuel delivery system.


Here is is what my Bolt on's will look like;



997 GTS RS Intercoolers
Europe Exhaust (100cell)
K16 Hybrid (Permutation is yet to be decided)
IPD Plenum and TB (74 mm)
5 Bar FPR or 60 lbs Injectors (TBD)???
Fuel Pump (W)

Looks exciting doesn't it!?

I do have a question through which I hope more seasoned tuners can help me with. I am shooting for power of around 620- 690 bhp however, I have read that this can be achieved by implementing a simple 5 Bar Fuel Pressure Regulator. This wasn't my preferred option as I didn't want the risk the car running lean, however I still want to explore it.


I have also read and been told that a 5 Bar FPR a car cannot produce more than 580 bhp (Fly) as a result of this limiting fuel delivery method. It's even been discussed on here (http://911uk.com/viewtopic.php?t=67932&postdays=0&postorder=asc&start=20)

What I don't understand is that I have seen cars dynoed and for sale with a tuning packages identical to the above which were using 5 Bar FRP's and the BHP figure were 640/ 630 bhp??

I understanding every aspect of each bolt on and its value in my tuning setup however this Fuel pressure regulator has thrown me a bit.

Could anyone comment please?


Si

 

[ok51mon]

Sorry! Grammar and Spelling amended. I was extremely drunk and in thought when I wrote this, it's been plaguing my mind for days!


Can anyone comment?

 

[neil allan]

I think it comes down to physics doesn't lie ,but rolling roads and pub talk can


I have been told the same around 580 max with a 5 bar , im only running 1.3 bar with K24's and my IDC was in the 90's so have fitted a 5 bar and new tune dropping IDC.
Im planning on fitting K16 hybrids next and will be going for injectors, I don't see the point of spending on turbos and then no managing to get the best from them.

 

[JohnnyDangerous]

I would not even say its 580, you injectors will be locked at 100 duty cycle, mine were at 1.1 bar with 5 bar, plus injectors are designed to operate at at a certain pressure, my asnu's are 3.8 bar after that the spray pattern goes off. Junk the stock pump and system and run a 1 or 2 pump -6 to -10 to -6 to each rail with aeromotive reg and 800 issh CC ASNU injectors, it will drive like stock and more than you ever need, if the injectors lock the only way to control DET is to pull timing.

 

[ok51mon]

So how can these cars be producing 640 bhp with 5 Bar FPR???? Are the dyno's inaccurate or will it eventually start to pull timing above a certain speed i.e above 140 mph??

 

[Manic996t]

agree with JD,

5bar is really a band aid to bring IDC down, nothing wrong with that approach if it suits your goals IMHO upto 550ish hp after that you should upgrade injectors


however for you hp target injectors are the only sensible option

ASNU's are very good

Fuel pump and lines is optional but definitely advisable and will future proof you for when you want more hp

I'm sceptical about over over 600 on just a 5bar, only way I'd believe it is with logs or a 1/4 slip to prove the acceleration ties up with the dyno hp figure

 

[ragpicker]

So how can these cars be producing 640 bhp with 5 Bar FPR????

They aren't! :wink:

 

[DynoMike]

So how can these cars be producing 640 bhp with 5 Bar FPR????

They aren't! :wink:

^^^^^This^^^^^

 

[Bodgerben]

So how can these cars be producing 640 bhp with 5 Bar FPR???? Are the dyno's inaccurate or will it eventually start to pull timing above a certain speed i.e above 140 mph??

That depends on the latent energy of the local air, it's a well known phenomenon that the local air will produce the desired power that the owner requires.

Some air and it's constituent components produce more power than others.

Much like air temperature, a lot of focus has been made to keep air intake temps low, air density is higher, when temps are low, so you'll produce more power. What is less understood is the make up of local air, which can, and will produce different power levels. Some air can produce far more power than other air.

Along with the local air energy content, you also have to consider the direction of the wind. If the wind is blowing from a low energy direction your car will produce less power. However, if, as is often the case when you need to quote a power level, the air is in fact blowing in from a high energy location, you'll find that you can in fact produce 640bhp from a 996 Turbo even though your injectors are fully open and the engine cannot physically consume any more fuel. It's all in the air. More focus needs to be committed to investigating the power of air. When air energy content is fully undersotod we'll see 800 bhp 996T's with much less than a 5 bar FPR.

Unfortunately we've not been able to capitalise on the power levels of thin air and had to resort to fitting bigger injectors and chuck more fuel in.

 

[JohnnyDangerous]

If I put you in my car and told you it was 850hp you would believe me !!! Dyno HP is a selling point what would you rather have a 640hp 11 sec car or 599hp 10 sec car, the only true teller of hp and torque is a time ticket with terminal speed.

 

[ok51mon]

Wow.


So I guess injectors are the way to go??


would 60 lb injectors give me a rough idle?? Bare in mind I'm not changing the cam profiles?


At the end of the day I want something fast , that runs and sounds (with the exceptions of a sports exhaust) like a normal porsche. I don't want it sounding like a tractor!!

 

[JohnnyDangerous]

Ive got 1100cc injectors, we arent american we dont measure in lbs and my car idles as good as yours, it will on 1600 as well !!!

 

[ragpicker]

1100cc here too and absolutely no idle issues.

It knows how to empty a tank of fuel into the cylinders very quickly though!

I could do with a larger fuel tank so it can start driving past the first filling station it sees...

 

[DynoMike]

So how can these cars be producing 640 bhp with 5 Bar FPR???? Are the dyno's inaccurate or will it eventually start to pull timing above a certain speed i.e above 140 mph??

That depends on the latent energy of the local air, it's a well known phenomenon that the local air will produce the desired power that the owner requires.

Some air and it's constituent components produce more power than others.

Much like air temperature, a lot of focus has been made to keep air intake temps low, air density is higher, when temps are low, so you'll produce more power. What is less understood is the make up of local air, which can, and will produce different power levels. Some air can produce far more power than other air.

Along with the local air energy content, you also have to consider the direction of the wind. If the wind is blowing from a low energy direction your car will produce less power. However, if, as is often the case when you need to quote a power level, the air is in fact blowing in from a high energy location, you'll find that you can in fact produce 640bhp from a 996 Turbo even though your injectors are fully open and the engine cannot physically consume any more fuel. It's all in the air. More focus needs to be committed to investigating the power of air. When air energy content is fully undersotod we'll see 800 bhp 996T's with much less than a 5 bar FPR.

Unfortunately we've not been able to capitalise on the power levels of thin air and had to resort to fitting bigger injectors and chuck more fuel in.

Bodgerben, I think what you are trying to convey in this statement is Barometric pressure. The local air pressure numbers can produce drastically differing results when tested on the same engine.

An example would help here; In 2007 we started to develop the then new Yamaha R1, for Superbike racing. We had an engine on the dyno and were in the process of mapping the Life ECU, which can take 16 hours when starting from an entirely clean sheet of paper. The local air pressure was a shockingly low 958mb (the deepest depression we have ever seen). From memory, the raw, uncorrected horsepower was a pathetic 174 at the gearbox sprocket, which corrected to DIN70020 gave us 196.5hp at 13500 revs. Aware that the storm was moving through, we stopped mapping on that day. The following day, the barometric pressure reading was 1003mb. The nett results of which was 195hp at the gearbox sprocket raw, 196.5 corrected.

Interestingly, the Vapour pressure was higher on day two (more moisture in the air). We then ran on day 3, with 1012mb, which is as near to DINs 1013 'Standard day' correction factor, the motor gave 196.9 hp uncorrected, 196.5 corrected.

With a turbo motor, obviously more air is being forced in to compensate for low baro days, but the turbos are working harder to get the quantity in=more heat generated. The energy however, comes from the fuel, the air carrying the oxygen being the catalyst needed to produce power from burning the fuel. To make 800 hp from standard injectors at 3.8 bar fuel pressure, the motor would have to be run with Air/Fuel ratios of about 23:1, currently unachievable, particularly with a turbocharged production engine.

Going back to the air quality statement, as well as Barometric pressures needing to be reasonable, temps low for greater density (and therefore oxygen bearing content), a lack of contamination is very important too. Many times we have had cross-contamination from the exhaust, where we haven't quite got the extraction right, and this murders power, as the contaminants displace much needed oxygen.

As for the original question, some over-head capability is always needed when sizing injectors. Think very cold days (a lot more fuel needed to be added to the dense air), very high barometric local air pressures of circa 1040mb and the requirement of the DME to add fuel when the engine detonates. All of these scenarios require added fuel. With a perfect storm of all three being combined, an injector at 90% duty cycle can quickly run out of head room. Which toasts the pistons amongst other things.

 

[ok51mon]

I think for my set up i'd be looking at siemens deka 875cc or the ANSU equivalent injectors.


Can anyone comment ? The great "Todd" of tuning recommends the siemens for stocks ecu's but I've also been told ANSU ones are also great.