996TT Injector Upgrade

Am currently running K16 hybrids with a 5 bar FPR. Car ran 580 HP on the dyno with this setup but the injectors were maxed out so unable to go any higher. The 5 bar was only ever supposed to be a temporary solution and I'm now looking to install bigger injectors and go back to the stock 3.8 bar FPR. So my question is......which brand and size of injectors should I go for and where's the best place to get them ? It's a Tiptronic and I'm not planning to do any work to the gearbox so need to stick within the its limits (which I believe is around 700-750 HP). AM also running a stock fuel pump which I think should be ok with bigger injectors to a point. Does anybody know at what point I need to look at a better / 2nd pump ? Thanks in advance.

Recently been down this road myself. I went for asnu 1050 injectors and a walbro 455 pump. A mafless tune from Rick at unicorn, fender well intakes and a water / meth kit.

1050s are pretty big. I am currently running 650cc asnu injectors with my hybrid turbos. I have read various things which say once you start getting towards 700hp you are also getting towards the limits of the rods and have to start limiting the torque to protect them, it isn't just the gearbox at those levels. Others say that they are happy to run 800hp though. I guess it depends on how much you want to risk it. MC

Yes my 1050's are way ott! I think my peak duty cycles are around 50%. Agree re engine limits that mc suggests. Also I believe the limit on the tip box is closer to 650bhp to 680bhp. There are options for upgrading it so it is good for 1000bhp which I have researched but currently shelved the idea. I guess it depends on your tuning goals ultimately. My main reason for upgrading injectors was to allow more of a safety net. I was never comfortable with 95% IDC's and the 14 year old fuel pump fully maxed out. Now with my most recent mods I have to turn Psm off to stop it cutting power when launching the car. How much power do you really need?

Okay bit confused here... A k24 turbo is max on a 5bar with stock injectors at 1.3 bar. A k16 hybrid should make a shed load power so at what point (load) where you out of injector? Do you know the flow rate of the k16 hybrid? 30lbs, 35lbs etc? 5 bar will never work on a k16 hybrid unless you are cracking the turbo open very early. Ken

I read in one of your posts once that the limit on the gearbox is around 650 bhp (crank) no more. Is this still true? I also read that you said the internal are good for about 600 crank bhp, is this still true

The first statement was true and still holds some validity. However the gearbox can be managed - you can run 800hp on stock gearbox but you have to know how to control it, what causes issues, how to get it to shift at these levels. Generally though the limit is around 650-700hp as mentioned before. Internal limits - primarily depends on the tuning. I have run close to 850 on stock internals and that lasted 10000 miles before I pushed too hard trying to find limits - have bent rods at this point. RPM is a factor on some components. Again it depends on how you are driving as well - if you are running 50 runs at Vmax on the same day, or running flat on an autobann for 5 minutes - these are all factors that come into the equation. It only takes one component failure, for example 02 sensor, with poor tuning (no room for error) and bang goes your engine - I see tunes regularly that the latter applies too and that is just 500hp. The what if question is very good policy when tuning. I won't build a 9e25 without an engine as a guide. That is a solid 750hp as a guideline. Have run without a built motor and no issues with rods bending. One point Simon, we never give full fat version on any package. It does what it says on the tin of course, but every package is capable of around 20% more performance (we run 80% if that makes sense). But I have to offer a package that is reliable. A 9e30 car is capable of 25 seconds, I just restrict it's ability to do so. Different for our own cars, or if you are doing it yourself, then it is your issue if the engine has an issue.

Does your statement regarding standard internals still remain the same for a Gen 1 997 turbo running 850 ? In other words if I bought a 997 turbo ( Gen 1 ), kept the internals standard and bolted on turbos that delivered 850 bhp do you think the rods would all be the same size after 10k miles? Or have the internal been uprated for the Gen 1 997 TT .

Effectively they are the same engine - there are differences that makes the 997.1 a better engine than the 996 version, but in core strength they are the same. We had a small bend in one rod when stripping an engine on our own car. This was before going for more power. The bend was not dramatic but the point is that further usage would have rendered the engine broken. I don't think you can have a reliable stock engine with a true 850hp level of performance - by that I mean a 20 second run to 300kph approx. That is seriously fast Simon with stock car being in the range of 42-44 seconds and remember where this power really is - from 60mph onwards. You can have a reliable 800 or so hp car with built motor. How long with unbuilt I am not sure - you are clearly close to a lot of component limits - if you kept the stock rpm for example that would help and so on. It is just degrees of reliability Simon - the higher the hp the less reliability. K

Hi Ken, I'm not sure about the flow rate of the turbos but we added the 5 bar following the K16 upgrade (Jan 2015) and then the car was mapped and ran 580hp peak on the dyno. I was told they had to "turn the boost right down" at higher rpm as there was simply not enough fuel. They said at the time that upgrading injectors and going back to stock FPR would allow us to increase boost & power. However this is obviously an engine out job so I decided to put off until this year. Any advice on how best to proceed would be much appreciated

I used to use 630cc injectors with k16 hybrids but have moved on to 840cc injectors since you can make up to 900hp on a k16 hybrid with some fancy stuff inside. I do run 1100cc injectors on some of our k16 hybrids, but I don't believe you will need to go that much. So best advice is go back to the 3.8fpr and find some 80lb injectors ( I say 80lb because you will see some cc number based injectors are based on different fpr. e.g. some 80lb injectors will be quoted as 840cc, others as 870cc and so on. MAKE sure whatever injectors you go for (your tuner should have a preference (make) and there are some differences in tuning on partial/low load(rpm) even if same size) that they have been tested with an actual report on each injector - I have stopped buying a lot of injectors and re valve stock ones to 840cc because of this - have seen as much as 10% difference in one injector to the next, despite them supposedly being the same, which is not good. Depending on what hybrids, you may also need to think about changing the stock fuel pump for a little more coverage. You can find that out once the fpr and injectors are done. And you need to boost leak check your engine before it goes back in whilst it is on the floor. Injectors can leak boost if not properly seated and visible inspection is not enough. K

It can be done with the engine in, just requires great care. Took me about 3 hours. My advice would be, be prepared to take the engine out if required. I took a big gamble and did the work on my ramp at home. No way would I have been able to take the engine out in my little garage. My plan b was to get it recovered to my brothers workshop if anything snapped etc and the engine had to come out. Luckily it all went swimmingly (for once). Only thing that happened is I dropped one of the injectors which took me the next 30 minutes to fish out. There is a good diy on one of the American forums.

Thanks guys, appreciate the advice. I have seen the DIY guide and online but it's not something I would feel confident enough to do at home unfortunately. Here's the dyno output from last year following the turbo upgrade work. You can see where the power levels off over 4000rpm where there wasn't enough fuel to run higher boost.

Hacka, did you resolve your injector issues ?