Vince964T

Just need your opinion guys before I worry if I need to do something or not.

My set up on my 3,3 turbo is pretty simple.
Race cat
Hybrid k27/29 turbo
6 speed 993 gear box
0,9bar of boost
Car weights 1400 KG with me and almost full tank.

I am just slighty slower than 996 GT3s MK1 and 2 in a straight line.
Shouldn't I be a little bit faster ?

Actually my car used to be a little bit faster with the same set up and the K27, but I also had a little more boost for I don't know how long (wastegate membrane leak). Last week end was the 1st time with the new turbo.

911addict

In gear you might be faster, but GT3 will be quicker off the mark and in high speed turns. This I know with experience and similar mods to you (c.380bhp) but not the 6 speed box.
... but of course, the modern car nowhere near as exciting to drive ;-)

Vince964T

Yep I am only talking straight line and in gear. Like coming out of a 3rd gear corner on a racetrack.
Had a few runs with GT3s last week end at the local track and I was slightly slower in the straight.

Ok mine definitly doesn't have 380 HP with those mods.

turboholic

with 380hp you should walk away in gear from MK1 GT3s (mine does). The MK2 is much quicker though, but didnt have opportunity to play with one yet. I dont know what power your car has but I would increase the boost to a safe 1bar (make sure your car has enough fuel by measuring AFRs) and ditch the race cat. You have a hybrid turbo, at what rpm does it kick in?

Vince964T

It kicks in around 3500 (with the 6speed tranny) and the power build up is linear as boost builds up a little bit slower than with the K27, really nice, makes it a bit more predictable.

AFR looks good so 1bar should be fine. It should even be more than fine as I really feel the diff at higher RPMs compared with the old turbo.

What mods do you have on yours so I have a bench mark ?

turboholic

I run a 7006 Turbo with headers, 1bar, decat and stock muffler, around ~380hp. Turbo also kicks in little later than the stock 7200 but pulls hard up to redline. AFRs are good with the usual fat midrange.

Vince964T

Thanks a lot.
I think I know what to do.

Headers I am not sure but 1 bar, no cat and may be slightly shorter gear so I am on boost all the time.
That should work like a dream and hopefully will not stress things to much as my car is probably one of the 964 turbo with the highest amount of track time on it (well the gear box will live a shorter life of course).

I run without a muffler right now. I tested both with and without didn't feel any difference. Car is louder at idle without muffler but same 95 decibel at full throttle when the wastegate opens. Easy to cut weight there.

tjr

I assume you have stock headers? If so I would think that is your problem. The larger hybrid turbo requires more air to make the most of the larger compressor wheel - with stock headers, as you suggest, the K27 is probably giving you both more power and torque. I'd therefore change the headers - that will give your turbo the air is requires, increasing both power and torque. I doubt you'll even need to up your boost to see a benefit. Admittedly it is more expensive but it should be kinder to your engine as you can won't have to up the boost to see the benefit.

Vince964T

Yes it's more expensive and I am a bit hesitant with all the craked headers stories especially since this is a track car only...+ I need heating, i live in sweden. God knows how much i have spent on this car already.

Still I can look into it. Any suggestion. Preferably a European supplier, less of a hassle. I guess my favo Cargrpahics has a product, twice the price compared to everyone else but good quality.

EDIT - I should not be hesitant in fact now that I think of it. I had major cracks in the original headers, had to get them repaired last winter. It's just the price issue. Just saw cargraphics has a complete exshaust package but it''s expensive to say the least.

911addict

You can get headers with heat. I used B&B. Be careful to fit properly so no leaks. Even when done properly they leak when cold but is ok when warm. Hybrid turbo without headers is no good (ask me how I know). My performance mods were:
headers (B&B)
cat bypass (Scart)
no silencer (g-pipe)
Tial wastegate and 0.9 spring (nets 1 bar with the HFS)
HFS turbo
Air filter induction kit (BMC)
LW flywheel.
(plus suspension etc.)

VERY fast in gear, and a hoot to drive.

tjr

As you say, all headers crack, including the OE items. Assuming this is the case, you may want to accept this and just have them welded every year and pay less in the first instance. I bought B&Bs because they are recognised as being slightly freer flowing than GHLs (which I don't think are available any longer). I looked at Cargraphic but couldn't find any evidence of their relative merits vs. B&B - although at the time they were about twice the price of B&Bs partly because of the strength of the £ vs. the £ at the time (early 2008). My car had had a B&B muffler on it for 13 years at that point and was (and still is) perfect, so on that evidence I decided to buy the B&Bs. I also needed a new turbo so bought a K27 HFS which I was told needs the B&Bs to work optimally - hence my comment re. your hybrid. My car pulls strongly from around 3k and just keeps on going!

I know 911addict very well - and we both agree that the B&B headers were the best mod from a performance point of view, even more so than the larger turbo...

Vince964T

Thanks for the reference. Nice set up ! And I like keeping it at 0,9b given the amount of track time I have on the engine.
Ok how do you know please ;-)


A few more Euros and she will be perfect, just as Porsche should have build it from the start.

cobalt

I would think with the mods listed the GT3 should be a little faster. Of the 3.3's I have known with B&B headers, HF k27, cat delete, sport muffler, Billet BOV and 1 bar spring these cars were just seeing 375 BHP on average some better some worse depending on CIS condition, leak down and compression numbers. Since you are retaining a race cat and .9 bar spring with an unknown turbo I might suspect you are seeing 355 bhp or roughly 300 at the wheels.

I pull on GT3's but I am starting off with more power and have mods increasing power to 385 to the rear wheels. I would start by looking into seeing if you have any vacuum leaks in the CIS. All the mods in the world are worth nothing if the CIS isn't running at 100%. BTW the GT3's are fast cars and being N/A is an advantage on the track, Your 6 speed box might actually be working against you too, since you need to shift more often and loose boost during shifts.

Vince964T

Thanks tjr.

Seems they have different sizes on the B&B models. Would you be kind enough to indicate which one you went for if possible. I guess this one.
FPOR-0110 930/911 TURBO HEADERS 1 5/8" W/ HEAT EXCHANGERS 79-89

http://www.bbexhaust.com/car/930/

If you don't remember no worries I ll check with them when it's time.
Cargraphics is more expensive.

Vince964T

I don't loose much to GT3s as it is, so it's probably normal given the set up as you say. I was a bit afraid at 1st as the car was dynoed at 300hp at the engine but taking her to the track I was releived to see it's definitly giving way more. Just may be not as much as I hoped for and less than before with the wastegate leaking erm erm...

For the 6 speed gear box shifting is not a problem. I have a working BOV so I don't loose much and I am a little bit higher in the REVs all the time. With the K27 and race cat I actually had almost 0 lag and the car was very close to an athmo with excellent engine response ! Worked perfectly. A great mod even if it took me a little bit of time to get used to driving with no lag.
I actually loose in some corners but it's because the gear ratios just don't fit that specific corner but overall I became faster on every track.

I will see what I do but if a more free flowing exhaust doesn't cut the lag I will shorten the gears even more. They will still be long compared to say a 996CUP !