advice for 3,2 "group B" engine

[MaRu]

Hello guys,

guess this is my first post, so a little introduction. My name is Malte, Iīm from germany. The last 2 years I was racing a 3.0 Group4 911 in a german rally trophy. Now I decided to swap to group B with a 3,2 Carrera (FIA Homologation B-282). Actually I am not sure if you are building your race cars with these regulations, too.

I am not 100% firm with these regulations yet. But here is what I know for sure.
The engine size must stay 3,2 (LS)
Only one spark plug
stock port size
Throttle body must be original 63 mm
engine management whatever I want but I must keep the original air-flow meter
also must keep orginal valve size

Now I wonder what would be best to modify and with which parts. I want the power start at about 3500 and be really strong between 5000 and 7000 with a limit of 7300-7500 rpm. Due to the 63mm throttel body and the original 3,2 intake manifold I have no idea what cam will be best.

Here is what my thoughts are so far:


-fine balanced knife edged crank
-air flow modification inside the case and on cylinders
-10,3 cr pistons with pockets
-lightly ported/cleaned ports
-racing valve springs with titan caps
-cams???
-ECU?
-exhaust relatively open with 6 in 2 in one in little muffler

What would you guys recomment me to do?

many thanks in advanced and sorry for my school english from some days ago...

Malte

[MaRu]

forgot to say, -running on 98 octan and with short gearbox....

[Weissach911]

Have you looked at the permitted modifications allowed in Group A ?

You will find this information in Appendix J for 1985 which would still be applicable until 1990 when it was updated.

http://www.fia.com/en-GB/sport/regulations/Pages/FIAHistoricRacingChampionships.aspx

All of the modifications allowed in Group A are also permitted in Group B so providing you don't change the engine capacity class you can increase capacity by 0.6mm on bore diameter and in the limit this must be worth considering.

I believe cams are free but there is a restriction that Valve Lift must be standard and I am not sure the K jetronic will deal with an increase in overlap.

If you increase compression too much could you run into detonation problems with 'mild' cam profiles.

[MaRu]

Hello weissach911,

thanks for your answer! Yes I looked there. I also read about the 0,6 mm bore and i am thinking about this, too. what in your mind would be a good piston for this?

I am totally free with cams, regarding duration and lift. And I donīt have to deal with the k-jetronic as it is a 3,2 with motronic. But here I have to keep the throttle body and probably also the air flow meter. And I think if so this might limited my cam profile. When it is to extrem, I might not be able to have all the air needed through the throttel boday and the air flow meter at top rpm.... But i donīt know how to calculate this...

My 3,0 group 4 engines runs very good on 10,3 pistons 98 octane fuel and max 36 degree advance ignition. i do not expect deternation problems. this engine has the S cam, but i guess there are better profiles available now.

Thanks, Malte

[Weissach911]

I have been using Woessner Pistons which are 4032-T6 and have performed very well.

can you change the connecting rods? as I think the 3.2 rods will not be so good at the RPM limits you are considering.

I quite like DC40 and DC43-102 cams but for Rally Cars

[MaRu]

Thanks for the pistons! I can change rods, -which one do you prefer here? My engine should be for rally, too. Most tarmac, but it should not only have good peek hp but also torque at mid refs...

[Weissach911]

Originally Posted by MaRu

Thanks for the pistons! I can change rods, -which one do you prefer here? My engine should be for rally, too. Most tarmac, but it should not only have good peek hp but also torque at mid refs...

I rather like the R & R rods that LN Engineering market with a 3.0 litre size pin or Pankl but these would be very expensive.

If you are using a 915 box I have low gear sets we had made some time ago.

They use the 8:31 CWP from the later box and use a stock first gear.

We re-manufactured 2nd, 3rd, 4th and 5th.

In fifth gear they will give about 190kph at 7250rpm and they are evenly spaced between.

It was cheaper to do this than to buy a new frst gear and an 8:35 CWP.

These gears have been used in the UK for forest/tarmac rallies for a few years now and have never suffered any failures.

PM me an e-mail address and I will send you a gear chart if they are of interest.

[MaRu]

pm sent

[MaRu]

Did no one ever buildt or drove an engine similar with my plans and would share his experience? Especially in regards to the original 3,2 intake manifold, and the choice of cams in contrast to the 63 mm throttle boday I could need some advice...

Thanks. Malte

[nardo911]

I would pensse his best to make you a map with Acc
specific
the flowmeter is adjustable Sambla me that we must strive for the resort that it is more reactive

[MaRu]

Hello Nardo911,

guess I do not really understand what you want to say with it. Can you specify it a bid.

Thanks, regards Malte

[FloarmaAloria]

And to "jwelectric" I guess youre right. I probably do have a screw loose. Not only am I renovating the kitchen, Im renovating the whole house... as hj and dlarrivee can attest to from my plumbing questions in the other forum.
fun fun fun ...