6 speed or 3.8 litres?
Thread Starter
Racer
Joined: Nov 2001
Posts: 320
Likes: 3
From: Vienna, St. Gallen, Stuttgart - Europe
6 speed or 3.8 litres?
Hi,
As Adrian knows, I have a slightly modified 1991 C2 coupe.
The story so far:
The engine was upgraded with Cup exhaust pipe, bigger throtle body, K&N, Roock chip and strenghtened valve spring seats. Oh, and I also drilled my airbox. Now I have 290 hp on the dyno. Further modifications include and RS flywheel and clutch, H&R springs over Bilstein sport dampers, braided brake lines and Pagid liners, front strut bar and some niceties in the interior as well as a 3.2l Carrera rear wing.
The problem:
I love to race alpine passes here in Switzerland. However, with the longer gearing of the Swiss 5 speed gearbox and little low down torque, u-turns are not quite as racey as the stretches in between.
Possible solutions:
Either I have a 6 speed 993 gearbox with ROW gearing installed to exploit the better part of my torque curve. Price roughly USD 5000 (incl. 996 GT3 limited slip dif).
Or I have the engine enlarged to 3.8 litres with different cams etc. to have more low down torque. Price should be somewhat higher than the gearbox option.
The question:
What are your recommendations and does anybody have experiences with the two possible solutions?
Thanks for your help!
Anatol
As Adrian knows, I have a slightly modified 1991 C2 coupe.
The story so far:
The engine was upgraded with Cup exhaust pipe, bigger throtle body, K&N, Roock chip and strenghtened valve spring seats. Oh, and I also drilled my airbox. Now I have 290 hp on the dyno. Further modifications include and RS flywheel and clutch, H&R springs over Bilstein sport dampers, braided brake lines and Pagid liners, front strut bar and some niceties in the interior as well as a 3.2l Carrera rear wing.
The problem:
I love to race alpine passes here in Switzerland. However, with the longer gearing of the Swiss 5 speed gearbox and little low down torque, u-turns are not quite as racey as the stretches in between.
Possible solutions:
Either I have a 6 speed 993 gearbox with ROW gearing installed to exploit the better part of my torque curve. Price roughly USD 5000 (incl. 996 GT3 limited slip dif).
Or I have the engine enlarged to 3.8 litres with different cams etc. to have more low down torque. Price should be somewhat higher than the gearbox option.
The question:
What are your recommendations and does anybody have experiences with the two possible solutions?
Thanks for your help!
Anatol
Addict
Lead Rennlist
Technical Advisor
Rennlist
Lifetime Member
Lead Rennlist
Technical Advisor
Rennlist
Lifetime Member
Joined: May 2001
Posts: 8,027
Likes: 17
From: Parafield Gardens
Dear Anatol,
I think the power will not be improved greatly going to 3.8 Litres over what you have. The data I have been given is that you will get up to 297HP on the crank with the 3.8 conversion and Roock sports cams.
I would go for the 6 speed gearbox and the LSD. But you knew I would say this seeing as I have driven your C2,
Ciao,
Adrian
911C4
I think the power will not be improved greatly going to 3.8 Litres over what you have. The data I have been given is that you will get up to 297HP on the crank with the 3.8 conversion and Roock sports cams.
I would go for the 6 speed gearbox and the LSD. But you knew I would say this seeing as I have driven your C2,
Ciao,
Adrian
911C4
Addict
Rennlist Member
Rennlist Member
Joined: Jun 2001
Posts: 2,537
Likes: 1
From: Dana Point, CA
Hi Anatol,
I'll just add that I do have a 993 6-speed in my '91 C2. Works great, and pretty much just a bolt-on installation. Seem to remember that all you need is a new rear shift rod to swap from the 964 to the 993 unit.
The above applies to a C2 only. I believe installation is more complicated for a C4.
I'll just add that I do have a 993 6-speed in my '91 C2. Works great, and pretty much just a bolt-on installation. Seem to remember that all you need is a new rear shift rod to swap from the 964 to the 993 unit.
The above applies to a C2 only. I believe installation is more complicated for a C4.
Thread Starter
Racer
Joined: Nov 2001
Posts: 320
Likes: 3
From: Vienna, St. Gallen, Stuttgart - Europe
Well, the gearbox seems to be it. Especially since I am reluctant to open a good engine. You never know whether it is still good when you close it...
Above all, should I think about selling the car later, it may be easier to sell with the 6 speeder than with some aftermarket 3.8l modification.
Re-gearing came to my mind, too. However, my car runs into the rev limiter in fifth, so a longer top would be ok (in Germany, you know). And swapping the lower gears would almost cost as much in labor as a new bolt-on job for the new gearbox.
Thank you for your help!
Anatol
1991 C2
Above all, should I think about selling the car later, it may be easier to sell with the 6 speeder than with some aftermarket 3.8l modification.
Re-gearing came to my mind, too. However, my car runs into the rev limiter in fifth, so a longer top would be ok (in Germany, you know). And swapping the lower gears would almost cost as much in labor as a new bolt-on job for the new gearbox.
Thank you for your help!
Anatol
1991 C2
Addict
Rennlist Member
Rennlist Member
Joined: May 2001
Posts: 764
Likes: 1
Anatol:
When I was searching for 911s I came across a car that had the 3.8 job done on it. FWIW, it was NOT cheap (almost $20,000), but the original owner made almost every modification possible to it (intake, exhaust, cams, chips, you name it, he did it). All the paper work was there and it was very detailed. I remember trying to isolate just the cost of the engine mods (3.8 bore out) and I think it was about $10K (all figures I post are US dollars). The shop he took it to is not known for their low prices.
If you're already getting decent power (and it certainly sounds like you are) and the transmission conversion is feasible, that's what I'd go for.
Just my opinions,
Bill Wagner
When I was searching for 911s I came across a car that had the 3.8 job done on it. FWIW, it was NOT cheap (almost $20,000), but the original owner made almost every modification possible to it (intake, exhaust, cams, chips, you name it, he did it). All the paper work was there and it was very detailed. I remember trying to isolate just the cost of the engine mods (3.8 bore out) and I think it was about $10K (all figures I post are US dollars). The shop he took it to is not known for their low prices.
If you're already getting decent power (and it certainly sounds like you are) and the transmission conversion is feasible, that's what I'd go for.
Just my opinions,
Bill Wagner
Addict
Lead Rennlist
Technical Advisor
Rennlist
Lifetime Member
Lead Rennlist
Technical Advisor
Rennlist
Lifetime Member
Joined: May 2001
Posts: 8,027
Likes: 17
From: Parafield Gardens
I have just received the data from a 964 owner in England who had a complete job done on his engine converting it to 3.8 Litres, replaced the clutch and flywheel with RS versions. Cost was around 9000 UK Pounds. His HP on the wheels is around 263HP now,
Ciao,
Adrian
911C4
PS: I should add that the trick parts installed were from Roock. Not cheap.
Ciao,
Adrian
911C4
PS: I should add that the trick parts installed were from Roock. Not cheap.
Trending Topics
Thread Starter
Racer
Joined: Nov 2001
Posts: 320
Likes: 3
From: Vienna, St. Gallen, Stuttgart - Europe
Which improvements should I expect from different camshafts? Is there a cam shape that would keep my current max hp but improve low end torque at the same time?
Anatol
1991 C2
Anatol
1991 C2
Rennlist Stories
The Best Porsche Posts for Porsche Enthusiasts
10 Used Porsches Are Selling for Way Too Cheap
Joe Kucinski
Tuner Is Converting Porsche 911s Into Shooting Brakes
Verdad Gallardo
This Coachbuilt Creation Is A Modern Take on the Legendary Porsche 917
Verdad Gallardo
Is This Convertible Cayenne A Steal, Or A Returnless Investment?
Verdad Gallardo
10 Best Non-Flat Six Porsches You Can Buy For Under $100K
Joe Kucinski
Porsche's Top 5 Most Questionable Naming Decisions
Verdad Gallardo
Pogea Racing's 964 Porsche 911 Reimagination Stands Out in a Crowded Field
Verdad Gallardo
6 Convertible Top MYTHS Most People Don't Understand!
Michael S. Palmer
2026 Porsche 911 Club Coupe is Spectacular, And Everything Wrong with the Porsche Market
Joe Kucinski
Addict
Lead Rennlist
Technical Advisor
Rennlist
Lifetime Member
Lead Rennlist
Technical Advisor
Rennlist
Lifetime Member
Joined: May 2001
Posts: 8,027
Likes: 17
From: Parafield Gardens
Dear Anatol,
You will really need to ask the camshaft suppliers for their data. Call Roock, RUF, Kremer, FVD, Sportec and ask them what they feel would meet your requirements,
Ciao,
Adrian
911C4
You will really need to ask the camshaft suppliers for their data. Call Roock, RUF, Kremer, FVD, Sportec and ask them what they feel would meet your requirements,
Ciao,
Adrian
911C4
5th Gear
Joined: Nov 2001
Posts: 5
Likes: 0
From: London, UK
Chaps,
Adrian mentioned my car in reply to this post - I have a '90 C2 coupe that has just had a 3.8l conversion. Not the cheapest thing to do, but my engine was getting rather sick, tired and leaky, so I decided to have a top-end rebuild and sort it out once-and-for-all. It's a little down on peak power as I'm still awaiting the correct chip (should arrive tomorrow) but the torque is phenomenal. About 210lb ft from 1500rpm, rising to 285lb ft at 5000rpm, so it is incredibly driveable. I don't know what a 6spd transmission would be like, didn't even know you could do this so I'll add it to my list!! I may be a little biased, but this is an excellent conversion if you need more bottom-end torque and overall driveability. I'll keep you posted on the top-end when my chip arrives!!
Michael
Adrian mentioned my car in reply to this post - I have a '90 C2 coupe that has just had a 3.8l conversion. Not the cheapest thing to do, but my engine was getting rather sick, tired and leaky, so I decided to have a top-end rebuild and sort it out once-and-for-all. It's a little down on peak power as I'm still awaiting the correct chip (should arrive tomorrow) but the torque is phenomenal. About 210lb ft from 1500rpm, rising to 285lb ft at 5000rpm, so it is incredibly driveable. I don't know what a 6spd transmission would be like, didn't even know you could do this so I'll add it to my list!! I may be a little biased, but this is an excellent conversion if you need more bottom-end torque and overall driveability. I'll keep you posted on the top-end when my chip arrives!!
Michael
Addict
Lead Rennlist
Technical Advisor
Rennlist
Lifetime Member
Lead Rennlist
Technical Advisor
Rennlist
Lifetime Member
Joined: May 2001
Posts: 8,027
Likes: 17
From: Parafield Gardens
Dear Michael,
Anatol already has a similar power output to a 3.8 anyway. This is why I said go for the gearbox. Your 3.8 conversion as I told you has been incorporated into my book,
Ciao,
Adrian
911C4
PS: For the record. Anatol did not tell this in his posts but his C2 was previously owned by a quite well known Swiss race car driver who has a rather powerful 935 he blasts around the place. This C2 has had some tender loving care and some killer mods carried out on it by people who know exactly what they are doing. They are not independents either.
Anatol already has a similar power output to a 3.8 anyway. This is why I said go for the gearbox. Your 3.8 conversion as I told you has been incorporated into my book,
Ciao,
Adrian
911C4
PS: For the record. Anatol did not tell this in his posts but his C2 was previously owned by a quite well known Swiss race car driver who has a rather powerful 935 he blasts around the place. This C2 has had some tender loving care and some killer mods carried out on it by people who know exactly what they are doing. They are not independents either.
5th Gear
Joined: Nov 2001
Posts: 5
Likes: 0
From: London, UK
Hi Adrian,
I appreciate that, and it sounds like a cracking car. I'd love to drop a 6spd box into mine, but I think I've spent more than enough for one lifetime (well, this year at least).
As you know, dyno figures vary wildly, so I'm always a little dubious of power claims. If the car feels right to drive then that's the most important thing. I'm curious to know what the torque curve is like though 'cos that's probably more important than peak power, isn't it?
Is there any scope for lightening Anatol's C2 to help the power-to-weight, or has that work been done already?
Regards,
Michael
I appreciate that, and it sounds like a cracking car. I'd love to drop a 6spd box into mine, but I think I've spent more than enough for one lifetime (well, this year at least).
As you know, dyno figures vary wildly, so I'm always a little dubious of power claims. If the car feels right to drive then that's the most important thing. I'm curious to know what the torque curve is like though 'cos that's probably more important than peak power, isn't it?
Is there any scope for lightening Anatol's C2 to help the power-to-weight, or has that work been done already?
Regards,
Michael
Addict
Lead Rennlist
Technical Advisor
Rennlist
Lifetime Member
Lead Rennlist
Technical Advisor
Rennlist
Lifetime Member
Joined: May 2001
Posts: 8,027
Likes: 17
From: Parafield Gardens
Dear Michael,
Anatol and I have had many conversations on the lightening of his C2. He has basically a full interior plus a huge fixed rear wing. I have physically shown him (plus he drove my C4) on mine what and how I removed things to reduce weight. Mainly sound proofing I removed and replaced with super lightweight tool box hard foam.
Anatols C2 goes like a rocket, especially in third gear.
Ciao,
Adrian
911C4
PS: The Roock parts help.
Anatol and I have had many conversations on the lightening of his C2. He has basically a full interior plus a huge fixed rear wing. I have physically shown him (plus he drove my C4) on mine what and how I removed things to reduce weight. Mainly sound proofing I removed and replaced with super lightweight tool box hard foam.
Anatols C2 goes like a rocket, especially in third gear.
Ciao,
Adrian
911C4
PS: The Roock parts help.
Track Day
Joined: Jun 2001
Posts: 23
Likes: 0
From: Bucks, UK
Anatol/Adrian/Michael
I have been following the Michael 3.8 saga at JZMachtech quite closely because I have the same conversion for my C4 in mind for next year. We are all dying to know whether the new chip works and to what extent!!
I too have the cup pipe and an upgraded chip (JZM's own not Roock) but have not had the car dyno'd because 4wd dynos are less available -- JZM do not have a 4wd dyno, for instance.
I am extremely interested in the sheer quantity of power Anatol has achieved for the following reasons: my engine is an extremely good one, not least because it was rebuilt and mildly modified a year ago. It would seem to be that a good alternative for me might be to go the same route as Anatol so far - i.e. different throttle bodies on top of the current changes (I assume there would be a few other items in addition but not many) plus perhaps look at a 6-speeder. This would avoid a second engine rebuild within two years just to get the 3.8 ltr depth of torque.
Any comments on this??? I do not think I got the strengthened valve springs during the rebuild and would be interested to know why it was thought they were required for 290bhp.
By the way, I think Michael's comment that it would be interesting to compare the torque curves of the two cars is appropriate .. that would answer a load of questions on its own
Andrew
1989 C4
I have been following the Michael 3.8 saga at JZMachtech quite closely because I have the same conversion for my C4 in mind for next year. We are all dying to know whether the new chip works and to what extent!!
I too have the cup pipe and an upgraded chip (JZM's own not Roock) but have not had the car dyno'd because 4wd dynos are less available -- JZM do not have a 4wd dyno, for instance.
I am extremely interested in the sheer quantity of power Anatol has achieved for the following reasons: my engine is an extremely good one, not least because it was rebuilt and mildly modified a year ago. It would seem to be that a good alternative for me might be to go the same route as Anatol so far - i.e. different throttle bodies on top of the current changes (I assume there would be a few other items in addition but not many) plus perhaps look at a 6-speeder. This would avoid a second engine rebuild within two years just to get the 3.8 ltr depth of torque.
Any comments on this??? I do not think I got the strengthened valve springs during the rebuild and would be interested to know why it was thought they were required for 290bhp.
By the way, I think Michael's comment that it would be interesting to compare the torque curves of the two cars is appropriate .. that would answer a load of questions on its own
Andrew
1989 C4
Thread Starter
Racer
Joined: Nov 2001
Posts: 320
Likes: 3
From: Vienna, St. Gallen, Stuttgart - Europe
Hi,
I can provide dyno prints of my engine before modification and after. Maybe Adrian can scan and post them.
Before modification I had some 254 hp (computed) on the flywheel and afterwards approx. 289 hp, if I remember correctly. Have to take a look at the prints for the torque figures, though.
My car is in winter storage right now but I will proceed with the gearbox project in the weeks to come and keep you all informed.
Another thought: my mechanic has recommended trying my old B90 16" wheels with semi-slicks for the ultimate acceleration fun in the mountains - rather than selling them for nothing as I was planning.
Ciao
Anatol
1991 C2
I can provide dyno prints of my engine before modification and after. Maybe Adrian can scan and post them.
Before modification I had some 254 hp (computed) on the flywheel and afterwards approx. 289 hp, if I remember correctly. Have to take a look at the prints for the torque figures, though.
My car is in winter storage right now but I will proceed with the gearbox project in the weeks to come and keep you all informed.
Another thought: my mechanic has recommended trying my old B90 16" wheels with semi-slicks for the ultimate acceleration fun in the mountains - rather than selling them for nothing as I was planning.
Ciao
Anatol
1991 C2