Martin S.

I agree that on a short course, gears are a huge difference...on a monster course such as Cali Speedway...they help in a couple of spots...but they are not the ultimate advantage as some seem to think.

ZP44 writes, "a huge part of racing 911's is really about experience & skill"...and alludes to the better time a better driver will get in your car. I couldn't agree more. There is that continuum of talent and car preparation. A car with minimal preparation and an excellent driver will be more successful than a mediocre drive in a well prepared car...assuming that the cars are somewhat similar...those pesky Turbo cars can make up for a lot of sins on the long straights!

I know that Cort Wagner took a fairly stock 996 around WSIR and did a 1:29, or so I was told...if I trusted anyone to drive my car at speed, I'd have Doug Baron, Kevin Rousch, Cort Wagner, Randy Pobst or some other hot shoe take my car around WSIR so I could judge the potential of the car. I just don't want to know that badly....for me it all comes down to fear, and that is somewhat in Turn 8, and for sure in Turn 9. I know I could be a lot faster through 9, but I am afreaid to miss the apex...the consequence for a poor apex, especially early apex can be catastrophic...

I calculate my car is capable of about a 1:33 at WSIR...my best time ever was a 1:36. I have some work to do as I usually linger around 1:38. Now where can I find that 5 seconds.

I have switched to Hoosiers...that seems to help, and I plan on installing a Guard LSD; that should help as my current LDS is toast....seat time...

ca993twin

Let me go back for a moment to the original topic... 400HP out of a 4 liter conversion. Help me here. If you add 10% more displacement to a 3.6, AND you could get it to breathe sufficiently well for that extra volume, you could reasonably expect a 10% imprivement in HP. That would take the 282HP (have I got that number right?) 3.6 to around 315hp or so. This assumes you can somehow get 10% better flow through those heads, which is not easy.

So how do you get the extra 85HP? You have to increase the efficiency (higher compression?). Or spin it faster, along with cams, intake and exhaust that are optimized for the higher revs. Either of these paths will cause more stress, reduce life, and probably make passing California emissions pretty tough. My point is that this does not sound like a simple bolt-on that will yield a nice, streetable, reliable car. A race engine can get those numbers, no doubt... but a race engine likes a rebuild every race season. A problem is the old technology, air-cooled basis for our engines. We simply can't get the high specific outputs like the more modern stuff.

Am I too pessimistic about these old 2-valve engines? Is there some upgrade path that I'm not thinking of? I'm thinking that original poster of this thread was thinking about a simple, 4 liter conversion that he could reliably use on the street, and have 400 HP. I just don't see how that's possible.

RallyJon

The 9M engine is much more than a displacement increase.

Instant-G has a good page on the myth of big power from small displacement increases: http://instant-g.com/Products/36Conversion/38.html

For a fun street 993 all I want is 320 or so ft-lbs of torque at 3000 rpm. Something that is apparently also impossible.

Martin S.

We see above from CA993twin, "a simple, 4 liter conversion that he could reliably use on the street, and have 400 HP. I just don't see how that's possible."

Great observation....it's not possible would be my conclusion. Were it doable, the 993 model run was over in 1998, don't you think we'd have seen it by now?

Let's think for a moment how Porsche is getting big HP (GT3 as an example) out of a NA engine:
Vario Ram
Vario Cam
Water cooled
4 valves per cylinder
Advanced electronics
Lighter reciprocating parts
Higher revs tolerated

Geoffrey

The variocam in the Porsche GT3 and TT is primarly for emissions and low end torque, not peak power.

I also wouldn't hesitate to put my over 100hp/liter engine into my street car.

Martin S.

Who would have thunk it....

'95 993

Rallyjon - how about 313lbft @ 4600 rpm. That is what 9m billet heads gave my 3.6l non varioram 993.

the conversion also included hotter cams and 100 cell race cats and live remap - very strong torque monster, bit of a handful on the track in the wet, but in the dry with Michelin cup sport tyres, fantastic :-)

Rassel

Two things needs to be separated - Is the goal:
A.) Get a 4.0L engine?
or
B.) Get over 400hp in a N/A F6 engine that would fit?

Don't stare too much on displacement, you can get 400+ bhp from smaller displacement.

Here's one example of a 3.2 N/A engine that makes 418hp:
http://www.spezialmotorer.com/start/3_2/418HP_3.htm
Lots of pictures of the engine also!

Also, getting a 4.0L engine running can also be done. Easily if you forget the +400bhp

NineMeister

I think you have posted this link before Rassel. I would still like to see the dyno curve though.


As for the suitability of running a 4.0 litre engine on the road, all this boils down to is minor revisions to the parts that give our race engine 450hp, unfortunately this all takes time and money of which we do not have an endless supply (unlike all the "theoretical" tuners out there).

Our initial work was and is still focussed on the high hp engine simply due to customer demand, but that said 9m are currently looking into the option of "detuning" our 4.0 litre race engine by fitting a new intake/cam/exhaust package which includes 100 cell cats and hence make it emission compliant (subject to correct mapping).

This will probably reduce the peak power rpm from 7300 to below 7000 so it then would make perfect sense to impose a 7500rpm limit which would also extend the life of the engine to a similar level as a TT. All our parts are lighter/stronger than standard Porsche parts and are designed for the race engine which runs at 8500rpm maximum, so longevity should not be an issue.

mamoroso

I think you hit it on the nail. But I think it is possible.

HP=torque*RPM/5250

With lighter pistons, valves, rods, retainers, spring etc you can easily spin these engines at 7,600-7,800rpms

So at 7,600 you need to make 276ft-lb (373nm) torque.
Assuming a drop of 10-12% from peak torque to max hp rpm torque it means that your engine needs to put out 310 ft-lb (420nm) max torque.

The 3.8RS engine put out 355nm max torque. Now let's say Porsche was a little conservative and bump this to 370nm. The increase in displacement (from 3.75l to 4.0l) should give you already 395nm. Then a decent exhaust should give a little more torque. Add Motec and 420nm is not impossible anymore.

Instant_g is building my 3.9L (CMW P&C) engine. We are using custom heads, lighter pistons, rods, valves, springs etc to be able to rev the engine higher.
Cams are the DC-62. Peak HP should happen at 7,600rpm. We are not using the Vram but individual throttle bodies (I will lose some torque there) as I optod for max throttle response ove max hp. Motec M600 is the ECU.

We'll see what results it will yield. I am hoping for 375-380hp at the crank.

I am planning on using it as a daily driver, mated to a G50/31 transmission.

NineMeister

ITB's would only lose torque if there are aspects of the ports/cam/valves combination which are not in harmony. We have no problem finding over 500Nm from our 4.0 litre with ITB's (as shown on the dyno plot above) so as long as the builder has got the model right for your 3.9 there is no reason why you could have your cake and eat it.

Rassel

Colin, indeed I have.
My point was to "not confuse displacement with the HP output". There are design issues with the M64 engine that makes displacement increases to cause issues. Some already mentioned. So if someone wants +400HP - just displacement increase isn't really a good suggestion, the route should be different. The target is probably a power output around 400hp, question is - "Should you go 4.0L for that?". Now, I know you know this already, so it wasn't really intended to you..

mamoroso

Check out this link... you can go up to 4.2l...

http://www.cmwmotorsports.com/engine_kits.htm

RallyJon

I've searched here and on Pelican in the past and haven't found anyone who's built a big cmw motor, much less dynoed it or driven it around for 50k miles.

NineMeister

Here is the comparison of the 9m 4.0 litre 964 engine against a stock GT3 and a GT3RS as promised earlier.