NineMeister

This is a serious technical question that I hope someone out there can help me with. We (9m) have been looking at the 968 engine design and have come to the conclusion that with the 104/88 bore/stroke ratio the best way to get real power out of a normally aspirated 968 engine is to allow it to rev at anything up to 8500rpm. I know all about #2 bearing oiling issues, but does anyone have definitive solutions for really high rpm use?

Alternatively I have heard that Bob Norwood's Doom2 engine ran at or beyond this level, so can anyone provide information on the project or specifically the mods done to the bottom end?

Thanks in advance.

dualblade

i dont' actually have an answer, but a question about the factory redline. what component or components set the redline? anotherwords, what are considered the weakest links? i know alot of chips bump the redline up to 7k but what stops it from going farther? how are our injectors as far as usable pulse duration remaining? perhaps to get to 8500rpm you'd need more than 100% of the stockers. i'm sure you guys have thought of this but it's just stuff i'm curious about

AznDrgn

you probably know this already but the obvious things that go into a high revving engine would be:
1.) balance the entire lower end as close as possible
2.) knife edge and cross drill the crank
3.) upgrade the valve train with heavier springs and the neccessary components to handle the heavier springs so you prevent valve float.
4.) get a cam that is going to give you power at that speed

Porsche-O-Phile

Why would you want to? The engine will be well past its power curve point revving that high and although you might be able to build it to take it, it will certainly wear faster.

josephsc

I believe this is part of a long on-going development by 9m racing to fill the demand for more power to the 968 engine that 1) doesn't lose the A/C as is the case with SFR/9m racing supercharger kit or 2) cheaper and less of a hassle than a full turbo conversion. Very exciting stuff: see here, start at around page 13

Colin, I hope you find the answer you're looking for!

iloveporsches

Tune it with custom parts and you can move the powerband where you want.

Zero10

I believe the valve-train is the first limiting factor. Solid lifters would be ideal, but at the very least, heavier springs. I don't think the cam needs to be changed.

As things presently stand, the N/A heads just don't flow well enough past 6000rpm, so you would be looking at low-restriction intakes as well.

Now, I would image around 7000+RPM you'll be in trouble in the bottom end. Forged rods would be a good idea, but perhaps the factory rods will take the added stress?
Main/rod bearing oiling would be important. Cross-drilling may help with the issue.

Knife/edging the crank, and balancing all rotating parts would help for sure.
I don't know for sure, but I would imagine the timing belts and such would be fine at those revs.

Perry 951

Provided they stay at the factory tolerances. A kevlar belt would be ideal.

Predator

A na 968 cylinder head can't flow enough air to support big horse power at that rpm. You'd have to pressurize (turbo/supercharge) the motor, and then you have the problem of size/efficiency. This is all possible, of course, but streetability would then be the defining factor. I'd think that 250 hp is approximately limit for a na 3.0 litre 4 banger. A little cylinder head work, higher compression, different camshaft profiles, some good exhaust work, is about all that can be done with these motors. A 20 to 25% increase would be very hard to realize from just these changes.We had a 2.5 motor (8v) with extensive head work, 13:1 compression, radical camshaft (damn motor would not idle below 1500 rpm), and 2 inch x 28 inch primary tube hedders with a 12 inch colector. The motor made 201 hp at 7100 rpm and 200 ft lbs of torqur at 5400 rpm. Completely unusable street engine. The last time I saw this motor it was at my brothers basement, sitting on the floor with a sheet over it. Then we changed over to the LT-4 motor and enjoyed a whole set of new adventures!

hosrom_951

I could be wrong here, but to increase revs on NA and Turbo modles (single camshaft) would need these:

1) Sports Cam
2) Lighter Rods (Pauter/Carrilio possibly even titanium)
3) Drilled Crank, Balanced and lightened
4) Ligher valves/springs/lifters (Titainium)
5) A standalone engine management/Piggy Back with timing control

Now, i may be mistaken on a couple of things listed above. However, we are talking about serious $$$.

The NA 16v engines would could more, since there are TWO camshafts to adress. The most crucial and best upgrad would be a standalone, since you would have complete control on the system......

I know members pushing ~7,000-7,300 or so on Turbo models but 8,500 sounds like an over kill.

Also mentioned above by Predator, you would definately need to increase airflow, so even if you can get your hands on camshafts/valvs etc you would need some P&P, Intake Manifold and even a MAP/MAF. Even then, i don't think 8,500 revs would be reached........

Again, don't quote me on what i said, what i mentioned above is how to 'lighten' internals, thus allows higher revs........

Chris_924s

It's not designed to rev like a Honda S2000.. But I do like the idea.
IIRC from my old V8 days, you can run a balanced and blueprinted well beyond 7000, up to 8k before initiating damage sequences.
I suspect the nature of a 4cyl (i.e. less moving parts, less centrifigal weight) would actually optimize torque around 6K.. obviously the potential is much higher- look at some 4cyl bikes..

Predator

You can try using the math ( smokemup.com). This site has the formulas to calculate how much air you'll have to flow to produce a given amount of horsepower. It's fairly simple. It will also guide you as far as engine efficiency (nothing flows 100%). Once you know how much horsepower you want, how much air your motor will flow, then you need to know if your heads will flow that much. The site will also help calculate injector sizes and all kinds of good stuff, like how much horsepower it takes to reach a specific mph in a 1/4 mile with a given weight. Supose you want a 110 mph trap speed in a 1/4 mile with a weight 0f 2900 lbs. With an estimated drivetrain loss of 20%, you'd need 262 rwhp. It's a fun site to play with.

Matt H

NOPE. Just dead wrong. There are a few 250HP 2.5L NA motors and one or two tuners have made over 300.

The only things that are certain in the this world are:
Death
Taxes
Your ability to make HP is directly proportional to the size of your wallet

An NA 3.0L with the proper tuning and parts should be able to easily crank out 300+, again depends on the size of your wallet. If you are serious about making power then you should talk to Jon Milledge, Bob Norwood, and Scott Gomes any of them can build you what you want. Bring an accountant, it wont be cheap.

9M, Norwood has done some incredible stuff, he did a 928 that is just incredible. He is in Dallas off of loop 12, I can get his phone number if you like.
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86 951 Driver

No offense but the 3.0 motor is not a honda motor. It is a torque monster. Just rev to 7000 rpms and be happy. If you want to rev high get a 2 stroke Moto GP bike like me. I like have power everywhere in the powerband instead of in the upper rpms.

Matt H

He is trying to make more power, part of doing that is RPMs. You are also not talking to a 12th grader with a dream. Ninemeister is one of the UKs tuners.

Lastly, attitudes like that are the reason there is no 944 development.
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