Caveman

That old saying "if it looks right it probably is" comes to mind...

ed devinney

I am not an expert, but everything I've read about ports says that eyeballs are terrible guages of performance. Big, smooth ports are alluring but no guarantee of performance. Port shape, proportions and other aspects turn out to be at least as important as volume and finish, if not more so.

Flow isn't always enhanced by smoothness, and it may be that the factory ports aren't further finished because there is little to be gained given the costs involved. These are production street motors after all.

SimonExtreme

While I agree with this to some extent, the differences between the heads are very marked and when an F1 engine designer points out the differences between them and what is "bad" about the OEM ones, it makes us all experts!

The interesting thing about these new heads is that they don't have huge polished ports. In fact, I wouldn't be suprised if they weren't fairly similar in size. While they weren't polished (that creates its own problems), at least they didn't have major ridges where the ceramic liner didn't fit properly. In addition, there are some very significant differences in shape, particularly the removal of a significant hollow.

Results on these heads are provable on a flow bench, rolling road and on the road itself. maybe, knowing that, it makes it easy to say "its obvious why this head is better"! It still doesn't explain what seems to be unusual design features in the OEM head.

pcar964

OK, so back to the point - we need to figure the best way to get these into NA, and that's going to require either an engine builder or just a method of distribution. Am I right in saying that the only sticking point will be the live engine remapping?

AVoyvoda

"It still doesn't explain what seems to be unusual design features in the OEM head." Excellent point. I for one, would love to hear an explanation how a bunch of chaps from Warrington (talented and all that, but no match to Porsche's resources) can find 50 to 120 hp (na road version) from the engine that powered Porsche's flagship range for 9 whole years. Better materials and better fuel, will of course make a difference and so does MOTEC. But it can't be the whole story.

Caveman

I've heard that they never landed on the moon and that George Bush is secretly not an idiot.

If those heads were the result of development stretching back to the original Peoples Wagon wouldn't there be some advances in both flow theory and construction design/methods. Don't forget that those guys in Warrington have retained the services of some pretty skilled F1 designers (and let's not get into Porsche's crappy F1 engine). Given that we have dyno and road test evidence I'm willing to believe it.

SinVancouver

Also remember the package is not just heads but cams as well.. Porsche has to run a pretty wide tolerance level for many reasons.. ninemeister only had one customer and one goal.. its apples and oranges.. plus we all know Porsche almost always designs to a number...

SimonExtreme

It's not a bunch of guys from Warrington! The head has been developed by one of the leading motorsport engine design consultancies who have a very good track record in many branches of the sport and specialise in F1. Surely it would be a much bigger suprise if they couldn't produce a better head!

When you take off the constraints of manufacturing to a price and in quantity, it opens up lots of posibilities. To find the power you refer to, you change many of the key components - heads, cams, valves, intake system, exhaust system, engine management plus in some of the engines, they increase capacity. In addition, when you do the maths properly, as shown above, they are still some way off the theoretical maximum.

What I would like to hear is an explination as to why some people are so sceptical and why they think Porsche would have done such a good job in the first place.

'95 993

Bunch of guys in Warrington, come on we all know it is Eddie Irvin and Tom Cruise, I saw them myself when they worked on my engine.

Nothing like celebrity tuning :-)

Jean

SimonExtreme, where can we read a little bit about 4T's background and their very good track record, other than what we read on this forum and hearing that they are F1 suppliers and some of the leading design houses in the world?
BTW Avoyvoda is not a sceptic (I am indeed, it's a disease) he has his engine being built by Colin.
Thanks

AVoyvoda

Naw guys, don't get me wrong. Tom Cruise has my respect. I am a customer to boot. Just wondering if Porsche left some power "on the table" in order to better differentiate between the na and the more expensive turbos. Perhaps some of that - and more besides - has been found by TC and his crew. Let's not forget that in the early '90s Porsche was facing closure, so one has to assume they pulled out all the stops.

Red rooster

I would still be very interested to see what these heads, with no other mechanical changes - cams, exhaust , etc - will do.
From what I have seen those cams may very well make the motor non OBDII compliant . Important stuff in some parts of the US.

Flow benches and fingures up ports are good talking points but can very well have no bearing on power output ! There is a little more to motor design than that .

All the best

Geoff

N51

Geoff,
Good questions. Could you provide more specifics as to what cams have caused non OBDII compliance? As you have not seen 9M's sport cams, what are the related issues?

I agree, and such talk works against 9M's labors. Patience will be our friend.

Noah

epj993

You gotta remember that was about 9-10 years ago. I wonder if Colin & his group could do this in the '95-'98 time frame considering the technology available then.

Also, I think you're assuming that Porsche was trying to squeeze every ounce of power possible out of the 3.6. Probably not as car manufacturer's usually meter out performance over a models life span to be able to claim improvements from year to year. I think they had to balance performance with cost saving measures & marketing to save the company with the 993.

All that aside, since you're a customer I'd love to hear your report on your 9M upgrades when they're completed.

NineMeister

Whilst Simon mentioned port sizes I will reiterate a comment that I made on an earlier thread. In testing all the variations of stock Porsche heads that fit my race engine, the one that made the most power and torque across the operating rpm range of the engine was the one with the smallest port - the 964.
The second significant difference of the 964 head in comparison to either the 993 or 993RS head is that it has a shallow bowl under the intake valve, the net effect being a straighter port. The less you turn air flowing down the port the more energy it retains, thus a straight port is of the highest priority in performance head design. Why the 993 went away from this is a mystery, but my guess is that Porsche replaced their head designer sometime after 1989 (964) and the new one got the numbers wrong.
Port size and profiles are critical in the approach to the valve and around the valve guide, but fundamentally any engine has a finite limit to the air flow that the cylinder demands, thus the optimum port should be sized to match the maximum flow demand of the cylinder (allowing for capacity and rpm) in order to achieve a high intake velocity.
Get the sums right and the torque increases significantly - get the cam right to the intake/exhaust and the torque is maintained further up the rpm range and this means more power - lots of it. So what you have in the 9m heads (aside from material, combustion chamber shape, etc) are ports optimised within the geometry limits of the Porsche installation (valve sizes, port locations, etc), they do not flow huge numbers because the engine (even in 4.0 litre form) does not demand it, but they do maintain a very high intake velocity which is key to producing a high volumetric (cylinder filling) efficiency.
There may even be more to come in the future if we stray away from Porsche valve sizes and port locations, but for now what we have we believe is the ideal compromise to suit a variety of engines from the stock 6800rpm 3.6 engine to the wildest 8000rpm 4.0 litre, and the measured road performance suggests that we got the numbers about right.