Robin 993 c2

This is a follow on from my first thread, i hope that this one will not dissapear.
The theme of the thread was my engine ungrade. I have had a top end rebuild with new billet heads, new valve gear and a new RS flywheel and clutch.
The current status is that the car is going back together and i should pick it up in Warrington and drive it the 250 miles home on Wednesday.
I am very excited as the engine was making 260 hp when i dropped it off at 9M for the work, it has been tested at 350 hp, corrected and 369 hp uncorrected at the flywheel.
I will let you know how the driveability is after i have had a good drive.

TheOtherEric

Robin-
Do you know conceptually how this improvement occurs? It doesn't increase the displacement, I assume. So how does this work? Merely increasing the compression ratio?

I want to understand the "hows" so that I can figure out what the possible downsides or risks are. We're anxious to hear how it turns out!

Bill Verburg

HP is directly proportional to the amount of air moved through the engine per time unit of your choice, and to the thermal efficiency or extraction of useable work from the heat content of the fuel.

Process more air and you have more hp

paths to this end

• displacement
• cams
• valves
• ports
• rpm

most if not all of these process more air at higer rpm than low so that street driveability suffers. Usually a moderate dose of several or all give a pleasant boost across the rev range, tho usully still w/ an emphasis at the top.

Additionaly improving the thermal efficiency helps to get more out of each liter of gas, to that end higher compression, keeping heat in the exhaust and out of the intake, quality of the mixture, spark timing etc. all help

Atgani

Colin has done a lot of research into the port sizes on the 993 heads, and found them to be of a less than optimum shape and size. It is my understanding that a large part of the increase in HP comes from the heads improvement in this area.

Robin 993 c2

The ports in the head are the biggest area of improvement. As i understand it the ports in the new heads are slightly smaller, this gives a higher gas velocity, which improves the volumetic efficency, or in layman's terms the filling of the cylinder. This would not work, but the shape of the port has been fully optimised. The cams are a little 'wilder' which also improves the filling of the cylinder. The suprise to me was that there was no loss in torque compaired to the standard power curve. I will post a power curve once i have worked out how to do so. The engine should be driveable and nice for road work.
I use the 993 as my daily driver and wanted good reliability, so have resisted the temptation to increase the rev limit, as a result reliability should not be hurt.

'95 993

Robin, keen for your real world feedback, I had the cams, valves, remap and L/w flywheel and clutch in July, but didn't go for the heads, I have just finished talking to colin about getting the heads fitted as the next stage.

I loved the stage one, especially at the track - have done Brands, Goodwood and Combe with the stage one and it flys, a stage II would be awesome

Please let me know how it feels, a PM would be fine

many thanks

John

Robin 993 c2

John
I will give feedback as soon as i have some miles on the car. If you are interested i am willing to take you out for a drive, then you could see what you think.
Quite a fan of Rennlist, i am new to it, but it allows us, the ones who are interested in the engineering, rather than just polishing to exchange our ideas. If i can help you make a decision before putting your hand in your pocket it would better for all. It was a very big decision for me to go for it, risky being the first.
Robin

Geoffrey

Additionally, Colin's cylinder heads have a slightly revised chamber which optimizes the squish area of the stock piston. What this means is that the air/fuel mixture is forced to the spark plug where it is ignited faster and the burn is more efficient. The ignition timing requirements are then reduced which means that there is less pressure fighting the piston on the way up near TDC (less of a torque loss). It also raises the compression ratio slightly which basically will restore a 964/993 engine from the 10.5:1-10.7:1 compression it actually is to more like 11.1:1-11.3:1 it is advertised to be from Porsche.

Christer

Colin has worked on my car as well, I didn't use his heads (in fact I don't think they were availbale then - this was 18 months ago) but I do have 3.8 Cup pistons, Carillo rods, Titanium valve train, 310degree cams, full Motec and I think the best result on the dyno to date was 315rwhp and around 313lb/ft. I also have LWF, LSD and so on. I think the car is great now, but as mine was a custom build I could probably spend a lot more time on the dyno mapping the fuel at very low revs....there is some minor surging at even throttle when the revs get very low. Not a problem, but it makes the car a tad more tricky to drive in traffic...but then that wasn't the point in any case...

My current rev limit is 7250, but the valvetrain is good for 7.5 and the pistons 8k. Colin advised that although the engine is still making very good power through 7krpm, that for a (mainly) roadcar it wasn't worth extending the rev limit any further....

Caveman

I've seen Christer's car and it is an awesome sight and sound! Mark's on the other hand is a perfect sleeper...

Christer

Thanks Cave, I am not sure why my car sounds the way it does although when I was at Brands for the Porsche Festival this year, I noticed that Colin's car makes a very similar sound. I did ask Colin but I don't remember what his take on it was. It might have something to do with the cams/timings...?

Caveman

Well it certainly sounds good. Mine sounds like a couple of old Panzers when it is ticking over! Should be good enough to frighten small children and old folks!

Caveman

I forgot to add that Colins sounded fantastic at Brands; especially when he booted it off from the start point. Having said that there was some old 3.0 RSR or something that sounded incredible and was barely controllable as it weaved its way up the slip road - makes for a nice video clip!

Cheers,

David

agdamis

Gentlemen,

Please keep us up to date on this on this side of the pond. This is extremely interesting. Does this kit get exported to the US? Will it pass emissions testing? Does Colin have a website that explains this in detail?

Robin - Your driving experience on street and track will be very valuable to us.

MPB993

My problem is how to I convince my SO that I need to put these heads/cams on my TPC'd sleeper. I must be dreaming again.