AVoyvoda

"When will the baby be ready?" Hi Jean. The engine is being built as we speak (4 litre na, road version, expected around 400 hp, redline 6.8 - 7k, car weight 1,200kgs retaining all the luxuries such as aircon, full soundproofing, power steering, airbags etc). Going to see them tomorrow to review progress and deliver some uber-components I have sourced in Germany.
Seriously pondering whether we should go one step further and fit a compressor too, thereby increasing power beyond 450 hp. At that point you'd be looking at power to weight in line with a CGT. Not as powerful as your beast, of course, but the overall aim here is different: to produce a great non-turbo road car, 2wd cabrio, without a fixed rear wing.
As one of the "originators" of the 4 litre engine (placed the order and deposit back in September '05) am very pleased that the results are in line with expectations. You can be sure I'll borrow your AX22 when all is ready.

Robin 993 c2

Out of interest here are a couple of failed heads, one has failed the head gasket the other, a billet head from another supplier has yeilded around the head stud. I am told that these failures are not uncommon at quite low hours in race use, and that the head to barrel seal is a perfomance limit on these engines, effectivly limiting peak torque.
We are looking at the head stud, nut and the detail design of the head to improve the structure and cooling, we think that there is room for improvement.
You can improve the efficency of the engine and get power for nothing, or just plie the boost on and fix the bits that break, we are planning to make a stronger, more efficient engine
We are always open to input, and don't know it all by any stretch of the imagination, that is why we have been looking at parts and talking to tuners.
Robin

Red rooster

I came across a UK company , BS Motorsport ,that is supplying a novel replacement barrel / head set. The barrel actually screws into the head so there is no head gasket to blow !Lots of very high tech companies involved in the product devolopment .
Might be worth a look if high boost is your thing .

All the best

Geoff

TB993tt

The company you refer to is "Perfect Bore" mentioned in previous posts

Kevin

What are we talking about, $10,000 USD for a set of heads.. The picture shown looks like someone installed flame rings but didn't weld the head.. I also can't see by the picture if it was cut for 102's.. Anyone running a 3.8ltr and not welding the first few fins is looking to repeat what this owner went thru..

If you want trial test a set on US gas, I have spare engine that would be a good platform for some R&D..

I do like the idea of screwing the cylinder to the head..

TB993tt

Whilst I was researching how to go 3.8 litre, here is a reply I got from Perfect Bore:

There are various ways of increasing the capacity of the engine whilst still retaining the standard crankshaft ,
To increase the bore from 100.00mm to 102.00mm raises capacity to 3746cc
from 100.00mm to 103.00mm raises capacity to 3820cc
from 100.00mm to 104.00mm raises capacity to 3894cc
Both the 103mm and 104mm conversions require a spigot bore in the crankcases of 109mm this would be standard on factory RSR cases , standard 3.6 crankcases have spigot bores of 107mm these can be opened out and require a seal detail to be machined

With reference to the cylinder kits available we can supply piston , barrel to suit these applications , barrels can be machined to suit standard nirosist rings , however at the 104.0mm bore we use a solid bronze ring which has proved very successful.Our barrels are manufactured from Forging as are I believe the motorsport parts and are made from a high Silicon alloy which gives good stiffness and a low expansion rate.
With our barrels we believe we can offer a number of options if required , gas transfer ports are machined in the barrels as standard.
With reference to your cylinder heads , the standard heads will obvious convert to the RS spec however these heads are prone to softening particularly if they have been used without the head temperature feed back this may or may not be relevant.I am not sure if your heads will hasve the modification to the lower three fins which have the area between the fins filled in to support the sealing ring

With reference to the screw in liner conversion , it should be possible to modify your existing heads if they are not softened to take screw in liners they do need the fins filled in as detailed above , at 102mm the head , liner seal should be ok up to at least 2.0bar boost how this equates to output I am not sure as this will be dependant on other features.

In order to quote the cylinder heads we really need more details about the specification do you want these based on GT2 Evo heads or on the Perfect Bore Heads , please advise

Following further discussions, I didn't take it any further.
The main reason was, to get my tuner involved sounded like it would turn out VERY expensive, mine would be a test engine, there were no guarantees, no testing on the race track had been done etc etc..... compared to established RS GT2 EVO technology which has been honed over the years and seems pretty reliable.......

Having said the above, I still won't have any guarantees and its still bloody expensive

Red9

The issue of paying for the development of "new" technology is enough to keep most of us on the conservative "known" paths .Saying that -- I also think that those that seek to evolve and develop new or refined ideas should be encouraged - we all benefit.I do think that those that bring these ideas into a public forum should be given a chance -- particularly when they appear here on this forum to explain.This is all obviously work in progress and from personal experience it can be very difficult doing your development publicly.I notice in the 993 forum that Colin is virtually accused of being a liar.The flip side is that real facts are required to back claims up-- over to you Colin.

Miles965uk

I agree with you Red. Ill add my 2 cents

I think its only a good idea that tuners try to keep redeveloping the older engines. I personally love anything that improves something over the factory. Also it keeps me away from thinking that the new engines now being varioram, variocam, VTG etc are perhaps running away from the aircooled brothers one day i will have to throw in the towel... which of course I dont want to!

There was an article this year in one of the UK porsche magazines about the heads. What the article said was that Colin optimised the cylinder flilling of the heads with the relationship between velocity and port size which increases the VE of the engine. I know that there is improvement needed on the stock head and they are ported/polished etc to improve flow already. So these heads must be better than stock for sure, just a question over how much better you can get vs the ported ones.

My limited understanding (correct me if im wrong) is that the heads should increase torque ealier and make the turbo work less harder however they shouldnt increase the top HP much becasue the turbo could just work harder to get to the same VE number (if you are not limited to boost that is )

But like everyone says you need to see the real world numbers...

Woodster

this is why I miss the 993TT threads,

the knowledge base here is unsurpassed!!!!!!!!!!!!

thanks for letting us all listen in a gread public format

Marty K

AVoyvoda

"Colin optimised the cylinder flilling of the heads etc" That's the way I understand it too. Plus the fact they are twin versus single plug, which should improve combustion somewhat. As to whether they make the upgrade worthwhile and are, at the same time, superior to the offerings from RS, Promotive and others, remains to be seen. Unlike for na, there's stiff competition out there.

Kevin

TB, I'd definately be interested in taking your old heads and installing the screw in liners.. Look at his reply.. Good for 2.0 bar.. I just picked up a early 3.8 ltr RS case.

TB what are they supplying or recommending for pistons? Mahle or Cosworth?

Red rooster

Miles,
The 9M heads have smaller/ reshaped intake ports to optimise port air velocity
when used on a N/A motor .

The velocity is flow divided by port area . For a turbo motor port flow is much increased so reduced port size is not the right way to go !

This is not an attack on Colin !! but just underlining that a turbo motor head has some different needs than a N/A.

Those screw in , forged barrels certainly look like a neat idea.

All the best

Geoff

Jean

If I recall correctly (we spoke about this 6 months ago) Perfect Bore recommend to use their own barrels to replace the Porsche (Mahle) Nickel Ceramic coated ones, no mention of Cosworth. They supply their own customs Pistons and rings as well, and the heads can be bare or ported with guides and valves..

The problem with the turbo engines is that you cannot increase the ports aggressively or increase the valve sizes without impacting street drivability, also your limiting factor will be your camshafts and MAF.

The GT2 EVO race engines had larger valves, very aggressive camshafts, and most importantly, had no MAF, which makes a great breather and improved VE, but no low end drivability.

Red Rooster, I might have understood your comment the wrong way , but you seem to say that turbo engines need larger ports, which is the opposite in fact, the TT heads have smaller port sizes and valves than N/A engines, which is partly why N/A engines are much more efficient than turbo engines. Turbo engines rely on forced induction, which also makes the air flow more vulnerable to imperfections in the heads (these heads might bring good upsides here, just as good as well ported and polished EVO ones)

We are talking pure race cars grounds here already. Put GT2 EVO heads on a street 993TT with decent drivable cams and you will not see much HP difference regardless of how great programming you have, certainly nothing North of 15-20HP peak across the RPM range of a street engine. Torque will certainly improve with the 3.8 ltr displacement, even more so with 4.0 ltrs, as long as the intercooler can keep the substantially higher temps at bay I believe.

A N/A engine will benefit greatly form better breathing since there is no forced induction, the improvement will be very dramatic.

Whether these heads are good or not, is not a debate, they are certainly no CMW billet heads, and they will be rock solid and great heads , I just don't know how much we are talking about and how much better than GT2 EVO heads with proper work on them. You certainly cannot go 2 Bar with these engines, something else will break, in race (enduro) environment, you will stay within 1 Bar or face damage in other components.

The question is whether I would do this on a MAF based engine, or a street engine all together, would I be getting the benefits I would from a race gearbox that can cost as much.

Who would be doing the Motronic twin plug mapping? Other things that I see certainly needing change to capitalize on the 4ltr head gains...Intercooler definitely (unless you target quartermile runs), bigger turbos, a Motec EFI or similar, unless there is an expert tuner that can do the upgrade on Motronic and pressure sensing? Any opinions?

Cheers

Jean

Avoyvoda
I am really looking forward to see this car on the street. 4.0 Ltrs and 1200Kgs with the advantageous aerodynamics of a wingless speedster promises to be an animal and I would bet the fastest air cooled N/A in the UK and probably the world. I would leave it N/A , no compressor.

AVoyvoda

Interestingly, now that the power issue on the air-cooleds has been cracked (either 4 litre with or without compressor or 3.8 tt) we need to focus on traction. Colin tells me that his 3.8 na 993 (about 415 hp, 2wd) has no traction in 1st, 2nd or 3rd gear in the rain. Worrysome for a street car. Which then leads us to Motec and its in-built traction control module plus better brakes and 4 channel ABS. Moral being, that there's a lot more required than just a power increase for ultimate driveability.
As to compressor or not, mulling it over. It's kinda depressing having the tt boys kick sand in our faces.