Just a quick note to announce that following the interest shown in the 9m/4T billet heads we have decided to produce the second version of the head to fit the 993TT and GT2 engines to fulfil the requirement of a superior product than the stock part.

The drawing work is just about complete and we have ordered another batch of extruded 2618 alloy material (F1 piston stock) to manufacture the first run of 10 sets. These will have the same port & valve details as the n/a head, the only revision planned will be the fire face extension to suit the shorter turbo barrel. The machining time is pretty much the same as the atmo head so allowing for a minor increase in material costs we expect the head to retail in the £800-850 each bracket, supplied fully finished with guides and cut seats for 50/42.5mm 8mm stem valves (9mm bore Porsche guides will also fit).


Just in case anyone has been living in a dark place for the last 6 months there is a lot of information about the n/a version of the heads on these threads:

https://rennlist.com/forums/993-forum/243898-engine-upgrade-993-a.html

https://rennlist.com/forums/993-forum/260509-9m-heads-make-350-bhp-on-n-a-95-993-a.html

 

Quote:
Originally Posted by LAT
Assuming these heads work as claimed. Would there be similar advantages to using them on a Turbo engine?
Has anyone tried?

LAT




A 993TT version of the head is currently underway, I did mention this on the 993 turbo forum recently but had no response to the post so I have not followed it up. There is a large high demand for an improved turbo head for GT2 race engines which appear to "melt" standard (& other billet) versions with ease and we are confident that the 2618 material of the 9m/4T head will withstand a lot more heat cycles and perhaps improve reliability & duration between replacements.

What I can tell you is that the turbo head will be twin plug and have the same high velocity ports & valve sizes as the n/a version, there will be minor differences elsewhere as you can see in the lack of lower cooling fins on the CAD model. We may also go with smaller spark plugs to follow the trend of the GT2 evo engine.

Here is a CAD view of the redesigned GT2 head, showing the revised fire face to suit the shorter cylinder and piston intrusion of the TT engine.
Attached Images


Can I get some input on this head from the turbo guys...Kevin, PorschePhD...anyone?

They sound pretty good, would they allow you to push the power envelope further?

 

I have no experience with these heads at all, I have read a lot about them, and they seem to be very good, certainly nothing like the other aftermarket billet heads being sold at 1/4 of the price.. I have reservations however about the performance gains, on anything other than pure race engines when it comes to the turbocharged variant, unlike the N/A ones.

Foryorent, I am surprised there is such high demand for solid GT2 heads, one can probably count with two hands the race GT2 EVO engines out there still being run in races, and out of those that are, I wonder how many are melting the race GT2 EVO heads as you mention. I think that the melting GT2 EVO heads are those that are being run on poorly tuned lean engines or highly boosted on EFI systems beyond their natural resistence characteristics.

The N/A heads are more efficient than the TT heads, but there is a reason why those valve sizes are smaller on the stock turbo engine, maybe not so on high end race engines that don't care much about drivability and they use very aggressive cams.

Until now (not saying that is carved in stone) , the likely most experienced 993 GT2 EVO race builder uses stock OEM GT2 EVO heads on his most powerful racing engines, although he knows thoroughly about the similarily excellent Perfect Bore products, that use the same forged 4032, 2618 and SF9 material than these. ( I have no clue what they mean)..These PB guys have among their customers F1, NASCAR, Le Mans, ALMS, WRC, Moto GP, BSB, Formula Nippon, A1 GP, F3, V8’s, WTC, IRL, Porsche Cup as well as OE special developments so their credibility is up there as well with 4T.

Customers for these heads also need to know that they will most likely have to move to an aftermarket EFI setup, I don't know many who can tune properly a twin plug Bosch Motronic 5.2 ECU to go with the twin plug heads and deliver the performance in a professional race environment for which these heads are most likely intended? That is an incremental cost as well.

The way I see it, IMHO, 99% of these turbo engines can get away with the stock OEM heads and mild flow improvement for all the way up to serious club racing, by reinforcing and welding for flame rings like Kevin has done, and the process will be much cheaper.

I do believe that these heads will bring performance upsides vs stock, unlikely vs. GT2 EVO ones though with also larger valves and worked ports etc.., however these performance gains should be sought for only after everything else has been done, namely state of the art ECU mapping and intake and exhaust modifications, getting rid of the MAF setup to name just a few. On a highly tuned street performance engine with the most efficient intercooler in existence, these heads will not give you any performance North of 15 HP if any, vs. a similarily built stock head twin plug engine.

Net net, for the serious professional racer, these heads will be great, while maybe not being better than the GT2 EVO ones, they will deliver that ultimate response. I would love to test them of course as they seem very trick.

Sorry for asking but are you related to 4T? you use the "we" all the time, it would be great to know.
Thanks.

 

I have a set of the N/A 9M heads and have done flow bench comparison between 964 N/A, 993 N/A head, 993RSR heads. I found that particularly at the low valve lift area that the 9m head has substantial velocity improvements over any of the aformentioned heads and continues to have improved velocity all the way to .550" of lift. I have the heads on my engine and am pleased with them. I do not have back-to-back comparisons between the various heads and the 9M heads, however, my engine produces as much power as another engine with higher compression and racing fuel where mine is lower compression and runs street fuel.

From my experience with the 9M heads, I believe they proved a better "area under the curve" than a stock or ported stock head including the 993RSR due to the increased velocity that fills the cylinder better and more efficiently than a similar increase in CFM airflow.

The 993tt and GT2 engines both have smaller intake and exhaust valves than a 993 varioram engine and smaller exhaust ports than any of the 993 engines and is the same size as a 964 N/A engine.

I believe that 4T also is an engineering firm for various F1 activities.

As for a turbo engine, my experience with various ported heads shows that an improvement in cylinder head flow will improve torque and HP. So, assuming the 9M turbo heads are as good as the N/A version (they should be since the port design is the sam) they should produce increase power. If you are going this far in search of power, a custom camshaft is recommended so it can take advantage of the specific design of the heads.

 

Geoffrey

I am not sure the experience with the N/A engine applies to turbocharged engines. I do not believe that flow is in question either, I am sure they flow better,and I believe the heads are of very good quality, but it still does not mean that they will make any substantial or worthy difference in a highly tuned street engine. I also was comparing vs. GT2 EVO heads, since it was the question raised by the poster, saying they were melting, and better ones were needed, which I dispute.

I did read that 4T supplies F1, which is why I said above that the other company also has its credibility up there with 4T, as both are suppliers it seems.. Not that it matters anyway, they are both great, maybe not a worthwhile TT upgrade though? I am interested in the tech aspect of this.

 

I have just been in the market for new heads - too many "skims" = too high compression ratio

I did some research and asked a lot of questions from people who know the most about Porsche Turbos and in particular racing GT2 EVOs.

The Perfect Bore stuff was available and known (RS Tuning use the PB stuff for the big bore GT3 RS engines), but I have gone the tried and trusted route of brand new Porsche 3.6 race heads modified to GT2 EVO 3.8 specifications.

I have zero idea whether these new heads offer any real world benefits - it seems for a street engine which stays under a real ~600PS the GT2 EVOs stay together pretty reliably.

I realise I am the cynic but I would have to see evidence of these heads used by the likes of RS, Manthey, Ruf before I would consider them worth a look.

BTW if a 9M built 993tt/GT2 (same weight and gearing as mine) with the new heads ever beat my car in a 60-170mph then I will be retracting the above statement in a big way and be begging to be sold a set

 

Thanks for the input guys!

Just to clarify, that was not my post, but I tried to copy a post from the 993 N/A forum where the 9m guy posted this. The entire post but the very end where I ask what you guys think about these in a TT application is all from 9m.

Basically I was wondering if these would be on the list for someone looking to build the best, most powerfull, most reliable 993TT engine possible. It looks like you can go all the way to 4.0l with the N/A version of the heads, wonder how much power you could make out of a 4.0TT engine.

I was hoping that the billet heads would allow for more boost without causing reliability concerns.

 

The 9M heads have several key benefits that apply to both N/A and turbo engines alike. I see these benefits as equally important as the port flow.

- They are made from 2618 alloy which is a stronger alloy than the factory uses for the 993tt and GT2 Evo heads. This allows the head to keep more integrity and resists bending or lifting.

- They have a much better support at the sealing surface. The first two fins on the 9M head are a block design rather than the two separate fin design the factory uses. This allows for a much stronger sealing surface which keeps the combustion in the cylinder. Many shops will weld the first two fins on a factory head (I think Kevin has some picutres in his 8500rpm thread). This helps keep the head integrity.

- They have harder, better valve guides and seats than the factory uses.

- They have a revised combustion chamber which is slightly smaller than the factory. While this helps restore the loss of compression from advertised compression (Mahle pistons are never the advertised compression), it also provides for a better squish/quench of the combustion mixture. The latter would be a better benefit on a N/A engine with the significantly raised dome compared to the tt piston which isn't.

I think the first 3 will allow for higher boost pressure than a factory head, espeically when dealing with the higher cylinder head temps that come from increaste boost.

 

foryorent
Sorry about that, I thought it was you posting! Maybe I should not have revived this thread.

TB, thanks for sharing your experience, if RS Tuning uses those PB heads (with similar alloys and credentials to the 4T) for some of their N/A applications, it makes me wonder why they don't for their high HP TT engines.

Geoffrey, your points seem to point towards the stronger material of these heads vs the GT2 EVO ones, I am not an alloy engineer, but do you know what the factory GT2 EVO alloy is, in order to state that the 2618 alloy is stronger, or this is something 4T has stated? The same questions go for the valve guides and seats, what is the difference in alloy composition in order to say that they are better.

Also, the GT2 EVO race engine failures did not come from the heads melting, the heads just had to be refurbished after about 40 racing hours. The breakage was coming from components such as the gearbox or other bottom end internal engine failures such as the rods and bearings.

While as you rightly say, harder components help being able to use higher boost, this is not the solution for racing engines for which these heads would be designed, the key is to use lower boost to get the HP you need, not to raise it, since while the heads will resist, the thermal stress on the other components on a race engine won't with higher boost.

I am interested to find out about the performance gains these heads would see on a turbocharged engine now that the N/A benefit seems to have been established.
Thanks

 

Hi Jean,

I realize that you (and others) feel the GT2 Evo is the holy grail of turbocharged air cooled engines. I don't share that same sentiment. Although a great car in its time and one of my favorites, improvements in technology allow for an engine that surpasses it in terms of performance and longevity.

I'm not a metalurgist, however, the GT2 Evo heads are made from the same RR350 aluminum alloy as any 96 and later 993 head (N/A or TT). The heat treating process for that alloy is that it is heated to 1100F for 5 hours then quenched in boiling water. Then it is heated in an oven at 425F for 16 hours and allowed to cool by air. In the end you have an alloy stable to 425F or about 218C. The 2618 is a piston alloy used for pistons in F1 and has a far greater resistance to heat. Knowing that F1 pistons are critical parts and are required to withstand high forces, 2618 is used.

As for the guides, Porsche uses phosphorous bronze guides similar to the ones found in a stock head. They are known to be soft and have premature wear. The difference is that the exhaust valve guide is surrounded by ceramic to help it keep its structure under the high heat is sees. The 9M heads use a harder valve guide. I can tell you from my experience with the heads when final machining them from Colin that they are much harder than any Porsche valve guide and seats I have worked with. The aftermarket valve guides and seats that I have been using in the stock Porsche heads are also much harder and have better cooling properties than the Porsche guides so I have no reason to doubt the performance of the guides Colin is using.

I don't know much about GT2 Evo successes of failures as I've only seen one set of GT2 Evo heads and not the entire engine. I could not comment on direct experience other than to note what is in my GT2 Evo parts manual. Given that the crankshaft is a stock 993 part I'm not surprised that there were crankshaft and rod issues. If I recall correctly, the engines used various restrictors with 33.8mm being the largest and also ran with limited boost to .8bar.

I also don't diagree with producing a more efficient engine which utilizes lower boost. This has been the philosophy that I have followed when designing and building my own turbo engines. I also believe the 9M heads strength and improvements go beyond expanding the performance envelop and will also increase longevity of a turbo engine.

 

"wonder how much power you could make out of a 4.0TT engine" Already asked. Reply was that you'd be facing heat issues, therefore not advisable.

Colin of 9M has faced enormous scepticism re the power output of his na engines. But he delivered. Therefore, I'd give him the benefit of the doubt.

 

I am also a sceptic when it comes to parting with my money! This is a most interesting development that I would like to see how it unfolds. I do not subscibe to the idea that only the factory knows best-- particularly in the 993 GT time.A lot of development ideas came from outside at that time and the race department did not have the budget for too much R & D.Compromise was the order of the day.The last 10 years have seen significant gains in technology and know how-- and that particularly applies to turbocharging.The fact is that the 993 engine was superceded and factory development ceased long ago-- those of us still with an interest in these engines should not believe too strongly "that the factory knows best" as even if this was the case improved experience and knowledge should open the way to better and improved engines.One last comment-- I have always been told that to build a good turbo engine you basically build the best N/A engine and tailor for turbo ,and as far as N/A engines go Colin's heads seem to be producing more power than anyone has achieved previously!

 

Geoffrey

Thanks for the info. I still have not understood how stronger are these heads and whether we need stronger heads on our TT engines rather than weld and prepare our stock or GT2 ones. Your experience with them is based on your N/A engine and I am not sure you have tested them thoroughly yet.

Let me say it again to avoid going back again and again on this topic, there was a question about how good these heads would be on a TT engine, this has nothing to do with 9M or 4T, I am sure that these heads are great for N/A engines, but I doubt they offer any substantial benefit to turbocharged engines on this forum, which is what the initial question was. Also, the "melting GT2 EVO heads" comment is inaccurate.

I don't buy a product just because the supplier is an F1 supplier, I want to understand what it does to me. Is there any GT2 or turbocharged Porsche race car using these or similar alloy heads? The heads with 2168 alloys have been around for a while now from different suppliers. I might have a 24hour race soon and would like to have facts before a rebuild.

I do not think that the GT2 EVO is the holy grail of anything I don't have any of their components on my car, we are beyond that argument.

The RS comment from TB cannot go unnoticed (nor the challenge ),

Is there a link one can read about the performance of the 9M N/A car fitted with these heads and were the details posted about weight, conditions etc..? It is out of genuine interest, not scepticism since I know they will do great in N/A.

Avoyvoda, good to see you here, I do think these are the ultimate upgrade to your N/A engine and I always said it. When will the baby be ready?

As far as 9M HP claims, the stock K24 550HP TT and GT2 cars disappeared unfortunately before we could measure any runs, if you know of any out there that would be willing to use an AX22 to kill that overstated HP debate please let me know.

 

Jean
I am not certain that RS uses the heads from PB, just the pistons/liners - I think the set up is the "property" of Cargraphic, they commissioned the 3.9 specification etc and it was built and tested by RS - one can read about it on trhe CG website and I don't think it mentions heads ?

Red9
When I "throw around" GT2 EVO I am not reffering to Porsche Motorsports specification, the racers took these engines further and further.

Today's RS Tuning race GT2 EVO Secan engine produces ~670PS, back in the hey day they were making more like ~620PS for racing - they have moved things on and I believe the heads have moved on with it, I know for a fact they are using latest valve tech in 2006 GT2 EVO heads and am guessing there will be other stuff in there - so we're definately not on the "factory knows best" band wagon here

Avoyvoda
Following Colin's other attempts with the 993tt engine and his claims that he has a "more complete understanding of the management system" than RS Tuning when he uses fixed boost controllers and believing silly chassis dyno figures - he will need to build something with these heads that really performs and performs better than the latest GT2 EVO heads before he can get the credibility back IMO.

 

TB - you are right in suggesting it is up to the promoter of the benefit to prove his product, and we do know that he contributes to this forum.One of the terriffic benefits of the internet is that products,ideas and concepts can be exposed,promoted and refined from knowledge that would have taken much longer to get to the bottom of previously.Hopefully it also saves us all the expense of dud products and promoters.The otherside is that we should not be too quick to condemn those brave enough to expose themselves to the scutiny.As has been generally agreed-- dynos are not internationally reliable method,1/4 mile terminals are interesting and 60-130 only tell us something when the data is published,or, perhaps when it is not published.