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Nah, don't worry about it until there's a reason for it It's intoxicating pushing the right foot on the floor (I'm just a week of driving with my 924 2.5 16v turbo, hence the exhilaration) but traffic slows down quite good and having driven quite a few times in Holland, I have a feeling that you will get some traffic too
I am still of the opinion that even 350 true hp to the wheels is quite a lot for a street car so the 8v is fine in most cases. Having 500+ like Shawn, Sid and others must be somewhat mind bending at times! I can't imagine how fast our car would feel on the street. Must be a blast but you can get into serious problems seriously fast with that sort of power.
While my experience with 3L 8V of different flavours, mine included, has shown me that an 8V can already be a handful on the road, we could argue that a top spec 8V will hardly be any less of a pain to keep below speed limits than a top spec 16V.
At the risk of shooting in my own foot, and as the finals costs between the two may hardly differ from between 5 to 10% on top of an arguably salty bill, I am not sure it's worth bothering with the lesser build, at least looking at such a build with a blank sheet of paper - it seems that many folks building 8V do so because they have progressively gathered parts over time and in some instance do not get to complete their project and come to sell components as they have realized along the way it's no small task, even with a pretended "plug & play" 8V.
Duke seems to be one of the few who got the opportunity to purchase an already-running, although not optimized, 3L 16V engine to begin his 16V journey, and he has understandably stuck to this configuration in spite of misfortunes that were not even related to the head being a 16V - Failures are integral part of the development process. Even the factory did not get its high HP engines right from the start. The 2.5 16V Le Mans engine covered the distance as they had decided to run it with less boost (1.1 bar) than intended (1.5 bar) in view of the major issues observed during the tests. But again, this head was quite different from the production castings of the S/S2/968 that have been proven reliable when turbocharged, if a few years down the line, and without any official input from the factory.
I agree with all said but the thing that I cant wrap my head around is that when an engine in an environment like porsche lemans team fails, there is a forensic examination of engine done by team of the best techs in business, especially in Porsche's golden years when they won everything tenfold.
They go trough every single detail and all relations of the most seemingly unrelated factors and after number of failed engines, they conclude what went wrong.
They definitely did that on 16V motors built for lemans and from there on, all big time racing engines were 8V.
Not meant to start an argue, I just see that as an interesting sequence of events.
I agree with all said but the thing that I cant wrap my head around is that when an engine in an environment like porsche lemans team fails, there is a forensic examination of engine done by team of the best techs in business, especially in Porsche's golden years when they won everything tenfold.
They go trough every single detail and all relations of the most seemingly unrelated factors and after number of failed engines, they conclude what went wrong.
They definitely did that on 16V motors built for lemans and from there on, all big time racing engines were 8V.
Not meant to start an argue, I just see that as an interesting sequence of events.
Porsche never did a street 16v turbo engine so it would make little sense to race one. Remember than the goal with the 944 Turbo S engine was 250 hp... 250! So adding the cost of a 16v head made no sense at all for their goals.
What type of rules the US made GTR was built for I don't know. It was likely a "production based" engine which required them to use the stock 944 turbo configuration of bore and stroke and head configuration.
That they used the 8v head makes as much (or little) sense as keeping the 2.5l displacement. If they were allowed by the rules and had funding you can bet that the engine would have looked differently in all aspects. Bore, stroke, head, valves, cams etc.
With racing it's always regulations so a racing car is basically never ever the best the factory can do if they were handed a blank piece of paper. The same goes for the 911 RSR's which are the highest level of factory race cars. The latest spec 991 RSR have a 460 hp N/A engine and that's because of rules. If it was up to Porsche you can bet they would put a 1000 hp turbo engine there
I agree with all said but the thing that I cant wrap my head around is that when an engine in an environment like porsche lemans team fails, there is a forensic examination of engine done by team of the best techs in business, especially in Porsche's golden years when they won everything tenfold.
FYI the front engined race program was a development program. The aim was to get the cars to finish Le Mans, keep winning it with 935 then with the 956 that came later. The front engined program was never the priority in endurance racing.
Originally Posted by Voith
They go trough every single detail and all relations of the most seemingly unrelated factors and after number of failed engines, they conclude what went wrong.
They definitely did that on 16V motors built for lemans and from there on, all big time racing engines were 8V.
They definitely did not. They tried the 16V 2.5 engine, it held the distance at Le Mans with fingers (and toes) crossed with less boost that they initially designed it for, ran it again once at the Norisring to promote the 944 that was coming on sale within the same time frame, then stopped their race program on the 924/944. Interestingly the same engine was used more or less successfully in Australia later on by a private team, but that was for sprint racing, not endurance racing. They still had significant issues that the factory never solved as it was not a priority for them.
Originally Posted by Voith
Not meant to start an argue, I just see that as an interesting sequence of events.
I appreciate your effort, but you keep missing a few key historical events to see the whole picture. Porsche never designed their 8V head to be used in competition. The factory had major issues that kept repeating themselves with the Audi engine in the 924 GTR, before they even designed the Porsche engine. They kept having issues that were repeating themselves, so it's not like they were in a 100% successful problem-solving process, contrary to what you may be thinking.
It was probably an opportunistic move from the factory to let people like Al Holbert and other motivated American teams to carry on with the front engined cars by themselves, securing promotion in the US where these cars were popular since the beginning, more so than in the domestic European market. It's always a matter of company politics and money, of course, and management cannot care less than the number of valves if the ROI is maximised.
While my experience with 3L 8V of different flavours, mine included, has shown me that an 8V can already be a handful on the road, we could argue that a top spec 8V will hardly be any less of a pain to keep below speed limits than a top spec 16V.
At the risk of shooting in my own foot, and as the finals costs between the two may hardly differ from between 5 to 10% on top of an arguably salty bill, I am not sure it's worth bothering with the lesser build, at least looking at such a build with a blank sheet of paper - it seems that many folks building 8V do so because they have progressively gathered parts over time and in some instance do not get to complete their project and come to sell components as they have realized along the way it's no small task, even with a pretended "plug & play" 8V.
Duke seems to be one of the few who got the opportunity to purchase an already-running, although not optimized, 3L 16V engine to begin his 16V journey, and he has understandably stuck to this configuration in spite of misfortunes that were not even related to the head being a 16V - Failures are integral part of the development process. Even the factory did not get its high HP engines right from the start. The 2.5 16V Le Mans engine covered the distance as they had decided to run it with less boost (1.1 bar) than intended (1.5 bar) in view of the major issues observed during the tests. But again, this head was quite different from the production castings of the S/S2/968 that have been proven reliable when turbocharged, if a few years down the line, and without any official input from the factory.
Thom I agree with you. Certainly an 8v can be made too fast for the street. While this is a broad generalisation, I know that when I had way less than you and others have, it was still a fast road car that was seldom beaten in a race. By race I don't mean a '300 mtr-3 honks-flat to the floor on a highway', but corners and braking etc. So I have no arguments over the validity of a solid 8v car. A blank sheet build can be scary expensive no matter how many valves. Plus of course there are degrees of project which will have a major effect on the bill$. I think we're sort of at the top of a wave and in the not too distant future a lot more people will be going with the 16v than in the past. The resources and parts have improved a lot in 10 years. Once more people do it, then it becomes more of the norm.
Originally Posted by Voith
I agree with all said but the thing that I cant wrap my head around is that when an engine in an environment like porsche lemans team fails, there is a forensic examination of engine done by team of the best techs in business, especially in Porsche's golden years when they won everything tenfold.
They go trough every single detail and all relations of the most seemingly unrelated factors and after number of failed engines, they conclude what went wrong.
They definitely did that on 16V motors built for lemans and from there on, all big time racing engines were 8V.
Not meant to start an argue, I just see that as an interesting sequence of events.
I don't know the detailed history of the 16v factory builds but I suspect that this wasn't the top of the list at Porsche. My guess is that it was a side project at best and they clearly didn't pour anywhere near the amount of time and money into the transaxles as they did the rear or mid engine race cars. If they had, we wouldn't be having this conversation now.
Originally Posted by Duke
Porsche never did a street 16v turbo engine so it would make little sense to race one. Remember than the goal with the 944 Turbo S engine was 250 hp... 250! So adding the cost of a 16v head made no sense at all for their goals.
What type of rules the US made GTR was built for I don't know. It was likely a "production based" engine which required them to use the stock 944 turbo configuration of bore and stroke and head configuration.
That they used the 8v head makes as much (or little) sense as keeping the 2.5l displacement. If they were allowed by the rules and had funding you can bet that the engine would have looked differently in all aspects. Bore, stroke, head, valves, cams etc.
With racing it's always regulations so a racing car is basically never ever the best the factory can do if they were handed a blank piece of paper. The same goes for the 911 RSR's which are the highest level of factory race cars. The latest spec 991 RSR have a 460 hp N/A engine and that's because of rules. If it was up to Porsche you can bet they would put a 1000 hp turbo engine there
FYI the front engined race program was a development program. The aim was to get the cars to finish Le Mans, keep winning it with 935 then with the 956 that came later. The front engined program was never the priority in endurance racing.
They definitely did not. They tried the 16V 2.5 engine, it held the distance at Le Mans with fingers (and toes) crossed with less boost that they initially designed it for, ran it again once at the Norisring to promote the 944 that was coming on sale within the same time frame, then stopped their race program on the 924/944. Interestingly the same engine was used more or less successfully in Australia later on by a private team, but that was for sprint racing, not endurance racing. They still had significant issues that the factory never solved as it was not a priority for them.
I appreciate your effort, but you keep missing a few key historical events to see the whole picture. Porsche never designed their 8V head to be used in competition. The factory had major issues that kept repeating themselves with the Audi engine in the 924 GTR, before they even designed the Porsche engine. They kept having issues that were repeating themselves, so it's not like they were in a 100% successful problem-solving process, contrary to what you may be thinking.
It was probably an opportunistic move from the factory to let people like Al Holbert and other motivated American teams to carry on with the front engined cars by themselves, securing promotion in the US where these cars were popular since the beginning, more so than in the domestic European market. It's always a matter of company politics and money, of course, and management cannot care less than the number of valves if the ROI is maximised.
It makes sense if the Race rules in US mandated 8v head as a 'production' type race car. However if that is not true, all that fabrication that must have cost a fortune was topped by 8v head even though it was a custom one.
Originally Posted by V2Rocket_aka944
didnt they find this made unbelievable power and was pretty reliable but the rules got changed so it couldnt compete anymore?
These type of engines did not live up because piston rings are not really rings and do not seal as they should on a flat sides of piston. Its a design flaw that makes me wonder how it was conceived in the first place.
It makes sense if the Race rules in US mandated 8v head as a 'production' type race car. However if that is not true, all that fabrication that must have cost a fortune was topped by 8v head even though it was a custom one.
Since no one on here is likely to ever proceed with a home-built 3L 8V using a 944 GTR head, it does not really matter. What matters is that the production 16V head as seen on the later cars, which is the topic here, is superior by all accounts to the factory 8V head.
Alternatively you can show us the way and design/build a "944 GTR" look-alike 8V head yourself. That would be some kind of topic worth blabbering about on here. They may sell like hotcakes. In fact I would probably even order you one
What matters is that the production 16V head as seen on the later cars, which is the topic here, is superior by all accounts to the factory 8V head.
I don't agree with that.
16V has larger 800°C+ combustion chamber surface and that is not better as surfaces that hot are more prone to self detonation if all else is being equal.
16v head is less reliable than 8V since it contains critical maintenance part, namely the plastic chain tensioner, so it can never be as reliable as 8V since less complication = more reliability.
Structural integrity of 8V head is stronger than 16V by a long shot. I have seen cracked 944S 16V head and I have never ever seen an 8V 944/951 head crack. Factory even put out a bulletin for testing cracked 16V heads.
Take a sledge hammer and try to knock out 2V combustion chamber and then 4V.
It flows better by a relatively large margin and has nicer shaped combustion chamber, but the benefits end there. Maybe it is better in steam management, but that is again just a guess.
How many cracked 4V heads have you seen with your own eyes Thom?
03-25-2015, 05:20 AM
It's intoxicating pushing the right foot on the floor (I'm just a week of driving with my 924 2.5 16v turbo, hence the exhilaration) but traffic slows down quite good and having driven quite a few times in Holland, I have a feeling that you will get some traffic too 
