Refresh951's Hybrid Ultra Stroker Build
04-08-2014 | 07:23 PM
#1411
Race Car
Joined: Apr 2009
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From: Knoxville, TN
Those reasons are usually related to a rulebook. But it could also be related to simplicity, service, and durability. But, a 4V chamber is superior in just about every facet to a 2V chamber. Even ignoring flow, the plug is in the center of hte chamber, which lets you run 3/4 of a point more compression, which gives you better fuel, and allows MBT with less advance. My preference for a 4V has every bit as much to do with plug location as flow (maybe because I have a lot of chemistry in my background).
04-08-2014 | 07:57 PM
#1413
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From: Marietta, Georgia
I have absolutely no problem with any of your comments and I highly value your input. I just meant a critical look at results which I view as a very positive thing. It is easy to get wrapped up in a project and to become non-objective. Thanks for taking the time to give some input here. 
04-08-2014 | 09:25 PM
#1414
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Joined: Feb 2006
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From: Australia
I’m doubtful of the 700bhp figure? Would like to see any evidence of that.
Interestingly re the 2v vs 4v discussion, in the Aussie V8s we always used American based V8’s (ie 2v pushrod motors) however since there has been the introduction of other marques such as Mercs, Nissans and now Volvos, we have some 4v V8s running around. Rumour has it that the Nissans were complaining that they were losing some power compared to the 2v motors due to parasitic loss of the extra drivetrain associated. Just thought that was interesting.
Note, these are n/a motors of course. Perhaps this isn’t as much of an issue with forced induction.
Interestingly re the 2v vs 4v discussion, in the Aussie V8s we always used American based V8’s (ie 2v pushrod motors) however since there has been the introduction of other marques such as Mercs, Nissans and now Volvos, we have some 4v V8s running around. Rumour has it that the Nissans were complaining that they were losing some power compared to the 2v motors due to parasitic loss of the extra drivetrain associated. Just thought that was interesting.
Note, these are n/a motors of course. Perhaps this isn’t as much of an issue with forced induction.
04-08-2014 | 09:39 PM
#1415
Rainman
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From: Nashville, TN
I’m doubtful of the 700bhp figure? Would like to see any evidence of that.
Interestingly re the 2v vs 4v discussion, in the Aussie V8s we always used American based V8’s (ie 2v pushrod motors) however since there has been the introduction of other marques such as Mercs, Nissans and now Volvos, we have some 4v V8s running around. Rumour has it that the Nissans were complaining that they were losing some power compared to the 2v motors due to parasitic loss of the extra drivetrain associated. Just thought that was interesting.
Note, these are n/a motors of course. Perhaps this isn’t as much of an issue with forced induction.
Interestingly re the 2v vs 4v discussion, in the Aussie V8s we always used American based V8’s (ie 2v pushrod motors) however since there has been the introduction of other marques such as Mercs, Nissans and now Volvos, we have some 4v V8s running around. Rumour has it that the Nissans were complaining that they were losing some power compared to the 2v motors due to parasitic loss of the extra drivetrain associated. Just thought that was interesting.
Note, these are n/a motors of course. Perhaps this isn’t as much of an issue with forced induction.
2v pushrod is still plenty capable, NASCAR 5.9L v8s make ~8-900hp and do 9000RPM and have only been EFI for a few years now...
anyways,
shawn,
at any point would you consider switching to an NA head vs the turbo, for added exhaust flow ability too? or just go 16v at that point?
04-08-2014 | 09:52 PM
#1416
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From: Marietta, Georgia
04-08-2014 | 11:06 PM
#1417
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Joined: Dec 2011
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Im not convinced..
924 GTR with 944 lemans 16V head was concieved in 1980, yet in 87 us GTR race car used 8 valve head and they even made custom cast 8V head. Money was clearly no object and 944S 16 valvers rolled off the assembly lines, yet top builders chose 8 valves for high profile 944 engines.. Why? There has to be a reason that is not money related. Those cars are not budget builds and made close to 700hp on 2,5 liter engines with 8V head..
Whats the point? Development cost of that GTR 8V head was not much less than if they'd developed 20V head. But they didn't.
I know a guy that was a factory mechanic and engine builder on 959 paris dakar and 944 german cup series, and he advised against 2.7 and 16V head on my 3.0 build (if want to boost over 1BAR). He said that the best option is ported & modified 951 head(with ceramic ex. liners). He has over 1500 porsche official race engine builds under his belt.
7 second 514whp pull and 500+hp 24H endurance race are two different things. Maybe that was the reason for 8V.
924 GTR with 944 lemans 16V head was concieved in 1980, yet in 87 us GTR race car used 8 valve head and they even made custom cast 8V head. Money was clearly no object and 944S 16 valvers rolled off the assembly lines, yet top builders chose 8 valves for high profile 944 engines.. Why? There has to be a reason that is not money related. Those cars are not budget builds and made close to 700hp on 2,5 liter engines with 8V head..
Whats the point? Development cost of that GTR 8V head was not much less than if they'd developed 20V head. But they didn't.
I know a guy that was a factory mechanic and engine builder on 959 paris dakar and 944 german cup series, and he advised against 2.7 and 16V head on my 3.0 build (if want to boost over 1BAR). He said that the best option is ported & modified 951 head(with ceramic ex. liners). He has over 1500 porsche official race engine builds under his belt.
7 second 514whp pull and 500+hp 24H endurance race are two different things. Maybe that was the reason for 8V.
04-08-2014 | 11:45 PM
#1418
Rainman
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From: Nashville, TN
maybe they were RPM/speed limited so the 16v didnt make too much sense...or tight tracks needing more oomph off corners...
or maybe they knew something about the 944S cam chain drive that might not make 24 hours of hard labor.
or maybe they knew something about the 944S cam chain drive that might not make 24 hours of hard labor.
04-09-2014 | 04:13 AM
#1419
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Joined: Feb 2006
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From: Australia
what kind of displacement do aussies run?
2v pushrod is still plenty capable, NASCAR 5.9L v8s make ~8-900hp and do 9000RPM and have only been EFI for a few years now...
anyways,
shawn,
at any point would you consider switching to an NA head vs the turbo, for added exhaust flow ability too? or just go 16v at that point?
2v pushrod is still plenty capable, NASCAR 5.9L v8s make ~8-900hp and do 9000RPM and have only been EFI for a few years now...
anyways,
shawn,
at any point would you consider switching to an NA head vs the turbo, for added exhaust flow ability too? or just go 16v at that point?
04-09-2014 | 04:34 AM
#1420
Addict
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From: Slovenia
I dont find that picture though..
04-09-2014 | 05:28 AM
#1421
Nordschleife Master
Joined: Aug 2001
Posts: 5,552
Likes: 18
From: Stockholm, Sweden
It's like comparing F1 engines. In 1986 the BMW M12/13 1.5 liter engine made 1300 hp in qualification trim. It doesn't mean it is a better engine compared to the 1.6 liter 600 hp combustion engines in F1 today. Apples to oranges.
04-09-2014 | 05:53 AM
#1422
Race Car
Joined: Mar 2002
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Duke, I'm saying that drawing conclusions from these dyno sheets makes little point considering the engine has not been retuned to suit the new intake. Your observations are correct, but you can't compare apples with oranges even if the Maths let you do so
I'm really interested in Shawn's progress as he is the only guy I know of who has now first hand experience with swapping intakes on the same 951 engine, all other things being equal, and considering costs as a limiting factor I'm sure he is on the way to making big progress now that a significant bottleneck from the stock hardware has been removed. I would probably also have jumped straight from a 2.5 8V to a 3.0 16V if things had turned up differently for me, but I doubt I would have learned as many relevant aspects without swapping components one by one. I suppose it depends how much you ponder the acquisition of knowledge in your personal ROI.
I'm really interested in Shawn's progress as he is the only guy I know of who has now first hand experience with swapping intakes on the same 951 engine, all other things being equal, and considering costs as a limiting factor I'm sure he is on the way to making big progress now that a significant bottleneck from the stock hardware has been removed. I would probably also have jumped straight from a 2.5 8V to a 3.0 16V if things had turned up differently for me, but I doubt I would have learned as many relevant aspects without swapping components one by one. I suppose it depends how much you ponder the acquisition of knowledge in your personal ROI.
04-09-2014 | 06:19 AM
#1424
Nordschleife Master
Joined: Aug 2001
Posts: 5,552
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From: Stockholm, Sweden
Duke, I'm saying that drawing conclusions from these dyno sheets makes little point considering the engine has not been retuned to suit the new intake. Your observations are correct, but you can't compare apples with oranges even if the Maths let you do so
I'm really interested in Shawn's progress as he is the only guy I know of who has now first hand experience with swapping intakes on the same 951 engine, all other things being equal, and considering costs as a limiting factor I'm sure he is on the way to making big progress now that a significant bottleneck from the stock hardware has been removed. I would probably also have jumped straight from a 2.5 8V to a 3.0 16V if things had turned up differently for me, but I doubt I would have learned as many relevant aspects without swapping components one by one. I suppose it depends how much you ponder the acquisition of knowledge in your personal ROI.
I'm really interested in Shawn's progress as he is the only guy I know of who has now first hand experience with swapping intakes on the same 951 engine, all other things being equal, and considering costs as a limiting factor I'm sure he is on the way to making big progress now that a significant bottleneck from the stock hardware has been removed. I would probably also have jumped straight from a 2.5 8V to a 3.0 16V if things had turned up differently for me, but I doubt I would have learned as many relevant aspects without swapping components one by one. I suppose it depends how much you ponder the acquisition of knowledge in your personal ROI.
I think all of us have gone done the slippery slope of starting with small mods only to end up in big projects years later. Great for learning, not so great for finances though
04-09-2014 | 06:32 AM
#1425
Nordschleife Master
Joined: Aug 2001
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From: Stockholm, Sweden