16v vs 8v head turbo application - max static compression ?
01-29-2011, 09:05 AM
#151
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Ok I had to let that sit for a little while – I am not sure how Duke and I got to pissing in each other’s Wheaties…but it not a good thing!
Duke – I respect what you are doing and obviously you are doing something right simply based on the dyno charts! Your dyno charts are much better that most of the other 16v projects from the past – earlier torque and a flatter and wider plateau. So if it sounded like I was saying you were doing something ‘wrong’ that was not how I meant it to appear.
I made up the twin cam drive for several reasons – mainly it was as an R&D tool to figure out the best possible cam timing. Traditionally cams for a higher rpm NA motor do not work well for a turbo motor and all the past 16v projects has fairly poor low end performance. I wanted to see if it was possible to really get the torque up in the low end. Once the optimum timing for a particular application was found then custom cams could be made based on that info and used is a stock type set up (even in a variocam set up!).
Along the way to putting all this together I was looking for 16v heads (I have about 20 of them on the shelf right now) and I found quite a few that had the chain tensioner mount stripped out of the head from failure as well as quite a few cams with stripped teeth. That made me question the wisdom of a plastic block rubbing on a chain…..it works if maintained, but the engineering side of me still says ‘yuck’.
In the end I will make up cams to fit the stock type 16v drive for most projects but I will keep the twin cam for race/track set ups. The ability to tune your torque curve for each track is a plus and I sleep better without visions of a steel chain rubbing on plastic! BTW – you are correct in that two exhaust cams are not ‘optimal’, they are just a step in the process. To modify a common quote – “its not over until the fat torque lady sings’!
One last thing…and this is just a technical questions to the ‘man’ when it comes to playing with the variocam -
If I read that right is says there is a significant difference in the mid-range but not much in the top end – why not just leave it in the position where you found the mid-range gains?
Besides all that technical stuff my cam gears come in colors….they are pretty and the spin around and around. Maybe I should include a little LED light behind the spokes?
Duke – you are better than ‘just OK’ in my book.
Duke – I respect what you are doing and obviously you are doing something right simply based on the dyno charts! Your dyno charts are much better that most of the other 16v projects from the past – earlier torque and a flatter and wider plateau. So if it sounded like I was saying you were doing something ‘wrong’ that was not how I meant it to appear.
I made up the twin cam drive for several reasons – mainly it was as an R&D tool to figure out the best possible cam timing. Traditionally cams for a higher rpm NA motor do not work well for a turbo motor and all the past 16v projects has fairly poor low end performance. I wanted to see if it was possible to really get the torque up in the low end. Once the optimum timing for a particular application was found then custom cams could be made based on that info and used is a stock type set up (even in a variocam set up!).
Along the way to putting all this together I was looking for 16v heads (I have about 20 of them on the shelf right now) and I found quite a few that had the chain tensioner mount stripped out of the head from failure as well as quite a few cams with stripped teeth. That made me question the wisdom of a plastic block rubbing on a chain…..it works if maintained, but the engineering side of me still says ‘yuck’.
In the end I will make up cams to fit the stock type 16v drive for most projects but I will keep the twin cam for race/track set ups. The ability to tune your torque curve for each track is a plus and I sleep better without visions of a steel chain rubbing on plastic! BTW – you are correct in that two exhaust cams are not ‘optimal’, they are just a step in the process. To modify a common quote – “its not over until the fat torque lady sings’!
One last thing…and this is just a technical questions to the ‘man’ when it comes to playing with the variocam -
This is an easy target 
I am extremely confident there is a lot to gain for my setup so I'm totally with you. BUT, the effect I got from VarioCam can not be replaced directly with a static cam setup. I gained a lot in the midrange, while in another part of the curve (top end max HP) there was no difference with or without Variocam activated. So with a static setup I would have a compromise: more top end - less midrange, more midrange - less top end.
I am extremely confident there is a lot to gain for my setup so I'm totally with you. BUT, the effect I got from VarioCam can not be replaced directly with a static cam setup. I gained a lot in the midrange, while in another part of the curve (top end max HP) there was no difference with or without Variocam activated. So with a static setup I would have a compromise: more top end - less midrange, more midrange - less top end.Besides all that technical stuff my cam gears come in colors….they are pretty and the spin around and around. Maybe I should include a little LED light behind the spokes?
Duke – you are better than ‘just OK’ in my book.
01-30-2011, 02:01 AM
#152
Formula One Spin Doctor
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I don't think you guys really know Stockholm Duke , he originally learned how to tune his cams while filming, the gains are real , he needs the power, listen to his custom BV.
http://www.youtube.com/watch?v=fzjAe...eature=related
http://www.youtube.com/watch?v=fzjAe...eature=related
01-30-2011, 10:08 AM
#154
Nordschleife Master
Ok I had to let that sit for a little while – I am not sure how Duke and I got to pissing in each other’s Wheaties…but it not a good thing!
Duke – I respect what you are doing and obviously you are doing something right simply based on the dyno charts! Your dyno charts are much better that most of the other 16v projects from the past – earlier torque and a flatter and wider plateau. So if it sounded like I was saying you were doing something ‘wrong’ that was not how I meant it to appear.
I made up the twin cam drive for several reasons – mainly it was as an R&D tool to figure out the best possible cam timing. Traditionally cams for a higher rpm NA motor do not work well for a turbo motor and all the past 16v projects has fairly poor low end performance. I wanted to see if it was possible to really get the torque up in the low end. Once the optimum timing for a particular application was found then custom cams could be made based on that info and used is a stock type set up (even in a variocam set up!).
Along the way to putting all this together I was looking for 16v heads (I have about 20 of them on the shelf right now) and I found quite a few that had the chain tensioner mount stripped out of the head from failure as well as quite a few cams with stripped teeth. That made me question the wisdom of a plastic block rubbing on a chain…..it works if maintained, but the engineering side of me still says ‘yuck’.
In the end I will make up cams to fit the stock type 16v drive for most projects but I will keep the twin cam for race/track set ups. The ability to tune your torque curve for each track is a plus and I sleep better without visions of a steel chain rubbing on plastic! BTW – you are correct in that two exhaust cams are not ‘optimal’, they are just a step in the process. To modify a common quote – “its not over until the fat torque lady sings’!
One last thing…and this is just a technical questions to the ‘man’ when it comes to playing with the variocam -
If I read that right is says there is a significant difference in the mid-range but not much in the top end – why not just leave it in the position where you found the mid-range gains?
Besides all that technical stuff my cam gears come in colors….they are pretty and the spin around and around. Maybe I should include a little LED light behind the spokes?
Duke – you are better than ‘just OK’ in my book.
Duke – I respect what you are doing and obviously you are doing something right simply based on the dyno charts! Your dyno charts are much better that most of the other 16v projects from the past – earlier torque and a flatter and wider plateau. So if it sounded like I was saying you were doing something ‘wrong’ that was not how I meant it to appear.
I made up the twin cam drive for several reasons – mainly it was as an R&D tool to figure out the best possible cam timing. Traditionally cams for a higher rpm NA motor do not work well for a turbo motor and all the past 16v projects has fairly poor low end performance. I wanted to see if it was possible to really get the torque up in the low end. Once the optimum timing for a particular application was found then custom cams could be made based on that info and used is a stock type set up (even in a variocam set up!).
Along the way to putting all this together I was looking for 16v heads (I have about 20 of them on the shelf right now) and I found quite a few that had the chain tensioner mount stripped out of the head from failure as well as quite a few cams with stripped teeth. That made me question the wisdom of a plastic block rubbing on a chain…..it works if maintained, but the engineering side of me still says ‘yuck’.
In the end I will make up cams to fit the stock type 16v drive for most projects but I will keep the twin cam for race/track set ups. The ability to tune your torque curve for each track is a plus and I sleep better without visions of a steel chain rubbing on plastic! BTW – you are correct in that two exhaust cams are not ‘optimal’, they are just a step in the process. To modify a common quote – “its not over until the fat torque lady sings’!
One last thing…and this is just a technical questions to the ‘man’ when it comes to playing with the variocam -
If I read that right is says there is a significant difference in the mid-range but not much in the top end – why not just leave it in the position where you found the mid-range gains?
Besides all that technical stuff my cam gears come in colors….they are pretty and the spin around and around. Maybe I should include a little LED light behind the spokes?
Duke – you are better than ‘just OK’ in my book.
While the genereal theory of overlap and N/A cams not being good for a turbo engine is right, it does not necessarliy make it a bad choice depending on the engine. With a low backpressure turbo and moderate boost levels overlap can be beneficial. Something that is proven by my engine. And I'm all about results. That's why I was so surprised about the OK comment
My point is that stock 968 cams along with Variocam might be one of the best setups for a GT3582R type of turbo and moderate boost. But I do like adjustability so a set of dual cam gears would be nice (and cool of course). If someone would take the time to do back to back dyno of different cam setups I'd be more than happy to put the best setup on my purchase list if it would turn out I have power to find!
My engine will be dry sumped and get 4-1 headers with large diam primary and a very nice long merge collector with low convergence angle so upper end power should go up a fair bit. Add a pair of long duration cams and I'm confident 600 rwhp could be passed at low boost
Yes that is basically what I did regarding my VarioCam-settings. I have it activiated where it gains torque and deactiviated where it reduces torque.
01-30-2011, 10:13 AM
#155
Nordschleife Master
Choosing a modded 951 for race from the cops would be the worst thing you could do. They'll cuff you while you're trying to fix the car by the side of the road
01-30-2011, 10:18 PM
#157
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Has any body tried different combinations with the 2.5 S cams or combo of 2.5 and 3.0 . If memories serves correctly the 2.5 is basically same lift duration with different opening and closing times.
