Piston Bowls
- Thread starter Fingers
- Start date
I was wondering who was going to notice that, and you are the winner Matt!!! Nice to see you again, it's been too long!
It is kinda ironic how some will fight until the end saying elevation has little to do with how these motors run. its nice to see someone that is in agreement with me finally. My motors have been at 15/1, 16/1, and now 16.5/1 and each motor has been more fun to drive, less smoke and more responsive.
I will definitely agree with you guys about the elevation playing hell with driveability but I don't see that here in Indiana. If I was in your shoes I would keep it up there around stock levels.
Matt, that article is wht got me started on the whole compression kick a year ago when it debuted. I figured if it works for them then we need to figure it out. Doing the same thing over and over agian expecting a different result is the definition of insanity, just saying.
He is, but he only signed up a few weeks ago because I told him about a set of twins that were for sale in the classified section here.
Hopefully he'll post his findings . There seems to be quite a few engines running these pistons WAY :cool2:
Installed another set of these race cast oval's in a motor today at 15.5:1 with .075" reliefs. Will be a 700+Hp 2.5 VGT street truck that sled pulls in 2.5 class.
Have ran stock cam, 3388 SoCal, 6480 SoCal(what is in mine), and will be doing a 9100 SoCal combo very soon. The 3388 works great but my motor with the 6480 is just plain loud! This cam in a normal mahle forged 16.5:1 was not one of my favorites, kinda lazy feeling without alot of rpm gain. I had this cam on the shelf used because we replaced it with a 9100 in a 2.6 puller to gain more topend power. In my motor it acts completely diferent, with great response and definitely wants to rev hard and the thump out the pipe is rediculous, it is so loud. I think this cam will rock with the twins when I put an 88mm over my 72mm vgt. It's all about the combination and the compression ratio with this piston design acts completely different than the normal mahle round chamber and I think this is why my experience is so different than the masses, idk.
I was thinking about 16 to 1? An mark I'll have to be talking to you in private here soon I'm really tossing around the idea of adding another turbo to accompany my 71mm and having you tune my motor with these pistons I'm in the north eastern part of Indiana so I'm not too far out of range
Fingers, great info in here, thanks! I had been curious about increasing engine efficiency (I know I'm one of the few who wants high MPG more than I want higher HP) but it sounds like you are saying that you achieve diminishing returns as CR moves much above stock LLY levels. I'm sub'd to see how those 18:1 pistons work out too. I can certainly see why lowering CR is conducive to increasing boost pressure as Mark outlined and how that plays into daily driver usage as well.
Again thank you both for your insight. :thumb:
Remember, the ultimate efficiency of the diesel is based on the "Ideal" engine. Reality gets in the way.
There are many reasons besides blowby that reduce the efficiency as you increase CR.
High on the list is heat transfer. At higher CRs the chamber temps are significantly higher than lower CRs. Since the transfer of heat from the charge to the piston and block and head is driven by the temperature difference between the two, you lose more heat energy to the engine at higher CRs. A lot more. Heat energy is, after all, where all the power is.
There are many reasons besides blowby that reduce the efficiency as you increase CR.
High on the list is heat transfer. At higher CRs the chamber temps are significantly higher than lower CRs. Since the transfer of heat from the charge to the piston and block and head is driven by the temperature difference between the two, you lose more heat energy to the engine at higher CRs. A lot more. Heat energy is, after all, where all the power is.
How much of a gain did you observe switching from the 8460 to the 9100? Did it make more hp or just move it up in the rpm range?