Combustion chamber and piston dish shape
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From: All humans are vermin in the eyes of Guru VA
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Combustion chamber and piston dish shape
OK so I am building a forced induction motor, and since I am po' I tend to agonize over every little thing.
So as far as I can tell chamber development lead to the kidney/heart shaped chamber for increased power, economy, less detonation, and increased compression reliably. So what about the piston on the other side. I would assume that it would have as much to do with the flame fronts and whatever as the chamber does.
So my options are
1.) Cheap - D-shaped cup
2.) Not so cheap - symetrical reliefs
3.) Expensive - Asymetrical relief(like my chamber bigger relief for the bigger valve.
So as far as I can tell chamber development lead to the kidney/heart shaped chamber for increased power, economy, less detonation, and increased compression reliably. So what about the piston on the other side. I would assume that it would have as much to do with the flame fronts and whatever as the chamber does.
So my options are
1.) Cheap - D-shaped cup
2.) Not so cheap - symetrical reliefs
3.) Expensive - Asymetrical relief(like my chamber bigger relief for the bigger valve.
Team Owner
Joined: Jul 1999
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From: Orange Park Florida
Guru, from a tech aspect I can say I dunno crap, from a bux side ....
you pursue this project you most definately will continue to be 'po' but.......
it will put a hell of a smile on your face....
GENE
you pursue this project you most definately will continue to be 'po' but.......
it will put a hell of a smile on your face....
GENE
Le Mans Master
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From: Fremont CA
Any of the 3 options are OK if you are retaining proper quench clearance rather than putting the pistons down into the bore (0.040" piston top to cylinder head clearance.) #3 is the best solution but, any of the 3 methods will work better than a full "bowl type" dish on the piston top. Make sure the rings are 0.250-0.300" down too and go with 0.927X2.75 or 3.00" long piston pins NONE! of the 2.50-2.25" long normally aspirated "race" stuff if your going to put some boost in the motor.
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From: All humans are vermin in the eyes of Guru VA
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Yeah I think I have been underplaying it. I think a solid roller cam to replace the hydraulic one, and move the redline up to 6800rpm or so with shift points around 6300 would do me a lot of good.
I wouldnt need to change anything except my cam really.
But all I want is 650hp.
I wouldnt need to change anything except my cam really.
But all I want is 650hp.
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From: All humans are vermin in the eyes of Guru VA
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I was looking at the sealed-power/TRW piston (summit part number)
TRW-L2441F30
The SRP piston
SRP-139632
the JE piston(asymetrical)
JEP-130969-8
If the D-shaped cup will work than I just might buy the speed-pros. If there isnt 200-300 dollar improvement to the other shaped dish.
TRW-L2441F30
The SRP piston
SRP-139632
the JE piston(asymetrical)
JEP-130969-8
If the D-shaped cup will work than I just might buy the speed-pros. If there isnt 200-300 dollar improvement to the other shaped dish.
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From: All humans are vermin in the eyes of Guru VA
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I guess I am just gonna have to spring for the JE pistons. Damn I really didnt want too but I cant find an alternative that has an asymetrical dish designed to mimic the fastburn chamber, and maintain quench.
The turbo guys on the turbo forum are disturbingly silent. Do I ask hard questions or something?
The turbo guys on the turbo forum are disturbingly silent. Do I ask hard questions or something?
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From: All humans are vermin in the eyes of Guru VA
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Originally Posted by Solid LT1
Any of the 3 options are OK if you are retaining proper quench clearance rather than putting the pistons down into the bore (0.040" piston top to cylinder head clearance.) #3 is the best solution but, any of the 3 methods will work better than a full "bowl type" dish on the piston top. Make sure the rings are 0.250-0.300" down too and go with 0.927X2.75 or 3.00" long piston pins NONE! of the 2.50-2.25" long normally aspirated "race" stuff if your going to put some boost in the motor.
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From: All humans are vermin in the eyes of Guru VA
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I am assuming that the standard deck height is 9.025
Wow
So a 3.48" stroke + 5.7" rod and a 1.56 compression height only gets me 9" so my pistons will be .025 down in the hole to start with. add a .041 standard head gasket and I am at an unacceptable .066 quench. so I need to lose about half that distance somewhere.
I can get a .027 thick Cometic MLS head gasket that takes me down to .052
I suppose if I decked the block to 9.010 I could get .37 quench which will wonderfully.
Dang.
Wow
So a 3.48" stroke + 5.7" rod and a 1.56 compression height only gets me 9" so my pistons will be .025 down in the hole to start with. add a .041 standard head gasket and I am at an unacceptable .066 quench. so I need to lose about half that distance somewhere.
I can get a .027 thick Cometic MLS head gasket that takes me down to .052
I suppose if I decked the block to 9.010 I could get .37 quench which will wonderfully.
Dang.
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From: Park Ridge IL
Here's what my piston from my 1200hp TT SBC427 looked like.
I already had the Dart CNC 18* heads from the engine's previous incarnation as a 12:1 compression NA engine, and I wasn't about to take the grinder to the CNC machined combustion chamber to enlarge them or go with a piston with a too short compression height - not good for combustion efficiency and not good for forced induction apps due to the ring location. 1.175" compression height works perfectly fine and you can safely locate your rings (as mentioned in an earlier post) although the oil ring will need a support but that's no big deal.. Besides, I beleive in the small, efficient combustion chamber to promote flame travel and uniform A/F ratio. In order to drop the compression from 12:1 to 8.5:1 I had to go with a fully dished custom piston from JE. There are some benefits to this design in that the cylinder pressure is applied more uniformly against the piston and the valves are greatly unshrouded, but you do give up some traditional quech area although you still ahve some around the circumeference of the chamber. Even so, you'll notice I still had to have a slight valve relief for the intake valve as I was running a 2.180" valve.
I already had the Dart CNC 18* heads from the engine's previous incarnation as a 12:1 compression NA engine, and I wasn't about to take the grinder to the CNC machined combustion chamber to enlarge them or go with a piston with a too short compression height - not good for combustion efficiency and not good for forced induction apps due to the ring location. 1.175" compression height works perfectly fine and you can safely locate your rings (as mentioned in an earlier post) although the oil ring will need a support but that's no big deal.. Besides, I beleive in the small, efficient combustion chamber to promote flame travel and uniform A/F ratio. In order to drop the compression from 12:1 to 8.5:1 I had to go with a fully dished custom piston from JE. There are some benefits to this design in that the cylinder pressure is applied more uniformly against the piston and the valves are greatly unshrouded, but you do give up some traditional quech area although you still ahve some around the circumeference of the chamber. Even so, you'll notice I still had to have a slight valve relief for the intake valve as I was running a 2.180" valve.
Last edited by Monty; Jan 20, 2006 at 06:36 PM.
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So the circular dish is OK. Thats good to know.
Thanks.
Probe makes a forged piston similiar to that for 329 bucks for a set of 8. Its not a JE but I am also not planning on running as much boost as you.
As a question monty how much did the CV products pully system run you?
Thanks.
Probe makes a forged piston similiar to that for 329 bucks for a set of 8. Its not a JE but I am also not planning on running as much boost as you.
As a question monty how much did the CV products pully system run you?
Last edited by Guru_4_hire; Jan 20, 2006 at 09:35 PM.
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From: Fremont CA
Full dish pistons like the ones in the photo leave some of the mixture unburn but, do help with piston cooling in a supercharged motor (or turbocharged engine.) The mixture uniformity and burning are much better with a "D" or assymetrical dish type piston. You can use anything you want but, I would go with the J&E pistons in my motor.
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From: All humans are vermin in the eyes of Guru VA
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The thing is I am trying to avoid 700 dollar pistons. 400-500 is much more condusive to my life.
Is there somebody that sells slugs to be machined?
Is there somebody that sells slugs to be machined?
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From: All humans are vermin in the eyes of Guru VA
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Originally Posted by Solid LT1
Full dish pistons like the ones in the photo leave some of the mixture unburn but, do help with piston cooling in a supercharged motor (or turbocharged engine.) The mixture uniformity and burning are much better with a "D" or assymetrical dish type piston. You can use anything you want but, I would go with the J&E pistons in my motor.
But the full dish will keep the piston cooler avoiding hot spots.
Interesting.
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From: Park Ridge IL
Originally Posted by Guru_4_hire
As a question monty how much did the CV products pully system run you?
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From: All humans are vermin in the eyes of Guru VA
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Good deal. I am sort doing my turbo project on a budget. So I agonize over everything, and then compromise my agonization with what I can actually afford.
I did come up with a new top-shelf fluidampr off of ebay for a song. So I am happy there.
I did come up with a new top-shelf fluidampr off of ebay for a song. So I am happy there.
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From: All humans are vermin in the eyes of Guru VA
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I can get wiseco pistons for 8.7 or so compression with rings and pins for 514 bucks. they have symetrical reliefs but I guess it will have to do. I will just save up some more money and have them ceramic coated by swaintech. that will help keep them cool.
also I think there is a TRW piston I could get but after I add in rings its already at the wiseco price.
also I think there is a TRW piston I could get but after I add in rings its already at the wiseco price.
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From: pr, frederick md.
Originally Posted by Guru_4_hire
Yeah I think I have been underplaying it. I think a solid roller cam to replace the hydraulic one, and move the redline up to 6800rpm or so with shift points around 6300 would do me a lot of good.
I wouldnt need to change anything except my cam really.
But all I want is 650hp.
I wouldnt need to change anything except my cam really.
But all I want is 650hp.
