The ultimate strength of the stock piston is more than the delipped. However, the reduction in compression ratio, and thus the max pressure and temp, more than makes up for the reduction in strength.
Piston Bowls
- Thread starter Fingers
- Start date
This is what I said in another thread. I couldn't agree more.
Have you made any revisions or is what I have current? I believe I'm going to start my build.
I'm finally off the road and nearly have my house in order to continue the project. I ended up being out of town a bit longer than expected.
I have purchased CAMWorks which works within SolidWorks for Machine code. I have spent the last few days working with the post-processor to generate code in a style that "I" like. So far, the machines like the code too. I will play with a scrap piece of aluminum tonight and see how it goes.
I have made one revision to the original design. I have increased the radius around the bowl from 0.062" to 0.125"
If there is interest, I will make a copy of the piston model available on-line. The valve reliefs are only 0.040" for my application. I know that some other people have/need significantly more. If you need a larger relief, let me know and I can easily adjust the model.
I have purchased CAMWorks which works within SolidWorks for Machine code. I have spent the last few days working with the post-processor to generate code in a style that "I" like. So far, the machines like the code too. I will play with a scrap piece of aluminum tonight and see how it goes.
I have made one revision to the original design. I have increased the radius around the bowl from 0.062" to 0.125"
If there is interest, I will make a copy of the piston model available on-line. The valve reliefs are only 0.040" for my application. I know that some other people have/need significantly more. If you need a larger relief, let me know and I can easily adjust the model.
The radii I changed increased the measured volume of the piston chamber too much. (for me) I should have checked it in Solidworks first. The Measured and SolidWorks calculated amounts were identical.
I made the needed changes to the model, checked the chamber volume and then re-ran the FEA on the piston. All good now.
I hope to machine another blank (non-piston) tonight.
I made the needed changes to the model, checked the chamber volume and then re-ran the FEA on the piston. All good now.
I hope to machine another blank (non-piston) tonight.
:thumb: Keep it up! I haven't decided on pistons for my motor that I plan to build this year sometime and I think there is a ton of merit to this idea!
Brief update.
Discovered a flaw in the profile. A bump where it shouldn't be. Chased that to ground and redid a couple hunks of stock to test. Looked good.
Cut all the pistons. I still need to rub them down to remove the machine marks, but all is good. The CNCs I borrow to do the machining have been tied up most nights, so I have had to wait my turn.
Now to put the short block together...
Discovered a flaw in the profile. A bump where it shouldn't be. Chased that to ground and redid a couple hunks of stock to test. Looked good.
Cut all the pistons. I still need to rub them down to remove the machine marks, but all is good. The CNCs I borrow to do the machining have been tied up most nights, so I have had to wait my turn.
Now to put the short block together...
can't wait to see how it all works out
I've cracked a stock unmodified LBZ piston, I cracked a stock unmodified LB7 piston and I cracked a delipped uncoated LB7 piston. I'm going with with forged pistons on my current build, but I'm keeping my eye on the oval bowl design Fingers is working on.
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Waiting on the machine shop to balance the rotating assembly.....
I am always amazed when I start matching up pieces the variation in weights of the pistons. At least from Mahle. I have 10 pistons and they vary over 4 grams from lightest to heaviest. BUT 8 are within a gram of each other. I don't know for sure, but it would indicate that there is something wrong with the extra light pistons.
FWIW, I weight match all my components. Pistons within a gram range, wrist pins the same, rods too. I check the rod for big and little end variations. Then juggle the sub assemblies to stay within ~1/2 a gram. All piston/pin assemblies are with 1/2 gram. Same with the completed reciprocating piece.
Why? Just anal I guess.
I am always amazed when I start matching up pieces the variation in weights of the pistons. At least from Mahle. I have 10 pistons and they vary over 4 grams from lightest to heaviest. BUT 8 are within a gram of each other. I don't know for sure, but it would indicate that there is something wrong with the extra light pistons.
FWIW, I weight match all my components. Pistons within a gram range, wrist pins the same, rods too. I check the rod for big and little end variations. Then juggle the sub assemblies to stay within ~1/2 a gram. All piston/pin assemblies are with 1/2 gram. Same with the completed reciprocating piece.
Why? Just anal I guess.
Recap:
These pistons will maintain stock compression (17.5:1) even with the valve cuts.
The FEA analysis, if it can be believed, shows these to be 50% stronger than stock. This does not account for the steel implants in the piston. Only the Aluminum.
The surface areas on these pistons are less than stock. This should help the heat soak.
The bowl width across the pin is the same as stock, but shallower. I am not sure how this will affect the injection fuel plume. It does add a lot more meat over the wrist pin.
The top of the center dome is 30% closer to the injector. I don't know if that will have any affect at all on the injected fuel, but it does add meat over the pin.
These are slightly lighter than stock. but because of the base piston casting I think, not the bowl design. The chamber is exactly the same volume as the stock piston.
These pistons will maintain stock compression (17.5:1) even with the valve cuts.
The FEA analysis, if it can be believed, shows these to be 50% stronger than stock. This does not account for the steel implants in the piston. Only the Aluminum.
The surface areas on these pistons are less than stock. This should help the heat soak.
The bowl width across the pin is the same as stock, but shallower. I am not sure how this will affect the injection fuel plume. It does add a lot more meat over the wrist pin.
The top of the center dome is 30% closer to the injector. I don't know if that will have any affect at all on the injected fuel, but it does add meat over the pin.
These are slightly lighter than stock. but because of the base piston casting I think, not the bowl design. The chamber is exactly the same volume as the stock piston.