Piston Bowls
- Thread starter Fingers
- Start date
I can't claim power increase or flow increase. All that started with people noting the engines sound different and trying to explain why. If it is because the exhaust valve is slightly more unveiled, well that's a good thing.
BTW guys. I have only 0.020 over piston blanks in stock right now. Other bores can take 4-6 weeks to get in, but are available. I highly recommend that you at least bore out the block the 0.020 if your going to do a build.
I guess people just don't like oval bowls!
Will someone please break a set of these and shut me up?
Nah, people dont like change, or/and dont like to think there is something better than what they already have and stop at nothing to find a flaw so they can point and laugh.
I don't think there was a "concept" on bowl design as it relates to combustion, flame propogation, or performance.
From what I gathered (I don't want to put words in his mouth so he can correct any issue I'm inaccurate on) it seems like Jon looked at what was happening (piston cracking along the pin) and did some modeling and found the area that cracks happened at the weakest portion of the piston by it's design.
He was looking for a way to eliminate the weak link. His biggest concern was increasing strength in that area, while still having a "bowl" for combustion and doing so in a way to keep CR within certain limits.
I'm ASSuming that he had a few limitations:
1: There has to be some sort of "bowl" for combustion to take place
2: There has to be enough meat above the pin to increase the overall strength in that area (whole reason for the project).
3: Injector spray pattern (dictating minimum size of the bowl)
4: Compression Ratio
5: Others that I'm not thinking of
Those factors led to a bowl that was as wide as the OEM bowl (to keep the spray mostly in the bowl......or at least as much as stock does), and because of that factor combined with making it a shallower bowl (leaving more material above the pin) while needing enough material removed for proper CR values, it necessitated elongating the bowl on opposite sides of the pin.
This led to the shape which he modelled and found to be "stronger" and he took a chance with it (although he did his homework it wasn't just a WAG). I don't think he was worried about proper combustion or emissions as long as it still ignited the fuel in a controlled manner. The changed exhaust note was a byproduct (not a design feature) as well as the unshrouding of some of the exhaust valve (not a design feature, but a welcome byproduct), which may be the reason for the changed exhaust note or it could ALSO be due to the way combustion takes place which may change the harmonics in the cylinder (I'm assuming if you could look in the cylinder at the flame on a stock bowl vs. this would be different).
Jon, have you compared (with your chamber pressure monitoring system) the stock bowl vs. these on a similarly hardwared and tuned engine? It would be interesting to see if or how it affects cylinder pressure (if at all assuming same CR)?
When they were first discussed/shown, piston cracking was a hot topic. Some were going to forged pistons because of it, but were unsure of ring life and/or piston life on a DD. Monotherms were not out (and even now I have not heard much from them), so these were a potential alternative for a spirited DD and possibly more. These pistons will have a breaking point, myself and others would like to see them do well at it will only be better for all of us. I doubt they are the end all and be all of pistons and for a extreme high HP purpose built rig, there are most likely better alternatives, but for the price and their "wearability", it would be a good answer for a large percentage of the populus who still drive our trucks but like to drag race, truck pull, etc.
I guess only time will tell, but much like "Ben's special rods" the proof will be in the pudding. So far these are doing much better than those :spit:
And even if they do break, it will be interesting to see how much it took to make that happen.
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Any particular reason for this Jon? I have a low mileage block with minimal wear I was looking to do. I was hoping to go stock bore leaving me room to go larger in the future, and then even larger as things wear. My gasser engines often have multiple "lives", each time going a little bigger as they wear. After a certain point they are tossed. I'd rather not get there too quickly with this one
As for someone finally breaking one of these for you, do you have many sets that have been in use for a while in decent power vehicles? I know there are a couple, just wondering if that is it? Were there any competition vehicles that ran them this year? Not that non-failure proves they are great, but it would mean they aren't worse.
Edit: I know the video of Brett's truck was posted and those numbers are nice, but some feel part of our problem is moving these heavy pigs around. That is a bad-azz truck, but I don't think near our weight. Wondering if there was a more apples to apples example.
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One resin I asked was to see if he might have found that in his models for design because of low lift efficiency and the second people say the motors sound different. How the air is moved in and out of the cylinder is most likely why the different sounds. Anything that can add to efficiency will increase power and reliability.
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I guess people just don't like oval bowls!
Folks, I've been working on this design for over two years now. Heck, this thread is almost two years old. I've looked at designs from the gas, big diesel and even the nitro burner worlds and borrowed what I could from each. I've asked a lot of questions and taken a lot of suggestions. I've cranked it through computer simulations and a couple less than scientific static tests. It is the best I (we) can do with the mechanical envelope that is available to us.
Will someone please break a set of these and shut me up?
Do I get a discount on the next set if I break them?
With all the horror stories of cracked pistons I personally could care less about any of the technical details as long as they are strong and hold up to high HP. If you do lose a few HP because of bowl shape there are plenty ways to get it back. I plan to use these in the build I'm working on now, I'm planing for 800 or so, piston performance is not a concern of mine but strength and longevity is.
Thanks for that. Very close. The route there was a bit more twisted. I leave that for a later conversation.
Though performance was secondary to strength, I still needed to keep an eye on the quench areas and spray pattern. In the process, I got some secondary results like less heat exposed piston surface and slightly unveiled valves.
Pressure wise, there really isn't a big difference with these pistons. I am running a little higher CR in my engine just to prove a point, but it looks typical to me.
I don't want to promise the world here. Everything has it's limits and these pistons are no exception. I started with a known base product (Mahle race cast) and tried to improve on that. I personally don't have an engine strong enough to test these to failure.
Besides Mr Broviak, I've had a hard time getting end users to talk about the pistons. Secret Squirrel mentality.
I for one don't have a problem telling the in and outs of a product that I use. I will build another for one of my other trucks and will give your pistons a try to compare with what I run now. Truthfully my intentions will be to switch my motor now into the other truck a put these in my toy. When that happens with my luck I will be able to give you a breaking point. LOL
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i pick up a set tomorrow am.
see how they hold up in my setup nothing high HP less then 300fwhp.. with avg of 2k mile a week and 23,000lb. should work nicely
see how they hold up in my setup nothing high HP less then 300fwhp.. with avg of 2k mile a week and 23,000lb. should work nicely
i pick up a set tomorrow am.
see how they hold up in my setup nothing high HP less then 300fwhp.. with avg of 2k mile a week and 23,000lb. should work nicely
Very cool, Adam. What compression ratio?
Hopefully will fire mine up tomorrow! I'm excited to say the least and I will get some videos for you guys.
I know I'm happy with my choice to run these pistons. Whether they are proven yet or not I would rather give something a try that in my eyes if nothing else should be atleast as strong as other cast options but with the potential to be considerably stronger.While I don't have a ton of time on them yet the motor sounds great with them and spooling the s475 as a single was no issue and the new big twins so far seem to spool a lot better than expected without any tuning changes for the new setup so I haven't seen any performance loss running these in any way.I look forward to trying to hurt them being at the track or just the pounding it always gets when it's driven.
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