TTS steel pistons
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I came up with the wade+killerbee=#1 team tag
I just 2 and 2 together and figured they would make a perfect match :roflmao: I think if wade used some of killer Bee's killer tuning and one of his induction overhaul kits he might stand a chance actually beating the banks truck fair and square :rofl:
For what it's worth, a properly designed monotherm should weigh about the same as a race aluminum piston. We saw that back in the late 90's when running against the DAF trucks. We had some of the two piece pistons (steel tops with aluminum skirts) and they weighed less than the DAF's all aluminum pistons. The old two piece pistons were the precursor to the monotherms. I guess the big question is about the billet material. I thought all montherms were forged, but maybe this was a cheaper / quicker way (not having to modify a die) to give us a steel piston without all the long lead time.
From looking at the pic, they could have went a lot lighter for a race Dmax piston. You don't need the toroidal (donut shaped) bowl, you could do like the Arias and go "dished turbo" design since you're not worried about emissions.
The first pistons we ran in Casper with aftermarket rods were actually "shortened". In other words, there were no valve reliefs and no delipping, we cut the material straight off the top squish area. Didn't seem to change much. For some reason, that engine rev'd like a LS1.
I've often wondered if you could just do a flat-top Dmax piston with 2 rings for racing apps. This would make the lightest possible design and subject the piston to the least amount of heat input.
i was talking to a detroit diesel tech about the 2 piece pistons they use, aluminum skirt and steel face...
he said they hold up to a ton of abuse in big rigs, not sure if the idead would work for us though.
he said they hold up to a ton of abuse in big rigs, not sure if the idead would work for us though.
Isn't a portion of the duramaxes efficiency tied to it's bowl-style pistons? Do you not think flat tops would put a big dampener on the combustion process of the HPCR platform?
Do any other HPCR engines ever have flat top pistons? Do any performance engines use flat tops? I would have thought dome or dish were more common place than plain flat tops, no?
I guess what compression that would be lost from any shortening of the piston height would/could be more than picked up by filling in the bowl.
Hello 22:1 CR.Just thinking out loud. Got me chewing on it now.
Isn't a portion of the duramaxes efficiency tied to it's bowl-style pistons? Do you not think flat tops would put a big dampener on the combustion process of the HPCR platform?
Do any other HPCR engines ever have flat top pistons? Do any performance engines use flat tops? I would have thought dome or dish were more common place than plain flat tops, no?
I guess what compression that would be lost from any shortening of the piston height would/could be more than picked up by filling in the bowl.
Just thinking out loud. Got me chewing on it now.
I don't have a Arias in my hand, but it seems the turbo dish is only about 1/4" deep at most. So a 16:1 cropped piston might only have a 3/16"? headspace. Dunno. Need to do the math.
You make HP by getting the air above the piston as hot as possible to create pressure. If some of the fuel doesn't burn, it will use up heat as the fuel vaporizes. So if too much fuel sprays the walls, it will lose power. But we are already spraying the walls to an extent with big fuel. You can see the "flower" going all the way to the wall, and the black smoke is fuel that atomized too late. Even with the cropped pistons we first ran, Casper never did smoke a lot once boost hit.
But the point is moot. I don't have the money or the resources to make custom pistons. If it's not a retail item, I can only bench race it.
EDIT: Yes, flat top pistons are fairly common with V8 gas engines. It's the most efficient shape. You only dish or dome pistons when you have to due to compression or chamber shape requirements.
The primary reason for the dished piston chamber is to keep the spray off the walls. At the pressures the injectors run at, the spay actually will push past the top rings as well as wash off any lube that might be there.
There have been many design attempts to keep the chamber in the heads, but the piston bowl has worked out better for power and durability. One reason is that the injectors alone fuel only the top of the combustion chamber. By spraying into a pocket in the piston, the fuel has a tendency to follow the piston down and distribute fuel throughout the cylinder. Clever.
There have been many design attempts to keep the chamber in the heads, but the piston bowl has worked out better for power and durability. One reason is that the injectors alone fuel only the top of the combustion chamber. By spraying into a pocket in the piston, the fuel has a tendency to follow the piston down and distribute fuel throughout the cylinder. Clever.
More than some but less than most. Thanks for asking so we could clear that up.
I know all the cat motors I work on at work have the 2 piece pistons; aluminum skirts and steel pistons. If the motor has been torn down and has the outdated all aluminum pistons, they receive new 2 piece units as an "updated" part. Nevert seen a piston from those motors crack, but ive seen way too many cranks split in 2.
Pat, if you could get your hands on a set, do you think you would give LSR another shot as pistons seemed to be your biggest hurdle? I'ld be willing to donate a little to the cause, and I'm sure many others as well (much cheaper than building our own LS racer)
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As for the spraying the walls, the other big factor is the spray angle of the injectors. From what I have read (I know, VERY dangerous), the stock injectors are very flat. They were tuned for emissions and spraying very short shots close to TDC.
Typically you want a narrower spray angle so that the fuel hits the bowl and then rebounds back up to get the most uniform distribution. Thus the interaction between spray angle and piston bowl design. It's also implied that the injection duration is key to these two parameters.
Typically you want a narrower spray angle so that the fuel hits the bowl and then rebounds back up to get the most uniform distribution. Thus the interaction between spray angle and piston bowl design. It's also implied that the injection duration is key to these two parameters.
IIRC, it's 158° included angle, or almost horz. That's 11° from horz. It's aimed right at the wall. Any more deg. and it would hit the head with the spray.
So the marking on the tops of pistons, whether from proper tuning or total blow torch erosion is from a star shaped flame propagation not from direct injector spray pressure?
My bestimate:
When you spray stuff out of a nozzle at high speed, it starts off straight, then becomes a "bulb". Kinda looks like a light bulb.
Now, when you look a brand new OEM engine (test run only), it has the famous star-shape on it, fat at first, then thins out.
So the piston must be rising into the "bulb" region of the fuel, or falling out of the bulb area to make that kind of shape.
I don't think fuel pressure itself can erode a piston, because we run max pressure on "tune only" truck, and piston erosion doesn't happen regardless of timing and duration.
Talk to Steve today, From picking up the steel piston to a stock lbz piston, I could not tell the difference in the weight. If I remember correctly the steel piston weighs 13 grams more than the stock lbz piece. Ready for price?.... $4400. the last photo is lb7, lbz, lml, and then the steel. Made it a point to go by the booth to get some info.
