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Lower compression piston source

Rockabillyrat

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Mahle offered pistons with two different Ricardo bowl depths. One was .158" The other was .064" I believe this was how the compression was lowered on the 6.5 but I never confirmed it. I've always wondered if compression was lowered on purpose or they increased the bowl depth to help with the dual swirl. Anyway if your going to have a set of pistons machined down I would suggest using the deeper bowls so you don't end up effecting the combustion process. I'm a big believer that the Ricardo bowl is necessary on an IDI and it should not be removed to lower compression.

I believe Mahle still offers the .010 decked pistons. Personally I would leave the compression stock myself. Guys are pushing square cups and stock compression to 500hp with great success.
 
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Will L.

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Mahle offered pistons with two different Ricardo bowl depths. One was .158" The other was .064" I believe this was how the compression was lowered on the 6.5 but I never confirmed it. I've always wondered if compression was lowered on purpose or they increased the bowl depth to help with the dual swirl. Anyway if your going to have a set of pistons machined down I would suggest using the deeper bowls so you don't end up effecting the combustion process. I'm a big believer that the Ricardo bowl is necessary on an IDI and it should not be removed to lower compression.

I believe Mahle still offers the .010 decked pistons. Personally I would leave the compression stock myself. Guys are pushing square cups and stock compression to 500hp with great success.
I have always wanted to see a piston swap of 18.5:1 with the bowl vs a shaved piston 18.5:1 and no other changes. Engine dyno would be neat to see power differences, but also get them a set load and just burn 1/4 gallon of fuel till empty for mpg.

Then now with the way TSP has the taper cut to flare out across the piston- since I bought a set I obviously think that will do well.

There is the computer simulation of liquid/air flow- that would be great to see the difference- but wouldn’t be as accurate as to what end results are.
 

Twisted Steel Performance

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A call to the tech line at Malhe is easy, and they can answer any question a person has.... The 18:1 they offer now they raise the pin around .041-.044"

At one time the bowl design may have been played with but I have measured each set for a number of years now and haven't seen a change..
 

Rockabillyrat

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I thought I remembered reading that they changed the pin height
I would like to see information on that. Ive never come across that before. We need @n8in8or to measure some pistons for us. he has probably collected every version of the 6.5 ever built by now 🤣

I have always wanted to see a piston swap of 18.5:1 with the bowl vs a shaved piston 18.5:1 and no other changes. Engine dyno would be neat to see power differences, but also get them a set load and just burn 1/4 gallon of fuel till empty for mpg.

Then now with the way TSP has the taper cut to flare out across the piston- since I bought a set I obviously think that will do well.

There is the computer simulation of liquid/air flow- that would be great to see the difference- but wouldn’t be as accurate as to what end results are.
Same here. I have research papers that show the dual swirl in detail. But I would love to see a comparison on a machined piston like what TSP does.
 

SnowDrift

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Those pistons from BMI (Bostic, if I'm not mistaken) come with rings and the ad makes some bold claims about the rings, in particular. From what I've read about rings, Total Seal would still be the way to go if a guy wants to keep clean oil, correct?
 

SnowDrift

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I called them out of curiosity and was told they don't have any more of these marine pistons, but they may have another run of them made if they get enough inquiries on them. I was also told that Unique Diesel buys their marine pistons from Bostic, while I was on the phone. I suppose this adds up if it is really the case since those from Unique are a little more $ than the ones directly from Bostic.

Will, the set you bought - were those new stockers that you're sending to TSP for the machine work to have the compression lowered?
 

Will L.

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No, he bought new sets and cut them in a run of them he was making.
Talking to a guy at gep when they were building engines at navistar- the pistons were bought under same part number from mahle that gm did when building the 6.5 for years.

So while Chris may or may not know the manufacturer of the pistons he bought to have cut, I have my belief of who made the pistons. It is always possible there is another manufacturer making some- but 6.5 pistons are not exactly a hot commodity, so idk what other mfrs make any. I suspect someone could have batches made in china,

Bostic is a big outfit that does descent volume. They sell new optimizers and sold new p400s. Many have been happy with results- I will be leary until the date 32nd of Neveruary.
 
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