higher compression pistons

WPDiesel

WPDiesel

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Joined
Mar 25, 2011
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Maybe this has been done 1000x I'm wonder if the CR piston works in the VP block? The only difference could be in wrist pin height. I'm looking for a higher compression to help spool up at lower rpm.... wonder how to do so without going forged custom pistons because they last about 20k on the street. Or is there a way other then drooping valves close to piston like add material or coating the piston?
 
WPDiesel said:
Maybe this has been done 1000x I'm wonder if the CR piston works in the VP block? The only difference could be in wrist pin height. I'm looking for a higher compression to help spool up at lower rpm.... wonder how to do so without going forged custom pistons because they last about 20k on the street. Or is there a way other then drooping valves close to piston like add material or coating the piston?
Click to expand...

smaller cc piston bowl
deck the block
longer stroke crank and deck piston

only cheap options i can see as a simple upgrade.

personally, for quicker spool, id leave pistons alone and try different camshaft design, heat wrap the exhaust side, and play with fuel/timing. just my $.02
 
Well problem is I never find a can worth a **** unless its a mechanical motor. I guess how would u make the piston bowl smaller CC without doing a forged piston.... really don't want to deck the block and take out my grooves but probably the cheapest option.... I Just think the 6.7 crank would be too much stroke to mill the top of the piston down wouldn't it? I'd be in a ring land?
 
With the VP being limited rpm it just falls off fueling at about 2900 i thought my twins need some more drive for low end. Smaller twins isn't an option I'm not going backwards in HP ill drive my laggy turd around before that or just drop the common rail in it Like I'd planned on..
 
Call Karl at redline diesel, he has a sweet setup in his drag truck and might be able to help you out.
 
WPDiesel said:
With the VP being limited rpm it just falls off fueling at about 2900 i thought my twins need some more drive for low end. Smaller twins isn't an option I'm not going backwards in HP ill drive my laggy turd around before that or just drop the common rail in it Like I'd planned on..
Click to expand...

dending on what electronics you are running you can extend your power band out. fwiw the last time i dyno'd my truck it made power out to 3400rpm. the HO piston has a smaller bowl but not sure how much of an increase in compression you are looking for.
 
jlbayes said:
dending on what electronics you are running you can extend your power band out. fwiw the last time i dyno'd my truck it made power out to 3400rpm. the HO piston has a smaller bowl but not sure how much of an increase in compression you are looking for.
Click to expand...

What electronics are you running? And I did do some dirt on the ho motor its 17.**:1 I can't remember but I was thinking 19 or so...
 
jlbayes said:
dending on what electronics you are running you can extend your power band out. fwiw the last time i dyno'd my truck it made power out to 3400rpm. the HO piston has a smaller bowl but not sure how much of an increase in compression you are looking for.
Click to expand...

if I remember correctly the standard VP compression is something like 17:1 and the HO is something like 19:1.
I'm not entirely sure on that though.

EDIT: ^^^ beat me to it
 
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Standard output - 16.3:1
High output - 17.0:1

There will be a forged piston available early next year with a much wider bowl and roughly the same compression as the high output version.
 
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Why go to all the trouble of a rebuild if it's not necessary ...... ported head is gonna suffer from velocity issues on the exhaust end either way ...... need to gain some of your velocity back ...... either smaller turbo or spool flange to increase velocity behind turbo ....... either that or go get a new head that's not been ported ......imo of course
 
The higher compression pistons can give you slightly better fuel economy with a little snappier throttle response. The lower compression are better for higher boost applications.

I'm in the process of rebuilding and will be putting in the HO pistons along with the new switch blade turbo and cam shaft. Porting does not help fuel economy. You want high velocity. The right cam can help fuel economy in two ways, it can lower the pumping losses and it can allow better filling of the cylinder with less HP loss. The right fuel injector will help fuel economy as well, as the injectors get larger, they advance the timing. For best economy you want to lower your pumping losses as low as possible and you want to lower your throttle input as low as possible. Then the rest just becomes drive line losses and drag.

I will be running at around 1600 RPMs and 2-3 lbs of boost at 65 mph. The cam will lower the torque curve to around 1400. When towing I will put it in tow haul and kick out OD so that my RPMs will be around 1900 at 60-65. Gotta love Allison.

MPG goal is around 26-28 on the highway and to get this I will probably have to change out the front wheel bearings with lock out hubs. (there's a guy who got 27 consistently with his truck with some of these mods.)

Now if you are going for power then some of these things overlap and at some point and fuel economy just goes out the window.
 
I would give Monster Pump Mike a call he knows more about VP motors then anyone . I know on some of the big cube motors he builds he welds up the 6.7 pistons and recuts the bowls in them for the VP injectors. His number is 419-237-1521
 
Thanks guys I think I've decided to try the 6.7 crank and mill the tops of the piston I believe spray angle is a 128* if I've been told right..... I'm guessing th VP don't make enough power to blow a block out at a 4.25 bore? Isn't that stretching its limits? I guess I know on 6.7 blocks they like to crack and blow I couldn't imagine a 5.9 being much better!?
 
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