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Picking out a piston/rod combo...what's your goto currently?

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Guys take it easier eh, no need to bash each other for things like this.

From personal experience I am running an entirely stock 7 bolt which initially had the stock 8.5:1 pistons but had to replace them with 10:1 N/A pistons (don't ask why long story). Take it with a grain of salt, but I wouldn't say there is a major difference in spool times or power. Then again, the car hasn't been tuned for the higher comp. pistons so that's also a factor. Runs at 12psi on stock T25.

We can all agree that, if we could get around knock effectively, more compression will be better. It's simple math; more overall efficiency. But to really decide if you want to go this route, it would really depend on your build and how you'll be using your car.
 
How does lower compression spool a turbo earlier? I thought higher compression caused to spool earlier. Not trying to debate, just interested in the reasoning.
A less thermally efficient engine (lower compression) wastes power blowing it out the exhaust as extra unused heat. This spools the turbo.

Higher compression makes more torque off boost and feels more responsive though.
 
Is the higher CR motor blowing "more... less heated" gas out per cycle than the lower CR one? If so, how does that compare.... wouldn't it be kinda the same thing happening in the end? Less air that is hotter is better than more air that is cooler? Again, I'm just spit balling because I'm not an ME or anything.

Also, I'm leaving out the advantage that's already been stated of lower CR being that it's more tolerant to tuning f ups.
 
If money wasn't an option for me, my endgame would probably be Vader or R&R aluminum rods with wiesco HDs. The new age aluminum rods have really proved themselves to me, they will be going into my next engine for sure.

On the whole compression thing, if I were in his shoes, I would probably take the one or two psi more and get the same power safely, than have an engine that's much more prone to knock and unpredictable.
 
For pistons: You just can't go wrong with Wiseco HD's. But if you're looking for an equally reputable company with proven results I would try Wossner. They have treated me very, very well. Not just in performance and durability, but customer service that I have yet see others beat. Very responsive, very knowledgeable.

For rods: I have tried many and have yet to bend or break any one of the brands or styles that I have run. Unless you're trying to break records and play with the big dogs, just pick one of the reputable companies out there and run it.
 
Go on the link forum. Kiggly tested low compression on his methanol car.

From the borg warner site.
"The turbine performance increases as the pressure drop between the inlet and outlet increases, i.e. when more exhaust gas is dammed upstream of the turbine as a result of a higher engine speed, or in the case of an exhaust gas temperature rise due to higher exhaust gas energy."
 
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No dsmlink for him. He's only using :

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:)
Ill pretend I didn't read this blasphemy.

But to the methanol car, using this type of fluid would cause an increase in mass flow. (More meth is needed to be viable.) Ill have to hop over and give the Kiggly post a read as I do not know what they tested.
 
Ill pretend I didn't read this blasphemy.

But to the methanol car, using this type of fluid would cause an increase in mass flow. (More meth is needed to be viable.) Ill have to hop over and give the Kiggly post a read as I do not know what they tested.
He went from 9.6:1 to 7.5:1 on his methanol car. Everything got better.

When you are blowing air into the engine, a larger dish in the piston gives you more volume to blow the air into effectively increasing displacement. Whether or not it offsets the increase in thermal efficiency you get from increased compression is up to a lot of things.
 
Found it.
"First impression brake torques on 7.5:1 compression are good. The larger trapped volume required a decent change in VE and probably combined with better overlap flow it seems to spool a little better than 9.6:1. I opened it up from a 1.1 to a 1.25 ar turbine housing and it testing in much warmer weather it gets up on the converter just about identically. It isn't quick on the converter without the spray, but it will get there."

Not sure I totally agree with your thought process still. The turbine housing was changed. This lowers the ratios you were speaking to thus changing spool.
 
Put your thinking hat on for this. Lower compression spools the turbo at an earlier rpm. Higher compression can reach full boost in a shorter time from a given start rpm.

For what it's worth 10,000hp dragsters run around 7:1 compression.
 
I thought the discussion involved how fast the turbo spools vs compression ratios?
It does, but there are different ways to measure spool. If setup a spools fully by 5,000 rpms, but takes 3 seconds to get to that rpm from 4,000 rpms, does it spool faster than setup b that makes full boost at 5,050 but reaches that rpm from a 4,000 rpm start in 2.5 seconds?
 
I understand what you speak of.
Chances of OP running 100% nitro or meth? Little to none.
Based on 93 I have not seen or heard of any data supporting these claims.

You do bring up a good point though.
"e85" pistons are for sale.(10-11 comp ratio). IMO if nitro and meth react this way it would be smart to run lower compression when using something other then 93. So why do they offer high comp pistons for e85? Just something to think about.

On a side note, English claims 20+ hp gain when bumping up compression ratio by 0.5.

In the end, discussion aside, you make all of these decisions based on application. Is this going to be a 10k hp car? Or will this be used to get groceries? Will it be road raced? Will it be dragged? From there, you build to your requirements to achieve the goals. Each of which demand different setups for max output.
 
I chose 6bolt turbo tuff i beam rods with 625+ rod bolts, And 22mm pin for 7bolt piston choices., figured that may help at higher rpm, i liked 9:1 CR my last motor was decent out of boost, and easy to tune, kinda best od both worlds in my opinion, i used e85 also.

Pistons i habnt decided on but the wiseco 1400HD look good to me, or ross.

My car is a drag car though, and i be entering 67mm class when it's finished
 
Looks like some good info came out of my question above. I'd be interested to hear anything else people have to add to that.

I definitely understood what you meant, Donnie, about how the lower compression motor may get into boost faster but not hit full boost until later than a higher compression motor. I think this boils down to the same conclusion most of this car build stuff comes to which is build your setup for what you're trying to achieve.... and nothing else.
 
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