2g pistons or evo 9 pistons

[sharky559]

ive been doing some reserch on evo 9 pistons on 7 bolt rods and i really got confussed. people are saying to stay with 2g pistons an d some say to upgrade to evo pistons. could some one help with this.

 

[ezz-e]

Look at the picture in that thread the 2g piston has a much deeper combustion pocket then the evo piston.
The proper way to no what compression ratio you will have is to cc the top of the pistons.

 

[sharky559]

what about the evo 8 pistons are they just like the evo 9 pistons and can i use them on 7 bolt rods to

 

[Sirnixalot]

i've gotten a set of these off evolutionm.net for my 3 whenever i go to do a rebuild.

Will just buy the graveyard/hastings/whatever rings and reuse the evo 9 rods with arp bolts.

 

[Deuce_three]

This was covered in the link provided by Vette. Overall if you read carefully through the article, the headgasket used on a dsm is thicker then the evos. This could be 1 of the reasons why the evo has an overall higher C/R then stock 2g pistons.

Other then that, I recommend this to anyone looking for a setup that can withstand more abuse then the stock 2g piston can offer.

 

[NOSLO2PT0]

The other reason you get a final CR of 8.8:1 with the EVO pistons in an EVO is due to the 43cc combustion chamber on an EVO head vs a 47cc combustion chamber in a DSM head.

 

[Strm Trpr]

The other reason you get a final CR of 8.8:1 with the EVO pistons in an EVO is due to the 43cc combustion chamber on an EVO head vs a 47cc combustion chamber in a DSM head.

This is correct.
To everyone that said you retain 8.8:1 static compression ratio is retarded.
Evo's also use a head gasket that is .034" thick vs dsm's at .042".

 

[DsMGsX28]

are there any machining required for this setup?
thanks

 

[NOSLO2PT0]

are there any machining required for this setup?
thanks

Nope. Just a hone and new rings if your cylinder bores are ok.

 

[spawn87]

Nope. Just a hone and new rings if your cylinder bores are ok.

doesn't that count as machining?

well for the pistons i am running the 9s on a 6bolt bottom end with a 2g head and i like it. yes the low end power is not as responsive but once you start building a motor and go bigger turbo your gana loose it anyways. not to mentioned our stock engines are pretty beefy already so a little lost is nothing to loose sleep over.

if your gana put them on a 7bolt then like mentioned before me you need cylinder bore and new rings (dsmgraveyard has some nice ones for a good price.)

if your going to rebuild a 7bolt bottom i say at least get a/m rods to go with those pistons. IMO

 

[CanMan]

doesn't that count as machining?

Could be, but you can easily do it at home.

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[Tanro]

Evo 9 pistons have been shown to yield close to an 8.5:1 compression with the older style DSM head as opposed to the evo head. This is because the piston is shorter. And sits a bit lower at TDC. But this is a much superior construction quality/material quality piston.

 

[gixrman]

I've been running USED EVO8 pistons/rods since 2006 in a 7bolt with no issues. Heres my original old post from 06'
http://www.dsmtuners.com/forums/newbie-thread-graveyard/244184-can-anyone-help-me.html

 

[1G King Koopa]

Go with the evo's!

 

[ViciousLord]

cant one run a thinner headgasket to bump up the compression?

 

[NOSLO2PT0]

Evo 9 pistons have been shown to yield close to an 8.5:1 compression with the older style DSM head as opposed to the evo head. This is because the piston is shorter. And sits a bit lower at TDC. But this is a much superior construction quality/material quality piston.

You have any evidence of that? The 4cc difference in the head drops compression almost .6CR. Then that 1/8" gap with the piston drops the CR down even more.

I've asked this a few times already and have gotten no replies. Would someone with the EVO 8/9 pistons and a regular 47cc DSM head, do a compression test and post result??

 

[CFeclipse]

You have any evidence of that? The 4cc difference in the head drops compression almost .6CR. Then that 1/8" gap with the piston drops the CR down even more.

I've asked this a few times already and have gotten no replies. Would someone with the EVO 8/9 pistons and a regular 47cc DSM head, do a compression test and post result??

I used to have EVO 9 PISTONS & HEAD GASKET RUNNING WITH NO PROBLEMS for about 1 year then i upgrade to WS 9:1
i just make little modifications to the Head gasket and it work PERFECT so i assume my compression was like 9:0 running EVO 9 PISTONS & HEAD GASKET...

 

[crazyboy81]

Can't you just shave the block some to bring CP up? How much can be taken off?

 

[92EagleAWD]

#1 Whats modifications did you do to the gasket to make it work? that seems a bit extreme, cant you just buy a thinner gasket?

#2 What rod bearing do you go with if you use and EVO Rod/Piston combo?

 

[ramsack]

The EVO piston will sit at the exact same height in a DSM block as it does in an EVO block. Math applies. The same deck height, same stroke, and same rod length means the head gasket thickness and 4cc/cylinder head difference is what disables one from making 8.8:1. I have a question, can you mill enough off a DSM head to get down to 43cc without going out of spec and having valves smash?

 

[Strm Trpr]

^^^ You sir, are incorrect.
You can clearly see in this post that the Evo Piston sits below the deck at least .060".

http://www.dsmtuners.com/forums/152222200-post28.html

Last pic seals the deal.

I just calculated my static compression ratio for my build using Manley 8.5:1 off the shelf pistons, and the numbers came out to be 8.3:1 using a .055" Felpro Permatorque Head Gasket.

Combustion Chamber - 47cc
Head Gasket Volume - 8.3cc
Deck Clearance - 1.7cc
Piston Dish Volume - 12cc
Cylinder Swept Volume - 505cc
Total - 574cc

Formula for calculating static compression ratio is - Total Volume/TDC Volume or 574cc/69cc = 8.32:1 static compression ratio

 

[ramsack]

Where are the pictures of the EVO pistons sitting in an EVO block? No one has stated whether or not the EVO pistons sit flush or are sunk below in an EVO block. You can also easily see the dome made in the EVO piston is a lot less in volume, so it's not simply just 2g-like pistons with a 1mm drop. You want to seal the deal with a partial equation? Find me measurements that say the deck heights are different.

 

[Strm Trpr]

Where are the pictures of the EVO pistons sitting in an EVO block? No one has stated whether or not the EVO pistons sit flush or are sunk below in an EVO block. You can also easily see the dome made in the EVO piston is a lot less in volume, so it's not simply just 2g-like pistons with a 1mm drop. You want to seal the deal with a partial equation? Find me measurements that say the deck heights are different.

Ummm, Evo 4g's have the same deck height as DSM 4g's.
229mm

You want to really cook your noodle, compare specs for Wiseco Evo pistons vs DSM pistons.

http://www.wiseco.com/Catalogs/SportCompact/MiniMitsu.pdf

Better yet compare Manley pistons.
http://www.manleyperformance.com/sc/mk/mitsubishi/4g63_pistons.shtml

The 4cc difference in combustion chamber size is good for a 0.5 pt drop in static compression ratio.
Now throw in the thicker DSM head gasket and an even greater drop in static compression ratio.

 

[crazyboy81]

Evo pistons from Mentor Mitsubishi run from $62-$72 each! One type even comes .025 oversize

 

[ramsack]

OK THEN? The 2 blocks are identical in height, stroke is the same, rod length is the same, the pistons will sit below the deck in an EVO, as well, therefore the thinner head gasket and smaller combustion chambers is what is enabling 8.8:1.

 

[CFeclipse]

#1 Whats modifications did you do to the gasket to make it work? that seems a bit extreme, cant you just buy a thinner gasket?

#2 What rod bearing do you go with if you use and EVO Rod/Piston combo?

i used 6 bolt rods with evo 9 pistons i just make like a couple of holes for the drain lines... Pretty easy never had a problem...