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Low Compression pistons


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Hi chaps,

I am in the process of force inducting my car and would like to fit low compression pistons in my Euro T sport (sportivo). My quick and rather noobish question is if I do this and then reassemble it will it start and run on the stock ECU? I did the maths and think it would start but I would be slightly low on power but I wondered if anyone had any experience of this?

The car is used frequently but I want to get the pistons changed in 5 days if possible before I start with the supercharger. I figure having a strong bottom end would allow plenty of boost.

Cheers

NRG

www.nrgizerbunny.com

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as far as i can see there is no reason why the car would not function with the stock ECU. Do bare in mind that it will be down on power... untill you supercharge it of course.

Before i turbo'd my celica, I put a thicker head gasket put in (which also will lower compression) and this did not effect the car (besides a small drop in power)

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as far as i can see there is no reason why the car would not function with the stock ECU. Do bare in mind that it will be down on power... untill you supercharge it of course.

Before i turbo'd my celica, I put a thicker head gasket put in (which also will lower compression) and this did not effect the car (besides a small drop in power)

Thanks for that, I'll go ahead and order my mahles now. bit of a drop though from 11,5 to 9,0!

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as far as i can see there is no reason why the car would not function with the stock ECU. Do bare in mind that it will be down on power... untill you supercharge it of course.

Before i turbo'd my celica, I put a thicker head gasket put in (which also will lower compression) and this did not effect the car (besides a small drop in power)

Thanks for that, I'll go ahead and order my mahles now. bit of a drop though from 11,5 to 9,0!

are you buying a new block too? as you cant touch the original bore due to the mmc lining you'll want resleeving or a new block unless you are willing to put up with some piston rattle like most do when not doing the job properly.

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I'm told that these pistons

http://www.monkeywrenchracing.com/product_info.php?cPath=21_23&products_id=31

are just a drop in. Sleeving doesn't seem to be recommended given how slim the walls are. Plus you are hardly a good person to take advice from

Edited by nrgizerbunny
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I'm told that these pistons

http://www.monkeywrenchracing.com/product_info.php?cPath=21_23&products_id=31

are just a drop in. Sleeving doesn't seem to be recommended given how slim the walls are. Plus you are hardly a good person to take advice from

If you want an oppinion on sleving/honing/whatever talk to XOOM or CHA54 on here, they are both EXPERTS on the *ZZ motors.

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The sleeving is only required if the bores are too large for the pistons. Contact MWR for pistons sizing as last I heard from them they were getting a slightly larger piston done to cover the people with high mileage. The Mahles work fine with the sleeves, but if you do sleeve go for the Wisecos as they are a lighter piston. Keep in mind that sleeves actually reduce the ability to transfer heat from the cylinder to the cooling system; hence why Toyota used MMC coating instead (they did test sleeves during the development of the engine). You can also look into the cost of a short block from Toyota if your bores are out of spec; as there was a lot of users in the early days of the 2zz sleeves complaining about dropping sleeves. The solution was to get Darton to sleeve the blocks.

The piston slap is unavoidable when cold as they are forged pistons and forged pistons expand more than cast; but they will quieten up once they expand to fill the cylinder better. As for any wear caused by the slapping, who knows how significant that is in the long term with the MMC.

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I cant see any reason why the stock ECU couldnt run the decompressed setup

When we installed the wiseco's in my sportivo going to 8.8 compression we put it up on the dyno and there was no need to change the tune on the powerFC at the time.

The loss in power was about 15% ..... otherwise everything worked fine

The mahles werent available at the time i built my engine & being that i went with the wiseco's meant we had to get the block sleeved. As long as you are within the spec's for the mahles it should be fine but as stated the wiseco's are one extremely light piston.

Sleeveless

block_sleeveless2.jpg

block_sleeveless1.jpg

Sleeved

block_sleeved.jpg

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depending on how much pressure your goin to put the the engine lower compression isnt required as alot of new factory turbo engine will use high 10-1 compression ratios eg mini jcw has 10.5-1 comp ratio

so if your only gonna run like 6psi as long as you know a good tuner 10+-1 comp is tunable

ive seen standard 4ag20v which have 11-1 comp run 10psi no dramas and they make almost as much power as mine and im running 20psi but only 8.2 comp so think about that more comp less boost for similar outputs

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