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flat tops


Guest gikoro23

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Guest gikoro23

would it be ok to run forged flat tops in a turbo motor with a t3/t4, to4, or gt40 turbo.

or would i have to get forged dished pistons.

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Depends on the compression I guess....If you're doing aftermarket pistons, usually you have a choice of compression ratios. I've heard people say all things being equal, dish is better for turbo, supposedly it concentrates the combustion event into the piston, but that's just what I've heard.

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Guest gikoro23

i would want to make 25psi at least i want to push around 55psi... and the people who have forged pistons already made only have flat tops. and JE wants 960 for all 6, and other people have flat tops for 600 including the rings. so i either pay 360 more and get custom pistons or use the money for somthing else.

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55psi of boost?! Let me know how that works out for you...I was actually referring to the static compression ration of the piston, like if you wanted it to be 8.0-1, 8.5-1, 9.0-1 and so on. If you are using flat top factory pistons, that would leave you with a high compression ratio depending on what components you were using them with, but if you are getting straight up aftermarket pistons, the manufacturer should be able to tell you what the CR is going to be with that piston.

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Guest gikoro23

i was kinda throwing a high number out there just to get a point across, but my question was what would be better flat tops or dish with a large turbo pushing a lot of psi. i know the p90 has the largest combustion chamber at about 53.5cc. im going with that head and piston dish volume on a dish piston is 10.9cc with stock rod length, and stock crank. it should make a little less than 7.5 compression with dished pistons. wich is great for a large turbo application. but i was wondering how the l engine will hold up with flat tops with it making around 8.5 compression. i would like to go with flat tops also because of the lag on the semi large turbos. with flat tops i will have more power right away and then hit my boost and have even more power.

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Guest DedPyro

Don't know if I'm just butting in but the more PSI the less compression you want. It is however a trade off. boost only kicks in higher in the RPM range lets say 2500 to 3000. (just example) so if you want 50psi you need around 6-7:1 compression. Remember boost is pressure above the 14.5psi of atmosphere so that's around a total of 65 psi. So do you want a dog on take off with a screamer on the highway or do you want a bullet all around. You can also invest the money in O-ringing the block and head (mucho money) stay moderate like 15-20psi. get dished pistons or (flat tops with a 2mm head gasket approx. 8:1 comp.), a good fuel management ECU (ex. megasquirt)a rising rate fuel psi regulator, head studs and a GOOD head gasket, try 7.5:1 compression.

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Please :search:

 

This has been covered lots of times and people have provided numbers for their setups as well.

 

In short: Flat tops and a P90 will have good quench, with plenty of oomph at no/low boost and still take high amounts.

 

Granted your fuel system and everything else is up to par if not better.

Mario

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