5S Crank in 3S block compression question.

Q&A regarding engines, turbos, and intercoolers and power upgrades

5S Crank in 3S block compression question.

Postby toybota » Wed Mar 12, 2014 6:44 pm

So I want to use the 5S crank out of my parts car to stroke my 3S-GTE out, I am going to get rods, pistons, new bearings, ARP fasteners and all that. But what is a good compression ratio to aim for? To keep stock compression,8.8:1 I would have to get a 0.6mm thicker head gasket. What Compression ratios are you guys running on stroked engines?
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Re: 5S Crank in 3S block compression question.

Postby Pipedreams » Sat Mar 15, 2014 9:37 am

Depends on what boost and fuel you´re gonna run. I´m at 10.2:1 but I will run up to 40psi of boost with e85. With low boost and gasoline 8.8 would be fine. With the increased displacement it will take less boost to make the same power as before.
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Re: 5S Crank in 3S block compression question.

Postby toybota » Sat Mar 15, 2014 3:07 pm

I plan on building the engine fully. It will be used as a daily driver so 91 octane and lower boost would be for sure. I do not want to push over 20 psi, as I've heard that 20 for a 3S is a reliable pressure to run. So on pump gas with 20ish psi would running 8.8:1 be best?
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Re: 5S Crank in 3S block compression question.

Postby ST_6396 » Sat Mar 15, 2014 3:46 pm

Anything around 9:1 or less would be fine. Even if compression ends up a little higher than 9:1 it should still be fine, but you'll have to go with a bit less ignition timing, a slightly richer air fuel mixture or water/meth injection(the option i would consider most). You also want to make sure you have a turbo that's able to efficiently work where you want it to.
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Re: 5S Crank in 3S block compression question.

Postby toybota » Sat Mar 15, 2014 4:52 pm

So should I aim for 9.1:1 instead of 8.8:1 in your opinion?
El Coño My 1990 ST185 Canada delivered Turbo 4WD. Bought for $1000. You could say it needs some work.

'00 Focus Wagon - Soon to be gone.
'90 St185 'El Coño'
'93 St184 Parts car
'85 MA61 Supra Daily Driver
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Re: 5S Crank in 3S block compression question.

Postby toybota » Sat Mar 15, 2014 4:59 pm

Pipedreams wrote:Depends on what boost and fuel you´re gonna run. I´m at 10.2:1 but I will run up to 40psi of boost with e85. With low boost and gasoline 8.8 would be fine. With the increased displacement it will take less boost to make the same power as before.


Just out of curiosity and in the interest of learning more about the S series engine, if I run about 20 PSI and use the 5S crank with cams, rods, front mount, exhaust, fuel and all that fun stuff what kind of power should I be expecting? I know it is a difficult question but what would your ball park be?
El Coño My 1990 ST185 Canada delivered Turbo 4WD. Bought for $1000. You could say it needs some work.

'00 Focus Wagon - Soon to be gone.
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Re: 5S Crank in 3S block compression question.

Postby Pipedreams » Sat Mar 15, 2014 8:31 pm

There are to many variables to give a good guess but with 2,2l and 20psi you should get passed 400hp.
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Re: 5S Crank in 3S block compression question.

Postby ST_6396 » Mon Mar 17, 2014 4:08 pm

Boost pressure is just a number, horsepower is made with efficient airflow. With a properly sized turbo you will make more power with less boost pressure than with an undersized turbo like the ct26. It's important to read compressor maps and find a properly sized turbo for your goals.
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Re: 5S Crank in 3S block compression question.

Postby toybota » Wed Mar 19, 2014 12:08 am

Pipedreams wrote:There are to many variables to give a good guess but with 2,2l and 20psi you should get passed 400hp.


Thanks! I know there are a ton of variables, but I don't want to go in expecting more than I'll get. 400 sounds nice.
El Coño My 1990 ST185 Canada delivered Turbo 4WD. Bought for $1000. You could say it needs some work.

'00 Focus Wagon - Soon to be gone.
'90 St185 'El Coño'
'93 St184 Parts car
'85 MA61 Supra Daily Driver
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