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Old 02-22-2015, 08:16 PM   #1
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Default Max Compression Easily Attainable for NA on e85

Hi,

What is the max compression ratio that is easily attainable on a naturally aspirated motor? For use with e85 on a dedicated track car.

By easily attainable I mean off the shelf or custom but existing (& ideally 85.5mm) pistons, and sensible amounts of head/block skimming that don't cause other issues.

Cheers.
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Old 02-25-2015, 12:01 AM   #2
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Anyone? Anyone?...Bueller???
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Old 02-25-2015, 12:08 AM   #3
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I'm not sure if I've seen any over 11:1. This guy is running11:1
on corn juice and boost.
https://www.miataturbo.net/build-thr...-thread-80256/
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Old 02-25-2015, 12:42 AM   #4
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According to this guy, you can shave the head roughly .080" with a stock 2001+ bottom end and a BP4W head. Internet wisdom for head shaving says that should be roughly 12:1.

My 172whp N/A Engine. Stock bottom end. No Porting. - MX-5 Miata Forum

I'm about to drop a .060" shaved VVT head in my car with E85, but I won't have any dyno results for a month or two.
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Old 02-25-2015, 02:46 AM   #5
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As much as you can fit in there. Id probably call up weisco and have them make you some 12:1 slugs and then clay it and see how much you can take off the head with the cams you will use. If i had to put a number on it, you'd probably end up around 13:1. It gets pretty tight in there with high lift cams.

Too much work? Here are easy off the shelf pistons

TMD CCP0001 TMD Racing Forged Aluminum Piston. from the EPMiata.Com Online Store!
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Old 02-25-2015, 03:11 AM   #6
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Get some Supertech piston XX ring combo 11:1 from 949 racing and shave the head to get 12:1 or really aggressive and almost 13:1
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Old 02-26-2015, 12:42 AM   #7
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Quote:
Originally Posted by joyrider View Post
Get some Supertech piston XX ring combo 11:1 from 949 racing and shave the head to get 12:1 or really aggressive and almost 13:1
Thanks for the replies and links.

It would be nice to get to 13:1.

At what point are there issues with timing? Physical clearance will be easy enough to clay and measure before skimming the head.
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Old 02-26-2015, 02:50 AM   #8
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Quote:
Originally Posted by Neddy View Post
Thanks for the replies and links.

It would be nice to get to 13:1.

At what point are there issues with timing? Physical clearance will be easy enough to clay and measure before skimming the head.
Don't know, but which computer do you plan on running ?
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Old 03-02-2015, 04:17 AM   #9
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11.2:1

23PSI





Dann
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Old 03-23-2015, 01:51 AM   #10
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Quote:
Originally Posted by joyrider View Post
Don't know, but which computer do you plan on running ?
MS, but to clarify when I said issues with timing, I was talking about the physical effect on camshaft timing from a big head skim, not ignition timing.
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Old 03-31-2015, 02:53 PM   #11
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@Neddy wich Motor do you have ?
Does it make sence to go 13:1 on a 94 1.8 stock Engine Na Miata exept skimming ....I guess no....
Depends on your entire Setup if such cr ratio make sence or not
Sorry my english isn't the best ,so if i understood something wrong please tell me
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Old 03-31-2015, 02:59 PM   #12
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Wossner makes 12:1 pistons.
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Old 03-31-2015, 10:26 PM   #13
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Quote:
Originally Posted by MiataGarage View Post
@Neddy wich Motor do you have ?
Does it make sence to go 13:1 on a 94 1.8 stock Engine Na Miata exept skimming ....I guess no....
Depends on your entire Setup if such cr ratio make sence or not
Sorry my english isn't the best ,so if i understood something wrong please tell me
Does it make sense to go for max easily attainable compression on a track only engine build?

Keeping in mind e85 is readily available, to me it makes perfect sense
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Old 03-31-2015, 10:28 PM   #14
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Quote:
Originally Posted by concealer404 View Post
Wossner makes 12:1 pistons.
Cheers. Have ordered some 85.5 supertech 11:1.
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