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Old 09-03-2019, 09:08 AM   #1
Jade_Accord
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Post Planning a rebuild. Need info on compression ratios and tuning.

I'm planning on rebuilding my old and tired 280,00 mile F22a6 and I would like to go and refresh the cylinders and bore them to 86mm Just to make sure everything is fresh and good to go for another 300,000.

Now I've been eyeing the Bisimoto 9:1 and 9.1:1 Compression ratio pistons for quite some time now and due to the bump from 8.8:1CR to 9:1CR I was wondering if I'll need a tune. I've scoured the internet, dug through all kinds of forums from subarus to civics but still no solid answer. I even made this account just so I can get more insight.

I live in Califronia so almost any performance mod is seen as criminal so thats why I'm reluctant to tune. I could manage with a bit of adjusting the distributor if I must though. If its one thing I keep seeing in many other forums is "Just do it right the first time". Well its a little hard to do it right if its frowned upon by the state.

tl;dr - I live in california. Gonna rebuild with 1mm larger pistons. Larger piston = slightly higher comperssion ratio. ratio from 8.8:1 to 9.1:1. Will I need a tune? Cali sucks for mods. Reluctant to tune.

Thanks all in Advance.
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Old 09-03-2019, 11:51 AM   #2
Crankshaft
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For performance the .2 in compression is gonna yield you about nothing, i would suggest that if you are not going to tune just to get the 85.5 pistons from ebay and run with those as you dont have to pay the extra $400 specially if you are not gonna boost or even tune the engine. In your circumstances anything you do without a tune is pretty much like shooting steroids without working out, does this mean the car will implode? no but generally $499 pistons are used when building upon is the goal, for a simple build you dont have to spend that money.
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Old 09-03-2019, 10:25 PM   #3
Jarrett
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Don't worry about the difference. The main benefit from that package is the longer rod used increasing the rod/stroke ratio of the F22 engine. This will allow the engine to rev more freely, and to reach a higher redline (with supporting valvetrain).

Bisi, however, doesn't make these parts, and never did. They are pistons designed for a stroker 4G63 ordered in 86mm bore. The compression height is 28.75mm if purchased for the 100mm stroke, and can be had with a multitude of compression options. Just start searching eBay for "4G63 stroker pistons" and read enough item descriptions until you find the proper compression height.

The shorter compression height of that piston is what allows the the 143mm H22A rod to be used. Luckily, this rod is dimensionally identical to an F22A/H23A1 rod in every way except for the length. The H22A rod is 1.5mm longer. Bisi just used cheap "Chinesium" rods packaged with those shelf pistons and called it a day. I suggest you buy the two separately and save bit of money. Not to mention tailor the compression to what you'd like to have.

To determine the ultimate compression ratio, only use the dome/dish volume in the listings you look at. Ignore any ratios. Then use the zealautowerks compression calculator to determine the final static compression ratio.

https://www.zealautowerks.com/hfseries.html
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Old 09-27-2019, 05:36 AM   #4
Bailey_CatDaddy
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Quote:
Originally Posted by Jarrett View Post
Don't worry about the difference. The main benefit from that package is the longer rod used increasing the rod/stroke ratio of the F22 engine. This will allow the engine to rev more freely, and to reach a higher redline (with supporting valvetrain).

Bisi, however, doesn't make these parts, and never did. They are pistons designed for a stroker 4G63 ordered in 86mm bore. The compression height is 28.75mm if purchased for the 100mm stroke, and can be had with a multitude of compression options. Just start searching eBay for "4G63 stroker pistons" and read enough item descriptions until you find the proper compression height.

The shorter compression height of that piston is what allows the the 143mm H22A rod to be used. Luckily, this rod is dimensionally identical to an F22A/H23A1 rod in every way except for the length. The H22A rod is 1.5mm longer. Bisi just used cheap "Chinesium" rods packaged with those shelf pistons and called it a day. I suggest you buy the two separately and save bit of money. Not to mention tailor the compression to what you'd like to have.

To determine the ultimate compression ratio, only use the dome/dish volume in the listings you look at. Ignore any ratios. Then use the zealautowerks compression calculator to determine the final static compression ratio.

https://www.zealautowerks.com/hfseries.html

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