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What is the stock compression ratio of our D-17 motors? And are there any tricks to raise our compression

 
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d17a1 is 9:1 the a2 is 9.5:1 I believe, and dommed pistions always raise compression.

 
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the d17a1 motor is in what civics in what years ?..01-03 ??.. or am i wrong ?

 
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01-05 lx and dx

 
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a1= non vtec
a2= vtec

 
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I believe the da7a1's compression is 9.5:1 and the d17a2 is 9.9:1. Someone correct me if I'm wrong. I own an EX and I"m positive its 9.9:1. Not really a bid deal though maybe just a bit more responsive with vtech.

 
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ronald is right. i checked the manual.

 
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well i have a d17a2. and im trying to figure out the best way to boost my compression without motorwork. Ive heard of people buying thinner headgaskets, but since ours is so shitty i wouldnt do that. I am at a loss at the moment. I am hoping to be around 11:1 or 12:1 somehow. I have never done motorwork before, it isnt hard to figure out how to get things done in "theory" but the doing is what is so hard.

 
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only way your ever get 11:1 is by motor work. even if you mill the head you might get it to 10:1. sounds like you may want to look into somebody who knows what thier doing replaceing your pistons for you. then again not sure if they even make 12:1 compression pistons for our car. but with higher compression your need to completly retune the thing, probably AEM EMS is your best bet.

 
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check the manuall again VTECH isnt spelled like that its VTEC. just giving U a heads up before someone goes ballistic on U.

 
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It's also you, not U... just a heads up

 
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nice....

 
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Going with thinner gasket won't do very much to the compression ratio. Compression ratio is the ratio between the volume of bottom dead center and top dead center. I think if you are messing with the head gasket, might as well just change out the cranks and such. But if you are inexperienced, I don't think you should be messing with the engine. If you want to increase power, you might want to turbo the car. Cuz if you increase the compression ratio that much, you'll have to mess with engine management and other stuff.

 
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whatever you do DO NOT mill the head. its so fragile you will get a blown gasket within a year. find some domed pistons and build the motor. there are no shortcuts.

 
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Gearbox- how many thousands are you talking about? Why would .010" make it much more fragile? I understand the less material there, the less strengh, but what #'s are you talking about? I know that pistons are the better way to go. But if you get a warpped head, usually the machine shop will shave it. I am just curious what threshold your are talking about, .010", .015" .030" etc.

 
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you can shave it, actually they had to mill my stock head before it was swapped again. but there are guidelines to follow, and too much they will not do because it will be out of spec. the cooling passages are just way too thin already. the manual says, 0.2mm (0.008 in) is the max resurface limit. i believe mine was milled 1mm and a year later, the coolant had leaked past the gasket. fyi, compression was around 200psi per cylinder after the milling (stock is 135psi).

 
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Head shaving, and higher comp pistons

 
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thanks for the info. I am currently to pissed at the fact that my car is auto to replace the cylinders yet. Im looking to do a trans swap. Ill ask around and see if any shops will mill the head.

 
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you should find a machine shop, they can do it for you.

 
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Different subject...but still on compression. I got a new compression tester and tested the compression on a cold motor...(I would later discover that the motor should be warm) and got 205 (+ or - 1) on all four. I don't have a service manwell so can someone tell me if the above #s are acceptable...or do I need to recheck on a warm motor? What should the psi be?

 
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hey hey.. you never know.. he might mean the phone

 
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Those numbers sound good for a cold motor. there is no specification since there are so many variables when using a comp tester. You just want nice even numbers.

BUt on the subject of raising compression without changing bottom end parts. The older d series engine tricks work on our also. you can pull the middle layer out of our stock head gasket and use plenty of copper sealent spray. that will net you around .2-.3 get some flat faced valves that will be another .4 -.6 ish You don't want to go too high without true engine management. I am not a fan of milled heads but it does work also.

 
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so a milled head is a bad idea on the 1.7's^^^

 
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milled head wont last more than a year trust me i know.

 
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but yours was done incorrectly...^

 
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well it was flat, incorrectly meaning milling past factory spec. the water passage are just too delicate to do any more. eventually the increased compression will cause small leaks in the gasket.

 
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hmmm. cool cool.