 compression ratios? 1.7L motor |
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| brer |
  Apr 20 2006, 02:30 PM
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#1
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Advanced Member  Group: Members Posts: 2,555 Joined: 10-March 05 From: san diego Member No.: 3,736 Region Association: None  |
so whats the highest ratio you can run on RUG ?
stock 1.7L motor I keep hearing about the new fuel mixtures and knocking... but i'd like to up the ratio to the most possible when i put the heads back on. 8.2:1 8.5:1 9.0:1 |
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| SirAndy |
Apr 20 2006, 02:36 PM
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#2
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Resident German Group: Admin Posts: 41,623 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(brer @ Apr 20 2006, 01:30 PM)  so whats the highest ratio you can run on RUG ? stock 1.7L motor I keep hearing about the new fuel mixtures and knocking... but i'd like to up the ratio to the most possible when i put the heads back on. 9.0:1 i ran 9:1 on my 2.0L on pump gas with no problem ... i don't see why it wouldn't work in a 1.7L ... (IMG:style_emoticons/default/smile.gif) Andy |
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| brer |
Apr 20 2006, 02:42 PM
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#3
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Advanced Member Group: Members Posts: 2,555 Joined: 10-March 05 From: san diego Member No.: 3,736 Region Association: None |
what brand did you run? octane? did you use regular? I have flattop pistons. would it be necessary to run domed to hit 9:1? |
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| SirAndy |
Apr 20 2006, 03:08 PM
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#4
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Resident German Group: Admin Posts: 41,623 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(brer @ Apr 20 2006, 01:42 PM) what brand did you run? octane? did you use regular? I have flattop pistons. would it be necessary to run domed to hit 9:1? wow, slow down .. (IMG:style_emoticons/default/biggrin.gif) brand: any. whatever was cheap. octane/regular: usually mix 50/50 of premium and regular pistons: euro P/Cs, not domed. (IMG:style_emoticons/default/smile.gif) Andy |
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| brer |
Apr 20 2006, 03:17 PM
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#5
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Advanced Member Group: Members Posts: 2,555 Joined: 10-March 05 From: san diego Member No.: 3,736 Region Association: None |
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| brer |
Apr 20 2006, 03:46 PM
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#6
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Advanced Member Group: Members Posts: 2,555 Joined: 10-March 05 From: san diego Member No.: 3,736 Region Association: None |
no, but seriously,
I realize i'm not going to get tons of power out of the 1.7, and while the high compression sounds "neat" I'm wondering what the most efficient rate would be. is going to 9:1 going to be worth 2 or 3 hp? or are the benefits of longevity that a lower compression motor can give bought at the cost of 4 hp. of course the kid in me says 9:1. whats the intelligent choice? I'm not sure. |
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| 914forme |
Apr 20 2006, 03:57 PM
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#7
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Times a wastin', get wrenchin'! Group: Members Posts: 3,896 Joined: 24-July 04 From: Dayton, Ohio Member No.: 2,388 Region Association: None 
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The kid in me handsdown
If your planning on driving it for 100K miles the 9.0 compresion might make it drop to 90K miles. 4 extra HP will make up for ht grin factor, but then. Toss a turbo on it and make an extra 50 hp or so. See the kid in me keeps winning. |
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| brer |
Apr 20 2006, 04:15 PM
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#8
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Advanced Member Group: Members Posts: 2,555 Joined: 10-March 05 From: san diego Member No.: 3,736 Region Association: None |
me thinks i agree. (IMG:style_emoticons/default/biggrin.gif)
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| Dave_Darling |
Apr 20 2006, 09:05 PM
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#9
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914 Idiot Group: Members Posts: 14,982 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California
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QUOTE(SirAndy @ Apr 20 2006, 02:08 PM) octane/regular: usually mix 50/50 of premium and regular pistons: euro P/Cs, not domed. Unless you flycut the heads, the Euro P&Cs "should" give you 8:1 compression, not 9:1. That's quite a difference... Factory spec for the 8:1 2.0 motors is to run ~89 octane. Stock 1.7s would be 8.2:1, and most of them are spec'ed for super-grade (91 octane) fuel. Though the later 1.7s seem to have been spec'ed for regular (87) stuff, while making the same power and having the same compression. (???) Compression ratio is the sort of thing you can't easily change your mind about once you've made the decision. I would tend to go more on the conservative side--I'd probably stay at ~8.6:1 or less, because trying to find higher octane than 91 in CA is quite difficult. --DD |
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| SirAndy |
Apr 20 2006, 10:37 PM
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#10
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Resident German Group: Admin Posts: 41,623 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(Dave_Darling @ Apr 20 2006, 08:05 PM) Unless you flycut the heads, the Euro P&Cs "should" give you 8:1 compression, not 9:1. yes, headwork was done. 9:1 on pumpgas, as i said usually mix of high and low 50/50 ... (IMG:style_emoticons/default/smile.gif) Andy |
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