RacerX Posted October 9, 2006 Share Posted October 9, 2006 I was reading engine articles on NA engines and I've noticed that a couple of the high performance engines were running 11.0:1 or 11.5:1 compression ratios. This was the new Z06 Corvette LS7 engine with 11.0:1 while the 2006 BMW M3 is running 11.5:1 CR. My question is that it's obvious these cars are able to run on Premium Pump Gas. With the technology of stand-alone computer systems that are now available for use when doing engine swaps - do you feel you could get away building a high compression engine for your next engine swap. Obvious there is much more power to be had. With this in mind, do you feel 12.0:1 CR is streetable? I remember in the late 60's when guys were running 13.0:1 on pump gas - but back then the octane was much higher than todays pump gas. Your thoughts please. thanks, RacerX Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 9, 2006 Share Posted October 9, 2006 Check this out... http://www.kemcooil.com/product_info.php?pId=61 Run whatever CR you want:flamedevi Quote Link to comment Share on other sites More sharing options...
mario_82_ZXT Posted October 9, 2006 Share Posted October 9, 2006 It's all in the tuning. I bet that if you had to put something less then premium in those vehicles the computer would recognize that and adjust accordingly. Even the 300zxtt boosts less when ran with lower grade gas, and the 350z pulls timing. There are a few Zs running around with about 12.:1 or higher. Mario Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 9, 2006 Share Posted October 9, 2006 RacerX Seriously... check out that link to the fuel additive. It has tetra ehtyl lead and for just $5 per 10 galons of pump gas, you can bump your octane by 16 POINTS. It's poisonous... just be CAREFUL. If you only want to bump your octane 5 points, it will only cost you $1.80 per 10 galons!! Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 9, 2006 Share Posted October 9, 2006 If you travel 100+ miles from home often, carrying extra additive might be necessary. Regarding carrying spare additive in an ice chest... I doubt you'd have to do that but I'm no expert. Quote Link to comment Share on other sites More sharing options...
strotter Posted October 9, 2006 Share Posted October 9, 2006 Aluminum heads - which both those motors feature - can take at least 1 point higher than iron. I'm sure somebody will pipe in here to clarify, but I understand heat dissipation, as well as heat distribution, make much of the difference for Al. Another point of importance, w/r/t detonation, is the dynamic compression ratio. There has been some talk about it on the forums here, but the gist is that the *actual, running* compression is always lower than the calculated number to the valves' being open during part of the compression stroke, and modified somewhat by inertia effects in the working fluid(s). So you can have a radical c/r calculated for static, but see a much, much lower actual number in operation. Grumpy is the one that clued me into this one. It's not hard to guesstimate, you just use the ratio of the volume at the valve closing point to volume at TDC, instead of from BDC to TDC. Quote Link to comment Share on other sites More sharing options...
chuckmorgan79 Posted October 10, 2006 Share Posted October 10, 2006 I'm not sure how this applies, but my 2005 Honda 600rr had a compression ratio of 12:1 and the manual recommended 87 octane. I never understood how they pulled that off. My RC-51 (1000cc Vtwin) requires premium and the CR is well below the 600, maybe 10.8:1. Does it have something to do with the cc's per cylinder? chuck Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 10, 2006 Share Posted October 10, 2006 chuckmorgan79 Dunno... maybe VVT and ECU management:icon43: Quote Link to comment Share on other sites More sharing options...
chuckmorgan79 Posted October 10, 2006 Share Posted October 10, 2006 variable valve timing? they don't have that. i could see the ECU having something to do with it though. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 11, 2006 Share Posted October 11, 2006 Oops... I've shown my ignorance again:redface: But yes, the ECU is preventing the ping. I'd run the highest octane I could get with that CR. Quote Link to comment Share on other sites More sharing options...
Gollum Posted October 13, 2006 Share Posted October 13, 2006 Yea, I think the earlier S2000 hondas had 12.5:1 I could be wrong though. I don't claim to know what it really is, but I remember nearly falling to the foor when I first found out how high it was on a production vehicle. Quote Link to comment Share on other sites More sharing options...
Gollum Posted October 13, 2006 Share Posted October 13, 2006 that's the spec on the 2.2 liter. Was it higher on the earlier 2.0 liter motors? Quote Link to comment Share on other sites More sharing options...
Gollum Posted October 13, 2006 Share Posted October 13, 2006 Thanks for the clarification. I thuoght it was higher though, oh well Quote Link to comment Share on other sites More sharing options...
dscott@red3 Posted October 13, 2006 Share Posted October 13, 2006 It's all in the tuning. I bet that if you had to put something less then premium in those vehicles the computer would recognize that and adjust accordingly. Even the 300zxtt boosts less when ran with lower grade gas, and the 350z pulls timing. There are a few Zs running around with about 12.:1 or higher. Mario And this is why most 350z owners(like myself) are a littled p'd at the VQ. The engine is a little to smart. Quote Link to comment Share on other sites More sharing options...
darthpaul Posted October 15, 2006 Share Posted October 15, 2006 The compression ratio of the new BMW v-10(s85) in the M5 and M6 is 12.0:1. It has very precise fuel and spark mapping(duh!) and a unique ignition system that uses the spark plug to measure in cylinder ionisation to determine combustion quality and detonation. It will run perfectly on cali. 89 octane, at a slightly lower maximum power I'm sure. It will still try to spin the tires at 70 m.p.h in third gear from 7000 r.p.m. to 8200 r.p.m. Quote Link to comment Share on other sites More sharing options...
sweetleaf Posted November 10, 2006 Share Posted November 10, 2006 High pressure direct injection is sweet. The fuel atomizes much better, giving better MPG and power at the same time. Quote Link to comment Share on other sites More sharing options...
Careless Posted November 10, 2006 Share Posted November 10, 2006 that's pretty nuts for a factory luxury automobile Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted November 11, 2006 Share Posted November 11, 2006 You don't need a stand alone computer to automatically adjust for low octane gas. All modern FI engine use knock sensors to automatically retard timing should you gt bad gas. My geo had that back in the 90's. As for direct injection, that is getting much more common, even for domestic econoboxes. Detonation is not possible because there is no fuel in the compression chamber until it is ready to fire the spark. I think there are still octane limits on direct injection motors. I know the Germans used it in there aircraft back in WWII. I would stay the F away from anything with concentrated TEL. Can't believe that is even legal to sell. Not to mention what it will do to your catalytic converter. Quote Link to comment Share on other sites More sharing options...
Guest beebo Posted January 20, 2007 Share Posted January 20, 2007 the 2007 kawasaki zx6r has a 13.9 cr. that is rediculous Quote Link to comment Share on other sites More sharing options...
Brett6485 Posted January 23, 2007 Share Posted January 23, 2007 Internal ceramic coating goes a long way, we've ran 11:1 compression on a completely iron motor on 91 octane with out issue. Basic Fuel injection, no knock sensors, just a good tune and a close eye on the wideband. Quote Link to comment Share on other sites More sharing options...
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