Question for high compression guys
#1
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I just recently wnet up to about 11.1:1 CR. Today, I made a short burst with ATAP and saw a little KR (1-2 range). This was with 94 octane gas.
I remembered that my timing was still set to 28 degrees from when I was running lower compression. I retuned to 26 degrees, but didn't ATAP yet.
Was wondering how much total timing you guys are running with higher compression setups. I remember reading the post about an LS6 vette making good power with only 22 degrees, so I'm guessing some of you are "tuned down" with higher CRs?
I remembered that my timing was still set to 28 degrees from when I was running lower compression. I retuned to 26 degrees, but didn't ATAP yet.
Was wondering how much total timing you guys are running with higher compression setups. I remember reading the post about an LS6 vette making good power with only 22 degrees, so I'm guessing some of you are "tuned down" with higher CRs?
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I've been experimenting a little with timing advance, and haven't really seen much change ET/dyno wise between 23-31 degrees of advance. A little more timing in the midrange seems to help launch the car, but I don't have enough hard data to back that up. Right now I'm running 29deg @ WOT, ~13.2:1 compression, and nothing but Sunoco Purple or VP 110 race fuel.
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We typically run 22-24 degrees of advance with our cam/head setups that have a compression ratio of 11.4:1. There is usually isn't any detonation at all except on maybe a real hot night at the track. 29 degrees is definately too much timing for that compression. Have you dyno'ed the car and checked the A/F ratio? Maybe the car might be a slight bit lean as well.
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</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 9D9LS:
<strong>We typically run 22-24 degrees of advance with our cam/head setups that have a compression ratio of 11.4:1. There is usually isn't any detonation at all except on maybe a real hot night at the track. 29 degrees is definately too much timing for that compression. Have you dyno'ed the car and checked the A/F ratio? Maybe the car might be a slight bit lean as well.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Me? The A/F ratio is right on the money on the dyno (12.7-12.8), but the car still acts a little rich at the track.
I plan to keep playing with advance and see what works out best.
<strong>We typically run 22-24 degrees of advance with our cam/head setups that have a compression ratio of 11.4:1. There is usually isn't any detonation at all except on maybe a real hot night at the track. 29 degrees is definately too much timing for that compression. Have you dyno'ed the car and checked the A/F ratio? Maybe the car might be a slight bit lean as well.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Me? The A/F ratio is right on the money on the dyno (12.7-12.8), but the car still acts a little rich at the track.
I plan to keep playing with advance and see what works out best.
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12.7-12.8 is still to rich for these motors. We always find the best power at a leaner 13.2:1. These engines are highly efficient with there "fast burn" combustion chamber design. Old school power was always made at the "ideal" 12.8 but these motors are a whole new animal. Think about how efficient they really are. We are make 520 HP at the flywheel with cam/heads utilizing the stock 346 ci. Thats 1.5 hp per cubic inch!! Lean and mean!!
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Haven't gotten her on the dyno yet, but the O2s were consistently about .920 through the street burst. Think I will try 25 degrees timing, unless I throw in some real good gas like George <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
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I've been at 26-28 with my 11.8:1 compression without any problem but I really haven't given it hell in 4th yet on 93 octane.
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#8
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It depends on the temp outside.. It was blazing yesterday.. I autotapped her and intake temp was showing almost 140 degrees and it was about 98 to 100 out. I was getting 28.5 degrees of timing and I saw 1 to 2 KR's right at 6000rpm.. Made another run when it was a little cooler out and the car showed no KR.. The reason I am going with a bigger cam is to bleed off some more compression..
#9
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I am running 27 degrees of advance with no problems on 94 with a AF of 12.4:1
Cheers,
Chris
ps- If/when I change cams I will likely bump it up to 28 degrees and see how that works
Cheers,
Chris
ps- If/when I change cams I will likely bump it up to 28 degrees and see how that works