Question for high compression guys
Thread Starter
Joined: Nov 2001
Posts: 10,060
Likes: 33
From: Canton, GA
Question for high compression guys 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?
TECH Junkie
Joined: Nov 2001
Posts: 3,987
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From: Melbourne, FL
Re: Question for high compression guys 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.
Re: Question for high compression guys 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.
TECH Junkie
Joined: Nov 2001
Posts: 3,987
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From: Melbourne, FL
Re: Question for high compression guys </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.
Re: Question for high compression guys 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!!
Thread Starter
Joined: Nov 2001
Posts: 10,060
Likes: 33
From: Canton, GA
Re: Question for high compression guys 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" />
Todd
Todd
Joined: Nov 2001
Posts: 8,484
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From: Cecil County Raceway!!!
Re: Question for high compression guys 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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Re: Question for high compression guys 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..
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TECH Senior Member
Joined: Nov 2001
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Re: Question for high compression guys 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
Re: Question for high compression guys The best way to find out if it is really detonation.. Try race gas and go out and run her.. If no KR. Then you will no it was not false knock..