Need help figuring out compression ratio
Thread Starter
Staging Lane
Joined: Nov 2011
Posts: 51
Likes: 0
From: Fredericksburg,va
Need help figuring out compression ratio Having trouble figuring compression ratio out. I have iron block 9.230 deck height bored to 3.904 100% flat top pistons compression height of 1.328 stock stroke 3.622 stock rods 6.09 ls6 cnc heads 63.5 cc chambers and .051 head basket need help horrible with math remember the aluminum ls1 block is 9.240 and this one is 9.230
Check out this site.
http://www.bgsoflex.com/auto.html
It has a bunch of calculators for automotive applications.
http://www.bgsoflex.com/auto.html
It has a bunch of calculators for automotive applications.
Now calculate your dynamic compression ratio. If it's over 8.0, you'll have some trouble with pump gas in the summer.
This is 8.35 on pump gas. Sometimes you can get away with it, and sometimes you can't. Unless you're racing, keep it closer to 8.0.
And this is what can happen with E-85 at >8.5. It detonates up under the first ring land.
And this is what can happen with E-85 at >8.5. It detonates up under the first ring land.
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Sometimes you can get away with it, and sometimes you can't. Unless you're racing, keep it closer to 8.0.
And this is what can happen with E-85 at >8.5. It detonates up under the first ring land.
I scan everytime I drive the car and I get no knock anywhere in the RPM range and I'm sitting dead on 8.8 DCR. Oh and this is on shitty winter blend no less.
That's not a "shitty tune", that's a race engine running on the edge, lap after lap. No timing retard, so max power every lap.
You can get away with a high DCR, especially if you have a electronic ignition with a knock sensor. If there's any pinging, it will retard timing to protect the engine. But then you lose power. Do your dyno run on a hot day, with coolant temps above 200* or so and see what you get.
Keeping the DCR below 8 or 8.5 will maintain max power on pump gas. Especially if you keep it cool.
You can bump that up even a little bit more if you've polished the chambers a bit, and kept your quench down to 0.035-0.040".
Play with programs like Desk Top Dyno, and see what the power difference is between 8.5 and 8.0. It's such a small amount that you wouldn't even notice on the street. On the drag strip, it would be measured in thousands of a second.
If you're racing and need every HP you can get your hands on, it's worth it to push the edge. If you're looking for a fun street car that makes good power and will last forever, it's probably not worth it to push it that hard. All depends on what your goals are, and what risks you're willing to take.
But, that's just my opinion. I could be wrong.
You can get away with a high DCR, especially if you have a electronic ignition with a knock sensor. If there's any pinging, it will retard timing to protect the engine. But then you lose power. Do your dyno run on a hot day, with coolant temps above 200* or so and see what you get.
Keeping the DCR below 8 or 8.5 will maintain max power on pump gas. Especially if you keep it cool.
You can bump that up even a little bit more if you've polished the chambers a bit, and kept your quench down to 0.035-0.040".
Play with programs like Desk Top Dyno, and see what the power difference is between 8.5 and 8.0. It's such a small amount that you wouldn't even notice on the street. On the drag strip, it would be measured in thousands of a second.
If you're racing and need every HP you can get your hands on, it's worth it to push the edge. If you're looking for a fun street car that makes good power and will last forever, it's probably not worth it to push it that hard. All depends on what your goals are, and what risks you're willing to take.
But, that's just my opinion. I could be wrong.
That's not a "shitty tune", that's a race engine running on the edge, lap after lap. No timing retard, so max power every lap.
However, I don't see the guy asking for a specific setup (aka circle track or road course engine). Thus on a regular street/strip engine where it doesn't see 7000rpm for hours on end, mid-high 8s DCR is more than doable.