What dynamic compression ratio do you run?
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From: Quebec
What dynamic compression ratio do you run?
For those who wonder what this is about, here is the link for explaination and the little program to calculate it. http://www.empirenet.com/pkelley2/DynamicCR.html
For the others, I check mine and it's 8,18:1 with 9,71 static, a 270 duration cam and 106 intake lobe centerline.
I want to be sure to run on 92 octane gas without any problem. The engine has 0,039'' quench to help.
How about your engine?? Any experience with this??
Thanks
Stephan
For the others, I check mine and it's 8,18:1 with 9,71 static, a 270 duration cam and 106 intake lobe centerline.
I want to be sure to run on 92 octane gas without any problem. The engine has 0,039'' quench to help.
How about your engine?? Any experience with this??
Thanks
Stephan
Le Mans Master
Joined: Feb 1999
Posts: 5,877
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From: Park Ridge IL
Re: What dynamic compression ratio do you run? (American Boy)
Dynamic Compression ratio: 6.00
Static Compression: 8.275
Obviously, I like nice round numbers ;).
In any case, it seems to work well on 93 octane with as much as 22 psi of boost thus far.
Static Compression: 8.275
Obviously, I like nice round numbers ;).
In any case, it seems to work well on 93 octane with as much as 22 psi of boost thus far.
Melting Slicks
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From: Sealy Texas
Cruise-In III Veteran
Re: What dynamic compression ratio do you run? (American Boy)
8.13 - I haven't installed my motor yet. I just finished putting it together last night.
I also have thermal coatings - pistons, chambers, valve faces, exhaust port and underside of valve.
I also have thermal coatings - pistons, chambers, valve faces, exhaust port and underside of valve.
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From: Quebec
Re: What dynamic compression ratio do you run? (Ken73)
Gkull:
I think that with aluminium head you can run higher compression because of the higher cooling factor. Do you have a quench on that engine?
Monty:
Without your turbos, that engine would run like crap. But that's different with 22 lbs of boost. I guess it's more like a bat out of hell. Can't wait to see your next videos.
Ken 73:
Do you have cast head. If so, that's exactly what I was looking for. Are you going to start it soon. I'd like to hear about how it run on pump gas.
Thanks
Stephan
[Modified by American Boy, 10:33 AM 2/14/2003]
I think that with aluminium head you can run higher compression because of the higher cooling factor. Do you have a quench on that engine?
Monty:
Without your turbos, that engine would run like crap. But that's different with 22 lbs of boost. I guess it's more like a bat out of hell. Can't wait to see your next videos.
Ken 73:
Do you have cast head. If so, that's exactly what I was looking for. Are you going to start it soon. I'd like to hear about how it run on pump gas.
Thanks
Stephan
[Modified by American Boy, 10:33 AM 2/14/2003]
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From: Park Ridge IL
Re: What dynamic compression ratio do you run? (American Boy)
Actually, it runs very well when not under boost, and it still make good torque and power at off idle engine speeds until it transitions to manifold pressure. We had a difficult time getting the dyno to grab below 4000 rpm but from what I could tell it was making around 440 ft lbs at 2500 rpm with low single digit negative manifold pressure.
[Modified by Monty, 9:41 AM 2/14/2003]
[Modified by Monty, 9:41 AM 2/14/2003]
Melting Slicks
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From: Sealy Texas
Cruise-In III Veteran
Re: What dynamic compression ratio do you run? (American Boy)
Stephan, my heads are cast aluminum, and are ported (very mildly.) They are just stock 1990 Corvette heads (58cc chambers, 1.94"x1.50" valves, raised D-port exhaust.) I put the TechLine CBC coating on the piston faces, the chambers, valve faces, and the entire exhaust port including the backside of the exhaust valve to cut down on heat being transferred into the metal.
My car should be running in a few weeks, but I still have a lot ahead of me (tuning the fuel injection, etc.)
My car should be running in a few weeks, but I still have a lot ahead of me (tuning the fuel injection, etc.)
Team Owner
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: What dynamic compression ratio do you run? (American Boy)
Do you have a quench on that engine? That's a difficult question to answer as worded! Now if you ask how big is my gap from the pist top to the head. which is called the quench area I would tell you that my pistons are .004 below the block deck and I'm using a .038 compressed size head gasket. So I have @ .042 quench. 10.84 static C/R
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From: Quebec
Re: What dynamic compression ratio do you run? (Monty)
Monty:
Well, I still have a lot to learn on engine dynamics. I hope that I get what I'm after with my engine.
Ken 73:
Aluminium head! They have great advantages over cast but my budget would'n't allow me to put those. I got some used vortec for almost nothing so the choice wasn't difficult. Good luck with your engine.
Gkull:
Sorry for the bad english, I speak french all day so sometime the words are not align correctly. Anyway, it's about the same quench area that my engine will have (0,039''). I guess that I'm gonna be on the line as far as 92 octane and full advance.
Anybody run Nitrous oxyde with these dynamic compression ratio? (8-8.5)
Stephan
[Modified by American Boy, 1:34 PM 2/14/2003]
Well, I still have a lot to learn on engine dynamics. I hope that I get what I'm after with my engine.
Ken 73:
Aluminium head! They have great advantages over cast but my budget would'n't allow me to put those. I got some used vortec for almost nothing so the choice wasn't difficult. Good luck with your engine.
Gkull:
Sorry for the bad english, I speak french all day so sometime the words are not align correctly. Anyway, it's about the same quench area that my engine will have (0,039''). I guess that I'm gonna be on the line as far as 92 octane and full advance.
Anybody run Nitrous oxyde with these dynamic compression ratio? (8-8.5)
Stephan
[Modified by American Boy, 1:34 PM 2/14/2003]
Drifting
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From: Reno nevada
Re: What dynamic compression ratio do you run? (American Boy)
I have friends that are into Nitrous and drag racing. They have race gas only motors. Your compression ratio doesn't matter, if it runs fine with 12.5 compression and 100 octane or if you have 10.5 and it runs fine on 91 octane. It relies on pulling timing out as the N2O comes on.
Melting Slicks
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From: Sealy Texas
Cruise-In III Veteran
Re: What dynamic compression ratio do you run? (American Boy)
Stephan, mine are actually a set of later-model Corvette heads I picked up from a forum member here for a really good price. They are used, but I paid about as much as you did for the Vortecs. Of course, I've taken them to the machine shop a couple of times, but they were still much cheaper than a set of new ones. I did the ceramic coating myself, a bottle of the stuff only cost me $25.
As for my quench area, my block is totally stock; I measured and I have .025" deck-to-piston clearance and a .039" thick gasket. My pistons are flat-tops with a 3cc single valve relief.
As for my quench area, my block is totally stock; I measured and I have .025" deck-to-piston clearance and a .039" thick gasket. My pistons are flat-tops with a 3cc single valve relief.
Drifting
Joined: Apr 2002
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From: Stockton Ca
Re: What dynamic compression ratio do you run? (American Boy)
I'm also interested. I have a scr of 10.25. I run a CC HR 270-276 218-224 w/1.6rrs. The 6" rod helps w/detonation. I run 91 all year w/o problems on hottest days. Dual spals keep temps below 200. Can anyone help w/caculations?
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From: Quebec
Re: What dynamic compression ratio do you run? (Ken73)
Ken73:
The forum is a great place to get good deals on part. Aluminium head is the way to go. I do like the flow rating and chamber design of the vortec though.
Taijutsu:
The link on the first reply provide a software that calculate the DCR. I ran the calculation with the spec you provide and it would be 8.40:1. Do you run aluminium head? You have the same cams as I plan to put in my engine. How do you like it? Does the idle have any lope in it? I want to build a sleeper so the idle is important to me. How about low end torque and h.p.?
Thanks
Stephan
The forum is a great place to get good deals on part. Aluminium head is the way to go. I do like the flow rating and chamber design of the vortec though.
Taijutsu:
The link on the first reply provide a software that calculate the DCR. I ran the calculation with the spec you provide and it would be 8.40:1. Do you run aluminium head? You have the same cams as I plan to put in my engine. How do you like it? Does the idle have any lope in it? I want to build a sleeper so the idle is important to me. How about low end torque and h.p.?
Thanks
Stephan
Drifting
Joined: Apr 2002
Posts: 1,736
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From: Stockton Ca
Re: What dynamic compression ratio do you run? (American Boy)
Thanks for the caculations. I believe that 8.4 is about right for this cam? I have TFS heads bowl ported. The cam is restricted by the stk ex man. This will change after next smog. I couldn't be happier w/performance. This pulls like a BB. No lope mega sleeper. Right now carb is my problem. The 750VS Demon broke its idle circut and flooded fuel into oil. I haven't sent it back yet for the second time. The first was bad enough. I just want my $ refunded and I know they will want to keep repairing it. This on and off not to mention tuning expenses are killing me. If they refuse to refund for their POS I will start my "DEMON SUCKS, BUY A HOLLY campaign". Hopefully the bad press will help them to refund my $. The Demon tech rep lectured me like a 5 yr old that THEIR 750 was too big for my engine! After their custom tuning my engine was WORSE than out of the box! Thanks for the support! :banghead:
