Can you run turbos with a 10.5:1 compression.. - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 23 Old 05-03-2003, 12:52 PM Thread Starter
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Can you run turbos with a 10.5:1 compression..

engine? if so, what kind of consequences would I face (in terms of reduced boost timing).

Please help, I have a flat top 347 built for higher compression.

This would be mated with an incon like kit and smallish turbos.

Guy

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post #2 of 23 Old 05-03-2003, 04:27 PM
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I would say you could likely run about 4.5-5 lbs of boost max on pump gas. The LS1 guys are at 10.3:1 and that's all the boost they can see without changing expensive stuff.

Just keep C16 in the tank and turn it up to 10 lbs. Not sure the consequenses of that, but it sounds fun.


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post #3 of 23 Old 05-04-2003, 03:19 AM
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Not totally true...my freind here in town w/a TC'd LS1 will run as much as 10lbs sometimes...on the street he usually runs 3, 6, or 9 though...he's still running stock internals, heads and cam. He's had the car that way for about 7-8 months now and no problems. It will be down in a week or two to swap in a 9.0 comp. motor...I'm really intersted to see how the stock pistons and rings are gonna look.

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post #4 of 23 Old 05-04-2003, 02:28 PM Thread Starter
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That sounds intriguing, I have been working on the turbo kit for a while, it sounds like too much fun to run around with 96 in the tank and 6-8 lbs boost..

any one else?

BTW, I was thinking about the conversion between my current set up @ ~9.5:1 and 10 kennebell to 10.5:1 forged aluminum pistons :

9.5:1 compression with 10 lbs boost (or 24.7psi) is theoretically equal to:
10.5:1 compression with 7.5 lbs boost but with better bottom end torque due to the cubes and higher compression.

Am I on the right track?
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post #5 of 23 Old 05-04-2003, 10:37 PM
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Quote:
[i]9.5:1 compression with 10 lbs boost (or 24.7psi) is theoretically equal to:
10.5:1 compression with 7.5 lbs boost but with better bottom end torque due to the cubes and higher compression.

Am I on the right track? [/B]
Your on the right track, but wrong compression numbers according to my book.. 9.5:1 compression with 10 psi=16.0:1 static compression ratio in the end. 10.5:1 comp with 7.5 boost=approx 15.5:1 static. Do your own math and think of what octane you think you can run with those numbers.
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post #6 of 23 Old 05-05-2003, 01:17 AM Thread Starter
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I did round down on that last boost number. I think its doable, but I have access to 110 leaded to supplement my mix, but that smells pricey..

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post #7 of 23 Old 05-05-2003, 08:57 AM
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I ran 12lbs of boost into a 10.5:1 motor via a B-trim years ago. Just dumped a lot of fuel in it and took out a lot of time, this was long before custom chips and such. It worked pretty good, but had a TON of useless low end torque and especially for the suspension I had. If I were to do it again, I'd run half the boost or at least an intercooler of some sort

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post #8 of 23 Old 05-05-2003, 11:10 AM Thread Starter
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Aaron,

I always value your input. I do have the tweecer, a WB and other help, but I am trying to confirm if its worth the headache of trying it. looks like i am working toward putting twins on.

I think I would be happy with 6lbs intercooled boost... lets see.
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post #9 of 23 Old 05-05-2003, 11:57 AM
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I think it will be an unhealthy low end torque monster with that many cubes, that compression and twins. But I do know it can be done and not blow up, just has to be tuned good for obvious reasons. I think cooling the motor down might be a problem though.

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post #10 of 23 Old 05-05-2003, 07:33 PM
 
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Quote:
Originally posted by snipe656
I think it will be an unhealthy low end torque monster with that many cubes, that compression and twins. But I do know it can be done and not blow up, just has to be tuned good for obvious reasons. I think cooling the motor down might be a problem though.
What do you mean by this? I'm trying to figure out that happy medium between quick throttle response and lots of boost on a '98 Cobra. How would this be unhealthy? I'm also attempting to build a turbo monster but I don't want to run low boost and sacrifice good throttle response on NA applications...meaning I don't want to 'get on it' just to get going.

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post #11 of 23 Old 05-05-2003, 08:56 PM Thread Starter
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Aaron,

I can tune out much of the LOW end tire shredding with a good cam, dont you think?
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post #12 of 23 Old 05-05-2003, 10:41 PM
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Yeah, you probably could do it via a custom cam, never really thought about trying that method.

What I meant by that is a 347 with that type of compression is already kind of torquey to most people. A 302 with stock compression is pretty torquey to most people. Mix the two and you are going to get a TON of lower end torque, so much that it might be a tad hard to actually use any of it, especially on the street. In regards to cooling, the higher comp motors tend to run hotter as is, turbos add a bit of underhood heat, then a IC tends to hamper the cooling system some, so all those mixed together and it will take a very well done cooling system to keep up with things.

Honestly with a Cobra, I'd turbo it and keep the motor around stock compression. I would think you are not going to run into your fears unless you go overboard on the turbo sizing and low compression.

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post #13 of 23 Old 05-10-2003, 04:58 AM
 
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lol my friend wants to run 10 psi on his 10.5:1 408 stroker, lol
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post #14 of 23 Old 05-10-2003, 02:39 PM Thread Starter
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tell him we will be right behind him
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post #15 of 23 Old 05-10-2003, 03:01 PM
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yeah, way behind him

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post #16 of 23 Old 05-10-2003, 03:13 PM Thread Starter
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Aaron, remember to bring your Digicam!
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post #17 of 23 Old 05-10-2003, 03:32 PM
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Yeah that and a case of beer for after the "fireworks"

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post #18 of 23 Old 05-10-2003, 03:33 PM Thread Starter
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I cant wait until I get to see what it feels like with a 347....
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post #19 of 23 Old 05-10-2003, 06:31 PM
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It was crazy torquey in the low end on my car and that was just with a 302 and a lowly Vorturd. You could just ease into boost at maybe 1/4 throttle cruising down the street and it would start to get "squirally" But then again some of that had to do with suspension.

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post #20 of 23 Old 05-10-2003, 06:48 PM Thread Starter
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you might have forgotten that I currently drive a KB car... I wonder if it will be like that? cant wait cant WAIT

I have never been in a centrifugal car... ... bah!
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post #21 of 23 Old 05-10-2003, 10:59 PM
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Nope, did not, but also have never driven a KB car.

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post #22 of 23 Old 05-11-2003, 08:53 PM
 
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I think anything over 10:1 will recquire wing nuts on the head studs. It just sounds like a recipe for abundant head gasket replacement. Good luck with it.
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post #23 of 23 Old 05-11-2003, 10:37 PM Thread Starter
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well, I have been running 9.5:1 compression with my aluminum head combo and 10Psi Kb boost (oringed with the HG's). I have used both elcheapo felpros to the 1006 with the locwire in them... neither has had any problems with the HG's getting tempermental or blowing, despite detonation that has ruined my ring seal....

I have to admit, tho, that I am a bit more cautious going into this ..
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