compression for engine in desert states - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 9 Old 12-09-2016, 11:35 AM Thread Starter
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compression for engine in desert states

Just wondering what compression ratio some of you are running in the desert states. It will be a 347 and will be set up on meth or e85 boost will be probably 20 at most but realistically 16#'s. I didn't want to run into problems with lower 91 octane if I decide to run just on pump gas at times either. Thanks


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post #2 of 9 Old 12-10-2016, 10:34 AM
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Boost and 91 (no meth) just doesn't work, IMO, you NEED meth. My Safeguard knock detector lit up like a xmas tree with just 7psi of boost on 91 although the car made 720hp with 93. With 91/meth I was running 25psi and made 700hp+.

The CR on my car is 9.5.

If planning on pump gas/meth then a Safeguard knock detector is an absolute must, IMO. You will be amazed at what point the system actually hears knock even though there is no signs of detonation on the plugs. It will probably save you a lot of headaches before the tuning gets figured out.

ks



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post #3 of 9 Old 12-14-2016, 06:04 PM Thread Starter
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where did you get the knock sensor?

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post #4 of 9 Old 12-14-2016, 06:28 PM
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Originally Posted by Kool Rock Steady View Post
where did you get the knock sensor?
Best thing on the market and highly recommended if not running E85 or race fuel:

J&S Electronics SafeGuard Indivdual Cylinder Knock Control

ks


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post #5 of 9 Old 12-16-2016, 02:31 PM
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I use a Ford knock sensor off a 351 truck in my SB Fords.

It worked with my J&S and it works with my Holly HP just fine.

I mounted it on the block top flat edge between the transmission block plate and the rear China wall.

I can dig out a part number if you need it, but it is from a 90's pickup with 351W engine. It is a round black two-wire with a single 5/16" hole in the center for mounting. I just found a clear spot, drilled a proper size hole through the block in a clear spot, and tapped it for a 5/16" bolt. By placing the sensor there midway between banks, I get good signal from both banks and it is away from timing chain noise and all the headers and stuff.


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post #6 of 9 Old 12-16-2016, 06:29 PM
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The jury is out on compression ratio. The old school way was to run around 8 to 8.5 cr. now days people are running 10 to 10.5 cr. The newer cars are 11.3 roughly. I spoke with Freezy and duane busch about my combo and both agreed on 10 to 10.5. at lower elevations. I live at 5280 and they seemed to think I could get away with a little more. My combo comes out to 10.8. Just my 2cents

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post #7 of 9 Old 12-21-2016, 04:10 AM
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No need to be afraid of compression these days. With the amount of tuning available, people are running into the 11:1 ratio quite a bit. No need to be below 9:1.
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post #8 of 9 Old 12-22-2016, 03:39 AM
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4.6 Made 450/450 on 6# @ 10.7:1 On3 FF 70mm, A/A @ I think 12* total timing & 12.5 afr wot.

Now running 12#, upgraded wgs and bov , MP 70mm/.63 AR, Snow stage2, J&S (John is a great guy to chat with) @ 18* all on crappy AZ 91. No detonation and still waiting for a dyno slot. I think there is still a lot of power left to be found.

Good luck with your build!
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post #9 of 9 Old 12-22-2016, 06:41 PM Thread Starter
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Thanks. I think I'm leaning towards meth since I hear e85 is not popular out there. Are there any good mustang clubs or pages on Fb? the few clubs I have found are older mustangs and they charge fee's

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