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496 CMI Sport Tube dyno test

Old 06-02-2009, 10:40 AM
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Default 496 CMI Sport Tube dyno test

I finally got a chance to dyno a set of CMI headers on the prop shaft dyno. These were installed on a twin engine Formula with captains call exhaust. The install was a lot of work. We had to cut the diverters significantly to get it to fit. The kit also included brackets to relocate the pcm, fuel pump module and oil filter. That was all pretty straight forward. The hatch lift didn't clear the headers and needed to be relocated. I'm attaching the dyno sheets. They were run using standard correction method.
Attached Thumbnails 496 CMI Sport Tube dyno test-stock-496-ho-.jpg   496 CMI Sport Tube dyno test-stock-496-ho-cmi-.jpg  
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Old 06-02-2009, 11:01 AM
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Originally Posted by bobl
I finally got a chance to dyno a set of CMI headers on the prop shaft dyno. These were installed on a twin engine Formula with captains call exhaust. The install was a lot of work. We had to cut the diverters significantly to get it to fit. The kit also included brackets to relocate the pcm, fuel pump module and oil filter. That was all pretty straight forward. The hatch lift didn't clear the headers and needed to be relocated. I'm attaching the dyno sheets. They were run using standard correction method.
You picked up 30HP+-
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Old 06-02-2009, 05:32 PM
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Originally Posted by bobl
I finally got a chance to dyno a set of CMI headers on the prop shaft dyno. These were installed on a twin engine Formula with captains call exhaust. The install was a lot of work. We had to cut the diverters significantly to get it to fit. The kit also included brackets to relocate the pcm, fuel pump module and oil filter. That was all pretty straight forward. The hatch lift didn't clear the headers and needed to be relocated. I'm attaching the dyno sheets. They were run using standard correction method.
The last piece of the puzzle. 31.6hp increase in HP and not the ~60hp rummored/claimed. Thanks for your time and effort Bob.
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Old 06-02-2009, 06:57 PM
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Read the charts closer...stock made 395.6 at 4800 and the cmi made 419.6 at 5000. That's only 24 peak hp but it did move peak hp up a couple of hundred. So maybe if the engine was turning higher Rpm the gain would have been a lot more. hmmmm.
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Old 06-02-2009, 06:59 PM
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I would take 30 a side if they weren't so damn proud of them.
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Old 06-02-2009, 08:00 PM
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think i would like to see the raw data including the inlet air temp and oil temps , hunidity and the uncorrected numbers before i was willing to buy into this increase.

20 deg of oil temp will make a huge dif in the actual and true power made and minor differences in the runs between the inlet air temp and the humidity will make the correction factors significantly different.

not saying you are wrong... only pointing out that if you are doing this sort of comparison and want the litteral truth at the end, then a good dyno operator will make sure that the run parameters are as close to identical as possible and even then will do several runs with each configuration and average the results...

thats why the uncorrected numbers are always best. if the run conditions are the same then the uncorrected numbers are the truth. if the run parameters are different in any meaningful sense, then the correction can easily lead you to believe somthing that is a lot less accurate.
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Old 06-02-2009, 09:10 PM
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Originally Posted by bobl
Read the charts closer...stock made 395.6 at 4800 and the cmi made 419.6 at 5000. That's only 24 peak hp but it did move peak hp up a couple of hundred. So maybe if the engine was turning higher Rpm the gain would have been a lot more. hmmmm.
Well then that is only , what, 3 hp more (at the crank/dry exhaust) than the lightening headers showed you earlier and ditto versus the Dana IV's wet/prop shaft. Mith Busters rejoice. I know I am. Bob you are the King!!
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Old 06-02-2009, 09:32 PM
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Originally Posted by Rage
Well then that is only , what, 3 hp more (at the crank/dry exhaust) than the lightening headers showed you earlier and ditto versus the Dana IV's wet/prop shaft. Mith Busters rejoice. I know I am. Bob you are the King!!
So the lightnings are doing the same power almost??

Interesting.
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Old 06-03-2009, 12:04 PM
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Pick up any speed with the boat?
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