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Author Topic: 8v92 blower gear  (Read 509 times)
Rick 74 MC-8
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« on: August 20, 2013, 07:34:02 PM »

My Brother has a 8v92 in a 92 Prevost DD11. He is changing the blower gear to 38 tooth. Seems strange no other changes need to be made.   One of the techs at DD told him nothing else needs to be done. Does this sound correct?

Thanks Rick 74MC8
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About 20 Miles West Of Chicago
TomC
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« Reply #1 on: August 20, 2013, 09:58:49 PM »

What gear does he have now-what is he changing from to the 38 tooth? If he's slowing the blower down-that's good-just have to add the bypass valve to the blower to take advantage of that. If he's trying to speed up the blower, he's just wasting more fuel driving the blower faster when the turbocharger takes the work for the blower when at power. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Rick 74 MC-8
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« Reply #2 on: August 21, 2013, 05:12:00 AM »

He is speeding it up. He thinks it will help excelerate better. He's also replacing the bypass. I agree with you Tom if it was that easy to pick up horsepower it would have been done by the Detroit experts. My main question is just being able to replace the one gear. I would think you would have to replace the set to mesh correctly

Rick
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bevans6
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« Reply #3 on: August 21, 2013, 05:38:40 AM »

The blower gear is driven from the cam gear, and you don't change the cam gear.  It's possible to have different tooth counts on gears if the gear tooth profile was correctly designed to allow that.  As I understand it, in a turbocharged engine the blower is really for starting and idling.  It actually is a bit of a hindrance once the turbo is at positive pressure.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
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1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
TomC
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« Reply #4 on: August 21, 2013, 07:15:38 AM »

Rick-your friend will loose fuel mileage by speeding up the blower. Sounds good on paper though. He should keep the slower blower drive and make sure he has the most recent version of enhanced bypass valve for the blower. The bypass valve allows enough turbo pressure to go around the blower to make the pressure on the intake and exhaust side nearly even. Hence, the blower is not pumping air and just free wheeling. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Sam 4106
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« Reply #5 on: August 21, 2013, 07:25:53 AM »

Tom,
I have a 1990 8V92TA DDEC II with a mini bypass blower. What is the difference between what I now have and "the most recent version of enhanced bypass valve for the blower."?

Thanks, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
bevans6
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« Reply #6 on: August 21, 2013, 07:26:21 AM »

I wonder - can you add a bypass valve to a blower that doesn't have one?  The ex-military setup I have is turbo'd but does not have a bypass on the blower.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
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