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#1
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Drawn through turbo application for motorhomes
Funny thing happens when you get old.
You quit measuring performance in MPH and start measuring it in MPG. Making something that normally gets about 8 MPG cough up a few more miles per gallon is a challenge for sure. And that would be most of the gas powered motor homes out there. I recently purchased a classic 1978 32' Avco motorhome powered by a 440 and a torqueflight. (was cheap and in fantastic condition, otherwise I would have passed) There was a aftermarket kit back in in the hey-day of this kind of rig that was a drawn though; like a roots blower setup accept with a turbo. Anyone experienced with the ins and outs of a drawn though system? I understand it isn't the "best" setup but I'm looking for boost levels in the 6-8 lbs range max. I have asked this question in some other places and got a overwhelming negative response. Blown through may be better for max power but it requires a lot of specialized carb tuning. Nobody is talking a max power application. What I have in mind is a boost in efficiency (cylinder filling) that would yield better MPG. Keeping the boost low and the fact late model 440 probably has a stock compression ratio of 7.5:1-8.0:1; turbocharging could be a win-win. |
#2
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Same kind of setup was used in the early GM turbo cars, V6 Buicks and 301 Pontiac. I believe even 6-8 psi may be hard to achieve. The main problem with the draw through is that you will have pretty hot intake temperature, but there are others. However, it is very simple and inexpensive method to add decent power if you can fabricate things.
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#3
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Quote:
The biggest problem I'm finding is people narrow minded thinking when it comes to turbocharging. Only thinking "max power" applications are legitimate is really kind of silly. A drawn through bolt on system was a popular bolt in the 70s and 80s for motor homes. But all info on these has disappeared completely. IF you goal is just a few lbs of boost to improve efficiency; this system is ideal. This low compression 440-3 will probably get 5-6 MPG on for this heavy coach. When gas was cheap; meh. Today it isn't cheap. I'm already planning on a Gear Vendors OD system which will be at least 3 grand. But I will be leaving a lot of potential fuel savings on the table if I don't seriously consider maximizing combustion efficiency. Turbocharging is still the best method because it does not rob power from the engine to drive it. |
#4
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the problem with the draw through for max power is, that you have to carry the air fuel mixture quite long and curvy route, and there is no easy way to lower the temperature. I know one AMC Hornet 360 that has run a 9 sec ET with a draw through set up, and one Fox Mustang that also run 9's with a draw through centrifugal! Both had dominators on the suction side.
I would not expect wonders as far as the mileage goes... |
#5
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would it not be better in the long run to put in a cummings with trans out of some late model truck, i think it would be cheaper too, not too mention more reliable
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#6
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Quote:
You can swap a Cummins 4BT into a half ton truck (Ramcharger in my case) and if setup correctly see 25 mpg and all the torque you will need. It is easy to setup a small vehicle but in this case it isn't ideal. Unless the swap is a boon in fuel efficiency and AND torque it might not be the best way forward. The Cummins 6BT "sweet spot" is 1800-1900 rpm. This thing has a 4.88:1 Rockwell rear end. Even with an OD gear that would put me running 45-50 mph to maintain the ideal RPM range. Smaller coaches have a more manageable ratio (4:11) and you can hit the sweet spot at a more ideal HWY speed of 60-65 which is ideal considering the amount of drag these have. Besides that the cost of the swap is very expensive, diesels are HEAVY and LOUD and the fuel is expensive. Normally diesel motor homes are pushers because of the noise. The only way I could make a 6BT work is to run a double OD. That is to swap in a 4spd OD tranny AND run a gear vendors type OD. My plans are to do a Gear Vendors OD and that would put the 440 at about 2400 RPM cruise at 60 mph. There is actually plenty of room to add a turbo and going with port EFI isn't out of the question (MegaSquirt 3). But all of this would be cheaper and easier than swapping in a diesel. Now unless we are talking about a 2 stroke Detroit Diesel.......Hmmmm |
#7
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440-Turbo
Hey Doc. I have looked at this, and was considering Hypermax. They make a turbo for the Ford IDI diesel from the 80's and 90's that makes 12 psi max. Might be worth a look.
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