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TOPIC: Alternative vacuum supply to stop using up intake manifold vacuum

Alternative vacuum supply to stop using up intake manifold vacuum 24 Jul 2020 06:50 #1

  • neil
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This is a Bosch Alternator with a vacuum pump. I see these on Nissan patrols with TD42 motors and Isuzu diesels like 4JB1 motors.
I suggest it is a way to remove the load and possible leaks of manifold vacuum which might be detrimental to the groove operation. They need to be connected to engine oil pressure and also have a oil drain back to sump so will cause a little more work to fit.
I have also heard about an Australian car using an electric vacuum pump for brake vacuum supply, this might be another good way to disconnect the intake manifold from everything.

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Alternative vacuum supply to stop using up intake manifold vacuum 24 Jul 2020 09:52 #2

  • GregK
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There's a common shaft for both the generator and the pump, turned by the engine crank/belt?
A bigger alternator to drive an electric pump sounds to me like it would be more efficient. I'd love to get my water pump off the belt drive system, but I'll get serious about that if I ever need to replace my alternator (which would get upgraded to 200+ A)

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Alternative vacuum supply to stop using up intake manifold vacuum 25 Jul 2020 08:38 #3

  • neil
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Hi Greg, Yes I would probably opt for an electric vacuum pump if cost is the same, but I would expect it doesn't draw much power, nor enough to warrant upgrading the alternator. Most alternators have plenty of unusued capacity. Replacing water pump with electric is different tho, Cooling systems is one of the few things that I do know loads about. A close friend of mine won plenty of speedway trophies with an engine that I helped develop, and it ran an electric water pump. We modified the cooling system heaps but I was never sold on the electric pump part.
Even if you allocated 100 amps to the water pump that still only equals 1200 watts, belt drive water pumps use far more power than that and they use it to good effect. A cooling system gives you thermal tuning. No point having a computer tuning to engine temperature if some cylinders are that temp, others Cooler and warmer. Literally the warmer ones would be running rich and vice-versa. I saw a kit developed for a common 6 cyl inline motor that guaranteed 10 percent better economy and power. All it did was upgrade the water pump and some plumbing to equalize temperatures.
Automotive cooling systems are such a disappointment. The pump impellers alone tell the story, you only need a little logic....or a water pump off an industrial diesel and you'll soon agree with my disappointment.
If you wanted to improve things through your cooling system I would suggest a modified impeller to pump more water and cavitate less, then drill very small hoses into the back of your motors coolant jackets highest points and vent the hoses to just under your radiator cap. Theres most likely a benefit to be gained and really all you're doing is upgrading your automotive cooling system to commercial engine cooling specs.
I have done this many times but never have I done it around fuel economy checks that I have documented.

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Last edit: by neil.

Alternative vacuum supply to stop using up intake manifold vacuum 25 Jul 2020 11:00 #4

  • GregK
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I'd like to see how much of a difference using a vacuum pump would make. You're going to go ahead with this mod to one of your vehicles?
my money is on 1-2 miles/US gallon (3.2km/3.78litres, or 0.85 km/l). every little bit helps, though, in bringing down cost of operation.

This is important and should be stickied somewhere: Note to people outside the US - a US gallon is 3.78 litres and an Imperial gallon is 4.5 - if you're trying to make your numbers jive, it's important not to mistake the difference. Your gains will be ~20% lower than what they really are!

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