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Dodgeman
Re: SUPERCHARGING A15
#11
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I hadn't imagined anyone running a positive displacement blower as a blow-through instalation.
Do you use a BOV?

I just like the image of a trad. Hemi with the huffer & dual quads. Thats motoring.
P.S. I need some good drive gears for my 6-71 if anyone can help out. Oh yeah, & an aftermarket back plate.

EDIT
Quote:

Dodgeman wrote:
The level of boost pressure in a positive displacement supercharger's manifold is directly related to throttle opening.

If you want to run in the negative pressure zone [vacuum] in the manifold, just close the throttle a bit more.
Actually, that would still be valid in a blow-through setup except that the vacuum would be below the throttle plate, ... ummmm, ... as it would be in a suck-through, if you , ummm, ... get what I mean.

Posted on: 2006/11/27 9:26
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Lobster
Re: SUPERCHARGING A15
#12
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Quote:

Grunterhunter wrote:
I'll get in on this one just for a laugh....

Dodgeman- yes, but only if you are running a draw through. Blow through the carb and the fish-kettle is very different and a little more stinky.
The parasitic drag is always there and always more than a turbo, unless you hook up the electric clutch (SC12 &SC14), but then you need an alternative inlet for when the blower is not running.

I am in the process of putting a SC14 onto an A15- Budget build (less than $1000 AU) using the stock pistons & stock inlet manifold, & stock compression. I am planning to run a blowthrough, boxed 32/36 carby setup with intercooler (definatley required for 9:1 compression). 4-6psi to start with & 8-10 if all goes well, although I may have to decompress for that boost level.

I will draw up some plans for the blower mounts & give details of carby jets, pulley ratios etc, if all goes well.


This is exactly what I was looking at. I would be very interested in seeing your plans.

Posted on: 2006/11/28 0:10
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1971 Datsun 1200 Coupe
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Standard 1200 4 speed with lightened fly wheel and HD clutch
Stanza front struts and brakes.
15x6 CSA Wheels with 195/50 rubber.
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Grunterhunter
Re: SUPERCHARGING A15
#13
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Quote:

Dodgeman wrote:
I hadn't imagined anyone running a positive displacement blower as a blow-through instalation.
Do you use a BOV?

Actually, that would still be valid in a blow-through setup except that the vacuum would be below the throttle plate, ... ummmm, ... as it would be in a suck-through, if you , ummm, ... get what I mean.


The standard is to run a bypass circuit rather than BOV. It's a manifold vac operated secondary Throttle body that opens to allow air to run directly from the outlet of the blower to the inlet of the blower- & closes under boost
- I reckon a BOV would work but would be even more annoying than normal because it would scream its head off on overrun untill the engine revs dropped (turbo jsut goes pssst and by that time there is no more pressure from exhaust).

-Fair call on the other point- EDIT at idle or just off idle, with the throttle a few mm open you would still get manifolc vac- after that the fun starts

Posted on: 2006/11/28 1:06
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Grunterhunter
Re: SUPERCHARGING A15
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I've had a change of heart last night on the blow through setup.

Looking at things a bit more closely I have realised that if I change the mounting position & mount the blower upside down I will be able to make up some new mild steel manifolds (less of a headache than trying to modify the alloy ones) to give the option of either draw through or blow through. It will be a bit of stuffing around to swap between the two setups, but it will make the design more versatile & allow me to start with a draw through & fiddle with that while I source bits for the blow through.

Initially I was not excited about draw through because of the extra inefficiencies (You have to run the carby super rich because fuel sticks to the blower lobes, warm intake charge means that adabiatic loss is high etc) But as a simple low boost starting point it may not be such a bad thing.


Posted on: 2006/11/28 1:31
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A14force
Re: SUPERCHARGING A15
#15
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Quote:

Grunterhunter wrote:
But as a simple low boost starting point it may not be such a bad thing.


works for me.

Posted on: 2006/11/28 6:21
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prospec
Re: SUPERCHARGING A15
#16
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can you turn the superchargers upside down? i was told because it had an oil resivour it had to be sood up the right way...not that i know what sort of lubricating systme its got on it...(sc14 im refering to)
Thanks

Posted on: 2006/11/28 8:49
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DatsunDrifter1
Re: SUPERCHARGING A15
#17
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Yes. Supercharging an A15 is hell of alot better than turbocharging it but like they have said it isn't that cheap neather. I have seen one supercharged Datsun 1200 with Supercharged A15 and that baby hauls.

Posted on: 2006/11/28 11:46
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prospec
Re: SUPERCHARGING A15
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Hey all i was wondering if anyone knew the maximum boost a sc14 would produce. i read an article saying 10psi but other paces say heaps more can any one help? Thanks

Posted on: 2006/11/28 13:52
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Grunterhunter
Re: SUPERCHARGING A15
#19
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Disco stu has mounted his blower upside down & over the other side of the engine bay

the yellow engine bay


and A14 force has mounted his sideways and has not reported any trouble with it:

sideways

Datsundrifter1- supercharging is not better than turbocharging. On any given engine, set up optimally for the application (cam, ignition, exhaust etc) a turbocharger will make more peak power than a roots blower. Set up with EFI, the turbo should make more power and still be drivable, without excessive lag etc.
People like me like blowers cos they give good torque down low which is ideal for a street car, and because they suit the technology of the era.........and also cos my knuckles drag along the ground.

Prospec- Depends what engine it's on- a rootes will push more than 10 psi under the right circumstances, but they become inefficient at high boost. If you are planning for more than 10 psi you probably want to consider all your options & look towards injection forgies etc, in which case money is no object & you would chose something other than a $250-300 blower off a late eighties toyota

EDIT:

and another upside down

Posted on: 2006/11/29 1:30
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A14force
Re: SUPERCHARGING A15
#20
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Quote:

Grunterhunter wrote:
.........and also cos my knuckles drag along the ground.



The only reason they drag on the ground, is from having your arms streched from trying to hold on to the steering wheel from the Ball tearing acceleration.
People can agree to disagree untill the cows come home about it. But show a hairdryer (Every GIRL has at least one) equiped machine that can do a standing 1/4 in under 4.5 secs.
I fear gasoline will be obsolete, and most of the world will be covered by water quite some time before that day comes.

Posted on: 2006/11/29 5:09
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