turbo setup with stock su carbs

[erichwaslike]

basically just wondering if there is a way to boost reference the stock su carbs so they deliver more fuel when the boost comes in. tossing some ideas around and wood liek to stay away from fuel injunktion to simplify it and keep cost down. anywhere i can go to get info on it is appreciated

 

thanks

 

erich

[ggzilla]

No but if you put them in a box, and use the blow-thru system it will work. Or, you can move the needle a bit to richen them overall.

[erichwaslike]

does it have to be in a box or can i just plumb it to the front of the carbs? same basic idea? or does it do something to have the whole carb under pressure?

[RAlly_DatoB210]

I believe you need to have it before the turbo or else it will run lean. In front it will draw fuel through and then the air gets compresses but carbs on the other side will just have air pushed passed them without much fuel delivery. Plus it might be a bit hard on the carb? I considered building a box around my itb set up and doing draw through but don't think it would work as well. Blow through should be fine as everything is in the box and at the same pressure. Don't know the logistics but think that's basically the idea but I may be wrong

[ggzilla]

If you box the whole carb, it works great under boost.

 

You can instead blow into the carb, but I don't know if the SU-type works well with this. The stock Datsun hitachis work OK this way at 5-10 psi.

[hacked521]

it has to do with the whole carb in a box. it puts the carb in its own atmosphere.

[Skib]

if your going blow threw you have to O-ring the throttle shaft on the SU's

[Logical1]

I've been messing around with several SU setups and the suck-through seems to perform the best. Skibs right if you box the whole you carb you have to o-ring the shafts and get a boost actuated fuel pressure regulator/pump so that when the boost hits the fuel pressure goes up to equalize. Suck through you just put the carb before the turbo inlet swap out the turbo gasket for a fuel resistant one and Vroooom! nice article and a cheap/easy home-brew turbo SU: Turbo SU

[erichwaslike]

if your going blow threw you have to O-ring the throttle shaft on the SU's

 

even in the box or is that out of a box?

[Skib]

even in the box or is that out of a box?

 

 

any blow threw set up, they leak even when you run normal SU's :lol:

 

 

in the SU turbo research Iv done Iv found that the easiest way to do is with a single large SU draw threw.

 

 

an SU blow threw is plenty doable its just more expensive/more work.

its easier to use a down draft webber and a box IMO tho

 

heres a side draft set up. i got lazy and dont feel like finding a down draft picture lol

[erichwaslike]

well im looking to do it where i use the stock intake and carbs as it came factory (location wise) and put something in front of it so it is still kinda stockish if that makes sense?

[Skib]

well im looking to do it where i use the stock intake and carbs as it came factory (location wise) and put something in front of it so it is still kinda stockish if that makes sense?

 

 

let me go find my L series turbo notes.

 

might be able to do the blow threw without having to O-ring the throttle shafts

[ggzilla]

Draw through is the way to go, easiest too. Except if you want to use an aftercooler, which you can't with draw through (or at least not safely). Draw through is good for 5 psi or 10 psi with water injection.

[RAlly_DatoB210]

Draw through is the way to go, easiest too. Except if you want to use an aftercooler, which you can't with draw through (or at least not safely). Draw through is good for 5 psi or 10 psi with water injection.

Once again my memory could fail me but with water injection I think I remember someone using the wiper sprayer? An it would spray when the pedal was floored? And could an intercooler actually get enough gas pooled in it to explode? Or am I just pipe speaking at this point? Ha

[erichwaslike]

i dont mind oringing them or modifying them at all but i want to use the stock mani and stuff so it looks stockish. basically and add one from the stock filter forward

[Skib]

Once again my memory could fail me but with water injection I think I remember someone using the wiper sprayer? An it would spray when the pedal was floored? And could an intercooler actually get enough gas pooled in it to explode? Or am I just pipe speaking at this point? Ha

 

 

 

itd be worried about the fuel staying atomized all the way from the carb, threw the turbo, threw the intercooler and finally into the intake

 

 

 

 

Iv never seen it personally (not many people run it) but I can see it happening

[Skib]

i dont mind oringing them or modifying them at all but i want to use the stock mani and stuff so it looks stockish. basically and add one from the stock filter forward

 

 

then yes I think.

 

have have to seal the shafts and the float bowls.

 

 

but at the same time SU's are constant vacuum carbs, and the piston/needle are drawn up letting more fuel in by engine vacuum.

 

 

 

I had a bunch of notes on this, need to find them lol

 

I do remember that I had concluded the way to go with SU/turbo was a draw threw set up with a single SU in front of the turbo.

all of the old brit cars with superchargers and turbos always run the same set up too.

you dont see vary many blow threw SU set ups.

 

 

its always with side draft weber, solex, ect type carbs.

 

[RAlly_DatoB210]

itd be worried about the fuel staying atomized all the way from the carb, threw the turbo, threw the intercooler and finally into the intake

Iv never seen it personally (not many people run it) but I can see it happening

ok more sense made. So like a turbo stuff destroying flame thrower?

[Skib]

let me go dig up all my turbo L notes

[erichwaslike]

this is wat im thinking

 

 

dont get too involved im just seeing if its possible and worth attempting if u gotta go thru notes do it whenever, im not starting on it tomorrow

[Skib]

this is wat im thinking

 

 

dont get too involved im just seeing if its possible and worth attempting if u gotta go thru notes do it whenever, im not starting on it tomorrow

 

 

oh Im glad too, this a good discussion and Iv done research on the subject already

 

let me find my stuff and get back to this thread, Ill figure out how to do it :lol:

 

Iv been playing with the idea too, Id love to turbo my L16 with the SSS SU's I have on there

[erichwaslike]

cool

[Skib]

ok so lets start with this diagram.

 

this is an SU draw thru set up.

 

its the most common SU/turbo set up and we know its works.

 

but it doesnt keep the regular SU location

 

 

 

It can be run with a single or duel SU's and is very common with the brit cars turbo and super charger set ups.

 

 

 

it requires no mods to the carb since SU's are constant vacuum carbs and being in front of the turbo

theres no pressure being pushed into it and therefore it doesnt need to be sealed.

 

but thats all well known and not really important other than for comparison with the blow thru set up

[Skib]

what we want is to keep the stock intake/carb location

 

 

 

 

possible problems and complications:

 

- SU's are constant vacuum carbs, the needles are draw up by vacuum. how will pos. boost affect this?

- float bowls will need to be sealed

- throttle shafts will need to be sealed

- will the dome spring need to be stiffened to keep the needs from being forced up by boost?

 

- can it be run with an external box (like side draft webers?)

- will boxing the whole carb work best? will it remove the need to seal the shafts?

 

- other issues?

 

 

 

over all its already been concluded that a draw thru is the easiest and most practical to build for turbo SU's

and over all an EFI set up is best.

 

 

 

 

but for the sake of figuring out how to run a proper blow thru SU set up,

discuss...

[erichwaslike]

ur stock su pic looks better than mine.

 

im not too familiar with the operations of su carbs in how they work, is there another thread on her that explains it or a site that u can link to just so i can get it down and try to figure some of it out too