carburettor draw through turbocharging

[gldgti]

as the name suggests, I am interested in the set up of draw through turbocharging. anyone had any experience with it?

please no responses along the lines of "why bother when this is better" and the like ;-)

[velly_16v_cab]

i ve seen setup like it on aircooled beetles...i dont have clue how they work tho lol

[abreut]

I have a mate that ran a draw through setup on a buggy with an aircooled beetle motor. It ran really well. He used an SU carby I think, the bike style ones with the slide throttle plate. He only had a small kkk turbo. It was easy enough to tune, he did have some serious icing up happening though especially when he hit the sand dunes. That thing would 3rd gear wheel-stand in the sand.

You obviously won't be able to intercool, my mate ended up running a water setup which worked off vacuum, the water was sucked in.

[Jarred]

yea, no intercooler, which generally limits the kind of boost you can push, and thus limits end numbers.

You can run a standard carby which is good, you don't need to get a carb pressurized, which can be a bit expensive.

You can move the carb around too, to place it slightly better, ie not about the exhaust.

[gldgti]

yeah, water injection is what i was thinking would be a good idea - it was all the rage back in the 30's and 40's... esp aircraft engines and superchargers.

[static1800]

A mate and his brother are into Sigma Turbos and one of theirs was a carby turbo I have another mate who used to have one also. They run alright from memory chew through fuel though.

[Jarred]

A mate and his brother are into Sigma Turbos and one of theirs was a carby turbo I have another mate who used to have one also. They run alright from memory chew through fuel though.

blow through or draw through?

And do you know what boost they we're running?

[static1800]

Carby was before the turbo, think they were running an SU from memory. My mates one went pretty damn hard.

[Jarred]

Carby was before the turbo, think they were running an SU from memory. My mates one went pretty damn hard.

That would be a draw through.

Alot of people knock these set ups. oh FI and stuff. In reality, for the street, these crude devices can be just as quick! and slightly cheaper possibly.

[DVR68U]

yeah i have had a drawthru setup on my beetle , just grab a good 1/3/4 or 2in SU and wack that in front of your turbo. im thinking about doing it to a mk1 ive got here atm , my bro and i have already sussed it out lol . you just need to make sure the fuel only has to go downwards and not back up anywhere or you can get fuel puddling and thats bad ;) . also the most important thing is GET A TURBO THAT CAN BE CARBON SEALED!!!! with out a turbo that can run draw thru you will end up chewing thru the seals in about 200kms and then burning the most oil you have ever seem. i did this one with a turbo a guy tols me was carbon sealed but wasnt . looked like i was driving a steam train . totally crazy abouts of smoke, untill the engine couldnt handle the carbon build up and got bad detination from the hot carbon build up. any how it can be done and works well. get a few extra needles for the su so you can sand them down to suit the motor. if you got any more q's feel free to ask.
cheers brenton

[Guy_H]

I built a couple many years ago on aircooled motors - there are a couple of good books available on Amazon on this subject that are well worth reading before you start spending cash on hardware!

[gldgti]

thanks guys - another quality thread from the tuning and perf section :-)

[Guy_H]

This is the book you need - it seems long out of print & I can not find my copy:

http://www.amazon.com/Turbomania-Turbocharging-Engine-Bob-Tomlinson/dp/999938272X/ref=sr_1_1?ie=UTF8&s=books&qid=1221088014&sr=1-1

Looks like you will have to pick it up from ebay!

ebay Item number: 160279375931

[Guy_H]

Dellorto's or Webers work pretty well for draw through, only Dellorto (modified & sealed) for blow through - Weber is too hard to seal.

Never tried it with SU's

[abreut]

I reckon you should give it a go. It will be good to see a turbo set-up that actually matches the period of the car. A retro turbo setup and theres no reason why it won't be as fast as hell too.

And just think you'll have the carby guys and the turbo guys on your side.

[gldgti]

I reckon you should give it a go. It will be good to see a turbo set-up that actually matches the period of the car. A retro turbo setup and theres no reason why it won't be as fast as hell too.

And just think you'll have the carby guys and the turbo guys on your side.

i agree - i like the idea of something period.

***quietly mentions...***...its not going to be for street use, i'm thinking hillclimb/track.

[Jarred]

If you go forced induction in most forms of motorsport, you'll be penalised for it I believe. your times will be X by 1.3 or 1.5 or whatever the ratio is.

I believe that's how it goes though.

[Preen59]

I reckon you should give it a go. It will be good to see a turbo set-up that actually matches the period of the car. A retro turbo setup and theres no reason why it won't be as fast as hell too.

And just think you'll have the carby guys and the turbo guys on your side.


Webers and Delortos work on pressure, whereas an SU works on vacuum, so i'm not sure whether an SU would work blow thru.. However don't quote me on that.

I like the idea of draw thru carbie setups, however i'd do it with a supercharger. ;).

Yes, you can't run as mouch boost, but i'm assuming you're doing this to a Mk1, in which case, 6 or 8 PSI would be plenty anyway. Any more boost would yield pointless unusable horsepower, unless you just want to be able to quote the peak HP figures, and i KNOW you aren't about that. :)

My uncle had a draw thru supercharger setup on a toyota 1.3l in a nota back in the late 80s. Went pretty hard apparently. He used a 2 inch SU. Seems to be that SU's must be easier to tune for this purpose. If you like, i'll get some more info off him about it. :)

[Preen59]

***quietly mentions...***...its not going to be for street use, i'm thinking hillclimb/track.

Blown Diesel! DO IT! :D

[Peter Jones]

If you go forced induction in most forms of motorsport, you'll be penalised for it I believe. your times will be X by 1.3 or 1.5 or whatever the ratio is.

I believe that's how it goes though.

Actually your engine capacity is multiplied by 1.7 so your 1800 golf ends up in a 3.0L class racing commodores.

Pete

[gldgti]

Blown Diesel! DO IT! :D

we have a lot of spare 1600's hanging around...

[abreut]

Seems to be that SU's must be easier to tune for this purpose. If you like, i'll get some more info off him about it. :)

My mate that used what I'm pretty sure was an SU for his draw thru turbo buggy had one issue - the SU didn't have any pump jets. They are extremely simple to tune and they have like one main tapered needle but the one he used didn't have an acclelerator pump jet which is crap when you boot it suddenly. It kind of slowly builds revs unlike webers which tromp like mad as soon as you stand on them.

[VW Convert]

My mate that used what I'm pretty sure was an SU for his draw thru turbo buggy had one issue - the SU didn't have any pump jets. They are extremely simple to tune and they have like one main tapered needle but the one he used didn't have an acclelerator pump jet which is crap when you boot it suddenly. It kind of slowly builds revs unlike webers which tromp like mad as soon as you stand on them.

SU's don't use a pump jet, they have a unique method of enriching the mixture when you boot it.

Inside the bell at the top of the carby there is a sliding piston which has a very light spring that pushes it down. When the throttle is opened, the venturi effect makes the piston slide up opening the port to allow the air to flow through. The piston has a damper which slows the initial movement causing the mixture to become momentarily rich. The damper requires a small amount of oil to be poured into the dashpot at the top of the carby from time to time and if the dashpot is dry, the piston will open fully immediately the throttle is opened causing the mixture to lean out and the engine to splutter.

See there is no limit to the information you can find on this forum! :biggrin:

Cheers

George

[Preen59]

SU's don't use a pump jet, they have a unique method of enriching the mixture when you boot it.

Inside the bell at the top of the carby there is a sliding piston which has a very light spring that pushes it down. When the throttle is opened, the venturi effect makes the piston slide up opening the port to allow the air to flow through. The piston has a damper which slows the initial movement causing the mixture to become momentarily rich. The damper requires a small amount of oil to be poured into the dashpot at the top of the carby from time to time and if the dashpot is dry, the piston will open fully immediately the throttle is opened causing the mixture to lean out and the engine to splutter.

See there is no limit to the information you can find on this forum! :biggrin:

Cheers

George

Thanks for that info George. I have limited knowledge of SU's and that cleared it up somewhat. :)

[abreut]

SU's don't use a pump jet, they have a unique method of enriching the mixture when you boot it.

Inside the bell at the top of the carby there is a sliding piston which has a very light spring that pushes it down. When the throttle is opened, the venturi effect makes the piston slide up opening the port to allow the air to flow through. The piston has a damper which slows the initial movement causing the mixture to become momentarily rich. The damper requires a small amount of oil to be poured into the dashpot at the top of the carby from time to time and if the dashpot is dry, the piston will open fully immediately the throttle is opened causing the mixture to lean out and the engine to splutter.

See there is no limit to the information you can find on this forum! :biggrin:

Cheers

George

There you go learn something new everyday! They're definitely different to your webers and dellortos. My mate had a whole bunch of different tapered needles which is the equivelant of the jetting I think - something like that anyway. Sounds like you know your SU's very well George.

[VW Convert]

There you go learn something new everyday! They're definitely different to your webers and dellortos. My mate had a whole bunch of different tapered needles which is the equivelant of the jetting I think - something like that anyway. Sounds like you know your SU's very well George.

Owned Mini Coopers and other assorted BMC cars for many years, when you own that type of car you have to learn to fix them yourself!

Still hate my ex for making me sell my beautiful 1970 MKII Cooper S along with the supercharger kit I never got around to fitting. :frown:

I'm sure there have been numerous draw through turbo conversions using SUs, the simplicity of them makes them a good choice.


Cheers

George

[twin eng, twin turbs]

I have built two draw through carby turbo setups on my twin eng mk1 using a sidedraught 40mm dcoe webber on the rear motor and a 40mm IDA webber on the front. SU's are a better option for smooth drivabilty though. I used the webbers because they were spare and are very tunable. I made new exhaust manifolds in both cases and modified the original solex carby inlet manifolds to suit. I made seperate downpipes for the waste gates and turbines aswell. I will have to post up some picks of the setups.

Compression ratios that are to high and high boost together are the biggest potential problems causing detonation and engine meltdown. You will need a good electronic ignition system to prevent the spark blowing out under boost and a recurved distributor with retard instead of advance when boost comes on to prevent detonation occuring in the top end rev range. If you run approx8:1 compression and around 7 psi boost it would be a cracking performer! You should easily be able to top 150hp with a internally standard 1600 with heaps of torque aswell.

I have seen some excellent power made from draw through carby turbo setups especially on 12A, 13B rotors some of which i have witnessed running 10 second quarters back in the day..

[gldgti]

wow, 150hp! i was thinking to crack 100 would be fun :-)

as much as anything it's just be great to learn about it - i have lots of diesel experience and very little petrol experience, and since i cant ever see myself owning anything but a diesel for a road car ever again, i reckon i can afford to have some cheap fun learning about "the old days" on something thats not for the road.

some pics of your old setups would add volumes of info to this already very good thread ;-)

[Oneofthegreats]

I have seen some excellent power made from draw through carby turbo setups especially on 12A, 13B rotors some of which i have witnessed running 10 second quarters back in the day..

True.

My friend's dad's 13b was the fastest street rotary in OZ in 89 & the only rotary in the 9 sec street car club. Ended up running 9.78@145mph in 90.

All with draw through weber technology & alittle gas.

Behold, the octopus!!!!


http://www.vwwatercooled.com.au/forums/images/imported/2008/09/WayneDysonRX36-1.jpg

http://www.vwwatercooled.com.au/forums/images/imported/2008/09/WayneDysonRX34-1.jpg

http://www.vwwatercooled.com.au/forums/images/imported/2008/09/comp202cm1-1.jpg

[twin eng, twin turbs]

Thats exactly what im talking about golfworx, a relativly simple and cost effective setup with maximum bang for your buck! I have a soft spot for rotors especially rx3 coupes... I'll find some pics of my draw through setups shortly or just take some new pics..

[SpeedRated]

[QUOTE=golfworx;215383]True.

My friend's dad's 13b was the fastest street rotary in OZ in 89 & the only rotary in the 9 sec street car club. Ended up running 9.78@145mph in 90.

All with draw through weber technology & alittle gas.

Behold, the octopus!!!!

Hello All.
This is my 1st post here and am glad to see people are looking into this old tech.
I might not be a water cooled VW guy, but we are all gear heads, right?

I have to ask who made those manifolds!!!?

I have been looking into draw thru setups for some time (3 years ) for a 13B. Trying to find one here in the U.S is like pulling teeth!!!
One thing I have not seen mentioned in this thread is the fact that a draw thru setup will atomize the gas on boost way better than blow thru. And the fule cool's the intake temps at the compressor blades when it atomizes. That's where the intake's heat is generated in the 1st place.
I see it as a Win Win, low tech style.

Dave

[aprr32]

Spraying fuel onto a compressor that spinning at 80,000 rpm plus does erode the blades over time.I had a su suck through 1600 Golf 1 in the early 80's and the compressor would be almost worn out out 40'000 km's.( turbo rebuilds in those days weren't as cheap as today)It did go rather well and 170 hp was a lot of power when only v8's ruled the streets.

[SpeedRated]

Thanks for the info.
I see how that would be a problem.
Glad to be getting info from people who have done this kind of set up.

Great forum.

[gldgti]

indeed, SpeedRated Dave - i think its a win win too! (welcome to the forum!)

given junkyard turbo's are plentiful in my district (saab/renoult/pug/volvo wreckers nearby) and i have cheap and easy access to lasercutters and welding (i love work) then i'm not concerened about tubo life really (feels good to say).

[Jarred]

Can you use a standard turbo, or do you need a carbon sealed unit though?

[Oneofthegreats]

Hello All.
This is my 1st post here and am glad to see people are looking into this old tech.
I might not be a water cooled VW guy, but we are all gear heads, right?

I have to ask who made those manifolds!!!?

I have been looking into draw thru setups for some time (3 years ) for a 13B. Trying to find one here in the U.S is like pulling teeth!!!
One thing I have not seen mentioned in this thread is the fact that a draw thru setup will atomize the gas on boost way better than blow thru. And the fule cool's the intake temps at the compressor blades when it atomizes. That's where the intake's heat is generated in the 1st place.
I see it as a Win Win, low tech style.

Dave


G'day Dave & welcome to the vww world.

I'm sorry, but I really can't help you with that carby setup. This was done long before I knew the family & I was less than 10 years old!

The intake manifold is a off the shelf (brand - performance ?) & also probably modified & the exhaust is home built.

I do know that this setup is not as simple as it's look's from some of the story's told.

It consisted of a bunch of fuel pump's to not only supply fuel, but to also draw fuel out of the carby, along with a couple of home built rising rate regulator's long before they were even invented!

He has said he use to tune it by richening it up until it couldn't run, stall & dump fuel out the exhaust & then back it off just alittle.

Turbo'd, draw through carby's & rotary's is where they got there bad name & bad reputation for blowing up from.

You just couldn't keep fuel up to it.

He did say he built a massive bridge port, draw through setup that was the fastest & scariest thing he'd driven back then, but it just couldn't keep fuel up it & as such would blow up after one run.

How many rotary's do you see blow up these day's with current technology. Not many.

I've heard of more piston engine's lunching themselves lately than rotary's.