carburettor draw through turbocharging

[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!

[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!

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!

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!

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!

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.

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!!!!

[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..