No other like it.

[jmlcolorado]

Cant say i dont learn something new every day:

"Carburetor
There are two types of choices in a carburetor turbo setup: “Suck-through” or “Blow through”.
The Suck-through (or draw through) setup involves mounting the carburetor before the turbo inlet (usually in front of the impeller mouth). This means that both fuel and air are drawn into the turbo already mixed and then blown into the inlet manifold. This is by far the simplest way to set up a turbo, as the carburetor doesn’t need to be especially modified and tuning is quite easy. The main disadvantages are that you can’t use any intercooling with such a setup, as it is dangerous to run air/fuel mixture through an intercooler core. The reason for this is that fuel can condense inside the intercooler core and stay there – if you then have an engine backfire the intercooler can explode. As a result water injection is about the only option for cooling the charge air with this setup. This also corresponds to a blow-off valve because instead of just venting pressurised air, it would be releasing a fuel/air mixture which is very dangerous.

The Blow-through arrangement, logically enough, means the carburetor is mounted after the turbo compressor, so the turbo only draws in air and then blows it through the carburettor, which adds the fuel. To use a carburetor this way it has to be specially modified so that the jets will still add the right amount of fuel. This means specially sealing the carburetor and pressurizing the fuel bowls to match the turbo boost. The good thing is than an intercooler and also a blow-off valve can be used with such a setup."

 

[jmlcolorado]

Heres some more food for thought.....like you need/want more

"Engine Preparation
Forged Pistons
One of the most popular upgrades for a turbocharged engine is using “forged pistons”. Forged Pistons are made using a different process to cast pistons, which strain especially under high temperature and pressure loads. As such they are more suitable for engines running high boost (14-15PSI) and also running a large hit of nitrous oxide. Forged pistons often cost twice the amount of normal performance pistons. Generally when builders change pistons in a turbo engine, the compression ratio will also be reduced. The less compression you have, the more boost you can run without pinging. But the less compression you have the worse your car will perform “off boost”. For a street engine, a compression ratio of 8.0:1 compression will be sluggish off boost.


O-Rings
The O-Ring is a metal ring slightly larger than the bore size, which helps the head gasket get a more positive seal around the edge of the bore (where the head gasket is most likely to fail). A groove is actually cut into the head or block to locate the thin ring, which bites into the head gasket when the head is torqued down.


Regraphed Distributors
When fitting a turbo system to an engine that wasn’t turbocharged before, it is critically important to have the ignition advance curve altered to suit a turbocharged engine. Boosted engines need to have their ignition retarded at higher revs, rather than advanced like a naturally aspirated engine – otherwise they will ping extremely.
"

 

[8literbeater]

I didn't realize that a turbo would work in that configuration. I thought the boost had to be put in above the carb rather than suck through. Is that the way you have it set up? I'm still not sure about the distance between the carb and intake, plus mixed gas going thru the turbo. It will probly make it a booger to start because the mixture has to travel so far before getting to the combustion chamber. Also after shut down, there will be alot of mixed gas ready to fire in all that space. By next morning it will have dissipated making for a hard cold start again.

I had my propane motorcycle backfire and I had a large space of mixed gas in the plenum. It stretched the aluminum plate over the bolts holding it together. I had to decrease the amount of air space between to prevent that and make a quicker cold start.

It looks awesome. You may have discovered the best way ever to get awesome fuel mileage.

Hmm. I must say I'm a little surprised that more people are not familiar with a draw-through turbo setup. I'm learning more about it myself, but everyone seems to be really shocked by the concept. Even my dad said he'd never heard of it, but then everything he drives with a turbo is a diesel. The draw through is a very common way to go. I even took a picture of a nice draw through setup on a 60s ford car at a recent car show, but a bunch of my pictures got lost from my phone. I think the blow through has a little more potential for power gains, but it's a TON more work to set up. Here's a site with some basic info - http://www.dune-buggy.com/turbo/carbureted.htm

As far as starting goes, you are definitely familiar with the propane principles, others may not have thought it through, so... I agree with the probability of hard starting for gasoline, but the propane is slightly pressurized, but yes, on vacuum demand. However, the vaporizer that I happened to come to own, is an old model "E", which the propane guru that I ordered the rebuild kits from said is an obsolete model where the "E" was for "electronic purge". If you look at the third picture in post #86, you can see the wire for the purge solenoid at the top right. I may put an outlet valve down at the cylinder head for a true purge of the intake system. I expect that to solve the problem. (I believe they all have the manual purge button still.)

For the backfire thing, you have a very good point. I will either make a simple backfire valve, (blow off valves are expensive) or leave the silicone connecting elbow loose enough that it can blow off, which I have personally seen to work. BDS sells backfire valves that are very easy to duplicate, so that might be fun. Otherwise I have a fancy pipe bomb.

 

[8literbeater]

Im no expert by any means, but wouldnt you have the potential for pre detination when the turbo gets under pressure since compressed air gets hot? Might not get hot enough to detonate before entering the cylindar but its a thought. Hate to see your setup explode

Don't forget, every roots type blower with a carburetor is pressurizing the air/fuel mixture essentially in the intake manifold. You are correct about the turbo being hot though, but not that hot. Thanks for the input.

 

[8literbeater]

ya just noticed that once people started ponting it out. That turbo set up is bothering my a bit. Ive been around turbo car all my life and have a turbo M3 right now and that just seels a lil dangerous. Mixing gas in the turbo then trying to push it into the engine. also that height of the turbo and trying to get a good mixture while traveling upwards is going to be very hard. Im with the other guys and say put the carb on the other side of the turbo for better fuel mixture.(unless you h ave something up your sleve that we dont knwo and you know this is going to work). enlighten us and let us k now if you have something worked out

With a draw through setup the mixture works exactly the way that a non-turbo carburetor works. It just uses more of it. As for the mixture and its trek through the system, propane vaporizes at -44 degrees Fahrenheit. It can never condense or puddle above that temperature unless you get it back to 250 psi (give or take).

 

[Hydrocarbon Rocket]

The propane should be safer than Gasoline. The propane will not ignite until its 920 deg f. The gasoline will ignite as early as 495 deg f. How hot will the turbo get?

I sure wish you was close by. I would love to come by and see your machine.

 

[8literbeater]

Heres some more food for thought.....like you need/want more

I'm only gonna run about 6-8 pounds. It's not really for power, as much as it is just for fun and the experience. I think it starts out with around 8:1 compression. The other thing, propane has an approximate octane rating of 110. So it won't detonate or ping very easily at all.

 

[8literbeater]

How hot will the turbo get?

Well, according to my highly scientific calculations, with the turbo being out in the open air, it's air cooled. So the faster I drive, the safer I'll be.

 

[jfg455]

The propane should be safer than Gasoline. The propane will not ignite until its 920 deg f. The gasoline will ignite as early as 495 deg f. How hot will the turbo get?

I sure wish you was close by. I would love to come by and see your machine.

I like to try and keep the turbos under 1500 F. Any more than that and it is probably running lean. That is turbine housing side. it is nothing for the hot side of the set up to be glowing bright red under full boost. 350-550 F driving around town and 1400-1500 F under full boost for a period of time. This is with an EGR tapped into the down pipe right after the turbo on some of the LSX builds I have done.

The cold side you will easily see IAT's in the mid 200's F if you aren't carefull with the boost. Itercoolers and Meth injection are your friends for lower IAT's (with gasoline engines).

Draw through turbo set ups have been around since the 60's at least in the hot rodding scene. They just arent as efficiant as a blow through or an EFI set up. 83-84 turbo buicks were a draw through system. They were dubbed the "hot air" cars. as soon as they went to EFI they started hauling some butt

 

[CCROCHET]

I have def learned something today. I have never turbo'd a carb'd engine before. I have always comes from fuel injection and when you say "draw thru" to me that means you meter the air (m.a.f) before the turbo instead of "blow through" there you meter it (m.a.f.) after the turbo in between the throttle. SO with us we never mix fuel and air before the turbo bc we have to run intercoolers. SO this whole "draw thru" with mixing air and fuel is new to me. But def excited to see yours running bc now im rethinking my ideas for turbo set up on mine. So many options now. hahah

 

[8literbeater]

It runs!![cl

Last night, just past midnight, about 20 feet from my neighbor's house I finished the pieces and parts and had to give it a shot. I didn't finish sealing up the fuel ports and things, so it has some vacuum leaks I'm sure. I cranked it until it got oil pressure and oil came from the return line on the turbo, then hooked up the ignition wire. It sputtered a little and then started up and ran right up to about 3000 rpm! It sounds like a jet powered machine gun! (my neighbor loves me)

So after making sure that the throttle was indeed closed, and it still wasn't coming down, I just pulled the power wire off the ignition and packed up for the night.

 

[earthman]

 

[8literbeater]

So I've got some fine tuning to do! Still it runs great despite not adjusting the valves since putting the head on, and the intake tubes sucking flat! I should've seen that one coming.

The iPhone just doesn't do the sound justice. [ddd

http://www.youtube.com/watch?v=7UspEPXAuyA&sns=em

 

[Hydrocarbon Rocket]

Cooool![cl

 

[DJ3100]

Thanks for the viedeo, interesting to see the intake tubes collapsing. It sounds way better than I was expecting, considering the vacuum leaks and undajusted valves you were talking about.

It started pretty easy considering it was propane. No explosions?

 

[Stacy]

Those hoses remind me of a beating heart, it's such a beautiful engine set up, I love it.

I like how the exhaust is just high enough so your neighbors can see it over the wall and nothing else.

 

[8literbeater]

Thanks for the viedeo, interesting to see the intake tubes collapsing. It sounds way better than I was expecting, considering the vacuum leaks and undajusted valves you were talking about.

It started pretty easy considering it was propane. No explosions?

Well, I actually plugged the vacuum leaks for the daytime test. It had already been running, so it wasn't a fair cold start. But I have to say, I will be building for propane whenever possible from now on. It is so simple and easy to work with. The rockers really are making a racket too. I'll have to wait until I have a radiator to adjust them with it running.

I'm wondering if I should lock out the centrifugal advance for the sake of the turbo and whatnot. On my 59 I run it without the vacuum advance. The shop that did my heads and dynoed the engine said to block it off or melt the engine. Maybe I should just run this one without the vacuum advance, and retard the initial timing? Anybody have experience that they can use to advise?

 

[8literbeater]

 

[DJ3100]

Wait!! -where did the Stude come from? Is that your project?

 

[8literbeater]

Ahh yes, the Stude. It's a little short term project. Which means it's for sale! I'm just gonna fix stuff until it sells. It's a 47 Commander, anybody want it?