So I have a '51 Chevy and I'm putting in a 250. I got some great advice on that, some parts, and got directed to the inliners website which I put a post about this on also. So who on the HAMB knows anything about a draw thru turbo setup? I think it would be a kool mod. I have an idea of how I want to fabricate my manifolds, but have no clue on how to modify the turbo to live compressing air and fuel. As a side note how cool would it be to run a blow off valve with a pipe to the back of the car and put a spark plug in it? Typical exhaust pressure is only about 3-5 psi and I have seen guys blow 20 footers with regular flame thrower kits. Imagine 12 psi with straight pressurized air and fuel mix. I'm thinking 40 to 60 feet. I could start a forest fire from the parking lot of Five Guys!!!! Ideas, comments???
I've heard that you want a turbo with a certain type of seal for a draw-though setup. Here's something that says that: http://www.smbaker.com/rail/monsterturbovw.html I've also heard draw-through is fussier, but some people say it aint so. Would your flamethrower ignite every time the BOV activated, or would you send raw fuel out the exhaust?
Probably not a good idea to let it flame every time the blow off pops, so likely would be dumping some raw fuel between shifts. That's a really good example of cheap ass hp. Thanks. V-Dub guys come up with cool stuff like that
You need a turbo designed for draw through that has internal lip seals, and a really short manifold setup so there can be no fuel puddling. Also, you don't use a blow off valve in a draw through setup - you use a bypass valve that simply dumps the air/fuel mix before the turbo into the intake plenum under the carb. They work fine if you build them like this. I have a draw through setup on a SBC sitting on the stand right now.
Any of the early Buick V-6 turbos (1978 through maybe 1985?) were set up this way from the factory. You could probably just use their whole package since your engine is of similar size (the Buicks were 3.8L or 231 cubic inches). 78 models were available with 2 barrel or Quadrajet. I think they dropped the 2 barrel after that. I've seen photos of a Hudson flathead 6 using a turbo setup directly off the Buick.
The last thing you want is to ignite popoff mixture. If anything went wrong and the flame backtraveled.......the resulting intake explosion would not be pretty. Backfires + forced induction = broken wallet
it's called a carbon seal and most (not all) turbos can have one installed. i've truthfully never seen a draw through setup with any kind of blow off or bypass setup. you really don't need one. the point of a blow off is to release the built up pressure in the intake between the outlet of the compressor and the closed throttle blades. because this is a draw through setup you'll never have a situation like this. duh.
Drawthru is easy, it's the blowthru setups that are a PITA. No real need for a custom manifold/header, just bend up some exhaust to go to the turbo. +1 on the buick setup, but they have been getting hard to find the past couple years. You might try and see if someone on one of the turbo-buick web sites has a spare to sell.
I think a friend of mine has the turbo and intake off of a 301 pontiac turbo. They would work also. IIRC they use AiResearch TB03's. Most RayJays also have the carbon lip seals. A lot of cheap offshore turbos do not, and a lot of diesel turbos do not. You still need should have a bypass valve in a draw through setup. When I had my car together you could hear it go off all the time. Its not as critical however, as on a blow through setup.
The blow off thing just kind of sounded cool but then I read the VW thing and got an understanding of why a carbon seal is needed and realized that it is the same reason a BOV is not; manifold vacuum when not making boost. I am thinking any turbo that is the right size would be ok since I could just but a seal kit with carbon seals. Any advice on what I should do about the carburetion?
i used this info when i built my turbo vw. found it really useful!! lots of info on this site...check the carbs link at the top http://www.dune-buggy.com/turbo/turbo.htm
Chevrolet Inline Six-Cylinder Power Manual by Leo Santucci. They have a good section on Turbocharging the chevy six.
A draw through is easy, but it has it's problems. The turbo has to work harder to pump air AND fuel through the compressor housing. Also, the turbocharger needs to be very close to the intake plenum otherwise fuel will puddle up in the intake and won't be evenly distributed to the combustion chambers. You'll need a carbon seal turbo, instead of the more typical dynamic seal. This seal will prevent the oil from being sucked out of the bearing housing and through the compressor housing. Most Garrett T2, T25, T28 turbos have encapsulated carbon seals, and the bigger T3 and T4 family of turbos can be outfitted with a 4-piece carbon seal kit. Older Rajay turbochargers had carbon seals but are hard to find, and hard to find parts for, but they are out there. Try the aircraft community for Rajay Parts. Here's the differences in carbon seals/dynamic seals... And here's a picture of a Poncho 301 draw through system that is very basic... You'll want to use a 4bbl carburetor with small primary jets and large seconday jets with some sort of vacuum regulator that will increase metering rod enrichment during boost. Also a wastegated exhaust housing to restrict boost levels. The oil pump should be upgraded as well since the turbocharger is cooled and lubricated by the engines oil, unless you do a remote pump & reservoir system. The oil pan should be baffled as well to keep the oil where it needs to be under boost. The 301 pictured above was a stock draw-through setup on the early Trans Ams and used an 800cfm Q-Jet, and a Garret TBO305 Turbocharger. You'll need to get gauges to monitor the system. Gauges are important on a artificially aspirated engine.... BOOST PRESSURE - to make sure you are not overboosting, or to make sure that the turbo is operating consistently. EXHAUST GAS TEMPERATURE - to make sure you're not overheating the combustion chambers, pistons, and cylinders. I've seen lot of melted pistons due to overheating. FUEL PRESSURE - to make sure you have adequate fuel supply under boost AIR/FUEL RATIO - to watch lean/rich conditions. I watch my aftermarket gauges more than my stock gauges, they tell me everything.
As for your Blow Off Valve idea...it wouldn't work. The Blow Off Valve, or "BOV", vents off compressed air pressure when the throttle valve is closed. This only is required on a blow-through setup. When you're building boost, and you let off the throttle, the throttle valve is shut, limiting the air into the engine. Well, there's still pressure in the charge pipe between the turbo and the throttle valve, so this causes a pressure surge and backfeed of compressed air in the charge pipe between the turbocharger and carburetor/throttlebody. The BOV pops off the excess pressure to prevent that surge of air from harming the turbocharger. If a BOV is not used, the surge of air could harmfully slow the turbocharger down and cause internal damage to the thrust bearing of the turbo. If you're talking about a Wastegate...the wastegate diverts exhaust gases away from the turbine wheel, which controls the speed of the turbine wheel, as well as the compressor wheel, which limits boost. The exhaust gases are either dumped out of a dump tube, back into the atmosphere, or back into the exhaust into the downpipe. You should always use a wastegate because over boosting can hurt the engine, and overspinning of the turbocharger will decrease it's volumetric efficiency and start forcing hot air into the cylinders. A wastegate is can be pre-set at a specific boost level, or can be adjusted with an inline regulator or needle valve on the pressure tube between the compressor housing and the actuator. Also, I've seen draw through systems, that were not actually drawing fuel through the compressor housing, but siphoning the fuel through the snout on the compressor housing. This would allow a couple of things... No chance of carburetor parts falling into the turbocharger. No fuel puddling at low boost levels. More consistent air/fuel mixture since the compressor wheel is not chopping it up. It's something you'd have to experiment with though as it's not quite as common.
School me: On a draw thru turbo, you have air mixed with fuel going through a spinning blade. Since the fuel is heavier than the air, wouldn't the centrifugal force remove some of it? It seems like it would sling up against the sides of the turbo housing and puddle somewhere. It seems like it would make for bad gas mileage and surging performance or idle. I'm sure I'm not the first to ask this question. Maybe you could direct me to some information on the subject.
My general understanding of a draw thru setup is that it is easier to tune than a blow thru because the carburetor has an atmospheric reference. Just like a draw thru blower it needs to be basically right above the intake (thinking 8-71 blower vs. a Vortec). I know that hp wise the blow thru is way more efficient but ease of setup the draw thru is (theoretically) much easier to deal with (once again picturing 8-71 vs. Vortec). But I have bo experience with the turbo or a 250. So for the big question; If running a 4bbl should is be a vascuum or mechanical secondary?
I guess it's what you're used to.....the draw thru is a PITA with the blow thru is easier IMO. The driveability is not quite as good with the draw thru. Harder starts and the fuel puddling issue. A backfire becomes a REAL fire! LOL Go to theturboforums.com and do some (lots) of research. Turbos are fun!
can be done, i put together a draw through in high school..... very quick boost, almost lag and a blast
I could go on for weeks trying to teach a monkey how a turbocharger works and what you need to make it work properly. I suggest you do some more research before diving into the shallow in head first. It's simple, once you understand the fundamentals of turbocharging. There's literally TONS of information on the internet. Don't go by what the forums say, everyone has their experience or their opinion. Go by the facts. Search Google for "Turbocharger Theory". Buy the books by Banks, MacInnes, and Corky Bell. There's also 2 good books from Gator Superchargers, one is called "21st Century Turbo" and one called "Kaiser/Jeep/Willys Super/Turbocharger Book". Both are very informative on carbureted turbocharger systems. I have build thousands of turbochargers, and have designed my share of turbo systems. I didn't know anything about boost before I started working at a turbo shop, but everything started to soak in after I understood the basics. Good luck.
I understamd the basics of turbo charging, the BOV flamethrower was just an aside which would be really cool is it worked but in reality wouldn't work in a safe manner. The whole draw thru idea comes from four basic things: A. I don't have the money for a blow thru carburetor B. Draw thru turbos can be reliable if set up right; look at the factory draw thru turbos C. I want it to look completely old school (I got the idea from an old ad I saw for a draw thru turbo setup from the late 50's or early 60's for what looked like a 235 or 261) D. It's not like a bone stock 250 needs a turbo system capable of making 1,000 hp I'm just looking to try and hit about 200 RWHP so I might be able to break a 15 and not have to put my tail between my leggs every time I hit a light next to a civic with an ass tube muffler, coffe can tip, 10-1/2 inch monster tach, park bench for a wing, some chicken wire for the grille, painted like the trix rabbit shat on it, a cold air intake yo, and some teenage suburban middle class eminem imposter playing like he is in the movie the fast and the furious Route 2 drift. I HATE those little moose knuckle brats. "I wanna be cool and have my whip sound like a CR250 yo!"
You dont "need" a blowthrouh carb if you put it in a box. as mentioned do some reseach one could go on and on and on...... as said factory carb wet draw through setups werer 78-83 Buick Regal ,century, Chevy Monte carlo 231, Pontiac 301 and dry draw through 84-5 Buick T-Type ,GN
It looks like you got the answer you were looking for on the draw-through turbo setup, and the answer you weren't looking for on the BOVFlamethrower- ha ha. I'd try to find a carbon seal turbo in a Pick It Yourself junkyard, and try it out.
http://static.summitracing.com/global/images/instructions/pax-1001839(2)1.pdf instructions on page 17 how to make a boost referenced fuel pump. you can make your own carb hat or spectre offers an inexpensive one. honestly though, budget and turbo dont really belong in the same sentence, but it can be done as long as you dont get greedy with the boost later on. read this forum alot, and pay particular attention to the carburetor and junkyard tech sections.http://www.theturboforums.com/smf/index.php I vote for blowthrough as it isnt really as complicated as some make it out to be. Studebaker had a handle on it back in the 50's. http://www.1956goldenhawk.com/superchg.htm
I am going for the Buick turbo and am going to make an adapter plate and mount plates to put the turbo in top of my intake and have it discharge thru a downward elbow into the intake making the distance as short as possible. For the carburetor I am going to also make an adapter plate because me and Quadrajets don't get along well and the stock Buick carb is a feedback type anyway. I had friend whou had a paxton on a SBF and he was running a pressure box and he had such a hard time tuning it because he had to remove the box to do anything and the box always leaked. We estimated he would have to reseal it about every 5 passes. Plus not exactly the look I am going for. A true old school ride is at least 75% visual impact (example, the fake olds valve covers with the wire looms to put on an SBC with vortec heads, not period parts by any means, wire loom part probably lot more of a PIA than regular wire looms and valve covers don't allow for oil fill, breather, or pcv even so they probably won't be as beneficial to the engine or end user either but who doesn't think they are cool as hell and want some because it just gives that old school flavor. Even if no one will ever believe your 350 is an Olds Rocket engine just because the valve covers say so, those valve covers are totally bad ass.) Since I am a hot rodder and not a racer I just want to drive the car, have it look kool, and not have to play pit crew every time I want to take my son to get burgers and ice cream, so I will elect to skip the box. I'm kind of stuck on the draw thru because that is what I had seen in period ads and will (when I can afford it) probably go with a side draft carb like I saw in the ad. Wish I could find that damn mag with the ad and post a pic, it was definitely old school and different.
all you need is carbon seals in your turbo. no blow off valve on draw throughs. its not that hard to do and can be built rather cheeply. here is a pic of my draw through project.
Turbonetics now owns the entire RayJay line. Its easy again to get the turbos and rebuild parts, but they are old tech. I bought a rebuild kit for my 301EE a year or two ago from them. I personally would go with a Garret GT series turbo these days. They have a more efficent compressor design than the older turbos.
The vdub is sweet. The Stude is bad ass. I am impressed with the ammount of good info I have gotten from the experiences others have had. I am pretty fired up about the turbo idea. A friend of mine just gave me a rock crusher with flywheel and bell housing that he had left over from and engine and trans combo he acquired for his 63 pu. On the inliners site, some one informed me that Trail Blazer and Explorers have rears that are about the right width for my car so with that being said I am on the prowl for a rear so when I grenade my stock drive line I will be ready to go.
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