Turbocharged Traxxas Nitro 3.3
 

Ive always been interested in turbo charged 2 stroke engines ever since I found out about the turbo snowmobile kits.

And with everything I know about 2 stroke nitro engines I believe its possible

This is my plan.

I plan to use a keychain turbo on a traxxas 3.3, un unsure it it will actially boost the engine but if I can get the turbo efficient enough it might have a chance.
After studying 2 stroke turbo exhaust designs ive fond they run them off the stinger to avoid the turbo effecting the scavenging as the exhaust gas passes the expansion chamber and the back pressure shock wave

here is the key chain im planning to use

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http://youtu.be/thsAKbE_dDc

The bore of the turbo exhaust housing was cylinder shaped and the hole for the exhaust intake did not transition into the housing very well. So I've smoothed that and re shaped the housing to direct more flow around the impeller

Ie. I Dremel'd a tapered channel around the housing. To get the gas swirling around the housing and impeller....

It's made a big difference... There is a noticeable rpm increase and is a lot less restrictive when blowing through it....

ATM I'm currently making a flange plate and dump pipe for the back of the turbo.... Out of a washer an a old HengLong alloy BB gun barrel.

My biggest focus is to be able to get the turbo to spool so I'm paying the most attention to the exhaust side. My plan is to see it the turbo will effect the running of the nitro motor before plumbing it into the carby.

and here is the test for a dump pipe.... but that has been removes as it was to restrictive. I might use a old header for the dump pipe

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but I'm still yet to get the engine of my buddy

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I didn't like my chances of turbocharging a nitro with its primitive carby espically with a blow through method, so ive been toying with the idea of a draw through setup.

a dump pipe would be fitted to the back of the turbo and the stinger would be plumbed into the side port

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Now for the fun part.... I need to find an exhaust that will get the stinger as close to the turbo as possible. And nearly all the traxxas pipes are L shaped and I need a U shape one....there is the 3.3 tmaxx pipe but I don't like the way the muffler bends down

You can always make one out of a Coke tin and some brass tubing. Gets you a real deep sound. :)

he he he now that would be cool.... but.... what about using that method to make a muffler after the stinger on the back of the turbo to quieten it down so u can here the turbo spooling better? :)

hows ive been thinking those RB super chargers are floored. and the same with any blow through carby on these primitive engines.

lets say we have a blow through carby setup on a nitro engine right, At wide open throttle and high RPM.... how on earth would the fuel system provide more fuel for when it comes onto boost?
if anything its going to increase the air pressure around the throttle plate and the jet, slowing down the fuel flow. The only way would be to richen the HSN but doing that will effet the LSN setting and will excessively effect the mid range off boost fuel mixture. so the end result will be this thing that idles, and goes flat out, but will have no power in-between.

I wonder if all the past negative review of the RB superchargers is because with that discrepancy in the fuel mixture for the mid power band?

so my theory is... with the draw through method the engine should run with the factory tuning with out any problems off boost. it will just be less responsive because the intake track from the carby to the crank case is longer. but as boost comes on, the air pressure around the throttle plate and the jet should decrease sucking more fuel as needed..... also keep in mind as it comes on boost yes it will be sucking more but as well as that.... im not 100% on this yet, but the exhaust pressure might increase making the fuel tank pressure increase

what about this for a thought?

make a dump pipe from the turbo to a pot of water???? it might quieten it down and act as a bit of a oil trap?

yeah second though... I dont know....

Maybe. I think RB keeps the fuel going into the turbo with that band around the flywheel, which keeps it turning and adding fuel...? Sorry, I don't know much.

I like the idea you are trying...but really doubt that the keychain turbo will work. and im thinking that even if it does make some boost, it wont last a long time. Not sure how hot exhaust temps get, but I cant imagine that the metal the turbo is made out of will hold up very well.
But, id love it if I am wrong!

If you look at the RB supercharger a you'll see a nipple in the outlet of the SC housing. That nipple is plumbed into the pressure line from the exhaust into the fuel tank with a T fitting. It's basically acting like a boost referenced fuel pressure regulator, enriching the mixture under boost. The problem is the fuel pressure isnt as tunable like a fuel pressure regulator in a full size vehicle and some of the pressure from the SC probably goes into the exhaust instead of only pressurizing the tank. To be more effective check valves and pressure regulators would need to be used which adds cost and complexity. If you need or want to experiment with stuff like that look into the check valves and regulators used with fuel pumps in nitro and four stroke planes.

Draw through carbs have the advantage of not being pressurized. However the vacuum signal on the Venturi of the carb varies and can be quite low when the turbo is not spooled. Either way fuel poudling can result in draw through setups. A nitro carb is sealed with o rings which should be fine on a Blow throw setup. The only potential problem is boost pressure leaking past the slide and out the bellows. The vacuum signal on the Venturi will be greater so atomization and fuel metering will be better as well. I think a blow through setup is your best bet.

Who knows?? But I don't think there will be any durability issues as the oil in the exhaust will lubricate it and been made out of alloy it should be as heat resistant as a alloy crankcase or cooling head.

check out this one..
http://youtu.be/JUt2n9NgGAQ

Cheerz...

hey just thinking with that reference port on the superchargers wouldent it bleed off exhaust pressure at idel potentially effecting the fuel mixture?... I think, that line would be in need of check valve.

Thats ts something I've been thinking about doing with mine but I want to try with out a reference line first.

I would of assumed that the vaccume signal off boost with the turbo not spooled would be about the same as a N/A motor??
I don't understand why it would varie? I mean I know it will varie with different loads and a RPM but that's normal.

im not fully understanding how a blow through would have a higher vaccume signal Compared to a draw through
because both are going to have the same air flow over the Venturi so from that aspect they will have the same fuel flow.
but the blow through setup will have positive pressure in the tank and on the Venturi where a draw through setup will have positive tank pressure but negative pressure around the Venturi.

yeah there's all sorts of potential issues with the RB setup. I've never had one, just looked at pics real quick.

You've got me rethinking the whole draw vs blow through thing now.My initial thought was a draw through would place a restriction on the intake while off boost slowing the air going through the venturi. That was my main concern, but even if it poses a restriction I'm wondering how much it will really impact anything.

I'm not really sure about this anymore. In 1:1 I think blow through is better, but 1:1 carbs have power valves, accelerator pumps and other stuff nitro doesn't. Maybe draw through would be better. Before boost it operates like normal and if any boost is made it can hopefully be used to increase fuel pressure. With a draw through its probably not as critical how much fuel pressure rises in conjunction with boost. In a blow through fuel pressure needs to rise as least as much as the pressure rises in the carb or the mixture will lean out. The big question is, how will the boost pressure compare with the exhaust pressure? And remember, even a loss of vacuum counts a pressure change with fuel pressure needing to change as well. Ugh my head hurts! lol

I'd tend to agree, on 1:1 I like blow through because u have the option to run a intercooler but a blow through carby setup requires a lot of modifications to the carby or required the whole carby to be inclosed within a box. In Australia it's very rare to see a blow through setup, the closest thing would be centre point injection on some of the late 80s sports cars. A lot of the 4cyl guys run draw through setups with side draft webbers where the 6cyl and v8 guys run a blow through setup on LPG with a Holley throttle plate and impco gas mixer.

so I can honestly say I have zero experance with blow through carby setups, I have read alot about them in a book I brought a while back "super tuning and modifying Holley carburetors" by Dave Emanual

i really apreatishate the feedback, it really helps having someone to go over ideas with. I get blank looks from my wife when I think out aloud with her.. Lol

Awhile back I did have a idea of a blowthrough setup with some kind of power valve. But I can only imagine how difficult the jetting would be. Who knows some dual inline carby setup where one has a rising rate pressure fuel regulator

I actually started reading up on Blow Through for 1:1 myself not too long ago as well. My dreams of my 1967 Camaro being LS powered with a pair of turbos seems more out of reach than ever. The alternative being I keep the iron lump of a 350 in it and build my own budget Blow Through setup. Boost referenced rising rate fuel pressure regulator, boost referenced timing retard module for the MSD box and a blow through modded carb are way cheaper than the LS swap and new injectors. Since Demon and Quick Fuel have carbs already modified for blow through with Orings on the throttle shafts, modified boosters and accelerator pumps I'd just go that route instead of modifying a carb myself. But there's still plenty to do on the car before I get to that point and lots to do on the house before I can get back to the Camaro.

I'm kinda surprised 4cyl guys in Oz are running draw through, here everyone is fuel injected. But I guess it makes sense when you consider carb sizes and draw through has been popular in rotaries since forever. Besides the last thing you'd want to try is a blow through on a weber! I'll have to check out that book

Ahh, I ment....most guys here are running EFI but out of the guys running carby's the majority are draw through.

he he, so I'm not the only one that's dreamed of some twins on a v8

Well actually I'd love an 8-71 with injection and a 3 hole bug catcher like so many of you Aussies have. But then I'd have to tub the car otherwise it just wouldn't look right! Lol. The Camaro will be a driver though and I never wanted pro street but it's mini tubbed, ultimately with (hopefully) around 650-700hp at the wheels and turbos are the best way to get the most drive ability. It's a basic small block with about 300hp now just to get her running but with a decent bottom end, twins should get me what I want without having to go too exotic on the heads. Just gotta get the more important projects out of the way before I can get back in the garage and fire up the welder again.

Most turbos are EFI here too, draw through seems to be only the old school rotary guys. Blow through is getting more popular here ever since companies making centrifugal superchargers reintroduced it with kits designed not to scare the old school muscle car guys afraid of wiring or tuning EFI. The fact you don't need to put the carb in a box and can buy carbs already modded for it has helped a lot. Btw sorry for the thread jack.

iv done this already ..

i turbo'd a modded bigblock in a 1/10.. runs a full live diff and 4-link

http://www.youtube.com/watch?v=stAOf...ature=youtu.be


http://www.rcuniverse.com/forum/atta...mentid=2020413http://www.rcuniverse.com/forum/atta...mentid=2020414

Hahaha, that's awesome, well done.

Turbo aside that's a awesome achievement converting that old Great Vigor chassis to 4 link rear...

Cheers ..the turbo car is my first 4link build ..every thing is abit over kill and will not fit a body being to large. The carbon bigblock 1/10 is my current build ,built to suit a 200mm touring car body..every thing is scaled down .

http://www.rcuniverse.com/forum/atta...mentid=2020626http://www.rcuniverse.com/forum/atta...mentid=2020627