fly_nitro_rc

I am currently machining my turbocharger for my MDS .68 two stroke. After reading multiple forums about supercharging in particular, it seemed that everyone had an opinion, but no-one had proof. So its about time to get some real answers out here. Yes, i do know the difference between turbocharging and supercharging, however i am building a TURBOCHARGER. I designed it myself and it is about 95% complete. Its made completely out of aircraft quality aluminum which i have hand machined. In fact the last 2 out of the 12 parts i have left to do, are the steel turbines which i am using a 2-axis CNC machine for. I hope to get some pics on here soon, but for now all i have is words.

Also- for all the people who believe 2-strokes cannot be supercharged or turbocharged-
Although the intake and exhaust ports ARE open at the same time at the bottom of the power/exhaust stroke, there is a way to create boost. First you need to create backpressure- or basically and exhaust restriction. If pressure is high on the exhaust side, pressure is able to be just as high in the combustion chamber. The extra air and fuel igniting creates much more power than the reduced exhaust flow takes away. So there it is- a RC turbocharger.

I will make sure to post again once it is running, to make the other unbelievers believers of this truly awesome turbocharger.

8178

My Feedback: (17)

Is the carb going to be upstream or downstream from the compressor section?

The Ghost

I seen a couple of engines that were turboed and supercharged in a model mag in the early 80's. Some one in England done them and were realy strong runners. GM run turbocharged 2stroke diesels and thay don't have any problems. Good luck with it.

Cheers

daveopam

My Feedback: (9)

Nitrous would be a lot easier to rig up with the same outcome. There should even be some weight savings with the nitrous system.
Even so it sounds like a great project. Look forward to seeing your results.


David

Newc

Detroit Diesel - previously part of GM - does make two-srtoke engines and they have been successfully used for buses, boats, etc. though less so today due to emissions requirements. However, that two-stroke engie is a whole different animal from ours. The most obvious difference is the that DD engines use exhaust valves which we don't have on our models.

fly_nitro_rc

The carburetor is downstream (im not really sure how else it would be). The reason the turbocharged two-stroke diesels ran great is because of there reed valve system. This eliminates the intake and exhaust valve from being opened at the same time. However i am still hoping mine would work fine. Nitrous would be pretty cool, but for now i am making just the turbocharger, and i like the turbo because it doesnt cost anything to use it -except the extra fuel .

Today i transfered my program from Mastercam to the CNC machine and i plan to machine the turbines tommorow. Like i said, these are the last two pieces to machine yet, so it will be running soon.

daveopam

My Feedback: (9)

I was thinking about your project at work today. How are you going to lube the bearings in the turbo housing? On a model engine like we use I would think you need a dedicated oiler.


David

Countryboy

My Feedback: (25)

Being a 34 year Auto Technician also ASE Master Certified, and knowing the complexity of a turbocharged system, I can't wait to see the outcome. For your sake, I hope you can make me a believer!

In your design analysis, what kind of boost pressure are you expecting to produce, and how do you plan to control that boost pressure? What rpm is estimated for the turbine/compressor blade's to produce calculated boost pressure?

At this point....just call me skeptic.

bigchap

sceptic

65 Chevy

My Feedback: (1)

I have thought about supercharging (compressor or positive displacement pump) several times. I even attempted to build one based on a roots system. My micro machining skills are what ended those. I turbo system HAS to be much more complex and difficult to build / machine without getting to be too big.

I am watching with great interest. Good Luck. When you perfect a working model, put me on the list to own, test and help develop.

APIA

I work on full size airplanes for a living and read your post with interest. Turbo's are basically FREE horsepower. I am with daveopam, providing ample lubrication will determine the longevity of your turbo.
-Tom

Countryboy

My Feedback: (25)

I will make sure to post again once it is running, to make the other unbelievers believers of this truly awesome turbocharger.

fly_nitro_rc

I may be dead & gone by then. You have my interest peaked....let's see some pics of those machined parts!

No need to wait to share your enthusiasm in this project. I'm almost certain that other's are just as curious as I.

shag555

Mr. Turbo made a system for Polaris snowmobiles. It was fitted to a 700 cc twin, which stock made ~125 HP. With the turbo, it output 180 HP. Polaris twins are reed valve inducted, and with the turbo system it was extremely finicky in getting it to transition from idle to full throttle, especially under temperature changes.

Good luck with it, I wished I had a lathe and mill to do what you're doing. I'd be building all kinds of stuff people said couldn't be done.

MPB

Villa

To Fly Nitro RC... You state:
"Although the intake and exhaust ports ARE open at the same time at the bottom of the power/exhaust stroke, there is a way to create boost. First you need to create backpressure- or basically and exhaust restriction. If pressure is high on the exhaust side, pressure is able to be just as high in the combustion chamber. The extra air and fuel igniting creates much more power than the reduced exhaust flow takes away. So there it is- a RC turbocharger. "

That high pressure you refer to in the combustion chamber is due to the exhaust not being able to leave. It re-expands and reduces the amount of fresh oxygen that can enter. Less oxygen less power. What am I missing?

Villa

To the Gost....As I recall Detroit Diesel does have turbocharged 2 cycle diesel engines. The engine also has exhaust valves. But the biggy is that the engine also has a Roots Blower for blowing out the exhaust gasses and charging the cylinders with boosted air. I could be wrong on that, it has been 30 years. Anyone have a more recent memory?

w8ye

My Feedback: (16)

Where are the pictures? Lets see some picture of your great project?

Enjoy,

Jim

daveopam

My Feedback: (9)

The old detroit diesels were a combination of two and four stroke tech. It has four exhaust valves in the head and ports in the bottem of the cylinder. When the piston was at the bottem the ports were open and the exhaust valves would also open. The boost would blow in the fresh air and push the exhaust out.As the piston went up the ports would be blocked and the valves would close. Once the air was compressed the fuel would spray and combustion kicked a**. An old truckers saying went"you know a detroit is running good when it's leaking oil". It leaked because the crankcase was full of boost.

David

Flypaper 2

Rebuilt a lot of 2-71s and 3-71s back in the 50s and 60s They were a great stationary engine.

Villa

fly nitro rc......Yours is a very ambitious project. A turbo charger is one of the more complex pieces of machinery I have ever seen. Please keep us informed on your progress and results. As I recall, the compressor outlet will be around 300 degrees Fahrenheit or maybe a little higher. Are you planning to aftercool? Maybe it is called intercooled.

fly_nitro_rc

Sorry for the wait on the responses- Ive been quite busy with school and the final steps till the turbo is done. I did finally get one of the turbos machined (i need to know how to post pics on here, also i would have pics ready but the camera batteries died.... i'll try again tonight). I machined the exhaust turbine on our 2-axis at the school, and it is made of steel. The steel took longer to machine than i figured, but i used only a 1/8 bit, so i couldnt ask it to do too much.

other good news- I got a real test run today finally!! I installed just the exhaust turbine and shaft into the turbo housing, and first used a dremel to test how well it spun. It spins perfectly on the ball bearings and actually took quite a while to finally come to a stop. After that i re-installed the turbo to the engine and started it up (-took a while to start because its only 15 degrees here). Although there was no boost from it yet (no intake turbine done yet), the engine had no problem getting it up to speed. When the engine ran out of fuel the turbine stopped spinning about 30 seconds after stopped- about twice as long as when it was spinning on the 35,000 rpm dremel. Maybe i did really get that magical 70K rpm.

Well anyway, I hope to have some pictures very soon once i figure out how to post them. I'll keep everyone updated on the progress.

fly_nitro_rc

I guess while im here i'll answer some questions you had....

in reply to DAVEOPAM: the bearings stay oiled from the oil that is unburned in the exhaust gasses. I gave the oul plenty of room around the shaft to reach the bearings. By the way the shaft and bearings i am using come out of an XMOD rc car you can buy at radioshack. They are the only small shaft/bearings i can find around here.

in reply to COUNTRYBOY: the RPM's i will be getting are whatever i get. I dont know any specifics on that type of stuff at all. but i hope they will be as good as i am hoping.

in reply to APIA: if my bearings do burn out which i doubt they will i can just go down to radioshack and buy another pack for $20.00

in reply to VILLA: the exhaust will still leave the combustion chamber except for a little bit which will stay behind- same as in a stock engine. I am just hoping the high pressure outside from the exhaust leaving will also cause i high pressure of air entering.

in reply to VILLA: an Intercooler (Inter- because it happens before the turbocharger) would be a cool thing to make, but since i am doing this only in school, it is just another week and another wait, so i dont want to do it. I also am thinking that it wouldnt do nearly as much as an intercooler on big engines would. It still would be pretty neat never-the-less.

Topgun2mo

My Feedback: (45)

At least 25 years ago I read an article in one of the r/c boat magazines where a guy machined a turbocharger...I think it was for a K&B engine. I was very interested and made phone contact, but what he didn't tell in the article was that he couldn't control the boost and the boost pressures would skyrocket and he was popping off the heads of the engines. Are you going to have some sort of method to control the boost..some sort of makeshift wastegate?

Thanks

fly_nitro_rc

i didnt think i would ever get nearly that much boost. But if i do, i might need to machine a small wastegate.

fly_nitro_rc

I tried to post a pic of my turbocharger, and it said it had. But now when i checked the site it wasnt there. Does anyone know how to post pics?

Countryboy

My Feedback: (25)

fly_nitro_rc,

PM sent in regards to the pics.