psychorevo

Sorry for the repost but one of my friends put in an order yesterday for his Jato.

I'm kinda interested because I'm addicted to speed. I know people say these don't work and are a waste of money but man, how sweet would it be....

Is it worth 179?

If I'm bored, I'm gonna do it and mount it on one of my trucks just as a show and speed demon(quater mile and drag racing).

bauerbach

wouldnt a bigger motor be easier/cheaper/more reliable?

DadtoaMarine

You are going to get some people on here that will start to yack about how they cannot work in ported two stroke engine. Once they produce that degree in mechanical engineering than you can start listening to them. Until then tell them to prove why they won’t work. The simple facts are that all engines are air pumps and anything that will force more air into the cylinder will increase an engines performance. In the case of these superchargers, which are designed to increase the intake pressure by speeding up the incoming air, they should work without to many problems.

If you want some way to prove they work just put a compression tester on the EXHAUST manifold WITHOUT the supercharger installed and start the engine. Idle the engine and wait for it to die and record this reading. Now hookup the supercharger and start the engine again with the compression tester installed on the exhaust manifold. Idle the engine and wait for it to die and record this reading. The difference between the two readings is the amount of boost your supercharger is adding to the system.

Why put it on the exhaust side, because unlike other engines these little two strokes do not have secondary ports to read boost or vacuum. Also you cannot simply put the gauge in the glow plug hole as you cannot turn over the supercharger fast enough by hand to have a measurable affect on the reading.

Now then this leads to the second and most often overlooked part of using a supercharger and that is the exhaust system. Just like any air pump what goes in must come out. Using a stock exhaust pipe will seriously limit the performance of the supercharger. Try to find one that has the largest stinger you can get a hold of. I would even experiment with a pipe that doesn’t use a reversionary chamber or with one that is as large as possible. The more backpressure the pipe has the less effective boost the supercharger will putout.

Hotrodhawk

If any thermodynamic guys pipe up I'll listen, till then I'll just watch all the blistering fast two stroke snowmobiles running boost (turbos) and say: more air in = more air out= HP in any thing with pistons be it 4 or 2 stroke or heck even wankel rotary motor are sick on boost

SkylineGTR

its not they dont work. its a matter of if there cost effective. they will add a little somethin, but for the price they charge for them, your better off just gettin a bigger, more poewrful motor, and having it modded. why spend on that what you would a TM323? its just not effective for the price. when they get affordable, im sure people will use them more, and they will be developed more to give better performance, but as of right now, there insufficient for the green it takes to throw one on, my 2 cents.

MBX5T Maniac

My Feedback: (-1)

I agree. The supercharger may add a boost in performance, but a TM323 installed will whip a TRX 2.2r with the supercharger anyday, and it only cost a bit more than the supercharger. So how about it? Having two engines, and one is far more powerful than you can make the other, and only a bit more than the supercharger. Now the supercharger on the TM323, that would be cool.

dustin7837

My Feedback: (1)

Since your buddy is getting one why don't you lay the arguement to rest for us. I would be interested to see how effective they are as well.
Have him tune up the unit its going in and test the accel and top end. Then once it's installed do it again.
Times and video would be perfect.

??

Bria1

A guy I work with has a T-maxx with a .21 and a supercharger. He said the supercharger made a big boost in performance, but he can't get it tuned for anything. If it is tuned so it takes off good, it is way too lean on the upper end. If it is richened up for the upper end, it loads up in a second when he lets off the throttle.
In my opinion, it sounds like a good idea, but not worth the headache.

DadtoaMarine

quote]A guy I work with has a T-maxx with a .21 and a supercharger. He said the supercharger made a big boost in performance, but he can't get it tuned for anything. If it is tuned so it takes off good, it is way too lean on the upper end. If it is richened up for the upper end, it loads up in a second when he lets off the throttle. [/quote]

This exact same thing happens when you toss a big displacement roots type supercharger on a large CID engine and do not change the exhaust system to match. You have got to setup the exhaust to match the intake. In your friends case it sounds like he is either running a two chamber tuned pipe or one that resonator is just too small for the supercharger to be effective over the whole RPM range. He should also experiment with changing the length of the fuel spray bar so that it rapidly enriches the mixture from midrange on.

Also, I agree that putting one on is not the most cost effective means of gaining performance unless you can change it from engine to engine (Say if you burn up this one can you put it on the next?) If the answer is yes then it could pay for itself over the life of a couple of engines. And finally there is the cool factor that you just cannot ignore.

I have a question for those that have seen one of these systems in use, do they make the famous supercharger whine or are they like a pro charger that says nothing until it is in the upper rpm range?

UF DUB

there is some power to be had by adding a supercharger. this is due mainly to the fact that a naturally aspirated 2-stroke engine has a harder time breathing at high rpm and must rely on aggressive timing and large ports to flow the necessary air. a supercharger can help in high rpm breathing by forcing the air into the engine. however, the air in the engine will NOT be pressurized. the exhaust port is open when the intake port is open, so any pressure from the supercharger is forced out the exhaust. as a result, tuning is difficult because fuel and air are forced out the exhaust at all speeds. its easy to see this if u think about how our little engines work, the ports are open at the same time. as the piston goes up, it closes the intake port first, and then the exhaust. there can be no pressure due to supercharging, only a cleaner charge and easier breathing at high rpm.

bauerbach

that benefit may or may not be negated by the load placed on the engine to create the positive flow.

UF DUB

i agree, i wouldnt put a supercharger on these engines. the marginal gains (if any) just arent worth it. 2-strokes arent designed to have forced induction. i would go with another engine for more power. besides the cost, the supercharger is harder to tune and may never run right. all of the people i have talked to who have bought one and tuned it said they are worthless.

DadtoaMarine

I don't want to start a flame war here but this is where the difference between gear heads with real world experiences and the understanding of the mechanics involved in building internal combustion engines depart for those that just read threads. You see ever single pushrod engine built for the last 50 years use some form of valve overlap (the condition where BOTH the INTAKE and EXHAUST are OPEN at the SAME TIME) as a means of cleaning the cylinder of exhaust gases. This simple fact does NOT prevent a supercharged from working. In fact it is the degree of overlap that gives a high performance engine that deep thump, thump, thump sound at idle.

You don’t have to believe me, read about how it works here: http://www.compcams.com/Technical/TimingTutorial/


Though it is true that the piston closes the intake port before passing the exhaust port it DOES NOT mean that there is not pressure left in the cylinder. Without trying to give a physics lesson you have to take into consideration the two different properties of the two completely different kinds of gas that is being developed by the engine. To put it into short terms the exhaust gases are less dense and have a far greater temperature then the incoming fuel. This means that they have a lesser resistance to flow and will exit the exhaust port first. The greater pressure created by the supercharger will only go to help this process out. Then of course there is the simple fact of the speed at which things occur.

Once again in short, the incoming charge, though over pressurized, cannot travel faster then the speed of the piston which means that the piston will close and trap the fuel charge in the cylinder before it has a chance to escape out the exhaust. And then there is this little thing about these two strokes that is called reversionary exhaust tuning. Basically this incorporates a specially designed cone that is placed in the exhaust that aids in keeping the cylinder pressure in the cylinder (this is where the term tuned pipe comes from). Which is why I explained in my pervious post that you must change the exhaust to get the most from the supercharger. A reversionary pipe that is to restrictive will cause a supercharged engine to run to rich on the bottom end and to lean on the top. On the reverse side one that is to open will lean the engine on the bottom and over richen on the top. You can compensate for either one of these two conditions by increasing the exhaust length, size, or by changing the intake jetting (in other words the spray bar in the carb).

Now then if you desire to contradict what I have just said start posting the physics involved in your argument, otherwise just accept the fact that they do work and leave will enough alone.

bauerbach

lol do you sell them or something?

first you compared to a real engine that has an overlap. thats not quite the same thing is it?


"I don't want to start a flame war here but this is where the difference between gear heads with real world experiences"
if they DO work, you want to post some data?

I mean, proof is in the pudding right? we can discuss theorys and physics till we're blue in the face. but if they do what you say, the data should be pretty easy to locate or produce, no?

Hotrodhawk

Thank you thank you Someone that also knows about overlap and related effects
Check out my "other" toy
Its just your avarge 90 octane pump gas with a 250 shot of nitrous highway cruiser/racer
http://www.hotrodhawk.com/third.htm or http://www.hotrodhawk.com/third_stag...d_pictures.htm
you want to go into overlap talk...hahaha enjoy

DadtoaMarine

The Physics of Gas 101


1. The lighter a gas is the easier it flows
2. The hotter a gas is the more pressure it will exert
3. A lighter and hotter gas has less resistance to change then a cooler gas
4. Sound will travel slower and with less pressure through a lighter atmosphere and faster and with more pressure through a denser one.

Has the cooler and heavier intake charge enters the engine it helps to force out the hotter and lighter exhaust gasses. Has the exhaust travels through the tuned pipe part of the sound is reflected back into the cylinder forcing the intake charge back into the engine. It is that simple

RC 2 stroke exhaust 101

1. Has the piston moves down on the power stroke it uncovers the exhaust port.
2. Hot exhaust gasses start to escape through this port creating a negative pressure in the cylinder
3. The piston then uncovers the intake port where the pressure inside the crankcase forces the intake charge into the cylinder
4. Has the exhaust gasses pass through the exhaust pipe they meet the resonator which forces part to the sound waves back towards the exhaust port. This has the same effect has putting your thumb over the end of a garden hose and creates some back pressure inside the cylinder. This effect helps keep the colder and denser fuel charge from exiting through the exhaust port while letting the remaining exhaust gasses escape.
5. The more pressure created in the cylinder the more residence sound that is created by the engine and the stronger the sealing effect created by the tuned pipe.

Now put this together with what I wrote before and you have enough information to understand why both superchargers and, if produced on the small scale, turbochargers will work on these engines. If you cannot understand it by now then give up and take a few classes on the principles of the internal combustion engine.

DadtoaMarine

a 1.37 60....running a 3.31 rear?

My last full size hotrod was a 1970 496 Donovan by Steve Schmidt Racing. I was getting around 725dyno and 650 rwp through a Carr 700 with 1:1 final. She had a 3.55 9 running 9" streets. I didn't take her to the strip before I sold her but her new owner heading to Cordova this weekend. I hope to hear she has hit the high 9.

bauerbach

real world proof?

I could state a case and back it up with some crazy backwards ass physics to say the world is flat or the sun revolves around the earth. Im not saying your making up physics though; just that the best example tends to be real world proof.

this would include that the benefits by the supercharger outweight the load it places on the enging, and that the units are even marginally efficient to create the situation you describe.

UF DUB

yes, naturally aspirated engines have overlap. in fact, high-rpm, high-power engines tend to have higher overlap, hence the thump thump thump sound at idle (and low manifold vacuum and reduced low end torque), like u said earlier. however, this applies to NA engines. turbo and supercharged engines mostly use cams with high lift and low to no overlap to keep cylinder pressure up. look at turbo grinds and you will see little or no overlap in the cam profile.

dont accuse me of just reading posts and regurgitating what others say. i dont claim to be the smartest person in the world, but i have been a car enthusiast my entire life and i have a mechanical engineering degree. no need to talk down to me.

the piston moves down, the exhaust port opens, exhuast gas exits, the intake port is opened, pressurized intake charge from the crank case flows in helping force remaining exhaust out. then the piston begins moving up, the intake is covered, gas is compressed and is held in by the reversion pulses of the exhaust pipe, and the exhaust port closes, the piston compresses the gas the final amount, and then it is ignited.

the problem is that when the intake port is uncovered and the charge is pressurized by the SC, the extra pressure simply blows out thru the exhaust port, thus losing the boost pressure. the good thing is, the extra scavenging due to the excess charge pressure creates a cleaner charge for compression. however, boost pressure is not realized in the combustion chamber since the exhaust port is still open when the intake port is (and even after the intake port is closed). this is different from a 4-stroke engine.

where some gains can be seen are due to cleaner charge for combustion since the exhaust is forced out under pressure and that it aids in high-rpm breathing since air flow has difficulty keeping up with the open and closing of the ports. the ports open and close so fast the gas has a hard time flowing in fast enough to keep up with the demands of the engine. in a 4-cycle NA engine, this is alleviated by high-lift, high duration cams with larger overlap. but this doesnt simply cross over to 2-strokes.

there is no boost pressure in the cylinder due to SC.

another problem in this situation is the carb. pressurized air going thru the carb does little to help draw fuel out of the spray bar. i realize the fuel tank is pressurized by the exhaust, but that pressure has to overcome intake pressure in order to release fuel into the carb. high velocity air has lower pressure and helps draw the fuel into the incoming air, but there is still pressure due to the SC. as a result, the needles must be set much richer to compensate, and tuning is much more difficult. most SC/carb combos are draw-thru, not blow-thru for this reason (turbo/carbs are different).

if it works, show us some proof. show us some cylinder pressure readings.

i dont mean to flame. just healthy discussion

dustin7837

My Feedback: (1)

Thats exactly what I was thinking while reading the whole thread!

The supercharger will make your fuel air mixture get into the engine faster and will push the exhaust out faster, but will create little to no boost. The only boost you would get is the amount created by the exhaust backpressure.

I guess that means higher max RPM's but no more power being created per cycle.
And although the piston in these things are light, depending on the safety factor that was used in the design of the connecting rod, there is a chance of breaking the connecting rod if the RPM's are increased too much.

EDIT: Does anyone know of a compression tester that will work on an RC engine? Or would you just have to rig one up with some small fittings and hose and a pressure guage.?

DadtoaMarine

For all of you that asked for it here it is:

"Most people overlook the extent to which crankcase pressure and velocity affect small rotary-inducted two strokes. The more you can pack in the crankcase, the more boost it will add to the charge entering the cylinder. The MPPA supercharger increases the incoming air velocity going through the carb and this in turn helps atomize the fuel better in the venturi as it enters the crankcase."

"The MPPA Supercharger disproved the theory that a two-stroke engine couldn't be supercharged. An engine with the supercharger installed on it showed an rpm increase through out the entire power curve."

Displacement: .21ci / 3.5cc

BHP: stock: 2.322 @ 32,851 RPM / Supercharged: 2.598 @ 33,178 RPM

Torque: Stock: 70.416 in.-oz. @ 32,851 RPM / Supercharged: 78.965 in.-oz. @ 33,178

This is from the December 2004 issue of RC Driver.

Look it up for yourself and by the way take a shower to get the egg off your face.

DadtoaMarine

Here is the link to buy the back issue if you like:

http://www.shop4rc.com/shopdisplaypr...er+Back+Issues

RC Driver
Issue 12
12/04

click to see more
December 2004

• Top products, best of '04 - you picked 'em!

• Traxxas Revo - true track test

• Nitro engine overhaul - 10 easy steps!

• Hot Bodies Lightning Stadium Pro - hybrid race machine

• Stuff you gotta' see! Hudy Exclusive set-up system, LRP Pulsar Competition 2 Charger, MPPA Engine Supercharger, Thunder Tiger TTR S3 Buggy

• RC vs. real - Thrasher monster truck

• OFNA jammin' X1 RTR

• GS Racing Vision

• Aquacraft Nitro Hammer

$3.99

supertib

http://www.hostdub.com/albums/avdub/...hargedSH28.mov


here is a video of a supercharged XTM Mammoth......it sure seems to work pretty dam good, as well it does make a very nice whine.......I can say it definitely doesn't hurt performance as i bet this truck wil whip most trucks on the board...

UF DUB

i have that issue. and u quoted the power incorrectly. here are the real numbers:

stock: 2.522@32,851rpms 77.416in-oz@32,851
SC: 2.598@33,178rpms 78.965in-oz@33,178

if u ask me, an increase of 0.076HP and 1.539in-oz is nothing to brag about and doesnt prove that "boost" was realized in the combustion chamber. it is more likely that the overscavenging simply created a cleaner charge. to add to this, the system burns more fuel, the SC adds weight, and it was driven with an electric motor that drains your battery faster.

"Look it up for yourself and by the way take a shower to get the egg off your face."

mature

bauerbach

and so the debate continues.

it would definitly come down to who has the numbers right. cause if it is the latter, thats pretty darn insignificant.

for all the theory mumbojumbo, reality has a way of rearing its ugly head of inefficiencies.