ESE's works engine tuner

[TZ350]

Is it a rg100 ?

RG150 with a RGV250 barrel sleeved back to 50mm for a 100cc water cooled.

[jasonu]

RG150 with a RGV250 barrel sleeved back to 50mm for a 100cc water cooled.

We looked at that route a few years ago and abandoned it as the KE125/RG400 was easier for us as that build suited our resources at the time.

[TZ350]

Both are hard to do using the GP cases hence the RG150 bottom end ( a RG125 would be better). We were going to go the RG400 way and got a bunch of barrels and heads but gave up on it when YowLing sent us a RG150 engine.

We now have some RG400 heads and barrels to sell or trade if anyone want's to try their hand with one.

[jasonu]

Both are hard to do using the GP cases hence the RG150 bottom end ( a RG125 would be better). We were going to go the RG400 way and got a bunch of barrels and heads but gave up on it when YowLing sent us a RG150 engine.

We now have some RG400 heads and barrels to sell or trade if anyone want's to try their hand with one.

How much pissing about to fit the RGV250 cyl to the RG bottom end?

[TZ350]

How much pissing about to fit the RGV250 cyl to the RG bottom end?

Bolts straight on, rods the problem but YowLing has sussed that.

[jasonu]

Bolts straight on, rods the problem but YowLing has sussed that.

easy pezy lemon squeezy.

[F5 Dave]

You guys will of course be putting the sprocket centerline in the right place to get some anti squat, and keeping the front of that engine up high so the angle wont be too steep with a dead straight rubber manifold holding the powerjet carb.
If the static angle is too acute, the fuel in the bowl can uncover the powerjet entry port - it goes lean and goes bang - been there done that.

Yeah I assumed that they just had the engine sitting there on that pile of firewood a few inches too low.
Ahh - the old fit the carb manifold to the engine sitting on the bench trick! Yes played that game & lost, but just with an engine that emptied the floatbowl of the small carb enough to make it splutter first corner after the straight when the main is sucking (overly short Mikuni button jet) in the air. Fortunately didn't lock up & a curved inlet was hastily added.

[TZ350]

Ok I have shortened the inlet tract by 70mm. Well that's if the theory that reversion happens at any significant change in area is correct. Then reversion should happen now at the V Tec's throttle plate insted of the carb's bellmouth which makes that part of the inlets tuned length about the 135mm Wobbly suggests, and thats significantly shorter than the inlet tract was.

To do this I am revisiting the plenum idea, with an arrangement YowLing suggested to me that allows any fuel/oil that drops out to still be inducted into the motor.

And this also gives me a chance to try the electric power jet carb. Should be finished and ready to run up next week. Hopefully this works as the carb is now tucked in, and well out of the way.

[TZ350]

To increase low end power Wobbly has pointed me towards the Honda ATAC system, he tells me that they had some success with the idea on the BSL500. He sent me this picture and some pointers on where to put it on the header.

Attachment 241414

"As close to the flange as you can, and get the throttle plate as close to the header as you can to reduce the ill effects when its closed at hi rpm......... Wob"

So I am going to try one on the GP

Other Bits and Bobs about the ATAC system that I scraped from the net........

ATAC System: The Honda Automatic Torque Amplification Chamber system works by effectively increasing or decreasing the volume of the exhaust system with a small butterfly valve located just before the exhaust connection.

A few pictures here:- http://www.scooterhelp.com/moto.barrels/honda.cr250.84_85.overview.html

A bit of YouTube of a guy working on his ATAC http://www.youtube.com/watch?v=tY7D0jLcfws

Atac and vtac differ very little. Vtac is a resonator chamber like kips, with only one inlet/outlet where atac is a bypass chamber with a in and out yet it doesn't block the main exhaust flow even when open so it very much acts like a resonator.

Attachment 241367 Attachment 241376



Attachment 241373

All of these designs stretch the vacuum, phase, and pressure waves that bounce back to the cylinder effectively making the pipe act like it has a longer tuned length when the resonator is open and making the pipe act like it has a shorter tuned length when the resonator is closed.

Attachment 241375Attachment 241374

[gav]

Ok I have shortened the inlet tract by 70mm. Well that's if the theory that reversion happens at any significant change in area is correct. Then reversion should happen now at the V Tec's throttle plate insted of the carb's bellmouth which makes that part of the inlets tuned length about the 135mm Wobbly suggests, and thats significantly shorter than the inlet tract was.

To do this I am revisiting the plenum idea, with an arrangement YowLing suggested to me that allows any fuel/oil that drops out to still be inducted into the motor.

And this also gives me a chance to try the electric power jet carb. Should be finished and ready to run up next week. Hopefully this works as the carb is now tucked in, and well out of the way.

Is that a bit of radiator hose you are using? Is it fuel resistant? Maybe try some silicone hoses?

[Henk]

Is that a bit of radiator hose you are using? Is it fuel resistant? Maybe try some silicone hoses?

Been using radiator hose as an inlet manifold for about four months now, no problems so far.

[bucketracer]

There might be some problem with a longish hose collapsing under vacuum when the throttle is closed unless you have a spring inside it like some radiator pipes on the suction side of a radiator have.

[F5 Dave]

. . . .
All of these designs stretch the vacuum, phase, and pressure waves that bounce back to the cylinder effectively making the pipe act like it has a longer tuned length when the resonator is open and making the pipe act like it has a shorter tuned length when the resonator is closed.

Attachment 241375Attachment 241374

I'm a bit dubious about the "making the pipe act like it has a longer tuned length" part of the claims made of these systems. & also of the Powervalve cover aftermarket people who market larger covers (for KIPS chambers etc). I've always assumed that the chamber introduces a volume that disrupts the returning wave when it is out of phase with the required engine timing, ie the ports are open longer at low rpm so the pipe waves are disruptively returning at the wrong time.

It just smacks of an easy to make aftermarket part that the punter can bolt on without stripping the engine down. But if bigger were better, then why didn't the manufacturer make them bigger? Or did they design this & forget to test it year after year? Hmm, didn't think so.

But adding one on from scratch? might be worth a try.

[wobbly]

In the testing I have done, the volume of the resonator chamber isnt critical, once you have reached a certain size.The best place to start is equal to the cylinder displacement, and this will "work" every time.
Fitted to a world champ ski engine, these chambers, operated by a flat, throttle slide plate,added over 30% more power at 1/2 peak rpm.
They seem to work very similar to a PV, in that the pipe effects are dramatically reduced in the area where the wave action is way out of phase with the port.
This is seen in the sim, and on the dyno, in that you can change the pipe dramatically, and it has little effect when the PV is down, or the chamber is open.

[F5 Dave]

Thank you. That is rather heartening to read.

Crumbs, 30% that's heaps. Obviously that engine loved it. I'm assuming a jetski engine is high RPM most of the time & has very strong wave action pipe.