ESE's works engine tuner

[SwePatrick]

I worked on the assumption that more volume was better and even more volume would be better still. I have no idea of how much crankcase volume there is now, it must be more than most. I will have to measure it next time the motor is out of the bike.

My motors breathing development is becoming very dependent on the suction action of the pipe.

Attachment 334496 Attachment 334495

Yes, they will be very depending on the pipe.
Thereby also quite 'variable' in power.
I hade HUGE volume in case due to ~20mm spacer under cylinder because of downstroked crank and long rod.

This made it very sensitive to heat in pipe, one dynopull without 'perfect' heat could result in 48hp at the wheel.
Another with bullseye hit with temp in pipe could result in 66hp at the wheel.
No adjustments made at all.

I found it very 'hard' to reach temp also with methanol as i am running.
Therby i figure that make the engine less depending on the pipe would make it produce more heat to the pipe, and thereby the pipe will start it´s action easier and faster(important in dragracing, one need full power immediately when releasing the clutch.

And, i also figuring that with the lower crankhousecompression the more risk it is to get exhaustflow into transfers, it will be very sensitive to backpressure in pipe.
Mine were a little bit dark greyish in transfers and crankhouse(soot), and i also needed very big stingerdiam to get it to produce power.

I´m redesigning this as we speak, more crankhousecompression and a milder pipe, even still a very angry pipe it is somewhat milder then my previous one.

Rgds

[TZ350]

.
Very interesting, what you say makes good sense.



We are close to getting this bike going, it has the same basic engine as mine but with a smaller more traditional crank case volume, it will be interesting to see how it goes on the dyno and its drivability on the track.

[Nath88]

I found it very 'hard' to reach temp also with methanol as i am running.

The snowmobile guys have a similar issue, they use ignition retard to heat the pipe before launch. Look for 'holeshot button', 'hot pipe button' or 'dragon button'. The ignition retard limits the RPM at wide open throttle so the clutch does not engage. The idea is to hold the button, hold full throttle, release button when you want to go, RPM goes up and the sled launches with a hot pipe.
In your case you could have the ignition retard controlled by a clutch switch. And you get to keep the angry pipe!

[Muhr]

This made it very sensitive to heat in pipe, one dynopull without 'perfect' heat could result in 48hp at the wheel.
Another with bullseye hit with temp in pipe could result in 66hp at the wheel.
No adjustments made at all.

That’s more den fascinating are we talking 20-50 C°?

[TZ350]

it's easy to take a standard T port cylinder from a MX bike or std RS125 that has like 190/195º exhaust and raise it to 200º by doing a good round chamfer raising the port 1/1,5mm.

The thing is if looking at cylinders from factory that come with 200º we don't see that chamfer, it's mostly straight plain duct on the roof, 1min in paint .....



Doing this helps keeping duct volume low, the return pulse gases can follow this chanfer if big enought, or maybe not.

Would this need a dyno to confirm or is safe to say that will not be has good has a normal 200º port...

It sure will keep the duct volume small, which is always a good thing. And the radius will help both the outflow and the return flow, but the positive effect on the return flow will be small; keeping the return flow attached over the port edge would require a much bigger radius.

I'd rather say that it is better than a 'normal' 200° port, if only because you can always modify that radiused port into a 'normal' port, but you cannot modify it the other way round.

If you are lucky, the modification effect will be strong enough for a seat-of-the-pants conclusion. But then you still won't know just how big the effect was.
So, if you have access to a dyno, use it.

That is very interesting.



On my Suzuki GP/NSR 110cc hybrid I radius-ed (chamfered) the front edge of the RC valves.



And set the fully open exhaust port timing to 200 deg duration.

When running it up on the dyno I got a noticeable improvement in top end power when the RC valve was lowered a bit so that the radiused edge was exposed making a rounded entry into the exhaust port. This gave a few more rpm over rev and made more power than a fully open port.

Without taking the motor apart again I can't tell what the exact timing numbers are but suspect they are much like RomeuPT's diagram.



This is not my NSR cylinder but it shows where I radius the RC valve.

[Vannik]

I did the same on a NSR250 used for racing but also built the valve halves up with brazing and filed them to get a much better fit with smaller pockets and hopefully better flow. Well, it seemed to work well, the bike dominated the championship.

[TZ350]

... also built the valve halves up with brazing and filed them to get a much better fit with smaller pockets and hopefully better flow. Well, it seemed to work well ...

Yes there is quite a bit of a gap at the sides of a NSR RC valve. I have been looking at it but it looked very difficult to get the re shaping of the RC valve right after building it up.

Because its very fiddly test fitting the modified valve as its filed to shape. I had been thinking of getting an un-serviceable cylinder and cutting it horizontally across the exhaust port top so that access to the RC valve pockets is much easier.

Great to hear that building the valve up to close the gap on the sides is worth the effort.




Building up the sides of the RC valve will be my next tuning move when the engine is apart again.

[Matt@TYGA]

Building up the sides of the RC valve will be my next tuning move when the engine is apart again.

This mod if definitely worth doing. When I raced the NSR back in '95/'96 I spent an excessively long time welding and grinding the valves for a pretty much perfect fit in the recess.

I'd previously done the same mod to the old '93 model NSR150R, which has a single flap valve, and this had shown a marked improvement at the top end compared to the stock valve rattling around, so it seemed rude not to do it to the 250.

Matt.

[Jannem]

Is there a rule of thumb about C-port sizing relative to A&B?

I'm working on a stud limited, single exhaust small cylinder and and it seems I need to max. out the transfers without cutting into the blowdown. If my calculations hold any water, the transfer area would be the bottleneck even without considering the less than ideal shape of the ducts. I have room to cut the c-Port area quite a bit bigger, but wondering if there's a balance of getting more appropriate total area vs. losing scavenging efficiency. In a much less than ideal situation like this, which way to compromise?

[Frits Overmars]

Is there a rule of thumb about C-port sizing relative to A&B? I'm working on a stud limited, single exhaust small cylinder and and it seems I need to max. out the transfers without cutting into the blowdown. If my calculations hold any water, the transfer area would be the bottleneck even without considering the less than ideal shape of the ducts. I have room to cut the c-Port area quite a bit bigger, but wondering if there's a balance of getting more appropriate total area vs. losing scavenging efficiency. In a much less than ideal situation like this, which way to compromise?

Pictures, drawings and dimensions might help, Jannem.

[Jannem]

Pictures, drawings and dimensions might help, Jannem.

I'll put more effort into it and collect more comprehensive info.

[SwePatrick]

That’s more den fascinating are we talking 20-50 C°?

About 70-100celsius off resulted in HUGE powerloss.
It produced best power at 470-480c

And watertemp at the same time should also be quite hot, about 85-90c

Two parameters that had to be in the ballpark to get it to produce power.
And, when all was good, i could open the powerjet half a turn and it gave me about ~3hp also(at crank).
If opening to early the engine never got hot, also pipe never reached correct heat.

[Muhr]

About 70-100celsius off resulted in HUGE powerloss.
It produced best power at 470-480c

And watertemp at the same time should also be quite hot, about 85-90c

Two parameters that had to be in the ballpark to get it to produce power.
And, when all was good, i could open the powerjet half a turn and it gave me about ~3hp also(at crank).
If opening to early the engine never got hot, also pipe never reached correct heat.

Ok, and 90 degrees water temp never heard about anything like that.

[SwePatrick]

Look at Harley dragbikes, they don´t even have cooling on the liners.
And top methanol engines (V8) have solid blocks, no cooling.
No need for any cooling.
On need to vaporize the alkohol, and the homebrewer knows that a magic number is 78.3c
But you need some more heat due to there isn´t a lot of time to do it

[Muhr]

If anyone thinks it's interesting

It's getting closer to something, it's just the hard one left! To make the best.