ESE's works engine tuner

[crbbt]

did Honda crush Aoyama's RS? or have they moved away from doing that these days?

[Muciek]

did Honda crush Aoyama's RS? or have they moved away from doing that these days?

Looks like it's in the honda museum

[wobbly]

The rotary valve could be spun either way in that case.
The engine sits with the crankshaft vertical ie rotated 90* anticlock to the pic, and the carb would be also vertically in line with that.
Thus as the slide opens it would flow along the manifold floor to the roof of the port - making no odds as to what side of the port was opening or closing.

[lodgernz]

The rotary valve could be spun either way in that case.
The engine sits with the crankshaft vertical ie rotated 90* anticlock to the pic, and the carb would be also vertically in line with that.
Thus as the slide opens it would flow along the manifold floor to the roof of the port - making no odds as to what side of the port was opening or closing.

Oh. I didn't expect that.
OK, if the crankshaft was horizontal as in the picture, and the carb consequently vertical, which way would you prefer to rotate the disc? Opening from the bottom up, i.e. clockwise?

[ief]

The 1st harmonic of the reed frequency can be up to around 15% less than the peak Hp rpm.
This frequency is reduced by increasing the petal length or decreasing its thickness.
In EngMod you must be careful that the petals do not smash into the reed stops, as this causes easily seen erratic tip
lift from one cycle to the next.
You can still run the thin reeds but move the stops further way.
Intake length is easily seen in that at the rpm you want to tune for, the case pressure ( red ) goes negative at the same time the
carb / manifold / reed reflecting wave goes positive ( yellow ).
This helps open the reeds quickly, as the piston begins to rise.
If the engine 4 strokes in the top end with a reed change, this may signify that the air corrector isnt big enough, or that the main jet is simply too big.
But if the reed frequency is well above where it should be, then you may have a big mismatch with the intake tuning,that causes the jetting to go to hell as well.

Wob, you're golden. Had to digest but I think I figured it out now, tnx!!! None of the above seems at play but my presumption of it being double dipping was just wrong... And my 'main ride' has just the situation to test this I think.

[Muciek]

Does anyone (Wob?) have dimensions of the mufflers for the 125 engines gp or karts? I remember there was one drawing here but was posted not on kiwibiker server and got lost.

[wobbly]

All the GP bikes used mufflers with the perforated core a slip fit over the stinger tube OD.
The tuneability is gained in that mid power is enhanced if the perf is the same size as the stinger, top end is enhanced if the perf is slightly larger
for high speed tracks needing top speed, not acceleration.
In karts there is only 1 choice now - most stingers are around 26mm OD, and there has always been 2 choices of perf size.
The early versions were like GP ones where it slipped over the stinger, but later versions were developed with a 40mm core size.
The stinger U tube is around 300mm long and this, when dumped into the big core size makes hugely better overev power.
The first one I tried increased power at 14,000 by 15Hp,up to 40 from 25.
The newly homologated compulsory mufflers are slightly longer, but all have the big core as its alot quieter as well. so I have lost my advantage
in knowing that the bigger size was better as most used the smaller old version previously.

[41juergen]

Wob, you mentioned some time ago to do a heat barrier coating on the piston crown and the bowl in the head. I know that the cart boys change their pistons more often than their pants.... So if it lasts for let's say 3 hours hard running, all is fine. But for a bike how long will that coating be durable, any experience?

[wobbly]

The ceramic heat barrier coatings I have never seen or heard of it failing.
You only coat the piston in the bowl area, NOT in the squish band - same in the head.

[oldjohnno]

Wow, I've spent the last few days wading through this thread and it really is a wealth of information. To Frits, Wob and all the others, thank you.

Now to my questions; they may well be off-topic and if so I'm happy to take them somewhere more appropriate if someone could point me there. I'm a long-time Bultaco tragic - hardly 2t state of the art I know but I like them and the've served me well and I enjoy the challenges involved in improving inherently flawed designs.

My current project is a Metralla GT with a modified 370cc Pursang engine - Blair based porting, YZ250 reed with rear transfer, Husky 390 head etc. I've just finished building a dyno and should have some power figures in the next day or so. What I'd like to do is run it at Lake Gairdner next year, and with a little work I could possibly run it as a MPF and MPSF (modified production and modified production partially streamlined) in both 350 and 500 classes. Fuel would be methanol as I just don't envisage the air cooled engine surviving for that long at WOT on petrol.

I fully realise that this engine will be severely limited in output compared to modern designs - it's quite oversquare (85x64) which limits available port area with a single exhaust port, four transfers plus the rear, and air cooled. But on the other hand they're a very small, narrow bike with little frontal area, and previous speed attempts on similar machines have shown that they can reach remarkable speeds with quite modest engine outputs. The current records aren't particularly high so I'm not entirely convinced yet that I'm wasting my time... But before I commit I plan to spend as much time on the brake as necessary to prove that it's capable of making the necessary power as well as able to resist melting down at prolonged WOT.

My half-baked plan at this stage is see if a reasonable amount of power (65hp?) can be made with the Bul top end. Failing that I've been looking at some similarly sized but more modern cylinders that could possibly be adapted. One in particular that interests me would be from the Arctic Cat 800 HO engine - an 800 twin that makes 165hp at moderate rpms.

Anyhow I'd welcome advice anyone may have on developing such an engine with limited wall area as well as transfer passages that hug the walls fairly closely. I'm also interested in anything on methanol usage, particularly with regard to temperature control in an air cooled big bore engine. As well, I'm thinking of buying an EngMod2t license - does it model old-style engines such as the Bul effectively?

Here is the bike in question:

[TZ350]

I'm a long-time Bultaco tragic - hardly 2t state of the art I know but I like them and they've served me well and I enjoy the challenges involved in improving inherently flawed designs.

Totally in the right place for that, I love your bike, please keep posting as your project progresses.

[husaberg]

Wow, I've spent the last few days wading through this thread and it really is a wealth of information. To Frits, Wob and all the others, thank you.

Now to my questions; they may well be off-topic and if so I'm happy to take them somewhere more appropriate if someone could point me there. I'm a long-time Bultaco tragic - hardly 2t state of the art I know but I like them and the've served me well and I enjoy the challenges involved in improving inherently flawed designs.

My current project is a Metralla GT with a modified 370cc Pursang engine - Blair based porting, YZ250 reed with rear transfer, Husky 390 head etc. I've just finished building a dyno and should have some power figures in the next day or so. What I'd like to do is run it at Lake Gairdner next year, and with a little work I could possibly run it as a MPF and MPSF (modified production and modified production partially streamlined) in both 350 and 500 classes. Fuel would be methanol as I just don't envisage the air cooled engine surviving for that long at WOT on petrol.

I fully realise that this engine will be severely limited in output compared to modern designs - it's quite oversquare (85x64) which limits available port area with a single exhaust port, four transfers plus the rear, and air cooled. But on the other hand they're a very small, narrow bike with little frontal area, and previous speed attempts on similar machines have shown that they can reach remarkable speeds with quite modest engine outputs. The current records aren't particularly high so I'm not entirely convinced yet that I'm wasting my time... But before I commit I plan to spend as much time on the brake as necessary to prove that it's capable of making the necessary power as well as able to resist melting down at prolonged WOT.

My half-baked plan at this stage is see if a reasonable amount of power (65hp?) can be made with the Bul top end. Failing that I've been looking at some similarly sized but more modern cylinders that could possibly be adapted. One in particular that interests me would be from the Arctic Cat 800 HO engine - an 800 twin that makes 165hp at moderate rpms.

Anyhow I'd welcome advice anyone may have on developing such an engine with limited wall area as well as transfer passages that hug the walls fairly closely. I'm also interested in anything on methanol usage, particularly with regard to temperature control in an air cooled big bore engine. As well, I'm thinking of buying an EngMod2t license - does it model old-style engines such as the Bul effectively?

Here is the bike in question:

I have always loved the Metralla.
Bert Flood used to prep them back in the day and they were hugely succesfull along with the 360s
But you likely already knew that anyway.

[wobbly]

An air cooled on Meth operates very similar performance wise to a water cooled on petrol, so its a match in heaven.
In fact if its done really well,you can exceed the bmep of a watercooled on good octane fuel, due to the jungle juices very high latent heat of evaporation - and not suffer the usual issues of heat induced power fade.
EngMod will model anything well, it all depends upon the input accuracy, so yes your crap transfer duct geometry is fully accounted for as an input variable.
As you have a dyno you can convert the power figures to crank easy enough, and from the peak Hp rpm you actually see, you can then modify the pipe temp
numbers of that setup, as modeled, to get accurate outputs for future improvements in port or pipe designs.

[oldjohnno]

An air cooled on Meth operates very similar performance wise to a water cooled on petrol, so its a match in heaven.
In fact if its done really well,you can exceed the bmep of a watercooled on good octane fuel, due to the jungle juices very high latent heat of evaporation - and not suffer the usual issues of heat induced power fade.
EngMod will model anything well, it all depends upon the input accuracy, so yes your crap transfer duct geometry is fully accounted for as an input variable.
As you have a dyno you can convert the power figures to crank easy enough, and from the peak Hp rpm you actually see, you can then modify the pipe temp
numbers of that setup, as modeled, to get accurate outputs for future improvements in port or pipe designs.

Thanks for that Wob, very helpful. Does it ever get to the point where it overcools and make consistent jetting difficult? I had one engine that in effect had two-speed jet requirements - up to a certain head temperature it wanted a particular jet and timing figure, then beyond that it was like a toggle switch had been flicked and it wanted something else entirely. I'm thinking about running on salt where the first mile or so is basically the warmup, and whether it'll be hard to run cleanly and safely over a wide temp range. I guess I could run a manual powerjet control and adjust according to EGT?

Is it an advantage to run something like a Lectron with meth? Supposedly they emit a finer droplet size than say a Mik. but I don't know if this is true. But if it is perhaps it would help take advantage of the high LHV..

Husaberg and TZ350, thanks for the warm welcome. Bert Flood set some records in the 70s on both his 360 drag bike and a 125 streamliner he built. The 360 did 152mph (and incidentally did low 12s on the strip) while the 125 could only manage 115. I find Berts 360 speed encouraging, as well as the performance of the old 360 endurance racer that won Montjuic. This bike was very similar to mine, mildly tuned to last 24hrs and unfaired, yet still would pull around 135mph. All this was a long time ago, and without wanting to detract from Berts or anyone elses efforts they didn't have access to the tools and knowledge we benefit from today, so I think we could reasonably expect to improve on those speeds.

[TZ350]

Does it ever get to the point where it overcools and make consistent jetting difficult?

Sure can, not difficult, impossible as the motor can run so cold that the Methanol does not completely evaporate and the engine runs lean. Any more Methanol fuel to richen things up only makes the engine run colder and leaner. You can get to the point where there is raw Methanol dribbling out the exhaust and the motor is still running lean, been there done that.

I had a Suzuki road racer fitted with RD barrels that ran methanol and the trick was to blend the fuel so that the engine temperature was high enough to evaporate all the fuel. For my RD/Suzuki the ideal blend was 50/50 Acetone Methanol, I expect that other motors may require something different so you will have to experiment but 50/50 is a good place to start.

Acetone has a higher octane rating than Methanol, evaporates better, a latent heat of evaporation about half way between petrol and Methanol and Acetone significantly reduces Methanols tendency to detonation when lean and Acetone very much helps keep oil in suspension in Methanol blends. Current unleaded pump fuel seems to blend with Methanol so probably worth a try. Sit a sample of mixed fuel in a glass jar for a few days to see if it separates out.

Use Yamabond on the cases, the only issue I had was oil seals, some coped with Acetone others did not. Suzuki crank oil seals worked best, Yamaha Teflon lipped seals swelled up and were useless. Test the seals you are going to use in a glass of fuel for several days. After a days racing I used to run a petrol mix very rich in oil through the motor to clean out the hydroscopic Methanol mix so that the crank did not rust. The richer in oil the petrol/oil mix can be the better the petrol will run with the Alcohol jetting.