ESE's works engine tuner

[2T Institute]

I guess some of that maybe because they are missing that rotary whatawacallit intake thingwajig....

42mm carby

[F5 Dave]

150mm rod.


(I assume we're playing top trumps)

[2T Institute]

RSW 125/250 only went to 115mm rod

[wobbly]

Biggest issue is they aint got a freehundredansixtydegree temperature gauge.

[chrisc]

Speaking of temperatures.

Wob, I got one of your thermostats from Steve Bagshaw which I'm going to fit to my 125. Any sharp leads on radiator hoses and a t-junction for the lower hose, before I go on the search myself?

[wobbly]

Here is how I did it on the TZ400.
Hoses are silicone off trademe,I have seen nice stainless T junctions available from Mico I think.
But hoovering up an alloy one isnt hard.

[husaberg]

Here is how I did it on the TZ400.
Hoses are silicone off trademe,I have seen nice stainless T junctions available from Mico I think.
But hoovering up an alloy one isnt hard.

The Engine there Wob, has it been changed?
It looks piston ported now.

[shnaggs]

Hi there fine gentleman,

I've been a lurker on this site for over half a year, lots of great stuff and great minds on this site...and I thank you for that!

If any of you could give me your input on a few matters in regards to Engmod, it would be much appreciated.

1) when reading the mach index traces on the exhaust, I'm a bit confused at what the numbers actually represent? I am no engineer, but if I see a peak value of .8, does that mean that I am seeing 80% of the speed of sound?

2) I've been trying to replicate the leaning out and retarding Ign on over-rev, to get some more usable power past peak, but when I try to simulate it, it doesn't work. If I keep it on the rich side and adv. the timing, I gain more over-rev??? What am I doing wrong?

Thanks in advance!

[wobbly]

Re the TZ400 cylinder, that was just a dummy piece I used to build the pipes - the reed cylinder was away being plated.

Re the EngMod questions - Mach 0.8 is as you say 0.8 X Sonic.
If you change the A/F ratio from say 12:1 at say 12,000 to 13:1 at 12500 the Ex temp will rise in the pipe, but just as in reality the lower fuel energy
available my not in fact be sufficient to make more power.
This is way more likely to be affected by the Delivery Ratio dropping greater than the pipes positive effect from temp has on Hp.
Pulling out advance also affects the pipe temp, but again in many cases the engine efficiency drops way more rapidly than the rise in power seen from the pipe effect.
Thus if the bmep drops, then cylinder pressure drops, and more advance will often make better power - just as in reality, again.
What average pipe temps are you using, as this input shows a much greater effect on the Hp curve.
Remember that a solenoid powerjet is not " leaning out " the mixture, it is simply opposing the carbs natural tendency to go rich over the top of the powerband .
ie the A/F ratio is forced to remain alot closer to a constant number, not rise to make the engine hotter.

[shnaggs]

Re the TZ400 cylinder, that was just a dummy piece I used to build the pipes - the reed cylinder was away being plated.

Re the EngMod questions - Mach 0.8 is as you say 0.8 X Sonic.
If you change the A/F ratio from say 12:1 at say 12,000 to 13:1 at 12500 the Ex temp will rise in the pipe, but just as in reality the lower fuel energy
available my not in fact be sufficient to make more power.
This is way more likely to be affected by the Delivery Ratio dropping greater than the pipes positive effect from temp has on Hp.
Pulling out advance also affects the pipe temp, but again in many cases the engine efficiency drops way more rapidly than the rise in power seen from the pipe effect.
Thus if the bmep drops, then cylinder pressure drops, and more advance will often make better power - just as in reality, again.
What average pipe temps are you using, as this input shows a much greater effect on the Hp curve.
Remember that a solenoid powerjet is not " leaning out " the mixture, it is simply opposing the carbs natural tendency to go rich over the top of the powerband .
ie the A/F ratio is forced to remain alot closer to a constant number, not rise to make the engine hotter.

Thanks for the response Wobbly.

I am starting the exhaust wall temp at 325* and have peak power at 425*, I got those numbers from earlier in this thread. Are these numbers close to reality in a MX application?

As you stated above ^^^ I am seeing more over-rev with advancing the timing and keeping A/F constant. So this is due to the delivery ratio dropping off? So does that mean that if I increased the time-area of intake and exhaust the delivery ratio shouldn't drop off as much, allowing the heated pipe to suck more?

Was not aware of the powerjets keeping the a/f more constant on over-rev. Makes sense now that I think about it.

Thanks again!

PS. Wobbly, what combustion efficiency number would you use for a MX 250 with a bore of 66.4mm, and stroke of 72mm?

[wobbly]

So if you are running a solenoid powerjet you can simulate its action more accurately by setting the pipe temp at 450 at say 500 rpm past peak.
It will take some fiddling to find the element that is affecting the power the most past peak.
I have found time and again that all it needs is to pull down the Ex exit area to 75% and add a tapered nozzle out to the 100% header area.
The increased pipe temp doesn't make it " suck " more it increases the wave speed,that in turn reduces the effective tuned length.
You can try adjusting the intake length to get it into resonance in the overev, depending upon the harmonic being used and the room available.

A 250 well tuned will sim accurately at around 85 to 88% C.E

[richban]

Progress.

I've learnt so much I want to start again!

[wobbly]

Yea, the problem you now have is that as you have assembled the rear cones, you cant use a mandrel to tap the seam together
before or after welding.
Rule 1A is to always move along one weld at a time, so each seam can be tacked, tapped together accurately, then welded, then hammered flat.
To do it perfectly like the factory Ti pipes, the cones have to be absolutely round, and with purge gas up inside, the seam then cold wire over tig welded.
Then no hammering is needed, as the seam is as good on the inside as it looks on the outside.

[peewee]

worked all weekend with the epoxy. templates worked a treat. not sure if you can tell but these passages were never intended to have a large teacup (B and C are worse off because the inner radius is larger than A) . technically I guess theyre not actually a teacup but rather more like a half circle , similar to the rsa. I even grinded the gasket surface 6mm farther outward which is as much as the crankcase deck will allow without welding them wider. what ill probly have to do is grind some what of a teacup in the outter wall also , other wise there will be a choke point half way up the passage where the inner wall reaches its max radius

[F5 Dave]

Indeed, that I believe was my mistake when I did my 100. I think I reduced the volume of the transfers too much. Vinamold showed me what the finish was like where it was hard to see but your cylinder has the luxury of plenty of space.