ESE's works engine tuner

[wobbly]

Pipe temp should be 325 at the bottom of the powerband and 425 at peak power.
What are the STA values for the rotary valve using the figures you entered.
142 and 82 are very early timings for anything making good power.

[adegnes]

Pipe temp should be 325 at the bottom of the powerband and 425 at peak power.
What are the STA values for the rotary valve using the figures you entered.
142 and 82 are very early timings for anything making good power.

STA


Open and close later? So I would be better of with say 130/90?
Need to read up on the intake side of things...

Used lower temp because pump gas not avgas, wrong?

[TZ350]

Been a long time since I posted anything about my Peugeot Spx project, if anyone's interested I can do a little write up on what's been going on.

Yes please and lots of pictures too, if possible.

[wobbly]

Using 95 or 98 pump gas the pipe temp is close to Avgas.
But 91 makes more power with a richer mixture and more advance - and hates compression.
Back at 142 it will be a bitch to carb properly, i would start at 135 and close it where you need to to get the top end you are after.
Of course it depends on how much mid you can afford to loose - but 90* is very late and suitable for very high end applications.

[TZ350]

Breakfast of Champions



Av ... https://www.facebook.com/avalonbiddleracing

[41juergen]

Been a long time since I posted anything about my Peugeot Spx project, if anyone's interested I can do a little write up on what's been going on. Anyways, I'm currently trying to dial it in on my dyno and I'm experiencing some issues, need advice/help.

My sim of the engine give about 20-21 hp peak @ 15000rpm with 87% combustion efficiency.
The weird thing is dyno runs show only around 13 wheel hp peak @ low 12500rpm - somewhere around 16bhp(wheel/roller0.95 x chain0.95 x variator 0.88, best loss estimate I could come up with)

I've gone through my numbers, the computer model is accurate.
I've jettet up/down and shifted the ignition timing around to no avail.
Ignition energy related?
What's going on?

Max egt ca 600c, cht around 80c, is the low cht telling me something? By doing 6-7 runs in a row without break I can make it touch 110c.

Is my combustion efficiency horrendously low? If I lower it to 75% in the sim it seems to reflect reality with 16hp peak @ around 12500rpm. why?


I'll post sim file later, not at my computer atm.

edit: here ya go! I'll post the dyno graphs too later, different computer.
Attachment 324397Attachment 324394Attachment 324398Attachment 324395Attachment 324396Attachment 324393

Your STA's you have shown predict approx. 18 crank HP and aren't your Exhaust timing as well the transfers not a bit low?

[wobbly]

The sim blowdown shows 18.5 crank,so this means around 15.5 rear wheel on a Dynojet - if everything is done real well.
Add in another 10% loss for the belt drive and now you have 14 Hp.

[adegnes]

Using 95 or 98 pump gas the pipe temp is close to Avgas.
But 91 makes more power with a richer mixture and more advance - and hates compression.
Back at 142 it will be a bitch to carb properly, i would start at 135 and close it where you need to to get the top end you are after.
Of course it depends on how much mid you can afford to loose - but 90* is very late and suitable for very high end applications.

Ok, thanks for the advice!

[adegnes]

Your STA's you have shown predict approx. 18 crank HP and aren't your Exhaust timing as well the transfers not a bit low?

You're right about that! I want to establish a baseline before I start grinding further - be able to quantify how bad I screw up...

The sim blowdown shows 18.5 crank,so this means around 15.5 rear wheel on a Dynojet - if everything is done real well.
Add in another 10% loss for the belt drive and now you have 14 Hp.

Maybe I'm not that far off then.
I'll see if I can touch 14 on the roller, then add some blowdown and a better pipe!

[_____]

Pipe temp should be 325 at the bottom of the powerband and 425 at peak power.

Hi wob and everyone!
I have a general question on the exhaust temperatures. Are they a depending on the cc of the engine?
I worked on a 50cc engine with engmod and the estimated peak of the simulation was at least 2000 RPM higher than in real life. In fact, i needed to make the temperature on the exhaust unphysically low (150°C) to get the rpm range to suit the reality.
I would suggest the temperature to be a formula of the cubic capacity, bmep and blowdown (more blowdown meaning less backflow to the transfers, thus the first gas scavenged and lost through the exhaust will be way cooler than with less blowdown)


cheers from germany
Christoph

[adegnes]

Back at 142 it will be a bitch to carb properly

Could my extreme case of early opening due to the loose disc be the reason my carb has been spewing fuel out the overflow at certain rpms, not vibration as I thought? Thinking about it, I've experienced far more vibration in other bikes without it affecting carburetion.

[adegnes]

Opening the disc earlier in order to increase inlet angle.area will function mathematically but angle.area is only one of the factors affecting intake flow. It would not be very wise to open the disc when crankcase pressure is still higher than the pressure upstream of the disc.
The lower the revs, the more time there is available for the crankcase pressure to drop; at 9000 rpm you could open the disc before BDC to good effect; crankcase pressure would not drop so far and scavenging flow would not be slowed down so much, resulting in more mixture reaching the cylinder. But such an early opening timing would seek revenge at higher revs.
Another effect, also mentioned by Wobbly: the earlier you open the disc, the smaller the pressure difference between crankcase and inlet tract and the weaker the suction pulse at the needle jet, which makes setting the carburation increasingly difficult.

Maybe mixture on its way out of the crankcase was colliding with mixture on its way in, and this caused higher than atmospheric pressure in the carb, blowing fuel ut of the bowl.
No fuel spilling below 11-12k.
You might also recall that I had a hell of a time getting it to start at all before I found the carb "sweet spot".
Interesting.

[wobbly]

In my experience the only thing that really affects the pipe av temp is specifically what egt in the header creates max power.
This is tied directly to the bsfc number and this is affected by the fuels octane,and thus indirectly the burn speed,along with the fuels energy content.
Fuel such as 91 pump or some race fuels ( such as the unleaded that replaced that used in the 2T GP classes ) makes best power when running well under stochiometric.
Thus when run rich with a ton of ignition timing, and reduced compression, the egt in the header is typically in the high 500*C/low 600*C range.
Whereas Avgas and real leaded racegas such as 110 octane loves compression, and responds well to lean mixtures and lots of retard to increase pipe heat.
These engines run in the high 600*C range in the header.
95/98 pump gas is similar to Avgas but cannot tolerate as much com, so the egt rises, close to that Avgas would show with higher com.
Thus most sims work well with the 325/425 wall temp range, but this needs modification where an out of range combination of fueling/com/timing is used.

Rotary valves create havoc in the carb bore over the emulsion tube exit , even with " normal " timings.
Have completely weird arse numbers,even going back to 142* makes everything so unpredicatable its impossible to sim it properly let alone tune the carb effectively.

[Frits Overmars]

I just discovered the disc valve was loose on the crank, could move 30ish degrees back and forth.

... my extreme case of early opening due to the loose disc

That would be extreme indeed, Adegnes. The disc does not run without friction; it has to be taken along by the crankshaft. And if there is any play, it will lag behind, opening 30° later instead of 30° earlier, but also closing 30° later than the 83° aTDC that you mentioned on the previous page. Now that will really upset the carburation.

[adegnes]

That would be extreme indeed, Adegnes. The disc does not run without friction; it has to be taken along by the crankshaft. And if there is any play, it will lag behind, opening 30° later instead of 30° earlier, but also closing 30° later than the 83° aTDC that you mentioned on the previous page. Now that will really upset the carburation.

Of course