ESE's works engine tuner

[diesel pig]

Re reading wobbly's posts on tuning with EGT he talked about aiming for a exhaust temperature with leaded gas between 1200 and 1250 *F for best power with temperatures of 1300 *F and above to be avoided as not being good for the motor. Having manage to take this much on broad when tuning on my private test road I tired to avoid seeing more than 1260 *F in all the rev range at all. But later when re reading wobbly's posts on ignition timing I pick up on what he was saying about retarding timing pass max power rpm to get overrev and this was done by getting more heat into the pipe to trick the motor into acting like the pipe is shorter than it is. So I am thinking have I got the wrong end of the stick with the temperatures? is the 1200 to 1250 the temp for MAX Power RPM and a higher temps in the overrev rpms is a product of getting the overrev and not to be worry about?

[Frits Overmars]

Thankyou, Frits, crazy man, thought as much. I tried ceramic coated pistons some years ago and that's what they did , get hot and help detonation. I wonder about these modern metal sintering ( laser welding metal layer by layer ) apparently you can change the metal as the component is built up. A piston could start off aluminium alloy and end up with say a copper finish layer on top, flash chrome over that. Perhaps?

Absolutely. Aprilia GP piston heads were polished to a mirror shine; piston heads for four-stroke competition engines are sometimes chromed. I don't know whether this chroming can be done by selective laser melting, but chroming the piston head in the conventional way has given good results.
If you want to protect the piston from combustion heat, covering its head with a heat barrier is not the way to go because of the detonation this will cause.
The only safe way I can think of is to reflect the heat. That way it won't get into the piston material and as soon as the combustion is gone, so is that heat reflection; fresh mixture won't be heated.

[speedpro]

I think as Wobbly explained it the main port needs to open first as it's bigger and the shape of the top of the port results in a strong leading edge to the pulse. This strength has benefits later in the cycle. Opening the aux ports early or at the same time smears the pulse and reduces it's initial strength thereby losing it's effectiveness.

I've been polishing the tops of pistons for years for two reasons. 1 - to reflect heat back from the piston and 2 - to reduce stress risers in the crap cast pistons I was using. The surface finish on the crowns was utter garbage.

[Frits Overmars]

Looking at the RSA125 tubo-102 pipe, Jan Thiel has gone for a three angle reverse cone. What's your thoughts on the thinking behind that?

My thoughts is that you are jumping to conclusions, Dutch. But you are forgiven because I will admit that it is logical to assume that Jan developed that pipe.
In reality he didn't; technical director Witteveen (or The Great Leader as he was called) did; pipes were his hobbyhorse. And each time Jan Thiel had to adapt the cylinder to get it running with Witteveens pipe designs; not a great way to commit development.....

[RomeuPT]

I also believed what I had been told previously ,that large changes in initial diffuser angle would cause flow separation and massive turbulence due to choking.
I built a heap of pipes to come up with a new design for CR125 Moto in SKUSA racing.
One of the tests was to try a design similar to the older Aprilia, with a very steep diffuser directly after the header.
This pipe made good power, but i was sure that if I added a short 25mm section ( the length of a bend segment in the U bend ) between the header and the main diffuser, with
only 1/2 the angle change - it would make more power.
Sadly no free lunch, it was worse by a small margin - bugger, another wives tale down the dunny.
I went on to discover the relationship of best power production, to the shape of the depression waves amplitude around BDC - was super critical to where the main diffuser started.

Thanks Wobbly. It's been a pleasure to talk with people from the other side of the world.

Main diffuser on your Hell pipe start at 43,25% and Aprilia tubo 102 at 41%. So I maybe use 42% as baseline for the next exhaust I build....

We can't say that the wave is traveling at the main difuser after 42% of exhaust opening right? If the exhaust gases are colder at the spignot, and the belly is the hottest point then the 42% is before because the wave might travel slower at the header!? And the wave enters the duct some degrees after exhaust open!?

Regards

[wobbly]

You have to be careful when using retard to heat the pipe in the overev.
If you continue the retard slope too far,especially if the motor then continues to make serious power - the egt will continue to rise with rpm, and you then end up running a richer main to suppress the now too high egt.
This means you are using fuel to cool, not burning it to make power.
You must flat line the ignition retard as soon as you can in the overev, to stabilise the egt when running full throttle at those peak revs.

You have got the wrong end of the stick re pipe temp Romeu, the highest temp is seen just into the header, the lowest in the belly, and it increases again at the stinger.
Lower temps are seen right at the flange, due to unburnt air/fuel sitting there waiting to be shoved back in.
Aprilia used probes in the flange due to reliability issues I understand,but they would for sure have found a correlation between the readings there, and the " normal " one along the header.

Three angle rear cones were a legacy design that Jan was forced to use, as Frits explained.
But it is a long time issue for me that so often a sim will be strongly telling me that the system works well ( and it annoys Neels as well I know ) but in reality I have never been able to get more power on the dyno
than a 14* straight tailcone - believe me I have waisted so much time on this, and have given up.

In a KZ2 125 kart engine with the main Ex port opening at 82.5* you would normally have the Aux about 1.5mm lower - lift them up flat and you loose around 3 Hp at 10,000, 1 at peak 13,000, but worst is
up to 6Hp at 14,000 where the curve is dropping rapidly.
I tested a cylinder with the main down at 84* and the ports all opening flat made the most power there, but sadly that power was well down on what is possible with a higher main and staggered Aux.

Re the diffuser position for RS125 - the Aprilia rotary valve engine was , by design, run to 14500 on track, so was able to use the slightly shorter header end position.
The reed valve Honda is virtually impossible to get to run up there with any effective gains, so makes more power in its useable band with the slightly longer header.

[Flettner]

Transfer port injection

[F5 Dave]

Mag has just come out, 21.4 bhp after a few runs on the dyno... .

On Facebook if anyone is interested, here:

https://www.facebook.com/groups/prac...5170764195858/

Dave

Went to look in shop but silly 'cause we won't see that edition for a couple of months. Not on Farcebook by principle. Either way its a good start, but they won't crack 100 with that in that roadbike chassis I don't think. its an ok effort with what they started with. Given the options & the lack of initial rules I think I'd be reaching for the liquid horsepower to make good the 100mph target. What revs were they pulling? Seemed to be a major limitation in initial calculations.

[Haufen]

Absolutely. Aprilia GP piston heads were polished to a mirror shine

As were the combustion chambers?

[Frits Overmars]

As were the combustion chambers?

Yes, the chambers were polished too, but I think the main goal here was to avoid carbon deposition which could cause glow ignition.

[RomeuPT]

Frits I noticed that tubo 55 was slighly thinner at the belly than 102.

Is the energy of the wave going down the exhaust port lineary greater with a raise in HP? So if you have got more horse power you can try increase pipe volume/angles and get even better?

Regards

[RomeuPT]

You have to be careful when using retard to heat the pipe in the overev.
If you continue the retard slope too far,especially if the motor then continues to make serious power - the egt will continue to rise with rpm, and you then end up running a richer main to suppress the now too high egt.
This means you are using fuel to cool, not burning it to make power.
You must flat line the ignition retard as soon as you can in the overev, to stabilise the egt when running full throttle at those peak revs.

You have got the wrong end of the stick re pipe temp Romeu, the highest temp is seen just into the header, the lowest in the belly, and it increases again at the stinger.
Lower temps are seen right at the flange, due to unburnt air/fuel sitting there waiting to be shoved back in.
Aprilia used probes in the flange due to reliability issues I understand,but they would for sure have found a correlation between the readings there, and the " normal " one along the header.

Three angle rear cones were a legacy design that Jan was forced to use, as Frits explained.
But it is a long time issue for me that so often a sim will be strongly telling me that the system works well ( and it annoys Neels as well I know ) but in reality I have never been able to get more power on the dyno
than a 14* straight tailcone - believe me I have waisted so much time on this, and have given up.

In a KZ2 125 kart engine with the main Ex port opening at 82.5* you would normally have the Aux about 1.5mm lower - lift them up flat and you loose around 3 Hp at 10,000, 1 at peak 13,000, but worst is
up to 6Hp at 14,000 where the curve is dropping rapidly.
I tested a cylinder with the main down at 84* and the ports all opening flat made the most power there, but sadly that power was well down on what is possible with a higher main and staggered Aux.

Re the diffuser position for RS125 - the Aprilia rotary valve engine was , by design, run to 14500 on track, so was able to use the slightly shorter header end position.
The reed valve Honda is virtually impossible to get to run up there with any effective gains, so makes more power in its useable band with the slightly longer header.

If the T port likes opening dead flat and the two aux's port likes staggered, I wonder what would an W exhaust port likes....

[F5 Dave]

If the T port likes opening dead flat and the two aux's port likes staggered, I wonder what would an W exhaust port likes....

Eating rings for breakfast?

[Dutch Fisher]

In a KZ2 125 kart engine with the main Ex port opening at 82.5* you would normally have the Aux about 1.5mm lower - lift them up flat and you loose around 3 Hp at 10,000, 1 at peak 13,000, but worst isup to 6Hp at 14,000 where the curve is dropping rapidly.
I tested a cylinder with the main down at 84* and the ports all opening flat made the most power there, but sadly that power was well down on what is possible with a higher main and staggered Aux.

Do you have a rule of thumb for the main and aux differential openings considering different B/S and cyl vol?

[Frits Overmars]

Frits I noticed that tubo 55 was slighly thinner at the belly than 102. Is the energy of the wave going down the exhaust port lineary greater with a raise in HP? So if you have got more horse power you can try increase pipe volume/angles and get even better?

All other things being equal, more horsepower goes together with more exhaust gas energy. But the connection is not linear and all other things are never equal.
Exhaust gas energy is mainly effected by squish, ignition timing, flame speed and compression ratio. And as I tried to explain before, you can overdo it with diffusor and reflector angles; there is no maximum but there is an optimum.