ESE's works engine tuner

[TZ350]

This is a model of the exhaust port dam.



The aluminium insert is not quite as good as the model but good enough to test on the dyno.

The RG50's exhaust duct diameter is 26mm at the flange face and because EngMod is pointing to 23mm as being more ideal we might try an entirely different approach to the exhaust dam idea that incorporates Wobblys suggestion of using the insert to reduce the duct area at the flange face. Maybe make something out of copper that is pressed into the exhaust duct for better heat transfer to the water jacket.

[wobbly]

TeeZee, the Mach numbers are telling you exactly what you need to know.
The port layout as it stands with the huge width above the transfers is operating like a T or 3 port, thus the Mach numbers for ExMach 1 are too low
as I have found most ducts taken down to 75% area at the flange will approach 0.8Mach - and this seems to be the best compromise for power.
The TuB number that is very high down low like yours is usually easily fixed by pulling out some timing, and then the whole curve can be lifted by making the stinger smaller, or cranking in more timing.
You can juggle com/timing/stinger in endless combinations, but the number will always drop away toward peak power as the timing needs to be pulled to get more heat into the pipe.
This is always more effective than using most of the finite combustion energy to compress the gas, as a longer pipe can be used with less timing - and this makes more overall power.
But sometimes this effect of a high TuB down low is caused by the reeds being very effective, due to their first harmonic tuning being in that range - have a look at that.
The Ex outlet being too big on every engine is exactly what I found years ago when I first started seriously using EngMod, and this developed into my 75% area rule of thumb soon after
that Neels has now incorporated into the inputs screens.

Re polishing the beams on rods.
When you do this you are cutting thru the highly compressed skin created by the forging process.
The as forged skin may look like shit, but is in fact very strong.
Polishing removes all the small imperfections and stress raisers, but then the rod MUST be re shot peined.
The finished result will be much stronger again than the original as forged item, and lighter.

[TZ350]

Thanks Wob, now I know a bit more about using Engmod effectively I will use it and your comments to develop a plan for the next step in tuning the RG50.

[ief]

would some form of aluweld be more effective in shaping the duct? Comes in different temp variations and sticks to most metal.

Just don't know if it will cope with the temps but guess it will (?)

[husaberg]

Re polishing the beams on rods.
When you do this you are cutting thru the highly compressed skin created by the forging process.
The as forged skin may look like shit, but is in fact very strong.
Polishing removes all the small imperfections and stress raisers, but then the rod MUST be re shot peined.
The finished result will be much stronger again than the original as forged item, and lighter.

The easiest way to do this is with linisher its surprising quick, so be careful, I recommend practising on a old rod first.( I learnt that the hard way)
The Air NZ workshop in CHCH used to do the peening (for beer money) as well as dynamically balancing the old Brit twin cranks for a lot of people not sure if it even still exists to this level anymore now likely a lot of stuff is outsourced.
The peening appears to give it a finish that resists minor corrosion not sure why.

[wobbly]

One more small detail is the length of the duct to where you form the smallest area nozzle.
In my experience one bore diameter is too short for the duct length - including the spigot/venturi.
Closer to 2* bore seems to be better.
So in the case of the RG50 it is easy enough to fabricate a longer bolt on spigot after you have had a play in Engmod by lengthening the duct and shortening the pipe.
The KTM one shown was a female spigot with the duct at 1* the bore, it worked way better and was easyer to transition better closer to 2* with an insert that became
a male slip joint.

[TZ350]

One more small detail is the length of the duct to where you form the smallest area nozzle. In my experience one bore diameter is too short for the duct length - including the spigot/venturi.Closer to 2* bore seems to be better. Easier to transition better closer to 2* with an insert that becomes a male slip joint.

Good thanks Wob. So although it is a single exhaust port which would normally be best with the smallest area of the duct at 90% of the exhaust port window.

Because the RG50's single exhaust is more like a T or Tripple port the duct could be better at 75%. With the narrowest part at a distance of 2 times the bore diameter or 82mm.

I will start modeling this up, not sure if this is the right thing to do but I will start with the Mach sensor at 82mm and use the first 41mm part of the pipe to form the converging part of the nozzle.

[wobbly]

No - I think a better solution would be to have the add on spigot at say 40mm long.
Its outlet will be the header round diameter, but for the first 1/2 or 20mm continue reducing the duct size down to the 75% number.
This will mean less filling will be needed in the actual cylinder duct and the smallest area point to place the sensor ( as this will now be the duct length ) , will be at 60mm.
From 60mm out to 80mm the duct in the add on spigot will diverge.
And this last 20mm diverging section will be the first element in the pipe input.

[AndreasL]

Great TZ and Wobbly!

This will help a lot.

[Grumph]

The easiest way to do this is with linisher its surprising quick, so be careful, I recommend practising on a old rod first.( I learnt that the hard way)
The Air NZ workshop in CHCH used to do the peening (for beer money) as well as dynamically balancing the old Brit twin cranks for a lot of people not sure if it even still exists to this level anymore now likely a lot of stuff is outsourced.
The peening appears to give it a finish that resists minor corrosion not sure why.

Aviation Support Services at ChCh airport still do shot peening - but not for beer money...Most airports with any sort of ground support for aircraft work will probably have someone who can do shot peening.

[husaberg]

Aviation Support Services at ChCh airport still do shot peening - but not for beer money...Most airports with any sort of ground support for aircraft work will probably have someone who can do shot peening.

What about the dynamic balancing?

[Grumph]

What about the dynamic balancing?

Not at the airport to my knowledge. The guy in town who was really good - ex DSIR - sold his gear to Gav Hill (HPE). You takes your chances...
Barry Lynch can be persuaded to do static balancing. Couple of reconditioners have dynamic gear. Best in my experience is Coombes. I've used them for probably 30 years...

[husaberg]

Not at the airport to my knowledge. The guy in town who was really good - ex DSIR - sold his gear to Gav Hill (HPE). You takes your chances...
Barry Lynch can be persuaded to do static balancing. Couple of reconditioners have dynamic gear. Best in my experience is Coombes. I've used them for probably 30 years...

Barry Lynch rings a bell was he ex st Asaph street?

[Kickaha]

Barry Lynch rings a bell was he ex st Asaph street?

Beaumont Engineering

[husaberg]

Beaumont Engineering

Wrong bell on the wrong street then.