ESE's works engine tuner

**wobbly** · 16th October 2023, 18:58

Easy way is to use oversize 4140 studs ( 1/2" =12.7mm ) with the stock 8mm threaded ends.
This was done to the TZ350 LSR title wining engine for both a 3port Exhaust , and a bridged reed intake.
Made over 100 Hp at 12,000.
The FEA confirmed the stress was equal at the thread root diameter when 1/2 the stud was ground away for the duct width needed.

**jato** · 16th October 2023, 19:55

Thanks for that - a good solution!

**diesel pig** · 16th October 2023, 23:21

Originally Posted by wobbly

Easy way is to use oversize 4140 studs ( 1/2" =12.7mm ) with the stock 8mm threaded ends.
This was done to the TZ350 LSR title wining engine for both a 3port Exhaust , and a bridged reed intake.
Made over 100 Hp at 12,000.
The FEA confirmed the stress was equal at the thread root diameter when 1/2 the stud was ground away for the duct width needed.

Interesting, How did one stop the exhaust gases causing problems in the cylinder bottom and top where the studs meet the different castings

**wobbly** · 17th October 2023, 06:59

The studs were a neat fit in the overbored casting thru holes and you can see the groove for a Viton O ring just above the Exhaust cutout level.
Never had any heat issues with the gasket surfaces .
Hours of sim , and hours of TIG.
Fastest Pre 82 Post Classic 350 non streamliner on the salt ( 172 mph stuck in 5th pulling 12,000 ) , the second cylinder is in the Frepin frame now.
Not sure who's more scared of it with 100 Hp , me or Charlett.
He does record 13s around Hampton now , with this thing in it and +50mm swingarm I recon 10s easy.

**Grumph** · 17th October 2023, 07:33

I see the inlet side studs are cut away too. Got a pic of the inlet side of the barrels please Wob ?

**wobbly** · 17th October 2023, 08:55

Yep , my version of Kenny's factory OW , but faster.
Cant decide what would be scarier a TZ750 with 200Hp or a TZ350 with 100Hp.

**Grumph** · 17th October 2023, 10:40

Thanks for the pics Wob.

TZ750 with stock frame would not be pleasant. Where's the Nico Bakker been hidden ?
In some ways the Frepin isn't ideal either. From all i've heard Fred was building for light weight prioritised over stiffness.
And yeah, i know yours is stiffer than the originals.

**diesel pig** · 17th October 2023, 11:13

Originally Posted by wobbly

The studs were a neat fit in the overbored casting thru holes and you can see the groove for a Viton O ring just above the Exhaust cutout level.
Never had any heat issues with the gasket surfaces .
Hours of sim , and hours of TIG.
Fastest Pre 82 Post Classic 350 non streamliner on the salt ( 172 mph stuck in 5th pulling 12,000 ) , the second cylinder is in the Frepin frame now.
Not sure who's more scared of it with 100 Hp , me or Charlett.
He does record 13s around Hampton now , with this thing in it and +50mm swingarm I recon 10s easy.

It took me a little time looking at the pics to realise the water jacket had bin cut away to allow the welding for the exhaust ports, I take it they were patched up afterwalds?
Am I reading the code stamped into the top of the piston right and it's a different bore size?

**diesel pig** · 17th October 2023, 11:16

Originally Posted by Grumph

I see the inlet side studs are cut away too. Got a pic of the inlet side of the barrels please Wob ?

Good spotting! what size reeds are you using? If I can ask Wobbly.

**diesel pig** · 17th October 2023, 11:21

I forgot to ask this in my first Question. I noticed welding on the bottom of the cylinder is it a different stroke?

**husaberg** · 17th October 2023, 19:10

Originally Posted by diesel pig

I forgot to ask this in my first Question. I noticed welding on the bottom of the cylinder is it a different stroke?

top and bottom from memory

Originally Posted by husaberg

**Tim Ey** · 18th October 2023, 07:58

Originally Posted by jato

Re auxillary exhaust ports; i am assisting a small amount with building a set of kawasaki triple cylinders - modern port layout with reedvalves fitted but still non powervalve. at this stage the aux exhaust ducts need to do a gentle loop around the outside of the forward cylinder studs - would this be a no go? the alternative is to relocate the studs but this is not the most preferred solution. any thoughts?

I would definitely lead the auxilary ports around the studs.
This was done by DEA in a Vespa Smallframe cylinder. Very good design!
https://www.facebook.com/DeaEngineer...952237/?type=3

**wobbly** · 18th October 2023, 09:54

Bunch of questions and answers - the long stroke is from cranks I had made with Mallory added for balancing and is 58mm ( +4 Banshee based ) by Shunchi in Taiwan.
They do HotRods and a couple of others.
The bore is 61.5 using race H1 pistons.
Best combination of rpm and port power I could get for an odd 175cc cylinder size.

The cylinder is a 250G as it had the best ducts Yamaha could do in the RD based case stud layout.
A deck plate was added as the rods are special RD400 with Peek coated flat cages @ 115mm to get some case volume and 1.3 ratio , and another plate was added on the top to get the piston edge -0.8 down at TDC.
The crank has rollers on both ends with straight cut low ratio gears , so the clip slot is moved into the middle balls.
The reeds are RS125 Honda from VeeForce , same bolts as CR125 and are what I used offset in the TZ400 , replacing CR250 to get them back on bore center in the flawed CPI cylinder design.

Re the addition of Aux port ducts - sweeping around the studs may look efficient , but then you have an even bigger disparity between the main duct and the Aux duct length.
This smears out the wave front exiting at EPO even more in time and amplitude.
Wasted studs are the best solution - was done first on the inlet in Eckerolds last 350 privateer title TZ/Bimota by my hero Helmut Fath.

I believe the Baker went bare to OZ , Trev put the engine back in a Yamaha frame.

Question from me - when Dennis won the Shorai challenge at Hampton on the TZ400 there was a shitty condition YB3 from OZ with a young lady on board , I want it , the bike or the girl would do .
Who , where etc etc.

**Storbeck** · 19th October 2023, 02:10

Originally Posted by wobbly

Bunch of questions and answers - the long stroke is from cranks I had made with Mallory added for balancing and is 58mm ( +4 Banshee based ) by Shunchi in Taiwan.
They do HotRods and a couple of others.
The bore is 61.5 using race H1 pistons.
Best combination of rpm and port power I could get for an odd 175cc cylinder size.

The cylinder is a 250G as it had the best ducts Yamaha could do in the RD based case stud layout.
A deck plate was added as the rods are special RD400 with Peek coated flat cages @ 115mm to get some case volume and 1.3 ratio , and another plate was added on the top to get the piston edge -0.8 down at TDC.
The crank has rollers on both ends with straight cut low ratio gears , so the clip slot is moved into the middle balls.
The reeds are RS125 Honda from VeeForce , same bolts as CR125 and are what I used offset in the TZ400 , replacing CR250 to get them back on bore center in the flawed CPI cylinder design.

Re the addition of Aux port ducts - sweeping around the studs may look efficient , but then you have an even bigger disparity between the main duct and the Aux duct length.
This smears out the wave front exiting at EPO even more in time and amplitude.
Wasted studs are the best solution - was done first on the inlet in Eckerolds last 350 privateer title TZ/Bimota by my hero Helmut Fath.

I believe the Baker went bare to OZ , Trev put the engine back in a Yamaha frame.

Question from me - when Dennis won the Shorai challenge at Hampton on the TZ400 there was a shitty condition YB3 from OZ with a young lady on board , I want it , the bike or the girl would do .
Who , where etc etc.

This brings up a thing that I've seen a few places but never understood.

Auxiliary exhaust ports lower than the main port seems to be something that is completely universal and I get the impression it has been tested to death and there is not much question that is what works best.

But...why? I don't think I've ever seen an explanation that makes sense (to my possibly dim mind). Usually something about smearing or distorting the wave front...but...since the auxiliary exhaust ducts are longer than the main duct, wouldn't that mean that if they were opening at the same height, the wave from the auxiliary ducts would be behind the wave from the main duct, and in order for them to arrive at the same time you would need the auxiliaries to be higher than the main duct and open first.

OR conversely, if there is some advantage to having the wave front from the auxiliaries behind the wave front from the main duct, couldn't you make the auxiliary ducts longer, and the port height the same, thus getting more time area and/or more space for transfer ports?

The best cylinders seem to not do that, so...I dunno.

**OopsClunkThud** · 19th October 2023, 02:33

Originally Posted by Tim Ey

I would definitely lead the auxilary ports around the studs.
This was done by DEA in a Vespa Smallframe cylinder. Very good design!
https://www.facebook.com/DeaEngineer...952237/?type=3

On the DEA (and other) vespa smallframe cylinders the aux ports pass inside the studs, but include a bump on the outer edge to clear the stud. The wasted studs could easily be applied to these to remove that bump.

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