ESE's works engine tuner

[wax]

Im wondering if anyone has played with a reverse taper inlet on a two stroke intake.
Instead of having the taper get larger or stay parallel im talking about a 11 degree angle which would keep increase the inlet air speed.
11 degrees increases speed with out losing mass so in effect it would end up with a high pressure on the reed block
Thoughts ?

[F5 Dave]

Where does this reed exit out to? I think that's probably your answer.

[EssexNick]

Inlet taper.
My initial thought was a really short inlet is required, so there may not be sufficient length to see any noticeable gains. It might help a lower reving motor. But i am just guessing here.

[husaberg]

Im wondering if anyone has played with a reverse taper inlet on a two stroke intake.
Instead of having the taper get larger or stay parallel im talking about a 11 degree angle which would keep increase the inlet air speed.
11 degrees increases speed with out losing mass so in effect it would end up with a high pressure on the reed block
Thoughts ?

Reed valves are already an venturi.......

[TZ350]

I'm wondering if anyone has played with a reverse taper inlet on a two stroke intake.Thoughts ?

Yes. It was something I played with briefly on my rotary valve engine but it did not show any benefits and made less power. Put it down to the fact a 2T is not a 4T and 4T ideas don't always translate to 2T's. Maybe I got something wrong, but anyway I wasn't impressed. Would love to hear if someone has had success with the idea.

Im talking about a 11 degree angle which would keep increase the inlet air speed. 11 degrees increases speed with out losing mass so in effect it would end up with a high pressure on the reed block.

Higher pressure? or greater kinetic energy? I wanted kinetic energy (speed * mass) to ram and over fill the crankcase. Pressure recovery increases as you slow the moving air column down.

[SwePatrick]

Im wondering if anyone has played with a reverse taper inlet on a two stroke intake.
Instead of having the taper get larger or stay parallel im talking about a 11 degree angle which would keep increase the inlet air speed.
11 degrees increases speed with out losing mass so in effect it would end up with a high pressure on the reed block
Thoughts ?

I have good experiances with having the carb taper drilled.
From big to smaller in the direction of flow.

First the velocity stack then inlet 46.5mm and outlet 43.5mm.
This is roughly 1.5degree on the radius.

This has proven for me to add torque and keeping the top end as a 45mm carb has.

[chrisc]

Chris how do you get in these situations? I would love to have been in those pits with all those 50s.
I guess they make our efforts look a little shaky.

Pure enthusiasm Dave! Plus I seem to have made quite of lot of friends recently when flew to the other side of the world to race 50s! The ~$3000 in insurance isn't cheap but the experiences and memories will always be worth it.

And yeah, our machines are uhhhh, quite primitive MOST of these 50s are more developed and have better gear on them than any 125GP bike or 250GP bike in New Zealand. Which makes sense given our distance from European professional teams and racing. I've learnt a lot already. I truly think F5 should adopt Freetech rules. It's one hell of a class! I'd like to ride a Freetech level 50 against the 250 production bikes in New Zealand. I think I could beat most of them with this level of tech.

Choice Chris.
Loving the pictures and the updates.

Really Really Great write up Chris, and super great to see Frits there with you.

Thanks Brent, Rob! Glad you're enjoying them, I'm enjoying sharing the experience!

what tires are you using chris ?

Dunlop Moto3 slicks on factory NX4 wheels. Most of the field have PVM, Marchesini, Marvic or carbon wheels hahaha it's nuts! I have a new medium compound on the front and a new soft on the rear. Thankfully they're new and they were cheap but I'll see how this medium works for my light weight and smooth (read: not heavy on the brakes) riding style.

[wobbly]

I have tried increasing the velocity ( read decreasing the inlet area ) on several VF3 reed blocks.
By adding a vertical splitter ( they all have a horizontal one ) to the stuffer insert every one made better mid power with no loss in peak or overev.

And in the KZ2 kart engines that are limited to a 30mm carb, I spent hours CAD designing up a stuffer that created a venturi at the point where the cage ports begin.
This is 3mm smaller than the carb in area,and the smaller area is kept right up to the cage tip where the reed petals end ( the area measured with the petal closed ).
The 3D printed stuffer costs $15usd to have done in Taiwan, and is the cheapest, quickest 0.5 to 1.5 Hp I have ever seen.
I believe that if we were allowed to press in a tapered insert from the slide,to the end of the carb spigot, this reduced stuffer area would work even better.

But the reverse idea works really well on Lectron HV carbs.They have a venturi directly behind the slide that is 4mm smaller than the bellmouth entrance area.
This R2 venturi then tapers back out to the nominal carb size at the spigot end.
On the flow bench a 40mm Lectron will flow over 12% better at WOT than a 38mm PWM but has 18% more velocity under the slide at 1/2 throttle.
Thus way better throttle response as well as more top end power.
The very reason that many people ( EMOT )use huge 30mm Lectrons on the 50cc racers in Europe - note to Chris.

[lodgernz]

I truly think F5 should adopt Freetech rules. It's one hell of a class! I'd like to ride a Freetech level 50 against the 250 production bikes in New Zealand. I think I could beat most of them with this level of tech.

I just read the Freetech 50 rules online. What a joy of simplicity and clarity! Well done Frits. Then I look at the MNZ rules and cringe.

If we were to introduce those same rules here, I suspect it would force everyone who wanted to compete to move to nicasil-bore cylinders, since oversize cylinders are not allowed. Older cast iron cylinders and those with steel liners would be eliminated since most of them are already at least one oversize. Given the investment some of us have in this old stuff (pretty much mandated by our own bucket rules), a Freetech 50 class might be less attractive initially.
Obviously, these old engines would no longer be competitive in the face of MX 50 engines and Euro race engines, so would fall away anyway, but it would be nice to have an upgrade window. Possibly we could change the rules slightly to allow minimal overbore. Or we could run two classes of 50, Freetech and Vintage, but this is probably not feasible given the small number of people who race F5 now.

It's a fantastic class though, no argument.

[speedboy]

"On the flow bench a 40mm Lectron will flow over 12% better at WOT than a 38mm PWM but has 18% more velocity under the slide at 1/2 throttle."

40^2/38^2= 1.108
Lectron is 1 percent better (measurement error may be greater)

Half throttle is it may not be a half surface, but if so, then there is a little better.

[wobbly]

1.108 is 10% more area, and the lectron flows slightly better than 10% more air ( same pressure drop of 28" ).
At 1/2 throttle the area is also 10% different, but the lectron has a huge advantage in velocity across the fuel nozzle and thus the signal strength.
This allows a bigger carb size to be used without loosing throttle response - the old issue of " staggers " when opening a carb that is too big.
Why do you think Lectron call these things HV carbs.

[speedboy]

1.108 is 10% more area, and the lectron flows slightly better than 10% more air ( same pressure drop of 28" ).
At 1/2 throttle the area is also 10% different, but the lectron has a huge advantage in velocity across the fuel nozzle and thus the signal strength.
This allows a bigger carb size to be used without loosing throttle response - the old issue of " staggers " when opening a carb that is too big.
Why do you think Lectron call these things HV carbs.

At half throttle is ok, when lectron and pwm venturi shape is same. But shape is another, then half throttle area is different, incorrect measurement. I think lectron and keihin throttle body is not same.

[wobbly]

The difference is that the 40mm Lectron has a 36mm venturi behind the slide.
Thus at 1/2 throttle it acts like a 36mm carb, at WOT it acts like a 40mm carb.
The area change is even greater in a 30mm body as they use in 50cc racing.
At 1/2 throttle it has a 26mm venturi,giving 33% more velocity /fuel signal than a parallel bored 30mm carb.

[Nath88]

Found something interesting while checking out the Athena GET aftermarket ECU for the KTM TPI system...
http://www.getdata.it/data/documenta...IP_0039_AA.pdf



The 'injectors support kit' moves the injectors to a spacer plate between the reed block and crankcase, and plugs the existing transfer port bungs.
I also downloaded the map pack and included was a map for 'indirect injection'. Couldn't find any other info on it anywhere. Must be some performance improvement, is a lot of effort to go to to make something worse.

Update on my bike, I had the cylinder 'bored' by the other shop in Australia that does Nikasil. Got it back to adjust the ports before plating, the bore is offset 0.35mm toward the front at the top and 0.30mm toward the back at the bottom. Turns out he used a hone for the whole 2.1mm!! The guy says it 'should be ok', I'm really not impressed, not sure what to do with it from here. The difference in squish front to back would be 0.3mm so that limits what I can do there, if it was bored out to 72mm it would clean up, but I don't want to go there.

[Grumph]

Pure enthusiasm Dave! Plus I seem to have made quite of lot of friends recently when flew to the other side of the world to race 50s! The ~$3000 in insurance isn't cheap but the experiences and memories will always be worth it.

And yeah, our machines are uhhhh, quite primitive MOST of these 50s are more developed and have better gear on them than any 125GP bike or 250GP bike in New Zealand. Which makes sense given our distance from European professional teams and racing. I've learnt a lot already. I truly think F5 should adopt Freetech rules. It's one hell of a class! I'd like to ride a Freetech level 50 against the 250 production bikes in New Zealand. I think I could beat most of them with this level of tech.

You most probably could - on Levels anyway, (cough)...