ESE's works engine tuner

[TZ350]

Suzuki GP100 with an NSR250 cylinder.



I have been working on a water cooled exhaust manifold for the Suzuki GP/NSR 110 engine.



Chambers is making good progress fitting it all into Av's old NF4 rolling chassis. He is even re cycling the original Honda RS125 NF4 expansion chamber. It will be a fun bike for us to ride.



And could be very interesting if Av takes her old NF4 for a spin.



Av peddling number 21 up the inside to take the win.

[mr bucketracer]

the front of the chamber is mighty close to the front wheel

[diesel pig]

I have to agree, When I fitted the radiator to my NF4 frame I did the same thing with unscrewing the fork springs and bottoming out the forks then fitting up the radiator with similar gap. I don't know if it is the tyre growing or the forks bending under braking or maybe a bit of both but there is a black mark on the bottom tank of the radiator after each race. I hope to fix it with a different radiator I have coming next week.

[TZ350]

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Yes we think you are right. Chambers is looking at ways to move the engine back. Even 10mm would be a help.

[Frits Overmars]

Chambers is looking at ways to move the engine back. Even 10mm would be a help.

Why not take the easy route and move the header back? Two sawcuts and one weld, and you're done. Or better still, build your own pipe, because I doubt that an NF4 pipe has the optimum dimensions for an engine with a different cylinder capacity and a different exhaust timing. The engine might feel more comfortable with a smaller initial header diameter.

BTW, for their NF4-successor NX4, Honda changed the complete engine layout in order to shorten the wheelbase and move the engine closer to the front wheel. Even 10 mm would make a difference in handling and feedback.

BTW2: tire growth on this kind of tire is wellnigh negligible. The wheel displacement is mainly due to the NF4 forks bending. The NX4 forks, or indeed most upside-down forks, are a lot better in this respect.

[ken seeber]

Wobbly, do you have any photos or info on this welded in bridge(Parent materials, filler metal, etc)?
Thanks,

I'm pretty sure Wobbly is away in Las Vegas for the SKUSA car park racing bonanza.....

[Tbh37620]

I'm pretty sure Wobbly is away in Las Vegas for the SKUSA car park racing bonanza.....

Thank you for the heads up on that. I will keep an eye out for when he returns and posts next

[TZ350]

... better still, build your own pipe, because I doubt that an NF4 pipe has the optimum dimensions for an engine with a different cylinder capacity and a different exhaust timing.

At first blush you would think so but it has proved not to be a problem.



We have done a bit of work in that area and Chambers has got quite good at constructing pipes.



Expansion chambers, I started with a RGV250 pipe then modified it to RM125 C specs then in 2009 started using a NF4 chamber.

At exhaust opening 80 deg ATDC for all the pipes all the torque curves were flat.



Typical torque curves, flat at Ex 200 duration and 70% wide and as the port width and duration was increased we got more power but the torque curve became steeper. This was typical of all four pipes RGV, RM125C, NF4, NX4.

The difference between the engine setups and pipes was the rpm at which they made maximum power. As the max power and rpm that max power was made at increased, the width of the power spread also increased, which was very handy.

When I first started using the NF4 pipe in late 2009 someone else expressed doubts about its suitability. But after a bit of thought I realized a good pipe like the NF4 or NX4 could cover a wide range of engine development.

As I developed the engine over the years I found the same length pipe can stay in tune with the new engine. Because, as the two physical effects of increased exhaust heat from more power (a longer pipe is required) and increased RPM (a shorter pipe was required), these two things neatly balanced each other.

A few calculations showed me that:-

Less power and exhaust heat plus lower max rpm equaled the tuned length of the NF4 pipe.
More power and exhaust heat plus higher max rpm equaled the same tuned length of the NF4 pipe.

And as the power and rpm continues to go up I expect the NF4 pipe to continue to be suitable.

So one pipe can be a good friend for a long time and like good friends, if you have a pipe that works, stick with it is my opinion.

There is still a lot to be gained within the engine by looking at the overall transfer ratio and trapping efficiency and the direction of the transfer streams.

BTW, for their NF4-successor NX4, Honda changed the complete engine layout in order to shorten the wheelbase and move the engine closer to the front wheel. Even 10 mm would make a difference in handling and feedback.

My own GP/NSR110 engine is tipped well forward and uses a NF4 pipe. The GP/NSR110 dyno graphs are pretty much the same as the earlier air cooled GP125 ones, the benefit will be the water cooling. Tipping the engine forward allowed me to move it forward but the angle of the engine meant I needed to run a dry sump gear box with oil sprayed over the gears.

I would love to experiment with pipe building but so far I have been unable to simulate anything in EngMod that exceeds the benefits of the NX4 or NF4 pipes. So I won't be cutting and welding thin sheet any time soon.

[husaberg]

BTW, for their NF4-successor NX4, Honda changed the complete engine layout in order to shorten the wheelbase and move the engine closer to the front wheel. Even 10 mm would make a difference in handling and feedback.

BTW2: tire growth on this kind of tire is wellnigh negligible. The wheel displacement is mainly due to the NF4 forks bending. The NX4 forks, or indeed most upside-down forks, are a lot better in this respect.

i am not so sure it was just to shorten the wheelbase as the NX4 went to a linkage rear shock which entailed a longer swingarm. Which is a benefit in itself.
The stacked layout with a balance shaft of the NX4 allows the engine to be mounted further forward. whist maintainng an acceptable wheelbase another plus.
With the rejigged engine an the different angle on the spars it endied up a few inches shorter with more forward weight bias.

My thoughts are that people are running into clearance issues as the original NF4 chassis geomerty was based on Skinny 18 inch wheels. These days people tend to drop the forks pretty low in the yokes to get them turning sharper as all these buckets now all have modern size 17" wide wheels fitted to them. plus the riders tend not to be 50-60KG teens.
The NX4 ws designed arround these factors from the very start. Other than the fatties.

NX4 WHEELBASE 1215mm (47.8 in) Caster angle 23 ° 30' Trail length 84mm (3.3 in) NF4 Wheelbase 1,260 mm (49.6) Caster angle 25 ° Trail length 95 mm (3.74 in)

[TZ350]

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An interesting read of one mans adventures racing his Post Classic TZ250 http://www.natsforum.net/viewtopic.php?f=3&t=1130

[jbiplane]

Hi guys

Want make V 2-stroke with 90 degree V-angle. I saw exist variant of V when conrods share the same finger
http://fastpic.ru/view/98/2017/1118/...a4442.png.html

but seems 90 degree pins ofset have balance and smoother torque variation. Possible make engine which
balansed like opposite and have smoothness of inline.
http://fastpic.ru/view/98/2017/1118/...1c1dc.png.html

Medium crank disk separates crank volumes in both cases. Anyone saw this idea already implemented?

(sorry dont found better way how direcly attach pictures to the post)

[Frits Overmars]

Want make V 2-stroke with 90 degree V-angle. I saw exist variant of V when conrods share the same finger... but seems 90 degree pins ofset have balance and smoother torque variation. Possible make engine which balansed like opposite and have smoothness of inline.
Medium crank disk separates crank volumes in both cases. Anyone saw this idea already implemented?

Hi Valery, a 90° V-twin with both con rods on the same big end pin has a very good balance, especially when you can keep the cylinder center lines close to each other.
It will also have a smooth torque with less variation over a crankshaft revolution than any 180°-firing twin.
A 90° V-twin with 90° offset between the big end pins would be very bad for balance, vibration and torque variation.

The idea of a center crank disk that separates the two crank volumes, is not new. It is used in many two-stroke outboard V-engines like the Suzuki V-6 below-left.
Is has also been seen in motorcycle racing. The pictures below show the 250 cc V-twin built by French dentist Jean-Bertrand Bruneau, better known as JBB.
The drawing on the far right shows his last V-2 crankshaft.

[WilDun]

Hi Valery, a 90° V-twin with both con rods on the same big end pin has a very good balance, especially when you can keep the cylinder center lines close to each other.

A 90° V-twin with 90° offset between the big end pins would be very bad for balance, vibration and torque variation.

The idea of a center crank disk that separates the two crank volumes, is not new.
Is has also been seen in motorcycle racing.

I do realize that I may not be quite up with the play here!.... but if the centre disc rotates (which it must do,) how much clearence is there between it and the crankcase and why does it have what looks like an "O" ring groove .... surely not?

[jato]

The center disc works as a labyrinth seal (no contact between surfaces and you are right - no o-ring) the groove is part of the labyrinth. probably in the order of 0.5 mm radial clearance on the lands and maybe a little less axially to allow for the inevitable bit of crank flex

[diesel62]

The center disc works as a labyrinth seal (no contact between surfaces and you are right - no o-ring) the groove is part of the labyrinth. probably in the order of 0.5 mm radial clearance on the lands and maybe a little less axially to allow for the inevitable bit of crank flex

Piston ring seal by the looks of it

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