ESE's works engine tuner

[Niels Abildgaard]

Muscle muffler for 2-stroke boxers

We finally tested it and got 1,5 power increase compare straight pipe exhaust.
Seems 2-stroke motocycle boxers is rare if ever exist. But...

There was many 2 cylinder boxer 2 stroke MCs in DDR.


https://de.wikipedia.org/wiki/MZ_BK_350


It was made as a poor mans BMW with shaft drive because DDR could not make MC chains.
The reaction torque variation from a two stroke boxer is just as nasty as from a single cylinder.
No good for aircrafts either.
Make a V2 instead.

[shnaggs]

The STA values in EngMod are at the crank , and are directly variable by the Combustion Efficiency value entered.
But in any case there will always be a drop in displayed Hp depending on where it is measured.
At the rear wheel on a Dynojet , with the tyre and chain friction involved, as well as the primary drive /cluster , as well as Dynojets well known fudge factor
the reduction is 12.5 to 15% - I have seen this hundreds of times between the calculated power in Engmod and the RWHp figure.
On an inertia dyno with a chain on the countershaft sprocket , as is mostly used on karts , its around 7 -10%.

Re the STA figures for the KTM150 , the value for the Ex port itself is near on irrelevant.
In fact if its small , as in this case , that is exactly what we have been shooting for in the last 10 years - getting the duct volume down , smaller and smaller , by lifting the floor
above BDC and filling in the corner rads below the TPO.
Having the Blowdown and the Transfer STA matching is what is needed where the effective efficiency are both similar.
But this is affected by the scavenging model used to correct the efficiency of say crap transfer ducts , and in this case the transfer STA needs to be lifted above the EX blowdown due
to the real Cd of the ports.

But I just noticed that the STA numbers are generated at 11750 - so this must be used with a kart or road race type pipe , as no way would it be of any use on a MX track , peaking that high.
Then if being used in a kart or road race end use , the power is way low for that rpm , as we get 45 Engmod Hp @ 11750 from a stock 2002 CR125 with just a pipe change.
And that translates to close to 40 Hp at the sprocket.

Thanks for the explanation Wob. I understand that different dynos and whether wheel power or crank power is calculated will make a difference in the power reading.

I'm not too concerned with what my power number is, more just trying to wrap my head around this whole 'black magic' of 2 stroke tuning. See ive been messing about with different inlet valve configurations with no gain to be had. I was thinking that maybe its pointless to be messing around with inlet configs when the exhaust might be limiting power? But I know that nothing can be this cut and dry, and that all the inter workings of the 2 stroke must work as one.

RE the STA RPM. On the dyno the bike peaks right at 11750 in stock form, so I put that RPM in the sim for the calc. You think that HP number is low for that RPM? Take into account that this is indeed a 125, the data pack was made off a KTM150 pack I had already made. So thats why the STA says its for a 150.

-thanks

[wobbly]

Its not as simple as understanding the different dyno readings - the bottom line is that you will never see the crank power as simulated by EngMod on any dyno,
unless its connected to the ignition nut.
Or you can introduce a fudge factor ,like adjusting the inertia value so that you get a reading 10% high for example - if you really want to see the same results as the sim.
But you are right - we are dealing with small delta's on a dyno, to find what works and what doesnt, as long as your test procedure gives very repeatable results the actual number doesnt matter much.

Re the KTM , they all use VeeForce as stock I believe , so its very hard to get real improvements with these as you are severely limited in petal configuration , and making new stuffers is a nightmare.
Whereas the SKUSA CR125 reed block is easily able to be changed to give an extra 3 Hp simply by having differing petals top and bottom, and adding staggered backups to force symmetric inflow to the case..
If the late 125 is anything like the smaller engines , then there are big gains hiding in re configuring the A port hooks.
But of course the sim cannot replicate this type of scavenging improvement.
If you are using the engine in MX, then yes having it peak at 11750 will by definition mean that the pipe / porting is skewed toward making top end power - and that isnt what wins in short track dirt racing.
I would be looking at ways to pump up the upper mid that it must be lacking simply due to the peak rpm number.

[shnaggs]

Its not as simple as understanding the different dyno readings - the bottom line is that you will never see the crank power as simulated by EngMod on any dyno,
unless its connected to the ignition nut.
Or you can introduce a fudge factor ,like adjusting the inertia value so that you get a reading 10% high for example - if you really want to see the same results as the sim.
But you are right - we are dealing with small delta's on a dyno, to find what works and what doesnt, as long as your test procedure gives very repeatable results the actual number doesnt matter much.

Re the KTM , they all use VeeForce as stock I believe , so its very hard to get real improvements with these as you are severely limited in petal configuration , and making new stuffers is a nightmare.
Whereas the SKUSA CR125 reed block is easily able to be changed to give an extra 3 Hp simply by having differing petals top and bottom, and adding staggered backups to force symmetric inflow to the case..
If the late 125 is anything like the smaller engines , then there are big gains hiding in re configuring the A port hooks.
But of course the sim cannot replicate this type of scavenging improvement.
If you are using the engine in MX, then yes having it peak at 11750 will by definition mean that the pipe / porting is skewed toward making top end power - and that isnt what wins in short track dirt racing.
I would be looking at ways to pump up the upper mid that it must be lacking simply due to the peak rpm number.

Once again, thanks Wobbly!

The standard reed valve in these newer KTM's are their own version of a Vforce (w-block). They get the reeds from Carbontech, which is Boyesen's sister company which is made all in house I believe. I think Honda GP was using Carbontech reeds back in the day FWIW.

I agree that making the power band wider would be more desirable and useful. So, what you are saying is that the Exh port window area is not as crucial than the transfer port STA and the Blowdown STA, unless we are talking about an all out Kart/GP racer? So, if I bring the Exhaust STA value up to match the other STA's, I would most likely bump peak HP up but may loose some up the front side?

Thanks

[peewee]

carbontech petals seem good. had the same set in the methanol nitro bike since day one , last summer sometime. holding up fine i would say

[wobbly]

NO - adding area to the lower part of the Ex port ( below TPO ) will not increase power anywhere , so is not a " design " element I would use for kart/GP or anything for that matter.
As I said we have been trying for years to reduce the duct volume , at the port end area , as well as using my nozzle idea at the exit face end.
BUT , reducing the lower area further only works effectively IF you have already sufficient Blowdown , matched to the power you are looking for.

If you are not going to be going into pipe changes, then there is alot to be had tuning the powervalve and ignition curves.
So if you are really serious about this , then an Ignitech driving a cable connected servo on the PV is the go , and of course the ignition can then be tailored specifically to whatever mods you do.

[tdc211]

quote
But I just noticed that the STA numbers are generated at 11750 - so this must be used with a kart or road race type pipe , as no way would it be of any use on a MX track , peaking that high.


no Wob it peaks at 11800ish on pump with oem mx pipe, stock.
has pretty much no ign in it and 845ish pipe, 33ish/66ish, give or take ,29ish hp at 9000, (on more than one dyno) , isn't a slouch for mx

[TZ350]

A very stock Suzuki GP100 fitted with an un molested (but replated) NSR cylinder.

The only modification is a de stroked crank. It still has the original carburetor and no cylinder porting.

It will be interesting to see what it makes on the dyno tonight. Our guess is about 26 rwhp.

[F5 Dave]

And is there a spacer increasing volume and allowing 6 speed space?

[wobbly]

Looking at the power curves , I can see a comparison of two , one making 38 @ 11800 the other making 36 @ 11400.
But both have a big torque hole at 10500.
To me this would normally tell me the PV is fully open too soon , but then I look at the KTM STA sheet and see that the Aux ports are only 0.3mm below the main.
This tuning automatically kills the mid power big time at the expense of some top end and overev.
The 845 pipe is completely normal and has been used forever , so its the ports / PV / ignition that need looking at.
From my limited experience of actually doing an MX engine properly ( once , including data logging to see where and how often the mid power Vs overev is really used on track ) then keeping the
36 Hp curve but adding 4 Hp at 10500 would cut way faster lap times - been there done it, won the Nationals.
Its easy to do , as the 191 Ex duration means huge superposition is available to give a really flat torque curve with a ton of area under the Hp graph.

[TZ350]

Follow the link to read the whole story about Team ESE's GP/NSR110cc engine build. You will have to follow the links to see the whole post, pictures and related links.

A very stock Suzuki GP100 fitted with an un molested (but replated) NSR cylinder. The only modification is a de stroked crank with a RD400 rod and cut rotary valve 145/85. It still has the original carburetor and no cylinder or inlet porting.

And is there a spacer increasing volume and allowing 6 speed space?

No..... there are several versions of these GP/NSR110 engines but this particular engine is a very deliberate effort to see what can be achieved without doing very much.

This engine is as basic as can be and if it works, easily duplicated.



Ok... now we know. Basic GP-NSR110 25rwhp. No porting, no trick parts, just a basic Suzuki GP100 bottom end fitted with a stock NSR250 cylinder and crappy NSR head and still running the stock Suzuki GP 24mm carburetor.

[tdc211]

Thanks for the explanation Wob. I understand that different dynos and whether wheel power or crank power is calculated will make a difference in the power reading.

I'm not too concerned with what my power number is, more just trying to wrap my head around this whole 'black magic' of 2 stroke tuning. See ive been messing about with different inlet valve configurations with no gain to be had. I was thinking

that maybe its pointless to be messing around with inlet configs when the exhaust might be limiting power? But I know that nothing can be this cut and dry, and that all the inter workings of the 2 stroke must work as one.

RE the STA RPM. On the dyno the bike peaks right at 11750 in stock form, so I put that RPM in the sim for the calc. You think that HP number is low for that RPM? Take into account that this is indeed a 125, the data pack was made off a KTM150 pack I had already made. So thats why the STA says its for a 150.

-thanks

Drop the head some with the oem pipe/silencer. . Shouldn't loose rpm. Pump gas. That means machining a new insert.

[dutchpower]

Looking at the power curves , I can see a comparison of two , one making 38 @ 11800 the other making 36 @ 11400.
But both have a big torque hole at 10500.
To me this would normally tell me the PV is fully open too soon , but then I look at the KTM STA sheet and see that the Aux ports are only 0.3mm below the main.
This tuning automatically kills the mid power big time at the expense of some top end and overev.
The 845 pipe is completely normal and has been used forever , so its the ports / PV / ignition that need looking at.
From my limited experience of actually doing an MX engine properly ( once , including data logging to see where and how often the mid power Vs overev is really used on track ) then keeping the
36 Hp curve but adding 4 Hp at 10500 would cut way faster lap times - been there done it, won the Nationals.
Its easy to do , as the 191 Ex duration means huge superposition is available to give a really flat torque curve with a ton of area under the Hp graph.

Here ign. curve KTM 125 '18

[TZ350]

Follow the link to read the whole story about Team ESE's GP/NSR110cc engine build. You will have to follow the links to see the whole post, pictures and related links.

Ok... now we know. The basic GP-NSR110 build is 25rwhp. Basic because we wanted to make something that you did not need to be a 2T tuning expert to re produce.

No porting, no trick parts, just a basic Suzuki GP100 bottom end with a de stroked crank, cut rotary valve 145/85 and fitted with a stock NSR250 cylinder and crappy NSR head and still running the stock Suzuki GP 24mm carburetor.

[F5 Dave]

Looks like a great formula Rob. Clearly NF4 pipes aren't that common and some over rev would be nice but that's well useable with careful shifting.