ESE's works engine tuner

[wobbly]

Running a KT100 is fraught with heat problems, as it affects every part of the testing.
Simply put, you MUST have the same head temp and case temp at the start of every test.
Then monitor the egt at the end of each test.
For example you can change the pipe length, run up the engine to get your reference head and case temp.
But the egt at peak rpm may be 100* lower.
So you must then turn the tap and change the jetting.
This then means repeat the test, until you reach the same egt as previously.
Then overlay the curves to see if the new pipe length actually is better than the last one.
All you are doing is replicating what would happen on the track,but making very sure the conditions are perfectly equal.
This enables the 1/10 Hp resolution in changes to be seen with confidence, as head or case or egt temp has a way bigger influence on the dyno power reading, than any pipe or small port timing change would ever produce.

Same issue with a water cooled 125.
If the change produces a change in egt, then you must go back and rejet and rerun the test.
On track we will always be shooting for a reference egt,by changing jets based on the current air conditions,no matter what the port timing or the ignition curve or the pipe shape,may be.
So the dyno result must reflect this process to be able to document on track reality and thus performance, with any useful accuracy.

[dinamik2t]

Wob, with air-cooled engines do you simulate somehow the stream of air cooling the cylinder/head ?
This (air-cooling in general) must be a good reason for power losses between sim-dyno. Do you have any idea of the efficiency of the air-cooling system described in EngMod?

[Brian d marge]

Wob, with air-cooled engines do you simulate somehow the stream of air cooling the cylinder/head ?
This (air-cooling in general) must be a good reason for power losses between sim-dyno. Do you have any idea of the efficiency of the air-cooling system described in EngMod?

Not sure of your Eng mod , but the design of the fins I can help I have some papers , on them somewhere

Stephen

[dinamik2t]

Thank you!
Would you mean this? http://users.uoa.gr/~sph0800108/mode...e%20Engine.pdf

I remember reading another document somewhere about head fin design, but I cannot locate at the moment.

[wobbly]

I have never done a sim of an air cooled, Neels was after a dyno run of a stock KT and pipe a while ago for some students using his code for a project.
But on the dyno for sure you need to simulate the air flow over the case /cylinder/head to get repeatable results.

[F5 Dave]

So is it fair to say that the closer to the edge the more critical temp is to performance?

Reason I suggest that is we spun up my mates VJ23 (70 degree Jap market only but derestricted) and the curves overlayed perfectly over 3 runs, there was a bit of delay between the runs & the engine got hotter. The test started at say 55* & ended at 71*. Couldn't pick the curves from each other.

Btw 60hp @ ~11,200 which meant 30hp for each 125 cylinder (ignoring less losses of a twin) on a std road engine that can run on 91 oct. Pretty good considering the squish is probably a mile wide. The old VJ22 does about 52 on similar dyno.

But because of the comp being low maybe it is [edit] more- tolerant of temp diff?

[dmcca]

Simply put, you MUST have the same head temp and case temp at the start of every test.

In a water cooled engine is it reasonable to just use coolant temp as a blanket temp reference instead of head, case and plug temp on an air cooled engine?

I've noticed using my digatron unit that coolant temp (taken at head exit) and plug temp are always within 20* of each other on my bike during normal riding and always move simultaneously... Pretty much what I expected as the coolant significantly masks the true plug temp.

[wobbly]

The KT100 is thermally borderline with a proper header and pipe.
Make anything more than about 17 at peak and the engine will go away after 3 laps on the track.
I spent around 3 months full time on the dyno, and could get over 20 Hp, but on track none of those pipes could be used in a race.
So I concentrated on generating a flat downsloping torque curve that gave plenty of bottom and overev power, with no hump in the graph that would over heat the finning.
As soon I did the engine would heat fade and loose around 20% of its power everywhere.

A watercooled engine should start all the tests at the same water temp,as I have found that a full house 125 will loose around 2 Hp if run at 70* instead of 50*.
The crank/cases heating up looses power as well,so I try and keep this as constant as possible.
I have never run a "stock " type bike engine, but I would guess that if you started the test at 70, you would loose power as it heated up further from there.
A CR125 engine as run in SKUSA box stock with a pipe would loose 1.5 if i overheated it during a dyno run from 6000 to 12000 - ruining the test.

[Frits Overmars]

...Frits is right ( as usuall ) about the acceleration dyno being the most useful. I set up the engine gear ratio to test, so it accelerates as it would as close to track conditions as possible. But an eddy current can be set up to work exactly like an inertia, simply by using the constant load mode. Then the absorber applies the same load to the engine all the time, just like a steel wheel or roller.

Thanks for the flowers, Wob. But an inertia roller does not apply the same load to the engine all the time. In a situation where the revs do not increase, the roller does not put any load on the engine at all. Its load is acceleration-dependent and that is practically impossible to achieve with any brake; the brake governing software won't know what to do until after the 'event'.

Advantage is that on say a Dynojet you can easily dial up the load needed in % terms, to get the acceleration rate you want. We use that facility with a twist - program it to increase the load with roller speed.
Thus when doing an all gear run, the load increases just like the wind drag with increasing speed - so the acceleration rate decreases.
Perfectly mimicking the track conditions. Means you can dial in the ignition and fuelling at very high acceleration rates in the lower gears, then do the same at slower rates in 5th/6th.

Right, mate. You can also use it to 'brake away' some of the engine torque and measure a strong engine on a light inertia dyno, and still achieve realistic acceleration times.

[wobbly]

Dead right Frits,but for the usual situation I encounter,where I build engines somewhere near well tuned to begin with, they are always trying to accelerate
the brake during a test - so I havnt encountered the "not enough power to accelerate the drum " syndrome.
Is this what you are alluding to?

[Frits Overmars]

Dead right Frits,but for the usual situation I encounter,where I build engines somewhere near well tuned to begin with, they are always trying to accelerate the brake during a test - so I havnt encountered the "not enough power to accelerate the drum " syndrome. Is this what you are alluding to?

Yes, I tried to clarify the fundamental difference between acceleration-dependent loading of an engine and just applying a braking torque. We both agree that an inertial dyno is the best tool for developing competition engines, and that a combination of such a dyno with a brake (usually an eddy current brake) is nicer still, but at a cost. In case you do not have deep pockets, a simple inertial dyno is not only the cheapest choice, but also the best one.

[Yow Ling]

In case you do not have deep pockets, a simple inertial dyno is not only the cheapest choice, but also the best one.

Haha not many deep pockets in bucket racing, and the ones that are deep are Gorse lined

[Drew]

Haha not many deep pockets in bucket racing, and the ones that are deep are Gorse lined

Mine are so deep I can't reach anything in them. When I get brave and try, only then do I find the gorse.

Should the situation be so dire as to continue digging, I still come up empty because there was nothing to be hard to get in the first place.

Do I qualify to ride buckets?

[F5 Dave]

no, but show up & you can wave a flag.

[Drew]

no, but show up & you can wave a flag.

I did that already! But don't tell the real racing fraternity, I've got them just where I want them for now.