ESE's works engine tuner

[husaberg]

Flettner, you can jet a carburetor pretty close on the stand.

What does it do when you hold throttle just above idle? Does it race up in rpm? If yes, your pilot and needle root are good.

What about 1/8 and 1/4?

Just listen carefully, does it blubber and then race up?

You'll get bad dips on dyno if it has to accelerate through these rich conditions.... even though you are testing wfo... it has to go through these rich conditions which causes false main jet readings.

Hi have a look at page one of the thread.

https://www.kiwibiker.co.nz/forums/s...s-engine-tuner

[F5 Dave]

Geez, welcome back to 2008. Thought I knew something for a page or two.

[Frits Overmars]

This is Thomas a Vietnamese race mechanic.... he starts with a main jet so big the bike floods at about half throttle (apparently this proves the oriface of the needle/needle jet combo is big enough) and then he slowly step by step works back until it runs clean.

That's the way. Most people think it's safe to jet up a bit and see what happens.
Here's what can happen. An engine runs so lean that it does not produce any power or heat.
Now you jet up, so it will produce more power and more heat, while still running too lean for its own health. That's not always fatal, but it can be.
If you jet up, start with a big step and then work back carefully, like Thomas did.

[wobbly]

I first tried the " so rich it wont run " thing about 10 years ago , by taking out the main jet completely.
Well in fact I had forgotten to replace it , being in a rush in the pits.
In that instance the thing would rev up perfectly to about 12,000 at WOT then fell flat on its face.
Made it very obvious the needle end / emulsion tube annulus was way too small.
So that got changed and I started rejetting the main.

That very same day was the first time I had used a fast response EGT gauge to assist with tuning.
It was also the first day I discovered that when the EGT flat lines , its not rich , its starting to deto and is lean AF.
As I then jetted down 1 size and it seized - destroying a brand new engine.
That lesson was so traumatic it has never left me - so if I say , quit guessing as well on this subject, and use data to inform your tuning choices , it has nothing to do with being a prickly bugger
its very hard won experience talking.

Here is the best value fast probe and gauge on the market - https://www.exhaustgas.com/ProductDe...D=71&BasketID=

[ApolloMotoMoto]

A lot of interesting discussion on the topic of Correction Factors (differnt places, but it floats around).

And within those discussion was obviouslly some detailing of the in-and-outs of running a 2-stroke dyno cell...

Well, me and the team are currently getting our new PerformanceTrends dyno settled in its new home...

(and honestly pretty close to ditching the PerformanceTrends datalogger for a SportsDevices unit, once the initial setup is complete, and we confirm everything works as its supposed to, we are changing over to SportsDevices DAQ and software for access to 'Frits FOS 2-Stroke Correction Factor)

...and I have been reviewing a lot of screenshots I have taken from Frits and Wayne....

I believe I have come to the conlusion that neither of you use a Lambda/O2 sensor at all.
-I have read Frits paper on the confounding results one will get if they use "standard" AFR tuning methodology on a 2-stroke engine using a standard O2 sensor, and I am pretty sure I understand it.


So, my first question is;

A: Do you have -any- use for a Lambda/O2 sensor for running an engine on the dyno, or for tuning a carburetor "on location" at the track?

And my next question is;

B: If not, what is your procedure for establishing a proper "baseline" jetting in the carburetor, from which you will adjust to new conditions using RAD and EGT?


I believe I have gathered that, when starting from a known good baseline for the jetting in the carb for a specific RAD, and having a known good baseline EGT for the pipe, the procedure looks like this:

Baseline Carb Setting + Baseline EGT + Baseline RAD is written in stone somewhere useful and handy.

You arrive at some new location.

First thing first, what is the current RAD at the new location?

Next up, what is the difference between current RAD and the Baseline RAD?

Before you even run the engine, the jetting in the carb is adjusted a set amount given the difference in RAD.

To make a very simple example; if RAD is 5 points lower than baseline, the jetting is made 5 steps leaner.
(I have seen the graphed curve plot posted by Wayne a few times for making this determination...)

Now, with jetting adjusted as a factor of the difference in RAD, the engine is run up to temp, and pulled under load long enough to take an EGT reading from the pipe.

Does the CURRENT EGT match the Baseline EGT?

If no, fine-tune jetting until you achieve the Baseline EGT in the new current RAD conditions.

If yes, then hooray, you are ready to go racing if you are at the track....

If you are starting a new day of dyno testing, that means its time to make a baseline pass with your baseline setup.

Now you have a baseline run on a brand new day of testing, with different RAD from your previous baseline.

Apply your preferred correction factor to the new days baseline run and compare this CORRECTED curve to your previous baselines CORRECTED curve.

Do the baseline curves match -exactly- for the two different RAD conditions?

If no, your correction factor sucks ass, and you will have the pleasure of re-performing the baseline run everytime RAD changes if you want to accurately measure the difference between the new parts or ideas you area trying to test.

If yes, then hooray, your correction factor can be trusted to accurately compensate for changes in RAD as you perform A-B testing.


Last Question:

C: Do I have that right?

[wobbly]

Answer to the first question is no - Lambda I have available as an input on my SportDevices , but its only useful for determining A/F ratios at part throttle or transient conditions
with a completely new carb/engine setup.
To do this reliably the sensor should be right at the front of the muffler , screwed into a bung fitted to the body, that fits surrounding the perforated within the muffler.
But here is the kicker - Lambda tells you absolutely nothing about the limiting factor in 2T tuning - the onset of deto.
Only a fast response EGT probe and data log can give you this.

Thus on the dyno it is easy to review the EGT traces as you jet down - and each jet will increase the EGT by a quite accurate set amount.
When you go down a jet and the EGT does not increase - this is deto, go back one and that is your best power EGT at a specific RAD ( I use Density Altitude as the scale is bigger and the changes easier to plot ).
This is one data point on your jetting chart - but you must be sure that your test run time and water temps match what is seen on track.
So from now on , be it on the dyno , or at the track , you have a target EGT.

With different weather on a different day you can initially run rich and jet down to that specific EGT - now you have two data points linking RAD and jet size, determined by EGT for best power.
This is the graph I have published several times for KZ engines with differing tune and fuels, and thus EGT.
Looking at the red line on the graph , 5 points of RAD , say 95 to 100 , in this case gives an 8 jet split.
I have a full set of pinned jets and thus can change jetting in 0.01mm increments , but a normal jet set would only have 4 - in this case 140,142,145, 148 for a Dellorto.
You can also see on that line several other data points I have added to ensure accuracy for any setting with that engine and with that fuel.

Then yes , as you say , if you apply the above logic and rejet to a specific EGT , on different days , and your correction gives overlaying curves , then no arse sucking is involved.
The accuracy of the correction is determined by the Density Altitude number , thus I have used the 3 way calibration available for the SportDevices weather station , so it matches exactly the local airport numbers I can
get anytime on my phone - ensuring that no matter where I am the data I am using is from super accurate airport stations , as planes are not allowed to fall out of the sky.

[ApolloMotoMoto]

Thus on the dyno it is easy to review the EGT traces as you jet down - and each jet will increase the EGT by a quite accurate set amount.
When you go down a jet and the EGT does not increase - this is deto, go back one and that is your best power EGT at a specific RAD ( I use Density Altitude as the scale is bigger and the changes easier to plot ).
This is one data point on your jetting chart - but you must be sure that your test run time and water temps match what is seen on track.
So from now on , be it on the dyno , or at the track , you have a target EGT.

Thank you VERY MUCH!

/Screenshot saved.


We will be following this procedure to a T.

PerformanceTrends sold us a whole range of K-type thermocouples, with one specifically a "fast response" unit for measuring EGT; we will see how well it works.

-I know you have a preferred 'fast response' thermocouple, but I dont have the part number saved, do you mind digging it up for me?

Thanks again!


-Sean

[Flettner]

Inside the AG cylinder, for what its worth.

[husaberg]

Looking at that helical primary and knowing how bad those ratios are I can't help but think that MB100 or a DT175 would make a better bottom end stating point. I will see if I can find you some AG175 bottom ends, pretty sure the 6 speed DT ratios would go in, or MX ones
That said the finish on the cylinder fining is amazing Neil, a real credit to your craftsmanship.

[wobbly]

https://www.exhaustgas.com/ProductDe...sub1&BasketID=

Stinger open tip , can be ordered with any length of extension - only probe with a 2 year warranty.
I have sold literally hundreds for karting use - never had a probe failure.

[Flettner]

Looking at that helical primary and knowing how bad those ratios are I can't help but think that MB100 or a DT175 would make a better bottom end stating point. I will see if I can find you some AG175 bottom ends, pretty sure the 6 speed DT ratios would go in, or MX ones
That said the finish on the cylinder fining is amazing Neil, a real credit to your craftsmanship.

I'm useing DT100 crank gear and clutch basket, higher gears ratio than the AG. Also allows for fitment of AG200 plates and springs. Much stronger.
Finish, yes I'm happy how the cylinder cast but if you zoom in you can see the bottom fin, a bit rough but good enough for a one off test unit.

[SwePatrick]

I see you talk about jetting carburetors, money saving tip!
This is my take on getting into the ballpark without spending dollars on buying a lot of rods(lectron)
When engine is somewhat running good after grinding the rod, you can measure it and buy the ones that are most similar to your grind.
Or, if it actually just wokrs fine, keep the grinded rod =)

Part one:


Part 'two':

[rtechracing]

Does anyone have a copy of the SAE 850085A and 930503 papers refered to in the FOS Air density correction factor? I will send them to Performance Trends so that they can implement the FOS correction in their dyno software.

Thanks

[ApolloMotoMoto]

Does anyone have a copy of the SAE 850085A and 930503 papers refered to in the FOS Air density correction factor? I will send them to Performance Trends so that they can implement the FOS correction in their dyno software.

Thanks

TEST


SAE 850085 should be attached to this post as a downloadable PDF.

[ApolloMotoMoto]

Does anyone have a copy of the SAE 850085A and 930503 papers refered to in the FOS Air density correction factor? I will send them to Performance Trends so that they can implement the FOS correction in their dyno software.

Thanks

Working on aquiring 930503:

Harari, R., Sher, E., The Effect of Ambient Pressure on the Performance Map of a Two-Stroke SI Engine
-SAE International Congress & Exposition, Detroit,MI, Pg 115-123, 01 March 1993.

Looks like I am going to have to just pay for it directly from the SAE.