Ski-Doo Snowmobiles Forum banner

ETEC Dial A Jet

13K views 39 replies 11 participants last post by  HemiChallenger 
#1 ·
Always wanted a range of fuel delivery that was simple and easy to adjust in the field for the etec.

Purchased these components last spring but did not assemble them tell today. This is nothing new or nothing i am wanting to market. Just a personal tuning tool for the complicated etec fuel system. I am sure some of our vendors have this same gizmo for tuning fuel delivery on there modified Etecs. It is built fully plug and play.

Just need some quality snow to test it out... Dang it.

Glasses Head Vision care Eye Eyewear
 

Attachments

See less See more
1
  • Like
Reactions: Sorcerer
#2 · (Edited)
Is that a POT?

Below is an article that Joey Strub @ BMP had once on his web site.



AFR vs EGT
By Joey Strub

(Link is now dead)

Air Fuel Ratio (AFR) is the ratio of Air(Oxygen) to Fuel(Gasoline). 14.7 units of Oxygen to 1 unit of Gasoline is whats called the Gasoline Stoichiometric ratio. Often AFR is displayed as a digital number, for instance 12.6 on a digit display would refer to only the units of Air. So 12.6 really means 12.6 to 1. Now that you understand what AFR is now lets go over what the different ...values of AFR really mean. At 14.7 AFR all fuel has chemically reacted with all oxygen that was available. At 14.7 there no fuel or oxygen remaining. This is an important number because if the number is higher than 14.7 (Lean) there is too much air and if it is high enough it will not fire at all because the flash from each fuel molecule will not flash far enough to contact the next fuel molecule so energy will be unable to pass from one to the next and the chain reaction can not occur, this is called a Lean Misfire. Another concern for AFR values 14.7 and over is that there is no unburnt fuel to carry heat out of the cylinder. Heat can be very dangerous for engine life. In contrary when values are lower than 14.7 (Rich) there is fuel remaining after flash has happened. This extra fuel has 2 main effects. The first is the engine will run cooler the richer it is because the unburnt fuel will absorb heat inside the cylinder and carry out into the exhaust. The second is that the flash will occur at a slower rate because the extra fuel molecules mixed in with the flashable fuel molecules acts like an obstacle that that flash must travel around to get to the next flashable fuel molecule. The Lower the AFR value (Richer) the slower the flash will occur. It is possible to have too many unflashable fuel molecules to for the flash to reach the next molecule, this creates a Rich Misfire. Like anything there is optimal value for AFR depending on application. Major factors that affect optimal AFR is engine type, compression, operating temperature, Octane, Ignition Timing and fuel delivery method.

Exhaust Gas Temperature (EGT) is a measurement of the temperature of the exhaust gas as its entering the exhaust system usually 6-8 inches down stream from the piston skirt if possible. Often EGT is displayed as temperature either in Fahrenheit or Celsius. Exhaust temperature is an excellent bit of information for the serious 2 Stroke tuner since you have a digital number to reference how your engine is running. In most cases the lower the EGT value is the richer/cooler the engine is running and visa versa. So you can adjust fueling to hit your desired EGT at Wide Open Throttle(WOT). Note it is quite normal have a higher safe value for Partial Throttle (sometimes 75 to 150 degrees F) since you do not have the volume of heat needed to cause damage where as that same value may be unacceptable at WOT.


Typical Wide Open Throttle (WOT) AFR Values for optimum power-
* Some engines safe values are outside of typical limits*


2 Stroke naturally aspirated Target AFR/EGT
AFR = 12:0-12.6:1
EGT = 1100-1200F

4 Stroke naturally aspirated target AFR
AFR = 12.8-13.4:1

4 Stroke Boosted target AFR
The more Cylinder Pressure the lower the number!
The lower the Octane the Lower the number!
AFR = 10.9-12.5:1


Where to install EGT bungs 2 stroke exhaust-
EGT Probe should be 6-8 inches from the piston skirt down exhaust stream, If a Y-Pipe joins the exhaust stream in this range install the EGT Probe at the closest point where you could install a hose clamp around each side as close to where the 2 join into 1.

Where to install AFR bungs 2 stroke exhaust-
For best reading without disturbing sound waves AFR bung should be installed as close to towards the engine while still in the belly portion of the pipe, this is the section where the pipe is at its largest diameter. You want to place the bung on the upper half so the sensor will not be upside down when installed (this would cause premature sensor failure).

Where to install AFR bungs 4 stroke exhaust-
Pre-muffler so it will not get inaccurate readings from reversion air pulses, If running a strait pipe 12 inches upstream of outlet should suffice. You want to place the bung on the upper half so the sensor will not be upside down when installed (this would cause premature sensor failure).


Written by Joey Strub
Bikeman Performance Plus

I wrote this to help with a basic understanding of the hows and whys. This is only the surface and claim no responsibility for any damage that results from inexperience.
 
#3 ·
It is a 25K ohm rheostat. Only trouble is it enriches the whole fuel curve. Not real tuneable vs a PCV.
 
#4 ·
Had the chance to run this thing on a stock motor 800R etec over the weekend.

Have five segments or lines on the box for a quick reference. Number 1 is Zero or open no resistance. 2 is 7K ohm. 3 is 14K ohm. 4 is 22K ohm and wide open it 25K ohm. At -20 deg C this weekend on a stock motor with small timing bump, 25K ohm is to rich. 14K ohm is ok but 7K ohm is better. Most noticeable is off/on throttle midrange richness but cleans up on wide open throttle runs.

Would be fun to try with timing cranked full advance and turn up the fuel.

Hood Motor vehicle Automotive design Automotive tire Automotive lighting
 

Attachments

#6 ·
This would be additional. Stock sensor is still in place.
 
#7 · (Edited by Moderator)
I don't have the readings below -20C, but just taking a guess from the 3 shown below there is a multiplication factor or roughly 1.62 for each block of 10 degrees C. Since you were riding at -20C the sensor should show roughly 15 K + the 25 K = 40 K. This is roughly -40 C.

The 7K setting @ -20C would total ~22K or -30C. Nice find!

From Shop Manual

0 C 5.705 K
-10 C 9.102 K
-20 C 14.900 K

3.4 K difference between 0C and -10C
5.8 K difference between -10C and -20C

Estimate using 1.62 as the multiplier.

0 C 5.7 K
- 10 C 9.1 K
- 20 C 14.9 K
- 30 C 24.1 K
- 40 C 39.1 K
- 50 C 63.3 K
- 60 C 102.6 K
 
#8 ·
That is interesting info. I do not have access to the shop manual. Thanks for the information.
 
#9 · (Edited by Moderator)
Ski-B, you do know this was a brilliant idea, eh? Obviously this is an old sensor trick that began when the first cars got filled with sensors decades ago, but how often do you see this for sleds even in 2017? The irony is that folks go about their business with their hand held computers walking the corridors just like Gene Roddenberry imagined it decades ago while we see a simple POT as this magical devise lol

What brought this on was reading the topic 800 etec miss-bog (click the link) and I couldn't help to think back to your topic and how easy it would be to eliminate the Air/Fuel ratio as a likely problem. There are many other topics that would also fit the bill. Do you remember the owner who set his 800RE back to Break-In mode just to find all his problems had disappeared?
 
#10 ·
A little more tinkering with the dial a jet. On my 2016 it accepts 7K and even 14K better than the 2012 did. It seams as tho the later models are calibrated some what leaner in mid throttle.

This is all on stock engines. I do not modify my engines anymore. Sorry.
 
  • Like
Reactions: djm
#12 ·
Air temp sensor in the upper air box.
 
#14 ·
I purchased a stock air temp sensor. Then cut the end off it, to expose the metal terminals, and solder your wires to the two terminals. Heat shrink it, tape and wire loom. Kind of a pricey way of doing it...but the only way.

You can not but the terminal end from any supplier.
 
  • Like
Reactions: barski
#16 ·
I just put a switch on my dash that has 6K resistance in it and tapped into the sensor harness. now at the flick of a switch I can enrich the fuel delivery if I have to get questionable fuel or I am doing long high speed trail runs.
Wow, nice going! So how has it worked so far with the added 6K resistance? Are there areas in the rpm/load range that are more responsive?
 
#20 ·
Always wanted a range of fuel delivery that was simple and easy to adjust in the field for the etec.

Purchased these components last spring but did not assemble them tell today. This is nothing new or nothing i am wanting to market. Just a personal tuning tool for the complicated etec fuel system. I am sure some of our vendors have this same gizmo for tuning fuel delivery on there modified Etecs. It is built fully plug and play.

Just need some quality snow to test it out... Dang it.

attachicon.gif
011.jpg
Nice ! Where did you get those parts ? I need one that goes from 0 to 2000 ohm
 
#22 ·
Oh, i intend to use the resistor on my 1993 Formula Plus EFI, if the air temp sensor in the airbox should crap out, and it just might...as the ohm values seemed to high when i tested it. Sensor is obsolete, so a POT seems as the only good option... Did a search on ebay, but cant find any POT´s with included housing like the one you have.
 

Attachments

  • Like
Reactions: Daag44
#23 · (Edited by Moderator)
I purchased everything separate. All at a local electronic story. Found the Rheostat in the range i was looking for. Then purchased the box to mount the Rheostat in. Had a old knob off a Yamaha variable hand warmer switch laying around. Drilled a hole in the box, wired it, installed the knob. Then inked on some lines. 1/4 1/2 3/4 and full. Then measured the ohms at the marked ink lines, so i have some idea what the etec likes for ohm trickery, to enriching up the system.

Kind of wish i had a Big Bore or a highly ported etec, so i could put the Gizmo to work. LOL.

Rectangle Automotive lighting Gas Coin Wood


What would work better is a four position switch. With a different resister soldered to each position. Soooo you could select 6K. 12K. 18k or what ever. The four position switch would be more secure. I am allways looking to see if the rheostat has moved or been bumped. But so far it sits on the location very well, with vibration and impact.
 

Attachments

#24 ·
All right, nice work :smile_old: So you are using only 2 terminals, center and one of the end/side terminals ? Whats the third terminal for ?
 
#25 · (Edited by Moderator)
It changes the direction of the ohms. Center is input and left or right of center... just changes the Clockwise vs counter clockwise of the ohm increase. I have it set to increase ohms on the clockwise rotation.
 
  • Like
Reactions: Daag44
#26 ·
I find this an interesting post.

Questions:

1. since you are fooling the ECM could this damage the engine in any way?

2. I have a 2016 600etec MXZX and it misses or pops after a mid range run at 6500RPMs. When you stab the throttle it pops or drops out for a second then takes off. Would this help this issue? FYI- I do run 91 octane non ethanol gas and the sled is bone stock.

3 can you list the part number of the connector you bought and maybe post a close up picture of the connector (plugged in and not plugged it to see how you wired it?

Thanks
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top