Thundermax Injector Timing - what is it for?

[hdrider]

In the later updates to the Tmzx Software I saw an item called "injector timing" appear in the basic settings.  It set at 400deg but can be user changed, however there is no info on what it is or what it does.

I asked ThunderMax support and they told me it wasn't supposed to be user adjustable and not to change it.  Sounded like a tall tale to me.

So .... what is it and what is it for -- anybody know?

[Admiral Akbar]

In the later updates to the Tmzx Software I saw an item called "injector timing" appear in the basic settings.  It set at 400deg but can be user changed, however there is no info on what it is or what it does.

I asked ThunderMax support and they told me it wasn't supposed to be user adjustable and not to change it.  Sounded like a tall tale to me.

So .... what is it and what is it for -- anybody know?

It's spray start in degrees after tdc (0 degrees )start of intake stroke.. The cycle starts there..

Max

[hdrider]

Would there ever be a reason to change this setting for a performance build?

[Admiral Akbar]

Would there ever be a reason to change this setting for a performance build?

Nope.. Early maps had it set to 360-368.. If you went to a larger injector it is better to set it to 400 or you can get a little stumble at cruise.. Setting it to 400 is fine for most other stuff.. I think that they added that feature when they found issues with larger injectors.. For the most part it is best left alone.. Might be interesting to mess with on the dyno if you have injectors running close to their max duty cycle.. Don't know if it would do anything..

Max

[hdrider]

If its start of injector cycle after TDC of the intake stroke, then 400deg would be 40deg after TDC of the compression stroke - is that correct?  So the injectors would fire even before the start of the exhaust stroke?  I'm having a hard time visualizing this.

[Barrett]

I went to 380 and mine seemed better.. smooth as can be with 4.9's too..

[hdrider]

I went to 380 and mine seemed better.. smooth as can be with 4.9's too..

Mine's smooth at 400, but I've got 5.3g/s injectors.

[Admiral Akbar]

If its start of injector cycle after TDC of the intake stroke, then 400deg would be 40deg after TDC of the compression stroke - is that correct?  So the injectors would fire even before the start of the exhaust stroke?  I'm having a hard time visualizing this.

You got it right.. Techically 40 deg into the power stroke and the injector is dumping fuel into the port.. At least that was what the TH engineer said. I asked twice and got the same answer.
Max

[Admiral Akbar]

Would there ever be a reason to change this setting for a performance build?

Nope.. Early maps had it set to 360-368.. If you went to a larger injector it is better to set it to 400 or you can get a little stumble at cruise.. Setting it to 400 is fine for most other stuff.. I think that they added that feature when they found issues with larger injectors.. For the most part it is best left alone.. Might be interesting to mess with on the dyno if you have injectors running close to their max duty cycle.. Don't know if it would do anything..

Max

Fwiw I had this backwards.. Early maps had it set to 392.. Bigger injector seem to work at smaller numbers..


Max

[7hogs]

5.3's set at 376 bike runs a lot smoother and idle is very steady. Gas mileage went up 5 mpg and plugs look good cruise is set at 13.773 motor is a 117 and Tmax

[hdrider]

5.3's set at 376 bike runs a lot smoother and idle is very steady. Gas mileage went up 5 mpg and plugs look good cruise is set at 13.773 motor is a 117 and Tmax

Interesting.  Did you change the injector timing just to see what would happen and did you need to change anything else to compensate for the new injector timing?

[7hogs]

5.3's set at 376 bike runs a lot smoother and idle is very steady. Gas mileage went up 5 mpg and plugs look good cruise is set at 13.773 motor is a 117 and Tmax

Interesting.  Did you change the injector timing just to see what would happen and did you need to change anything else to compensate for the new injector timing?

Bored one day changed it and of idle is way smoother and the bike is much happier no other changes made just keeping an eye on the plugs

[Eglider05]

I was just killing some time trying to learn more about the TMAX, and am i ever glad I came across this thread. I've had a low rpm surge ever since I built my 120" with a HPI 58" and 5.3 injectors. It was nothing terrible and I just learned to live with it. After reading this I went out and changed it from 400 to 376. This completely took care of the surge and the bike just plain runs smoother. Thanks guys!

Rick

[Admiral Akbar]

I was just killing some time trying to learn more about the TMAX, and am i ever glad I came across this thread. I've had a low rpm surge ever since I built my 120" with a HPI 58" and 5.3 injectors. It was nothing terrible and I just learned to live with it. After reading this I went out and changed it from 400 to 376. This completely took care of the surge and the bike just plain runs smoother. Thanks guys!

Rick

Funny thing is that I screwed up and set it the wrong way for a trip..I set the timing to 400 deg.. I had a little bit of the hesitation but also mileage went down and engine temps came up during the trip.. I changed it back to 380 deg and picked up about 3 mpg along with the motor running cooler on a 440 mile day loop..

Max

[Eglider05]

Funny thing is that I screwed up and set it the wrong way for a trip.. I had a little bit of the hesitation but also mileage went down and engine temps came up during the trip.. I changed it back and picked up about 3 mpg along with the motor running cooler on a 440 mile day loop..

Max

I was just surprised the difference it made. I'm going to get brave and start playing around with the timing next. From what I've been reading the maps are a little on the conservative side where this is concerned.

Rick

[q1svt]

Max could you restate the logic for setting the injector timing?

Trying to follow your posts but with the "I got that backwards" "I went the wrong way" comments I'm no longer sure what is the correct way to set things based on injector sizes and TB stumbles...

Thanks

[Admiral Akbar]

Max could you restate the logic for setting the injector timing?

Trying to follow your posts but with the "I got that backwards" "I went the wrong way" comments I'm no longer sure what is the correct way to set things based on injector sizes and TB stumbles...

Thanks

Yeah you are right.. I should use real numbers.. How about this?

I was just killing some time trying to learn more about the TMAX, and am i ever glad I came across this thread. I've had a low rpm surge ever since I built my 120" with a HPI 58" and 5.3 injectors. It was nothing terrible and I just learned to live with it. After reading this I went out and changed it from 400 to 376. This completely took care of the surge and the bike just plain runs smoother. Thanks guys!

Rick

Funny thing is that I screwed up and set it the wrong way for a trip..I set the timing to 400 deg.. I had a little bit of the hesitation but also mileage went down and engine temps came up during the trip.. I changed it back to 380 deg and picked up about 3 mpg along with the motor running cooler on a 440 mile day loop..

Max

Max

[Bigbluff]

Hey Max,

Did you ever settle for sure whether the injector timing pulse setting, in degrees, is after TDC or after the ignition timing pulse? Just seems to me that it would make sense for it to be after the ignition timing pulse and for essentially the same reason that the ignition timing has to advance as RPM increase. That would advance the injector timing pulse too if it was based upon ignition timing.

On the other hand...as RPM increase, the timing of the start of the injector pulse becomes less important... so basing it on TDC might make sense...

I'm just trying to figure out if there is a way to calculate the best number to put in for injector timing. I've read that the pulse should start on a closed intake valve...but my intake valve begins to open at 16* BTDC. With that intake valve opening, there is no way, using the slide in the TMax software, since the minimum is 360...which would be 16* too late...if I'm calculating it correctly...and I am the first to recognize that I may not be calculating it correctly. But if it is based upon when the ignition fires...well...that has possibilities of making the 360-400 range make sense... If that's the case, then we only need to know what range of ignition advance we are using in the light load cruise range and then calculate from there when the intake valve will just be beginning to open...and set it for just a little before that...  Yes? No?

[Bigbluff]

Finally a definitive answer!

http://harleytechtalk.com/htt/index.php/topic,77858.msg860662.html#msg860662