timing questions...

[Ski-Dooin' it]

So, On the propane fueled yamadoo im currently having issues. A brief overview of the parts before I go crazy with whats gonig down.

03 rx1 motor with a shim in it. 9.1:1 compression

homebuilt turbo system.

ski-doo chassis.

the motor worked great all last season with the gas turbo kit. redid the turbo and converted to propane.

I built a 4-1 intake manifold with a single large throttle body on it. the tps that was on the throttle body was not compatible resitance wise compared to the stock ones. SO, I currently was trying to do some tricky little wiring projects on the thing.. but the ecu is flashing the TPS signal to me. so this is obviously throwing the timing into some sort of limpy mode.

Sled runs amazing down low and up to around 7k rpm where it just sits and pops like crazy when going WOT... if you hold it like 1/4 throttle and let the turbo spool and rev it past there it runs great... WOT runs super sweet as well, and if you chop in and out of WOT and stay above around 7500 r's its really nice. It runs great if I stay easy on it and it revs throught that spot, but If I hammer on it, it revs, then just starts to pop and stutter at that RPM, then it will spool the turbo like it has an anti-lag button on it, then revs past it. the air fuel readings look great right until it starts parting, then it reads lean, but thats because its just not firing...

my thinking is that the motor with the low comp and the high octane of propane, combined with the limp mode from computer its not able to burn it in the mid range without enough advance?? does this thought make sense?? and would it cause it to pop like that?

any thoughts would help, also, does anyone have a timing table from say an apex with rb3?? should be sorta similar and give me some ideas of what the curve should do.

 

[Wildman]

Is it by chance going rich and breaking up (are fuel will show lean in this condition also)? RB-3 piggy back just modify's the stock timing curve (you just add in a table 1 to 10 or -1 to 10). I am curious to why you lowered the compression when you were going to run on propane for fuel?

 

[Ski-Dooin' it]

I dropped the comp last season when i first turbo'd it.. and ran it on pump gas.. I am also gonna turn the boost up soon, so I actually am contemplating taking the shim out to help the bottom end.. but, thanks for the heads up on the timing control with RB3

and after watching some videos of sleds with launch control, it sounds the Exactly the same.. i have messed with some things to make the midrange leaner and it doesnt help, just sorta changes the sound a hair. the air fuel is running perfect, and im thinking it just stops igniting as its stuttering ther isnt enough advance to get on it and not burning... and then when it doesnt burn it reads super lean(i know that afr trick)

I am led to beleive that its a timing issues as i have done all sorts of tuning things and it wont run right no matter what the afr is.. when i roll through it easy, they are good, and i can change them and they show alter midrange afr, but when i give it wood in the midrange it just cant burn it, no matter what the air/fuel.

 

[dirk_03]

Timing

Why not just put the throttle position sensor on it from the carbs. Should easily enough be able to make a bracket and attach it to the throttle body. Might as well fix that first as I am sure the TPS controls timing in comparison to throttle postion and rpm. If the throttle is opened fast with the engine at low rpm I am sure the ignition is way advanced compared to if the throttle is open and the rpm is high. I had a zx9r that was carbed it was suppose to be one of the quickest throttle response bikes of the era do to the tps sensor advancing the timing giving fuel injection type throttle snap. Keep in mind that was 01 so I am sure that the rx1 motor is the same deal.

This would explain why when you ease into it it works. The timing is not all wacked out. When you can it in limp mode the timing is probally way retarded and the fuel won't ignite. added to the low compression. I would say pretty condifently that you get the tps sensor on it and calibrated and it will work.

 

[Ski-Dooin' it]

well, it just so happens that i dont have a tps anymore as I sold my carb rack, otherwise this would have been my first course of action..

after reeding up, this seems like the most logical issue, just need to make it happen... BUT, its 120 and they are currently backordered.. so not my first course of action, im gonna try to find another one that I can use in its place.. lots of universal ones to be had cheaper.

 

[Srxspec]

I think I have a spare "parts" carb rack. Shoot me an email or give me a call and I will see what I have tomorrow.

 

[Ski-Dooin' it]

perfect, I will give you a ring tommorow..

I have finally just started reading on voltage dividers and potentiometers, they are really simple, might be able to rig one out of a simple potentioeter from radioshack.. way cheaper, so worth hacking together instead of cutting up $100 factor throttle position sensor

 

[t_thall]

I would also definatly fix the tps first, some two strokes are very finicky to proper tps adjustment. If you get that fixed and it doesn't fix your misfire than a hotter set of plugs might help light it off, at least its easy to try...

 

[Ski-Dooin' it]

yeah, i got the tps off my buddys doo 800 that has an almost identical resistance pattern.. SO, i should be able to throw that in tommorow and try it out.. will be lots of fun.. i know propane likes timing as its a slow burning fuel.

if the tps helps but doesnt cure it, a hotter set of plugs will be the next order of buisness.. its harder to burn then gas, so it wouldnt hurt.

 

[mulot30th]

Your right, no timing, no power.


I did a quick test on an apex blower with a standalone ecu.

Removed the intercooler, set timing curve... to 10 degrees all the way to 10000 rpm.

Guess what?, its not able to rev past 6000rpm WOT. talk about having no power at all....

 

[Ski-Dooin' it]

yeah.. i bet.. glad to confirm that it doesnt work.. and propane is harder to burn then gas.. so im betting that if mine is in an idiot mode. its NOT helping.


im betting at WOT at around 6000 it just sits and pops and burns in the exhaust...mine blows cool blue fireballs as the propane keeps burning into the pipe when the timing is to far back.

the tps im going to try also has slotted holes so i can test the thing and advance the curve which also supposedly really helps the propane buggys take off even faster.. if you start it a hair more aggresive it should burn it like crazy down low, but thats easy to test.. so we find out tommorow.. ill be sure to update so theres info that goes with my perpetual findings.

 

[BCBoost]

yeah, i got the tps off my buddys doo 800 that has an almost identical resistance pattern.. SO, i should be able to throw that in tommorow and try it out.. will be lots of fun.. i know propane likes timing as its a slow burning fuel.

if the tps helps but doesnt cure it, a hotter set of plugs will be the next order of buisness.. its harder to burn then gas, so it wouldnt hurt.

When you get the TPS figured out you should also put in the plugs!! All the HP3 kits run the hotter plug as well as timing advance.
BC.

 

[Ski-Dooin' it]

thanks for the heads up BC.. i will go grab a set today if i feel ambitious.

would you care to let me in on how they do the timing?? just a key in the crank or what/? i know on mine with this new tps i can crank the thing forward to advance the lower end a a bit to get into the map sooner,then leaving the top the same.

thanks for the help all, makes working on the thing a littlle more productive as a lot of times i feal like im running around in the dark.

 

[BCBoost]

For your engine....machined keyway, or the easiest slot the holes for the pickup coil under the flywheel. I believe some one has a post on here...make sure you go the right way with the slots.

BC.

 

[Ski-Dooin' it]

haha.. thanks for that as well.. the tps is giving me fits.. i just need to take it into the electrical engineering lab i have tommorow so i can test things and not ahve a motor running when in testing, i can just set it down and work on it.

sounds like slotting the deal would be the best way, and i feel like a pretty sharp fellow hopefully i go the right way with the slots. any guestimates onthe kind of advance i want to do/? 1-2...10 degrees???

i appreciate the help, the propane works great besides this little issue currently. and tanks, but thats another battle dealing with practicality.