[Lelebebbel]

After fitting 41mm FCRs over the winter, I made a post here about dyno tuning my 900SS to fine tune the jetting. There was a hang up with the dyno after the first warm up run, and for various reasons I wasn't able to get back there all summer. The bike runs quite well as is, but I'm sure there is room for improvement.

In the mean time, I figured I can maybe get more value for money on the dyno by adding another variable ... so I just received a TPS kit from [email protected] but I have questions:

1) I understand the basic concept of load based timing (I think), but does anyone have a base map with TPS values I could load as a starting point? The engine has said 41mm FCRs as well as 11:1 pistons, but is otherwise unmodified.

2) I seem to recall that the maximum advance, despite the ignitech unit, is still limited by the flywheel lump. So in my case that would be about 36 degrees or so. Getting the most out of the TPS would mean that I would have to drastically increase this at partial throttle, no? If so, how do I get around that limitation?


3) I'm definitely in over my head here as far as engine tuning goes... but I'm also not planning to outsource this project. First of all, there isn't anyone locally I would trust. Second, this is all meant to be a learning experience for me, that hopefully results in an even better bike instead of melted pistons. I got a well sorted 998 to ride in the mean time, and winter is coming anyways...


attached is some random map for illustration purposes. I probably wouldn't go beyond 32-34* at WOT on mine, it was pinging when it still had the kokusan units.

 

[belter]

i have a flywheel i took out of my single phase 750 that has had the lump extended to about 60 degrees. it's also been machined down a bit. probably still 1.5kg so au$50 postage, but if you want it i'll send it over.

i'm going to 3 phase engines from now on.

 

[belter]

i usually run at least 10 degrees over wot adv at part throttle if i can. the limitations will be if it gets rough usually - you'll feel it.

the ignitech get funny if you try to have break points below idle speed ime. so you're limited to starting the curve above that, unless you can find otherwise. not sure if the latest versions are still like that - i haven't really played with an ignitech for years.

 

[Lelebebbel]

So, the TPS is installed and belters' modified flywheel is in. I still have to verify base timing with a light (pissing rain outside!). Other than that, it's time to figure out a conservative base map, as well as maybe preparing a few more to try out when I can get on a dyno again. This here is what I loaded as a start. I don't know anything about anything though... Would anyone care to comment on the map? Anything stand out as obviously wrong/crazy?


Interestingly the ignitech software generated a 3D map as soon as I clicked on TPS, but it did some weird things I didn't understand (reduced advanced at certain part throttle settings) so I'm not sure how it came up with those numbers

 

[belter]

you need to have two bottom end rpm points to give you a constant advance across the potential idle speed. otherwise, you might get a creeping idle and hanging up when it gets hot. I'd make the advance at 1000 and 1400 6 degrees (or whatever the base is, keep it the same). will give a nice stable idle at 1150 or so.

then ramp it up pretty quick - 20 degrees by 2000, 25 at 2500, etc, as required so no pinging.

from 2500 up i'd start adding a fair bit at part throttle - at least 10 degrees more from 3000 up from 5% to 10, maybe 20% throttle. you need to ride it with a multimeter to find out what throttle opening you have when cruising around. i have seen a difference between output voltage with engine off and engine running, so check that for setting the end points.

you need to drop it off at lower % opening at lower rpm, as the engine load is closer to maximum at lower throttle openings - 50% throttle might give the same output (cylinder filling, pressure, torque) as wot, so you need to be aware that it may ping at that if you are still adding advance at higher part throttle. at 8000 50% throttle will give a noticeable decrease in output compared to wot.

 

[Lelebebbel]

Thanks once again. I've changed the table accordingly.

- Flat area at low RPM to prevent rev hang.

- Steep ramp up between 1500-2500, tapering off towards 4000.

- increased advance below 10-20% throttle above 2500-3000

- less advance between 40-100% throttle at lower RPM, slightly increased towards higher RPM


Couple of things I'm wondering about:

- I see some people have less advance at 0%TPS. I did that as well in my first table above but just removed it. Is that necessary, and why?

- when you say I should test TPS position at cruise, what am I looking for with respect to the table?

I'm guessing I should try to have the higher advance values at part throttle up to and including whichever value I cruise at?
For example if I find I often sit at 3500 and 15% on the highway, I could try to run 40 degrees or something from 0% to there, but then drop it off above 15%, to avoid pinging on acceleration - is that about right?

 

[belter]

advance at 0 and 2% (depending on how stable the tps signal is when running, 2% may influence closed throttle) may make it hang up in rpm with the throttle closed, so you may want to drop the value at 2000. it may also make it rough / chuggy as it comes back to idle on the overrun in first gear sort of thing. you should be able to tune it so in first it will come back to idle nicely and bumble along if you don't pull the clutch in.

you just need to know what % throttle opening you're cruising at, and unless you have a device that can talk to the ignitech and you can see the tps reading it is getting while riding, you'll need to use a multimeter and read the voltage, then correlate that to your tps calibration table.

i'd put as much advance in for cruise without it becoming rough or harsh, and you'll get a feel for what throttle opening is cruise and light accel, etc, if you do the multimeter thing.

 

[Lelebebbel]

I just did a quick test ride with a few pulls to full throttle as well as a reading for cruise throttle (which turned out to be between 10 and 17-20% max).

• no pinging / roughness. However there is a mix of 94 and 100LL in the tank right now so that is hardly a surprise.
• definitely improved pickup and response when accelerating from part throttle
• Engine sounds "sharper" if that makes sense. This one is pretty subjective, but I'm pretty sure it's changed tone a bit and is also louder now.
• Very curious to see if there is a notable improvement in fuel economy, but I can't really test that until spring.
• a few pops and bangs on the overrun but not too bad. Still some rev hang when hot when going back to idle.

So I dropped the 0% curve down to 8deg at 2000 for now and I'm gonna make a few more test runs if the weather allows it. Almost think this could be as far as I can get without a dyno...