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Post Info TOPIC: Limiter issue hitting affecting the run...


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Limiter issue hitting affecting the run...


During the past few days I have been puzzled because of the engine getting lean towards end of the each gear... this is something that I did not notice when dynoing the bike.

The starting point is:
- The ecu is extended to 11500rpm, fuel maps tuned with ecu.
- On each gear engine gets lean at around 11200, from speed sensor I can confirm that it happens at exactly same spot every gear. The exact RPM is a bit uncertain as innovate DL32 smoothens the RPM curve quite a bit
- The only limiter that is set at around 11200 is neutral
- Gear position sensor works, tested with multimeter from ecu harness connector. It do shows neutral in between gears when changing gears. I do preload the gear lever which may mean that gps detects neutral, anyhow have not been able to reproduce this on the road
- According to the rpm gauge I shift just before 12000rpm (11500 real).
- The engine does not cut completely, I can hardly notice that I hit a limiter. It just looses power according to the datalog
- This happens at partial throttle too so its not injector duty cycle issue
- I do clutchless switching so its not a clutch level that is pressed. We can also see from speed curve that clutch is holding.
- I did have a problem to start the engine, the side stand switch needed to be depressed once by hand.
- The EGT probe is connected to cylinder 4 and that does only indicate a slight temperature raise
- The oxy sensor is connected to collector and detects all cylinders
- Have checked the .bin on workbench, no odd limiters before 11500


There is certainly a limiter issue somewhere - just can not understand which one... I may be overrunning the bike to soft limiter. Anyhow I recall that the ignition soft limiter affects outer cylinders which is not in line with the logged data. On the other hand under certain conditions I do recall an ignition cut of the inner cylinders, just can not recall under which condition.

I still have at least four scenarios:
- Somehow the clutch limiter becomes engaged when preloading the gear lever on strip ?
- I just hit the normal rev limiter and the innovate is so much off (unlikely as I do see the busa stock rpm gauge at 12000rpm when shifting)
- Unknown limiter hitting the bike which we did not detect during the dynoing the bike.
- In dyno the conditions were different - so something is cutting the fuel pulse


limiters_in_use.jpg


hitting_a_limiter_but_what.JPG



-- Edited by PetriK at 10:06, 2008-06-10

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As this can be seen to happen on gears 1-3 searched through various tables.

Its of course possible that we have made a mistake when tuning the bike and not detecting this on dyno assuming just hitting the limiter...

The tables to be checked are:
0x28A20
0x32BA0

tables_to_check.JPG

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This is what outer and inner cylinders ignition output looks at any RPM on my "opened" usa ECU. RPM is same for both measurements and difference is alike all through the RPM range. I dont understand this... anyhow the signal directly at the driver transistors is good.

igndiff.jpg

-- Edited by PetriK at 14:36, 2008-06-10

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Don may have been right - voice of experience... possibly overrunnig injectors or simply having a block in the replacement air hose.

I looked at the Dyno AFR (red line, blue is stock busa K8), and there is nothing alarming there. Anyhow the cluch was slipping quite heavily when tuning the bike so that may have affected something.

AFR220.jpg

... but then I decided to compare pulsewidth from the injectors. First of all, when changing the TPS position from 70% to 100% the pulsewidht does not increase much - but with RPM increase the pulsewidth change becomes significant. Then as my B maps are still stock maps I decided to check the injector pulsewidth stock vs . 1397 and noticed this:
injduty_stock_vs_1397.JPG

Still need to verify the info, e.g. the ambient pressure for this comparison was artificial (set by resistor) etc... but I may be very close to the limits.

Just wondering why does this not show in the dyno. Innovate shows this clearly (the purple line peaking up...):

hitting_a_limiter_but_what.jpg

-- Edited by PetriK at 16:08, 2008-06-10

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Don


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PetriK,
Wow, looking at your injector pulse width comparisons, you are in serious "no-mans-land" with your modified engine. By quick calculation, your duty cycle is about 95%!

80% duty cycle is the safe standard number most tuners shoot for. That standard has come from the past when injectors were slow to fully open (~1.8ms), but the injectors we have on these motorcycle engines (and the newer automotive injectors) are far more responsive and much quicker to fully open (~1ms), so we can push things a bit more.

I would still shoot for 80%, even though the stock bike looks like it's about 83% duty cycle, especially if you are raising the fuel pressure. Raising the fuel pressure increases the opening time of the injector, decreasing the maximum acceptable duty cycle.

Raising the rev limit has a serious impact on injector duty cycle. The total open time remains about the same, but total cycle time decreases a bunch! I see this with the newer 600cc engines. The injectors that come stock in the 600cc engines often have higher flow rates than that of the very large engines. At 16000 RPM (2006 Yamaha R6) the total time is 7.5ms, which gives you 6ms to deliver your entire fuel load @ 80% duty cycle.

It looks like it might be time for a fuel injector upgrade. Do you know the flow rate and fuel pressure of your current injector? I might be able to help you with some replacement injectors.

Keep us posted.


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Don


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Depending on how quickly the dyno run is completed, you may not even see this on the dyno. I have noticed that the O2 reading taken from the exhaust are slightly delayed compared to the rest of the acquired data (distance the sensor is mounted from the exhaust valve and the response time of the sensor). The run might be over before the sensor ever "sees" the lean out. I'm guessing that the run at the drag strip may have a slower acceleration rate than on the dyno. It's something to look at anyway smile.gif

If the problem is related to injector duty cycle, you may be seeing the problem from the weekest injector first, meaning that all of the injectors won't give up at the same duty cycle.

It's late and my mind was wondering, so I figured that I would throw that out there.

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Thanks Don,

Appreciate your views. The injectors are stock 240cc(80% I guess, real word flow is about 296). Pressure should be 42. I will pump up the pressure asap to around 60psi - that should help a bit...

I am still very puzzled because of the dyno chart. The oxygen sensor was in the pipe and there is usually appr 300rpm delay on that. Additionally there was about 500rpm clutch split. At 11500 (real 11000) you see the AFR to drop significantly. That was not a mapping issue really. I tried to fix it several times without success and finally gave up as the clutch did not hold anymore.

What is that spcial condition that causes the dyno AFR to read rich ? Engine accelerating very rapidly due to the clutch slippage during few last hundreds of rpm ? Still should see the AFR going up, not down...

This makes me think that I still have not figured everything - yet. Any toughts on the topic appreciated.




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I think I have found out the reason why leaning out was not visible in the dyno...

As we know the ramair compensation increases fuel delivery on std engine around 3% before hitting top speed limiter.

For dynoing a bike in Ecueditor there is a feature that you use to set a fixed ram air map. In that case the amount of additional fuel is fixed to a constant which was set to 21 (now32). The thinking behind is that as the airflow from fans in dyno is fixed also the additional gear based fuel should be fixed. Otherwise you run too lean with smaller gears if you tune with fifth gear.

So now when the RAM AIR compensation is on for the track and in real life also the speeds are increasing to push air into the airbox the bike needs more fuel which the injectors are not capable of delivering. Below an image of the normal ram air maps, additionally the high load ram air maps are modified accordingly.

std_ramair.jpg

In my case I dialled in the AFR in Dyno with ramair being disabled (i.e. fixed to 21) on the 5th gear. This yielded reasonably straight AFRs between 12-13 regardless of gear, but still making the 3rd and 4th leaner than 1st. But more datalogging will show us the trend in more detail.

disabled_5th_ramair.jpg

I have also set the RAM AIR disable constant now to 32 so that the AFR curve will be on the leaner side. Now its too rich. I dialled for 13.2 and got around 12.5-12.8.

Additionally as Don pointed out the gas takes some time to travel from engine to sensor so its always delayed by few hundred RPM's.

Now only one unexplained is that why did the AFR indicate going so strongly downwards in dyno. I recall having difficulties in tuning that and have come to thinking that maybe that is the point when injectors are locked fully open. This is just a guess, would like to get views on this ???

AFR220_injectors_fully_open.jpg

All above assuming that the thinking process has been correct so far...



-- Edited by PetriK at 08:30, 2008-06-11

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