Advance

[Angry Joe]

I too worry about this with our Yamaha R6. The stock advance for our motor maxes at 55 degrees, high enough that we have to fool our crappy Haltech by adjusting the crank sensor calibration. We've been running into backfire problems above 10,000 rpm that might be caused by being too retarded, but considering our engine currently bothers people studying more than a mile away, we're not likely to hear knocking...

Lehigh Formula SAE

www.lehigh.edu/~insae/formula (http://www.lehigh.edu/~insae/formula)

[Angry Joe]

I too worry about this with our Yamaha R6. The stock advance for our motor maxes at 55 degrees, high enough that we have to fool our crappy Haltech by adjusting the crank sensor calibration. We've been running into backfire problems above 10,000 rpm that might be caused by being too retarded, but considering our engine currently bothers people studying more than a mile away, we're not likely to hear knocking...

Lehigh Formula SAE

www.lehigh.edu/~insae/formula (http://www.lehigh.edu/~insae/formula)

[Angry Joe]

Oops! I meant to respond to this post (http://fsae.com/eve/forums?a=tpc&s=763607348&f=125607348&m=7366069072)

Lehigh Formula SAE

www.lehigh.edu/~insae/formula (http://www.lehigh.edu/~insae/formula)

[Kevin Hall]

Joe

Check your private topics

kevin

Kevin Hall
University of Saskatchewan
Engine Guy in Need of Help

[B Lewis @ PE Engine Management]

Angry Joe,

I doubt that the backfiring is due to being retarded at high speed. Usually you just won't make the max amount of power without enough advance (unless you are way off). Are you "popping" in the exhaust? If so this can be caused by having just a couple of small exhaust leaks.

Glad to hear you got that thing finally running!


Brian Lewis
www.pe-ltd.com (http://www.pe-ltd.com)
"Complete Engine Management Systems"

[Angry Joe]

Actually, there is no doubt we have exhaust leaks! Due to what we have at our desposal, we're lucky we have enough of an exhaust to keep us alive in the lab. Could leaks cause this kind of problem? I acknowledge that it could be ignition related since we'd get backfires if it cut out. However, we've discovered the problem worsens as the engine heats up under load. There are definitely backfires since our aformentioned exhaust leak lets us see few of them...

Lehigh Formula SAE

www.lehigh.edu/~insae/formula (http://www.lehigh.edu/~insae/formula)

[B Lewis @ PE Engine Management]

Angry Joe,

Exhaust leaks will cause a "rumbling" kind of backfire in the exhaust, especially when the engine is under a load. The sounds are caused by unburnt fuel re-igniting with fresh air in the exhaust system. Generally, the hotter the engine and exhaust, the more prevelant the sounds are.

Try a little experiment to verify. Run the engine under a medium load and get the backfiring to occur. Then, change the fueling. Adding and subtracting fuel should change the frequency/tone of the backfires without changing the ignition timing. BE CAREFUL!!!! Don't go too lean while doing this. You don't want to starve the engine of fuel while under load.

Brian Lewis
Performance Electronics, Ltd.
www.pe-ltd.com (http://www.pe-ltd.com)
"Complete Engine Management Systems"

[Angry Joe]

I will as soon as we stop blowing the exhaust off the dyno. In the mean time, to clarify, the backfiring we hear increases in frequency to the point that it acts like a rev limiter. When we start the engine under no load, we hit 15k no problem. After we put it under load we start hitting pops at around 10k and can't get past 13k. It seems to worsen the longer we run - possibly heat related? If we take the engine off load, we STILL hit the same rev limit! Since playing with fuel and advance doesn't seem to help, I am thinking the problem is ignition related. But I am once again running out of ideas. What I know:

-Coils and ignition are capable of getting to 15k
-Crank sensor is properly installed and is not loosing signal as far as I can tell
-Engine itself is adequetely cooled (no airflow around it, however)
-Rev limiter is set to 15k, secondary rev limiter is disabled

We just got a huge ass fan to try and cool the intake/electrics, now go figure our exhaust is deciding to go flying off when we try and and run. Sometimes I really, really hate the equipment we have to work with.

Any ideas are welcome. I don't feel too good about constantly hitting this rev limit and possibly hurting the engine, but I'm not sure what else to try...

Lehigh Formula SAE

www.lehigh.edu/~insae/formula (http://www.lehigh.edu/~insae/formula)

[Charlie]

Is your crank sensor wired backwards?

-Charlie Ping
Auburn University FSAE 1999-present

[George C. @ Motec]

I was perusing the 'neighborhood' and this subject caught my attention.

Using an ocilliscope on the '12v' switch line to the coil(s) and an inductive amp probe will reveal if the coil(s) are being charged properly, (dwell) or to much/not enough.

If this comes out as ok, then your problem is the secondary output is insufficent for the bmep at these revs.

Try this, shorten the plug gap to .020" or less if possible, and run at it again. If it is what I think it is, she will zoom right up to "infinity and beyond".

good luck.

[Angry Joe]

Last night we tried a solution Brian gave me on the phone, apparently the crank position sensor is affected by the oil heating up and moving it closer to the magnets alleviates the problem. We had the headers glowing last night and I did not encounter any backfiring at high rpm. In fact, we logged about 3 hours of dyno time without breaking anything! That might be a new record for us.

Lehigh Formula SAE

www.lehigh.edu/~insae/formula (http://www.lehigh.edu/~insae/formula)

[B Lewis @ PE Engine Management]

Joe,

THAT'S GREAT. I'm glad that I could help. Maybe now you won't be so "Angry"

Brian Lewis
Performance Electronics, Ltd.
www.pe-ltd.com (http://www.pe-ltd.com)
"Complete Engine Management Systems"

[Angry Joe]

Your solution worked great, but let's not get carried away here http://fsae.com/groupee_common/emoticons/icon_wink.gif

Lehigh Formula SAE

www.lehigh.edu/~insae/formula (http://www.lehigh.edu/~insae/formula)

[MoTeC]

Just a question, is the crank sensor the stock one? I have seen problems arise with heat soak on sensors that are not designed to be in a hot oily environment. I usually recomend keeping what ever was on the engine to start with.

But as George said, a quick check is to close the plug gap and see if you can get a few more revs from that, it will usually point to an ignition problem rather than an ECU thing.

Mark.

Donna

[Angry Joe]

The sensor was supplied with the Haltech, a Hall Effect sensor.

Lehigh Formula SAE

www.lehigh.edu/~insae/formula (http://www.lehigh.edu/~insae/formula)