Tigers scared of heights?

[ChazzyB]

Well, my Tiger is, as I discovered on a trip last week down to the French Alps. To cut a long story short, once the bike's higher than 500m, the power loss starts then misfiring under load gets worse and worse. I managed to get to 2000m in one pass with the bike very seriously sick. Actually, it wasn't much worse at 2000m than it was at 850m, the height our hotel was at. As soon as the bike's down to 500m again, all's fine again - loadsa power, just the same as my mate's Tiger, which didn't hiccup.

My guess is ECU barometric pressure sensor foo-baahed, or is there something else it might be? Trouble is, any fix is difficult to test in the south-eastern UK...

[jwray76]

Sounds like your tune is messed up or your air filter is dirty. As you go up the air is getting less.

[NKL]

sounds like the ECU isn't picking up the atmospheric pressure.
As you go higher the air gets thinner so unless the ECU adjusts it runs richer. It could be a choked air filter that the ECU can't overcome, or is the link pipe from the airbox to the ECU kinked or squashed.

[ChazzyB]

The air filter is clean (K&N) and the link pipe from the airbox was OK when I fitted the ECU some weeks ago. The barometric pressure TuneECU reports is within or two units (994hPa vs 996hPa) of its predecessor (which I plugged up again to check), which didn't have any problems the previous two years I'd been up high in France. I suppose I should check the link pipe isn't blocked internally (I used the pipe which came with the replacement ECU). I presume the actual air pressure is sourced elsewhere by the ECU, as the link pipe is going to be sniffing at the depression in front of the throttle bodies

I reloaded the TOR tune this afternoon (I'd never done one before) and went for a ride. The thing that was evident is that gentle throttle transmissions below 3K RPM have been really improved! It used to stutter just at the point between slightly-closed throttle and even. Apart from the fuelling and ignition maps, what else does loading a tune do?

I'm going to have real problems checking any improvement on the altitude problem. It's a good 200 miles to the nearest place that's  approaching 500m above sea level from where I live.

[Bixxer Bob]

Chazzy,  the ECU sensor does sense the pressure in the airbox via that tube, it doesn't sense anywhere else.

If your local pressure is 996 and drops to something like 990 with the engine running, then at 500m the reading would drop to for instance 810 and 800.  The point is it doesn't matter what the relationship is between the airbox pressure and the atmospheric.  The ECU calculates how much oxygen is available at the pressure it reads in the airbox.  Even if the filter is clogged, it'll still compensate to make sure the air / fuel mix is right.  What will be noticeable is less power because there's less fuel and less oxygen for a given throttle position.  

Your poor running, assuming the baro sensor is working and the pipe is clear, must be elsewhere - valve clearances perhaps?  To check the baro, hook up TuneECU and read the pressure, then gently suck on the tube.  the value should drop.  Don't blow though, you might damage the sensor.  You could also try it with the engine running and see what the effect is.

[ChazzyB]

Your poor running, assuming the baro sensor is working and the pipe is clear, must be elsewhere - valve clearances perhaps?  To check the baro, hook up TuneECU and read the pressure, then gently suck on the tube.  the value should drop.  Don't blow though, you might damage the sensor.  You could also try it with the engine running and see what the effect is.

Thanks for that. I'll suck but won't blow... I hope it's not the valves - they were all within spec at last check at 42K, mileage now being 48K.

The altitude was like a switch. The bike was absolutely fine at 500m, but very soon after that (520-540m perhaps), I'd get a bit of hestitation around 4-5K trying to accelarate and then shortly, misfiring. Good job the Col d'Iseran was still closed when we headed for it last Wednesday. ;-)

[Bixxer Bob]

If the valves were ok at 42 they'll still be ok.

When you're in there, check that the white elbow is a good fit in the tube to the ECU, the tube is a good fit on the ECU, the tube has no leaks, and the grommet on the elbow where it goes into the airbox iss a good fit.  You might think it doesn't matter, but it does.

[Chris Canning]

I haven't been over the Grand St Bernard on my 955 but on my 885i it refused to start when at the top and had to be bumped.

[ChazzyB]

I haven't been over the Grand St Bernard on my 955 but on my 885i it refused to start when at the top and had to be bumped.

Two years ago I did the Grand St Bernard just a day or two after it had finally opened, first week in June. I stopped at the col to put more clothes on, didn't have any problems restarting. I've got a different ECU now, though...

[Bixxer Bob]

I seem to remember you had ECU probs once before?

Just out of interest, this one's not got water ingress evidence on the underneath, has it?

[ChazzyB]

Just out of interest, this one's not got water ingress evidence on the underneath, has it?

It certainly has some corrosion in the usual place, but I guess that any Tiger that's been used in the wet and hasn't been sealed by the owner is going to. I didn't realise myself this was a weak point until I suffered a problem.

[Cosmo61]

Hello!
I'm new is this group.
I have a tiger from 02 and on a holiday in Åre, Sweden.
I read the first post in this topic, and have similar problem
with my Triumph Tiger 955i.

[iansoady]

Good job the Col d'Iseran was still closed when we headed for it last Wednesday. ;-)

You'll just have to go back again. Been over it a couple of times on the Commando and it's fabulous - quite eerie as all the vegetation disappears near the top.

[Cosmo61]

I found this topic on the alltitude problem.
yamaha FJR seems to have some problem with this.

I had a problem with a brand spankin' new Sprint ST where it would die going over about 3000 ft in altitude. The ECU had to be replaced because the barometric pressure sensor failed and was in the ECU.  I don't know where or even if an FJR compensates for altitude but that would be the first thing I would check.

[ChazzyB]

I've got a trip to a rally in County Durham; the north of England planned for late July. There's a few roads in the Pennines just over 600m I've identified. I've ordered a multifunction barometer/altimiter/compass/thermometer/clock from eBay, which I'll stick to the dashboard. ;-)