17 replies to this topic

[MCBodge]

I've noticed that the TDM throttle opening/twist-grip rotation is very non-linear at wider openings.

There appears to be a noticeable 'step/surge' of torque (in a good way) that starts when the throttle is only a couple of degrees before Wide Open.

Is this normal on the TDM850 or do the carbs need tweaking to smooth this out?
The one thing I didn't check having replaced the emulsion tubes last weekend was the float levels due to a lack of time.

The throttle response is sharp off idle, there are no obvious hiccups or flat-spots and the engine pulls to high rpm.


When I'm not on the bike, I drive turbo diesel car, so am accustomed to a very different, fairly blunt, throttle response.

Edited by MCBodge, 09 April 2009 - 09:03 am.

[MCBodge]

TPS appears to be working correctly, so maybe it is normal.

[TDMTAM]

TPS appears to be working correctly, so maybe it is normal.

Could be a jetting issue but if its not bothering you I'd not bother chasing it, it would need dyno time.
TAM

[MCBodge]

Could be a jetting issue but if its not bothering you I'd not bother chasing it, it would need dyno time.
TAM

I realise that a dyno session would be required for an optimal set-up, I was just wondering what was a likely cause of such a marked difference in urge over a small range of movement at a wide throttle opening and whether float level might contribute.

If I did decide to go down the dyno route, I'd like to get the bike working fairly well with a bit of DIY before taking it to a dyno for final tweaking.

[MCBodge]

there is a distinct lag compared to modern FI bikes when opening the throttle, although the higher the rev's the less noticable it is

Probably the best way to describe it is

open throttle to 95% open and get 75% of maximum pull
open throttle to 100% open and get 100% of maximum pull

It may just happen to coincide with the alleged dip at mid rpm and hitting the "powerband", but I've noticed a few times.

The power delivery/torque curve feels fairly constant, but it does keep going with urge to the red line.

[TDMTAM]

Try http://www.factorypro.com/
look ing tech support there are some good guidlines there.
TAM

[MCBodge]

Try http://www.factorypro.com/
look ing tech support there are some good guidlines there.
TAM

Thanks. Some useful info on there.

As a matter of interest, does anybody have a torque plot from a factory standard Mk2 TDM850?


-Yes, this is cheapskate dyno tuning

I'm just interested in seeing what the standard is as a reference point.

Edited by MCBodge, 07 April 2009 - 04:22 pm.

[wicklamulla]

Thanks. Some useful info on there.

As a matter of interest, does anybody have a torque plot from a factory standard Mk2 TDM850?


-Yes, this is cheapskate dyno tuning

I'm just interested in seeing what the standard is as a reference point.

ya i have one in my photobucket link below, but my boike runs a K&N filter (wow) and carbon cans. search the pics and you will find the dynochart.

[MCBodge]

search the pics and you will find the dynochart.

Cheers wicklamulla!




That's a significant dip at 4-4.5K. It's consistent with the shape of the other plot too.
Is that 'dip' engineered-in by the factory to get around some regulations??

Are they before and after plots or different bikes?

It looks as if it's best to keep above the 'black hole' at 4k and there's nothing to be gained from going above 7.5K
-although my bike seems happy enough going to the red line and gets there fairly quickly.

Edited by MCBodge, 07 April 2009 - 08:20 pm.

[robelst]

My Guzzi and Buell have those leaned down dips as standard in the "lower-midrange", just to get around the noise and emission regulations (result of lovely but ancient engine designs ). TDM engines are a lot more modern but maybe they have this effect as well? Unlike my Buell (when it was still standard ) I never really noticed it on my TDM. Then again, I have a '01 model which have differences in the carbs compared to models up to '99 or '00 (so I am told). Apart from the odd carb-icing I have to say the throttle response is always spot on (unlike some FI bikes I have owned as well). I bet a modern diesel will always be more lineair though, and so will triples and fours be, but a properly engaging bike shouldn't be too lineair.

[MCBodge]

My Guzzi and Buell have those leaned down dips as standard in the "lower-midrange", just to get around the noise and emission regulations

As I suspected.
From looking at the Factory Pro site, raising the needle appears to be the method for richening the mixture at thse sort of rpm.

[wicklamulla]

MCBodge, the top pic is of my dyno run (i'm still out of breath) and the borrom one is of Emmett's 1998 MKII but it has TDM 900 barrells and pistons fitted hence the extra bhp, the midrange on his bike felt quite impressive to me when i rode it.

[MCBodge]

TDM 900 barrells and pistons fitted hence the extra bhp

Ah, interesting stuff.

Was the dyno plot scan rate done different for that bike? The line is much smoother.

[wicklamulla]

Ah, interesting stuff.

Was the dyno plot scan rate done different for that bike? The line is much smoother.

don't u dare speak to me loike that ya fecker sorry man i dunno what ya mean but
both bikes were done within minutes of each udder on the same day obviously.

[MCBodge]

don't u dare speak to me loike that ya fecker sorry man i dunno what ya mean but
both bikes were done within minutes of each udder on the same day obviously.

no offence intended, old bean, what, what.

I can sense a dyno session coming on....

[dandywarhol]

Even with a Power Commander fitted there's still a dip around max noise test area. The revs for taking the reading is based on the engine stroke.

[MCBodge]

Having experimented this morning, my bike does pull disproportionately harder at "Wide Open Throttle" than it does at "almost-Wide-Open" -Maybe that's just a function of the CV vacuum slide opening for given 'vacuum'/throttle position and isn't really a problem.

There's a slight snatchiness between coasting and power-on. It revs smoothly and the revs return to idle without under-shoot, albeit maybe slightly slowly.. The pilots are set to the standard 2 turns out and I suspect this could be improved on.
-I'm going to try reaching the screws without having to dismantle the bike.

Even with a Power Commander fitted there's still a dip around max noise test area.

So, it's possibly just a feature of the engine's mechanical dimensions. Harmonics, waves etc.

There are two DynoJet places in Stockport. Does anybody have any experience of either of them or any other decent places in the N Cheshire/Manchester/South Lancs area?

Edited by MCBodge, 09 April 2009 - 08:10 am.