R1100GS 86 bhp dyno run

[Pykie]

Hi all,

I had my r1100gs dyno'd yesterday, and was very pleasantly suprised when it gave 86 brake and 105 Nm of torque, with 76 bhp/94 Nm at the wheel.

I understand BMW quote 80 bhp/97Nm, and I was expecting a real world-ish mid-high 70bhp reading (at the crank).


The spec. of the bike is:

- 1998 R1100Gs, grey import from Germany. 40,000 miles.
- Remus Revolution exaust, with standard baffle in it.
- Cat code plug removed, CO potentiometer retrofitted.
- zero=zero set up on throttle position sensor, set at .370 Mv.
- Recent minor service.Injectors recently cleaned.
- NGK Iridium plugs.
- 6000 mile old slightly grotty standard filter.
(I usually get about 40mpg, which isn't great but I dont have a particulary economical riding style, and my ride to work is very hilly)


As for why I got a good result, I think that:

- The Remus exaust made a big difference.

- Retrofitting the CO pot. may have helped to richen it up a little to suit the exaust.

- The Zero=zero setup probably didn't make any difference.
(I shouldn't have disturbed the throttle stops at all really. I had a miss-fire at the time and was clutching at straws. I since read here that Mr Steptoe reckons it is a completely unneccessary procedure and I believe him. At least I didn't f**k my bike up by doing it.)

- Servicing it and cleaning the injectors certainly didn't do any harm.

- The Iridium plugs might make a small difference, though not ever enough to notice on the road.
(while I was messing about with my miss-fire I did find that my sick bike ran better on the Iridium plugs than on normal Bosch or NGK items. Whether this makes a difference on a healthy bike I don't know. It'd be interesting to do a dyno run with standard, and then Iridum, plugs to see if there is any difference).

- The grotty air filter may have lost me 1 or 2 horses, though again I doubt if I'd notice on the road.
(on the subject of filters, an engineer where I work did air filter testing of some sort at his previous employers, and maintains that K&N filters stop so few fine particles that you might as well put a bit of mesh over the air intake to catch stones. As BMW designed the bike so the standard filters are used for 12,000 miles I imagine the standard filter when new flows as much as the airbox will allow, so to keep good power and good filtration there is probably more to be gained by changing standard filters every 3-6000 miles than fitting a K&N. Any thoughts on this?).

As a thought, has anyone ever tried to improve airflow by modifying the intake trumpet? I did wonder if a second one could be fitted, running down the RH side of the bike. I don't know enough about airbox design to know if any gain would be made.

Anyway, I am posting this long-winded and nerdy ramble to invite comment, as I would be interested to hear any views on this and any critisism of my ideas on this subject.

Ride safe.

Pykie.

 

[rudiemoto]

86bhp
u must have ran it on

 

[Greg Masters]

Hi all,

I had my r1100gs dyno'd yesterday, and was very pleasantly suprised when it gave 86 brake and 105 Nm of torque, with 76 bhp/94 Nm at the wheel.

I understand BMW quote 80 bhp/97Nm, and I was expecting a real world-ish mid-high 70bhp reading (at the crank).


Pykie.

I'm sure that you're pretty pleased with that and, if the bike is running well, good for you. But by and large, dyno figures are pretty useless except as a comparison against other figures taken on the same dyno at pretty much the same time. If you were to not use your bike until some cold and damp day and then take it back to the same dyno, you'd get an entirely different set of figures. I really don't know how anyone knows that 76 brake at the wheel equates to 86 brake at the crank.

What 'domestic' dynos are good for is seeing the effects of changes that you make to the engine set up whilst the engine is under load (and for fault diagnosis if the engine is not running cleanly).

In the good old days (when I was an apprentice), we'd run an engine on a bed under load. The engine would be screaming away and the exhausts red hot and some fecker would stick their hand in and swing the distributor (to change the ignition timing) until power was maxed. Not a job for the nervous!



Greg

 

[Vern]

The best thing about dyno's,is when something lets go big time

Dyno's are only any use to engine builders and modifiers,not to mention pub car parks

 

[D6]

as greg says , ignore the top power readings and look sat the curves on the graph, smoothness is all important,
some dyno,s are "tweaked", after all, people are more likely to go to a tuning shop that can get more horses on the dyno

 

[Wrigsby1]

I had one of my previous 11GS's tuned a little. I had come from sports bikes so didn't know any better

I did the K&N bit and got hold of a Remus Viper with a collector. It was pretty tight when I bought it and this made it rev though the 2nd half or the range more easily. I went to Superchip and they fitted a modded chip with before and after dyno work. They tried a couple of different chip settings and I also had a chance to try it "real world" on the road.

The modded chips just play with ignition advance and richness as I remember?

The dyno showed a reasonable increase with the Remus over standard and a small increase again over that with the chip. It was noticiable on the road and wasn't total waffle. The Superchip chaps said if i wasn't happy there was a difference I could leave it and pay nowt.

All this is mainly unecessary and will be roundly panned by the usual but it was interesting to see what was possible. The gains are mainly post 4.5 k revs and the middle torque dip seems the hardest thing to fill.

I have also tried a 2nd hand Laser pipe and chip kit on my latest bike but it was too loud and too flat for me so was sold on.

The bike obviously freed up in the 40 k miles I had it. What is most noticable with the 11/1150's is the difference in how they ride back to back.

The 2 best "other" 11's i rode were a 80k standard GS and a 10k RT. The present 11GS is fine enough but is "average" in relation to all the others i have ridden. If you have a good one guy's, don't sell it

PS I didn't believe the dyno numbers but just looked at the graph curves)

 

[Pykie]

Hi,

thanks for the comments. I do apprieciate that Dyno results can be pretty subjective, and that the crank output is a definate estimate. Looking around a bit suggests that transmission losses could be anything from 10-15%, which is quite vague, though the dyno must have estimated a loss of 12% (ish) in this case to establish the crank output.

I can see that comparing the curves is far more valid than peak output, especially on a bike like a GS, but I don't have a baseline curve for my bike, and I can't find any graphs for any other GS's.

I actually visited the dyno because I wanted to check that the bike was running ok, what with with a non-standard exaust and TPS settings that had been meddled with by some idiot with a cheap multimeter (me). I also wanted to try the process out because I have another bike (an old kawasaki) that I am playing with and will need to set up. And it was a sunny day and I felt like a ride out.

So, I think the trip was a success, the bike is running well, though the true peak output is obviously subjective. I would like to compare the curves with other GS's but don't have the info. I will attempt to post a graph tomorrow for comment, if anyone is still listening.

Goodnight all,

Pykie

 

[Vern]

If you're a happy bunny,then it's money well spent

Did it have a run before you done anything to it at all?

 

[Wrigsby1]

My work did make a difference and made the bike more driveable though the range. Superchip did have standard graphs and mine with both the stages of mods. It was good to see the diffence on the graphs and match it up to how it felt.

When I worked for a dealer I got to have one of the demo's as a company bike which were often 1150's (until the mileage went too high!!). When i went to sell my 1100 i had a last ride to check it out and nearly didn't sell it!

 

[Jon P]

When the GS11 first came out in '94 a couple of the first magazine tests showed that they were making 80+.......and I for one, having owned a 94 and a 99 always felt that the ealrier bike had more punch.