Triumphrat

JAXTRIUMPHGUY · 04-24-2008, 03:24 PM

Just got back from the dyno, and thought I'd post the most recent numbers. I've been working on the jetting, and I think I've got it relatively close. Would love to get rid of the dips at 2500, and 5200, but I don't know if that's gonna be easy with the stock carbs., and c.c.'s. My bike is a 2005 790 Bonnie: Air Box Removal with K&N's, 140 mains/42 pilots 2 turns out/Thruxton Needles/Drilled slides by (Bottle Fed). My main interest is the A.F.R. but the numbers are pretty good. (66.74 hp, and 49.72 ft torque.) Probably inflated a bit due to the low pressure, and correction factor.

sweatmachine · 04-24-2008, 04:18 PM

looks like you could go a little bigger on the main, maybe a 142.5 or 145. It looks like a typical run for a very healthy 790.

I hate when they plot the torque/hp on different scales, makes me have to think and trace the lines with my finger on the screen!

mikeinva · 04-24-2008, 05:22 PM

If that air pressure is right you are way to lean( 28.19 air pressure that is way low) Was the dyno room in a vac.room BIG FAN SUCKING AIR OUT?
You are at 14to1 on top, If you run that on a good air day with 30.+ air pressure it will be near 15 to1.In the real world you would have to be in the eye of a storm to get that low of air pressure.I dont know why some of the dyno guys try to get mixture right with air numbers like that.You do have a strong stock motor if you take away that crazy 1.08 factor its still over 60 hp not bad at all.Richen it up alittle and run it in good air it will do even better.

ivar · 04-24-2008, 05:58 PM

which pipes are you using?

rbrian_taylor · 04-24-2008, 08:02 PM

I have 2 long time dyno run questions that have been eating away at me:

1. Aren't the runs done at WOT? If so, how does that possibly correlate to carb jetting/tunning other than the main jet?
2. Is there usually a big fan blowing on the bike/car to keep it cool, simulate road conditions of actual riding/driving?

Every dyno run I have seen (in person and on the internet) have had these two traits in common. Before I get blasted for not having my own results, I have never made a dyno run on my bike or cars, but I have seen many in person.

BTW JAX, great numbers, looks strong for almost stock.

mikeinva · 04-24-2008, 08:50 PM

Quote:

Originally Posted by rbrian_taylor

I have 2 long time dyno run questions that have been eating away at me:

1. Aren't the runs done at WOT? If so, how does that possibly correlate to carb jetting/tunning other than the main jet?
2. Is there usually a big fan blowing on the bike/car to keep it cool, simulate road conditions of actual riding/driving?

Every dyno run I have seen (in person and on the internet) have had these two traits in common. Before I get blasted for not having my own results, I have never made a dyno run on my bike or cars, but I have seen many in person.

BTW JAX, great numbers, looks strong for almost stock.

yes at wot only the main jets can be checked all though a good dyno guy can run it at part throttle and tell you where the rest is at fuel mix. and yes most have a fan on each side of the bike to cool motor

JAXTRIUMPHGUY · 04-24-2008, 11:09 PM

Yep. The dyno is in a low pressurized room, with a huge fan and low humidity. In that room with the low pressure, the a.f.r. was looking good at 3000-4000 rpm's. He held it there for a while for me to see that it was around 13.2 through that range. Then it leans out a little up top, but pulls back up pretty well. I told him that I was thinking of a larger main, and he said that I should leave it alone because it would richen up the mids as well, and I was really close to where I need to be. What do you guys think? Also, normally in Florida it is VERY humid. I'm sure that will come in to play with my tuning as the days get hotter.

Is there anything I can do with my current setup to tweak the big dip off of idle? I put in 42 pilots, and they stopped some of the heavy backfiring. Now just a nice rumble and a few pops on decel. With both the 40's, and 42's it seems to bog rich, then catch and pull hard when I punch it from idle in 1st gear. Thanks for the replies.

sweatmachine · 04-24-2008, 11:13 PM

you're rich if it bogs like you say, so go in 1/8 or 1/4 turn on the idle mix screws.

Try the bigger main, see if it still runs good (and it will probably run better), if not you can always go back.

JAXTRIUMPHGUY · 04-24-2008, 11:24 PM

Quote:

Originally Posted by ivar

which pipes are you using?

Emgo pipes.

SPARKSS · 04-25-2008, 01:09 AM

Quote:

Originally Posted by JAXTRIUMPHGUY

Just got back from the dyno, and thought I'd post the most recent numbers. I've been working on the jetting, and I think I've got it relatively close. Would love to get rid of the dips at 2500, and 5200, but I don't know if that's gonna be easy with the stock carbs., and c.c.'s. My bike is a 2005 790 Bonnie: Air Box Removal with K&N's, 140 mains/42 pilots 2 turns out/Thruxton Needles/Drilled slides by (Bottle Fed). My main interest is the A.F.R. but the numbers are pretty good. (66.74 hp, and 49.72 ft torque.) Probably inflated a bit due to the low pressure, and correction factor.

Great looking run....stout torque rise - bet its a great bike to drive. It's possible that the dip around 5200 might be a function of exhaust pipe tuning that might be hard to change there - doubt it's noticeable when underway. How'd they arrive at a single graph for A/F? Was this measured from one pipe only or an average of both?