Triumphrat

robnobrakes · 08-30-2007

Mods so far:
904 Wiseco big bore
Head skimmed, gas flowed and ported (10.7 to 1)
39mm FCR Keihin Flatslide carbs with 150 main jets (up from 140 with the 865 capacity as the motor was running too lean up to 6000rpm)
Quick action throttle
Predator Exhausts
Lightened flywheel
Ikon rear suspension
Hyde steering damper
Uprated clutch springs
19/41 sprockets.

Heres the thing: The new dyno Bob Farnham Tuning has recently installed is reading 5% lower than his old dyno, which my Thruxton has always been tested on in the past. We know this dyno reads less because my chums Speed Triple has been dyno'd on both machines.

Rear wheel power on new dyno: 80bhp
Rear wheel torque on new dyno: 63.8ft/lbs
+5% as a comparison with the old dyno is 84bhp and 67ft/lbs

The results of the earlier dyno runs before the big bore kit was fitted were:

74.5bhp, 62ft/lbs torque

So, we have achieved about a 10bhp power and 5ft/lbs torque improvement over the 865 motor. I know there is room for error with these figures, but there is no other way to finding the performance gains. I can't post the graphs at the moment as the printer has not yet been coupled up to the dyno.

As to which dyno is more accurate who knows, and who cares. Its the before and after improvements that matters. The Thruxton started out with about 53bhp at the rear wheel in stock trim on the original dyno. Now its around 84bhp. Thats a 63% increase in power.

sweatmachine · 08-30-2007

I think his old dyno was reading a bit more than 5% high, and probably the new one too...

but like you said, improvements have been made.

robnobrakes · 08-30-2007

Quote:

Originally Posted by sweatmachine

I think his old dyno was reading a bit more than 5% high, and probably the new one too...

but like you said, improvements have been made.

Who knows how accurate dyno's are. It's possible that the earlier dyno more accurately reflected the real world rear wheel power at 53bhp, given Triumph's claim of 69bhp at the crank. 53bhp reflects a 30% loss to the rear wheel, which is rather high IMO, suggesting there may not be as much as 69bhp at the crank for the stock bike. The new dyno would have indicated around 50 rear wheel bhp. However we can talk maximum figures for ever and not know the truth.

Whatever the 'real' bhp figure is, there has been a 63% overall improvement in the rear wheel power. Most importantly, the bike goes like a scalded cat, and my chum on his 955i Speed Triple has to thrash his bike to keep up with my thrashed Thruxton.

The next 'improvement' on the list is the polished alloy Slippery Sam tank I have ordered from
http://www.tabaker.co.uk/

SuperMan · 08-30-2007

Quote:

I think his old dyno was reading a bit more than 5% high, and probably the new one too...

Most likely so, yes.

jojje1963 · 08-30-2007

Maybe they didn't used the same correction factor? Anyway, 80hp sounds true. I have 75hp on my 904cc with stock carbs and mufflers (opened up a bit though)

sweatmachine · 08-30-2007

hey J, do you think with my bigger valves I have enough room to skim the head to raise compression a bit, or do you think it would be worth it?

jojje1963 · 08-30-2007

Sweat,
I would check clearance first, at least 1mm if you ask me. You won't gain much so that part is up to you, I only did it cos I can

sweatmachine · 08-30-2007

you're right, I just need to put a 3mm spacer under the base gasket right?

and a little compressor up front?

(one day....)

mikeinva · 08-30-2007

yea and 50rwhp is about right for stock

mikeinva · 08-30-2007

I wish the dyno guys would give everyone the raw numbers with out the correction factor the raw numbers are what you got where and when you test it and thats what shows on the track.I look at it this way if weather changes so dose the tune swo what good are correction factors in the real world anyway.ever have a motor pick up as much hp when its cold weather as much as the factor says it should i havent.I froze my butt of one winter trying to lol