60mm Open Exhaust Systems
 

Is anyone running a 60mm straight exhaust system on anything?

I am looking at building a 748r with an 853 kit on it. I love the revvy nature & weight of the 748 so don't want to really go 996r route.

Would this engine require a 60mm exhaust to get the best out of it or would it be overkill for this setup?

I am not quite sure how much bhp I will be able to squeeze out of that engine yet but I want a really nice lightweight large bore system on it.

Has anyone ever had an exhaust built for them before? A friend had a full bore titanium system made for his R1 and it was a piece of art.

60mm would be over kill IMO
and very expensive.
best of with a full 50mm
and more available second hand

I've played about a lot with this, I have a 748 RS, 853 kit and every engine mod possible (really got carried away) 57mm full system worked best, 60mm was too much and the bottom end and mid range suffered.

On a 748R with 853 kit, flowed heads and de-restricted throttle bodies (the usual and most cost effective route) 54mm would be the biggest you could use. 50/54 half system works just as well though.

how much is a 853 kit for a 748 R and what are the power gains ?

853 kit on its own, i.e. not done as part of a service, is about £1200 fitted/set up, inc gaskets, dyno runs etc. etc. if you dont have an adjustable chip (FIM Ultimap) or power commander then you'll need one too.

IMO, 853R is a mega conversion, i love em! the peak horsepower figure is only up by 5-8 bhp usually, but the area under the graph is much better, more mid range, typically the power you get at 10k on the 748 you get at 8k on the 853 and it holds it until 10k, so when you change up you don't get so much of a power drop, it feels great to ride. The revy 748 but with more punch out of corners.

748 R is the best model for the conversion but you need to use high compression pistons, the 748 R pistons have large crowns and the valves are set back in the head to suit (748R has a larger cylinder head volume than the other 748 models) Increasing the bore size increases the compression ratio anyway but with flat top pistons you would lose out on a lot.

Something to think about. :D

More like something to save up for. Yum, Yum!!! :o

Hey Wilf

Who did your all your engine work and setup.

It sounds like you have done exactly what I am looking to do. Are you pleased with the results? Do you have any Dyno runs you can post / pics?

Just a guess, but probably in his lunch times at................................... ?Check the site on his thread!!! ;)

Beat me to it ;)

The other thing to watch for with the big pipes is that once you get much bigger than 54mm, you'll need the mag swingarm. it's longer so as to offer more clearance for the pipes. that'll dent the budget a little :o

erm... lunchtimes, evenings and every spare weekend in winter, Steve did the really technical stuff.

Good point about the swingarm nelly, 54mm is the biggest you can get in there, but it does fit, with a bit of fiddling.

Motor is not quite finished yet, but should be together in a week or so. After its been on the dyno and i'll post the results.

Chassis isnt quite finished either...:puzzled:

Ooops. Foot in mouth and all that!

You learn something new everyday!

Cheers Wilf. I look forward to seeing the results!

Frame looks awesome!

Blue's a bit girly though ;)

Wilf, I see you're still leaving things to the last minute as usual...

Mr_S

you, me, cadwell, now!!!

i'll have you know that's 'Purple Sparkle"! chose it myself.

plenty of time yet, not booked on track until the 2nd week of april!

:burn:

Best pull your finger out then :)

May drop in a see you guys tomorrow as I haven't had a chance to call in for a month or so and I'm in Basingstoke bright and early!!!

Wilf

What sort of power do you expect to have top end on the 853R? I am guessing top end speed is swapped for grunt lower down the range.

Sigma reckon the are seeing about 118bhp from the 853R.



Any ideas if this can be improved on?

Just found this . . . .



Sigma reckon 136mph from the 853R. That does seem a little slow when you compare it to some of the equivalent Jap bikes!

That last graph is through the gears. There's only 5 "peaks" so I guess they thought the dyno had had enough at 140mph, and didn't run it through top :lol:

118 bhp from an 853R would be the best one, after a full refresh, with the heads ported/flowed to make use of the bigger valves, cams dialled in etc not just an 853 kit fitted. the sigma graph is before and after all that work and is and example of the best they can make one, not an average.

Just fitting just the kit with set up, they make 110 - 115 rwbhp. and a better shape curve with the cam timing set correctly.

I am probably going to get shot down now by lots of people waving dyno print outs but I can only go on what our dyno says. We had a recent customer who was not happy with the dyno print out we did showing 115 for his bike??? so he took it elsewhere and without making any changes they did 2 runs and gave him a printout showing 122! so please don't shoot me down about power figures. they seem to vary depending on if you want the customer to have the real number or just keep them happy.

You can get more out of an 853R, like i say above, but once you have fitted the kit and dialled in the cams and put a larger exhast system on, the price per BHP starts to get silly.

This sounds a bit negative, but its better not to expect or get promised horsepower.

Having said that, it feels MUCH more power than it is, i'm always amazed how fast my 853RS feels.