Triumphrat

motothrux · 07-02-2005

Could be a wild goose chase , but has anyone any knowledge about the difference cam's in the Thruxton compared to the bonnieville, was told that the Thux has a "detuned" ? cam and that the bonnieville is better!

I ain't no mechanic so could be way out of left field.

Nang · 07-02-2005

Don't have the specs of lift/duration but I'm sure the Thrux has a warmer cam than the bonnie. I think, but ain't sure, new 865 bonnie motor doesn't quite match the Thrux for power/torque so I expect the cam has something to do with the difference.

[ This message was edited by: Nang on 2005-07-02 21:21 ]

Panthermark · 07-02-2005

I've always thought that the Thrux had hotter cams then the 05 T-100, but this may not be the case. If you look at the service manual, the part numbers are the same.

Nang · 07-02-2005

Just checked the specs on the official Triumph site. 05 T100 - 63hp and 50ft/lbs. Thrux 69 & 53. Something is giving the Thrux the extra ponies and I reckon its more than just the exhaust.

Panthermark · 07-03-2005

I think it's the exhaust.

Bonnies have that "kink" in the headers right where the mufflers are mounted. The Thrux has straighter headers with reverse cones mounted.

I can't think of anything else.....airbox maybe?

badrufus · 07-04-2005

I think the cam on the Thruxton is hotter, ie, more power at the top of the power band.

WANG · 07-10-2005

Here are the cam specs that I have seen tossed around the web:

-Thrux intake------------------790 Intake
lift .374"-----------------------.374"
IO 4*BTDC------------------19*BTDC
IC 48*ABDC-----------------43*ABDC

-Thrux exh-----------------------790 exh
lift .374"------------------------.374"
EO 32*BBDC------------------38*BBDC
EC 22*ATDC-------------------7*ATDC

These are supposedly from the FSM, which I don't have, maybe an FSM owner could do some fact checking for us?

By all appearances, the 790 cam is indeed more suited to high RPM operation than the 865 cam. Perhaps this is why 790 owners have had such great gains when modding their engines compared to those gains made by 865 owners. For the sake of academics, I would like to see the results of an 865 engine with the 790 intake cam only.

If the specs that I have shared are factual, the fabled Thruxton "hot cams" are indeed merely myth.

Dave67 · 07-10-2005

maybe the bonneville cam is better suited the the smaller cc and presumably quicker to rev 790 engine ??????

simariarly how would a 790 engine go with 865 cams in it ???

WANG · 07-10-2005

I stopped trying to make sense of the way that Triumph do things quite a while back.

I used to own a Bandit 1200, the engine in it was a larger displacement, detuned version of the 1990 GSXR 1100. I swapped the Gixxer cams into the Bandit (and a few other things) for a pretty good result. It seems that a similar relationship exists between the 790 and 865 engines here.

With the Suzooks, the relationship was intuitive, with the Trumpets it is ass-backward.

Panthermark · 07-10-2005

There are "three" engines in out there. The 790cc engine, the 865cc Thrux, and the 865cc 05 Bonnie T-100. The cams might be different beteen the 790 and the 865, but according to the manual. There is not a difference between the cams on 865cc Bonnie and Thrux.