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Discussion Starter #1
I have now had the Thruxton back on the dyno with the Predator exhausts. This was to check if the fuelling was OK with 138 main jets and stock pilot jets. The needles are raised with one shim. This was the set up with the TORS and K&N pod filters. I can confirm the fuelling is fine, with no change to the existing set up required.

Here are the Torque and Power dyno graphs showing the TORS curves (RED) and Predator curves (BLUE). Maximum power and torque are similar for both exhaust systems. The Predators do give more power and torque almost everywhere else. The huge dip in the torque curve with the TORS at 3,500 to 5,000 rpm is no longer there with the Predators.

TORQUE: TORS 61.3, Predators 60.5 ft/lbs


POWER: TORS 70.6, Predators 71.0 bhp


Fuel/AIR RATIO:
 

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Hey Rob. What else did you do to get to 70 HP?

Sorry if you've been through this before.

Steve
 

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Discussion Starter #7
On 2006-12-07 19:27, Caffeinated wrote:
Hey Rob. What else did you do to get to 70 HP?

Sorry if you've been through this before.

Steve
Hi Steve

Engine mods:
Airbox elimination
K&N pod filters
air injection removal
head skimmed (compression ratio raised to 10.4 to 1
head ported and gas flowed

Rob
 

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Cool, thanks.

That sounds like a pretty simple mod with pretty awesome results. I'll have to look for a shop in Denver that can do the work.

Steve
 

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*edited per TCB's pointing out I had my head up my...nevermind...

Rob:

Nice to see dyno tests. The conclusion that the Predators produce more power than the TORs is, however, not supported by the data because the fuel air mixtures weren't really dialed in for either system. And in the case of the TOR's the fuel:air ratio was over rich ( <13:1 ) where the torque drops in comparison to the Predators.

In the case of the TORs, the rich mixture caused the loss in torque and horsepower, not the other way around. A test where both systems ran closer to an optimum air:fuel mixture throughout the rpm range would likely have produced much different, and more usable, results.



[ This message was edited by: Jimbonnie on 2007-02-07 18:14 ]
 

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I believe it was actually running richer on the TORS, and close to where these engines produce the best safe power(recommended between 12.8-13.2 A/F ratio) :)
 

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*yep; had to edit this one too. Thanks TCB.

"I believe it was actually running richer on the TORS, and close to where these engines produce the best safe power(recommended between 12.8-13.2 A/F ratio) :) "

Yup; too rich perhaps?

Heck; I just deleted the rest of the post; it was beyond help.

[ This message was edited by: Jimbonnie on 2007-02-07 18:17 ]
 

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12:1 air/fuel ratio is richer than 13:1 air/fuel ratio. My Thruxton produced it's best top speed at Bonneville at 13:2 A/F. Leaner, it ran hotter, but no faster. :-D Eliminating the shim would make the midrange leaner; going to a 145 main would make topend richer. :razz:

[ This message was edited by: tcb on 2007-02-07 17:46 ]
 

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"12:1 air/fuel ratio is richer than 13:1 air/fuel ratio."

TCB: You're absolutely correct. Just reverse everything I wrote concerning air:fuel mixture and I'll stick to THAT story.

The point being you've got to have the optimum air:fuel mixture consistently throughout the rpm range for maximum power and for useful comparison test results.
 

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"Jimbonnie: Absolutely. Problem is, though, you made me think, and now my head hurts!"

You should have a look at the "Fatter IS Better!" post were I've really stirred up a hornets nest. Come join my side; it'll go easier on you!
 

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Hornets nest is an understatement...... :)

Is it too late for me to join your side? :-D :hammer:

On another note, I have the Predators on my bike and I firmly believe that they are WAY more powerful than the TORS by at least 20 HP, not to mention the 30 Ft. Lbs. of added Torque and the.......oh, nevermind.....lol :hammer:

JOHN
 

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I'm afraid I agree with most of what you said, but I DEFINATELY would not admit to it.(I read the other post!) :)
 

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This and a Wideband Commander is the best dyno. See you at the Bub Trials at the Salt Flats in September.


[ This message was edited by: tcb on 2007-02-08 14:31 ]
 

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"Is it too late for me to join your side?"

Of course you can join my side John! But it's only fair to warn you I'm about to switch sides.


[ This message was edited by: Jimbonnie on 2007-02-08 19:21 ]
 
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