Triumphrat

dunringil · 04-14-2004

I have read several things on the web about opening up your airbox. One site recommended that you drill (3) 1/2" holes in each side of the air box then back out your mixture screws 1/2 turn each.

Another site says, whoa, dont do that, you'll actually lose power in the mid range.

I have a 96 adventurer with a k&n jet kit & off road pipes. Getting ready to upgrade the carb inlet rubbers to a non-restrictive type.

Should I break out my drill or leave my airbox alone?

I guess I could always duct tape em up if I didnt like the results.

04-14-2004

I have a K&N airfilter on my Legend and doubt that drilling the airbox would make any diffference. There is a limit to just how much your engine can "breathe" Ride safe, Quiller :wink:

glgavin · 04-14-2004

Check out Yahoo Triumph Renegade. Go to the Files section and then Hinckley Performance. There are accounts and photos of tuning experiments, the main subject being the Adventurer. IIRC your bike may have the Mikuni carbs while most of the modifications detailed on the net involve the Keihin. From what I've read people have mixed results.
:-g

jimmyj900 · 04-14-2004

Modifying the airbox and rejetting can produce about a 25% horsepower increase and flatten the torque curve up to redline.

To make more power you need to burn more fuel, but to burn more fuel you need more air.

Download "ClassicTuning10A" for some more information.

Jim

Slinky · 04-14-2004

Sooner or later the mild cams are going to be the biggest limitation. If you are serious about tuning for power that would be the first thing I would look at.

And don't forget when it comes to engine tuning there's no such thing as a free lunch.. If you are making more power at the top end you will lose some flexibility lower down.

jimmyj900 · 04-15-2004

A couple of items on this thread:

"ClassicTuning10A.doc" has been arbitrarily renamed "Classic Triumph Tuning" in the Downloads area here.

Changing to a higher-performance camshaft (Super III, etc.) with no other mods will produce approximately a 10% increase in *peak* horsepower and extend the linear portion of the torque curve upward slightly. The peak horsepower after the cam change will move to around 7000-7500 rpm.

Modifying the filter box, rejetting, installing a "offroad" mufflers and a higher performance cam will produce up to about a 40-50% increase in *peak* horsepower at 8000-8500 rpm.

There are no cams currently available for the Triples that significantly degrade low rpm performance. Most of the so-called degredation of performance due to mods is the result of fuel mixture non-linearity.

Horsepower is a misleading marker for measuring engine performance since it's the product of torque and rpm (HP = (T x rpm) / 5252) and comparing peak horsepowers is like comparing apples and oranges -- they're both sorta round, but that's about it. From the formula it can be seen that horsepower continues to increase even after the torque has begun to roll off.

The key to performance is to look at torque via a dyno run. Ideally you want the highest, longest, flattest torque curve possible.

Jim

Blaine · 04-15-2004

Jim

I couldn't agree more with your comments about torque and horsepower. They are inter-related but the torque curve is what you feel as you run through the gears. However, I will make an exception to your comments about degradation of low speed performance with higher lift cams. What do you mean by performance? Brake specific fuel consumption goes up with increased duration even if torque remains constant. The increased overlap duration and later exhaust closing inherent with longer duration cam timing decrease volumetric efficiency until intake flow volume and velocity increase. The Sprint cams aren't as bad as the Super III cams but both lose torque below 4,500 rpm and increase fuel consumption even if the carburetion is spot on.

jimmyj900 · 04-16-2004

>> However, I will make an exception to your comments about degradation of low speed performance with higher lift cams.<<

My comment was that there "are no cams currently available for the Triples that *significantly* degrade low rpm performance." None of them (Triumph, Wilcox, Megacycle) will make the bike unrideable between idle and 5,000 rpm. Indeed, my old KZ750 had a more radical duration cam than any of these and was quite rideable at lower rpms.

>>What do you mean by performance?<<

Is that a rhetorical question? My experience is that rhetorical questions obscure discussion. If you have a definition of performance, then state it clearly: hints and misdirections merely confuse issues and stimulate conflict.

>>Brake specific fuel consumption goes up with increased duration even if torque remains constant. The increased overlap duration and later exhaust closing inherent with longer duration cam timing decrease volumetric efficiency until intake flow volume and velocity increase. <<

Yes, but one does not install a longer duration/higher lift camshaft to increase fuel mileage or to improve low-rpm operation: the purpose of replacing cams is to improve volumetric efficiency at higher rpms and allow the engine to produce more torque.

Jim

bikertrash · 04-16-2004

Hey guys,

just thought i would throw in my $.02 for whatever it's worth, on both my '98 tbs and my '03 tbs i removed the black covers to the rear of the perforated fake air cleaners and drilled about 12 1/8 in. holes in both sides of the air box then reinstalled the covers. this along with shimming the needles and going out to 2 1/2 turns on the air screws made a remarkable difference in acceleration power.just let me say I'm not a scientist and don't know all the the formulas but my butt dyno says it was well worth the effort, i was contemplating going up about 2 teeth an the rear rear sprocket to get a little better off the line acceleration but this did the trick. i also had the triumph off-road silencers as well, i will be replacing the triumph off-road silencers with the d+d 3 into 3 system so these settings will probably be out the window now.

later dudes
jeffro

jimmyj900 · 04-16-2004

bikertrash says:
>>... on both my '98 tbs and my '03 tbs i removed the black covers to the rear of the perforated fake air cleaners and drilled about 12 1/8 in. holes in both sides of the air box then reinstalled the covers. this along with shimming the needles and going out to 2 1/2 turns on the air screws made a remarkable difference in acceleration power...<<

Interesting... You'd be surprised how many filter box mods and jetting setups have been floating around.

I was working with a guy in Texas who modified the stock Classics filter box and installed a K&N filter and Factory Pro jet kit. After we got his jetting sorted, a dyno run shows his bike is producing 74.4 HP/46 lb-ft torque @ 8500 rpm and peak torque was 51.1 lb-ft @ 7,000.

Those figures are for rear-wheel power on an eddy current dyno. The peak horsepower would be about the equivalent of 86 hp at the crank, so that's 20-25% over factory stock. He's kinda happy with it. ;^}

I've installed a modified Trophy airbox with a K&N filter and a Factory Pro jet kit with larger mains than he's using, so I'm expecting a bit more top end from my Adventurer.

Jim