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Has anybody disabled the speed limiter on their Thruxton R?

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18K views 26 replies 13 participants last post by  FLY-TRI-GUY  
#1 ·
Okay two things: 1) I want to do this for racing purposes, not for street use 2) Triumph technical did confirm with my dealer this bike has a speed limiter on sixth gear. After eight runs at the salt flats over three miles in length the bike stops at an indicated 140 mph and a measured speed between 135-137 mph.

Depending on the gearing the RPM is between 6200-6900 at an indicated 140 mph.

The question is how to disable or work around the speed limiter?
 
#26 ·
Agree that the ECU appears to limit both RPM and speed. Have not tried to work around either, but sure enjoyed your Speed Week video:


We had limiters built into our army vehicles in Europe. I paid my mechanic to deal with it on a 5 quarter or 1 and 1 quarter ton army ambulance. Cracker box we called them Anyway our limiters were a plate below the carburetor . It could be taken out and fit a gasket to replace. I don't know of yours but that worked.
 
#5 ·
I feel for you and I don't understand it.

What purpose does it serve for Triumph? I would have thought that some good speed runs at the salt flats would add to the appeal and therefore increase sales. I don't get top speed limits in any context.

The other question is: How might it be possible to make a replacement ECU for the bike? When I built my last kit car I made the ECU out of a kit supplied by Megasquirt. Could you make something that bypasses this issue?
 
#7 ·
Oh ffs, there is no speed limiter on the Thruxton 1200! I know this, because we've run all-gears runs on the dyno a few weeks ago, and it goes all the way to the red-line in 6th.
Let's just drop this ridiculous thread. I already explained the maths with CoD and power. Focus on why and where you're getting slippage, and stop searching for some magical computerised reason.
If you want to exceed 137mph you have to reduce drag. That will in turn reduce slippage. Try removing mirrors, tuck-down more, give it a full fairing, and replace the big flat headlight with a tapered full nose-fairing.

As I said last time, you can't guess at the reason for things in performance tuning, otherwise you end up with these crazy assumptions. Measure things properly.
 
#10 · (Edited)
A. I have run the bike in sixth gear at red line(stock gearing) on the salt in 2016. The average top speed measured not on a dyno was 131. Obviously the stock gearing at red line didn't get to where the speed is limited. I changed gearing because the bike can pull it and get more speed.

B. Once again Triumph USA said bike had a sixth gear speed limiter, why would they lie about it?

C. My go pro is mounted very far forward and I can guarantee it didn't hamper me getting out of the wind at top speed or I would not have used it. I have made over 32 runs at Bonneville and I know a little bit about riding a bike fast. My best top speed is 196.7 mph. You have no idea from watching this video what the bike is or is not doing.

D. Yes a better fairing especially with lowers would certainly help. I think it was 2013 that Allan Cathcart took a naked Thruxton with 110 RWHP to 152 average.

E. I really don't care if you and your buddies think this is a ridiculous thread, didn't ask you so why don't you go rain on someone elses parade. I really don't need you telling what I should do.
 
#8 ·
By the way, if you watch around the 2:00 mark on your video, you can see the RPM fluctuating. This is as the rear loses traction on the poor surface of the salt flats.
Another issue is that if you have a camera stuck on the top of the tank, how on earth are you getting low enough to benefit from the fairing? If I'm doing a speed run like that I'm quite literally looking through that fairing visor and my helmet is tapping on the top of the tank, otherwise your helmet and shoulders act as a huge air-brake and suck out 10mph.
There is a reason my little 1996 ZX6R could reach 178MPH, and I can tell you that I would be lucky to hit 130MPH if I wasn't tucked in properly.
Top speed is not a factor of power, it's a factor of efficiency, essentially power/drag.
 
#9 · (Edited)
Okay two things: 1) I want to do this for racing purposes, not for street use 2) Triumph technical did confirm with my dealer this bike has a speed limiter on sixth gear. After eight runs at the salt flats over three miles in length the bike stops at an indicated 140 mph and a measured speed between 135-137 mph.

Depending on the gearing the RPM is between 6200-6900 at an indicated 140 mph.

The question is how to disable or work around the speed limiter?
Oh ffs, there is no speed limiter on the Thruxton 1200! I know this, because we've run all-gears runs on the dyno a few weeks ago, and it goes all the way to the red-line in 6th.
Let's just drop this ridiculous thread. I already explained the maths with CoD and power. Focus on why and where you're getting slippage, and stop searching for some magical computerised reason.
If you want to exceed 137mph you have to reduce drag. That will in turn reduce slippage. Try removing mirrors, tuck-down more, give it a full fairing, and replace the big flat headlight with a tapered full nose-fairing.

As I said last time, you can't guess at the reason for things in performance tuning, otherwise you end up with these crazy assumptions. Measure things properly.
By the way, if you watch around the 2:00 mark on your video, you can see the RPM fluctuating. This is as the rear loses traction on the poor surface of the salt flats.
Another issue is that if you have a camera stuck on the top of the tank, how on earth are you getting low enough to benefit from the fairing? If I'm doing a speed run like that I'm quite literally looking through that fairing visor and my helmet is tapping on the top of the tank, otherwise your helmet and shoulders act as a huge air-brake and suck out 10mph.
There is a reason my little 1996 ZX6R could reach 178MPH, and I can tell you that I would be lucky to hit 130MPH if I wasn't tucked in properly.
Top speed is not a factor of power, it's a factor of efficiency, essentially power/drag.
If they were going to program a speed limit, why would it be 137 mph rather than 140?
 
#15 ·
Just looking at your video, it looked as though the speedo needle was drifting back and forth just a little at that indicated 140. Seems that if there's a hard 6th gear speed limit imposed by the ECU and the engine otherwise had the power, then the bike would accelerate to 140, and the needle would be like a rock, with power and speed limiter precisely balanced.

Not throwing any stones, just want to learn. My hat's off to anyone who'll sit a stock Thrux at that speed.
 
#12 ·
If the speed is being limited only in 6th gear, maybe you could change the wiring or whatever sensor to read 5th gear as 6th and 6th as 5th gear. Or change the gearing or location of the sensor that drives the speedometer through the ECU to read a few MPH slower than than it dose now. Any such mod likely would not be compatible with ABS or traction control so they would need to be disabled.
 
#14 ·
For all that want to argue the bike does not have a speed limiter please move on. I have also used info from Gear commander for five different bikes running top speed and many times the RPM doesn't match up with actual results. Sometimes I do better and sometimes I do worse. People race motorcycle because of the variations come out in competition. If that wasn't true everything could be settled on paper with math or on a roller (dyno).

I respect your opinions but don't have have to like being lectured to and being called ridiculous or making crazy assumptions, or not doing things properly by anyone.
 
#16 · (Edited)
Tssmgguy. Yeah it floats a bit at 140, I am also moving around a bit because it is a bit uncomfortable running wide open for a minute and half with the chin of my of helmet on the tank, toes only on pegs and arms tucked against the tank. Occasionally an elbow goes out or your head pops up to see where you are on the track so any movement causes drag and will cause the speed to fluctuate. You don't notice it while accelerating hard but you can see it when she starts to level off.

Also the cross winds will do the same thing. I have a video from 2016 speed trials where I almost hit a marker at over than 190 mph. Most of us have our heads buried and only look up occasionally but it is very risky.



















2016 ZX1400 196 3
 
#17 ·
Wow, sorry if I questioned your logic, and I wasn't intending to upset you, but it just doesn't make sense and you're starting what appears to be a whole new internet myth.
I have no idea why someone at Triumph might have told someone there was a speed limiter. Perhaps it's because on the Bobber there is one, and as with dealerships, they don't tend to be experts on every one of the 20 models of bike they sell. Next time ask if there's an off-road tune available, and there's a good chance they'll say yes to that too. It's just the way it is; there is a lot of misinformation spread around, even from Triumph importers.

As I mentioned last time, instead of pursuing comments on the suggestion that the designers are applying an illogical restriction, just spend US$80 or so and stick the thing on a dyno and get a definitive answer. Yes, you're right that the bike we ran was on standard gearing, so we hit the rev limiter, and while I haven't gone back to check the run, the theoretical max speed is about 137mph, so I would not be surprised to see the final road speed in excess of that. I suppose I could always see if I can enable rev-Xtend on the PCV and give it a theoretical max of 146mph.

Of course it's possible that for some bizarre reason on some ECUs they decided to set a speed limit above that of the rev limiter in top gear, so measure it and let us know.
 
#27 ·
If I had to have a bike factory programs and settings unlocked and reprogrammed for better performance and more horsepower it would definitely be Chris More of “ Moore Mafia” here in Florida, he knows his chit a great tuner for sure....FTG
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