Triumph Rat Motorcycle Forums banner

1 - 18 of 18 Posts

·
Registered
Joined
·
827 Posts
Discussion Starter #1
What is the purpose of the Restrictor plate and what will it do for the bike to remove it?
If remove, must you rejet?
Is this almost as good as removing the Airbox?
Thanks!
 

·
Registered
Joined
·
666 Posts
My guess as to the why would be with the stock pipes etc the restrictor would help low end or midrange performance. Once you add free-er flowing exhuast you need to open up the intake to let more air get to the engine to take advantage of the free-er flowing exhuast. I took my restrictor plate out today and with the stock air filter I didn't notice any difference but as soon as my UNI filter comes in I expect it will make more of a difference. It is about time I took full advantage of my pipes! If you have stock pipes I doubt you would get any benefit from removing the plate.

From what I have read here It seems that the K&N pods flow better than K&N filter in the stock airbox, I am certain by next spring I will have gone with the pods because I have the disease that it seems so many of us have, you can fix something that is not broken!
 

·
Registered
Joined
·
3,588 Posts
I wouldn't remove the restrictor plate unless you have free flowing silencers. Yes, once you remove the restrictor plate AND have free flowing silencers installed, you must rejet (and possibly shim or change to richer needles) to get the fuel/air mixture correct. Until you get this mixture correct, your bike will probably not perform any better than stock and possibly worse than stock. When I installed the NARK with NH Toga silencers, mine ran about like stock with 140 main jets and Thruxton needles. When I put the 150 main jets in, it really turned on at higher rpms. The 790's respond very well to free flowing silencers and a lot less intake restriction, IMHO. I never removed the restrictor plate--I went straight to the NARK; however, once jetted properly, one should get good performance gains from restrictor plate removal, IMHO.

Larry
 

·
Registered
Joined
·
2,472 Posts
Alrighty then,

I did 22,000 miles on a 790 with D&D pipes, a K&N air filter, expensive NH bellmouth, and some Thruxton needles,
BUT the ristrictor plate was removed.

I've since done 600 miles on my current 790 with the same D&D pipes, same K&N air filter, same NH bellmouth, and the same Thruxton needles..........
but with the restrictor plate still in place.

The following is my conclusion, make of it what you will:

With the restrictor plate removed, throttle response is improved. But she needs to be spun up with enough air moving into the air box for everything to be married and work in concert. The engine feels like it has more *punch* when the conditions are right, but THAT'S what makes this combination left for lacking..... conditions gotta be 'right'.

If you're tooling along in a high gear at cruising speed, but not fast enough to be forcing air up the throats of the carb's..... and you grab a hand full of throttle, the engine reacts in a fashion similar to "turbo lag"..... a slight delay before the party. I would not have been able to identify this "lag" had I not ridden my current bike with it's restrictor/divider plate in place.

With the plate in place, the engine is more user friendly, the power more docile and linear, and more responsive to throttle input when you're just tooling along at legal speeds in a higher gear. I don't feel any loss of power in the broad scheme of things, and when I researched the various recommendations for jet size with the plate removed, they didn't call for larger main jets unless there were additional factors in the changes being made.

Bottom line, if you live in the 'party zone' of your tach while chasing little Honda 600's through the canyons, and you don't want to go to the expense of an air box elimination, a restrictor plate removal will give you more (felt) throttle response, but it won't give you significantly more power.

At least, that's what I've concluded.......
and I'm leaving mine in. If you wanna tear your air box apart to get at the plate, you may as well remove it and install pods.

:cool:

[ This message was edited by: FattRat on 2006-11-26 11:58 ]
 

·
Registered
Joined
·
3,617 Posts
Take a sawzall to the air box and get it out of there! The air box removal system is the way to go. The bike revs so much smoother and gets to the power (what there is) quicker.
 

·
Premium Member
Joined
·
476 Posts
Mods to my T100

Initial configuration:
- AI removed
- Baffle removed
- Added .020" (0.51mm) shim under the carburettor needles


Dynotest Results (values at the back wheel)
1st run:
Power 60.6 BHP at 6,831 RPM / Torque 67.4 Nm at 6,062 RPM

Second configuration:
- Snorkel removed
- Thruxton carburettors needles
- 116 Main Jet
- K&N Air filter


2nd run:
Power 58.9 BHP at 6,986 RPM / Torque 69.0 Nm at 3,562 RPM

Third configuration:
- Air Box Restrictor plate removed

3rd run:
Power 61.3 BHP at 7,295 RPM / ]Torque 71.3 Nm at 5,769 RPM[/b]

Below you can see the comparisons:

First and second run


First and last run
 

·
Registered
Joined
·
827 Posts
Discussion Starter #8
So do you feel like it was worth it from first to last run?

[ This message was edited by: 5bassman on 2006-11-26 13:28 ]
 

·
Premium Member
Joined
·
476 Posts
Definitely!
The figures and curves talk for themselves.
I did 5 dyno tests in total and this is the best configuration for my 2006 T100.
- AI removed
- Baffle removed
- Air Box Restrictor plate removed
- Snorkel removed
- Thruxton carburettors needles
- 116 Main Jet
- K&N Air filter

Soon I will write what the mpg with this configuration is.
 

·
Registered
Joined
·
827 Posts
Discussion Starter #10
Soon I will write what the mpg with this configuration is.
I'm really interested in that. My bike runs great for me with BC Predators,AI removed. I have a chance to pick up the Airbox Elimination Kit at a great price but I don't want to mess up a good thing plus dump alot of money into something that might not benefit me(but maybe others). I'm not a racer, just a cruiser. :)
 

·
Premium Member
Joined
·
476 Posts
On 2006-11-26 13:50, 5bassman wrote:
I'm not a racer, just a cruiser. :)
Same here! :chug:
All I wanted was a linear operation. As you can see on the graphs, the power and torque curves are very nice progressive and smooth. I can assure you that it does feel on the riding.
As far as fuel consumption is concerned, up to 5.000 RPM (my normal cruising regime) the Air/Fuel mixture is steady at 13x1 (ideal) only slightly increasing thereafter.
I don’t know the normal price in the US but here a Dyno Test costs €20.00 (US$26.00). I think it is a very worthy investment. Nothing replaces it when it comes to REAL facts and figures.
 

·
Premium Member
Joined
·
476 Posts
Today I did a long ride to check the fuel consumption.
In a mix of highway, high speed, back roads, start/stop the average was 40.3 mpg (5.84 litres/100km).
The best I've ever achieved (highway/low speed) was 44.6 (5.28 litres/100km)
I'm very happy with the result.
 

·
Registered
Joined
·
381 Posts
On 2006-11-26 13:41, JMV2006 wrote:
Definitely!
The figures and curves talk for themselves.
I did 5 dyno tests in total and this is the best configuration for my 2006 T100.
- AI removed
- Baffle removed
- Air Box Restrictor plate removed
- Snorkel removed
- Thruxton carburettors needles
- 116 Main Jet
- K&N Air filter

Soon I will write what the mpg with this configuration is.

Maybe I got this wrong but I thought the T100 & Thruxton carb needles were the same.



??
 

·
Banned
Joined
·
9,598 Posts
I wouldn't even attempt to guess why, but in the time i've been reading this forum i've seen both people who have seemed to gain from it and those who found it to be detremental. The majority having experienced the latter which is why you hear so little about restrictor removal than other airbox tweaks.Seems to be the same with the cruisers as the bonnies. I wish i knew why because if i thought it would help i'd do it. But the 05 cruisers, at least the SM don't have removable restrictors so i'd have to cut it out which means getting a new airbox if it hurts performance.
 

·
Registered
Joined
·
505 Posts
Looking at the data, the only statistical ly significant change I see is the increase in torque midrange which is probably due to the Thruxton needles. I think he needs a more free flowing exhaust to go with the other mods, IMHO
 

·
Registered
Joined
·
3,588 Posts
I'm not seeing enough differences to compare "mod" results, IMHO. I would suggest checking the part number of the carb needles--I believe your '06 T-100 carb needles has the same part number as the Thruxton needles--what Spanner said. I doubt if anything more restrictive than TOR's would benefit much (if any) from restrictor plate removal, and I have doubts about TOR's. I don't know which is the biggest bottle-neck--the stock silencers or the stock airbox--but both do a good job of restricting air flow. Pull the silencers off sometime and look at the inlet--just past the curve is a reducer that reduces the size of the inlet to at least 1/2 the area. All the baffle removal in the world will not get rid of that restriction, IMHO. Toga, Toga, Toga. :-D

Larry
 

·
Registered
Joined
·
1,408 Posts
The Triumph factory built the Bonneville with a twin-plenum airbox. The twin-plenum design combines desirable intake resonance along with specifically chosen intake air velocity to make the constant velocity (also known as "constant vacuum"...) carburators work optimally at a wide variety of speeds. The metering of pressure is quite important with this design, as differential pressures effect the rising and falling of the carb slide. If this value is off throttle response suffers.

By removing the plenum divider (aka "restrictor plate"), the airbox is turned into a single-plenum design. The resonance (think of it as an echo that helps to charge the cylinders) of the intake is changed and (more importantly) the charge velocity is reduced at all, but full throttle applications. Reduction of charge pressure at lower rpms means that the metering holes on your carb are now the wrong size to operate the slide diaphram. The carbs will flow more air, but will only work optimally at full throttle settings when the slide no longer is controlled by differential pressure (because it's completely open). Therefore, you will wind up with improved top-end performance at the cost of throttle response at idle and throughout the midrange.

Because I ride my bike mainly in the midrange, I have left my plenum divider in place. I have been able to enhance my power peak with a freer flowing exhaust, a Uni air filter, a N-H Bellmouth, and careful rejetting. I am certain that I have left a few WOT horses untapped, but I really enjoy the linear throttle response that I experience with this setup.
 

·
Premium Member
Joined
·
476 Posts
My mistake!
The kit is not FROM the Thruxton but FOR the Thruxton.
It is supplied by the Dutch company Tovami and consists of needles and 116 main jets.
Sorry! :wink:

[ This message was edited by: JMV2006 on 2006-11-29 08:00 ]
 
1 - 18 of 18 Posts
Top