Triumph Rat Motorcycle Forums banner

1 - 20 of 24 Posts

·
Registered
Joined
·
123 Posts
Discussion Starter #1
I have been working on the carb/exhaust settups on my Tbird, TBS and Bonneville the past couple of months. Now that I have all three running fairly well (thanks to a lot of help from this site) I am thinking of the next step. I have already invested in a carb synch tool and am considering one of these:

http://www.airfuelratio.com/

The price seems reasonable for what could conceivably save a lot of time and effort to get an optimum state of tune. Anyone else have experience with this technology and would you recommend?

best regards to all,

Ted
 

·
Registered
Joined
·
1,034 Posts
this is not an exhaust gas analyzer that is stuck up the tail pipe . it requires an 18mm welded in boss where you install the sensor .

read here the copy/paste funtion is disabled on this page or i'd ....
 

·
Registered
Joined
·
123 Posts
Discussion Starter #4
Hi Ted,

Isn't this just for injected fuel systems, rather than our carbs?

Geoff
No, we have to tune our carbs for A/F ratios also. That is what the screw under the brass plug (US models) on the front bottom of the carbs is for across the entire RPM spectrum. Jetting and needle height vary the fuel air mixture at various points up and down the RPM range. It is my understanding that to get the optimum settup one needs to put the bike on a dyno and check the exhaust gas ratios for A/F mixture all across the power band as well as sample the exhaust for five different trace gases. Even then one has to make decisions on whether one desires smooth running across the band or absolute power output. This little tool just allows one to get a lot closer to the optimum 14.7 to 1 ratio running the bike on a stand. (That is my understanding, I am certainly open to correction by the real gurus on this site)

As for the 18mm boss: On my Thunderbirds (and the Bonnie) there are predrilled and threaded ports on the headers for the A/F sensor. I haven't measured it, but I was thinking (hoping) it was a standard.
 

·
Registered
Joined
·
2,073 Posts
"As for the 18mm boss: On my Thunderbirds (and the Bonnie) there are predrilled and threaded ports on the headers for the A/F sensor. I haven't measured it, but I was thinking (hoping) it was a standard."

I think that will be your snag.
 

·
Premium Member
Joined
·
2,255 Posts
Air/fuel ratio is certainly an important aspect of both smooth running and power production in an engine and tools to measure it are important tuning aids. With that said, these tools are often oversold and under-described by their vendors. While they are useful for analyzing steady-state flow, most practical fueling issues occur in transient flow situations (i.e. when you rapidly open or close the throttle). Fuel/air measurement in such cases is usually too slow to accurately represent the actual state in the combustion chamber, which is why modern EFI systems cannot tune themselves via negative feedback.

There is also an issue with linearity of the sensor element, which limits the accuracy of its measurement to the middle of the range. Wideband sensors have a large range of measurement, but the signal variance in the midrange may not be sufficiently sensitive to produce a usable signal change even though operationally significant mixture variations have occurred.

From your (admittedly brief) post, it seems that you might be laboring under an overly simplified understanding of the importance of stoichiometric ratios. This condition can only be sustained under light load conditions without incurring excessive (i.e. damaging) combustion chamber temperatures. In practice, fuel/air ratios need to be enriched under high load/power conditions so that the excess fuel can cool the combustion chamber through evaporation. Mixture enrichment is also used to overcome engine-specific fueling issues due to flow imperfections at different RPM settings. In other words, attempting to run a 14.7 mixture across the entire RPM range will quickly destroy an engine if you can get it to run at all!

There are numerous books that describe various aspects of this, but Building & Tuning High Performance Electronic Fuel Injection by Ben Stradler (SA Design, 2004) has a very cogent explanation of fueling issues and related measurements.

Hope this helps.
 

·
Registered
Joined
·
493 Posts
Thanks Coroja for the tip on the book. I've looked into this briefly but still want to do more research. Everything I've seen corroborates your statement about a 14.7-1 A/F ratio though. it seems 13-1 is a better target.

As far as those ports on the headers of the Bonneville, I have not found any available A/F sensors that come anywhere close to fitting those. If anyone know of sensors that fit them I'm all ears. They are way smaller than any of the sensors I've been able to find. One of these days I'm probably going to break down and get a similar unit like this but I''m pretty sure it will require a large hole in the cross-over pipe with a boss welded in.

I just re-read your first post Ted and seeing that you indicate you've researched within this site you probably already know that the fine folks at Jenks Bolts provide this free download resulting from the research they've done for the Bonnevilles anyway. It makes for good reading and is available here: http://www.triumph-bonneville.com/images/Carb Jetting Info 2007.pdf
 

·
Registered
Joined
·
2,073 Posts
Coroja,
Could you repeat that in english?
Just kidding, I believe that's why there's no replacement for a dyno when jetting.
 

·
Registered
Joined
·
123 Posts
Discussion Starter #9
From your (admittedly brief) post, it seems that you might be laboring under an overly simplified understanding of the importance of stoichiometric ratios.
All my understanding is overly simplified. It makes life much easier to cope with.

In any case, I appreciate the various inputs as well as the reference material (I printed out the Jenks white paper immediately). I really didn't expect this little analyzer to take the place of a dyno tune, I just thought it might make adjusting the A/F screws a little more precise. I was also suspicious of the port size, just glancing at them, they appeared quite small compared to the pictures of the sensing module. Since the ports are there I was hopeful someone had been able to find a sensor to fit. . . seems odd that Triumph would go to the expense of inserting a sensor port that wouldn't fit commercially available sensors. but what would I know? I have a simplified understanding. . . . .
 

·
Premium Member
Joined
·
6,462 Posts
Don't know if you're aware of the Gunson Colourtune ?

It works by replacing a spark plug with one that has a clear top which displays different colours according to mixture. I've never used one, but they've been around a long time & I've seen reports of success with it at different times. Really not much use for jetting adjustment other than the pilots or very light throttle (mostly still pilots there anyway). A bit fiddly, they provide a kind of mirror tube to look down at the plug top. I gather it helps if you have a dimly lit space to work in as the output of the device is not very bright.

Here's a link I found for you in the US:

http://www.autoexpertproducts.com/colortune-12mm.htm

and Gunson's UK site

http://www.gunson.co.uk/tools.aspx?cat=673
 

·
Registered
Joined
·
493 Posts
Hey Danny... thanks for the tip. I'll ask my dealer about it to see if he knows anything. If so I'll post. This may help Ted and me too if I can find anything

Hey Irl Mike.... thanks, that's a good tip too. Personally I am just looking for a means of seeing if my A/F ratio is in the ballpark across the range. Once I know that I'll just leave it be. I don't really need a gage to read at all times. But that's just my personal need. This is Ted's thread; I do not want to steal it.
 

·
Registered
Joined
·
123 Posts
Discussion Starter #14
Don't know if you're aware of the Gunson Colourtune ?
[/url]
Mike,

No I wasn't aware of this device. It looks promising, I think I'll order one today and try it. Thanks!

btw, I checked with the Indy dealer on the availability of an A/F meter from Triumph. No joy. The shop said that they just used a probe up the exhaust and didn't use the provided ports. Mike said nothing available from "tools."

I wonder if Triumph uses the ports in their initial setup of the bikes to meet the US EPA standards? If so, someone at the factory didn't do a very good job on my TBS, I'm guessing. Once I drilled out the A/F plugs I found: Carb one 1 3/4 turns out, Carb two 2 3/4 turns out, Carb three 3 1/2 turns out. That is what started me down this path trying to determine exactly what was going on that caused the three carbs to be initially dialed in so differently (assuming that the factory measured the exhaust gases to dial them in.) When I rejetted I turned all three out the same (2 1/2 turns.) Of course I changed the whole balance picture with the K&N filter, extra hole in air box, larger pilot, main jets, adjusted needles and EPCO reverse cones..
 

·
Premium Member
Joined
·
6,462 Posts
Sned

That's a very surprising difference on those pilot screws :confused:. When I tried playing with mine, mainly just a bit of tweaking with carbs 1 & 3 - middle one too difficult to get at without a proper 90deg tool - I found that a quarter turn could make a noticeable difference. Tho' if that upset the balance maybe that's what I was seeing (hearing)...

It will be interesting to hear how you get on with the colourtune - not taken the plunge as I've considered that I've been lucky enough for 2.5 turns on each to give a reasonable tickover, pickup & rolloff behaviour.

btw, you have done the carb balancing with a vacuum gauge kit ? IMO smooth running is really sensitive to good balance - literally an 1/8 turn on the adjuster screws can make a big difference.
 

·
Registered
Joined
·
123 Posts
Discussion Starter #16
Sned

That's a very surprising difference on those pilot screws :confused:. When I tried playing with mine, mainly just a bit of tweaking with carbs 1 & 3 - middle one too difficult to get at without a proper 90deg tool - I found that a quarter turn could make a noticeable difference. Tho' if that upset the balance maybe that's what I was seeing (hearing)...

It will be interesting to hear how you get on with the colourtune - not taken the plunge as I've considered that I've been lucky enough for 2.5 turns on each to give a reasonable tickover, pickup & rolloff behaviour.

btw, you have done the carb balancing with a vacuum gauge kit ? IMO smooth running is really sensitive to good balance - literally an 1/8 turn on the adjuster screws can make a big difference.
Mike,

I have the vacuum gauges but hadn't synched the carbs yet. That was on the agenda for this evening.

What I hadn't related was that the bike would hardly run when I got it. It was so lean that on a cold day it wouldn't run without the choke on full time. Now it runs really well from idle up to about 5000 rpm. At somewhere north of 5K it stumbles a bit then comes back strong up to redline. I think I need to up the main another notch or three (105 now) but taking the carbs off and on is such a hassle with that airbox monstrosity I thought I would synch and get the A/F screws spot on before I tried changing the mains. . . . again.
 

·
Premium Member
Joined
·
6,462 Posts
Mike,

I have the vacuum gauges but hadn't synched the carbs yet. That was on the agenda for this evening.

What I hadn't related was that the bike would hardly run when I got it. It was so lean that on a cold day it wouldn't run without the choke on full time. Now it runs really well from idle up to about 5000 rpm. At somewhere north of 5K it stumbles a bit then comes back strong up to redline. I think I need to up the main another notch or three (105 now) but taking the carbs off and on is such a hassle with that airbox monstrosity I thought I would synch and get the A/F screws spot on before I tried changing the mains. . . . again.
Ah, I see. Know what you mean about the airbox :eek:, tho' I'm getting pretty deft at it now :rolleyes:. Just a thought about your main jets...I wonder if you're not going the wrong way, it can be very difficult to tell sometimes? I've done the 'airbox shuffle' a few times in the last few weeks to dial in a new dynojet it (Keihin kit for TBS, but Legend same jets etc.). I have a K&N filter & Thunderbike 3-1 exhaust. I started out with DJ's recommendation for K&N + 'freeflow' Exhaust, mainjet DJ104 (their jet nos. are different from Keihin's - believed ~ 2 points higher, so these would be ~ 102 in KH).
That resulted in 'stumbling' around 5 or 6k rpm, bit similar to yours maybe? I went down to DJ102s & finally to DJ100s - probably fairly stock. All good now & feels very sprightly right through. Not sure what mods you have, but this agrees with what Jimmyj900 has previously recommended for my bike - maybe + 2 on main jet, definitely not more.
Hope this helps..
 

·
Registered
Joined
·
123 Posts
Discussion Starter #18
Mike,

You may be right. I used an FP jet kit specifically for the TBS. The largest jets in the box were 105's. Since I was using a K&N and Epco reverse cones, I thought that I should use the biggest jets. It looks like I was wrong, I know the Epcos don't flow as well as a Thunderbike (does anything?) I'll drop it down to the 100's and see if that clears up the stumble. Thanks, you probably save me a couple of tear downs!:)

btw, I did the synching last night. I was a bit intimidated by the directions on the vacuum gauge, but it turned out to be a breeze. All three are spot on now.
 

·
Premium Member
Joined
·
6,462 Posts
Cool :)
 

·
Premium Member
Joined
·
2,626 Posts
I built an air/fuel ratio monitor a few years ago and found that it was only useful for steady state (constant throttle, constant speed) applications. For variable-state applications (acceleration!) it was completely useless since the CV carb internal geometry varies with engine draw and intake velocity.

It also requires a heated (four wire) wide-band oxygen sensor. The temp of the sensor has to be maintained IIRC at about 700 degrees F to function properly and the heater pulls about 4 amps.

To install the sensor in the exhaust, I used an "anti-fouling" sparkplug adapter from the local auto parts shop. It's a gadget that screws over the sparkplug end and then into the plug hole in the head. Sawing the end off that gave me the 18mm threaded insert that I welded into the siamesed pipes on the right side.

The small bolts in the exhaust downpipes near the cylinder head appear to be for EGT (exhaust gas temperature) sensors that are used by the factory to set up the idle mixture.


SNED:
If so, someone at the factory didn't do a very good job on my TBS, I'm guessing. Once I drilled out the A/F plugs I found: Carb one 1 3/4 turns out, Carb two 2 3/4 turns out, Carb three 3 1/2 turns out. That is what started me down this path trying to determine exactly what was going on that caused the three carbs to be initially dialed in so differently (assuming that the factory measured the exhaust gases to dial them in.) When I rejetted I turned all three out the same (2 1/2 turns.)
Mixture settings can be very dependent on the fuel level in the carburetor float bowls and the synchronization of the linkage. I doubt whether the factory blokes spend a huge amount of time setting up either with precision.


What I hadn't related was that the bike would hardly run when I got it. It was so lean that on a cold day it wouldn't run without the choke on full time.
That's a primo symptom of dirty pilot jets. As they varnish up, the jet diameter is reduced and the mixture goes lean so applying some choke richens it up a bit.

Jim
 
1 - 20 of 24 Posts
Top