I’ve been talking about the importance of Air/Fuel ratios for a while now and I decided to finally get mine tested at Sand Mountain Utah yesterday. It was a good opportunity for me to learn the Dobeck 5 gas analyzer and how it can be applied to ATV tuning. Similar results can be utilized with any Air/fuel gauge.

I was lucky because I had the representative from Dobeck Performance with me. Dobeck is one of the leaders in air/fuel. Mark Dobeck, owns Dobeck Performance who makes the TFI control boxes for engines with EFI. Mark also used to own the company that built the Power Commander EFI control boxes. They use this technology to determine how much extra fuel is needed when modifications are applied to EFI and Carbed engines.

First, I let the machine warm up with a few passes up Sand Mountain and then placed the probe at the end of the exhaust and hooked up the meter for testing. We made the determination that, while under load I was indeed lean, although still within the range of tunability. After changing jetting to be richer, I actually found more horsepower and speed when I was jetted properly. After jetting on engine only, I then tuned my nitrous. I found that I was rich with fuel on nitrous and ended up tuning my nitrous system with less fuel for the best power. The new found power I found on my EX was amazing. What’s more, now I know, with my own two eyes what the nitrous system looks like on a gas analyzer – perfect! Throughout the entire run with no lean or rich spots! The comfort in knowing exactly where I am, and knowing that I will never have lean issues is a good thing too.

I’ve been running this setup for quite sometime, and I’ve always felt I had a handle on tuning the carb – I was wrong. My power increased as I actually gave it more fuel on engine and less fuel on nitrous! Our rep from Dobeck wasn’t surprised at all. He said he runs across this all the time.

In my eyes, this is the core of the issue – engine tuning! Without the best air/fuel tools, all we are doing is shooting in the dark and are possibly missing out on the horsepower we all deserve with our expensive aftermarket parts. Also, even if we are set up once to the perfect air/fuel ratio, temp changes and elevation changes can screw everything up and possibly harm our engines and our hard work.

Just so everyone knows, my tolerances on my EX are fairly tight. This is a list of my mods to my EX.

1. JE 12:1 piston
2. Edlebrock 38mm carb
3. 440 bore with 4 mil stroke = 460
4. VP C12 fuel – 108 octane
5. NOSS 25 hp shot
6. Air/oil cooled engine
7. Stock curve CDI with 1000 rpm raised rev limit.
8. slightly ported race head with 1mm oversize valves
9. Web 450/451 cams

My point in listing these mods is to show you that I have always had heat related issues with a bore and sleeve motor running 12:1 piston and going lean was always a concern, especially when running a 25hp shot of nitrous in a small engine like that. This is one of the main reasons why I run more octane that I actually need with a quality fuel that is very forgiving. I feel now that I might be able to run a less expensive fuel by having the information I need with a good Air Fuel meter at my disposal.

The entire tuning process took about 2 hours. My new found power is awesome. If any of you want to know exactly where you are in air/fuel and live in Utah, let me know and I will be happy to meet with you and measure your air/fuel to determine if you are too rich or too lean.

My next trip will be in St Anthony’s dunes this coming weekend then in Oregon throughout the 4th of July.

Marky

 

Thats some interesting info ODP... so how does the gas analyzer work? Does the sensor just clip onto the exhaust? I am assuming that there is some sort of computer that stores the air/fuel ratios through your run... am I correct? It seems that tuning by seat of the pants is as you say a shot in the dark, but I'm wondering why we don't see many people tuning with a gas analyzer.... so I'm guessing they are not cheap. I have been really interested in this subject (tuning) lately and I'm wondering if it might be a worth while investment to ensure that my tuning is always correct. My main concern is if I go to a high compression piston where tuning is more important. Anyway, good stuff there ODP, thanks.

 

Cool Marky,
what a/f ratio were you shooting for, and settle on?

measuring equipment set aside, the main jet that gets you up it the fastest is the one that belongs. but of course, without having anything to measure with, like a tach to shoot for the strongest rev, or a radar gun, it can be hard to determine this. then add NOS and I can imagine you are really starting to guess. an a/f ratio monitor seems ideal for these situations.


I too am curious of fatholly's question of how it mounts, the dynojet dyno a/f monitors are to be 12-18" inside the pipe, not possible on all pipes, disk systems can't be measured, or turn down tips. and the honda 450r's have a screwy baffle system inside only allowing insertion of about 8 or 10 inches, and that's after the core on the end is removed, wich does not allow proper measuring.

 

The Dobeck gas analyzer is the cream of the crop when it comes to Air Fuel. The measurement that we used to determine air/fuel is CO levels. Then you can take that info and use a chart to determine the Air/fuel. CO is better, they tell me, than measuring air left over after the burn. The box I used is about 12 inches long, 5 inches wide and about 2 inches deep with a large LCD display that graphicly shows the levels through a timed run. Basically you put the probe into the exhaust - it has a hollow tube and the unit pumps the gas through a hose up to the unit which you can strap to your leg. Before your run, you turn the pump on, then hit the record button. Then, you make your run up the hill and the unit automatically stops recording after sampling the gas at any pre-determined time lengh. I chose a 25 second sampling. I then simply went back to the truck and played back the run. I think he was saying that a 6% CO level (I could be wrong on this as I dont have my notes in front of me) was perfect - he was absolutely correct when it came to feeling the power. These units work on every type of engine because they use a laser or light beam to determine the spectrum of the gas and actually displays the gas levels. 2 stroke, 4 stroke, any kind of fuel - it simply does not matter. They do have a filter in there - dont know what thats for, but needs to be replaced once a year or so if you use it a lot. You can actually look through a lens and see if your filter needs to be replaced. Just so you know, Mark actually invented the dyno and sold that part of his old business. The guy is smarter than anybody else I done business - and so are his employees. Our cost around $3000 or $4000 - but most people will benefit from any good A/F meter that uses the Bosch 5 wire probe - much less expensive from an initial investment point of view.

As far as different exhaust tip - like the super trap tips. What has been done in the past is that you can drill a small hole into the supertrapp cap, and place the probe into that. I have a supertrapp end cap left over from my ODP days and will simply machine a hole into that to accept the probe tube so that folks can benefit from it. The aluminum probe tube is small in diameter and is about 6 inches long. It has a place to use a strap to hold hold the probe in place while you make a run. We simply used a bungy cord to strap it to the rear grab bar to keep it in place. The computer has an on board rechargable battery, but you can also hook it directly up to the quad battery as well. The computer does store runs, but if you dont erase them after each run, you get to watch every single run over and over until you see the last run. So what we ended up doing was erasing the last one after making the jetting change, and simply remembering the CO levels on the graph to compare the next run with it. On the display, it works such that the higher the curve on the graph went, the richer the engine. My initial nitrous runs were off the graph .... which was WAY too rich - even though it didnt bog at all. <u>This may explain why a few people that run nitrous never see the horsepower results they expect simply because they never tuned it correctly. </u> Once I came back on fuel with nitrous, that graph settled on a nice flat curve that matched my engine only graph. Once there, the time up the hill was amazing.

Hightower, the really cool thing is you wont have to make very many runs to determine exactly where you are, and fix it. You are correct, you could run a lot more times and try and feel where the power is, but you really wouldnt know where to start. And if your loss of power was due to being too lean (and didnt realize that), and determined to go leaner as a result, that could cause engine damage. This way, you only need to make one run to determine the direction you need to go.

Just so you know, Im simply pointing out that ANY good A/F meter will get you similar results - which is tuning your engine correctly. This can be done on a dyno, but the problem is you cant take a dyno with you. By having some sort of gas analyzer or A/F meter, you can take them with you and tune according to the environment you are in. The nice thing about the regulation on the nitrous, now thats tuned, I wont have to worry about that part of the system ever again. I simply have to make sure the carb is correct.

 

Very cool... thanks for the info.

 

The really cool thing, this puts the expertise of tuning into the hands of the guy that owns the quad ; as long as he has an Air/fuel gauge of course. Finally, the truth of tuning can be owned by individuals.

Who knows for sure, but all those dyno graphs of HP that manufacturers pump out when comparing other products to thiers can now be confirmed or denied. Its possible that inexpensive performance components were simply looked over or not tuned correctly. And the expensive ones were more about tuning than anything else. Time will tell.

This is huge!

 

Especially because I never trusted those idiots at the shop to tune my bike right. They get lazy and just rely on past experience instead of actually running tests. Thats actually why I started tuning my own bike in the first place... it just didn't feel right after they did it and my fine tuning always makes it better. Add to that the changing conditions through out the season and you have a bike that is never quit right. The air/fuel analyzer seems like it could be a solution. Now my only problem is convincing my riding buddies that we really need to go in on one. They never tune, and always just say... "we don't drag race, who cares about being tuned perfectly".... well I do damnit. Then they complain about how their bikes aren't running right. I try to tell them they need to mess with their jetting but their a bunch of biotches.... set it and forget it like freakin' Ronco rotiscerie cooker. Some day they will grow a sack and figure it out. Anyway I know there are more basic A/F analyzers... any suggestions on make or model?

 

Boy that is truly an awesome tool indeed, only a 6" probe depth solves alot of issues that you would run into with the 02 probes, and being able to use on 2-strokes to boot!

 

The one I posted on about 6 months ago is still probably the best one out there that most people would get. Its made by Innovate Motorsports and used the Bosch 5 wire O2 probe. I've seen them work and they do a pretty darn good job considering they only cost like $399. On Dunes Perforamance has them too.. But there are others Im sure. The reason I list that particular one, is that the last two companies I worked for, both owners had them on thier machines and I have seem them work well. The company I work for does not sell them - but I feel the one that On Dunes has is good. Innovate Motorsports has others, that may be more usefull if you wish to go in on one gauge for a group of people. Those need a hole drilled into the exhaust pipe, and a bung put in place when you dont use it. If you run leaded fuels, O2 sensors will eventually foul and the Bosch 5 wire sensor needs to be replaced - usually once a season - they cost about $75. The gauge itself is thin, and can simply be velcroed to the top of any flat surface. Hook up the power and a way you go!

The Dobeck 5 gas analyzer that we purchased is located here.. I think its the one to get if you can afford such a thing. Luckily for me the company supplied me with one. Plus a full days worth of training from the company that sells them. Since they spectrum analyze the gas, they never wear out.

 

Fatholly,

Its not just the local shops, its the so called expert tuners. I can see a lot of potential manipulation here when it benefits these experts. Who knows why else they may manipulate tuning claims especially when comparing products. Perhaps there are some builders that dont make the same amount of money selling nitrous systems as they would a big bore. Perhaps some of them dont realize they can do both. I dont want to get into the negative aspects of why these businesses do what they do. The very cool thing is that we dont have to take it anymore. Smart riders will realize that they can now have all the information and no longer be subject to expesive parts that claim high numbers simply because they were tuned correctly. Just how deep this goes is unknown. Potentially it could apply to carbs, cams, exhaust, pistons, and who knows what else.