Thinking of an air-fuel meter to tune carb - any experience?
 

I recently finished my car and got it on the road. I've had a few issues, nothing major. Next up, I need to optimize the tune. Brent tuned it on a dyno, but mentioned the fuel and atmosphere could be significantly different in Kentucky (where he is) vs NoCal (where I am).

There is just one shop here of which I'm aware that tunes carbs - Ole's in Redwood City). They are supposed to be very good and work on a lot of rods, but they clearly are old-school. I think they just do it by ear and experience.

I'm thinking it may make sense for me to buy a wideband O2 meter or gauge and tackle this myself. That way I could use it on both of my carb'd cars, learn how to do this right, and make sure the car isn't running too lean or rich.

Innovate Motorsports seems to be the leader in this area, and they have handhelds and gauges (cheaper, and sort of cool to see it in real-time). But one issue I have is that I didn't weld in an O2 bung when I put the car together, so I would either have to do this (and recoat the ceramic wherever I weld it), or use their clamp on the exit of the sidepipe (probably adequate and easier).

My questions are: what do you think of tuning it myself with one of these set-ups? Any experience would be appreciated - especially whether you could get the tune right pretty easily or if air-fuel meters are a rat hole. Also, what gear have you used successfully? Thanks!

I've had good with my LM-1 and the tail pipe mounted clamp. I drilled and tapped the end of the probe to accept a piece of brake line. Use a 12 inch or longer piece, then you don't have to worry about reversion at the end of the pipe messing up your readings.

I use a LM 1 as well. I use bungs welded into the exhaust pipe at the front of the collector. If you mount the bung towards the inside of the car there is no need to re-coat the pipe as it cannot be seen except from under the car. The LM 1 will do a much better job than an ear ever will. Well worth the money.

If I get the LM-2 with an exhaust clamp, I can use it on multiple cars, on both sides of the exhaust, and without removing the sidepipes to weld in a bung. Can you drive with the exhaust clamp, or only use it while parked?

Henry "Ole" Olson uses a 5 gas analyzer, as well as an LM-2. He wrote this a few years ago: tuning performance You should go talk to him if you are local to the Bay Area (San Bruno)...

I drive with it....shut the door on the wire and go. The first one I didn't shut the door on the wire and let it hang over the door...well the clamp came lose and and dragging on the ground..... had to get new O2 sensor and clamp.

I did a thread on installing a wideband O2 sensor. http://www.clubcobra.com/forums/tech...r-install.html
Last fall I bought the Innovate MTX-L wideband and love it. I am not installing it in my dash, just using it as a tool. I then will put the plug in the bung. I installed the O2 and did some tuning last fall just as it was getting cold here in Utah, so I will finish it this month.
I'm an old guy and have worked on most carbs in the 60s and 70s. The wideband is wonderful. No more reading plugs and guessing. With the one I have I can hook it to a laptop and see the AF graph as you drive or just watch the gauge. You can watch each circuit; idle, transfer, main metering, power, accelerator pump, and secondaries on the graph. Just pay attention to how you are operating the throttle. You can record I believe about 50 minutes of running and save the file, then make your changes and run it again. Then compare to the previous file.

I found that recommended jet changes for altitude by the carb manufacturer was way off. With the second jet change I am running from 14.5-15 for main metering. I still have a lot of playing to do. This is one of the funnest tools I have ever bought.

I'll check him out, thanks. But I still may get an analyzer.

a couple of years ago i purchased a kit from 14Point7.com to make my own wideband sensor - premade/retail was very expensive at the time.

Amazingly it worked (?!)

If you're going down this path I suggest a walk around the web-site becasue the products seem to keep growing & improving

LoBelly

I started down this same road have the gauge just need the O2 sensor. Also been a carb tuner all my adult life and have it down pat which made me realize it takes me no time to get the carbs working as good as they are ever going to. The plugs and seat of the pants is my gauge.
Good Luck in your quest.

Here's an excellent article of plug reading and timing.

Spark plug reading

Tuning on the Road with Holley - HOT ROD Unlimited Episode 14 - YouTube

Here is the detailed article.
On-the-Road Holley Carb Tuning During Power Tour - HOT ROD Magazine

Did a little more work on this and spoke with Innovate tech support. They recommend an LM-2, which has data logging capabilities. Also said to weld in the bung, and not to use the clamp (readings will not be nearly as good). I'm almost sold, but reading through some reviews it seems the quality and reliability of the LM-2 is pretty weak. Anyone have recent experience? They could've fixed initial quality problems.

All you need is a 02 & a volt meter shoot for 0.3 volts.

Yes, make SURE you mount it somewhere on the collector as ANY exhaust leak with throw the readings off, ask me how I know.

I've got an LM1 on a twin turbo truck, and I mounted it just after the collector as the headers were already in the truck.

Well, even with a V-band exhaust clamp I still have a very slight leak which drives the AF gauge wild. So guess what I will have to do all over again.............:mad:

I use a Lm1 on a race truck at Bonneville and it works great! After each run we can choose to or not to make an adjustment on the fuel injection. We have 3 records in 3 years. I have a LM2 on the cobra and it worked great until the # 2 sensor plug broke off the LM2 unit. It's under warranty, they fixed it and it's in the mail right now. The first time I hooked it up it read 11.5 on the left bank and 13 on the right bank. So I'm working on that problem now. It's a wonderful tool. I will keep using them.

This one doesn't have data logging, but it's supposed to be the most accurate and durable. NGK Performance Products - Powerdex AFX™. I would tune (1) idle, (2) cruise, (3) WOT, and (4) transition to WOT. So do I really need logging?

Try this one
 

This review by Ford Muscle confirmed to me the LM-1 and LM-2 are the best choice.

Paul

I don't use data loging with the cobra. Watch it real time. Although it's hard to do that at wot. I put bungs in the pipes when I built the headers. Use blue tape to hold the wires on the body to the cockpit. I drive the car 30 to 45 minutes to get it completely warm. It makes a difference in the readings.

If you do it in real-time without logging, does the unit respond quick enough? Thanks.