Are air to fuel ratio gauges and systems worth it for your daily drive carb tuning?

I plan to use it for road tripping to high altitude regions and was wondering if its really worth it to get an AFR set up. Most AFR complete systems cost about 225-300 excluding the trouble to set it up, my mechanic can tune my carb for 30$ and i was wondering if most mechanics can just tune it for 30$.

Im having troubles as is tuning my carb just right (so it doesnt flood, etc)

 

AFR is a nice to have to get precise tuning. Back in the day no one had them and you looked
at the plug color and listened to the sound of the motor to do carb tuning. Actually works pretty
well for the most part.

 

I think without a wide band and afr tuning you're guessing most of the time. Flat spots and tip in issues can't be solved by reading plugs, and usually people just throw fuel at it to fix the problem. This gets bad gas mileage, less power, and prone to plug fouling. Good luck though.

 

Not worth it. If you trust your mechanic and he does a good job, and you aren't running boost then, no its a waste of time.

I'm only saying this because are you going to take your mechanic with you to the mountains to change jets and the tune on the carb when the gauge moves to the 14:1 area? or are you just gonna watch it and get worried?


I wouldn't trust a mechanic of less than 50 years to tune a carb. anotherwords, the guy has to be at least 50 to have worked in the industry when carbs were prevalent. But if you found a good guy and you aren't experiencing any flat spots or bad points just run with his tune.

 

you don't need a wideband to tune, but it does make things quicker. the process is the same either way, you need to take the way the engine is running, either with butt dyno or real dyno, and then go from so rich it doesn't run to so lean it doesn't run, and then look at the dyno result, and pick the jet richer from where it ran the best. and this gets done on the idle, off idle, main circuit, and on the secondaries if its a 4 barrel.

with the wideband, you don't have to do quite as rich or quite as lean, and since you get to see each afr, going back to the right one is really easy.

 

spot on response =)

I was wondering how to find someone to properly tune the carb once I hit the peaks of North Carolina in case it bugs out (due to lower air pressures.) But seems like a real interrogation into someones background is needed before trusting them.

Yeah it does feel like guesswork most of the time, I've fashioned a wire for my secondaries to open as I throttle the carb, but it still flats out at certain RPMs before "burping" and kicking in the power. I'm assuming the jets on the Holley 450 I have may be too big or too small for the amount of air being given. Where is the best place the AFR can be played on the exhaust anyway? Would it be right at the headers, or a little further down so it doesn't get burnt. I just bought pacesetter headers and only 2 minutes of it warming up burnt the paint away.

Thank you everyone for your responses by the way =)

 

The elevation change from the beach 0 ft to the NC mountains, 5000 ft won't make a huge
difference and it will run a bit rich maybe. Probably won't notice it I bet.

If using a single oxy sensor, place it after the header merges into the exhaust. That will get you
the average on both rotors and keep it cool enough.

Those pace setter headers won't last so start saving for some good ones from racing beat.

 

It made a huge difference in mine. I live in IL and made the trip down to DGRR. Contacted RB before hand and they said I shouldn't have a problem with the altitude change. As soon as I got close to the mountains of TN the car bogged down. Managed to get the car down there with a well placed set of vice grips on the rubber hose going into my Racing Beat Holley limiting fuel. Tried to take it out once we got there and the same thing. Called RB again, now sitting at a gas station, waiting for my buddy and his trailer and they said I should've have sized down as far as jets. Beauty of the Holley is I was able to call a local parts store in NC and get the jets the next morning. Once changed, and carb adjusted the car was great. No AFR, but checked the plugs to make sure everything was good.

If you're genuinely concerned about taking this car into the higher elevations, etc spend the money. The alternative of being stuck at the side of the road, unprepared, is not fun. ;-)

 

No experience with the holleys but the nikkis don't suffer from this that I can see.
I live in Charlotte which is at around 600ft so not much different from Illinois I bet.

 

Well holleys are like that. 5* temp change outside could lead to a different jetting than you had the day before with those things. Garbage atomization....

 

5 degrees is an exaggeration. My Holley only acts up when the temps are around 40 or close to freezing. It was 70 degrees or so when I adjusted the carb.

 

Its not.

Tune that carb for 14.0:1@running temp at idle on a 75* day.

Then start it up and get it to temp on a 70* degree day. It wont be 14.0:1.

The Holley 4160/4150 "metering body" is not consistent at all, and the RB holley blocks actually promote bad front to rear mixtures because the fuel bowls have a slant towards the rear even if the car is sitting on level ground. If you had sight glasses on both sides of the bowls (mine did) you'd see how off it is. The rear float level looks close to flooding when the front sight glass indicates the correct level.

The emulsion tubes were butchered by RB (filled with epoxy on all 3 circuits, then bored out to an oversize bit on the lowest point in the well) which means the only time that carb is properly atomizing fuel is at very high intake velocity (5K+rpm).

My Holleys were barely even startable below freezing, with full choke set ups. Almost always needed a shot of ether to start the fire.

But hey, if you have one tuned well enough where you dont want to chuck it into a raging inferno every time it stalls in a corner, then you enjoy it.

 

That's reason 151 why I love my Nikki.

 

Same! And I didn't lose any power. And it has a manual fast idle. And better gas mileage. And mechanical secondaries. And it starts easier.

 

And it handles boost without having to spend money on nitrophyl floats or jet extensions! You also don't need two accel pumps to do it! And it goes around corners and slows down without stalling! And it can be tuned for gas mileage and power simultaneously!

That would be 13.0 part throttle cruise and 11.5 in boost. I think that's textbook perfect, right? And my idle likes to be 12.2. All of this is easy to achieve with proper air bleed mods, then jetting.

It's air bleeds first, then jets. Most have it the other way around.

 

Speaking of, I was got the AFR gauge, but I now believe that I have vapor lock.
For those of you with holley on your engine, you probably don't have a return line. So how do you possibly prevent vapor lock?

 

I ran my Edelbrock dead headed. Never had an issue with vapor lock, but I also ran a pretty crappy off the shelf fuel pump with a built in 4# regulator. and the tank I was using wasn't exactly sealed.

 

What did you do with the return line that stuck out of the fuel tank, did you plug it off at the end?
That's what I ended up doing today before sundown to turn in. My car would have just enough gas for a minute before going dry.

Fuel PSI gauge usually sits at 5, but went up to 10 before cutting the car off. I'm assuming the extra pressure is all vapor.

I'm just hoping the holley blue pump isn't burnt out from these 1-2 minute tests.

Edit: I'm using this to understand vapor lock
http://www.airtexproducts.com/news-w...apor-lock.aspx

 

I didn't have the foggiest clue what any of them did at the time*, so I just left them alone. And used the one line that went to the bottom of the tank as my fuel source.

I can tell you one thing about running a big 4 barrel carb on a rotary engine. MAKE A HEAT SHEILD. if you haven't already. Just cut a piece of sheet metal in a rectangle and drill a couple of holes in it and bolt the sucker under the intake. It will make a world of difference.





*I still don't really know what they all do

 

I had fuel delivery problems with the Holley until I ran a return regulator.

 

damn that sounds like a good idea, the exhaust right at the header does give off a lot of heat and that may cause it.

a return regulator, as in a regulator for the return line?

I noticed on the GSL-SE fuel tanks they have a little contraption with fuel lines that are probably for breathing. Should I plug those off as well as the return line? or leave them be.

Trying to understand vapor lock, and some mention that the fuel tank needs to breathe, but some make it seem like vapor lock occurs because the fuel tank doesn't have enough pressure.

 

Wait, do you have a GSL-SE tank or something?

 

Your fuel tank has a breather regardless of SE or not. It needs to be open. If you cap it, youll build pressure up in the tank and whats happening to you will continue to happen. The small hose leading into the charcoal canister is this vent. LEAVE IT OPEN.

And a return regulator is a normal regulator, except that it has an extra outlet labled "Return" it returns excess pressure on the ball and socket back to the fuel tank if you still have the factory return line hooked to it

 

Yes, I put a 12A into a GSL-SE. was cheaper than trying to get a clean GSL-SE for under 4k in Miami. A lot of the GSL-SE for 4~6k had rust somewhere, damaged interior, messed up wiring, etc. etc.

I've seen these regulators from holley, but they cost triple the price of normal reuglators for some reason. (only payed $20 for mine), friend at the time said I didn't need a return line if I had an edelbrock carb so I went with it. But that may have been bad advice.

 

It was bad advice.