Heckeng Posted September 23, 2006 Share Posted September 23, 2006 This thread was started from a question Wallaby asked on this thread: http://www.firstgenmc.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=001845;p=1#000021 I started the new thread so we wouldn't hijack Sam's original carb thread. Wallaby posted this: "Ok, I'm learning something here. I'm going nuts trying to get my Q-jet to do what it should. I gave up and bought a new one outright from carb shop (stage 2) and it was worse in some respects. As I go along making changes I feel I am gaining experience and if nothing else, I have a long list of things that don't work. Each time I feel I must be getting closer, but looking back, I've been involved with the process for 3 years. I'm ready to admit defeat and send the car to someone that charges big money to do the tinkering for me. You guys that have the O2 sensors; is it really helpful or does it continually remind you of how wrong things really are? I have the Autometer A/F gauge and it isn't wide-band. That stupid gauge has probably caused me to do more work than any other item. I don't think it is capable of giving me any useful information. If I was tuning by the seat of my pants, I'd be done a long time ago. Some of the questions I have for you O2 users: Does engine temp change the readings? I see that ign timing does, and that was my next question...Next, I'm wondering if camshaft profile changes the target ratio you want? If a cam has some overlap, I figure it must dump more unburned fuel than a short duration cam would. Wouldn't it make sense then that you would want the setup to read richer across the entire operating range to make the engine happiest? If I shell out for an 02 meter like the LM1, are there instructions to help the user sort out this complex balance? Also; would it be best to get the unit with the MAP and TPS and RPM sensors ($$)or is the basic unit good enough? A lot of questions, I know, but it's bad enough that I've gotten pretty bitter towards my car." Wallaby, my opinion is that you need a Wideband O2 unit if you use one at all, otherwise you don't have a good ideal of how large of a change you need to make, and also, the narrow band units only point to 14.7:1 a/f ratio (in my experience) so you can't tell if you are where you want or need to be or not. I have used Quarterbooty's LM1 and he has also gottent he manifold pressure, and RPM attachments, which I think are critical. without manifold pressure, you don't know what loading your engine is seeing, and without rpm, you can't tell where in the range you have the problem. It takes a while to get a grasp of how the carbs work, and how to adjust them, and I have not worked with an edelbrock, so I can't help you there. I would look at the innovate website and see other peoples experiences with your style of carb, and go from there. To my knowledge, there is no set rulebook for adjusting carbs, just using logic and learning how the circuitry of your carb works and adjusting once you have a handle on it. there are lots of supporters and people who offer help on the innovate site. Simply taking my carb apart, and following the fuel paths out to see how holley style carbs work has been the biggest help for me though. Before you dump the $$ into the LM1, post some questions on the innovate site and get some advice from people there. Make sure that you can get support for your carb from someone there, or possibly here. there are several people here who have used the LM1 also. At first, expect to be overwhelmed by not knowing how to adjust using the O2 sensor, but it will come to you, like it did me. Lots of things will affect a/f ratios, including temp, timing, all of the above. I would think that cam profile would have a minor effect on a/f ratio, not because of the extra fuel being dumped, but because it may allow a higher amount of scavenging to pull more unburned AIR through the cylinder and into the exhaust, which would give a higher amount of unused O2 being measured by the meter. I don't think that that would be enough to worry about as it would just mean that you would richen it up a little more, which would fail on the conservative side. Link to comment Share on other sites More sharing options...
MeanMonte Posted September 23, 2006 Share Posted September 23, 2006 the LM1 will make you want fuel injection real bad! but with time and given you have an adjustable carb and can put the meter to use its the best thing anyone can have short of a dyno to tuen your car. I have the rpm converter and a map sensor to know how much load i'm under and to know how many rpms. otherwise your really going to be lost. I take my laptop to the drag strip and can view graphs of my runs and get an idea of where i need to go. On the street you can just record onto the lm1 up to 44 minutes. But be prepared its hard to tell exactly what happened when on the recording so its also easiest to drive around with help and watch the live data on a laptop so you can simulate different conditions and see directly what is going on. Your entire engine combo affects a/f and there is no magic number. Also worth noting is that if your only in it for gas mileage dont waste your time. the price of the unit rules that out would take forever to save that much money in gas on a car you only use on occasion......then you have to figgure in a bunch of extra driving around only to tune the thing........... then theres the fuel lost at carb recalibrations........ im thinking it goes like this: Innovate LM1--> $459 Six tanks of gas-----> $360 Jets air bleeds small parts------> $150 Finding out that your carb won't work the way you wish it would--------> EXPENSIVE! For every other reason than fuel mileage theres the wide band 0'2. Do yourself a favor and dont waste the money on a WB for a Q-jet buy a top of the line holley and youll be leaps and bounds ahead for the same money. Link to comment Share on other sites More sharing options...
quarterbooty Posted September 23, 2006 Share Posted September 23, 2006 I have to chime in here. In my opinion, the A/F meters that just have LEDs to tell you which side of stoichiometric you lie are, well, worthless. Sorry, but there is no easier way to put it. I considered one myself, but ended up getting an LM-1, LMA-2, and MAP sensor setup. This is unquestionably the best set of tools that I own. Yes, it's expensive. But, you'll know exactly what your carb is doing. You can make quantitative decisions based upon objective data on what to change. An AFR of 14.7:1 is what is know as the stoichiometric ratio (for gasoline), where all the fuel and all the oxygen content in the air of the combustion chamber will perfectly balance each other out during combustion. In the O2 sensor world, this corresponds to a lambda reading of 1. Lambda values greater than 1.0 indicate excess air and are called lean mixtures. Lambda values less than 1.0 indicate excess fuel for complete combustion, and are called rich mixtures. The aforementioned LED style A/F meters lead the User to believe they always want to run at 14.7:1, which is certainly not the case. For example, at WOT in a N/A application, an AFR of ~12-12.5:1 is ideal (this, of course, will vary by application). WOT at stoichiometric could prove damaging to an engine. Conversely, one could safely tune his/her carb to deliver a mixture of let's say 15:1 during cruise. A mixture this lean is perfectly safe when the engine load is low. With respect to dyno tuning, you are only tuning for WOT and maximum power. Yes, this is good, but off-idle bogs and other tuning issues (e.g., erratic fuel delivery at main circuit onset --> emulsion system) will never manifest themselves. A WB02 unit like the LM-1 can aid one in resolving drivability problems. The LM-1 was very useful in helping me rid my car of a part-throttle stumble. If you really want to dial your carb in, consider an LM-1. Split the cost between several friends and pass it around. That's what Heckeng and I did. Although I don't like the Quadrajets, just buying a Holley and sticking it on out of the box is not a guaranteed fix. In fact, I'd be willing to bet it will run pig rich in the stock tune. Not only does this waste fuel, but excessive amounts of fuel will actually reduce power output. The point is, ALL carbs need to be dialed in to YOUR application. What worked on your buddies car may or may not work on yours. With the WB02 setup, you'll be able to watch as you tailor you fuel curve exactly to your liking. Link to comment Share on other sites More sharing options...
Heckeng Posted September 23, 2006 Author Share Posted September 23, 2006 I disagree with the LM1 making a person want fuel injection! I want as few computerized things as possible on my Monte! Just a personal preference though. I used to feel very confident about my tuning by using seat of the pants, reading plugs, and adjusting jets and secondary springs where needed. After using the LM1, I realize that while the carb felt ok, there were lots of places in the rpm range, or load range where I was at non-optimum a/f. Luckily on mine, I was rich more than anything. Quarterbooty had some lean spikes that we were able to tune out of it. If a carburetor is sized properly, there will be far less tuning to do on it. If it is sized improperly, you can smooth out that problem by working with the bleeds somewhat. It is a real eye opener to actually be able to quantify your a/f numbers all through the range. Also, not all problems can be solved by main jet changes. I wish I had more advice to give with regards to the edelbrock style carb for you. Sorry Link to comment Share on other sites More sharing options...
wallaby Posted September 23, 2006 Share Posted September 23, 2006 Well that's what I was saying about the LED A/F meters. I guess they are accurate at that magic 14:1 number, but nowhere else. Once the ratio wanders away from 14:1 the meter pegs or bounces and you know it's off, but have no idea how much. I also discovered that the "magic 14:1 stoichiometric" that the gauge is focused to look at, is a place a properly tuned engine never goes unless it is transitioning to/from somewhere else. Idle mixtures will be rich. WOT mixtures are rich. Cruise mixtures are lean. My siuation right now is a carb that seems right at WOT, and pretty good at 70 mph cruise, but tips way lean with a 40mph cruise. I'm not sure I'm really understanding what's happening inside the carb that is different between 40 and 70; the vacuum is nearly the same and the throttle position is close to the same, so the big difference is engine rpm. Either way, the vacuum is high enough and the load on the engine is light that I'm nowhere near the enrichment circuit. Link to comment Share on other sites More sharing options...
Heckeng Posted September 24, 2006 Author Share Posted September 24, 2006 Throttle position will have alot to do with that lean spot too. At low throttle positions, you actually run on the idle circuit alot, I assume that your carb is similar to a holley in that respect. On holleys you have idle feed restrictors (idle jets) that you can change to change that condition. I may have to do some research on edelbrock style carbs and how you tune them. Sounds like a good project. Link to comment Share on other sites More sharing options...
Monte Posted September 24, 2006 Share Posted September 24, 2006 If you want my opinion on the lm-1 feel free to call me. If you dont have the number send me an e-mail. Monte Link to comment Share on other sites More sharing options...
Recommended Posts