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I just added the Innovative Motorsports DLG1 dual O2 sensor A/F meter to my 98 convertible today. This was an interesting project which took maybe 8-9 hours to complete at a very casual pace.
Most people would add an A/F ratio sensor to provide feedback to an EFI system. In my case, I'm just trying to tune a quadrajet/qjet as well as possible. O.k. so maybe I'm being a bit extreme here.
I had my exhaust shop weld in O2 sensor bungs into my 2.5" exhaust. There are no headers (On a 98?). I just have factory dual 2.25" system feeding into 2.5" pipes & resonators. The bungs are about 6" down the 2.5 pipe, which seems far enough to give good A/F ratio signals.
Other than the welding, the Innovative kit is about as hard a wiring a modern stereo system. Connections are switched power, ground, 02 sensor connections and an interconnect between the gauge and an auxiliary unit which permits software logging of the A/F ratio.
Early returns: The Stochiometric A/F ratio goal is 14.7. That's probably a bit lean for the real world. My idle is a maybe a tick rich at 14.1- 14.3 AF ratio. The real news is part throttle cruise was in the 15 - 16 AF range. Too lean. I'd never have discovered that with a vacuum gauge. I haven't done any WOT testing yet, but that fun is yet to come.
Long & short of it is, an interesting product @$300 giving useful data for qjet tuning. If I were trying to economize, I'd go for single sensor gauge. There's not all that much difference between the two banks exhaust outputs. Other single 02 sensor units run about $200.
I'm not affiliated with Innovative Motorsports and have no idea how long this thing will live, but on Day1, it's working as advertised. Fun mixing modern and old.
cf, the requirements for straight gas and 10% ethynol may be different. Beware of ideal numbers, they may not be what your engine wants. Call Cliff Ruggles if possible, he's an expert on qjet tuning. Got any pics of your 98 to post? Best of luck with your Olds.
FWIW I set cars (Qjets) up similar to how you mentioned it. Usually shoot for 14.2-15 @ idle, 15-16 light load cruise, 12.5ish WOT. Seems to work well & owners always happy after dial in. They usually pick up mpg, response & run their best #'s if checked @ track. It is a trial & error process with a Qjet & takes a few (or more) "top pops" to get it.
I’m new at this, but I know Ruggles book pretty well.
If 14.7 is the ideal air/fuel ratio, why is it a good idea to go 15-16 at part throttle cruise? Isn’t that too lean? Richer WOT, I get, but why not shoot for 14.7 at part throttle cruise as well?
Haven’t had time for WOT runs yet, but it’s not like I use my 98 for racing.
Just a quick update. The 98 convertible is running well, if just a tick rich at idle 14.1 AFR at 850 rpm. Part throttle cruise is running 15-16:1, WOT or heavy throttle in the 12:1 range. I still have some tuning to do, but the a/f gauge is really helping. It's like getting a new pair of glasses - suddenly everything is clearer.
Here's the latest recipe for 17058553 (late) qjet: 2 turns out at idle, only 1/2 turn out on APT screw. The primary side is 75 jets / 45 rods. The secondary side is a K hanger and CV secondary rods.
I'm not sure what % of ethanol NorCal gas is now or any other time of year. I'm leaving the car a bit rich on the theory that local fuel is not pure gasoline. Alcohol has a much lower stoichiometric ratio than gasoline so running it a bit rich may be a good idea.
When I still had the Q-Jet on my car I kept leaning out the APT screw. When I ran out of adjustment, I dropped a jet size, ran the APT screw full rich, and kept leaning it out until I got a lean misfire at highway speeds on a typical day. Once I found the lean misfire I richened up the mixture just enough to get rid of the miss.
I would average 16.5-18mpg cruising at 70-75mph. The first year I did Drag week I averaged around 13 pulling the required size U-Haul trailer. All my E-85 buddies with their 12 gallon fuel cells were filling up twice to my one. All this, and my 5 day average was 11:62, good enough for Quickest Olds. Try that with a Holley! 😎
Fast forward a year, a buddy gave me an old INNOVATE LM-1 AFR to play around with. When I put it on the car imagine my surprise to find the cruise AFR was 16:1, the idle was about 15. Full throttle was 12:6. I guarantee if I had the AFR first, I would have thought exactly as you did. I would have chickened out long before I found the sweet spot in the tune. I also guarantee the engine wouldn’t have gotten nearly as good as mileage, probably wouldn’t have run as smoothly, basically lived up to the Prius lover mentality that old cars are gross polluters and we hot-rodders are scum. While I’m not nearly naive enough to say my Olds doesn’t pollute the air, with attention to detail and some time and effort you can make the best of it.
To make a long story short, give the engine what it WANTS, not what you think it needs. Read the plugs, listen to the exhaust, pay attention to the way it runs. Don’t be afraid to experiment, you need to find the lean limit. Don’t worry about “melting pistons” 🙄, unless the engine is severely lean at WOT things will be fine.
I leaned it out a bit today to 73/49 with the APT at 3.5 turns out.
I’ve got the idle AFR just about 14.2, which about right and in gear fluctuates just under 14. Feels about right too. Cruise is about 15.5 AFR at 45-55 mph which feels about right. I think I’ll leave looks this for a bit and focus in on the secondaries which feel a bit lean at 12.5 AFR @ WOT. I was able to advance the timing a degree or 2 with no ping. So it was a good morning.
If cruise AFR is greater than 14.7, but not pinging, I get that the Fuel economy is better, but how can leaner than stoichiometric be not harmful to the engine?
This afternoon I’m helping a teenager learn about wheel changing and car detailing.
I have followed your folks discussion since resurrecting this thread because I enjoy this topic. I've used AFR (Lambda) tuners on motorcycles for years. I'm not a racer or a dragster. At 67 years of age, I merely want my tuner be established for the best tune I can achieve for a particular engine. Having installed both narrow-band tuners and wide-band tuners on numerous motorcycles both with carburetors and with ECM/EFI systems, I've found what best works for me. Sometimes (most of the time) the automatic tuners don't provide enough ability to fine-tune the three stages of the drive cycle: Cruise, Acceleration & WOT. I've found (depending on the engine and characteristics of the motorcycle) a manually configured EJT (Electronic Jet Kit) works best for me. I think every engine has its own inherit drive cycle. Of course the AFR is what you're reading, but it's really the Lambda which is of critical importance. Let's face it, stoichiometry is based upon ideals. I studied these ideals until I was blue in the face in far too many chemistry courses. In a perfect world of ideals, Lambda = AFR. Essentially, the left-side (reactants) of the equation are exactly the same as the right-side (products) of the equation (stoichiometric) - i.e. the perfect (ideal) thermite equation.
cf- A prolonged lean condition would be detrimental to the health of the engine.
I set up my current motorcycle (2010 Indian Chief Vintage 105cc engine [ECM/EFI]) based upon shift points: There are two shift points: one shift point between cruise & acceleration, and one shift point between acceleration and WOT. This particular engine has a tendency to vibrate upon deceleration between 1400RPM and 950RPM (cruise RPM is best @ ~2500RPM - 2750RPM; idle = 950RPM). While any modern ECM/EFI motorcycle (and vehicle for that matter) will have various PCM mappings available (which supposedly are best suited for your engine), no two engines ever operate identically and no two engines ever burn fuel based upon the same (ideal) AFR. It takes time to make adjustments with each model of narrow band/wide band tuner on each motorcycle/vehicle. In my particular case, with this particular engine, I enrich the cruise shift point to eliminate the vibration when decelerating. The engine is running a tad too lean during acceleration and when it has to decelerate to a stop (in a lean condition) the engine vibrates - so I enrich the mixture during the cruise portion of drive cycle. This may seem inconsequential to many, but consider riding mountainous switch-back (piggy-back) terrains with many, many winding hair-pin turns which require immediate deceleration followed my immediate acceleration - I'm decelerating often & ramping up quickly. Because this EJT provides for user/manual input, I can make adjustments (nearly on the fly). I do have to stop to make those adjustments, but they generally only require adjustment if consistently riding between 5,000' - 6,000' above sea level where AFR is far from 14.7. I generally achieve between 45.0 - 47.5mpg.
At any rate, I enjoy reading your discussions.
There is no such thing as 10% ETOH or E-85...it "could" be....and since there is none, there is no AFR of 10% ETOH or E-85
Took the car on a test and tune yesterday. For this 455 (for now) I’m settled in one the following settings for my late model (75 and up) 17057553 Quadra jet. Perhaps someday you chase these settings to help get your cards running well too.
73 49M primary jets and rods
APT set at 3.5 turns out
idle screws 2 turns out
float set at 9/32”
CV rods, M hanger
Idle AFR is just about bang on @13.8- 14.1. Cruise AFR is varying between 14.5 and 15.2 depending on speed and RPM. WOT AFR is around 10.5 - 11.5
The engine feels like it could use more timing advance and its running cool and smooth.
With our CA premium gas at 10% alcohol, I’m knowingly running it rich. I totally agree that running the AFR at 14.7 long term could damage the engine which I don’t want to do.
Buuuut. I spent a good chunk of yesterday poring over Cliffs High Performance site about qjets. Most guys over there seem have no problem with cruise AFR’s. >14.7. Even up to 16:1 or higher at cruise. I don’t think those posts are lies, but I’m having trouble understanding how these lean cruise AFR values won’t damage their engines. Or maybe I’m just worrying too much.
Can anyone enlighten me here? Their logic seems to be that the cruise load is so light/low that the lean mixture don’t hurt the engine and do help power/economy. If that is true, why not lean out idle AFR’s to those levels too?
Lambda does sound like the better way to tune, but I need to read up on the scale and adjust my thinking. The good part here is the Innovative 02 readout meter adjusts to that scale with one button press.
Seems to me that is probably the next chapter. But it’s a new language to learn.
I don’t know why a engine will run at a lean cruise just fine, but won’t idle. Maybe it has something to do with engine speed? Who knows? It is a good question.
I guess I needed to lean out my carbs long ago. But I'm getting there on the learning for tuning & timing. There are a huge number of possible combinations with qjets & HEI's. Many work fairly well. In my old work it's what we used to call a "large search space".
My 98 with the AFR gauge went well after the changes above and setting timing at an initial mechanical of 11 degrees (no vacuum) & total of about 30@3000 rpm. Any more than that with HEI & I get pinging at full throttle with our crappy 91 octane alcohol gas. I still think this timing a bit retarded for the 98, but don't know where to go next. I got more or less where I wanted to go with the idle AFR of 13.8 - 14.2, cruise AFR between 14.7 and 15.5 and WOT AFR north of 11.2. Feels about right, if a little under powered. I don't mind a nice running cruiser that's not max power.
The kick off for today was installing a Buick 350 (VC1838 Napa/ Echlin) vacuum canister in my Starfire's HEI distributor. This vacuum canistoer provides 10-12 distributor degrees of advance (20-24 crank degrees) at 7-9 HG of manifold vacuum. I replaced the adjustable Moroso vacuum can which never seemed to limit distributor advance quite enough to kill off the part throttle pinging.
For years I've kept turning back initial timing to stop the knock, but then the cars feel sluggish. I'm trying to go with more conservative vacuum advance cans on the idea that they will reduce part throttle pinging and I can increase initial and total timing. I had good success with this approach on my 98 using a Caddy 425 vacuum pot (Napa / Echlin VC1833), so I thought I'd try it on the Starfire too. I'm not sure these vacuum canisters are optimal, but they're better than the adjustable cans from what I can see & hear. It seems like the adjustable ones are built for cars with a whole lot more cam than mine so they were more or less misapplied to my smooth-cammed, heavy cruisers.
The '66 Starfire has a '70 455 with E heads. Nothing fancy with the heads or cam. It's pretty much a smooth old car with dual exhaust. It's run rich for years since I didn't want to burn valves. But it's been getting pretty poor mileage (sub-10 mpg around town and maybe 11 mpg on the freeway). So today I leaned out the carb in the today going from 74/43 rods & 15/64" float setting to 74/49K and 10/32" float setting. I don't usually lean out the mixture by 5 rod settings, but that setup did well by the '66 98 and I thought it might solve the Starfire's poor MPG results. The Starfire carb is an '78 800 cfm qjet redone by SMI in 2012, so it's seen a few miles, but isn't worn or sloppy.
Here's the Starfire carb set up in case it helps you: 74/49K primary jets/rods; float set @ 10/32"; APT is 4.5 turns out; idle screws 4.5 turns out (I'd rather they were closer to 2 or 3, but AFR was 13.9-14.2 i.e. on the money with those turns). I'm still working on cruise AFR but it's running 15.5 to 16 at part throttle (55-60 mph) which is just a bit lean to me. Those AFR values are with the APT at 4 turns out, not 4.5. The secondaries are maybe a little lean with CK rods & K hanger. I lightened up the secondary wrap spring to be just about 25 minutes past the hour as compared to previous (tighter) 30 minutes past the hour. That seemed to help response. At WOT the AFR drops to 11.8 or so, then recovers as the secondary vacuum doors open and provide more air. I think I can go a bit richer here, probably starting with a M or P hanger and keep the rods the same.
The Starfire changes worked pretty well, but I did the carb & timing changes all at once. So I can't tell which changes made the big difference. Just to keep things fun, this is the Starfire that I converted to OAI a while back. I still haven't tested the effects of the OAI change, but I'm hoping to do a little road trip tomorrow. I'm hoping to see 13-14 mpg on a fairly gentle highway run.
Hope it's not too much detail and that if you've gotten this far, I hope my test results guide or help you in some way.
Having said all that, can any of you clue me in on the theory behind the idea that cruise AFR's from 15.5 - 16 are o.k., where they are not o.k. at idle? If these values are bad for a car at idle, why wouldn't they be bad for a car at part throttle cruise where demand/load is greater?
This still doesn't make sense to me as a theory, but I can see where it's working fine in practice.
I'm uncomfortable when tactics work, but I don't understand the theory. Guidance much appreciated.
I've heard the lean cruise works because Q-jets atomize fuel extremely well, and the engine is barely making any power at low throttle positions, so it really can't hurt itself. My H/O has legit 10.6:1 compression, iron heads, medium sized cam, and it cruises fine around town at over 15:1 AFR. The factory carb cruised at 13:1 and it ran pig rich.
I don't know that lean idle will catastrophically damage an engine, but mine definitely doesn't like idling that lean, it will start misfiring in gear (has 11 in-hg of vacuum in gear at idle). It's happiest around 13.8-14:1 or richer on the wideband gauge. I'm guessing it mostly has to do with engine speed and the charge air speed going into the cylinder.
Most data references "ideal" conditions - which ideally are seldom achieved. There are several other variables which must be addressed relative to ideal AFR for a SI (Spark Ignition) system. Three important considerations are: (1) RPM, (2) Torque & (3) Heat. The burning of various types of fuels is a simple oxidation reaction. The "efficiency" of this oxidation reaction is certainly related to the ability to atomize fuel as suggested by Luke. Below (link) provides some excellent examples and graphs depicting AFR @ various torque & RPM ranges.
Note in particular how for any given RPM, as torque increases AFR decreases and conversely the inverse relationship. A simple illustration (I suppose) is to imagine (or perform) the following situation. At idle, with foot firmly on brake, increase engine RPM. Torque value increases. AFR decreases relative to RPM in this scenario. The efficiency of the oxidation Rxn diminishes as the result of incomplete oxidation - fuel is expended and inefficiently expired as a result. As you let off the brake, the oxidation Rxn becomes more efficient and AFR decreases.
December 5th, 2017, 08:22 PM
