lean burn rules~!

[ECONORAM]

Originally Posted by JohnnyGrey

Modulating the injectors in this fashion probably won't give you consistant results. They're "on/off" devices, so by supplying low voltages, the cylinder to cylinder spray pattern and volume could vary considerably. As long as your car is in closed loop mode, there's no point in attempting mods like this since the ECU will compensate as far as it will go, then throw a CEL fit.

Your narrowband sensor is a poor indicator of AFR. Treat it like a digital signal, where >0.45v is rich and <.45v is lean. What actual voltage you get will vary with each sensor, exhaust temperature, ECU bias voltage etc, so there's no real way to know. Plus, if the voltage stayed at .24 for long, that's probably the voltage floor of the signal. It indicates a lean mixture, but there's no way to say how lean you were running.

A wideband lets you do so much more. Mine is made by Bosch and the driving unit is made by AEM. It puts out 0-5v which represents linearly ratios from 11:0.1 to 18:0.1. The driving unit also has a narrowband emulation mode that does switch back and forth over that .45v point at 14:7.1. This is fine if you want to run at that ratio, but we don't.

So we need a box that puts out either 0v or 1v depending on whether or not that 0-5v wideband signal has crossed a certain threshold. If the switch point is set at 4v, the motor will run quite lean (around 16:1), but the ECU will believe it's running at a steady 14.7:1 and will not throw a CEL. Also, it will be training itself around that ratio, and will hold it steadier than you could in open loop mode.

With a narrowband sensor, you're working blindfolded. The hot rod guys prefer to tune with widebands, but in a pinch, they can tune with a narrowband. Their only concern is running rich so nothing blows up, so as long as the O2 reads high and the engine sounds happy, everything is fine. For economy though, you need tight control over the AFR.

As to whether or not the ECU in your truck is programmable, I would say not for closed loop operation, and we're not interested in the open loop tables, they're for WOT operation. Also, I doubt Ford would implement a lean burn system since it is not emissions legal. I have no idea how Honda got away with it in the HX/VX.

It is technically possible for an ECU to run a lean burn on an engine equipped only with a narrowband sensor. In fact, that's exactly what GM does on cars it sells outside the US. That narrowband sensor is only good for switching around 14.7:1, so the ECU establishes fuel tables for that mixture. Once you get on the highway, the ECU goes into lean burn mode, which is actually open loop. Since the ECU already has a well-established fuel table that produces mixtures very close to 14.7:1, it can scale that table to produce whatever fuel mixture it needs. For example, 92% to run at 16:1. Because the narrowband sensor will read consistantly lean, the ECU occasionally wanders back to 14.7:1 to confirm that its tables are correct, then goes back into lean burn mode. On US ECUs, the mode is disabled.

Odd. I was thinking about this today, wondering if I could either trick my ECU into thinking it was at 14.7 when it was really at 16, or if I could run open loop at cruise, and reset the fuel tables to produce a 16:1 ratio? Maybe my PSC-1 could do it... From what I read here, and in other forums, a wide-band is pretty much a necessity.

[Joseph Davis]

No, a wideband isn't needed for daily operation. Only for the initial tune on the vehicle. Narrowband O2's are actually very accurate away from stoich; but their curve is logarithmic, a low amplitude analog signal prone to being molested by ground ofsets, and their calibration varies with sensor temperature. Run a heated four wire sensor a little ways down the exhaust stream so engine heat doesn't molest it - approx where the driver's feet are on a distributor Honda is fine - and make sure you keep the sensor's power and signal grounds seperate until they finally reach the block which is THE ground point in a car's electrical system. Chassis grounds are garbage.

I've been doing a mini engine R&D project with a friend, putting the 01-05 D17 cranks into earlier D16 engines. There's a lot of misinformation about the reliability of this combo resulting in few people doing this combo - it's mostly kids who don't know how to build an engine messing things up.

Anyway, 9:1 static CR 1.7 stroked D16Z6 1991 RT4WD wagon with an Evo8 turbo and Siemens Deka 500cc (at 43.5 psi, aka 04-05 SRT-4 injectors). Part throttle maps were tuned for 15.5-16:1 AFRs, and runs a (fresh!) stock O2 sensor whose lean/rich switch point has been set to 0.39 volts. The combo makes 185 whp at 7.5 psi and 235 whp at 12.5 psi, uncorrected figures. In 4WD, some spirited driving, 32 mpg. In 2WD, normal driving, 43-44mpg. Wagons are heavy and aerodynamic bricks, 4WD/AWD drivetrain loss is appreciable, and the air is thin as well as the land not flat up here on the mountain.

A third of the gains are tuning the vehicle. A third of the gains are having a working O2 sensor with a lowered switch point. A third of the gains are having a modern pencil core injector that atomizes far far better than earlier injectors. I've also spent a number of hours on the dyno placing the ignition event at the optimum point for all NA loads and speeds under 4000 rpms, as lean burn doesn't accomplish as much if the ignition timing doesn't place peak combustion pressure accurately at the "sweet spot" where the rod has best mechanical leverage against the crank.

[99kleansi]

Originally Posted by Joseph Davis

No, a wideband isn't needed for daily operation. Only for the initial tune on the vehicle. Narrowband O2's are actually very accurate away from stoich; but their curve is logarithmic, a low amplitude analog signal prone to being molested by ground ofsets, and their calibration varies with sensor temperature. Run a heated four wire sensor a little ways down the exhaust stream so engine heat doesn't molest it - approx where the driver's feet are on a distributor Honda is fine - and make sure you keep the sensor's power and signal grounds seperate until they finally reach the block which is THE ground point in a car's electrical system. Chassis grounds are garbage.

I've been doing a mini engine R&D project with a friend, putting the 01-05 D17 cranks into earlier D16 engines. There's a lot of misinformation about the reliability of this combo resulting in few people doing this combo - it's mostly kids who don't know how to build an engine messing things up.

Anyway, 9:1 static CR 1.7 stroked D16Z6 1991 RT4WD wagon with an Evo8 turbo and Siemens Deka 500cc (at 43.5 psi, aka 04-05 SRT-4 injectors). Part throttle maps were tuned for 15.5-16:1 AFRs, and runs a (fresh!) stock O2 sensor whose lean/rich switch point has been set to 0.39 volts. The combo makes 185 whp at 7.5 psi and 235 whp at 12.5 psi, uncorrected figures. In 4WD, some spirited driving, 32 mpg. In 2WD, normal driving, 43-44mpg. Wagons are heavy and aerodynamic bricks, 4WD/AWD drivetrain loss is appreciable, and the air is thin as well as the land not flat up here on the mountain.

A third of the gains are tuning the vehicle. A third of the gains are having a working O2 sensor with a lowered switch point. A third of the gains are having a modern pencil core injector that atomizes far far better than earlier injectors. I've also spent a number of hours on the dyno placing the ignition event at the optimum point for all NA loads and speeds under 4000 rpms, as lean burn doesn't accomplish as much if the ignition timing doesn't place peak combustion pressure accurately at the "sweet spot" where the rod has best mechanical leverage against the crank.

This is about the most sense I have head on this site. What injectors are you using? Injector dynamics are very good and are all balanced within 5% of each other in any given set.

Are you tuning each individual cylinder according to EGTs or for overall advantage. The ID injectors will make this real simple as the RC injector in the past were not as linear. The IDs also work real well at high pressure around 100PSI to def atomize the fuel.

I am under the impression that no motor actually runs @ 14.7:1 as that would be unrealistic. I would assume you could get around 15:1 or 16:1 with almost no load on the engine. Throttle tip in would reduce the ignition in milli seconds and allow the injectors to richen the mixture to allow for acceleration with more timing.

In some programs on the Hondas you can allow the dwell angle in the distributor to accumulate more spark energy in the coil to help a more efficient burn with out having to fork out for an ignition system that would allow more sparks over a certain amount of degrees of rotation.

[Joseph Davis]

Originally Posted by 99kleansi

This is about the most sense I have head on this site. What injectors are you using? Injector dynamics are very good and are all balanced within 5% of each other in any given set.

Injector Dynamics 1000 and FIC 900 are Bosch injectors modified to 880cc. As stated before, I am using the black/blue tip Siemens Deka cores used on the 04-05 SRT-4.

Flow balance, as it has been marketed to you, is only important with aftermarket modified cores. Most of these cores flow a certain amount in a raw fashion, and are then restricted by one or more precisely manufactured tips that are crimped or seam welded in place. These aftermarket modified units are flow match at 3% duty in the 2000-4000 rpm range, and again at 85% duty, for the sole purpose of good idle characteristics.

A 5% discrepancy at idle in an OEM injector of the last decade would likely not pass emissions. Most of these modified pencil cores would be unacceptable to any OEM in the last decade.

Originally Posted by 99kleansi

Are you tuning each individual cylinder according to EGTs or for overall advantage.

EGTs are for determining if there is a mechanical problem with the engine. The only time I'd do that are SBF in the 1400+ whp range as they have heat issues and are prone to thermal imbalance, despite which people still love them and insist on building them, so that's what you do. None of which has anything to do with a mild 200whp per liter street car, or for part throttle fuel efficiency.

Individual cylinder fuel and ignition trims, however, are vital for any performance tune. Those are best based off of the nature and condition of the carbon coat on top of the piston, and EGTs would not correctly reflect this. EGTs express the heat any one cylinder sheds, and not the heat that is absorbed and dealt with by any one cylinder. Much like octane, EGTs are not what people think.

All of this is entirely outside the realm of a FE tune, which would not require individual cylinder trims or temperature monitoring. Such things are largely a waste of time on a car like that. A highway cruise requires 12-18whp. Not to be hurtfully sarcastic, but oh no such power can hardly be contained?

Originally Posted by 99kleansi

The ID injectors will make this real simple as the RC injector in the past were not as linear. The IDs also work real well at high pressure around 100PSI to def atomize the fuel.

You're talking about a huge power turbo car injector? 1000cc/min at 43.5 psi comes out as a stream and not a mist, at 100 psi and commeasurate increase in flow the bottom line atomization isn't significantly better. Not enough to make a FE related post in a FE forum about it, although the performance guys might like to hear that they have perks past smooth idle and big flow at big pressure.

For a 300-350 whp street car, I'll stick to the smaller pencil cores. Everything about them is better with regard to flow balance (irrelevant at the present technology level, unless you are an OEM appeasing the EPA/DOT) and especially FE.

Originally Posted by 99kleansi

I am under the impression that no motor actually runs @ 14.7:1 as that would be unrealistic. I would assume you could get around 15:1 or 16:1 with almost no load on the engine.

Depending on the motor configuration, and injector atomization, 15.8-17.4:1 indicated AFRs is the tip over point where combustion pressures fall off. I ran an old D15B7 around at 16:1 part throttle and 13.9-14.2:1 WOT, you could feel the O2 sensor switch point at cruise as a slight surge. With the 12.5:1 D16Y5 I was in the 17's at a cruise and 13.0's WOT and it got much better efficiency due to quench/etc, despite the sportier gearing, with no closed loop surge, as well as better mpgs at all loads and speeds while making twice the power.

Originally Posted by 99kleansi

In some programs on the Hondas you can allow the dwell angle in the distributor to accumulate more spark energy in the coil to help a more efficient burn with out having to fork out for an ignition system that would allow more sparks over a certain amount of degrees of rotation.

No, it doesn't work that way. I was the guy with the oscilloscope who tested that for eCtune, it was never correctly implemented. With 13.75-14.25 volts available you can only charge any given coil so much. Any particular design coil's inductive reactance, however, will require a different charge time at any given frequency (rpm) than another design coil will. That table is there to add a little bit more dwell to MSD Blaster2/SS coils in the 3000-6000 rpm range so that they function as well as a fresh OEM coil does - and due to the confusion I've passively advocated removing that table. There's no free lunch, at the end of the day performance cars need an ignition amplifier to get the job done. Conventional spark ignitions are very crude, and either the air/fuel mix lights or it doesn't. For low power FE setups, not worth thinking about.

Also, you want one spark, precisely timed, not multiple ones. That's another advertising campaign, thanks a bunch MSD.

[steffen707]

Originally Posted by Joseph Davis

That's interesting.

Not all vehicles run correctly with O2 sensor unplugged; some ECU interpret this as a full lean condition (0 volts on the O2 signal line) and start dumping in fuel. Poor mpg and trailerhitching @ cruise are the usual symptoms.

I heard running the car without the O2 hooked up is very bad for the O2. I heard that since it is suppose to be heated by its heater ciurcuit, when its unplugged, its not getting this, and the hot exhaust gases can ruin it.

Maybe this is wrong, but i'd read up on this before continuing to do that.

[Joseph Davis]

Originally Posted by steffen707

I heard running the car without the O2 hooked up is very bad for the O2. I heard that since it is suppose to be heated by its heater ciurcuit, when its unplugged, its not getting this, and the hot exhaust gases can ruin it.

Maybe this is wrong, but i'd read up on this before continuing to do that.

Where do you get that I'm doing anything of the sort?

[steffen707]

Originally Posted by Joseph Davis

Where do you get that I'm doing anything of the sort?

Right from this sentence in the post I quoted from you.

"Not all vehicles run correctly with O2 sensor unplugged"

That would lead me to believe you are running the car without the O2 hooked up. Maybe you took the O2 completely off the exhaust system and put a plug in the O2 bung.

[Joseph Davis]

So by not all, I have more than one vehicle I'm intentionally driving around with the O2 sensor unplugged? Would this number of vehicles be greater than two or less than four hundred?

FYI, I dyno tune cars for a living, been reverse engineering ECUs for a decade and running various shop's dynos for half that. When I make a broad statement like that it's a titdbit of technical information.

[Joseph Davis]

Actually, since the last few posts in this thread have been 50% me and I display quite a large amount of knowledge on the subject, you're either a troll or dumb.

#1 reason I don't post much to forums anymore. You don't help anyone by doing so. Anyone capable of understanding can usually figure 95% of it out by themselves, and they find you via email/etc to ask for a tip or to exchange info.

[steffen707]

Originally Posted by Joseph Davis

Actually, since the last few posts in this thread have been 50% me and I display quite a large amount of knowledge on the subject, you're either a troll or dumb.

#1 reason I don't post much to forums anymore. You don't help anyone by doing so. Anyone capable of understanding can usually figure 95% of it out by themselves, and they find you via email/etc to ask for a tip or to exchange info.

Look JOEY, some people read these forums for information. Some people may have read your original post about running a car with the O2 unplugged and thought it would be okay to do so.

I wasn't knocking on your knowledge as I don't know you. Nor do I know how many cars you have, nor was I being smartass or a troll as you put it.

Stop being a Dbag and realize that I was trying to help the "ecomodder" community by informing people its not good to run the car with the O2 installed in the exhaust, and not wired up properly.

#1 reason I don't like posting much to forums anymore is because of A-Holes like you bashing what people say, instead of thinking where people are coming from when they post things. You don't want Jonny-knows-very-little to read your post go home and unplug his $400 L1H1 O2 sensor, break it then come *****ing to you because he thought you said it was okay.