What the hell is tuning via EGT vs, wide band/ narrow band

[Indecisive]

[span style=\'color:red\']Posted by Magnum[/span]

There seems to be a lot of mystery and misinformation about using exhaust gas temperatures to tune engines. Claims by many EGT gauge manufacturers about it being the best way to tune an engine must be qualified. The BEST way to tune an engine is on an engine dyno- PERIOD. What EGT is good for is a reference for where the engine made maximum torque at wide open throttle. Once removed from the dyno, a similar air/fuel ratio can be established at a later date by dialing in the mixture to achieve the target EGT. It is really the AFR that is important, not the EGT. Most engines will make maximum power at an AFR of between 11.8 and 13 to 1 however, the EGT may vary from 1250F to 1800F and is dependent on many factors.

It should be mentioned that the target EGT is valid only on the same engine configuration as was used on the dyno. If you change the ignition timing, cams, pistons, headers etc., the optimum EGT may also change. Raising the compression ratio with no other changes will drop the EGT at the same AFR. Retarding the ignition timing will generally raise the EGT at the same AFR. One engine might make best power at 1350 degrees while a very similar engine might be happier at 1500. You can\'t guess at this or you are simply wasting your money on the instrumentation. Wankel engines have higher EGTs than comparable piston engines due to their lower thermal efficiencies. 1800F is not uncommon here.

Some gauge manufacturers say you should tune to achieve maximum or peak EGT for maximum performance. This is incorrect. Peak EGT generally occurs at an AFR of around 14.7- 15.0 to 1 on gasoline. This is far too lean for maximum power and is dangerous under continuous WOT conditions. Many people think that the leaner you go, the higher the EGT gets. This is also incorrect. Peak EGT occurs at stoichiometry- about 15 to 1 for our purposes. If you go richer than 15 to 1, EGT will drop and if you go leaner than 15 to 1 EGT will ALSO drop. It is VERY important to know which side of peak EGT you are on before making adjustments. It is safe to say that peak power will occur at an EGT somewhat colder than peak EGT.

You can sometimes feel a lean of peak condition as the mixture is hard to ignite and power will be down a bit as well. Once the AFR gets close to 17 to 1 at WOT, generally the engine will start to lean misfire. Most tuners always recommend to begin jetting or programming from a known very rich initial setting and carefully leaning until torque falls off slightly, then going back richer to the point of max torque. Note the EGT at this setting. Be aware that altitude, barometric pressure and ambient air temperature may affect this optimal temperature to some degree.

Are EGT gauges better than AFR meters? Conventional narrow band oxygen sensors and digital LED meters are not the best devices to measure AFR in the richer ranges but they certainly warn of a too lean condition immediately and obviously, without translation by the driver and they are affordable. Meters combined with wide band sensors are supposed to be highly accurate and everyone has jumped on the bandwagon with these lately. Unfortunately the naive and impressionable often don\'t question the accuracy of these devices. We have seen some dyno plots indicating best power was achieved at AFRs of 9.7 to 1 on gasoline. This is PHYSICALLY AND CHEMICALLY IMPOSSIBLE and shows that either the sensor was bad (leaded fuel used possibly) or the meter was not calibrated properly. Again, the wide band sensors have the same limitations as the narrow band- leaded race gas quickly fouls them.

We recently dynoed a shop road racing Celica on a DynoJet equipped with a wide band meter. The meter was saying that the engine was going super lean (17 to 1) at high rpm so we kept upping the fuel there. The engine lost more and more power as we added fuel. The dyno operator was convinced that the meter was right but logic told us with no serious dip in power on the curve and the fact that the engine was still alive that the meter was not correct. We started leaning the engine down more and the engine started gaining power. Finally, when confronted with this information, the operator checked the water trap for the wide band sensor. Once this was emptied, the AFRs looked reasonable again. We didn\'t need the wide band to tell us this, only the torque curve from the dyno.

We have heard of several other instances with people using wide bands getting erroneous readings and tuning their SDS based on these readings. Then they phone us saying that the system is crap. Look at the dyno curve, when the engine makes its best power at a given rpm, that\'s where it likes the AFR irregardless of what other instrumentation is telling you. Remember, a bad sensor whether O2 or EGT equals bad information. When the engine sounds crisp and makes great power, you\'re there.

I would suggest that mixture meters and EGT gauges are complimentary. EGT gauges have the advantage of working long term with leaded fuel which will clog oxygen sensors. EGT gauges are widely used to set mixture on engines used for steady state high power applications where operation has been carefully documented such as in aircraft. The choice would depend on the application. Both are better if you can afford them.

[RPSport-John]

Depending on the 02 metering that you are using two wire, five wire, and seven wire 02/Lambda meters all give different reading, especially depending on how they are calibrated. 14.7 is not a universal stoicmetric point on all equipment, it is largely up to the manufacturer to dicatate stoicmetric point based on the calibration of the device and what it is looking for.

John

BTW, YOU SHOULD DEFFINATELY HAVE AN EGT AND AT LEAST A LOGGABLE 5 WIRE LAMBDA.  Many times you\'re lamda can log, RPM and egt, if you\'re guage has an output.  The largest problem with egt is it goes hot if you are too lean, and it goes hot if you are too rich. Based on the dynamics of you\'re Compression ratio after boost, and rated stregnth of you\'re internals, you should know what you\'re maximum EGT is.  I use the Lambda to tune a good a/f then concervatively add timing while monitoring the vehicles output (HP/TOURQE/RPM) against egt. When one falls short of the other, you step back and touch up fuel boost or spark to correct the pitfall.

[Mr.200]

EGT tuning is a bad thing to get into. Sad fact is most people don\'t understand the readings well enough to use them.

Yes, running lean will raise EGT. Great, luverly ... fancy. Detonation will cause temps to drop. What? Yes ... yes indeedy.

The difference between O2 sensors is *gasp* the width of the \"band\"

O2 sensors use an electrical signal to translate oxygen content in your exhaust for the ECU. The difference between \"narrow band\" and \"wide band\" is how accurate the gauge is.

For ease of explaining it, think of it this way (not real 02 values just an example)

A standard O2 sensor, let\'s say can send a signal of 0-50, whole numbers only in increments of 5.

So if your exhaust is actually at a 22.545, the standard 02 sensor can only give a value of 25 to the ECU.

The wider the 02 sensor\'s \"band\" is, the more accurate the readings are.

Dyno tuning is somewhat overrated IMHO. You can spend hours to find 3 hp.

Engine power is reliant on too many factors to be able to recreate a \"perfect\" test scenario.

Air pressure, air temperature, oil temperature, engine temperature, oil viscosity, planetary alignment etc can all affect performance.

I tune seat of the pants, then 1/4 mile, then, for posterity and baselining, one dyno day. Then, if something seems off, you can actually use a dyno to find real horsepower.

Just FYI, any dyno shop that\'s worth going to will use a wideband sensor to get accurate readings.

You can buy DIY wideband kits too.

[Alex Frost]

Matt hit the nail on the head, for another article look at the sticky in the CA18 section...

[RPSport-John]

i thought all dyno\'s were crap untill I used a mustang dyno. Mustang dyno\'s are the best.  Especially when tuning a duty cycle reliant boost controller, the induced drag is pinpoint real to life on the mustang dyno.

Hp/Tourqe figures are overated, though what many \"tuners\" are looking for. I tune for long useable powerbands while keeping the vehicles electronics and hardparts withing feasable range of usage (stuff not blowing up).

The problem with dynos is their induced drag can often times be very unrealastic. This is becasue many dynos only offer one \"drag\" speed or setting over all roller speeds. The mustang dyno comes pre programed with an adujusting algorythm drag, user programable broad spectrum correction, or point by point corection.

Also keep in mind dyno tricks that MANY shops will play, vehicle heat, the abcence of a fan, and adjusting drag of the rollers, and adjusting the \"weight\" settings of the rollers will give way different output #\'s.

You bring the car into the shop, Hot like 92C hot. They roll it right onto the dyno, it makes 173 hp.

Then they \"TUNE IT\" with an intake. Only this time they lesten the drag and weight of the roller, get the engine down to 45c, put a fan against the car and spray down the intercooler with an open bottle of N2o or co2, you\'re choice.

Now you\'re car just made 202 hp from the intake. Right? AEM is KNOWN for doing this with their \"TEST\" products. Most evident of this is the abcence of low end tourqe and HP on the initial dyno graph. Because most motors loose eficency when very hot, they do not make alot of power down low when hot.  You\'ve probably notice this for you\'re self when driving you\'re car semi-cold against very hot (like an hour of traffic hot).

Especially with an avc-r alot of dyno\'s will wreak havoc on this boost controller. It control of boost will be extrememly iradic and spikey when on the dyno. IF you tune it on the dyno to stabalize it, when the car is on the street the avc-r will do the same thing.

Please ask you\'re tuner if they have experience with the avc-r in you\'re aplication, and if they have a mustang dyno.

John

[frosti108]

good reading material!  

about the celica going to 17:1 at high rpms... could this be a leaky turbo flange?

im getting crazy spikey AFRs like that, i mean totally unrealistic ones around 19 and 22 even. someone suggested to check the turbo to downpipe flange...

?

[Arro]

yes this is one of the few gems remaining from the old days, this thread.

Prolly best to ask your question in it's own thread tho, I don't want anything but generic fuel tuning and gauges discussions here, not troubleshooting specific cars. We have too many post whores and I'll end up deleting and possibly locking this thread, which I really really don't want to do.

[mcfizzle]

Some decent info in here, and a few mistruths.

IMO, here are the "facts:"

- A wideband gas analyzer and a dyno is the best way to tune a car. Period.
- EGT works as a great supplement while using a wideband.

As for regular pre-cat O2's, here is how they work:

Oxygen readings both inside and outside the exhaust are sensed by a piece of quartz, which generates voltage pulses between .1V and 1.0V. A stoichiometric air-fuel mixture will cause the O2's voltage signal to toggle between roughly .25V and .7V at idle (I'm not 100% sure on those numbers, but they are close). They are built only as a data source for a car's ECU to determine fuel trim, and are not suitable for tuning.

[Arro]

Magnum's post (as reposted by Indy) was actually a more expanded (and a bit complex) version of my own, where I provided actual options and scenarios.

But after a recent discussion in another thread, I made some comments that simplify things, and also address the post directly preceding this one.

Shop dyno tuning is highly effective. That said, having someone do all the work.... it reminds me of people who pay a tuning shop to basically do the work (and the thinking) for you. If that's ok by you, then it's a great choice. But if anyone's gonna modify my circuitboards, it's gonna be me... or nobody. And I'd rather use workarounds that I fully-understand and have complete control over personally.

As far as manually-configured workarounds go.... If it usually leads to fucked up parts, it's usually because the person tuning is impatient and ignorant of basic fuel stoichiometry. FYI long before there were dataloggers and even before there were narrow-band O2 meters, there was plug reading, and it worked for many a patient, determined tuner.

That said, this is also why I laugh when people talk such mad shit about narrow-band 02 meters for tuning, and end up spending two or three times as much for some wideband meter kit. I know two different turbocar communities that rely almost completely on either a narrow-band 02 meter or on EGT's and some of those cars are more than mildly tuned. One would argue that a narrow-band meter does not have the resolution needed for tuning, but I know a company that makes a narrow-band meter that only has five lights because they know very well that if you're any richer than that, you're doing something wrong... and any leaner than that, and your engine is blown. I also know people who argue that EGT gauges are too slow, but then again I know people who would say if you are making such drastic changes to fuel that you can't monitor the slight increase or decrease of EGT's between tuning runs, then you're recklessly tuning.

So mistakes are less about the tools you use, and more about the most important tool -- your brain. You can employ the most sophisticated ECU management toys, but what good is it if all you're doing is using half (or less?) of the sensor options for it, and understand only half (or less?) of those as it is? In some respects, it's even easier to blow your shit up if you change numbers in a computer database field too aggressively and upload it to your aftermarket EMS. The EMS will do whatever YOU tell it to.

So, like I said, your choice of tuning tools should be based upon what is easiest for the individual... to understand, to install, to maintain, and ultimately... to tune. There is no "best" solution. Price and sophistication is not the measuring stick, but your own skillset is.

So if someone thinks he wants to play with lots of extra sensor inputs, custom fuel maps, lots more custom wiring than his OEM KA or SR spliced-in harness, and the risk of the ease of over or undercalculating... then he should do it.

Or he might find it more effective *for him* to employ more direct means, use his wits and patience and human skills, and rely less on automation and more on himself.

Neither is wrong or right in of themselves.

My only advice in this situation is before you plunk down a chunk of major change on some all-in-one aftermarket solution, learn about the workarounds, and see what you think after exploring a few alternatives.

Final thoughts: The original article was called "What the Hell Is.... Baselining?" I will have to recreate it at some point in the near future.