He didn't say Loren posted it first....and Loren did post it....so, I would say yes, you are wrong.

Scott

thanks Dub-OH.. Of course your are right. --no need to be shy about that. I've been avoiding this the tread. and so clicking on "go to last unread" button skipped me ahead. ...where I had also missed Mr9146 nailing it.
As did Bugermeister with that's as far back as I dare go. ;) ... it's good to see there are still some experienced critical thinkers who still post here in crazy threads like this.

The above graph, originally published by Bosch illustrates exactly what the majority knowledgeable engine builders and tuners have known for years, and debunks what the OP keeps preaching throughout this entire thread. Let us examine the above chart more closely. See below:


http://forums.pelicanparts.com/uploa...1340319629.gif

Without getting into the debate as to what is the more optimal AFR for max power (even though the chart seems to show the peak of 100% at ~13.0:1), according to the above chart a one or two point deviation from the ideal represents a 4 to 8% reduction in power. A 2 point variation from 12.6:1 is 14.6:1 and from the above chart that is only 92% of max power. A 1.6 point variation the other way to 11.0 also is at 92%. Whether 92% is good enough is up to you. 92% out of a 250 hp motor is only 230 HP. A lap time that is only 92% of what could be a stellar lap time of 1 minute 30 seconds is 1:48. For many of us for which won't accept less than 100% perfection, 92% is not good enough. Of course there are some like the OP for which less than perfect is acceptable, however that opinion should be left to the individual and not pounded to the masses as if it were gospel.

Bottom line:

Just rx'd a stock-programmed chip for my '89. I've been running with the PO's autothority chip for these years,...the car runs really well,..extremely responsive in the mid-range throttle,..may ALL be timing -related/AFR's, etc. Inanycase, I DO plan to install this stock chip soon,...then have the long-running ship read out for me to quantify all movements in programming....no need for a dyno, for me. Fact is, this modification process is "results-driven",..as many dyno runs have shown, both here in this NG and others. As a Recording Engineer, I don't spend much time with Dynos and such,..but certainly see (as a fellow Engineer), the resultant data from chip (S/W=software) modifications as being significant,....as to dyno results.

the question becomes (for me): at what cost? Over time? Seems to become (not just Porsche Engineering) but tolerances for the "mechanical side".....(what they can handle, of course,"over time").....I've just not seen data relating to this "piece" that's alledged to "be left on the table, by Porsche" AS RELATED TO WHAT HE HARDWARE CAN HANDLE,..wth advanced ingnition, in example.

Isn't this the real question? How they hey would one go about gathering the data on the P/C's, heads,.etc. with the resultant mods "loads"? I've often wondered this,.....they ARE what they are.....

My car is unbelievably responsive, at present. I really can't wait to see what happens when I load this STOCK chip,..I know, it may seem "backward" for some, but I (personally) wanna' know,..and I sure as hell wouldn't want to gain a few horsepower, even mid-range stuff, at ANY expense of putting the motor in strained relations,..due to specs....I've NO idea WHAT margins were used in Porsche engine development (especially for gas, at that time-89),..not a clue......

A conclusion I have drawn is that it seems a bit chancy to advance any ignition timing WITHOUT any knock-sensing capabilities......the "margin" may exist (a given),..but, what it "it"...? Exactly?

So goes my reservations........at least: caution.

NO,...I've heard of NO engines BLOWING up from Wong's stuff...this speaks volumes to me, at least for the time they've been installed.....Clearly, strong statement. I've had conversation with Steve,...and he impresses me as a knowleadgeable individual,..no question.

So goes my experiment,..the APE chip (6 years running) will be sent off for analysis and print-out (ignition maps, fuel maps, etc.),...I'm quite interested to see the differences from STOCK,..."feel" will be interesting, to boot.

Here goes,....


BEST,

Doyle

It's most definitely NOT a bogus chart. If you disagree with what it shows, so be it.

Although I'm new here (and the air-cooled Porsches in general), it's not my nature to post "bogus" stuff. I'm also an engineer in the automotive industry and have tuned several of my own turbo cars and have raced them with success.

Perhaps I'm being too sensitive....but I dislike being accused that I'm posting "bogus" stuff.

As Mr. Wong stated, that is indeed a real graph from an industry-related textbook.

Both winders and lorenb have been known to ruffle some feathers at times so I wouldn't worry about it.

LOL, just LOL.

Scott, so now you know more than Bosch and its 100's of engineers and experts because of a few dyno runs ? They basically invented modern (post 1970) fuel delivery and engine management.

NICE!!

FYI - Bosch will "lose" more information than you will ever know on this subject. They did more dyno runs in a single year than you will do in a lifetime. Just the facts Scott.

Even Wong says the graph says what it should, and supports his position... he agrees with the graph.

LOL, just LOL.

I have another chart somewhere showing the effect of changing the AFR and what result it has on EGTs.....

Not sure I should even bother looking for it?

It's bogus in the sense that no one ever tunes a car to 15.4:1 and expects it to live and that 12.6:1 is where peak power is made. Maybe peak power was made at 12.6:1 30 years ago, but not today.

As Steve Wong point out, the chart seems to show that 13:1 is where peak power is made. That, or slightly leaner, is the number I have been suggesting is where peak power seems to be made these days. Why the chart labels 12.6:1 as where peak power is made is beyond me. Dated information?

Scott

brads911sc,

Feel free to tune your car to 12:6:1 for power or 15.4:1 for economy. If you do the former, you are leaving performance on the table. If you do the later, you will be rebuilding your engine soon.

Scott

Hmm...in '87, Porsche changed the chip maps to net an increase of 10 hp over the '84-86 versions. So obviously, Porsche "left a bit on the table" during those earlier years. I don't have empirical data either, but after many years the "real world" data seems to speak for itself imo. To be clear, if YOU aren't comfortable, then don't do it...nuthin' wrong with leaving it stock either, but where's the fun in that :)? YMMV....

This is merely a chart showing the relation between AFRs and power/economy. No one is suggesting anyone tune their car to 15.4:1 :rolleyes: And certainly cars are different, but the relation between power and economy with regards to AFR still exists.

I had a car that had a lean burn mode and it was normal to see 25.8:1 AFRs....

Who said anyone was tuning to either extreme? Its a simple relationship graph. we aren't idiots. Its high school math.

Every event has a similar graph of extremes. cost-benefit, pros-cons, with a sweet spot/optimal value. ever study economics, statistics or finite math? doesn't make the graph bogus. your comments just show how little you actually know... why don't you go do a few thousand dyno runs and report back on your magic AFR number.

It is normal for OEMs to tune to 14.7:1 for idle and light part throttle conditions as that is the load condition the majority of the public spends over 90% of the operating cycle of their street vehicles. 14.7:1 is also the ratio for gasoline to acheive Lambda 1.0, where the catalytic converter is most efficient at catalyizing the exhaust components of HC, CO, and NOx into H2O, CO2, and N2. Since idle and light part throttle is usually a cruise situation such as on the freeway, achieving only 80% of power (as per the above chart) is an acceptable tradeoff in exchange towards the fuel efficient ratio of 15.4:1 while still being able to catalyze the majority of exhaust components. The reason OEMs don't usually target 15.4:1 under such conditions is going that lean increases NOx significantly by multiples more than what a catalytic converter can process. That's not to say there weren't some vehicles that attempted to do so. The Honda Civic HX (if I recall the name correctly) was one such vehicle that did such by utilizing a wideband oxygen sensor in the exhaust (vs. the narrow band sensors used by all cars) to accurately measure and modulate the mixture to create an extremely fuel efficient engine.

However under load, fuel maps in most cars transition to a richer mixture to achieve good power and response. Since full load and acceleration conditions is normally a less than 10% operating condition, the rich mixture is deemed acceptable for emissions limits, and why emissions testing only tests for emissions under idle and light load cruise conditions. Lean mixtures under load and full throttle also accelerate cylinder head and piston temps significantly increasing the propensity of an engine to predetonate, and thus a significant reduction in ignition timing is necessary to prevent such, thus further reducing engine efficiency and power. A richer mixture such as that in the above graphs, 12.6, or 13.0, take your pick, keeps the mixture cooler under combustion preventing predetonation in comparison, which allows additional ignition advance limits, further increasing engine efficiency and power. Going too rich though such as 11.0:1, over extinguishes the burn, reducing the peak pressure of the burn, necessary to optimize the torque of the stroke as the piston returns down from top dead center.

OEMs, such as Porsche did to the 3.2, go much beyond 12.6, to as rich as 11.0-11.5:1 at full throttle above 5000 rpm. The extremely rich mixture accomplished two goals: a) as a warranty margin for using substandard fuel and/or improperly maintained or functioning engines; b) as an exhaust coolant for the ceramic monoliths of the catalytic converter to keep them from melting on vehicles that went full throttle on the Autobahn for 2 hours straight. In the lower rpms below 4000, Porsche programmed the full throttle AFRs closer to 14.0 for emissions and fuel efficiency. This practice continued onto the 993, until the 996s and on when the programming changed to a more consistent 12.8-13.0 across the rpm range for better power.

Scott,

Perhaps this will help you understand the value of the graph. No one is choosing a hard and fast number off a graph and selling that as gospel for all conditions. That is why your comments about 12.6 vs 15.4 make you seem uninformed -- unlike the engineering team at Bosch. That is what Steve is telling us. What is good at Cruise is not good at WOT. Tuning a steady 13.3 or 13.1 across all conditions is equally elementary thinking and not wise. Why? because at cruise you are wasting gas, and at WOT, you may be in a lean condition depending on the conditions. Altitude, gas quality, octane level, ambient temps, all included. So please put the" smarter than you" attitude aside. There is no magic number for all conditions. I am sure with your thousands of Dyno runs you know that. right?

Just a little high school math. It will help you understand how x and y are related, and how you can use knowledge of one to predict the other. Of course, with thousands of data points, the Bosch graphs involves more complexity and likely many more variables than a simple x and y, but this video will give you the basic idea. In short, you can graph all of the x and y values, and draw lines that show various relationships. The next step in critical thinking is to actually solve for the optimal value even though that particular "optimal" x and y value may not even be in your data set. I am by no means expert in this subject matter, but my 11th grade son was doing this in his high school math class this last year.

Graphing Linear Functions by Finding X,Y Intercept - YouTube

Good luck.

In a word, Yes. I don't know Steve W, but i do know what he is saying is true based on the many hours i have spent on the dyno.

Meanwhile, the debate rages on
 

Already eaten three boxes of popcorn on this one as the debate rages on as I now sip my sweet ice tea and marvel as to why anyone is taking the bait lorenfb is casting. http://forums.pelicanparts.com/support/smileys/wat.gif

^You call that bait? We have a different word for that around here.

http://forums.pelicanparts.com/uploa...1340339857.jpg

Oh no. I just soiled my key board.