Performance Tuning - The Myth -

[Lorenfb]

And what is the basis for assigning numbers to a generic chart, i.e. Is there a
reference cited that adds validity to doing that? Maybe the scale is really 50%
to 100%. And if so, then the change in torque from an AFR of 12.6 to 14.7 is
only 4%. Has a scale been assigned to fit one's desired result?

"In the areas of interest - near the maximum power point and the minimum fuel
consumption point - those curves are relatively flat. Even if the system can be
adjusted to deliver the perfect mixture (just at the point of maximum power),
the gain promises to be pretty small. There are no huge amounts of horsepower
to be unlocked there."

"Bosch Fuel Injection & Engine Management", Charles O. Probst, Chapter 7, pg 7,
ISBN D-8376-0300-5

[LJ851]

Hey Loren, If you want others to believe you, post your own dyno charts proving your theories.

[Big Jon Jacobs]

Originally Posted by LJ851

Hey Loren, If you want others to believe you, post your own dyno charts proving your theories.

That is what I have been saying all along. Read my prior posts.

[Tippy]

You weren't the first

[Lorenfb]

The actual torque changes are only about 3% over the AFR range of about 11.8 to 14.7.

References:

"Automotive Handbook - Second Addition", Bosch, 1986, pg 439, ISBN 0-89883-518-C
"Automotive Handbook - Third Addition", Bosch, 1993, pg 428, ISBN 1-56091-372-X
"Automotive Handbook - Seventh Addition", Bosch, 2007, pg 641, ISBN 13-978-0-8376-1540-Q

These data provide additional support to the OP which stated that once the AFR is within
a few points of the maximum torque, insignificant torque improvements are gained
compared to small changes in the ignition timing which have a significant effect on torque.

Again, performance tuning of a stock engine, e.g. 911 3.2, in reality is just a simple effort
of increasing the timing advance over what Porsche had determined as appropriate,
given the lack of knock control.

[petevb]

I'll weigh in and give my opinion: There is certainly truth to some of what Loren says, but he also makes some big errors and reaches invalid conclusions because of them.

Taking his three main points out of order:

Point 1:

Originally Posted by Lorenfb

tweaking the AFRs for added performance yields basically no performance improvement once the AFRs are within one to two points
of the ideal AFR of 12.6

Clearly false, as others have said. Yes there is an area around ideal where there are limited gains, but Loren clearly doesn't understand how small that area is. If by "within 2 points" he means either a 10.6 AFR engine, which is terribly rich, or 14.6, that's a dangerously lean place to try to make max power. There is without question a significant, measurable direct effect on hp across this range.

Even more important, however, is the indirect effect the graphs do not show:

The first of these is the interaction between AFR and timing- the leaner tune is much more likely to detonate, and timing must be adjusted accordingly to maintain a given margin of safety, while it must be adjusted in the opposite direction for the richer motor. In fact across the range air fuel ratio, timing and safety margin are linked. So while a graph might show a relatively minimal drop in power with a 13.5:1 ratio, what it doesn't show is that timing must also be pulled out to safely run that ratio with the same safety margin, compounding the effect.

A second indirect effect is on engine temperature. A richer engine runs cooler which is why much good tuning is done with exhaust gas temperature measurement, but too rich and you get issues with cylinder wash-down, etc, that negatively effects reliability. As tuning for "Performance" naturally includes durability and reliability, these issues can't be ignored.

Taken together all of these require a well tuned engine to run in a relatively narrow A/F ratio band for peak performance. The ideal A/F ratio varies not only from motor to motor, but also within one motor: gas quality and particular point in the rev range (volumetric efficiency) both have an effect.

Now a separate issue, to some extent, is did Porsche get the air fuel to be ideal in the first place? If it's already ideal then obviously that can't be improved on. As stated, however, Porsche engineered a generic solution for a range of fuels and usages. When a given gas quality, maintenance standard, intended usage, expected conditions, etc are known I do believe it is possible to optimize the A/F ratios for that, improving (slightly) on Porsche's necessarily generic solution.

Point 2:

Originally Posted by Lorenfb

performance tuning... compromises the margin of engine safety that Porsche included

This I generally agree with. There is no free lunch, and the ability to run well on all the fuels and engine conditions Porsche engineered for is almost certainly reduced if a tuner successfully produces more power. Remember they only have two main knobs to turn- fuel and spark, and one can't perform magic with these two knobs.

However. As others have pointed out, what's an "acceptable" margin of safety is a non-trivial question. We've seen Porsche themselves change their mind on this question by tuning different model years differently.

My other car, a BMW 1M, offers a more dramatic example. It uses the same N54 motor with very minor tweaks as was launched in 2006. Then rated a 300 hp and 295 ft lbs, BMW has since decided that more is perfectly safe, and with software changes my version of the same motor is now rated at 335 hp and 370 ft lbs (and in reality often delivers those numbers at the wheels on a dynojet, suggesting it's making closer to 370/ 410). Not coincidentally my motor's ratings are near identical to what some chip tuners have been providing for the older version of the motor for years. Was the margin of safety compromised? Absolutely. In an acceptable way? BMW thinks so.

Point 3:

Originally Posted by Lorenfb

the reality is that performance tuning is neither an effort requiring any knowledge and capabilities beyond what most back yard mechanics know... This 'tuning' is nothing more than a minor engine tweak... Additionally, this effort hardly requires any real knowledge...

Yes it is true that DME tuning is now becoming more accessible to the masses. You can go out and use laptop to do it yourself if you're willing to go to the effort, and I've done that. And making more power is not a mystery- as we said there are only two knobs. So what's the difficult part?

Knowing where the line is.

Knowing how far you can push the motor while preserving the needed margin of safety is the difficult part, and that's where a good tuner earns his money. It takes real testing, ideally on both the road and a dyno (preferably load dyno, engine dyno being best), looking at EGTs, etc. And it takes knowledge.

A tuner is playing a high stakes game- on the one hand there is the desire to maximize power, but on the other they can't blow a customer's motor up. It's a small community, and that's the kiss of death, weather you're tuning for the Daytona 24 or street car enthusiasts. A tuner's livelyhood lives and dies by reputation, and blowing a motor is the surest way to lose it.

So sure you can tune your car yourself, crank some timing and make more power, but without the knowledge of where the line is you're playing Russian roulette. A good tuner, on the other hand, is playing chess, and a good one has played the game many times before. Unless you really know what you're doing I'd strongly suggest you don't go off turning dials and leave it to someone who does (and has more to loose than you do, if they are good). There is also some trick, however, to knowing who a good tuner is, as there are also bad ones.

I do believe Loren is not being straight about the dyno chart he posted, making me question not only his points but his ethics and motives.

[Rob H]

Well put, petevb!!!
Can we consider this chapter closed and now go out and enjoy our chipped or unchipped cars?

[LJ851]

Originally Posted by Rob H

Well put, petevb!!!
Can we consider this chapter closed and now go out and enjoy our chipped or unchipped cars?

If only it were that easy....

[KFC911]

Originally Posted by Rob H

...Can we consider this chapter closed and now go out and enjoy our chipped or unchipped cars?

Originally Posted by LJ851

If only it were that easy....

"Chips suck, case closed"

[Jeff Alton]

Loren,

You must have missed my post. Perhaps you could answer these questions for us, most are yes/no answers so you should be able to handle it. It would provide some context to your original post with the dyno graph and help us all understand your expertise on the subject at hand.

Here is the post:

Loren,

The facts always seem to get lost in your replies. So lets play a little game of question and answer to clear things up.

What year was the 3.2 911?

Were you actually present during the dyno runs?

What dyno was used?

Did you do the tuning, or someone else?

Who paid for the session, the car owner or you?

Surely you have some pics, a reciept or something to show you were there?

Why is it that you have not responded to Steve W's 100K challenge? I understand that is a large sum, but he may even do it for $100.00.

[Big Jon Jacobs]

Originally Posted by Tippy

You weren't the first

I won't be the last either.

[andyt11]

Post #111 could be the best post ever.

[scarceller]

Loren, you can't simply advance timing 1 deg and expect a 3 to 4 hp change! You are mis-leading folks by making this statement! If what you are saying is true then we add 10deg advance and gain 40HP? your nutts! Tuners don't use back yard tools to tune! We use a dyno and not just any plain dyno, you MUST use a load dyno such as a Mustang or Dynopak! And we don't just throw a few degrees of ignition we use very specific tuning procedures to determine optimal ignition for the give engine condition. I spend a few hours dialing in a PT igntion map and I don't just turn knobs, I use a process! Stop making this sound so simple please!

[scarceller]

One other area the factory did not address very well was ignition timing correction based on Intake Air Temps. The ignition that produces peak torque at 30degF is not the same ignition to be used at IATs of say 95degF. When you understand these principles you can get more aggressive torque at colder temps. The factory did very little here and simply tuned these motors for worse conditions, like assuming 140degF IATs! It's these areas of understanding that can allow us to get more torque out of a factory motor.

[scarceller]

If you really wish to get a good solid understanding of howto tune fuel and ignition goto Amozon.com search for Greg Banish and buy both his books! Loren, I suggest you do this, read them then come back educated.

Seriously folks these are the best books of seen, Greg has a unique writing style that's easy to understand and his concepts and approach to tuning is spot on. You'll gain a solid understanding of how important Ignition and Fuel is to achieving peak torque.

[Lorenfb]

"Stop making this sound so simple please!"

But it is so simple that even high school auto shop students can do it,
i.e. a PC, an emulator, an app, and some dyno time as was done to
provide data for the OP.

The details are all here: http://www.systemsc.com/tests.htm

[brads911sc]

Originally Posted by Lorenfb

"Stop making this sound so simple please!"

But it is so simple that even high school auto shop students can do it,
i.e. a PC, an emulator, an app, and some dyno time as was done to
provide data for the OP.

[Hydrocket]

Originally Posted by Lorenfb

i.e. a PC, an emulator, an app,

How much for this gear??

[Lorenfb]

"How much for this gear??"

1. Netbook Laptop WinXP (new) $250, Ebay WinXP PC Laptop $150
2. EPROM programmer - $100
3. EPROM Emulator - $150 (real time dyno mapping)
4. Map Tweaking Application - $300 - $400
5. EPROM chips - $3.00

Three to four re-mapped chipped @ $300 each pays for the investment.

Typical fuel and ignition maps (idle - 1X1, part throttle - 2X2, full throttle - 1X1)
are as shown here: Tests

[petevb]

I just figured out Loren's agenda: He sells stock chips.

I couldn't figure out why someone would lie about a dyno chart- clearly no stock 3.2 looks like what he's posted. Of course when you realize how he makes his money it becomes quite clear.

So he comes on the board a few times a year, spreads some fear, uncertainty and doubt, and hopes people buy what he's selling. The fact is he's intentionally misleading, which is why he won't answer simple questions.

So this is basically a disguised sales thread. Nice. I wonder how much less SW would sell a stock chip for?