Performance Tuning - The Myth -
 

Most are under the impression that the so-called 'performance' tuning of a stock
engine is an effort that is specialized requiring knowledge beyond simple
automotive engine basics, and that the effort maximizes performance
beyond what Porsche was capable of achieving when they developed their
engines without any compromises or trade-offs. So what is 'performance'
tuning for a stock unmodified engine really?

Well, the reality is that performance tuning is neither an effort requiring any
knowledge and capabilities beyond what most back yard mechanics knew
when the internal combustion engine was first developed nor yields any
additional performance without engine compromises and trade-offs. The simple
fact is that performance tuning is nothing more than increasing the timing
advance beyond what was specified for reliability by Porsche. Furthermore,
the hyperbole of 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, which is the case for a factory stock engine.
Thus, it's mis-leading to most to indicate that tweaking the AFRs will improve
performance for a stock engine.

Dyno tests (see below) have demonstrated on a 911 3.2 engine, whether
stock or non-stock, that for every one degree change in the advance timing,
a three to four horsepower change occurs from about 4500 to 5500 RPMs.
Many 911SC engine builders were aware of this effect and achieved a simple
performance effect by just loosening the distributor and slightly readjusting
the timing a few more degrees advanced, as has been the case for many
years with all early non-ECM (engine control module) controlled Porsche engines.
Obviously, this effect is limited to small changes in the timing.

So based on this simple and basic effect, it can appear to a Porsche owner that
so-called performance tuning has really accomplished something significant when
in reality it has just compromised the margin of engine safety that Porsche included,
to just achieve a marginal performance change. This 'tuning' is nothing more than
a minor engine tweak requiring no real testing and evaluation, as would be the
case for a major engine development effort. Additionally, this effort hardly requires
any real knowledge other than being able to buy a laptop, a 'tuning' app, and
programming a memory chip, i.e. An effort now days learned in high school auto shop.

Like many of the automotive performance products, 'performance' tuning is just
another marketing game of convincing the car owner that the owner needs
the product and relies heavy on word-of-mouth evangelists to promote the product
image. As is usually the case with hyped products, few purchasers really understand
what the product really is, what it really does, and what real effects it has.
So included in this thread are graphical data from dyno runs which demonstrate
what the so-called performance tuning really is all about and the myth that exists.

For more testing data on this topic, read here: Tests

Bottom line: Therefore in summary, the dyno tests demonstrated that small changes in ignition
timing result in significant torque changes versus small changes in the AFRs which produce very
little effect on torque once the AFR is near the idea. Besides, the AFRs are changed continuously
based on the intake air temp, irrespective of what the 'tuning' setting was. Based on this,
'performance' tuning of a stock engine in reality is basically just 'pushing' the ignition timing,
given the marginal effect of an AFR change, beyond the stock values and nothing more for the
claimed performance improvement. These were the actual results obtained for a 911 3.2 engine
during a 'live' dyno session. If one disagrees with the results, then one can always buy dyno
time and demonstrate a different outcome.

Here's the dyno graph where small changes (3-4 degrees) in the timing resulted
in significant torque changes:

http://forums.pelicanparts.com/uploa...1339649594.jpg

Here's the dyno graph where changes in the AFR had basically no effect on torque
once the AFR was close to the ideal of 12.6:

http://forums.pelicanparts.com/uploa...1339649650.jpg

Here's the well known standard graph of how ineffective AFR changes are on
torque once the AFR is near the ideal of 12.6 (AFR = Lambda X 14.7):

Graphs

Additional Supporting Data:

The actual torque changes are only about 3% over the AFR range of about 11.8 to 14.7.
Reference:
"Automotive Handbook - Second Addition", Bosch, 1986, pg 439, ISBN 0-89883-518-C

"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

getting out the popcorn.....

So I guess Loren is now calling out Steve Wong and saying he is selling snake oil.

This Loren person loses more and more credibility with every post.....

Scott

I'd like to see the guys who sell Performances chips response to this... A lot of what Loren is saying isn't wrong, performance chips do advance the timing of the motor, beyond what Porsche thought was a safe limit for the octane gas available

I think beyond switching cam duration/ lift profiles, and needing to readjust injector pulse duration, "chipping" a stock motor really wasn't worth the time and money

Me too!!!!!!:eek:

With the number of engines of various kinds that I have built over the years (too many to remember)...there is one thing that is consistant in the whole bunch....no two are completely alike!
I was once asked to build several 350 cu in Chevy engines...all with the same compression, cam, valves, etc....and the dyno run differences were amazing.
Even with all the same equipment...there was alost a 25 HP difference between the top and bottom of the bunch.
All that this proves to me is...there will be hidden HP in every engine...subject to altitude....temperature...humidity...and every other change in earth position and variance. (maybe even hemisphere?).
I think Loren is both correct and wrong because of this...given the narrowness of his statements.
Sorry man...you are on the right track...but keep an open mind.
Steve Wong chips probably address the advance curves and mixture control...as do others of the after market type...but that's not all they do (depending on the before mentioned variances).
After market chips will almost always pull out better numbers than the factory ones...simply because of the date...the factory ones were designed a long time ago...Wong's chips and the others are designed with time on their side (newer gas...better plugs...etc.).
My $.02 for what it's worth.
Bob

And me :D

Well stated Bob!!! In the late '60s and early '70s when I was building racing engines for modifieds (round track).. We found the same thing.. Even with all the technology available today, all principles still remain true!!

in the test you did, did you just adjust one parameter at the time? Eg just changing ignition timing and the other test just change AFR?

This post by Loren is really an oversimplification almost on the edge of "malicious intent".

First, reprogramming an ECU is not that simple if done properly. Even old systems like the Motronic used in 3.2 rely on 3D maps tying several variables simultaneously. So, you dont change a value here and there, you have to change many at the least, then you have to verify on the dyno (and road) and repeat...

Second, it should come as no surprise that sometimes the gains are significant. Porsche, like any manufacturer, tunes the engine to accept a broad range of gas quality, and always with emissions control in mind. When you're tuning, usually you can afford to forget about that, so with much less constraints, it's no wonder you get better results.

Third, dyno tests (for power and torque) are not everything. Something that can be improved (and usually is) over the factory spec is engine response / "revability". Specially in the older days, quick throttle response meant more emissions. If you care less about emissions, this too can be improved.

This post by Loren is really an oversimplification almost on the edge of "malicious intent".

First, reprogramming an ECU is not that simple if done properly. Even old systems like the Motronic used in 3.2 rely on 3D maps tying several variables simultaneously. So, you dont change a value here and there, you have to change many at the least, then you have to verify on the dyno (and road) and repeat...

Second, it should come as no surprise that sometimes the gains are significant. Porsche, like any manufacturer, tunes the engine to accept a broad range of gas quality, and always with emissions control in mind. When you're tuning, usually you can afford to forget about that, so with much less constraints, it's no wonder you get better results.

Third, dyno tests (for power and torque) are not everything. Something that can be improved (and usually is) over the factory spec is engine response / "revability". Specially in the older days, quick throttle response meant more emissions. If you care less about emissions, this too can be improved.

True enough! Tuning any engine is 3D...old geezers that would jump the timing up and enrichen the mixture in hopes of finding more power rarely were successful. Well made DME performance chips are more sophisticated than that.

Dynos can be misleading too. We campaigned a Laverda 1000 3c back in the day. Out of tune it would make about 70hp on the dyno (factory claimed 90hp). A well tuned Kawasaki 1000 (factory claimed 90hp) would make about 78hp on the same Dyno.

On the drag strip..the same out of tune Laverda was near on a second faster vs the Kawasaki with the Laverda's taller gearing and a slipping clutch.

A Charlotte Motor Speedway the Laverda (once tuned, we backed the ignition timing down from factory specs and went with some slightly leaner jets, and the clutch repaired) was 10mph+ faster and clocked 10 seconds faster on an average lap. (better brakes and handling)

My point is that it is not just dyno results as the dyno is only a base to start your tuning. It is thoughtless to advancing the timing and throwing extra fuel in an engine to try and find increased performance. I doubt SW uses this tuning technique.

Some track time comparing the before and after would be interesting.

The maps in DME chips are a wonderful place to refine the tuning of a 911 engine.

https://lh5.googleusercontent.com/-m...576/racer1.jpg

Hmm...can't disagree with Loren on this statement, but it seems to contradict what he was claiming just 8-10 years ago both on Rennlist and then here. I'm parapharsing, but in a nutshell, Loren's take was essentially that there was no REAL difference between chips (Porsche 84-86 stock, vs Porsche 87-89, vs Steve Wong, etc.) and we were all "feeling" things. So here it is in a nutshell...if you have access to "better gas", then a chip that advances the timing just a bit will indeed yield better performance. Caveat...it was NOT a "night & day" difference in my case, but incremental....just like most of the mods I've made. Oh yeah...Loren also warned us plenty about the DANGER of aftermarket chips...10 years now and my motor is still going strong.

"Chips suck, case closed" - Lorenfb (circa 2004 as I recall).

To think that Loren has a "hidden agenda" is a mild understatement imho :)

Not this again ???:(
I just hope this time round Loren provokes the right people into explaining exactly what is done to acheive the results we all feel as real and beneficial, its not i fear as simple as he would have you believe...
A...

So then, don't run low octane gas on a hot day at the track if chipped? --sounds like good advice.

Sounds to me like Loren is trying to educate people who blindly believe in a black box of magic. I know guys like that. It is a bit annoying that they have no understanding of what changes happen w/ a chip. ...or what changes happen "mechanic in a can" ... "Stop leak" or whatever mystery marvel.

Well, he's doing that, and having his subversive influence on the sales of . . .popcorn. Ask Toby.

You otoh, loses more and more credibility with every whiny post.....


. . .Mmmmm . .. Popcorn ...

Oh, and disclaimer time. I have no dog in this fight --have an SC where I get to advance the time as I like.-- no dog, other than to say that Loran has annoyed me at about the same level as those people who blind buy "mechanic in a can"

You may now return to your regularly scheduled ..... http://forums.pelicanparts.com/uploa...1339684561.gif

My experience is telling me that Loren is not too far off the mark. Where he is correct is in saying that a modified chip does tend to push reliability further out than was initially intended by the factory. I realize that emotions run high on this subject, but in engine tuning, just like life, "there is no free lunch".

And I see mentioned above, the need for longer duration/higher lift cams being introduced into the mix. Very true, for an engine is essentially an "air pump". So when a chip is used, just where is that extra horsepowere coming from?

I have donned my Flame suit.

exactly.

Good point. ..and one that I've made before. Factory 911's, from '84 on really lost throttle response. (for emission concerns)

I guess that means that Loren is trying to say that Steve Wong is set to destroy the earth. MUHAhahahaha. .. ... :D


Where's that popcorn....

I'm thinking that this might get Loren banned.

I mean, everyone has seen this...

http://forums.pelicanparts.com/uploa...1339685589.jpg


Right? :cool: