Originally Posted by Lorenfb (Post 3409552)

"Porsche left some large timing margins in some of these cars to accomodate poor gasolines worldwide and with experience, one can safely alter the ignition mapping (advance weights/springs or mapping tables) a bit to make noticable improvements in mid-range throttle response and torque without unintended consequences."

And the gasolines 20+ years later are WORSE!

Originally Posted by Lorenfb (Post 3409552)

"
"In short, there ARE some significant gains to be found with responsible, intelligent changes to advance curves depending on the individual engine."

Significant, HARDLY, and only for those that have an interest in selling/hyping group
buys of performance chips, e.g. Rennlist and others. Porsche could have further advanced
the timing in the Club Sport DME, (event racing where high octane fuel would be
recommended and/or used) but kept it the same as the '88/'89 stock DME.

Originally Posted by Lorenfb (Post 3409552)

Right! And NOT the self-proclaimed ones that profess to be "super engine builders"
who weren't "knowledgeable" until they began reading the hyperbole of the internet,
or those tuners that develop chips using a laptop while driving to tune the engine.

Originally Posted by Lorenfb (Post 3409552)

Another one who "doesn't get it", i.e. the point of the thread:

There's a maximum allowable 3.0/3.2 911 timing advance without knock sensors
and as an example it's NOT in the 40+ degree advance area that ALL performance
chips have.

Originally Posted by Wavey (Post 3409688)

Let's see... where's my Funk & Wagnell... H-y-p-o-c-r-i-t-e... hmmmmmm, seems to fit.

Originally Posted by Lorenfb (Post 3410170)

BOOM!!! HEADSHOT!!!!

- KTL -

So let's be specific and not present off topic dribble:

"I don't want to get off topic"
"If I had set my DC20/Super C2 cam timing to the advanced spec of 2.4mm (recommended range of 2.2 to 2.4mm) I would have valves that are well below the recommended piston-to-valve (P-V)clearance of 1.5mm intake and 2mm exhaust. In my case I couldn't even set my cams to the recommended range and had to settle on 1.85mm"

- KTL -

As was said before, the 911SC and earlier Porsche guys seem
to understand the issues by their many clear posts, where others
as usual are brain dead or have a clear vested interest in
promoting performance chips which ALL have excessive timing
advances to enhance the performance "feel".

Bottom line: The 911SC and earlier guys did good by this thread!

Originally Posted by Steve@Rennsport (Post 3407781)

Hi:

One should be aware of a phenomenon called "Sub-audible detonation" and these are shock waves that break rings as well as top ring lands.

I cannot count the number of times that we watched the rings fall on the floor during engine disassembly and the customer said they never heard a sound. Some of these people are ex hot-rodders and not rookies in this regard. :)

Detonation thresholds in air-cooled engines are NOT static; they change with engine temps (oil and cylinder head), outside air temps, mixture, fuel quality, and load (throttle position & RPM). Further, no two engines are alike, even of the same type. Failure to take all these variables into account when adjusting ignition timing can be an expensive exercise.

My best advice to anyone reading this thread is to never,.....EVER,....rely on your ears as "defacto knock-sensors" unless you have deep pockets ($$$$).

I hope this helps,

Originally Posted by Lorenfb (Post 3410170)

BOOM!!! HEADSHOT!!!!

- KTL -

So let's be specific and not present off topic dribble:

"I don't want to get off topic"
"If I had set my DC20/Super C2 cam timing to the advanced spec of 2.4mm (recommended range of 2.2 to 2.4mm) I would have valves that are well below the recommended piston-to-valve (P-V)clearance of 1.5mm intake and 2mm exhaust. In my case I couldn't even set my cams to the recommended range and had to settle on 1.85mm"

- KTL -

As was said before, the 911SC and earlier Porsche guys seem
to understand the issues by their many clear posts, where others
as usual are brain dead or have a clear vested interest in
promoting performance chips which ALL have excessive timing
advances to enhance the performance "feel".

Typical 3.2 chip guy:

"Like, what's detonation, my car feels stronger with the performance
chip and most Pelican 3.2 guys do it anyway. Like, I can't hear any new
noises, just that great sound my new muffler makes. Don't be so negative
about performance chips. The tuner's real cool & said don't worry about it"

Bottom line: The 911SC and earlier guys did good by this thread!

Originally Posted by Steve@Rennsport (Post 3409380)

I'm not comfortable with being quoted out of context like Loren did so some clarification is needed here.


1) IMHO, there is absolutely, positively no substitute for experience when tuning these engines. Knowing precisely how many degrees of advance these engines will safely tolerate using whatever gasolines, compression ratios, camshaft profiles and displacements must be factored when I setup a distributor in my distributor machine or when mapping Engine Management systems (Motec, for example). It takes experience to know what margins are safe and when an ignition profile is too aggressive for all the variables. Speculation and conjecture based solely on theory is utterly useless in this regime.

2) From experience, Porsche left some large timing margins in some of these cars to accomodate poor gasolines worldwide and with experience, one can safely alter the ignition mapping (advance weights/springs or mapping tables) a bit to make noticable improvements in mid-range throttle response and torque without unintended consequences. In short, there ARE some significant gains to be found with responsible, intelligent changes to advance curves depending on the individual engine. Blanket statements, either positive or negative, are simply inaccurate.

3) Stating wide generalizations about aftermarket chips is just as absurd as making blanket statements focused on race, religion, creed or national origin. Like people, there are good ones and not-so-good ones and tarring everything/everyone with the same brush simply displays incredible ignorance about the subject.


Porsche's family of air-cooled engines vary in design, displacement and ignition mapping tolerances so I'd strongly caution anyone contemplating such changes to discuss such things with experienced and knowledgable personnel intimately familiar with the engine in particular BEFORE making any changes (Steve Wong is one of them). IMHO, this is NOT a DIY'er, "Kentucky Windage" sort of exercise when seeking to make engine improvements with ignition timing alterations unless one can live with the consequences.

Originally Posted by Lorenfb (Post 3411178)

"After reading your post, I have to ask - do you have a chip in your '88 911 3.2 listed in your signature?"

After reading this thread and all similar for the last 4 years, it's obviously NO!

Originally Posted by Lorenfb (Post 3411167)

"all chip manufacturers except me"

Where is this promoted/said except by a few idiots????????