fast951

As Geoffrey stated, running Av Gas in a car is not a good idea. The Density of automotive gas is about 15% higher than the Av Gas. Running Av gas is similar to running much leaner. The Lead Content of 100LL av gas can harm many other things (cat converter, O2 sesnor,..). I have seen the results of 100LL on a turbo engine, not pretty.

Ritter v4.0

It also has dye in it I believe which injectors will not like.

Saying the timing cannot be improved, if only marginally, because the factory knew what it was doing etc. is like saying no point in replacing your hood/trunk struts because they were factory engineered to precise specifications and tolerances and made to last a lifetime (or 10 years whichever comes first).

Same with the suspension, wheels (D90s!), tires, lights, shift **** etc.- no room improvement here, so save your money.

garrett376

On a poorly tuned engine one can certainly hear the pinging/knocking. In 2 out of the 5 964's I've owned, before I fixed up the cars, I could easily hear it occurring, and easily cause it to ping/knock.

Geoffrey

Wait a minute, I read somewhere on the Internet that the knock sensing capability of the 964 Motronics would keep the engine from ever pinging, what gives?

Lorenfb

"but one of your criticisms of after market chips boasting increased power was that by using the equivalent of voodoo economics, they would advance the timing to in effect "fake" the increase."

Yes and No!

Yes in some cases, e.g. the ripeoff air filter mod where the shop just used
a 13mm wrench and turned the distributor to advance the timing, the owner
was "faked" as to what produced the increase. No the increase itself was not
"faked". What is "faked" in many "performance" chips is that the increase
is the result of an "easter egg" found in the DME maps that the Porsche/Bosch
engineers over looked ("conservative" tuning), e.g. tweaking the Win O/S to boot
the PC faster (added at patch or re-wrote some API), when all that was done
was to simply advance the timing a few degrees (turning the distributor if you
will) and calling it "tuning".

yellowducman

I can't really add much to this conversation but what I can add is when I was having a connection problem with my number 2 knock sensor and the timing would go into full retard, that was very a very noticable lack of power. The car probably retards the timing much more than what people are advancing it (even though I can't remember what it was retarding now).

By the way, that was a hard one to find on a 90 with out a check engine light and no hammer. Thank god for the Scan Tool Loaner.

Lorenfb

"The car probably retards the timing much more than what people are advancing it (even though I can't remember what it was retarding now)."

That's correct. It's 9 degrees total retard capability in the 964 Motronics,
in 3 degree increments. The key, though, is that as the timing is "pushed",
the margin before retardation can be zero which can result in a sooner loss
of power (knock control), e.g. the race track, than under stock conditions.

Most seem to forget or are unaware, as mentioned before, that when the
964 was in production, we in the U.S. had 97/98 octane. Now the best
octane (quality from some's perspective) that's available is 91. And some
still want to have their timing "pushed"?

Note: Per Porsche WKD 423 920 2M (964 Technical Specifications) the octane
indicated is RON 95.

Ritter v4.0

Plenty of 93 in Georgia (for the time being anyway).

Long ago I worked at a refinery in a quality control lab for Gulf Oil. We tested our own products obviously, but also that of Gulf's competitors- selectively. There were small differences in retail gasolines but perhaps not enough to feel or see in a car on the road.

But I digress; my point is for a given octane value, I highly doubt gas at the pump is any less quality than that of 10 or 20 years ago. In fact, it's pure speculation but I'm guessing its better in some ways.

fast951

Some opinions here brings back memories from years ago. Back then, big wig 951 tuners claimed that the factory 951 Motronic is useless when the engine HP exceeds 300hp. They all claimed the car will not run properly with larger injectors etc.. The bottom line, they didn't know how to do it, so they announced to the world that it does not work.. Now, people, running our software on the 951, are using 83# injectors (almost 2.5x the stock ones) or larger, and cars still using the motronic with our software are making 400rwhp, 500rwhp even higher.
I guess, there will be those that cannot do it, yet will continue to say it can't be done.

Tuning involves modifications of many variables, Fuel, Ignition, changes in temps, barometric changes, etc.. and we do modify many variables. Changing one variable (like ignition) without looking at the complete system is not a good approach, I agree. We look at the complete system with ALL the variables involved. It was implied that we "just bump timing and call it done", which is not the case. Interesting, how opinions are shared without any knowledge of what has been done at our end.

If and when more products make it to the market, many "it can't be done ideas" will change.

TR6

As long as we are digressing, I've also often wondered what the actual octane rating of the gasoline that I buy at the local station is after it sits in their underground tanks for a while getting mixed with older fuel and moisture that's been there for God knows how long. The fuel may test perfectly when it leaves the refinery, but by the time it gets pumped from the nozzle into your car, I wonder what the real octane rating is....

Ritter v4.0

You are really testing my memory but I believe these factors were taken into consideration and pump gas was selectively re-tested. Still, but from a high volume/traffic station and you're likely to get fresh batch

I remember lab technicians sitting in a room with an engine (not looking like anything found in a car) and would add precise amounts of reformate and platformate and taking measurements all day long, 5 days a week. Thats when I decided the job was not for me (but I was still in university anyway).

I also remember the irony of the ad on tv where Shell boasted "Shell gas- with platformate!" and the little animated car running farther than its competitor. All gasoline has platformate!

Lorenfb

"But I digress; my point is for a given octane value, I highly doubt gas at the pump is any less quality than that of 10 or 20 years ago. In fact, it's pure speculation but I'm guessing its better in some ways."

You're missing the point because of my poor choice of words.
As I pointed out (last post), I used quality to indicate a lesser octane level
and NOT the real "quality" of the refined fuel grade. Many in the past
have used quality to indicate an octane level. So in the true literal sense,
we'll avoid interchanging quality and an octane level.

Problem solved!

Ritter v4.0

So would you agree that IF Porsche set timing to the lowest common denominator including 91 there is room for tweaking?

Lorenfb

"So would you agree that IF Porsche set timing to the lowest common denominator including 91 there is room for tweaking?"

NO!!!!!!!!!!!!!!!!!!!!

And where did this 91 come from????????????

I just posted that the 964 SPEC BOOK requires 95.

And the highest here on the west coast is 91, anyway.

Maybe you need to just go to Pep Boys or Auto Zone and buy a case
of octane booster for your "performance" chip and be done with
trying to rationalize your use of a chip.

Ritter v4.0

We're trying to have an intelligent conversation here Loren- why do you insist on being getting personal? If I, or someone else has it wrong- just say so.

I think you and Porsche are talking RON 95 and I was talking of PON 91. Per below, they are the same thing.

RON MON PON
90 83 86.6
92 85 88.5
95 87 91
96 88 92
98 90 94
100 91.5 95.8
105 95 100
110 99 104.5