Wait, the 3.2 can use 87 octane with a stock DME chip??

[rnln]

Clearly understand. Thank you.

Originally Posted by ischmitz

Octane rating doesn't change HP performance. It enables changing the engine or mapping to allow for more power. So switching fuels alone doesn't change power output on a 3.2. It is a commonly accepted fact that Porsche left some HP on the table in favor of engine longevity when tuning the 3.2 engine. This is especially true for the U.S. spec models. That's where chipping comes in.

Knocking depends on many factors such as ambient temperatures, driving style and overall condition of the engine. A newly rebuild engine might not knock where an older engine with lots of carbon deposits in the combustion chamber starts knocking. Further you have to consider that more modern platforms have knock sensing and adaptive ignition retard. The 3.2 doesn't have this feature so it was tuned to be safe under worst conditions.

In the end it's up to everybody how much risk you'll want to take by reducing gas quality and pushing performance by chip tuning. Being very conservative you'd fill up with the best gas you can get while leaving the timing stock. That's what Porsche did. They built in ample safety margins for crappy gas here in the U.S. The European models have different timing to take advantage of the higher octane fuels commonly available over there.

Bottom line. 87 octane is fine with a stock U.S. chip and the manual says so. Once you go to 91 there is some headroom for a reasonably tuned chip. However, as the engines age its tendencies to knock could increase.

Ingo

[rnln]

Around here, the highest can find in most gas stations is 91. If that is true, it is very inconvenience.

Originally Posted by Nick Triesch

I think some of you guys are wrong. Just checked my 85 Carrera's owners manual and it says under technical data in the back to use 92 rating in USA pumps premium unleaded fuel only.

[Arne2]

Originally Posted by Nick Triesch

In fact, it says to use premium in several places in the owners manual. 87 is not premium.

Perhaps it varies from year to year. My '84 manual is very clear - 87 minimum, 92 recommended. As I noted, I've never put less than 92 in it, but apparently the stock chip timing map on an '84 can tolerate 87.

[Quicksilver]

One detail not touched on here is what other differences there could be between the premium and regular grades of gasoline when our cars were produced.

It used to be common for manufacturers to use a better additive package in their "premium" grade gasolines. For example Chevron first introduced Techron in their premium gas. They later added it across the whole range but they still were adding more to the premium grade. They finally changed so it is the same across their whole range. (Not sure if there are differences in other parts of the additive package.)

The point is that at the time when they wrote the manuals for the Carreras there was an additional reason to select the premium grade when filling your car. I don't think it is consideration anymore but in the 70s and 80s it still was.

[larrym]

Originally Posted by sky1jord

From my 88's Owner's Manual, interpret as you choose
88's Owner's Manual – (picture) - MINIMUM 96 RON or = 92 CLC (= AKI)

all very interesting -

in any case - for my '89 3.2, i am suddenly interested in this a lot since i recently got one of Steve's chips, programmed for 91 AKI (28-pin 082 DME) - and am experiencing some pinging at tip-in at almost any rpm, and under load at lower rpm on hills (hot summer days in CA) - similar to Arne2's report here - comparably my spare '87 DME (24 pin 050) with the oem "-302" chip has no such issues (Steve wrote elsewhere that this is one of the best Factory chips) - also no problems when running a spare '84 DME

i am exploring the possibility that maybe i just got some "bad 91 gas" when i filled up to test that new SW chip, but it's disconcerting to say the least

y'all may want to read what Steve Wong wrote about this octane issue 3-26-2008
87 CLC Octane Question

given what Steve wrote in above link - i should theoretically be able to run 87 AKI (CLC) with 302 chip ??? (or for sure,with that '84 DME)

just for reference here is another link with several of Steve's comments
Steve Wong Chip Advice


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