Gasoline/ 1973 911 Targa 2.4 Mfi

[AZNPLUMBER]

WHAT GASOLINE ARE U GUYS USING ON YOUR EARLY MODEL 911S? I HAVE A 1973 911 TARGA 2.4 MFI

[ed martin]

I had a 73 T MFI. The Check, measure and adjust manual was adamant about using only 87 octane. I'm not sure if that applies to the S though.

[AZNPLUMBER]

I WAS THINKING ABOUT USING 93 UNLEADED

[Early_S_Man]

Either 93 or 91 gas is a waste of money for a stock 2.4, and may actually cause driveability problems due to being harder to ignite.

If you was to use a better grade for the additive package, or to offset gasoline companies announced intent to seek permission to sell lower than advertised octane gas ... use 89.

[Grady Clay]

AZNPLUMBER,

Welcome to the Forum. You will find a lot of help here.

What ’73 do you have? T, E, S, Carrera 2.7 RS, 2.8 RSR? What is your use – daily driving, tours, canyon runs, DE or other track time? Makes a difference.

You will find many of the most knowledgeable Porsche people here. The art is asking the right question.

Your question about fuel is very germane. Much has been discussed about this. A good place to start is a Pelican search using the keywords “fuel, gasoline, octane and MFI.” MFI = Mechanical Fuel Injection.

This is a very visual forum; cool pictures of your 911 will be appreciated.

Posting your location will help connect you with local friends.

Most here try and use proper American English and reduce the jargon. This is a world wide forum and we want our non-English first language members to be able to read and understand the posts. Many language translation programs only work well with proper spelling and syntax. It is our responsibility to provide that.

Not using Caps Lock will also help.

Again, WELCOME.

Best,
Grady

[ed martin]

I'm going to advance my own hypothesis here. I believe the octane rating becomes critical particularly when the engine is really being pushed and is running hot. Under these circumstances if your using gas with too low an octane rating, because the engine is hot, the gas will precombust, resulting in pinging and loss of power. This effectively alters the timing (precombustion). The higher octane slows the combustion, so depending on what type of driving you do, the outside temperature, inclines and generally how hard you push your engine, that will determine what octane you want to use. With MFI, these systems are notorious for running very rich. A rich mix tends to run cooler, whereas lean runs hotter. I know mine took forever to warm up, and once warmed up the temperature didn't stray far from 180 degrees. Hence with MFI, the necessity for lower octane. With a higher octane and a rich mix you will probably experience problems achieving proper combustion with a resultant loss of power. I know that CMA states very low 87 octane so you probably want to start there. If you experience pinging problems upgrade by imcrements until pinging disappears.

[SandyI]

Been filling up my 2.0 911E w/MFI with whatever Chevron, Mobil, Union 76, Shell, etc., considers their highest octane gas here in Cali. Have had no gas related engine problems since I've owned the car accounting for 25,000 miles driven in 4 1/2 years including a dozen track days at Streets of Willow with the POC.

[AZNPLUMBER]

thank you for the info. i will be using 89 octance to start with.