What are the differences?

[EPorsche]

For the following years, 77, 78-79, and 80-83, there are three different AAR. What is the difference between them. Called Bosch and they tech person couldn't tell me.

[Dave Colangelo]

Well the 77 911 had the 2.7 and the 78 was the first year of the SC which had the 3.0. The early SC's did not have a lambda feedback system which I think came out in 80 so my guess is that they are all different because the 77 is for the 2.7L engine the 78-79 is for the non lambda SC's and the 80-83 is for the Lambda SC's then 84 and up would be the EFI 3.2 Carrera's which is a whole other system.

Regards
Dave

[porwolf]

There is a big difference between a 77 2.7 engine and the 3.0 SC engines starting in 78. The 77 case is different, I think made out of magnesium, where head studs pull out easily. The 3.0 SC cases are more solid and made out of aluminum. They are considered much more solid.

[Dave Colangelo]

Yup the magnesium was the issue. It does reduce weight quite a bit but the pulled head studs were the effect that you got from using a far softer metal. That being said each engine has its strengths and weaknesses. I have never owned a 2.7 so i wont comment much on them but I have heard many horror stories about them. The 3.0 is a very solid engine I have yet to have an issue with mine and have put almost 10K on the clock which now reads just over 150K. The Bosch people wont be of much help the guy that most likely designed the system is long gone and the blue prints are long lost in a room of file cabinets.

Regards
Dave

[timmy2]

LOL, I think he wants to know the difference in the AAR's not the engines...
Boyt911sc where are you?

[EPorsche]

That correct, what is the differences between AAR, not the cars themselves. Is it how much they open, the shape of the orifice, the elements resistances or etc?

[Two Rivers]

It`s been a long time , but if I remember the early AAR`s superseded to the later ones. The heater coil resistance was the only thing changed.
The later ones had more resistance across the coil or vise-versa.

So the only thing that would change would be the closings time of the little door to a different time so idle down time would be the only deferents.

I do not see a problem using one or the other as it just regulates air for high idle when cold and the deferents in time to close is not that different.

I think it had to do with the cat converter getting hot sooner or something like that.

[EPorsche]

Does the AAR, when fully warm, closes completely? I don't think they close all the way. When I went to EFI I got rid of the aluminum line that goes from the starter control valve to the AAR with a rubber hose. Recently I changed the hose to larger SS braided hose with a bigger diameter and it threw my fuel table off. I developed a lean stumble. Went back to smaller hose and the car was running rich. Had to revert back to leaner table.

[timmy2]

I've bench tested a couple of them and they never seem to seal off completely.
That would explain the mixture troubles you have run into.