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Nkuk35
03-14-2017, 08:29 AM
Is it possible with a stock 1990 cougar xr7 to run 89 octane instead of 93 and not have to worry about detonation.

RalphP
03-14-2017, 09:24 AM
The owner's manual specifies 87 or higher, although that might be for a non-SC unit.

I'd stick with the higher octane; even if it pulled timing to keep it from preigniting, it does that by hearing the preignition and then pulling timing.

RwP

Broncojohnny
03-14-2017, 10:11 AM
I wouldn't do it no matter what. Keep in mind that there is a point where the fuel detonates from pre-ignition no matter how much timing you pull out.

Nkuk35
03-14-2017, 10:54 AM
I would like to keep everything stock for now but 93 octane in PA is 3.05 per gallon and I m just wondering if I could get away with 89 octane to save money but not sacrifice performance cause this an all stock car and I don't want to have to mess with the timing because I just got her running good

DrFishbone
03-14-2017, 11:53 AM
You WILL be sacrificing performance.

You WILL also be putting your motor (head gaskets in particular) at risk.

There is an "octane plug" that you can remove that will help by pulling timing (and consequently sacrificing performance).

I'd only use less than "premium" in an emergency and drive it like a granny until you can fill it up high octane.

davec73
03-14-2017, 05:02 PM
Is it possible with a stock 1990 cougar xr7 to run 89 octane instead of 93 and not have to worry about detonation.

No, it's not.

bowez
03-14-2017, 06:01 PM
Yes if you take the blower belt off.

TbirdSCFan
03-15-2017, 10:50 AM
Is it possible with a stock 1990 cougar xr7 to run 89 octane instead of 93 and not have to worry about detonation. I've run 89 before for a brief time. If you pull the octane plug, that would help and it would run OK. Its not possible to NOT worry about it. ;)

DrFishbone
03-15-2017, 12:59 PM
Yes if you take the blower belt off.

You'd likely still see low RPM lugging knock. The timing would not adjusted with a removed blower belt.

But really...if you need to go to these lengths to save a couple of bucks a week, you have the wrong car, man.

KMT
03-15-2017, 01:07 PM
Is it possible with a stock 1990 cougar xr7 to run 89 octane instead of 93 and not have to worry about detonation.

As already noted, you can't remove the worry - once detonation is detected, it's already happened and you're in the danger zone. Trying to save a few bucks on better fuel is just going to cost more down the road. If you want to play with an SC, you have to pay to support it. If you can't afford it, pass it on to someone that can.

Ken

davec73
03-15-2017, 04:31 PM
This is why I said no. There is no other way to answer that question . You are going to have to worry about detonation if you run any less than 93 plus the cost you think your saving will be offset by fuel mileage more than likely

bowez
03-15-2017, 05:29 PM
You'd likely still see low RPM lugging knock. The timing would not adjusted with a removed blower belt.

But really...if you need to go to these lengths to save a couple of bucks a week, you have the wrong car, man.

Well if your looking to save money on fuel why would you be doing WOT anyway. So IMO without the blower you just have a N/A 3.8 with 8.2:1 instead of 9:1. Now the question would be how the factory spark curves compare.

Nkuk35
03-16-2017, 09:37 AM
Its not that I really need to save the couple bucks per week I was just wondering if it was possible because when you have to share a car with two other family members who don't work and complain every time they have to fill the car up it gets annoying after a while so I was just wondering if it was possible. And I bought it off my Grandfather for 200 bucks so getting rid of it for something else is out of the question.