Accidentally put in Regular gas
06-10-2011, 05:57 PM
#31
Nordschleife Master
Dave,
I usually pour in the race gas and follow that with the pump gas fill up. Drive it around the neighborhood and that mixes everything pretty nicely.
Bill,
Indeed, if you hear these ping, the detonation is beyond the system's ability to adjust to it and thats a problem unless its immediately recognized.
There is another condition called "sub-audible detonation" where the shock waves are not discernable to the ear but damage can occur to the rings and pistons if its undetected. These Motronic engines handle that pretty well so its not an issue on these cars.
I usually pour in the race gas and follow that with the pump gas fill up. Drive it around the neighborhood and that mixes everything pretty nicely.
Bill,
Indeed, if you hear these ping, the detonation is beyond the system's ability to adjust to it and thats a problem unless its immediately recognized.
There is another condition called "sub-audible detonation" where the shock waves are not discernable to the ear but damage can occur to the rings and pistons if its undetected. These Motronic engines handle that pretty well so its not an issue on these cars.
It might be my imagination, but the motor seems to idle and rev smoother.
At 8.99/ gallon its not something I would fill up on, but a few gallons to keep the octane up seems like a good idea.
06-11-2011, 02:01 AM
#33
Nordschleife Master
06-11-2011, 10:42 AM
#37
Nordschleife Master
06-11-2011, 10:45 AM
#38
Nordschleife Master
turned the radio off, windows down, taking hits off the air cooled flat-6 induction orchestra.
must resist Stage IIIs....must resist Stage IIIs, repeat I must resist....
06-11-2011, 12:37 PM
#39
Banned
12-27-2012, 04:48 PM
#40
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lol theres no science behind this what so ever. 911's are all equipped with knock sensors even if you rev the **** out of it the only thing you can expect is lower MPG and lower HP.
12-27-2012, 07:04 PM
#42
Race Car
Yes 993's have knock sensors, and retard the timing when the ECU detects knock. However, the ecu only retards the ignition up to 9 degrees, which is quite alot, but may not be enough if the car has crappy fuel and is underload at revs.
03-21-2013, 11:54 PM
#43
Drifting
I just did the same thing. The fuel low lamp had been on for 10 miles waiting for a reputable fuel stop. I filled up, drove off and at the first light the engine was running rough. Checked the receipt and sure enough regular. Amateur hour!
Anyway, all my answers were here. Isn't this place great? Thought I'd dredge it up with some opinion as it's a good thread.
First, I'm not sure what I think is knocking is the same as "pinging" What I think about when I hear "knock sensor" is preventing that rattley sound as someone said, almost diesel-like to me, when you get on the gas in a too high gear at too low revs. (I learnt this in a Ford Cortina in '80, not my precious 993, honest) Is this pinging?
My thought was to drive the next 100 miles in one gear down, i.e. always light throttle but keep the revs over 4K. Keeps oil pressure high, mpg is probably ~ 10; I could burn off half a tank on the way to work. Then top up tank with some high octane fuel I can get at a place in town.
Then I remembered that gas has been $8/gallon in UK for many years now and the high octane gas I can get seems quite reasonable.
What do folk think would happen if I alternated tankfuls of 92 and 97+? Is it better to have a constant octane so the ECU can settle down? When I disconnect the battery I find it takes a tankful or two for the ECU to adapt and then I get an extra 10-20hp (on the butt dyno) so I suspect you'd want a consistent fuel.
Anyway, all my answers were here. Isn't this place great? Thought I'd dredge it up with some opinion as it's a good thread.
First, I'm not sure what I think is knocking is the same as "pinging" What I think about when I hear "knock sensor" is preventing that rattley sound as someone said, almost diesel-like to me, when you get on the gas in a too high gear at too low revs. (I learnt this in a Ford Cortina in '80, not my precious 993, honest) Is this pinging?
My thought was to drive the next 100 miles in one gear down, i.e. always light throttle but keep the revs over 4K. Keeps oil pressure high, mpg is probably ~ 10; I could burn off half a tank on the way to work. Then top up tank with some high octane fuel I can get at a place in town.
Then I remembered that gas has been $8/gallon in UK for many years now and the high octane gas I can get seems quite reasonable.
What do folk think would happen if I alternated tankfuls of 92 and 97+? Is it better to have a constant octane so the ECU can settle down? When I disconnect the battery I find it takes a tankful or two for the ECU to adapt and then I get an extra 10-20hp (on the butt dyno) so I suspect you'd want a consistent fuel.
03-22-2013, 04:03 AM
#44
Rennlist Member
your ECU or DME does not need to adapt and it does not adapt. You have a 1995, moreover you are in the UK, so your ECU is OBDI, and there is no cycle for readiness codes.
Bare in mind that the regular gas is 'a better' gas than the premium, since it is more prone to detonate.
But the ethanol percentage in regular is around 7+, which probably made it cough ?..... I doubt, on the first red light.
Drive your car normally, maybe at half tank, refill with premium. and stick to premium.
the 993 engine is tough and could run on leaded gas as well, so keep cool, forget about it and enjoy your ride.
Bare in mind that the regular gas is 'a better' gas than the premium, since it is more prone to detonate.
But the ethanol percentage in regular is around 7+, which probably made it cough ?..... I doubt, on the first red light.
Drive your car normally, maybe at half tank, refill with premium. and stick to premium.
the 993 engine is tough and could run on leaded gas as well, so keep cool, forget about it and enjoy your ride.
04-04-2013, 12:19 AM
#45
Drifting
geolab, I'm interested in what you say.
I should update my bio but actually I'm an expat brit in California. My '95 is ODB1 as you say, but has a trapezoidal ODB2 connector in a rectangular wall cutout so I'm pretty sure it's original. I can't read it with my generic ODB2 scan tool so don't haven't been able to get any codes. I also have '95 Nissan that I couldn't clear readiness codes - until I did the cycle posted here. That early ODB stuff is really buggy. As for the C2, she sure feels like she adapts for a week or so after I disconnect the battery.
BTW finally cleaned out that regular today, ran the warning light for 10miles and then put 16 gallons of gassy goodness back in the tank. Some would say my 20mpg for the period due to a light foot was good. I say it added to the eternity and look forward to my regular 15mpg starting tomorrow.
The car was very well behaved and I didn't hear any of that "diesel" clatter as I never had it below 2K.
....except when I was decelerating up to a red light. If I let her slow down too much in a high gear she'd start bucking. That got my attention. Can you detonate your engine under those conditions?
I should update my bio but actually I'm an expat brit in California. My '95 is ODB1 as you say, but has a trapezoidal ODB2 connector in a rectangular wall cutout so I'm pretty sure it's original. I can't read it with my generic ODB2 scan tool so don't haven't been able to get any codes. I also have '95 Nissan that I couldn't clear readiness codes - until I did the cycle posted here. That early ODB stuff is really buggy. As for the C2, she sure feels like she adapts for a week or so after I disconnect the battery.
BTW finally cleaned out that regular today, ran the warning light for 10miles and then put 16 gallons of gassy goodness back in the tank. Some would say my 20mpg for the period due to a light foot was good. I say it added to the eternity and look forward to my regular 15mpg starting tomorrow.
The car was very well behaved and I didn't hear any of that "diesel" clatter as I never had it below 2K.
....except when I was decelerating up to a red light. If I let her slow down too much in a high gear she'd start bucking. That got my attention. Can you detonate your engine under those conditions?
Last edited by IainM; 04-04-2013 at 12:24 AM. Reason: added clarity