Premium?
#1
03-22-2012, 04:15 PM
Premium?
Quick question: Will putting premium gas in my 97 blazer make it run better? Or will it make it run worse or cause something to fail since it's not designed for it? Haven't done it yet and I'm sure people have, so tell me what it did, or didn't. Probably just a waste of money but I dont know. Thanks
#2
03-22-2012, 04:57 PM
Waste of money. Octane inhibits combustion*, so unless you're having premature detention a higher octane rating won't help at all.
* Well, that's a simplification. It's less likely to combust under compression, or can be compressed more before combustion, is probably more technically accurate.
* Well, that's a simplification. It's less likely to combust under compression, or can be compressed more before combustion, is probably more technically accurate.
Last edited by wyzardd; 03-22-2012 at 05:03 PM.
#3
03-22-2012, 10:38 PM
unless you have your truck tuned for it then it wont do anything negative or positive for you.
#5
03-23-2012, 04:20 PM
Some articles about octane
High Octane Gas Myth
The Low Down
The Straight Dope on gas
and a post by Pettyfog from last Nov (link to thread)
High Octane Gas Myth
The Low Down
The Straight Dope on gas
and a post by Pettyfog from last Nov (link to thread)
Originally Posted by pettyfog
But there should be some further definition for those who care.
Spark knock, Detonation, preignition, and burn rate are often related to octane but are distinct issues.
Detonation is caused by the temperature of the air/fuel mixture reaching the point where the fuel ignites by itself. That is purely a function of ambient air temp/stoich ratio eg 14:1/ and cylinder compression ratio. Detonation breaks piston rings and can burn the top right off a piston, let along the plug electrodes. Mainly caused by 'too lean' and/or too low octane for compression ratio.
It's how diesels run
Pre ignition however only happens in a 'warmed up' cylinder where the mixture is ignited by a 'hot spot', eg glowing deposits or a glowing plug tip, before the spark is sent.
It's how model airplane engines work
- Detonation can cause preignition
- and BTW, that is what caused 'dieseling' in old carb engines. It wasnt really dieseling it was hot spot ignition
Both can be reduced by enriching the mixture or raising the fuel igntion point.
Now we come to spark knock. The flame front - never mind what ignited it- burns so fast the maximum pressure is reached before the piston goes over top dead center. eg the timing is too far advanced for the compression ratio and burn rate {octane}. The burn is most efficient when the piston is already starting on the downward stroke when the peak pressure is reached.
* Too long -or timed too late- a burn will result in actual flame front going out the exhaust valve and heating headers cherry red at idle -common in the olden days when most of us had limited timing tech skills and some were stupid enough to run 12.5:1 pistons in street SBC's
- reason being you need 105 octane at least for that ratio and even with the superpremium pump gas you got anywhere from 97 to 100 octane, max.
SO... you had to retard timing too much to start the freepin engine, and couldnt change the curve nearly enough in the stock dist. Could have been helped by modding the point plate for more travel and hooking up a 'retard to start' cable or solenoid to get to a couple deg ATDC, but we were dum. Set base timing to 12 deg BTDC @ 850 rpm. Should have been at least 20 but the engine balked at spark which I recall was about 2 deg BTDC in crank.
*Now THIS * is why it's not smart to even think of running 105 octane in the stock 9.3:1
First, it's not efficient in either cost of operation or fuel mileage. Second it can do real damage and there's only so much you can tune for.
This is why production turbo cars used reduced compression ratios {dished pistons} along with requiring premium gas for full boost.
Spark knock, Detonation, preignition, and burn rate are often related to octane but are distinct issues.
Detonation is caused by the temperature of the air/fuel mixture reaching the point where the fuel ignites by itself. That is purely a function of ambient air temp/stoich ratio eg 14:1/ and cylinder compression ratio. Detonation breaks piston rings and can burn the top right off a piston, let along the plug electrodes. Mainly caused by 'too lean' and/or too low octane for compression ratio.
It's how diesels run
Pre ignition however only happens in a 'warmed up' cylinder where the mixture is ignited by a 'hot spot', eg glowing deposits or a glowing plug tip, before the spark is sent.
It's how model airplane engines work
- Detonation can cause preignition
- and BTW, that is what caused 'dieseling' in old carb engines. It wasnt really dieseling it was hot spot ignition
Both can be reduced by enriching the mixture or raising the fuel igntion point.
Now we come to spark knock. The flame front - never mind what ignited it- burns so fast the maximum pressure is reached before the piston goes over top dead center. eg the timing is too far advanced for the compression ratio and burn rate {octane}. The burn is most efficient when the piston is already starting on the downward stroke when the peak pressure is reached.
* Too long -or timed too late- a burn will result in actual flame front going out the exhaust valve and heating headers cherry red at idle -common in the olden days when most of us had limited timing tech skills and some were stupid enough to run 12.5:1 pistons in street SBC's
- reason being you need 105 octane at least for that ratio and even with the superpremium pump gas you got anywhere from 97 to 100 octane, max.
SO... you had to retard timing too much to start the freepin engine, and couldnt change the curve nearly enough in the stock dist. Could have been helped by modding the point plate for more travel and hooking up a 'retard to start' cable or solenoid to get to a couple deg ATDC, but we were dum. Set base timing to 12 deg BTDC @ 850 rpm. Should have been at least 20 but the engine balked at spark which I recall was about 2 deg BTDC in crank.
*Now THIS * is why it's not smart to even think of running 105 octane in the stock 9.3:1
First, it's not efficient in either cost of operation or fuel mileage. Second it can do real damage and there's only so much you can tune for.
This is why production turbo cars used reduced compression ratios {dished pistons} along with requiring premium gas for full boost.
Thread
Thread Starter
Forum
Replies
Last Post
