fot 5.13s going to 4.10s Part II
08-04-2008, 11:01 AM
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fot 5.13s going to 4.10s Part II
OK,
At the advise of my mechanic buddy, before I set the gear shop loose on my rubi, I tried 91 octane NON-ethanol (hard to find non-ethanol in Denver for some reason) just to see if there was a difference.
It is still not quite strong enough to hold 60 up the steep parts of I-70. But its freaking close. Close enough that I believe my money will be better spent finding another few horses. I havent decided how yet. Time for some research.
Also, I dont want to start a whole argument about octane. I have no idea if its the octane or the fact the fuel was actual gasoline and not a mix, or some combination. Maybe my jeep just needed a rest... The bottom line is, she has a touch more power. One more touch and I will be a happy camper.
At the advise of my mechanic buddy, before I set the gear shop loose on my rubi, I tried 91 octane NON-ethanol (hard to find non-ethanol in Denver for some reason) just to see if there was a difference.
It is still not quite strong enough to hold 60 up the steep parts of I-70. But its freaking close. Close enough that I believe my money will be better spent finding another few horses. I havent decided how yet. Time for some research.
Also, I dont want to start a whole argument about octane. I have no idea if its the octane or the fact the fuel was actual gasoline and not a mix, or some combination. Maybe my jeep just needed a rest... The bottom line is, she has a touch more power. One more touch and I will be a happy camper.
08-04-2008, 11:16 AM
#2
JK Super Freak
Your mechanic buddy is a moron as far as the octane issue goes. (sorry)
At high altitudes/In the mountains, you want LOWER octane ratings, NOT higher, to add power.
At higher elevations....The air is thinner/the charge is less dense, the higher octane fuel burns slower than the lower octane fuel at any given altitude, so - to compensate, you need the fuel to burn faster, to make up for the drop in pressure, etc.
To get it to burn faster, you use lower octane rated gas.
Higher octane gas has LESS power in the mountains than lower octane gas...explain it to your buddy (He SHOULD have already known this, as a mechanic....)
Perhaps you had been using higher octane to get more power....? That would explain more power loss for you to try to recover...?
Anyway - Regular gas in sea-level-ish places has a higher octane rating that gas sold in Denver/higher altitude locations...regular gas is NOT the same octane rating across the country....BECAUSE of the altitude/octane relationship.
I hope that helps!
At high altitudes/In the mountains, you want LOWER octane ratings, NOT higher, to add power.
At higher elevations....The air is thinner/the charge is less dense, the higher octane fuel burns slower than the lower octane fuel at any given altitude, so - to compensate, you need the fuel to burn faster, to make up for the drop in pressure, etc.
To get it to burn faster, you use lower octane rated gas.
Higher octane gas has LESS power in the mountains than lower octane gas...explain it to your buddy (He SHOULD have already known this, as a mechanic....)
Perhaps you had been using higher octane to get more power....? That would explain more power loss for you to try to recover...?
Anyway - Regular gas in sea-level-ish places has a higher octane rating that gas sold in Denver/higher altitude locations...regular gas is NOT the same octane rating across the country....BECAUSE of the altitude/octane relationship.
I hope that helps!
08-04-2008, 11:32 AM
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TEEJ,
You clearly know more about this than I. But the fact remains, she climbs better with this fuel. I will ask if it is the octane or the non-ethanol that he believes to be the relevant factor...
edited to say:
I will try the 87 octane non-ethanol next time and see how that does.
You clearly know more about this than I. But the fact remains, she climbs better with this fuel. I will ask if it is the octane or the non-ethanol that he believes to be the relevant factor...
edited to say:
I will try the 87 octane non-ethanol next time and see how that does.
Last edited by greggradwohl; 08-04-2008 at 11:37 AM.
08-04-2008, 11:51 AM
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Your mechanic buddy is a moron as far as the octane issue goes. (sorry)
At high altitudes/In the mountains, you want LOWER octane ratings, NOT higher, to add power.
At higher elevations....The air is thinner/the charge is less dense, the higher octane fuel burns slower than the lower octane fuel at any given altitude, so - to compensate, you need the fuel to burn faster, to make up for the drop in pressure, etc.
To get it to burn faster, you use lower octane rated gas.
Higher octane gas has LESS power in the mountains than lower octane gas...explain it to your buddy (He SHOULD have already known this, as a mechanic....)
Perhaps you had been using higher octane to get more power....? That would explain more power loss for you to try to recover...?
Anyway - Regular gas in sea-level-ish places has a higher octane rating that gas sold in Denver/higher altitude locations...regular gas is NOT the same octane rating across the country....BECAUSE of the altitude/octane relationship.
I hope that helps!
At high altitudes/In the mountains, you want LOWER octane ratings, NOT higher, to add power.
At higher elevations....The air is thinner/the charge is less dense, the higher octane fuel burns slower than the lower octane fuel at any given altitude, so - to compensate, you need the fuel to burn faster, to make up for the drop in pressure, etc.
To get it to burn faster, you use lower octane rated gas.
Higher octane gas has LESS power in the mountains than lower octane gas...explain it to your buddy (He SHOULD have already known this, as a mechanic....)
Perhaps you had been using higher octane to get more power....? That would explain more power loss for you to try to recover...?
Anyway - Regular gas in sea-level-ish places has a higher octane rating that gas sold in Denver/higher altitude locations...regular gas is NOT the same octane rating across the country....BECAUSE of the altitude/octane relationship.
I hope that helps!
This is not true. The octane rating is a measure of a fuels resistance to destructuve engine knocking and is not a measure of speed of flame propagation in the combustion chamber. Once ignition has occurred, the octane rating does NOT influence the speed of flame travel. A quick web search will confirm this.
In the mountains, one tends to drive with a heavier foot and thus increased manifold pressure due to larger throttle openings. This combined with increased loads and slower speeds combine to increase the likelyhood of engine knock. When the computer detects knock via the knock sensor, it moves to protect the engine and begins retarding the ignition which, in turn cuts power. Therefore, when you increase octane you increase power in the hills.
08-04-2008, 11:52 AM
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What I don't understand is thinking that a lower aka 4.10 will produce more pulling power up the hill than 5.13s? That would effectively be like changing up a gear as your going up hill, which obviously would not help.
If you can't get up this hill, can anyone else at the speed you want to maintain?
If you can't get up this hill, can anyone else at the speed you want to maintain?
08-04-2008, 12:38 PM
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Throw a cold air intake on and maybe a throttle body spacer... check the for sale forum... pick up a used one... throw it on if it helps great! if not throw it back on and all you will probably lose is shipping!
also maybe check your tire pressure... you never know, a little more air might help you out... might wear the tires out a little faster but ya know sometimes you have to make sacrafices!
An aftermarket muffler mgiht give a liltte edge as well..
If you do decide to give up on the gears i call dibs! lol
also maybe check your tire pressure... you never know, a little more air might help you out... might wear the tires out a little faster but ya know sometimes you have to make sacrafices!
An aftermarket muffler mgiht give a liltte edge as well..
If you do decide to give up on the gears i call dibs! lol
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08-04-2008, 01:15 PM
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In the mountains, one tends to drive with a heavier foot and thus increased manifold pressure due to larger throttle openings. This combined with increased loads and slower speeds combine to increase the likelyhood of engine knock. When the computer detects knock via the knock sensor, it moves to protect the engine and begins retarding the ignition which, in turn cuts power. Therefore, when you increase octane you increase power in the hills.
08-04-2008, 01:56 PM
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Than why is it that our gas here is 85, 87 and 91? Where as in VA it was 87, 89, 93?
Just trying to learn. I hate buying mid grade just to put in 87 like the om says.
Just trying to learn. I hate buying mid grade just to put in 87 like the om says.