Premium vs. Regular & MPG

[blackdiamond]

Today I had the thought that as long as the standard $0.20 price difference between regular and premium grades holds, the cost of premium grade fuel is effectively dropping.

Simple Example: When regular grade fuel cost $2.00 per gallon and premium cost $2.20 it was a 10% increase.  Now that regular is $4.00 per gallon and premium is $4.20, it is only a 5% increase.

Why does this matter?

Higher octane fuel allows the timing to be advanced, on engines that are not completely controlled by computers, which can yield more torque and improved economy.  I believe the concept is that advancing the timing leans out the engine making it more efficient.

I know from experience that my 89 4Runner  (22RE) has more power with the timing advanced on premium grade fuel.  The question is how much, if any, am I paying for the extra "seat of the pants" power?

The attached files compares the "cost per mile" and "cost per 100 miles" over a range of mpg (12 to 20) assuming the current cost of fuel in my area.  Not all stations have maintained the $0.20 difference, but several have.

It appears that an improvement of only 0.75 to 1 mpg would yield an equal, or reduced, cost per mile driven.  This doesn't account for the slight improvement in fuel economy that may result from having a little more torque.

From a white paper that I read on www.redlineoil.com about Water Wetter, it is my understanding that a 5 degree timing advance is approximately comparable to about a 3-4 octane rating increase (They also reported an approximate 2% torque improvement on the engine they used for testing).  They were relating it to cooling, but the same relationship should apply.

So the question is if increasing the octane from 87 to 92 (+5) allows me to advance the timing 3 to 5 degrees, should I expect the 1 mpg improvement that would make running premium grade fuel cheaper?

[All_Set]

Isn't premium just regular with additives? Maybe the additives haven't gone up as much as gas??

Gas is cheap in your *area*.  lol.

[blackdiamond]

Isn't premium just regular with additives? Maybe the additives haven't gone up as much as gas??

Gas is cheap in your *area*.  lol.

"The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting." - www.howstuffworks.com

The higher grade fuels may also have higher levels of additives/detergents.  Shell V-Power has a much stronger package than their regular.

[Plekto]

With mt new header and exhaust, I find that I need to run premium to make it run best/be a bit less prone to ping.  Of course, it'll run fine on 87 as well, but as was pointed out, 1/2 a MPG gain is all you need to "break even"

Oh - Thorley header, 2 1/4 exhaust with a straight-through muffler... easily 15-20HP gain.  Massive improvement.  I now get 18mpg at 70-75mph instead of 18mpg at 60-65mph.  Of course, 2mpg improvement or so if I drove slower will take me... about 30K to make back, but then again, I can pass people for a change...

[KDXSR5]

I am calling BS on a 15-20 HP gain over stock... there is no way in hell just a header and exhaust system did that to a 4 cylinder engine. It may have woken up your engine from its not so powerful, old state (assuming it is not a rebuilt engine), but there is no freakin way it made that big of a gain from just exhaust.

[Plekto]

No, I don't have a dyno, but the OEM was horribly restricted.

5-10% grade(Route 2 north out of Glendale, CA) I couldn't even maintain 60mph in *4th* gear before.  Now I go up that same freeway in 5th - at 70mph.  Literally twice the difference between your AC on and off.   And I know that a typical AC system sucks 10-20HP on average off of a small engine when it's running, so it's got to be at least 15HP gain.   

Similar mods to motorcycles routinely net them 10-20% more HP. 

I do notice that it has a tiny bit less torque at low RPMs, but once it gets past about 2K rpm, it hauls.(seems to be designed for freeway/higher RPM use, which is where the 22RE needs all the help it can get)

http://www.toyotanation.com/forum/showthread.php?t=235212
Here's a graph of a similar header on a FJ Cruiser.  It has about twice the HP, but you can see what's happening.  Less HP at low rpms but a huge bump between 3-4K.   At 3500rpm, which is right where you'd pass on the freeway, it's nearly 25HP higher than stock.  This is exactly what the guy at Thorley said it was designed to do when I picked up a few extra parts for the install.(drove down there - nice guys)

(like in this example, there's a boost in the ~2800-4100rpm range only- but no more flogging it in 5th gear is a godsend)

So yeah, 15HP or so for a 22RE, considering how bad a design the OEM manifold was doesn't seem unreasonable.

http://www.yotatech.com/f2/22re-highflow-cat-14122/
I think it's the combination helping as well.  Header, free flow cat, free flow muffler, and 2 1/4 exhaust.  But it's not something you'd do really unless the whole system was in need of replacement like mine was.  The guys here all seem to agree, though, that it makes the 22RE move much better on the highway.

[KDXSR5]

a 20% increase in HP over stock on a 4 cylinder engine with just exhaust? NO, it isn't going to happen


OEM exhaust manifold on a 22RE is not a bad design at all... you can make your own header just by cutting the manifold at the collector and running 2.25 or 2.5 inch pipe from there on back

I have all the proof I need in my favorites on my laptop. Unfortunately, my laptop bit the bullet last weekend, so i cannot prove anything. My searching has not yielded any of the info i was trying to find.

If you think you got a 20% HP increase over stock from just an exhaust upgrade, then you just keep on thinking that. I will not argue it anymore.

Also, that FJ engine is not comparable to a 22RE at all, totally different designs (as in actual mechanicals such as bore and stroke), in other words, when talking 22RE, stay 22RE. That is a huge rule of thumb when talking engines; always stay with the same engine or an engine that is mechanically very similar to the engine being talked about. I wish I could find my articles by ENGNBLDR, but they are currently lost on my laptop.

On the freeflow cat topic: just adding a free flow cat will not improve power over stock specs in any large amount at all. If your cat is plugged, it will increase performance and power compared to what it is at currently. Notice, I have been saying gains over stock power this whole time. There is a big difference comparing stock power to whatever your engine is making now. The reason why a highflow cat wont make much difference (when compared to stock) is that the cat, in stock form, doesn't really take that much power. It is more a matter of the really small exhaust tubing used on the stock trucks.

[kneedownnate]

So yeah, 15HP or so for a 22RE, considering how bad a design the OEM manifold was doesn't seem unreasonable.

What year is your truck?  If it's a 2nd gen or newer it will actually have a very WELL designed manifold, a tri y just like a lot of the headers.

Similar mods to motorcycles routinely net them 10-20% more HP. 

SOMETIMES, I wouldn't go so far as to say routinely though!  I've seen a full system give a bike 15hp before, but that's quite the rarity!

[blackdiamond]

Here's the deal with increased HP as I see it.

Horsepower is nothing more than a calculated value from torque at a given rpm.  The fact is that you have twice the horsepower at 4,000 rpm as you do at 2,000 rpm if the torque is the same.  If new exhaust allows your engine to run a few rpm higher you could see a 15 hp increase, but that doesn't mean you would feel any difference since it doesn't require a change in torque (the only thing you can feel).

[KDXSR5]

sorry for raping the crud out of your thread blackdiamond, but I could not resist the arguement

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