Increase timing to offset $ of better gas (MPG)?

94-302-vert · Jun 5, 2006

With premium gas still being only $.20 more than regular, can increasing the timing and running premium gas offset the price difference between regular and premium?

I mean right now regular is ~$3 and premium is ~$3.20... That is only 6.7% increase in cost.

Now if I advance the timing to make use of running premium (haven't played with timing at all yet) can I gain at least this 7% increase in mileage plus have the added power when I want it?

illwood · Jun 5, 2006

That's a good question.

In theory it would work, but you would have to do some experimenting (i.e. actually do it for a tank or two of gas) and see how it works.

I know I got a decent increase in milage after my intake swap. I'm still mostly stock (read: shameful 2.73 rear gears) and I do alot of highway driving and I've done a best of 27 MPG without trying too hard. I didn't play with my timing, but my car seems to be happier with 89.

94-302-vert · Jun 5, 2006

So how many tanks of 93 should I run before I try it?

I am thinking at least two...

Right now I am getting gas every 2 days!!! so every little bit helps...

wytstang · Jun 5, 2006

Tie a block of wood to the bottom of your gas pedal, this will not allow you to go WOT. Cheap and yet very affetive lol.

Joes95GT · Jun 5, 2006

You won't get better gas mileage. You'll get the same, maybe, but nothing better. Think about it....

You can run 87 octane and 10* base timing to get the "proper" burn. By running 93 you are raising the flashpoint (can't think of a better word) of the gas, thus requiring more timing to get the gas to burn as efficiently as the 87 and it's specific tune up.

I think that makes sense....

Joe

urban96 · Jun 5, 2006

you might see a 7% increase in power but maybe not gas mileage

94-302-vert · Jun 5, 2006

I agree, no MPG improvements unless I improve the efficiency as well. I am hoping that with more power on tap and better octane will mean better efficiency and less pressure on the right foot.

Anyone try this yet?

Swarzkopf · Jun 5, 2006

you might see a 7% increase in power but maybe not gas mileage

Are you serious? 7% from bumped timing? Is this really true? I honestly don't know and am asking, not arguing.

That's 14HP on a 200 RWHP car...seems like alot for bumped timing.

HISSIN50 · Jun 5, 2006

You cant get that anal about pump gas IMHO. Along the lines of what Joe (where ya been? School probably. ) and the others said, the difference in 5 octane points (here, we have 87, 89 and 91 octane) wont yield much in the couple of degrees timing bump. What Joe said about the ignition of the fuel and timing is right - increased octane (with pump gas - not race fuel) and increased timing-advance very largely offset eachother.
Furthermore, the inconsistancy in gas is a large variable in my mind.

This comes down to one of those debates like gears - guys with gears say they dont get into the pedal as much so they dont use as much fuel. But they are winding it up a little higher.

Personally, I'd stick with the lowest grade of fuel that works for my current timing (or a timing settng near stock). In the winter is the time to bump timing up (for me anyhow - it's 105* today).

Good luck.

urban96 · Jun 5, 2006

Swarzkopf said:
Are you serious? 7% from bumped timing? Is this really true? I honestly don't know and am asking, not arguing.

That's 14HP on a 200 RWHP car...seems like alot for bumped timing.

i honestly have no clue

mo_dingo · Jun 5, 2006

Paying for 93 and bumping the timing up is like stabbing yourself in an artery and THEN removing the knife.

93 octane #1 Costs more....#2 Takes away power. Then when you bump the timing you only get some of it back.

Definately a lose-lose-lose situation.
Scott

94-302-vert · Jun 6, 2006

Dingo, based on that philosophy, why is it that we even have higher octanes, or cars that require it.

Just curious...

I can say that the car seems to run better on 93 than it did on 87, filled it up yesterday. It also seems to be getting better milage without adjusting the timing, hoping ot get a couple tanks of data before i mess with the timing though... I am an engineer and I need my data...

Joes95GT · Jun 6, 2006

HISSIN50 said:
Along the lines of what Joe (where ya been? School probably. )

Yep. I'm so glad I'm done.

Thanks for asking!

Joe

HISSIN50 · Jun 6, 2006

94-302 Vert: Scott and some of the rest of us are talkin about the ignition of the mixture in relation to the piston's displacement. That's where bumping both can be moot.

Increased octane at the pump (rather small octane spread) is for when one needs a fuel less prone to ignition. In said situation, one does NOT bump timing up. If I ping on 87 octane and 10*, I would try 91 octane and 10*. If I had also bumped timing while going to 91, it would be moot. But only raising octane (or lowering timing works just fine too) will yield being less prone to detonation.

Joe - Good stuff mang! Done for the summer or just plain done?

mo_dingo · Jun 6, 2006

94-302-vert said:
Dingo, based on that philosophy, why is it that we even have higher octanes, or cars that require it.

Just curious...

I can say that the car seems to run better on 93 than it did on 87, filled it up yesterday. It also seems to be getting better milage without adjusting the timing, hoping ot get a couple tanks of data before i mess with the timing though... I am an engineer and I need my data...

Higher octanes were created for turbo/blower cars from the factory. Because they have forced induction, dynamic compression increases which creates a better chance for pre-ignition, like a diesel, combustion w/o spark. Good for diesel, bad for us. Even if you retard the timing on the dizzy of a turbo car, it may still ping on 87 octane. Especially as it gets older, and the O2's get older. That is why Vortech still recommends running 91/93 even with the MSD BTM.

If you are truly getting better gas mileage with 93, I will walk of the plank of a ship at sea w/ my clothes on singing Ricky Martin as I trott.

The true test is to run it with 93 for 3 tanks, never taking the RPM's above 2k, highway driving only. Then remove the fuel tank, and repeat with 87 octane.

But since you commute, you have to do some city driving, which makes for uncontrollable and inconsistent data. Gas from different companies is different. Outside temperature and barometric pressure change. No realistic way to test. And your belief that the car runs better is likely psychosomatic IMHO.
Scott

94-302-vert · Jun 7, 2006

Well initial ersults are a small increase in milage. I track it pretty well and always go to the same station (75% of the time to the same pump). I haven't gotten more than 18.5mpg in the last 20+ tanks. I usually average about 18.1mpg on a 18-18.5 mpg range. On my first partial tank of 93 octane I got 18.75 mpg.

So better, kinda. I won't call it measurable yet. But the car is DEFINITELY running better. As such I have been driving faster.

As for the 2k rpm thing, that isn't even highway speeds with the 3.73's....

So I'll continue to complie data for teh next 3-4 tanks, then I may try playing with the timing. The only problem is that I have a hard time changing something if it works...

HISSIN50 · Jun 7, 2006

It's not uncommon to get slightly better milage and slightly better performance from higher octane in 5.0 mustangs - it's counterintuitive to what we know (though not completely surprising given the extremely basic understanding of the dynamics at hand that I and many others have).

I say it matters not - there are too many variables. If higher octane works for someone and they get slightly better milage, keep doing what you're doing or what makes sense. Just MHO.

slocomo · Jun 7, 2006

wytstang said:
Tie a block of wood to the bottom of your gas pedal, this will not allow you to go WOT. Cheap and yet very affetive lol.

haha. I think that's the best advice for this topic.

slocomo · Jun 7, 2006

94-302-vert said:
Dingo, based on that philosophy, why is it that we even have higher octanes, or cars that require it.

Just curious...

I can say that the car seems to run better on 93 than it did on 87, filled it up yesterday. It also seems to be getting better milage without adjusting the timing, hoping ot get a couple tanks of data before i mess with the timing though... I am an engineer and I need my data...

That's cause it burns slower.

slocomo · Jun 7, 2006

mo_dingo said:
Higher octanes were created for turbo/blower cars from the factory. Because they have forced induction, dynamic compression increases which creates a better chance for pre-ignition, like a diesel, combustion w/o spark. Good for diesel, bad for us. Even if you retard the timing on the dizzy of a turbo car, it may still ping on 87 octane. Especially as it gets older, and the O2's get older. That is why Vortech still recommends running 91/93 even with the MSD BTM.

If you are truly getting better gas mileage with 93, I will walk of the plank of a ship at sea w/ my clothes on singing Ricky Martin as I trott.

The true test is to run it with 93 for 3 tanks, never taking the RPM's above 2k, highway driving only. Then remove the fuel tank, and repeat with 87 octane.

But since you commute, you have to do some city driving, which makes for uncontrollable and inconsistent data. Gas from different companies is different. Outside temperature and barometric pressure change. No realistic way to test. And your belief that the car runs better is likely psychosomatic IMHO.
Scott

high octane is made for high compression cars as well from the factory. I work with a guy that has an acura integra gsr. his owners manual calls for at least 90 octane If I'm not mistaken. I just remember he had to use premium cause it was like one point above mid grade.

Increase timing to offset $ of better gas (MPG)?

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