Tune Question - But Different I Hope - Ford Mustang Forum
 
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post #1 of 12 (permalink) Old 12-03-2015 Thread Starter
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Tune Question - But Different I Hope

My 2013 GT is stocked and a DD. My DD is 45 min one way with 25 min on a country road. The country road speed limit is 50 mph and has traffic. While DD I am conscious of rpms (mile per gallon) and like to keep it around 1800 rpm. On the country road I am constantly rowing 5th and 6th to keep around 1800 rpm. While this is fun, sometimes I just want to sip my coffee and suck on a cig. It would be nice to roll the country road in only 5th and maintain approx. 1800 rpm. That said, can a tune help me achieve this? Maybe I am over thinking this and should just roll at 2200 rpm in 5th?!?!

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post #2 of 12 (permalink) Old 12-03-2015
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What's your rear gear ratio?


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post #3 of 12 (permalink) Old 12-04-2015 Thread Starter
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Ah, good question. 3.31
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post #4 of 12 (permalink) Old 12-04-2015
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The only way to change the rpm in any given gear/speed is changing the rear end gear ratio, the internal gear ratios of the tranny and/or changing the overall diameter of your rear tires. A tune will not change the rpms of a given speed in any gear.

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post #5 of 12 (permalink) Old 12-04-2015
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what is stopping you from leaving it in 5th right now?

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Originally Posted by BleednBlue View Post
. . . . Maybe I am over thinking this and should just roll at 2200 rpm in 5th?!?!
Just the RPM? Yeah, you are over thinking it, no problem at all cruising at 2,200 RPM . . . the engine is very happy at that speed, it will sip just a little more gas, but not much

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Last edited by JBert; 12-04-2015 at 02:44 PM.
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post #6 of 12 (permalink) Old 12-04-2015
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Quote:
Originally Posted by BleednBlue View Post
That said, can a tune help me achieve this? Maybe I am over thinking this and should just roll at 2200 rpm in 5th?!?!
No a tune can't change that, just roll at 2200 and don't worry about it.


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post #7 of 12 (permalink) Old 12-04-2015
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As previously noted rpm in any given gear is determined by rear axle ratio, the ratios in the transmission and tire diameter. A tune will alter the engines torque curve and probably increase top end horsepower. IF [ big IF ] the change in the torque curve results in a big increase in low end torque you might be able to stay in 6 th. without lugging the engine, thus avoiding a downshift to 5 th. Of course the tune will almost certainly involve increasing the ignition timing advance which will make the engine more prone to detonation if you do lug the engine. These are relatively small displacement engines that love to rev. RPM is horsepower literally. The formula for horsepower is: horsepower = torque x rpm divided by 5252 [ a constant ]. I agree with others that say let it eat. 2,200 rpm is nothing for these engines.
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post #8 of 12 (permalink) Old 12-04-2015 Thread Starter
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Thanks guys for you responses.
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post #9 of 12 (permalink) Old 12-04-2015
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Like others have said, no problem keeping 2200 in 5th but at those speeds if you wanna save gas I see no problem leaving it in 6th either as long as traffic isn't fluctuating too bad- I'll keep it in 6th right down to 1000 and it'll still be okay on local roads (slow to get going though!)

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Why do you care about running it at 2200 rpm? 6th gear at highway speeds is like 2300rpm.

If your worried about gas mileage then you will see zero noticeable difference between 1800 and 2200 rpm if your maintaining speed. In fact depending on the type of road, hilly vs flat, you might get less gas mileage trying to keep the RPM's low because your making the engine work harder to maintain speed.

The amount of load on the engine is what makes the big difference in gas mileage, not 400 rpm. Your barely above twice the idle speed at that point.

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The FRPP tune might be a little easier to drive at those rpms. But there are other things you can do.


Let the space between you and the car ahead "rubberband" a little and you'll end up being able to use just the throttle to control your speed more of the time.

Question - do you perhaps mean 2200 in 4th as opposed to 1800 in 5th? There's 10 mph difference between 1800 in 5th and 2200 in 5th and the difference in speed (40-ish vs 50-ish) doesn't sound like the question you want answered.

Are you at all opposed to running slightly shorter tires, say, something like 265/40-18?


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I believe it's RPM=MPH X gear ratio X 336 divided by tire diameter
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