6 sp manual downshifting effect mpg?

Close, but not quite. With the throttle plate blocking the intake, you still save gas and use engine braking on gas engines. Diesel engines are another story, since there is no throttle plate. Diesel controls speed by fuel delivery. Jake/compression brakes contol valves to affect engine braking.

 

They aren't two completely different matters. It's 100% the same concept. You are using the engine to control the speed of the vehicle against momentum and gravity. Decelleration is decelleration regardless of the grade.

Your 10% comment is probably accurate. However it is possible in the Tacoma, I do it all the time. Sure it was an adustment compared to my previous vehicle but after a little getting used to it, I can heel-toe just fine in the truck. I do it to make downshifting a smoother, also similar to driving a racecar, it's makes downshifting for acceleration smoother.

Slowing down is the same thing as controlling forward momentum. Otherwise you would continue to move forward at the same rate of speed or faster if you're on an incline (obviously gravity and wind resistance affect this)

I have personally never spun out of control going down an icy hill, just using that as an example. Gearing down in low traction is not an epic fail, its actually better than using your brakes, there is no risk of locking up. Same concept that ABS accomplishes, which is modulating the brakes to even braking pressure to allow the wheels to continue to spin and to slow you down without locking up.

Anyways no more arguing for me, just based on the comments from others, it appears that you're in the minority here.

So according to people with a scanguage and other AFR monitoring devices, the consensus seems to be that downshifting does save gas over braking in nuetral.

 

It would be miniscule though. In gear, my gauge indicates 1.9-2.0 ms out of 20ms. In neutral, 2.0-2.3 ms out of 20ms. 300 microseconds difference. You'd probably never notice it at the pump. There are too many other variables that would affect it more.

 

hmm..interesting. I wonder if the narrowband sensor vs. wideband sensor has an effect on this.

When I had my wideband it would read "lean" (17:1+ AFR) if I decellerated in gear but if I were in nuetral it read 14.7ish. It wasn't a tacoma though but I doubt for it would be that big of a diff. Most cars idle at 14.7 (stoich)

 

That's what I was just going to say. The injectors shut off when you're 'coasting' while still in a gear.

I usually don't down shift until I know the rpm's are going to be 2.5k or below though.

 

Well, since you're a genius, I won't bother pointing out the ridiculous innaccuracies in your post.
No, I can't ignor them.
number one, you can't shift into second from 70mph.
Number two, you don't even know what a Formula Ford is, let alone posess the intelligence to know whether it's a POS or not...I'm pretty sure you've never driven a non-syncro close ratio 4spd.
Number 3, use some of that genius to show us your calculations for saving 'A TON' of gas.
301.783 gals?
329.326 gals?
I'll leave that question to the genius...bet you can't or won't figure out the what I'm even referring to.
4...I hypermile my 6sp...never rev over 2k except driving on the freeway where the pathetic 6th gear requires 2.4k rpm to maintain freeway speed.
thanks for our insight and wisdom....look forward to your response.
sorry for the hijack.
some people can't figure out the difference between deceleration and maintaining control of forward motion using engine compression.
BUT THEY'RE GENIUSES!

 

I'll help you with the difference between deceleration and maintaining downhill speed.....deceleration means your velocity decreases, maintaining downhill speed means your velocity remains constant.
There, see?
In re using engine compression to ease down an icy hill, stop fooling yourself into thinking you have better control using engine compression, you can't modulate the inputs as precisely as you can pressure on the braking system.
I learned this 30 years ago before ABS was prevalent.

 

I've been driving a manual for 16 years. I put nearly 300,000 miles on 2 vehicles. I replaced 1 clutch. My 1st Gen taco had 196,000 miles (i put on the last 116,000 miles) on it when i traded it in, and still had very strong original clutch in it. I downshifted all the time. It was just part of how i drove the vehicle. IF you know how to drive a manual, downshifting doesn't cause any extra wear on the transmission or clutch.

Downshifting shouldn't waste anymore fuel. If it uses extra fuel, it shouldn't be enough to make you lose 2-3 mpg. The fuel injectors shouldn't be pumping out much fuel while you are out of the throttle.

If your getting bad gas mileage, change the way you drive. Easy on the gas, shift early, don't drive over 60 mph. Start with that and see where it gets you.

 

Until they come up with a commercially available full rotor contact pad, engine braking trumps brakes. Brakes will lock long before you lose traction with the road, it's just the nature of the beast.
ABS corrects problems caused by the average driver. A good/expert driver can out-brake ABS every time.

 

It's the same principle with engine braking whether you're going downhill or running on a straightaway. The reason the speed stays constant going downhill is because there is extra force (gravity) being applied. Without the extra force, the vehicle would slow.

A particular gear is only going to allow the truck to go so fast without extra fuel input. The gear that keeps the vehicle at say 20mph downhill is also going to slow a vehicle to 20mph on a straightaway and it will do it much faster than letting it coast. The point is that the engine is doing it.

 

x2^^^

 

True. The throttle plate will not completely stop the flow of air. The throttle plate stop screw is what sets idle on carbs. It still offers a great deal of restriction, thus engine braking. A carb will not give you the control of fuel injection, and will constantly be fueling the engine regardless of speed.
If you put the trans in neutral on a carb engine, you save gas, but lose engine braking.

I'm unsure of the point you are trying to make. We seem to be in agreement.

 

I'm going to just avoid all of the crap you spewed afterwards, and rehash what everyone else has said because I can.

Downshifting slows you. Your assertion is provably false. Go 40mph, then downshift to second. Then, go 40mph and go to neutral. You will slow faster in second, period.

Whether it saves fuel is dependent on the automobile design. As others have mentioned, if the designers allowed for fuel shutoff while coasting in gear as the wheels drive the engine to turn over (which a source on this forum, I can't be bothered to search where, indicated that they did), then it is possible that it will save some fuel over coasting in neutral.

Make your Tacoma a Prius? No. Good idea to do? Up to you. But does any of that make it untrue? Absolutely not.

Shut the fuck up.

 

Thanks...I spewed coffee out of my nose.
Are you all so obtuse as to think I don't know what my 6speed Taco does when I let off the gas?
Apparently so.
Thanks for the education.
For those of you experts that think using the gearbox and clutch to slow your car is an effective use of the machinery, keep going. Your repair shop thanks you.
In re Formula Ford=POS, you lack the intelligence to know what you don't know.
I love you idiots.

 

Effective? Arguable. Does it work? Yes Did you say it doesn't and then call all of us idiots for saying that it does, when it in fact does? Absolutely.

 

210k Miles on my 5spd Honda Accord I owned before my Tacoma, no clutch problems.
87k on my 6spd Tacoma to date...no clutch problems.

 

Also, apparently you DON'T know what your 6speed taco does when you let off the gas! Keep up the attitude, really works well for you, jackass.

 

Hey, No name calling! Poopoo head

 

Yeah, you're right. Hard not to get annoyed at people whose undeserved arrogance makes me of all people look humble, especially when they're not only arrogant even whilst not being that smart or wonderful as people, but also happen to be wrong while simultaneously calling other people stupid.

Not that I'm talking about anybody in particular, here.