Rev Match downshift v. Normal downshift

[M3Convert]

^+1

Obviously one should achieve a perfect rev-match every time, but would it be better to under rev or over rev when not done perfectly?

Disclaimer: "I think"

I think if you are going to miss, I think it is better to miss higher. If you miss low, you engine brake the rear wheels thus throwing the weight forward. This would do two things to reduce/break rear wheel grip and create oversteer
1) The wheels would be braked and introduce a dimension of braking into the grip profile. The tire can only grip so much, so some of the lateral grip used for cornering would be converted into longitudinal grip for braking, reducing the amount of grip available to turn and creating oversteer. This could either look cool, impress your passenger...or make you the fap-master that ended the session early.

2) The weight is shifted (more) forward, reducing the size of the contact patch, and thus reducing the total amount of rear wheel grip available to follow the front and turn the car

If you are over-revs, you accelerate the car and shift the weight backwards, which doesn't change 1), but may create a better situation for 2). The downside is that you shift weight away from the front, reducing front grip, and creating understeer and probably a missed apex. It requires much more effort to break rear traction with power than with braking, so I believe this is the safer option of the two, although neither is good.

Most of this can be avoided by straight line braking and gear selection before the corner, so the wheels just slides/skids in the direction you are going without introducing rotation. It only becomes a problem if you are trail braking into a corner. It becomes a real problem if you are at the limit of traction...i.e. a very accomplished driver. Most folks aren't a very accomplished driver (i.e. essentially pro, or that guy that passes you 3 times/session in an MX-5 in the advanced group), so they have some latitude with grip levels that results in a missed apex and a slow track-out.

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[vernonator]

Routinely rev-match/blip on downshifts. Smoother ride and easier on the drivetrain. Replacing brake pads is easier and cheaper than replacing a clutch.

This....

 

[MaverickGT]

Disclaimer: "I think"

Thanks for taking the time to share what you think. Good stuff and well thought out.

 

[allgripnoslip]

A follow up question to this. If OP doesn't mind.

What's the maximum rpm you allow your engine to get to downshifting? Engine braking to a stop and downshift for a corner.

As long as it's smooth and below redline then it's all fine. Because going over redline can be harmful I personally will only go to a max of 500rpm's below redline just in case of error but in theory anything below redline is fine.

When coming to a stop, the higher the rpm the larger the engine braking effect is.

When entering a corner smoothness is the real key so you don't upset the chassis.

As far as racing, downshifting should not be used to slow the car down, that's what brakes are for. So the engine braking effect is not important in racing, the goal of downshifting before the corner is so that you can exit the corner in the correct gear. So racing only requires a smooth downshift.

So be smooth and stay below redline.

 

[markmurfie]

As long as it's smooth and below redline then it's all fine. Because going over redline can be harmful I personally will only go to a max of 500rpm's below redline just in case of error but in theory anything below redline is fine.

When coming to a stop, the higher the rpm the larger the engine braking effect is.

When entering a corner smoothness is the real key so you don't upset the chassis.

As far as racing, downshifting should not be used to slow the car down, that's what brakes are for. So the engine braking effect is not important in racing, the goal of downshifting before the corner is so that you can exit the corner in the correct gear. So racing only requires a smooth downshift.

So be smooth and stay below redline.

I Agree. Smooth and as close as possible to redline just not over. passengers have told me I'm going to blow my engine if I go over 4000. usually they notice while going down a steep hill downshifting to maintain speed. Coming to a stop the RPMs drop quick enough that people usually don't notice how high they were up to. Probably sounds like fancy engine revving to the people who don't know whats happening.

The autos don't let you downshift higher than 4500RPM stock. Just wondering if there's a logic behind this. I know my passengers are just judging by the loud noise.

 

[e30og]

Because this is a Mustang forum and we have as much right to post here as anyone else. Don't act like an elitist just because you happen to drive a stick--many of us have owned manuals at some point and know what rev matching is. The S550 automatics rev match for you, even Ford knows how important it is and designs their auto transmissions around the idea.

OK GENIUS.

The thread is asking if you rev match or not on downshift, implying that you must have the choice in the first place! DUH! :headbonk:You admitted yourself that Ford made that decision for you, so why would you answer this thread of whether or not you rev match on the downshift?????

No elitist here, just a victim of a clueless temper tantrum

 

[markmurfie]

OK GENIUS.

The thread is asking if you rev match or not on downshift, implying that you must have the choice in the first place! DUH! :headbonk:You admitted yourself that Ford made that decision for you, so why would you answer this thread of whether or not you rev match on the downshift?????

No elitist here, just a victim of a clueless temper tantrum

If someone driving any manual car asked me about rev matching I would tell them that they should learn it and do it if they are not so already. That's why I would answer this thread. No that doesn't mean I'm going to sign up for every car forum and post the wonders of rev matching. although I can appreciate the not my job attitude. This thread was mixed in with a bunch of others that peaked my interest. The question is about manual transmissions which are not specific to the mustang.:headbonk: Believe it or not some people can drive both an automatic as well as a manual transmission. Just because they are choosing to drive an automatic mustang, for what ever reasons, doesn't invalidate their experience with a manual transmission. Your implication that it does makes you sound like an elitist. At the very least you have a prejudice towards automatic transmissions and I feel sorry for you. They really are not as bad or boring as the majority of the manual elitist make them out to be.
Ford making the autos rev-match for you is just evidence that it should be done in a manual. YES the autos rev-match. It helps with chassis stability as well as clutch pack life. On a down shift the rotational force is coming from the tires so the clutch packs take the direct load just as your manuals clutch would if engine RPM was not synchronized(rev-matched) with output shaft rpm. If the engine RPMs are synchronized prior to engagement the clutches don't have to do the work of accelerating the engine and it can immediately take the force of the vehicle. The engine deals with this force by compressing air, The clutches slip just like brake pads slip. I think it obvious which way causes more rapid and unnecessary wear.
double clutching helps give your manual transmission syncros a longer life by keeping the gears RPM in sync with the clutch rather than the much smaller syncro-rings doing this. There is no equivalent to this in an auto as the autos gears are comprised of clutch packs that directly sync gear RPMs.
I imagine Speedlu's answer is similar from his previous post which you didn't seem to either read or comprehend.

 

[e30og]

My original Auto bashing was directed to comments like this:

Not sure about rev matching but I use the paddles in my auto 90% and almost always downshift because it sounds badass....I've wired the paddles to the point if you listened to my car you would think it's a 6 speed manual.
Another thing I learned about the car is if you want a responsive shift when pulling thru the gears is to turn off the Advance Trac otherwise you can get some serious lag when upshifting in upper RPM's.....

this is 100% unnecessary:

Ford making the autos rev-match for you is...I imagine Speedlu's answer is similar from his previous post which you didn't seem to either read or comprehend.

His original comment was that Ford incorporated rev matching in the autos, which has nothing to do with me bashing auto drivers for replying to this thread

That being said,

If someone driving any manual car ...for what ever reasons, doesn't invalidate their experience with a manual transmission. Your implication that it does makes you sound like an elitist. At the very least you have a prejudice towards automatic transmissions and I feel sorry for you. They really are not as bad or boring as the majority of the manual elitist make them out to be.

I was in the mindframe of S550's only, so this is a very valid point.
Apologies to you sissy automatic converts! :cheers:
I am definitely a manual snob because the thing will be extinct in a very short amount of time

 

[markmurfie]

I am definitely a manual snob because the thing will be extinct in a very short amount of time

I appreciate people like you because if gives people like me choices. :clap2:

 

[e30og]

I appreciate people like you because if gives people like me choices. :clap2:

haha me too! just don't mind my occasional big mouth

 

[SpeedLu]

Driving a manual transmission is not impressive, bro. I've owned several sportscars over the years and most of them have been stick. I don't look down on my fellow auto brothers and you shouldn't either. Your elitism is nauseating and has no place in a community where we all drive these beautiful cars. I could shit on you for driving an Ecoboost because that's the popular thing to do, but I don't make fun of you for not driving a "real" Mustang because I'm not a pretentious snot. Get off your high horse and remember that we all drive Mustangs and we are all car guys. :cheers:

 

[Horsey]

Heal toe initial d style. Kidding. But seriously, i only rev match when i need to speed up or trying to zip around corners

 

[Joe 5.0]

It is amazing how many people I talk to have no idea about rev matching.

I'm not perfect, but I am at the point where I don't always have to look at the RPM's. I'm starting to rev match simply by feel.

 

[cyril185]

Let me reword the question for the auto guys: Do you downshift on your own with the paddles, or do you let the ECU downshift for you?

Sports mode does it for you, Drive doesn't ;)

 

[Sharad]

Five pages in, and I didn't see anyone mention the horrible throttle response these cars have. (that's why I opened the thread in the first place)

I blip the throttle on the downshift when I'm driving aggressively, but it's a PITA in my 2016 5.0. The stock tune is so lazy, when I stab the throttle to rev match, it seems like it takes a year or two to hit the desired RPMs.

I bought the car new and I wanted to keep the stock tune in case I have any warranty issues, but the factory tune is awful. And don't even get me started about the hanging revs between gears!!

Typical event which occurs on a daily basis:

Leave an intersection, squeeze the throttle down in first, WOT in second, 7,000 rpms... "whoops, I'm speeding", clutch it out to coast a little, revs hang around 4500rpms for about three full seconds before it returns to idle... and I want to throat punch a Ford calibration engineer!

Jimmy LaRocca tuned my 2011 5.0, and even with the ProCharger, throttle response was crispy clean.

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