Hi All;

I was wondering if there is data anywhere which displays the RPM/Speed for each gear (M/T). The reason I ask, is that I am trying to determine wether or not I may have overreved the engine. Here's the story:
- I was cruising on 6th @ around 85-90 MPH (RPM was probably around 4k)
- Pressed on the clutch then the gas to rev-match to 4th gear (RPM around 6k)
- Shifted to 4th, at which point the tach reached past 7K (maybe around 7500-7700 @ 85MPH) and was still climbing
- Saw the tach at redline and quickly switched back to 6th ...

Question is, those numbers 4th @ 7500RPM and 85 MPH, while approximate do not sound right to me. Did I accidentally mis-shifted to 2nd gear and not 4th? What would be an estimated RPM for 4th running at 85 MPH?

With all the overrevs and mis-shifts I have heard/read about, I am paranoid about whether or not I damaged the engine.


Thoughts?

 

Forgot to mention - car is a stock 2006.

 

not sure but would guess somewhere in the 4-5k range 85mph in fourth. and if you accidentally went to 2nd you would have gone to alot more then 7500rpm and it would happen really fast.

if the car feels fine and everything seems ok. then it probably is ok. I think you would know right away if you broke something?

 

Haven't noticed anything wrong with the car yet.

How about this, how many MPH can we reach with gear 2 when it hits redline?

 

Don't know if this helps or not, but I KNOW for a fact that on my auto at 90mph-95mph, my tach is at 3k RPM, so I can't imagine that on your MT, you're at 4k at 85-90mph. I'm driving a 2006.

 

If you were going 85-90 you'd come close to redline in 4th, but if you flew past it briefly before pressing the clutch back in you must have shifted into 2nd by accident.

Someone named DarkLava came up with this
Redline Speeds

Gear Speed @ 7100RPM (mph)
1 34
2 59
3 82
4 108
5 134
6 169

Then someone named tide posted this

1st - 35
2nd - 60
3rd - 81
4th - 110
5th - i dont know
6th - i would have died... not enough road haha

 

Thanks Wackura. It must have definitely been second then. Crap, that's much worse than if I had gone to fourth

 

If nothing broke on the spot then I think it's ok. No broken rods or anything.

 

Try changing your hold on the stick shift when you shift...

Hold it from the right when you want the 1st-2nd plane, put your hand on it from the top when you want the 3rd-4th plane, and hold it back-handed (hand on the left of the stick) when you want the 5th-6th plane. You'll never drop it into 2nd when you want 4th if you make this small change...

BTW, you'd know if you damaged something already... on a severe overrev, rods or valvetrains get damaged and the engine will either stop, or sound like crap right away... try the technique and let us know if it works for you!

 

Thanks Chrisman. I will definitely give this a try. I hope that both you and wackura are right and that nothing is damaged.

 

You never know for sure. If it didn't go past redline and bounce off beyond what the tach is numbered it should be ok. But bent rods are a ticking time bomb, everything seems ok but one day your rod bearings could fail out of nowhere.

 

I don't think it went over what the tach display is limited to (which is 8k). If I remember correctly, it was around 7700 when I hit the clutch and changed the gear back to 6th.

If the motor does blow after a few thousand miles, does anyone know if Acura will cover it under warranty? I'm guessing, "no," specially since Acura can see the history of RPMs generated by the car (as it is tracked), right?

 

Don't skip-shift, it's hard on the trans. Not to mention the increased likelihood of over-reving.

http://www.in.honda.com/Rjanisis/pubs/SN/B060100.PDF

 

Hmmm. I don't shift from 1st to 3rd during exceleration, that this would be bad seems like common sense, but when coming to a stop from a high gear I don't shift into each gear on the way back down, that would be impractical much of the time. The only time I skip gears during acceleration is if I'm doing 70 mph in 3rd and am ready to shift into overdrive at which point 4th and 5th are lower gears than what I desire. I'll have to look more into this to figure out how harmful that might be. I drove a '91 teg this way for years and never had a problem.

 

It's only bad to skip gears if you're going to keep accelerating after the shift (i.e. 1st to 3rd, while accelerating is bad). If you've reached your cruising speed (say 65mph) in third gear and shift it into 6th, while maintaining that speed, there should be absolutely no problems with the synchros.

 

Well, it's kind of hard to "put your hand on it from the top" when downshifting 6-4, but otherwise this is sound info.

The shifter has a fairly strong tendency to want to "center" itself on the 3-4 plane if you aren't pushing to either side, so I just pop it out of 6th and release it for a split-second -- it will naturally center over 4 -- and then push down from the top as Chrisman suggested.

 

Here are speed calculations for my 2006 MT. The gear ratios
are from the 2006 TSX sales literature. Note that the published
ratios are to only three significant figures so accuracy
could be improved by counting gear teeth. But since my tire
measurement is also to three significant figures the calcs
are pretty close. Also note that the speeds are actual, not
indicated - your speedometer and tachometer are not that accurate.
I've separated the three columns with semi-colons because the forum
absorbs spaces and tabs.

gear;gear ratio;speed in mph at 7100 rpm with a 78.1" circumference tire

1;3.27;33.7
2;1.88;56.4
3;1.36;81.1
4;1.03;107
5;0.83;133
6;0.66;167

diff ratio = 4.76

 

Thanks for the info. Having the addition of gear ratios is a plus.

Man I still can't believe I did that.

 

Curious if this is true with heel-toe shifting or other types of rev-matching?

I knew the syncs allowed for the gears to mesh without grinding but never thought about it in real terms - i.e. they must speed up or slow down the input shaft to allow clean tooth meshing.

Interesting that the service flier says "Skip shifting, though, is really brutal on synchronizers; it puts a higher demand on them than they were designed to take."... I would think that multi-gear changes would be common for down shifting for passing, especially since the gearbox is "spaced close together so you can keep the engine speed in its optimum range for max power and acceleration"... but our car isn't designed for this? What, are we supposed to row from 6th to 5th to 4th (or even, to 3rd), in order, if we want to downshift?

 

I believe the reason for rev-matching is exactly to avoid additional pressure to the synchros.

 

There is no way I'm going to walk down the gears sequentialy when down shifting. If the car falls apart the so be it, but I somehow doubt it will.

 

I understand what the Honda bulletin is trying say, but it IS possible to skip gears as long as you match revs for the gear you are going into. Example: You have accelerated to 50 mph in fourth and just want to cruise there. If you make the shift from fourth to sixth matching the revs to say 2200, the shifter will easily drop into gear with no excess wear on the synchros. With a little practice watching the tach you can get the hang of it. The trick is to not be ham-fisted but feel what the tranny is telling you. When upshifting a slight pause in neutral with your foot off the gas will get the engine revs low enough that the stick will just drop into gear with no help from the synchros at all. Look at post 17 and
you'll see how much rev drop there is from first to second - if you rev to 7100 and
power shift to second you'll be at about 4200 rpm. The second gear synchro had to scrub off about 3000 revs to make the 1-> 2 shift, and that's the synchro that takes the biggest beating even in normal usage.

 

NO. Rev-matching is for minimizing wear on the clutch. If you want to minimize wear on the synchros, you have to double clutch.

If you are upshifting and want to go from 1st to 3rd, you can shift from 1st to neutral and then wait a while for the input shaft speed to drop before shifting it into 3rd. There is no indication for input shaft speed as it is not matched to the tacho when you are pressing the clutch down, so you have to go by gut feel.

For downshifting, say from 5th to 2nd, you go into neutral, release the clutch, blip the throttle to the revs suitable for 2nd, get it into 2nd gear, blip once more to rev match and release the clutch.

 

Interesting. I just blip the throttle once before going into gear, then I release the clutch. If blipping it a second time (after moving to the gear), then releasing the clutch helps my synchros, then I will do this. Thanks for the tip.

 

What? Synchronizers are the specific reason why we do not need to double clutch. There is absolutely no point to double clutching in a car that has synchronization gears.

I think what Honda is trying to say in that document is that you shouldn't be trying to accelerate and skip gears. For example, you shouldn't go from first to fourth from a stop as the RPM drop can cause some lugging and/or a stall. However, going from say third to fifth (and allowing the RPM to drop somewhat before shifting into fifth) is fine since the engine RPM and drive shaft RPM are fairly close. Rev matching is too complicated to explain to the layman so they just tell everyone not to do it. Anyone else with me on this interpretation?

As for the original post...if it didn't smell like burnt swiss cheese for a half an hour and you car can still shift normally, you should be fine. No car would last long on the road if the transmission croaked the first time you missed a shift.

 

The tranny is fine. I am more worried about the engine.

 

Nono, the first time, you are meant to blip when your gear is in neutral and your clutch is released. Doing this first blip before putting it into gear is what minimizes synchro wear. The second blip is to minimize clutch wear.

 

There is no point double clutching if you are going 1 -> 2 -> 3 -> 4 -> 5 ->6 and back down through all gears. But if you were going from 5 -> 2 like in my example, that causes accelerated wear on the synchros and you'd do best to double clutch. Even when trying to go into 1st at any speed other than 0mph, double clutching will stop the loud banging sound which is the synchros speeding up the input shaft when you try to muscle it into 1st.


Rev matching is complicated? That just involves blipping the throttle once before releasing the clutch. How complicated can that be? Double clutching is the one that is complicated.

 

Of course when upshifting from 3rd to 5th or 2nd to 5th, there is no point double clutching as all you need to do is wait a second or two while the shifter is in neutral before putting it into the next gear. That little bit of time in neutral lets the input shaft slow down to a closer RPM that is needed for 5th gear.