But I was shifting at 7200 rpms not 6600. Sentry and I are trying to figure out if reving that high hurts the motor. We are wondering how many runs that shifting at 7100-7200 rpms you can get. I'm just guessing that it does reduce engine life to some extent. I can not conclusively say that my motor blowing was the result of the higher shift point, but I'm guessing we only have so many redline shifts in the motor.

I am doing some datalogging of my lapping days right now and generally would, if I was still doing it, hit redline about 10 times per lap at my local track. With 25 minute sessions and a 1:25 per lap, I get 15 laps per session. That's 150 redline hits, times 4-5 session per day is 600-750 redline hits per day. I did 13 track days last year, so that equals 7,800-9,750, redline hits a year.

Which do you think would be safer - to drag race your Z 2,500 times in a year or do 13 lapping days at the track? (Equal amounts of redline hits.)
I personally think drag racing is way worse for your motor than tracking it.

 

dragstrip runs are WAY less abuse on the engine than lapping. There is no sustained high rpm and hence no HEAT. Heat is what wears down the engine, not revving. You also never downshift at dragstrip. You can dragstrip a stock engine(properly, without abuse) FOREVER.

2500 dragstrip runs is ~ 600 miles of mild abuse on the engine...

10 track days is 1500 miles of constant abuse

The more you are modified, the higher risk you run of damaging something. I am considering the 7100 rpm L-spec flash too. Trying to figure what kind of extra wear it will be on the engine. But revving to 6600 does NOT affect the life of the engine, constant 6600 rpm maybe. These engine need to be beaten, they are made to be beaten.

My car is modified(crank pulley too), I lap my car(4-5 times year), I dragstrip my car(every week) and I drive hard on the street. My car was even in europe and germany where it was beat for hundreds of miles at constant 130mph +. I have 20Kmiles, engine is running as smooth as silk, virtually no oil consumption, good MPG... I have no reasons to worry, this engine can go on for years, even the way I use it.

 

You mean flywheel? Clutches don't spin (well, the friction surface does I guess). And they're not lightweight.

And yeah, maybe it'd be more like 3000 RPMs, but that's still a big leap. Lightweight drivetrain or not.

About the rev limiter...that's kinda what we're debating. Even with your redline moved up, if you're not making power there, why go?

 

Uh, have you ever double-clutched before? I generally do the "machine gun" downshift 6-5-4-3 or sometimes skip 5, but it works fine. And you could skip all if you want. I don't know if you understand how fast the Tilton revs. The clutch plates + friction surfaces + flywheel are in total less weight than even the stock flywheel OR clutch separately.

It goes like this. Clutch pedal in, shift to neutral, clutch out, rev engine to ____ RPM, clutch in, move lever to gear matching ____ rpm, gas in, and clutch out.

In fact, I think I double clutch every downshift nowadays. I catch myself heel-toeing as I slow to a stop sign even.

 

Hey Vin, you're not in the movies. You have synchros. Double clutching is wasting your time.

Heel-toe downshifting (rev-matching) however, is a good idea.

 

huh, yeah... that's uselss clutch abuse... you are going to kill your clutch twice as fast

synchros where invented for a reason

 

I hear what your saying man and on a stock car you might be right. You can see on that chart, power in 3rd gear and above at redline starts to fall off, mirroring the torque curve of a baseline dyno. You have to take into consideration any i/e you've added to your car have the most dramatic effect right up there in the upper rpm range, extending the need to shift further into the upper rpm range. So stock car=shift at redline, i/e=beyond if you can!

The Tilton is another story altogether...If you have that, you need as much headroom as possible just so you aren't constantly batting the rev limiter.

 

Wow, touched a nerve cause I pointed out your ignorance. Are you telling me that the synchros are designed to spool the difference between 6th and 3rd? Oh, noes, I used my clutch twice to avoid blowing up my transmission.

Nano, why don't you do a fast 6-3 shift at 60 mph without double clutching and then report back how smooth it is. Cause with double clutching, you don't even have to clutch as you move it into 3rd if the intermediate shaft is at the right speed. Additionally, you are not allowed to slip the clutch as you shift either because that puts as much or more wear on it as using it twice.

Anyway, if you're gonna call me VD, get it right first. 1) I'm not talking about double-clutching while upshifting, 2) I didn't say anyone was "granny" shifting, and 3) I didn't say that revving above 7100 will blow the welds on your IM.

Finally, as a parting word, normal people don't leave the Tilton in gear at a stop or in traffic. This comes from the fact that the pedal is pretty darn heavy.

 

I hate to say these things and not have dynos in front of me, but I just find it really hard to believe that an ECU flash alone will make power up to the "raised redline". That's what I've been trying to say from the start.

I'm with you however on the subject of respitory mods, ie. intake, test pipes, cat-back....they will raise your peak HP and torque and most of the time will give you more area under your curves.

I'm a great example of what I'm saying. This weekend, the Alabama G/Z club held a track day at Steele's 1320. Shifting at 6000 RPMs instead of redlining brought my ET down by four tenths. That's a hell of a lot of time. You can either say that I'm making my peak HP at or below 6K, or that by redlining, then shifting, I'm breaking traction. I believe the first to be the case. I gave the same advice to a fellow Z guy who had almost the same results. We both had similar mods. I am unsure if he had an ECU flash or not, however.

 

instead of double clutching, what's the disadvantage of just pushing in the clutch, rev up, downshift, and let the cluch pedal back out again??

seems like it's 2 less steps?

That's how I've been downshifting, but maybe I don't know something?

 

Read before you post. Please. The cure for not knowing isn't posting 5000 messages. Yes, the synchros match your RPMs for you. Is it good for the tranny to downshift three gears? Nope. I never said it was. In fact, I said it was a bad idea. But your double clutching isn't going to save it if you do.

I'll give you this one.

 

Exactly. You're doing it right by leaving out the steps that the synchros do. Still not a good idea though.

 

why isn't it a good idea?

 

Do what you like, but my vote says it's wrong on a couple of levels. First, like we said, rev-matching from 6th at 80mph to 3rd requires a 3000+/- downshift. This takes a lot of time...ok, alright...at least for the majority of us who don't have the Tilton "lightweight clutch". Second, it puts you just about at redline in 3rd gear. Why take the time to downshift to a gear that you'll be shifting out of when you get there? And third, a 6000 RPM clutch engagement at any speed is bad for the friction surface of your clutch. Well, for any stock clutch anyway.

We can bench race all day and all night. How about that first chance we get, we all try this*. Get to 80mph in 6th gear and downshift to 3rd...rev-match...double clutch...whatever. Then, try it again, but this time just go to 4th. It will be hard to tell unless you're really racing someone, but I'm pretty sure that the car will accelerate much faster by doing the latter. If I can honestly say that I feel the car performs better by shifting to 3rd, I'll post back and say so.

*I'm not condoning speeding, racing, or any other irrational use of a motor vehicle.

 

Don't worry Sentry. It is perfectly alright to downshift like that. Almost every main straight on every circuit track ends with cars in 5th gear and requiring a shift to 3rd, then hard on the gas. As long as you rev-match you're good to go. Most everyone I know shifts right into 3rd.


1991tt
I don't think Sentry is asking about downshifting at 80 mph into 3rd? Just how to downshift on the fly.

I've downshifted in to 3rd at 80 many times. I have not had a problem. But then again, I have the Tilton and until recently the ECU flash.

 

I did not know rev-match downshifting was a bad idea.. So why is this?

What exactly is the "proper" way??

 

yeah I think as long as I rev matched, there's no big deal

My car with the tilton and UR pulley rev up really quick so it takes i dunno .2 sec or less to rev up 3000 rpm's

Usually when I'm on the highway and I want to really hit it, I'll shift into 4th gear cause I have the 3.9 final drive and so shifting to 3rd at 80mph is totally pointless cause it'll put me at 6400-6500 ish rpm

I do have the 7100 rev limiter though....

 

I think I'm seeing your point, but I can match the RPMs well enough that the transmission almost "sucks" the lever into gear. With double clutching, the whole transmission is spinning at the correct speed, then rev matching the engine during the shift makes for no shock at all on the drivetrain.

I can see that having the Tilton and the reflash do bias my opinion. Honestly, 60 mph is the top of 2nd for me. I have like 20 mph in 3rd. And, with the way the Tilton works, the lower the gear, the better the effect of less weight is. For example, the reduction in rotational inertia is like 1100 lb in 1st, 600 in 2nd, 300 in 3rd, etc to like 40 lbs in 6th because of the gearing. I could post the formula, but I'd have to dig out the engine book I have.

Being in 3rd is a big deal compared to 4th for this range of speeds. Maybe this weekend I'll get some vids of the tach/speedo for this stuff. Unfortunately, "work" (flying a 6,000 hp, 500 mph jet everyday) takes up most of my time during the week.

 

Ok guys, great to see we're seeing each other's points now. For clarity's sake though:

Ok yes, downshifting on the fly should be accomplished using the rev-match method. As promised, tonight on the interstate I downshifted from 6th to 3rd while going 80mph. Totally useless. I found myself waaaaaay out of my powerband and right about at redline. I wasn't even in 3rd long enough to be WOT and it was time to upshift. You will lose momentum doing this.

The proper way is how sentry65 described. Basically, the goal is to match the revs of the lower gear while shifting out of the higher gear, so as to not drag the clutch. For instance, say you're doing 4000 RPMs in 4th gear. If you were in 3rd at this speed, you'd be around 5200 RPMs. The idea is then to rev to this point while downshifting in hopes of a smooth clutch engagement and smooth power transition. This is a tad more technical than it need be, but it's the "mathmatical" way to explain it. And it is by no means a bad thing at all. My point was that such a huge downshift (6th to 3rd = 3000 RPMs) was not on my to-do list.

This is exactly my situation, with one glaring exception: I don't have the 3.9 final drive nor the ECU flash. After downshifting from 6th to 3rd, I tried a 6th to 4th downshift and the difference was as I expected.

If I'm wrong, then I'm wrong, but double clutching a tranny that has synchros is useless. The synchros automatically do what you're trying to do manually. Rev-matching will reduce drive train shock, but not eliminate it.

 

I'm pretty good at no shock shifting, but I'm also doing the double dance to avoid the wear on the synchros from this big ole shift.