Maximum Downshift Question
 

Over the weekend I pulled out my stock 85 MPH Speedometer (pretty crazy!), and am going to ship it out to Helmut at North Hollywood tomorrow to update to 160 MPH. I am also going to have him indicate Maximum Downshift point on the speedo as well. My factory manual indicated the following:

o 1st Gear 36 MPH
o 2nd Gear 63 MPH
o 3rd Gear 95 MPH
o 4th Gear 118 MPH

Ok, now I know I never will downshift into 1st at anywhere near 36, in fact I don't know if I could even shift into first at 5. But has anyone actually downshifted from 3rd into 2nd at 63 MPH!!. Is this safe, and commonly done without worry? I am sure I wouldn't make this a habit, but those are some damn tall numbers!

Looks pretty good to me, seems those speeds coincide with my rev limiter. :D I wouldn't bother with first gear, if your down shifting into first at 36mph, you probable won't be doing it for long.

downshifting to a gear where you will be at the redline does not make any sense, you should be in the power band in the gear you are in. If you are down shifting on the track, and expect to still slow down more before you need the power, just don't let the clutch out until you are at corner entry speed, ideally you should be in a gear that will allow you to be at you best possible position in your power band.

not really an answer to your question,

Jim

You may want to double check your manual. I think the manual says the maximum speed in a gear corresponds to those numbers, but will then probably specify different numbers for maximum downshift speeds.

I know those nembers look like the numbers in my manual, but not for downshift points.

I can't think of any situation where you'd want to downshift into a gear at a speed that close to redline.

Maybe some of the guys who drive track events can be of better help but I would think shift points on a speedo would be distracting (+ I dont think your a looking at your speedo when driving track events). From what I understand (and what I do when I drive) the sound of your exhaust note is the indicator of shift points both up and down. Maybe marks on your tach with bottom and top of power band would be better or a shift light instead of a clock. Just some thoughts from a rookie.



Only if you wanted a new engine.;)

I never watch my speedometer when downshifting. In fact, my last track car didn't have a speedometer, and I never missed it.

Harkens back to the days of VW Beetle and 356 speedos with I, II, III, and IV red marks!

One situation where it might be useful ... coming down Pike's Peak without brakes!

"I never watch my speedometer when downshifting. In fact, my last track car didn't have a speedometer, and I never missed it."

Heck, I never look at the tack on my track car (no speedo) just look for the shift light and listen to the exhaust note.

Jason

So that "would" be coming down Pikes Peak in a VW Beetle.

Regards

Hayden

there's a reason why real sports cars have the Tach in the center of the dash and not the speedo like most common cars....

Yes, who needs the speedometer anyway? Replace it whith something useful like this: :D

http://forums.pelicanparts.com/uploa...1064965274.jpg

yeah, and a jato rocket , to get that dial all the way round to 12G!!!

I agree that speeds can be a distraction and the rev-counter is central for good reasons.
As a generalisation I think those speeds are all about 15-20mph too high as changedown points. I do a lot of 911 driving on roads similar to Pikes Peak including the untarmaced sections (Good practice for hillclimbs as well as fun) and I find there is little point in changing down a gear unless you have at least 2000 rpm left to accelerate in the lower gear.
Exceptions might be to aid braking (no lectures on the pointlessness of engine braking, I've heard it already and I'm too old to change the way I drive) or for greater control in a bend or going down hill - this last I include with reservations: I think, as mentioned by Warren, driving down Pikes Peak with no brakes otherwise you need some revs left for it to be worthwhile changing down.

Post scriptum: I've seen Milu waking up before a hairpin that has to be completed in 2nd and dropping from 5th to 2nd to be at around 6000 in 2nd and go round at a constant 6000rpm, could that be a justifiable usage? - the swine also matches speeds so well that you hear it but don't feel it.
-Isa

Thats the sign of a perfect downshift, heel toed to perfection

I know. He also double declutches and also completes sustained changes like that. I hope Milu misses this thread as I had something nice to say about him;)

i don't see the point to this H&T thing :confused: i guess it's an American thing
i've done car handling courses and none of those even mentioned it..
i do know that double clutching is redundant and doesn't gives any edge over normal clutching with working synchro's

Which car handling courses have you completed?
I believe it is still: part of the UK Police class 1 driver tuition; taught by instructors of the HPC and by some Porsche approved instructors.
Try talking to your instructors, they may tell you they are superfluous, advanced or track only techniques. Master them anyway and then make up your own informed mind:)

slipcourse , handling under rain conditions FWD
then a 2 day racing course at Spa , FWD
and the last one was a drifting course with RWD

Use the brakes to slow the car not the engine.
The car does not care what gear you are in (as long as engine braking is not a factor) during the turn in.

At the end of the straight my attention is aware of my braking and turn in referance points, traffic around me, track condition and preparing to either threshold or trail brake along with car control. It is a critical time to expect to divert my attention to speedo downshift points.

The greatest fear in down shifting is mechanically over reving the engine or locking the rear tires (not good in a corner), perhaps that is what your marks hope to avoid?

svandamme, if you aren't H&T, then what do you do when you get to the end of the straight, need to brake, downshift, and accelerate out of the corner with as little wasted time as possible?

i have very fast feet
i also tap dance :D

Do you downshift during braking or after?

during, my driving instructor has hammered engine braking in my tiny little brain when i was 18... i do admit , that my 911 is a different breed of car ( only had her for 3 months), and it's a lot harder then with my other cars to get things lined up through a corner, but it seems to work out.

edit > for the record that instructor was a friend of the family who had won a bunch of Rally's driving in Group N in 1978 and 1979 so i guess he knew something about it.. ok it wasn't group A or B , but he came first more than once

Heel and toe besides helping the car stay balanced also prevents alot of abuse on the gear box and axles.

There is a reason why the tach is in the center of the dash and not the speedo. I don't ever consider the mph when shifting up or down. I am sure that most of you guys are the same. I watch the tach but just the sound of the engine is usually enough to go on when shifting anyway.

Svandamme: Sorry if I was a bit abrupt. I am surprised h&t, double decluthching etc were not covered. This does not mean they are not valid choices. Nor do I believe they are obligatory for either fast road or competition. I do believe you should learn and master them before deciding to reject them. However, I am not sure how else you could balance engine speed with travelling speed with steering input and then drive smoothly.
Ted: I know that brakes are for braking. But I am past the point of caring what the "book" says is correct. I engine brake, trail brake etc as and when I consider appropriate.
"The car does not care what gear you are in during turn in"? To me that sounds like the logic a proponent of automatic transmissions would offer;) I think being in the right gear and at the right speed before you start turning in is critical. Whatever, if it works for you its fine with me.
There are lots of driving styles and techniques, one checks them out and uses those that feel right for one.

Since we've all got opinions: I don't believe it's possible to drive a car to its maximum capability without being able to downshift smoothly, and (three-footed people aside) it's not possible to downshift smoothly, under braking, without having one foot work two pedals.

For street driving, I honestly don't think it's a very important skill to develop -- since I don't think you should be that close to the limits on public roads.

Amen. A rule of thumb that I always use is that if the inside of your 911 stinks of burning rubber on a public road, you're getting the tires too hot. http://www.pelicanparts.com/support/smileys/wat4.gif

Agreed, my personal opinion, h&t is a necessary skill when going 10/10ths, otherwise it is not possible to go 10/10ths, also part of what sets a cars attitude through a corner is how much you are on/off of the throttle, and being at too low an rpm due to being in too high a gear will affect that. Of course, if you aren't at or very near the limit it's not important.

no worries isabo, i didn't think it was that abrupt at all, i do know double clutching, used to drive a truck without synchro's ( an old army truck we used for hauling stuff around in the familly )
i didn't actually reject the heel and toe thing , i just didn't get it , still don't get it completely as untill now i found the fast foot work fully acceptable and completely good enough for my driving, i don't race on the track, don't drive slow either, but my car is a bit to old and out of shape do start pushing the envelope... yet

it has always been my habit to learn the car before pushing the car, i've seen to many people pushing a newly acquired care before they knew it.. and that's when the car demonstrates it's superiority to the driver... and kills said driver...

my current experience is such that i think that it's extremely important to be at the right speed and gear when you turn in , since it's the safest way to exit the turn at an efficient speed. variation might exist, but for the non professional (sponsored) driver, i think it's not worht risking your car for that minute gain in speed.. no use trying to out brake ones own ego on a public road...you can't win if you do

Vic Elford goes into H&T in great detail in his book "High Performance Driving". He explains why it is essential to drive your car at its limits. That being said, I've spent hours reading that chapter of the book and I still can't do it right. I'll figure it out if I spend enough time on a track.

[QUOTE]Originally posted by Isabo
Ted: I know that brakes are for braking. But I am past the point of caring what the "book" says is correct. I engine brake, trail brake etc as and when I consider appropriate.

Isabo it is very difficult to debate engine braking in a letter.
Are you saying trail braking is done with the engine?
I prefer to be either on the brakes or on the gas but never slowing via engine braking.

What is correct is what works for you, great. Are your non book techniques based on improved lap times? What are your favorite tracks to race at?

1. Perhaps your 911 may have a marginal brake system which has brakes designed for the demands of the street environment. Brakes like these in longer run sessions may fade away at which time you use whatever you can to slow the car for the corners. In that case you certainly do use engine braking to slow the car, but it’s a last resort.
If at threshold braking with good brakes you are using engine braking too perhaps you have a brake bias issue?
If you are engine braking at the end of a straight and your brakes and brake bias are good I expect you may have time to gain in the braking zones.

2. The car at turn in is not depending acceleration, do you brake turn in? But this thought requires the assumption that gears are used to accelerate.

Don’t confuse throttle steer car control techniques such as pitch and catch with my position of not promoting engine braking to slow a car.

Be very carefull engine braking in corners if the road is wet.

Perhaps we should just agree to disagree.SmileWavy

As for the downshift thing - I usually downshift if I want to overtake or pick the right gear for a tight corner. In which case I look at my rev counter and know that down shifting will add about another 1000 revs - if it ends up in the fun bit (3500- 6000) then I'm ok.

[QUOTE]Originally posted by ted

Quote:

Originally posted by Isabo Ted: I know that brakes are for braking. But I am past the point of caring what the "book" says is correct. I engine brake, trail brake etc as and when I consider appropriate. Isabo it is very difficult to debate engine braking in a letter. Are you saying trail braking is done with the engine? I prefer to be either on the brakes or on the gas but never slowing via engine braking. What is correct is what works for you, great. Are your non book techniques based on improved lap times? What are your favorite tracks to race at? 1. Perhaps your 911 may have a marginal brake system which has brakes designed for the demands of the street environment. Brakes like these in longer run sessions may fade away at which time you use whatever you can to slow the car for the corners. In that case you certainly do use engine braking to slow the car, but it’s a last resort. If at threshold braking with good brakes you are using engine braking too perhaps you have a brake bias issue? If you are engine braking at the end of a straight and your brakes and brake bias are good I expect you may have time to gain in the braking zones. 2. The car at turn in is not depending acceleration, do you brake turn in? But this thought requires the assumption that gears are used to accelerate. Don’t confuse throttle steer car control techniques such as pitch and catch with my position of not promoting engine braking to slow a car. Be very carefull engine braking in corners if the road is wet. Perhaps we should just agree to disagree.SmileWavy

I mentioned trail braking with engine braking as some "books", "experts", "instructors" consider them superflous, outdated or wrong. I think trailbraking is more a road than a circuit technique.

I wouldn't describe my driving style or technique as "non-book". I just refuse to be a slave to it. I find that I am faster and smoother when I do it my way. I have driven some circuits you will know such as, Monza, Misano, Brands Hatch, Silverstone and others you probably don't such as Varano, Snetterton and MIRA. This on trackdays and for instruction with cars and motorcycles. My competition experience is with hillclimbs. I'm not much more than a novice but I am not embarassed by my placings and times either. I seem to do best and feel more comfortable when I do it my way.

My car is in excellent shape mechanically even if it looks a bit sad. Basically it's a 71 with mostly SC mechanicals and fibreglass corners. Brakes are fine. But yes I think there is room for improvement when I enter a turn, I'm either braking too early or too late, I'm working at getting this right.

I like to do my braking in a straight line, be in the right gear as I enter a turn and either accelerate through it or go round with a constant throttle.

Engine braking in the wet: my car has about 200bhp, is quite light and fitted with 16X7&9 wheels with slicks (slicks: translation worn out road tyres;))- An excellent way to add to my gray hairs

Agee to disagree? Always cool. But I think if we were discussing this in person with cars and road available we would find that our respective views were not that far apart
SmileWavy
-Isa

I can't imagine driving on a track at 10 tenths and not using H&T. I think on the "average" road racing track not using H&T would cost you possibly 3-4 seconds per lap.

I think that a lot of people that drive "fast" on the street think H&T is not really necessary. If you've never driven in a competitive situation on a track, you've never driven at 10 tenths. You may think you have, you may have even crashed on the street thinking you were, but most likely you haven't.

H&T is different with every model car. On some, it's very easy, on others, it's a very difficult skill to learn. Having used H&T for many years, in lots of different street and track cars, the 911 is by far the most difficult car I've ever driven to H&T. I'm still working to master it, and I think it will be a while. I'm sure having fun learning, however! :D

You would think no H&T would cost time...Perhaps those that don't wait to the last second to downshift. Then releasing the clutch at idle so as not to chirp the rear tires and loose time controlling the car from the momentary rear wheel lock up.

At Big Willow one of the fast guys runs mid 120s and does not heal and toe. He recently also had to replace the transaxle twice in one weekend. Related to no H&T?

Isa it would be thrill to drive on some of the historic tracks you mentioned. Yes in person we might be not as far off. If anything perhaps we both demonstrate the confidece in ourselves required to drive at 10/10ths.
Good luck racing.

It seems that H and T is most applicable for track and "at the limit" driving? I rev-match and drive quite spiritedly...but am not a race driver and have never tracked my car. I am sure it can be taken to a much higher level then mine (Ive never lost the rear end for example)...but its surprising what performance our cars can put out even w/o knowing the racing techniques...