ADUK Archive

I must admit I have to grit my teeth when in my car with someone driving who thinks it's "cool" to rev it to 6500 rpm in every gear because they like the noise. Personally I stay well clear of this most of the time. There's enough torque that a change up rarely diminishes the acceleration available. YMMV.

Mr Cholmondeley-Warner wrote:I must admit I have to grit my teeth when in my car with someone driving who thinks it's "cool" to rev it to 6500 rpm in every gear because they like the noise. Personally I stay well clear of this most of the time. There's enough torque that a change up rarely diminishes the acceleration available. YMMV.

+1

My experience is that there is very little need to red line in 1st. 2nd and 3rd maybe red line in overtaking to avoid mid-manoeuvre gear change. Red-lining in 4th, 5th or 6th means highly legal speed in most cars.

Garrison wrote:Red-lining in 4th, 5th or 6th means highly legal speed in most cars.

Most car's will slow down if you shift from the redline of 5 to 6th. There's more power at the top of 5th than ~2000 rev/min lower down in 6th so you end up with not enough power to overcome the aero and you slow down until they equalise. I think on the 8 speed autos Vmax is usually in 6th. Not that any of this actually matters in the real world - and I'm wondering why I wrote this

StressedDave wrote:Because it's interesting...

What is?

Mr Cholmondeley-Warner wrote:I must admit I have to grit my teeth when in my car with someone driving who thinks it's "cool" to rev it to 6500 rpm in every gear because they like the noise. Personally I stay well clear of this most of the time. There's enough torque that a change up rarely diminishes the acceleration available. YMMV.

So, what arbitrary rev limit are you happy with, and why?

When I want decent acceleration, i.e. not every time I set off from the lights, I'll happily do this to my own car, although not in first gear. Why wouldn't I? If anything, the Italian Tuneup does it some good.

Garrison wrote:

RobC wrote:I was put of buying a 911 after speaking to people about intermediate shaft, cylinder cracking and catastrophic engine failure and £10K engine rebuilds as well as rear main oil seal problems and bought a Mercedes SL instead.

I know that all modern cars have ECUs that store fault codes, however would the Volvo V50s diesels ECU pick up the same things as a 911?

Regarding 996/997 Carrera engines, unfortunately they can be liable to bore scoring, intermediate shaft (IMS) failure and oil leaks. U.S. Class Action request for disclosure indicated the failure rate which requires a new engine is c.5% of all cars under Porsche warranty in the U.S.

Fortunately, the repair would only be c.£10K as you said. The Mezger engine in mine would be £39K + fittings, although it does not suffer bore scoring, IMS, etc. and the failure rate is almost nonexistent for stock cars. The X50 engine is in excess of £43K and I think the GT2 engine is north of £50K. The failure mode has been the engine throwing its timing chains after the over-rev, but I don't know whether the damage was caused by the chains or crank or rod or camshaft side.

Hi Garrrison

I know all cars have faults and that the 911 is a supercar, it just that for me any driving pleasure would be ruined by the thought of a £10K engine rebuild, never mind a £43K or £50K engine rebuild1

Rob

RobC wrote:I know all cars have faults and that the 911 is a supercar, it just that for me any driving pleasure would be ruined by the thought of a £10K engine rebuild, never mind a £43K or £50K engine rebuild1

Rob

That's exactly my feeling. For those who can afford it and are happy to spend that sort of money, and enjoy that style of motoring, good luck to them. There's just no way it would be worth it to me.

In truth I'm still enjoying most of my motoring, but it's very much at bargain basement level, as befits a poor OAP.

Best wishes all,
Dave.

I often change from first to 4th which I would do about 20 mph, but would not normally hold first beyond 30 mph.

So I did a little experimenting today when the Aston was fully warmed and on a quiet road. Peak power is 6.5k, red line is 6.75k (except there isn't a red line on the rev counter, there is supposed to be a flashing red light but I am too sympathetic to know what it looks like) and rev limiter is 7k - all according to the manual, which may be wrong about this as it is about various other things!

When using lots of performance I would normally be quite happy to change up from 2nd to 3rd at 6k, but would normally change up much earlier from 1st to 2nd. Today I experimented by accelerating to 6k in 1st, and saw a little over 40 on the speedo. From there it was easy to make a slow smooth change to 4th and that would work wonders for a traffic light GP in a 40 mph limit. However, I found it disappointingly difficult to make a smooth change from 1st to 2nd at 6k for continued hard acceleration.

The revs drop more quickly in higher rev ranges than in lower ones, so normally high rev gear changes are quicker than low rev changes even though the revs have further to fall.

RobC wrote:

Garrison wrote:

RobC wrote:I was put of buying a 911 after speaking to people about intermediate shaft, cylinder cracking and catastrophic engine failure and £10K engine rebuilds as well as rear main oil seal problems and bought a Mercedes SL instead.

I know that all modern cars have ECUs that store fault codes, however would the Volvo V50s diesels ECU pick up the same things as a 911?

Regarding 996/997 Carrera engines, unfortunately they can be liable to bore scoring, intermediate shaft (IMS) failure and oil leaks. U.S. Class Action request for disclosure indicated the failure rate which requires a new engine is c.5% of all cars under Porsche warranty in the U.S.

Fortunately, the repair would only be c.£10K as you said. The Mezger engine in mine would be £39K + fittings, although it does not suffer bore scoring, IMS, etc. and the failure rate is almost nonexistent for stock cars. The X50 engine is in excess of £43K and I think the GT2 engine is north of £50K. The failure mode has been the engine throwing its timing chains after the over-rev, but I don't know whether the damage was caused by the chains or crank or rod or camshaft side.

Hi Garrrison

I know all cars have faults and that the 911 is a supercar, it just that for me any driving pleasure would be ruined by the thought of a £10K engine rebuild, never mind a £43K or £50K engine rebuild1

Rob

Not a problem for buyers of new cars, who would take an extended warranty on expiry of the manufacturers warranty. Buyers of older expensive cars have to realise that what they save in depreciation may cost them in repairs.

PS - I did not extend the warranty of my car when the factory warranty expired recently. I won't be happy if I have to fork out for a very expensive failure, but I can afford it and I know warranties are priced to make money for the insurers.

Garrison wrote:

Silk wrote:

Garrison wrote:The fact that the engine can/may register over-revs will 1) render the car pretty much unsaleable, as well as 2) might reduce its resale value noticeably.

I don't understand. Are you saying that a record is kept somewhere that the engine has been over-rev'd and a future purchaser can find out? I'm not sure how this makes a car unsaleable.

All Mezger Porsche engine (GT1, GT2, GT3 and Turbo), although immensely strong, are liability to give terminal failure if it has been over-rev. Most likely happened on missed down shift or you spin out with your throttle open wide-ish.

Garrison, given that Mezger engined GT3's have a rev limit of 9k, what is it that would fail in the Turbo if you go over your much lower rev limit?

All I know is I've rarely needed to exceed 3000 rpm in the Yeti, and have never gone over 4000 rpm (redline is 5000 rpm)

While the engine is cold, I generally change up around 2k rpm because the engine doesn't like being revved at all while cold, but when it's warmed up, I tend to hold gears until 3k rpm because I find that when I change up at that point, from 1st to 2nd, and 2nd to 3rd, the revs for the gear above are just above 1.5k rpm (below which there's zero power and a horrible vibration in any gear above 2nd), and for 3rd to 4th, and 4th to 5th changes, the revs end up just above the bottom of turbo range (around 2k rpm), so you still get good acceleration.

While I was learning in the petrol-powered cars, I found I would change up very early, as there was still power low down in the rev range, but the diesel Yeti seems to dislike low revs, preferring the mid-range (which doesn't quite make sense, but hey).

It's a Greenline 1.6 diesel if anyone has any idea why that's the case

But back to gear-shifting, I find that the 1st to 2nd change is quite smooth if I either get the car moving, and change into 2nd before 2k, or if I rev it up above 3.5k so that the revs in 2nd are above 2k.

Just my £0.02's worth

TheInsanity1234 wrote:While I was learning in the petrol-powered cars, I found I would change up very early, as there was still power low down in the rev range, but the diesel Yeti seems to dislike low revs, preferring the mid-range (which doesn't quite make sense, but hey).

It's a Greenline 1.6 diesel if anyone has any idea why that's the case

It's the same engine as I had in my second Ocatavia. It loved high revs. It was in complete contrast to the engine in the one I had before (2.0 PD). The newer VAG CR diesel engines produce peak power near to the top of the rev range and are much more petrol-like in that respect. They're fantastic engines. The 2.0 170 in my A3 was amazing - I used to rev the bollocks off it on a daily basis and it didn't seem to do it any harm. I contrast, my 1.6D PUG is much more sedate and prefers lower revs.

trashbat wrote:So, what arbitrary rev limit are you happy with, and why?

I generally use up to about 5500 out of the available 7200. While the oil's not up to temperature, I limit myself to 4000. There's little benefit in wringing the last few revs out of the engine, and to my rear end, it feels happier not bothering. However some other drivers seem to like the noise and don't hear the harshness that creeps in at this stage.

I do sometimes use more, for example on some overtakes where I don't want to change up half way, but just doing it for the sake of it, for example when turning out of a junction with no following traffic, grates on my ear, for some reason, when I'm the passenger. My engine is not as expensive as Garrison's, although it's from the same stable and vintage, but I would still rather not have to have it rebuilt, or replaced.

Mr Cholmondeley-Warner wrote:I do sometimes use more, for example on some overtakes where I don't want to change up half way, but just doing it for the sake of it, for example when turning out of a junction with no following traffic, grates on my ear, for some reason, when I'm the passenger. My engine is not as expensive as Garrison's, although it's from the same stable and vintage, but I would still rather not have to have it rebuilt, or replaced.

So do you believe that using 6,000 rpm would damage your engine? I don't believe that. I dislike use of high revs when high performance is not required, but I think it is entirely reasonable to take advantage of the performance potential of a car including use of the rev range up to max power. Whether or not I choose to use the top end of the rev range in a particular car depends on the cars characteristics. I recall that you drove my M3; that car had a top end which I found thrilling, and was at its superb best between 6k and 8k revs. I recently drove a (replacement model) M4 - in that the red line is set at 7k, but holding a lower gear to 7k did not feel rewarding, either aurally or in terms of the rate of acceleration, so I don't suppose I would use high revs in that model nearly as often.

Nick, if I ever have the pleasure of driving your car, please remember to brief me on how you like it to be treated. I am happy for any car of mine to be taken up to say 500 rpm shy of the red line.

waremark wrote:Garrison, given that Mezger engined GT3's have a rev limit of 9k, what is it that would fail in the Turbo if you go over your much lower rev limit?

Although the block of the Mezger engine is shared between different models, the internal are all slightly different. For example, the GT3 has forged titanium con rods whereas the GT2 and Turbo does not. Also, according to Nine Excellence who looks after my car and also tune 996 Turbos for vmax, the K16/K24 turbos start to lose efficiency beyond 6,000 rpm so I guess there is no reason to fit parts for 9,000 rpm rev limit if that particular engine (Turbo/X50/GT2) cannot deliver output at that high revs anyway. I am not totally knowledgeable on the differences but it is the differences which partly dictate the parts used and therefore the limiter.