Why won't engine won't rev out! (Newbie)

[HoppyUK]

Hoping you can help a newbie

No matter what mode the Tiptronic is in, it always changes up at around 6,700-6,800rpm. This is quite some way below the 7,000rpm red line, which is where Audi specs promise me I have 344PS peak power, and miles short of the 7,200rpm limiter (that I can reach by revving carefully in neutral).

I'm not happy about this, and so far Audi has not been able to explain it. I am being robbed of both rev range and power, which I have paid for and expect.

Everything about the car is fine, and I really like it, but this is bugging me. It might be hypothetical 90% of the time, but I want the performance Audi has promised. They might as well claim that the S4 gives 400bhp at 8,000rpm but sorry, the engine won't rev that far

Other Audi owners I know, including autos, have no trouble revving to the red line, and the manual versions go right to the limiter of course. But I've not heard from any other S4 owners so I don't know if this is just my car or that all S4 Tiptos are the same.

Can you guys kindly tell me about your cars? Where is the red line marked and where does your Tiptronic box change up? Mine always changes at 6,700-6,800rpm, even in manual mode, or in sport with kick-down. Do manual cars rev right to the limiter?

Many thanks,

Richard

[tweek]

I suspect this is a gearbox limitation, you maybe able to get the software changed to allow it change at a higher rpm. I have a manual B7 S4 and this revs right the way up, limiter is approx 7250rpm, anyway its the torque that makes the car go and the max torque is achieved much lower down the rev range so no need to max out the revs IMHO..

Pete

[HoppyUK]

I suspect this is a gearbox limitation, you maybe able to get the software changed to allow it change at a higher rpm. I have a manual B7 S4 and this revs right the way up, limiter is approx 7250rpm, anyway its the torque that makes the car go and the max torque is achieved much lower down the rev range so no need to max out the revs IMHO..

Pete

Thanks very much Pete So manuals will go all the way to the limiter, as I suspected? I assume your red line is also at 7k? And I wonder what it says in your handbook - mine has various illustrations showing the red line at either 6,500rpm or 6,700rpm. Brochure produced when the car was new shows the red line at 7k, and there is also a bhp/torque graph which clearly shows the engine revving to 7,200rpm.

So what is going on here? Every (manual) car I have ever owned is always red lined a bit higher than peak power, and the limiter set a bit higher still. This is as it should be I think, and I know from a friend's RS4 that his car produces peak power at 7,800rpm, is red lined at 8,000rpm, and hits the limiter at 8,200rpm.

Like me, he is not keen on the idea of his car being artificially limited to 7,500rpm, which is effectively what I am getting. RS4 owners would be furious.

To my mind, if peak power is at 7,000rpm, then I would expect the red line to be at 7,200rpm and the limiter at 7,400rpm (in line with the RS4 and most other cars). This would allow full access to the engine's power. Nowhere is it stated that automatics are less powerful - yes they weigh a bit more, accellerate slower through transmission losses (on non-dual-clutch versions) and use more fuel. That is normal, clearly stated and understood. But power output should be the same, and on my car it is not.

My cycnical mind can only come up with one explanation for this - there is a reliability issue, particularly with the gearbox at higher revs, and I don't think the 5-valve head likes it much, either, which is why the higher revving RS4 only has 4-valves.

Audi has dithered about how to best manage this. So they have decided to cut the revs artifically on auto cars, figuring that it is cheaper to re-programme cars from the few people like me that complain, than to get hit with the warranty claims from everyone else.

On manual cars, they are obliged to take the risk but they have still put the red line lower than where you should expect it, and the limiter also. Note that there are not nearly so many manual S4 cars on the roads - there are only seven S4 for sale on the official Audi website right now, and all are autos.

Of course, the most sensible thing to do would be to fit the engine from the A8 which although it has 10bhp less at 6,500rpm, has 20lbs-ft more torque. I would go for that! But that would not give Audi the headline number that they want, ie BMW M3 (E46) 343PS, S4 344PS

Any more input from you guys very gratefully appreciated.

Thanks,

Richard.

[tweek]

Richard,

The red line is also at 7k rpm and the limiter is a little higher, the limiter is there to help prevent engine damage due to over-revving and you have already stated your engine does rev upto the limiter in neutral. In this case I would consider that your engine does perform as per spec and the issues you have are related to limitations with the tiptronic transmission.

I am curious as to why you have bought a vehicle with automatic transmission if making use of every ounce of the engine's performance is a high priority, auto boxes depending upon design are slower, absorb more power etc than manual gearboxes but provide a smoother ride. With regard to your comment about limiting revs based on reliability issues, I doubt very much the small difference in HP available between 6800rpm and 7000rpm would affect the reliability of the engine or gearbox as I think peak engine torque would be the dominant consideration for the strength of the gearbox.

The RS4 engine is a very different engine to the S4 and cannot be compared like for like, the RS4 engine has 32 valves because FSI technology is used and 1 valve per cylinder was sacrificed for this purpose, I think it is impressive that a V8 can actually rev to over 7000 rpm in a road car.

As for Audi's response, this may sound brutal but get used to it, it won't change.

Pete

[HoppyUK]

Richard,

The red line is also at 7k rpm and the limiter is a little higher, the limiter is there to help prevent engine damage due to over-revving and you have already stated your engine does rev upto the limiter in neutral. In this case I would consider that your engine does perform as per spec and the issues you have are related to limitations with the tiptronic transmission.

I am curious as to why you have bought a vehicle with automatic transmission if making use of every ounce of the engine's performance is a high priority, auto boxes depending upon design are slower, absorb more power etc than manual gearboxes but provide a smoother ride. With regard to your comment about limiting revs based on reliability issues, I doubt very much the small difference in HP available between 6800rpm and 7000rpm would affect the reliability of the engine or gearbox as I think peak engine torque would be the dominant consideration for the strength of the gearbox.

The RS4 engine is a very different engine to the S4 and cannot be compared like for like, the RS4 engine has 32 valves because FSI technology is used and 1 valve per cylinder was sacrificed for this purpose, I think it is impressive that a V8 can actually rev to over 7000 rpm in a road car.

As for Audi's response, this may sound brutal but get used to it, it won't change.

Pete

Pete thanks for that. I understand eveything your're saying, even if I don't like your conclusion

I bought an automatic because I've wanted one for a while and the TT I recently bought for my wife, with the wonderful dual-clutch S-Tiptronic auto, not only revs well past peak power, it doesn't change up until the red line. And a friend's A8 auto with a very similar motor to mine, also revs well past peak power and even slightly into the red before shifting (but it peaks 500rpm lower). It never occurred to me when buying that an automatic thast it wouldn't even reach peak power - it's not the done thing to bounce a test drive car off the limiter in all gearbox modes! And it wouldn't have been safe on the day and place I drove it.

Yes, gearboxes generally don't like big torque, but Audi Tiptronic boxes are no strangers to torque so I don't think that should be an issue. However, I don't know of any other slush-box autos that rev as high as an S4 which is why I'm making that connection. There are plenty of V8s that rev high though - no reason why they shouldn't. The RS4 obviously, and the new M3. I also note that BMW makes a fuss about how their new dual-clutch gearbox can handle high revs...

But my funadmental question remains. The S4 produces peak power at 7,000rpm, which on the evidence of every other car I am aware of, would suggest a red line around 7,200rpm (not 7,000rpm), and a limiter at maybe 7,400rpm (not 7,200rpm). This clearly isn't happening, even with manual cars. And on my automatic, it will not rev beyond 6,800rpm, ever, and often changes at 6,700rpm. In other words, the engine has been capped, and automatics deliberately capped still further. Why is that?

Cheers,

Richard.

[tweek]

Richard,

I think the red line indicates where maximum power is achieved and is separate from the limiter, you have already demonstrated that the engine can rev upto the limiter and hence achieve max power, the real issue as I see it is the way the gearbox behaves. You maybe able to get the gearbox ECU reflashed with new software to change the way it behaves, try contacting Unit 20 (www.unit20.org). As to why Audi produced a vehicle with the anomolies you have found we'll never know, there could be a good technical reason for it or someone just got the software wrong and didn't fix it.

As for the test drives, why not? I would and have hit the rev limiter during test drives, they want my money I want to make sure I like what I'm getting

Pete

[HoppyUK]

Thanks for your comments Pete. Everyone I've spoken to, including Audi UK, admit that it doesn't seem right, but cannot explain why. Audi is refering it to Germany, I believe. I just want to gather as much information as possible to get them to sort my car as it should be.

I will be happy if Audi can simply re-programme the box so that it changes up at the red line. Or even better, leave the auto settings where they are, ie changing 2-300rpm short of the red line for safety, but when switched to manual mode, cut out the upwards automatic shifts completely and let it run to the limiter if I'm stupid enough to let it. This is what regular manual gearbox cars do and I feel I am sufficiently competant to be trusted to grab the lever before it gets into trouble. I know of a Supra automatic box that does exactly this.

As things stand, and if my understanding of the facts is correct, Audi is guilty of miss-selling the S4 Tiptronic.