[norhog]

One point I would like to bring in here is reliability and longevity of the engine.

Just by simply considering one fact that higher engine revs will cause higher turbocharger RPM and subsequently higher boost pressure in the intake manifold.

A higher boost pressure means the engine internals piston rings, piston pin, main bearing, cylinder head gasket will be experiencing higher forces and stresses.
A NA engine revving at say 7000 RPM will have lesser forces going on, on the engine internals than a similar sized turbocharged (TC) engine.

So if you make the turbocharged engine stronger, it becomes heavier and costlier, and you loose the advantage of having a small, light, cheap (relatively speaking) and powerful powerplant to power your car.

Turbocharging and supercharging was developed with the intension of forcing in maximum possible air in the intake stroke, inside the combustion chamber.
More air in the combustion chamber means more fuel can be burnt, thus more power. So if you get your 90 bhp of a turbocharged engine at say 5000 RPM, so be it. Why do you need to rev it more?
To get more power in a similar size TC engine, like I said before, you have to strengthen the engine, thus engine becomes more heavy OR exotic materials need to be used like titanium etc. Both the options are expensive. So I guess you get the drift where this is going.

For F1 and race car engines, they overhaul the engine after every race or two literally. We cannot do that in our road going regular cars now, can we?

[AMG Power]

Originally Posted by Kosfactor

Why do you feel they are in the stone age?

The current ball park of cubic capacity / bhp ratio is 100. A 1.5 turbo petrol gives out 150 bhp (Skoda), 1.4 gives out 140 (Kia), 1.0 gives out 100 (VW), 2.0 liter (Skoda) gives out 190 / 200 bhp. In this group Mahindra makes a 2.0 liter that gives out 150 bhp only?

To make matters worse the buffoons put the engine in a 2021 model 20 lakh dinosaur called Thar that cannot go over 100 kmph unless one is on a suicide mission.

Even a Hindustan Ambassador which was engineered 75 years ago in 1956 could go over 100 kmph without putting the driver at unease.

And after 3/4 th of a century these clowns can’t even do that ? They’re only good at copying the cosmetic bits - interior / exterior etc, when it comes to engineering, copying isn’t easy, so they’re caught out.

If that isn’t Stone Age, what is?

[dhanushs]

Originally Posted by v1p3r

...
Your post is almost entirely correct. However, turbos and AFR are not related. Maintaining the correct AFRs across the rev range is a function of injectors, ECU and a suite of sensors. Adding a turbo will not do much. Of course, a bad AFR will literally melt your engine.
...

You are mentioning aspects that control the fuel. What about air, that's the Turbo. Hence, Turbo and AFR are related?

The point here is why engines aren't revving high. I said, for a daily driver you need power early in the rpm and hence smaller turbo. Unless you have a turbo that can cater higher rpm's there is no point giving a higher revv limit

[fhdowntheline]

Originally Posted by AMG Power

The current ball park of cubic capacity / bhp ratio is 100. A 1.5 turbo petrol gives out 150 bhp (Skoda), 1.4 gives out 140 (Kia), 1.0 gives out 100 (VW), 2.0 liter (Skoda) gives out 190 / 200 bhp. In this group Mahindra makes a 2.0 liter that gives out 150 bhp only?

To make matters worse the buffoons put the engine in a 2021 model 20 lakh dinosaur called Thar that cannot go over 100 kmph unless one is on a suicide mission.

Even a Hindustan Ambassador which was engineered 75 years ago in 1956 could go over 100 kmph without putting the driver at unease.

And after 3/4 th of a century these clowns can’t even do that ? They’re only good at copying the cosmetic bits - interior / exterior etc, when it comes to engineering, copying isn’t easy, so they’re caught out.

If that isn’t Stone Age, what is?

1)The Thar is almost like a metal container weighing over 1700 kgs, whereas the Ambassador did have some sort of aerodynamic shape and weighed around 1200-1300 kg.

2) I am pretty sure the Ambassador driver would be completely uneasy if he had to brake at 100 kph plus with its weedy tyres and wooden drum brakes. I remember the drivers who drove Amby cars during my childhood and they hated the braking.

The 2020 Thar has ABS, EBD , ESP, dual Airbags, not to mention crash safety ratings of a high order.
I think specifically wrt the Thar, the manufacturer has come a long way from Stone Age.

[Kosfactor]

Originally Posted by AMG Power

The current ball park of cubic capacity / bhp ratio is 100. A 1.5 turbo petrol gives out 150 bhp (Skoda), 1.4 gives out 140 (Kia), 1.0 gives out 100 (VW), 2.0 liter (Skoda) gives out 190 / 200 bhp. In this group Mahindra makes a 2.0 liter that gives out 150 bhp only?

To make matters worse the buffoons put the engine in a 2021 model 20 lakh dinosaur called Thar that cannot go over 100 kmph unless one is on a suicide mission.

Even a Hindustan Ambassador which was engineered 75 years ago in 1956 could go over 100 kmph without putting the driver at unease.

And after 3/4 th of a century these clowns can’t even do that ? They’re only good at copying the cosmetic bits - interior / exterior etc, when it comes to engineering, copying isn’t easy, so they’re caught out.

If that isn’t Stone Age, what is?

No Sir, its called fit for purpose.

Most vehicles under ~50L will fail your ball park figure expectations even otherwise.

Lets look at this example -

The 2.7L Petrol engine in an Innova produces only 164BHP @5200 RPM, it produces only 245nm Torque @4000 RPM, in comparison a Skoda 1.5 TSi will produce 148 BHP & 250nm of Torque. Do you think this Skoda engine can replace that 2.7? You know the answer.

OT : 2020 Thar or the old CRDe has no problem with 100 kmph, not one bit. Ambassador is better than most people remember it and I have driven ambassadors quite a bit, they are nowhere close.

[AMG Power]

Originally Posted by Kosfactor

The 2.7L Petrol engine in an Innova produces only 164BHP @5200 RPM, it produces only 245nm Torque @4000 RPM,

That is not a turbo petrol engine. It is a NA engine and that is why the figures are lower. The ball park figure where Mahindra was very much lower was with reference to turbo petrols.

[v1p3r]

Originally Posted by dhanushs

You are mentioning aspects that control the fuel. What about air, that's the Turbo. Hence, Turbo and AFR are related?

In theory, AFR and turbos are related, albeit in a slightly different way than you have posited. In practice, the A in AFR is the boundary condition that the F must be tuned for, so that the R remains safe. An ICE will have a standard airflow profile, given various other conditions like valve timing and control, intake pressure, RPM, etc. So what you're really looking for is the ability to match the right fuel amounts to that specific airflow mass at that RPM. This is primarily a function of injector timing and pulsewidth, injection pressure, and your oxygen sensor. Secondary instruments would include a knock sensor. With diesels, the need is even less - diesels are basically big air pumps where a certain amount of knock is acceptable. So the airflow mass does not require control as such, as much as it is the determining factor for how much fuel needs to be injected.

Originally Posted by dhanushs

Unless you have a turbo that can cater higher rpm's there is no point giving a higher revv limit

This is correct.

Originally Posted by AMG Power

If that isn’t Stone Age, what is?

I can't comment as to which prehistoric age these guys are in, but I can tell you that TML has about 100 engineers in the powertrain division alone. I can only guess what they do there - eat donuts all day, tickle each others' bellies, play hide-and-seek with trim parts, start their own vada-pav stalls - because even with that many engineers, their engines have a higher IPTV and lower specific output than most others. Let's not forget that every time there is a halo tuning project, it goes to Jayem in Coimbatore because Pimpri's pride can't seem to figure out the basics of performance enhancement to a level that a college student in the west would.

M&M is actually behind TML in this regard.

[pavi]

I don't know the technical details to compare between a turbo and a NA petrol engine, so those who are interested in only the 'scientific details', please don't go further. I own a 4th gen Honda City ivtec MT and Skoda Rapid TSI MT. I love the Honda ivtec engine and love to rev it when ever possible, 2nd gear overtakes are my favorite. After driving the TSI for over 2000 kms, I am loving the TSI engine more. Why?? I can keep the speed much higher with very less work done. I found it easier to drive the Rapid when compared to City and it's engine is only a 1 liter turbo. So my question would be why would you need a higher rev limiter when you can extract more power at lower rpms when compared to a NA engine. The higher rpms were never missed in the last 2000+ kms in Rapid, for I have all the power needed (and some more) at mid rpms itself. If it's for the fun of revving high, yes I am with you, NA is still hell lot of fun at high rpms.

[venkyhere]

Originally Posted by v1p3r

A few reasons:

1. It's not needed: Very often, turbochargers are added to engines to make them more relevant. For example, the beloved 1.8T from VAG (which came in the old Octavia RS, Audi A4, Beetle, etc.) began life in the 80s as an NA Audi engine. To pass modern emissions and make the same engine architecture more driveable, a turbocharger was added. This lowers max torque points (way more important for driving than bhp) and makes the car more efficient. As a result, there is no need to have higher revs. The 1.8T's max torque rpm went from ~3500 to ~1750, lowering gear shift points and increasing efficiency.
2. Turbos choke: Point 1 also means that a turbocharger is optimised for a rev range. This is normally the mid range, where most people drive. Because of how air flows, a turbo that works well in the mid range will choke the engine at higher RPMs. This choking will also overcome the inherent ability of an ICE to produce more power with higher revs. So the engine will be quite useless past a certain rev limit.
3. Detonation: Higher revs increase the chance of detonation. Add to that the extra heat generated by compressing the charge, and the lack of absolute reliability on both fuel quality and driver skills, and a high rev limit is suddenly a bad idea.

I must admit that I never thought about 2 , whilst I was going to type a reply with 1 and 3 as the reasons, particularly 3, where the heat of the charge doesn't leave much room to have meaningful advanced enough timing to generate notable extra power as revvs climb, to justify higher revving.

Many of the replies in this thread tend to suggest that engine designers somehow have "free choice" while determining the redline - it's not the case, unfortunately. There are a terrible number of restrictions even in NA guise. When coming to turbocharging, these restrictions increase exponentially.

The most "executive summary" way to answer the title Q of the thread could be -
It's not a linear system, things don't just 'scale up' linearly - things like propagation time for combustion remain largely same & things like heat energy transfer and gas expansion etc vary exponentially, rather than linearly. That would mean somewhere nature will come and bite us, even if we try and fool it by making the intake charge mass artificially high, rather than letting the intake charge mass be determined by the suction rate of a reciprocating cylinder.

Even otherwise, I am curious to know (as I have observed elsewhere too, in forums and social media) - why is high-revving considered with such great reverence ? is it because of the high frequency sound ? Never been able to understand the correlation between driving pleasure and engine RPM. If it feels great to your bum and hands (chassis and steering) and it goes like the clappers, why care about the rotation rate of an entity that is producing the power to do so ?

[Pashin]

Maybe it has something to do with the way Turbos are designed in modern cars. To minimize turbo lag and achieve early boost the turbos may be getting smaller. These small turbos may not be useful in the high rev range. There were many high end cars with "Twin Turbos", not sure whether they still have that config even now.

[kutlee]

Originally Posted by dhanushs

You are mentioning aspects that control the fuel. What about air, that's the Turbo. Hence, Turbo and AFR are related?

I thought the air mass calculation is kindly sponsored by ideal gas law. Then you add fuel to the get the required AFR. So AFR is more of a target than a given. So if you have powerful enough ECU and sensors and triggers etc to get the required AFR, you can always run in closed loop and hit that AFR. Also higher gas volumes/weigh need better exhaust, high flow cat converter etc. Things get expensive.

[PrasannaDhana]

Originally Posted by Dr.Naren

Suzuki 1.5 DDIS was one of the best revving diesel engines I ever drove .

Even the 1.3 DDIS is pretty rev happy and revs till 5000 rpm.

Tatas have always been conservative and are not at all rev happy. My storme for instance, revs just upto 4000 rpm. And one wouldn't want to go anywhere over 3250 rpm.

I have driven the 1.0 tsi of the VAG, and that 6500 rpm wasn't that bad of bother. I floored it and it was very fun even within the 6000 rpm.

[Dr.Naren]

Originally Posted by PrasannaDhana

Even the 1.3 DDIS is pretty rev happy and revs till 5000 rpm. That's in the top gear, still revving till 4300 rpm Tatas have always been conservative and are not at all rev .

Yes I agree that 1.3 MJD also revvs good. 1.5 DDIS has better torque curve. That's the reason Ciaz 1.5 is significantly faster than 1.3, but the peak numbers on paper do not show a big difference. Another point is the smoothness while revving the 1.5 .

[Raghu M]

Originally Posted by Jeroen

What is with the fascination of high revving?

We have countless threads suggesting trost Indian drivers never ever exceeds 1500RPM?

We are concerned about lugging not revving I thought?

Jeroen

Exactly my thoughts. What's the point of revving an engine beyond 5K +? You can't even run a car beyond 120 kmph on 99% of Indian roads.

[sierrabravo98]

Originally Posted by AMG Power

The current ball park of cubic capacity / bhp ratio is 100. A 1.5 turbo petrol gives out 150 bhp (Skoda), 1.4 gives out 140 (Kia), 1.0 gives out 100 (VW), 2.0 liter (Skoda) gives out 190 / 200 bhp. In this group Mahindra makes a 2.0 liter that gives out 150 bhp only?

To make matters worse the buffoons put the engine in a 2021 model 20 lakh dinosaur called Thar that cannot go over 100 kmph unless one is on a suicide mission.

Even a Hindustan Ambassador which was engineered 75 years ago in 1956 could go over 100 kmph without putting the driver at unease.

And after 3/4 th of a century these clowns can’t even do that ? They’re only good at copying the cosmetic bits - interior / exterior etc, when it comes to engineering, copying isn’t easy, so they’re caught out.

If that isn’t Stone Age, what is?

Correct me if I am wrong but isn't the 2.0L GDI engine used in the Thar capable of churning out something like 190 horses? The upcoming XUV5OO is supposed to come in that tune.