[Guna]

Originally Posted by Jeroen

Correct, weight of these component has a big impact on the engine performance. In particular, in context of this thread, how fast an engine could rev. Think moment of inertia and centripetal forces.

For similar reasons stroke has a big impact as it determines the maximum speed of a piston and thus impacts the same.


Jeroen

You are right (and I was wrong) , I did some reading as well. Since the piston is a reciprocating mass which has to change it's direction multiple times within second, every ounce seem to matter. Plus, the increase in piston, connecting rod, crankshaft results in the increase of weight of the counter balance as well.

[antz.bin]

Could this be the scientific reason?

https://www.ninjah2.org/threads/urba...r-chirp.23761/

As the revs climb in the turbocharger, the some parts of the turbo blades will be traveling at a really high speed.

The metallurgy required for making sure the blades don't give up at near-sound-barrier-speeds will make it prohibitively expensive to produce. The simpler option will be to not even go close to these speeds.

Cars can obviously come with larger turbochargers than the supercharger seen on the Ninja / Z H2s, (simple reason, there is much more space under the hood of a car) they will reach the sound barrier at much lower revs since the speed at which the tips are traveling is also directly proportional to the diameter as well as the revs (circumference of a circle = 2πr).

When they can already overcome the power outputs of the next higher engine size with low revs and preserve efficiency, emissions and performance, there is no need to make everything more expensive.

[Jeroen]

I see a lot of comments on how the max RPM of the turbo might be the limiting factor. I don’t think that is a reason at all. Engine and turbo are designed in conjunction. So they are matched and optimised for whatever you want the design criteria to be.

Besides as I mentioned before we have waste gates to keep turbo rpm (and back pressure) in place.


The approach into this high revving discussion is not the correct one I believe; If you start thinking from an existing engine and simply (mentally) rev it up. When you do that you will run into all sort of problems. Including turbo’s running too fast, bearing wearing out etc.

Engine design is always a compromise of many different factors. If there is a need for a high revving engine, it is simply designed that way. Can and is being done, and it tends to be more expensive than most engine that don’t rev so high.

Other than the glorious sound, today’s engine tend to get optimised for delivering power (torque) at as low RPMs as possible. When all is said and done, this will allow for cleaner combustion (less emissions) and better fuel economy. It also improves driveability tremendously as these days most cars will have plenty of torque in every gear across a wide RPM band.

At high RPMs the power delivery becomes very inefficient. Or at least very complex and costly to do it properly; All sorts of internal losses in the engine, notably friction losses increase exponentially with RPMs.

Engines that can run at these high RPMs tend to have a much narrower power band, which means you need to keep the RPMs up at all time, so you need a very different way of shifting too. You shift at high RPMs (which means some extra attention is needed for how you design the power train, clutch and gear box)

So these days it is cheaper and easier to produce an engine with a nice flat torque curve from pretty low RPM up to a decent number of RPMs. There is simply nothing to be gained to produce high revving monster.

With the exception of a few cars/engines out there. Somehow there is this almost mythical auro around high revving engine. Again, I love them for their sound, but give me a regular engine for all my day to day driving. Much more convenient, more comfortable, cleaner and less thirsty.

[Alka panwar]

It is simply much more expensive to make high reving Turbo petrols. Need much better balanced rotating components, lighter & stronger internals.
NA engines may rev to much higher rpms but they aren't making much torque at those RPMs, high horsepower is simply coming from more revs( hence more bangs per minute).
Most manufacturers are simply offering Turbo petrols with previous gen engineering ( crank/ con rods/ pistons/head design), largely trying to cash in on coolness factor of owning a Turbo petrol, plus Turbo in lean burn config helps achieve pollution norms.
They are not dishing out Turbos to provide rush, they are just saving money by not replacing already established Forge shops, machining facilities and engine assembly lines.

[SgtRepeat]

Originally Posted by sierrabravo98

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.

The Thar has a 2.0L I4 mStallion 150 TGDi engine that produces 150 bhp.

It will be mated to the upcoming XUV5OO in a higher state of tune to produce 190 bhp.

[Sankar]

Originally Posted by Alka panwar

It is simply much more expensive to make high reving Turbo petrols.

Yes sir, the right answer! It is expensive to produce reliable high revving motors that a manufacturer can warranty and more so $$ for a high revving turbo engines. High revving engines needs better everything inside the engine and outside. All drills down to $$ and where or how it is going to be used.

Apart from that the golden age of ICE is over; now its about economy, CAFE ratings, and stifling emissions equipment. High performance high revving petrol engines in daily drivers are a thing of the past, born when the manufacturers were trying to outdo each other in the performance and durability! Now the priorities are different; they are putting most of their money $$ into electric propulsion or hybrids because that is the future.

[Kosfactor]

So in conclusion, they CAN produce a high revving petrol turbo - but it isn't worth it. I`m happy that the direction they took to counter the diesel hate is petrol turbo and not add an electric motor to the existing petrol engine which is very expensive and complex in comparison.