[Rtech]

Yup, thats what a friends 1.5 OHC Type I revvs to now. And man, what a sound.

oh yea, it also puts out about 112hp.

Spent the entire day here as he is more set up for Vtecs rather than non-vtecs. He claims peak power is made at about 6800-7200.

Shan, most cars will produce their peak power before they revv out, not at the redline only. What the extra rpm's give you is the ability to hold a gear longer, which comes in use when cornering, overtaking or even for 0-100 times if it allows you to avoid a change.

No adverse affects aside from the usual wear n tear with high revving an engine. Afterall, it is a Honda! But still, not that you would want to do that in every gear and all the time!

[Shan2nu]

Shan, most cars will produce their peak power before they revv out, not at the redline only.

Thats why i said 8000rpm, 300rpm below the redline.

What the extra rpm's give you is the ability to hold a gear longer, which comes in use when cornering, overtaking or even for 0-100 times if it allows you to avoid a change.

Even for a 0-100, it doesn't need to revv to 8300 dude!!! A stock City 1.5 will reach 96kmph at 6800rpm (redline). So, at 7052rpm the car has already achieved 100kmph (which is below the claimed peak power rpm of 7200).

On a track, i think it would make more sense to shift up since you're gonna need a quick exit out of the corner. Will confirm this and let you know, though. If you have any articles on shifting at corner entry, let me know.

No adverse affects aside from the usual wear n tear with high revving an engine. Afterall, it is a Honda! But still, not that you would want to do that in every gear and all the time!

Do you think the engine is capable of such high rpms? Won't the engine rquire some mechanical changes to sustain higher rpms?

Shan2nu

[Rtech]

Thats why i said 8000rpm, 300rpm below the redline.

ok boss

Even for a 0-100, it doesn't need to revv to 8300 dude!!! A stock City 1.5 will reach 96kmph at 6800rpm (redline). So, at 7052rpm the car has already achieved 100kmph (which is below the claimed peak power rpm of 7200).

again, OK boss!! I was talking in general. I had no idea what gear/rpm the city reaches 100.

On a track, i think it would make more sense to shift up since you're gonna need a quick exit out of the corner. Will confirm this and let you know, though. If you have any articles on shifting at corner entry, let me know.

best never to change gears when in the middle of a corner. Just unsettles the car. if there is no ideal gear for a corner, take the best compromise. however, this is just a base point, an ideal situation if you like.

Each and every corner is different and has to be looked at differently. When I went through the racing school, they taught us the ideals. that has to be taught first. However, when we started practicing seriously, things changed. There was this one off-camber left-hander just before a steep climb that required a shift. Places like that throw the "ideal situation" out of the window.

And its exactly places like this on a track where the extra rev limit come into use as it allows you to hold that gear loger AND gain a bit of speed WITHOUT unsettling the car.

Do you think the engine is capable of such high rpms? Won't the engine rquire some mechanical changes to sustain higher rpms?

Its 1,200 rpm higher than the original redline. So no, I don't think it will pose a problem.

[Shan2nu]

best never to change gears when in the middle of a corner. Just unsettles the car. if there is no ideal gear for a corner, take the best compromise. however, this is just a base point, an ideal situation if you like.

Each and every corner is different and has to be looked at differently. When I went through the racing school, they taught us the ideals. that has to be taught first. However, when we started practicing seriously, things changed. There was this one off-camber left-hander just before a steep climb that required a shift. Places like that throw the "ideal situation" out of the window.

And its exactly places like this on a track where the extra rev limit come into use as it allows you to hold that gear loger AND gain a bit of speed WITHOUT unsettling the car.

I get your point. But still, if you're entering a corner at 7200rpm in 2nd, you might hold it there (even i would), maybe take it to 7500rpm. I can't see any reason why someone would want to take it all the way to 8300?

Sorry if i'm sounding like a geek but, i just can't live with the fact that a car producing peak power at 7200rpm (as claimed), needs to shift at 8300rpm, in any scenario.

I've got a City too and i'd love to see it revv to 8300rpm (provided it makes sense).

Shan2nu

[Rtech]

what rpm does the Vtec make its peak power at?

[Shan2nu]

what rpm does the Vtec make its peak power at?

Power peaks at 6800rpm, 7100rpm is the redline.

Shan2nu

[Rehaan]

Originally Posted by Shan2nu

I get your point. But still, if you're entering a corner at 7200rpm in 2nd, you might hold it there (even i would), maybe take it to 7500rpm. I can't see any reason why someone would want to take it all the way to 8300?

What if it was a fast sweeping (increasing radius if you must) corner, in which you want to gain speed (as opposed to holding a constant speed).
You enter the corner at 7,099RPM. What you gonna do? Upshift and unsettle your car, or wish your car revved till 8,300?

cya
R

[Shan2nu]

I would obviously upshift after 7500rpm or, if i wanna take it easier, enter the corner in the next gear at 4638rpm.

How do you expect the car to accelerate quick enuf to 8300 when the power peaks out at 7200? If that was the case then every cars shiftpoint would be fixed 1200rpm beyond peak power.

Shan2nu

[Rehaan]

Originally Posted by Shan2nu

I would obviously upshift after 7500rpm or, if i wanna take it easier, enter the corner in the next gear at 4638rpm.

Upshifting @7500 was not an option, we were talking about the stock redline vs the 8,300rpm redline.

So the choices would be
1. Hold the car at a constant speed at 7,100rpm (vtec redline)
[disadvantage = slower lap]

2. Upshift to next gear
[disadvantage = possibility of unsettling the car]

3. Have the ability to revv to 8,300
[disadvantage = more engine wear]

How do you expect the car to accelerate quick enuf to 8300 when the power peaks out at 7200?

The fact is that it will still be accelerating. It will not be accelerating as fast as it does from say 6800-7200, but it WILL be accelerating, which is an advantage over option 1 listed above, and possibly an advantage over option 2 as well, since its a question of whether more power is created at 7300rpm, 7400rpm etc than 4638rpm, 4738rpm etc, and that depends on the power curves (since you have already established a gear ratio).


I'm just trying to answer your original query >

Originally Posted by shan2nu

I can't see any reason why someone would want to take it all the way to 8300?

Sorry if i'm sounding like a geek but, i just can't live with the fact that a car producing peak power at 7200rpm (as claimed), needs to shift at 8300rpm, in any scenario.

Heres another scenario as well-
Theres a long straight, followed by a sharp 2nd gear left hander.
In your Vtec, you are 9/10ths of the way down the straight, but you hit 7100rpm in 3rd gear.
Option 1 - Upshift (but lose .3 of a second on the shift) , only to have to double-downshift again at the corner
Option 2 - Hold the gear, mantain speed, but no acceleration
[The choice between these options would largely depend on how long the remaining 1/10th of the straight was, and how much of it would be remaining after the .3secs for a shift]

Either way, in theory, neither of those options would beat being able to continue accelerating till 8,300rpm and then downshifting to 2nd for the turn.

Remember - Just because power is on a downward curve doesnt mean that its not making acceleration happen.
Plus, the higher redline is a larger advantage on cars with wider spaced ratios (or as you go higher up in the gearshifts. ie more advantageous between 3rd&4th than 1st&2nd)

Hope that illustrates things better,
cya
R

[Rtech]

How do you expect the car to accelerate quick enuf to 8300 when the power peaks out at 7200?

boss...the needle simply flies to 8000rpm!! you'd need a really light foot NOT to get there

[Shan2nu]

@Rehaan - Firstly, we don't know if 8300 is actually the redline of the engine. 2ndly, the peak torque at 7200 is a probability and not a certainty.

It's not that easy to say that revving to 8300 will assure you a better lap time. It may or maynot (Depends on the power/torque curve)

@Rtech - Maybe it flies but, unless we check it's acceleration from 0-150kmph (shifting at 8300) and 0-150kmph (shfting at 7500), we'l never know which is quicker.

My guess is that it's way too early to decide on anything. I don't deny that it revvs to 8300 but, i can't agree that it helps to revv to 8300 unless i see some figures.

Shan2nu

[Shan2nu]

Found something regarding redline.

Redline refers to the maximum speed at which an internal combustion engine and its components are designed to operate without causing damage to the components themselves or other parts of the engine. The redline of an engine depends on various factors such as stroke (the total up or down distance moved by any one piston during its cycle), displacement, composition of components, and balance of components. Redlines vary anywhere from a few hundred RPM (very large engines, i.e. trains, generators) to in the tens of thousands of RPM (smaller, usually high performance engines such as motorcycles and sports cars). Diesel engines normally have lower redlines than comparatively-sized gasoline engines.

Redline is usually determined by stress-testing the engine and its components. Changing the stroke of the engine (the lateral distance the pistons travel) can also change the redline. Engines with short strokes can handle higher RPM because there is less force in reciprocating motion (see reciprocating engine). Lighter components can increase the redline as well, since they have less inertia and decrease forces present in the engine.

The actual term redline comes from the red bars that are displayed on tachometers in cars starting at the RPM that denotes the redline for the specific engine. Operating an engine in this area is known as redlining. Straying into this area usually does not mean instant engine failure, but may increase the chances of damaging the engine. Most modern cars have computer systems that prevent the engine from straying too far into the redline by cutting fuel flow to the fuel injectors/carburetor or by disabling the ignition system until the engine drops to a safer operating speed. Electronic Control Units (ECUs) of automatic transmission cars will upshift before the engine hits the redline even with maximum acceleration (an automatic transmission sport car's ECU will allow the engine to go nearer the redline or hit the redline before upshifting). If manual override is used,the engine will go past redline for a brief amount of time before the ECU will auto-upshift. When the car is in top gear and the engine is in redline (due to fast speed), the ECU will cut fuel to the engine, forcing it to slow down until the car slows down and will then release fuel back to the engine, allowing it to speed up again.

Source

So what i want to know is : How can the redline be moved from 6800 (stock) to 8300, without making any changes to the engine?

Electronically shifting the redline is one thing but, doesn't the engine need to be mechanically capable of supporting that increase in redline?

Frankly, i don't think it's worth revving the engine to 8300. All you're gonna get is higher wear n tear.

PS : If the City was to have a 9000 rpm tacho.....i'm pretty sure it would have managed that too. So, would the redline be 9000 rpm in that case (even thought peak power is achieved at 7200)?

Shan2nu

[Rehaan]

Originally Posted by Shan2nu

@Rehaan - Firstly, we don't know if 8300 is actually the redline of the engine.

Shan2nu,

There is no actual redline of the engine!!
Its just a revvlimit that is reached by choosing optimum factors of enginewear, powertrain loads, powercurves etc, which differ from aplication to aplication.

As for everything else, i will follow Rtech's example and say "ok boss"..

cya
R