high reving engines

[rice]

whats the difference in performance wise between high revving engines and low revving engines?? and whats the use for a high revving engine? wouldn't it be better if you made like 500 hp at 5,600 rpms than at 7,800 rpms??

[emiliorescigno]

wouldn't it be better if you made like 500 hp at 5,600 rpms than at 7,800 rpms??

Yes, that's why you don't buy a Honda

[sonyminidiscman]

well, all depends on how wide the powerband is.

[toyotaspeed90]

i'm going to give you a quick rundown in physics of engines..... hold your comments, this is a general statement and doesn't take into account differing metals for different components.

Lets take a chevy 350cid for example. A 350 is not just a 350. There are at least 3 different major production era's of the 350, not even including different bore and stroke combinations.

So, why can some 350's rev to only 5,000 while others can rev to 8,000? It's for the most part an equation based off of either bore or stroke. 350 just refers to the amount of volume displaced by the piston. Now you can have different variations of bore vs. stroke to achieve that displacement.

Think of it this way in a very simple way to grasp this. Imagine you're finding the area of a shape. It's width could be the bore and it's length cold be it's stroke. If you need to find a shape with 4 sides that has an area of 100 units, it could be achieved by 10x10, 5x20, 2.5x40, or vise versa: 20x5, 2.5x40 etc.....

So, now that you understand that an engine size of 1.6L could be a variation of bores and strokes i can get a little into rpm and hp/torque. As a general rule of thumb, an engine that has a shorter stroke (the length that the piston travels across the engine wall, ie from TDC to BDC) and a larger bore will have the ability to rev higher. However, this engine setup will not be able to create as much torque (can't remember the equation, but it has to do with the the work created by the length of the stroke) down low, but the faster it runs the more power it can make (ie, more HP in higher rpms). Inversely, an engine with a longer stroke and smaller bore will make more lowerend power. It will be limited to the rpm's to the forces that are put upon the longer connecting rod and can't rev as high. Also, they tend to make less power in the higher rpm's anyways.

Now that's just talking about the bottom end. Similar things can be applied to the head as well. Like, differing cam lobes & heights will produce different results, as will larger valves or stiffer valve springs.

flame on, pick at what i said, i don't really care. it's just a generality of motors.

[silver04rollas]

Owning a 8400 rpm high revving engine car myself, I will summarize the key features for you:

- Modelled exactly after how sports motorcycles work. Extract a lot of power from small engines. That is why it sounds like sports motorcycles at high revs i.e. Toyota's 2ZZ GE was designed and built by Yamaha (yes the entire engine and not only the header).

- you have with a high revving car is that during city driving while on the smaller cam below 6000 rpm, it drives like a normal car and gives great gas mileage. Almost as good as normal compact car.


- As soon as you need the power and performance, you punch the car above 6000 rpm and it switches to the high speed cam where the exhaust and intake cam lift is increased allowing cylinders to compress a lot more air and fuel mixture into the cylinders. Hence, called 'hitting lift' and the engines are called 'high compression ratio' engines for the same reason. There is a sudden surge in torque and horsepower and it keeps building power till it hits the redline (8400 rpm or so).

- Car's close and short gear ratios allow the car to rev up to redline very quickly in first gear and then close ratios allow it to keep the engine in high revs during shifts thus continuously delivering the power through rest of the gears. High revving cars are in particular excellent around racing tracks.

- At the top rpms high revving cars put out 100 horsepower per liter of displacement.

- Having power from a small engine allows the cars to have excellent power to weight ratio since the curb weight of the car is kept low i.e.


- The downside is that during city driving at low rpms, the car has just decent torque to scoot around. That is the thing about high revving engines since low end torque comes from displacement, but since high revving engines have small engines, but high horsepower at high revs does not change the fact that they make just decent torque down at low rpm and they are not quick when you are zinging around at low rpm.

Originally Posted by rice

wouldn't it be better if you made like 500 hp at 5,600 rpms than at 7,800 rpms??

It is dependent on a lot of variables i.e. how the power curve looks like on the graph, how the gear ratios complement the powerband of the car, how is the power to weight ratio etc.

[94_Rolla_Guy]

just to fill in the blank. the reason a long stroke makes more torque than a short stroke isn't related to the stroke in its self it is related to the crankshaft, in a longer stroke engine the rod journals are further out from the main journals making a more effective lever for the piston and rod to push ,but at the same time makes the reciprocating assembly, (rods pistons) move faster which puts higher forces on them thus taking away from the red-line. this same process works in vice-versa to create a high reving low torque engine

in short when comparing engines of the same displacement this is usually the case.

high revving = high HP / low torque = short stroke / large bore

low revving = Low HP / high torque = long stroke / small bore



also take into consideration that hp is proportional to torque

HP = Torque X RPM / 5252

It doesn't end here there is soo much theory behind this stuff

[Flashmn]

That is why it sounds like sports motorcycles at high revs i.e. Toyota's 2ZZ GE was designed and built by Yamaha (yes the entire engine and not only the header).

As are all toyota performance engines, 4A-GE / 3S-GE etc.

Few general points, engines revving faster will wear out faster, why do you think race engines have to be overhauled after each race and on the other end of the scale, cargoship engines last forever. Engines with a powerband at high rpm will feel like crap driving in town. I'd personally rather have a car that has a wide torque curve at low rpm. Nothing like beating that civic sounding like a lawnmower with a V8 reving to 5k max.

[silver04rollas]

Those other engines you mentioned do not have a seperate high performance camshaft that kicks at high rpms. 2.0 Liter 3S GE found in Altezza is the only other true high revving engine Toyota built (also collaborated with Yamaha for this one), but it does not have 'high lift camshaft', but relies on dual vvt-i and direct injection for high compression in cylinders and make 100 hp per liter.

As for high revving engines wearing faster, just for your information Toyota's performance 2ZZ GE engine (now 6 years in production) overall is rated atleast as reliable as the 1ZZ FE engine. That is exactly the official reason why Lotus picked the 2ZZ engine for the Elise (and the other reason was the very light weight of the engine).

Originally Posted by Flashmn

As are all toyota performance engines, 4A-GE / 3S-GE etc.

Few general points, engines revving faster will wear out faster, why do you think race engines have to be overhauled after each race and on the other end of the scale, cargoship engines last forever. Engines with a powerband at high rpm will feel like crap driving in town. I'd personally rather have a car that has a wide torque curve at low rpm. Nothing like beating that civic sounding like a lawnmower with a V8 reving to 5k max.

[357wheelgunner]

Originally Posted by silver04rollas

- you have with a high revving car is that during city driving while on the smaller cam below 6000 rpm, it drives like a normal car and gives great gas mileage. Almost as good as normal compact car.


- As soon as you need the power and performance, you punch the car above 6000 rpm and it switches to the high speed cam where the exhaust and intake cam lift is increased allowing cylinders to compress a lot more air and fuel mixture into the cylinders. Hence, called 'hitting lift' and the engines are called 'high compression ratio' engines for the same reason. There is a sudden surge in torque and horsepower and it keeps building power till it hits the redline (8400 rpm or so).

- Car's close and short gear ratios allow the car to rev up to redline very quickly in first gear and then close ratios allow it to keep the engine in high revs during shifts thus continuously delivering the power through rest of the gears. High revving cars are in particular excellent around racing tracks.

- At the top rpms high revving cars put out 100 horsepower per liter of displacement.

I like to get 38 mpg on the free way and still be able to punch it and beat most 4 cylinder cars, including turbo'd civics, s/c'd corolla Ss, and so on.

[357wheelgunner]

Originally Posted by 94_Rolla_Guy

just to fill in the blank. the reason a long stroke makes more torque than a short stroke isn't related to the stroke in its self it is related to the crankshaft, in a longer stroke engine the rod journals are further out from the main journals making a more effective lever for the piston and rod to push ,but at the same time makes the reciprocating assembly, (rods pistons) move faster which puts higher forces on them thus taking away from the red-line. this same process works in vice-versa to create a high reving low torque engine

in short when comparing engines of the same displacement this is usually the case.

high revving = high HP / low torque = short stroke / large bore

low revving = Low HP / high torque = long stroke / small bore



also take into consideration that hp is proportional to torque

HP = Torque X RPM / 5252

It doesn't end here there is soo much theory behind this stuff

I disagree, my XRS has amazing torque now (since CAI+flowmaster can) at low rpms, and amazing HP once my cam switches over.

[toyotaspeed90]

Originally Posted by 357wheelgunner

I like to get 38 mpg on the free way and still be able to punch it and beat most 4 cylinder cars, including turbo'd civics, s/c'd corolla Ss, and so on.

actually by opening up the airflow you generally allow the air to move through the engine easier, and you will lose lowend torque. I'm sure it's more of the 'it feels faster' than actually has more power dillema.


talking about getting good gas mileage and having good torque - one good thing about going with a standalone ecu on a 4agze (like my mr2) is that the supercharger has an electromagnetic clutch (for those that don't know, it's like the a/c compressor wheel).... so, when i want power i drive with the s/c on and catch mk2 turbo mr2's..... when i want good gas mileage, i drive with the s/c off and get over 30mpg with an untuned ecu

for some reason i doubt your xrs would beat an s/c rolla or a turbo civic (if either owner had any knowledge on their car and how to drive it).

[Flashmn]

Too bad theres no XRS's here, theres the T-sport corolla tho, I guess tahts about the same.
I'd like to hand one its ass with my corolla

[silver04rollas]

Yeah and then you will wake up...lol.

Originally Posted by Flashmn

I'd like to hand one its ass with my corolla

[micro214_kp61]

you guys are prolly smoking some good shit...