Why is the red line so low?
08-25-2013, 09:34 PM
#1
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Why is the red line so low?
I used to own a nissan an SR20DE engine in it. It was a square (86mm x 86mm) 2 litre engine with hydraulic lifters and in stock form it would rev to 7500 RPM. HOwever the valve train could safely handle 8250 RPM, which is where I set my redline after some ECU tweaks.
Since this motor is very similar in design, why is the redline set so low?
If the LNF is a square motor, (I remember reading somewhere that it is.) Then piston speed is definitely not the limiting factor.
Is it a fueling issue since the cam runs the high pressure pump?
This car with a slightly bigger turbo and an 8000 RPM redline would be a monster.
Since this motor is very similar in design, why is the redline set so low?
If the LNF is a square motor, (I remember reading somewhere that it is.) Then piston speed is definitely not the limiting factor.
Is it a fueling issue since the cam runs the high pressure pump?
This car with a slightly bigger turbo and an 8000 RPM redline would be a monster.
08-25-2013, 10:32 PM
#2
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Higher rpm's don't necessarily translate into more power.
Redline on a stock configuration is most often past the peak hp power range anyway. Going beyond a vehicles redline usually means you're outside of the peak power curve, and the result is it's slower.
To answer the question.The redline isn't low. It is set there based on that power curve.
Redline on a stock configuration is most often past the peak hp power range anyway. Going beyond a vehicles redline usually means you're outside of the peak power curve, and the result is it's slower.
To answer the question.The redline isn't low. It is set there based on that power curve.
08-25-2013, 10:43 PM
#3
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Honestly you'd need to address your question with an engineer at GM, but there are reasons as to why the redline is set where it is.
Some balance shafted engines(like the Ecotec's in all HHR's 2.0 -2.4)are limited in their ability to rev beyond a certain rpm because of the presence of the shafts in the first place.
The shafts are there to quell the inherent Second Order Vibrations that all inline 4's have.(the 4-banger shake)
Since the Second Order Vibrations are at a frequency that is double that of the crankshaft rpm, the balance shafts are designed to work at a set range of rpm's.
They are most effective between 4,000 to 5,000 rpm, but running the engines beyond the redline can induce Fourth Order Vibrations which will cause destructive resonances.
And as George pointed out, higher redline limits do not equal power, plus comparing a Nissan SR20DE to an Ecotec LNF is an apples to oranges deal.
Some balance shafted engines(like the Ecotec's in all HHR's 2.0 -2.4)are limited in their ability to rev beyond a certain rpm because of the presence of the shafts in the first place.
The shafts are there to quell the inherent Second Order Vibrations that all inline 4's have.(the 4-banger shake)
Since the Second Order Vibrations are at a frequency that is double that of the crankshaft rpm, the balance shafts are designed to work at a set range of rpm's.
They are most effective between 4,000 to 5,000 rpm, but running the engines beyond the redline can induce Fourth Order Vibrations which will cause destructive resonances.
And as George pointed out, higher redline limits do not equal power, plus comparing a Nissan SR20DE to an Ecotec LNF is an apples to oranges deal.
08-25-2013, 11:15 PM
#4
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Honestly you'd need to address your question with an engineer at GM, but there are reasons as to why the redline is set where it is.
Some balance shafted engines(like the Ecotec's in all HHR's 2.0 -2.4)are limited in their ability to rev beyond a certain rpm because of the presence of the shafts in the first place.
The shafts are there to quell the inherent Second Order Vibrations that all inline 4's have.(the 4-banger shake)
Since the Second Order Vibrations are at a frequency that is double that of the crankshaft rpm, the balance shafts are designed to work at a set range of rpm's.
They are most effective between 4,000 to 5,000 rpm, but running the engines beyond the redline can induce Fourth Order Vibrations which will cause destructive resonances.
And as George pointed out, higher redline limits do not equal power, plus comparing a Nissan SR20DE to an Ecotec LNF is an apples to oranges deal.
Some balance shafted engines(like the Ecotec's in all HHR's 2.0 -2.4)are limited in their ability to rev beyond a certain rpm because of the presence of the shafts in the first place.
The shafts are there to quell the inherent Second Order Vibrations that all inline 4's have.(the 4-banger shake)
Since the Second Order Vibrations are at a frequency that is double that of the crankshaft rpm, the balance shafts are designed to work at a set range of rpm's.
They are most effective between 4,000 to 5,000 rpm, but running the engines beyond the redline can induce Fourth Order Vibrations which will cause destructive resonances.
And as George pointed out, higher redline limits do not equal power, plus comparing a Nissan SR20DE to an Ecotec LNF is an apples to oranges deal.
"they dont make power up there" doesn't make any sense. A power curve can always be tweaked with breather mods, which includes a change in turbo.
SR20DE(T) and LNF have more in common than not. The major difference is the direct injection vs. port injection. I dont yet know how valve train speed affects fueling. I know ZZP have played around with it, their camshaft has a bigger lobe on it. I'll know more once I get my hands on an FSM.
08-25-2013, 11:35 PM
#5
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Let me quote GM....
"This 2.0-liter Turbo is the pinnacle of Ecotec performance to date, with additional growth planned," says Groff. The groundwork for its capabilities was laid on the drawing table at the beginning of the Ecotec's development. Prior work and a far-thinking engine design continue to help GM respond to market demands around the globe more quickly and with greater accuracy.
This new Ecotec family member also features:
Dual overhead camshafts (DOHC) and four valves per cylinder
**Twin counter-rotating balance shafts for operational smoothness**
"Drive by Wire" electronic throttle control
Low friction, roller-finger follower valvetrain with hydraulic lash adjusters
Low-maintenance chain-drive for the camshafts
58X camshaft positioning
Direct-mount accessories, which reduce or eliminate traditional sources of noise and vibration
Full-circle transmission to reduce noise and vibration
GM Oil Life System, which can reduce the frequency for oil changes
As with other engines in the Ecotec family, the 2.0-liter Turbo engine also has premium features designed to ensure smooth and quiet operation, including a polymer coating and skirt design for the pistons that reduce noise during cold starts. An automatic hydraulic tensioner also is used to maintain optimal tension on the timing chain, which reduces noise and vibration."
And this is what the folks at ZZP have to say....
"The installation of cams in an overhead cam motor requires a knowledgeable mechanic to do it properly. Failure to have the timing chain and gears setup correctly will result in poor performance or severe engine damage.
You will NEED to replace your valve springs and retainers. It is also recommended to remove or replace your balance shafts with the neutral balance shafts if spinning above 7k rpm."
Yes Ecotecs are internally balanced, balance shafts have nothing to do with balancing the crankshaft, they are there strictly to quell Second Order Vibrations inherit in the design of 4-cyl inline engine.
Remember, two pistons up, two pistons down every time the crank rotates. The crankshaft counterweights take care of balancing that out, but when the cylinders fire in their 1-3-4-2 order the engine shakes in a vertical plane.
That is the shake typically felt in non-shafted fours, it comes right up the steering column and also through the floorpan into your butt.
"This 2.0-liter Turbo is the pinnacle of Ecotec performance to date, with additional growth planned," says Groff. The groundwork for its capabilities was laid on the drawing table at the beginning of the Ecotec's development. Prior work and a far-thinking engine design continue to help GM respond to market demands around the globe more quickly and with greater accuracy.
This new Ecotec family member also features:
Dual overhead camshafts (DOHC) and four valves per cylinder
**Twin counter-rotating balance shafts for operational smoothness**
"Drive by Wire" electronic throttle control
Low friction, roller-finger follower valvetrain with hydraulic lash adjusters
Low-maintenance chain-drive for the camshafts
58X camshaft positioning
Direct-mount accessories, which reduce or eliminate traditional sources of noise and vibration
Full-circle transmission to reduce noise and vibration
GM Oil Life System, which can reduce the frequency for oil changes
As with other engines in the Ecotec family, the 2.0-liter Turbo engine also has premium features designed to ensure smooth and quiet operation, including a polymer coating and skirt design for the pistons that reduce noise during cold starts. An automatic hydraulic tensioner also is used to maintain optimal tension on the timing chain, which reduces noise and vibration."
And this is what the folks at ZZP have to say....
"The installation of cams in an overhead cam motor requires a knowledgeable mechanic to do it properly. Failure to have the timing chain and gears setup correctly will result in poor performance or severe engine damage.
You will NEED to replace your valve springs and retainers. It is also recommended to remove or replace your balance shafts with the neutral balance shafts if spinning above 7k rpm."
Yes Ecotecs are internally balanced, balance shafts have nothing to do with balancing the crankshaft, they are there strictly to quell Second Order Vibrations inherit in the design of 4-cyl inline engine.
Remember, two pistons up, two pistons down every time the crank rotates. The crankshaft counterweights take care of balancing that out, but when the cylinders fire in their 1-3-4-2 order the engine shakes in a vertical plane.
That is the shake typically felt in non-shafted fours, it comes right up the steering column and also through the floorpan into your butt.
Last edited by 843de; 08-26-2013 at 12:12 AM. Reason: Cut down the huge GM quote.....
08-26-2013, 11:24 AM
#6
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Location: Palm Bay, Florida
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The 2.4 has peak HP at 6250 rpm (I think) however at 70 mph the car runs at 2500 rpm. I don't hit 6200 rpms very often, unless you are racing the car I don't see why you have the concern over red line rpm.
08-26-2013, 12:38 PM
#7
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Join Date: 06-17-2013
Location: MD
Posts: 80
so balance shaft removal kit
stiffer springs and possibly a new cam?
why a new cam? is that for the fuelling issue?
edit: the plan is to race this car once I replace my wife's versa with something bigger.
stiffer springs and possibly a new cam?
why a new cam? is that for the fuelling issue?
edit: the plan is to race this car once I replace my wife's versa with something bigger.
08-26-2013, 06:10 PM
#9
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Valve train speed is only one part of the equation.
Intake flow, exhaust flow, combustion chamber design and flow characteristics, camshaft lift and duration, fuel delivery rates, and internal reciprocating masses all need figured in.
More agressive cam designs allow the engines to breathe better, but all the factors above need addressing. The blank balance shafts allow for a higher than normal redline by eliminating the destructive Fourth Order vibration modes that would cause a catastrophic engine failure.
At 6,000 rpm the balance shafts are spinning at 12,000 rpm, so you have some significant internal masses screaming along already.
Here's a good article on the balancing of internal combustion engines....
http://www.autozine.org/technical_sc...ne/smooth2.htm
Intake flow, exhaust flow, combustion chamber design and flow characteristics, camshaft lift and duration, fuel delivery rates, and internal reciprocating masses all need figured in.
More agressive cam designs allow the engines to breathe better, but all the factors above need addressing. The blank balance shafts allow for a higher than normal redline by eliminating the destructive Fourth Order vibration modes that would cause a catastrophic engine failure.
At 6,000 rpm the balance shafts are spinning at 12,000 rpm, so you have some significant internal masses screaming along already.
Here's a good article on the balancing of internal combustion engines....
http://www.autozine.org/technical_sc...ne/smooth2.htm
08-26-2013, 10:07 PM
#10
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Location: Washington State, where it rains
Posts: 4,708
One can design the motor to spin at higher rpms...at the sacrifice of power in the lower rpm ranges where 99% of normal driving occurs...race engines run high for the momentum factor..and gearing..like e an electric motor, gearing allows for faster speed build up..but costs more energy to be used. Not practicle for a normal car.