how much power is too much power?

[A_Harman]

Originally Posted By: ls1mike
Originally Posted By: DBMaster
Intake and exhaust modifications don't help much, unless the increased noise makes you THINK the car is more powerful. To use the "increased" airflow coming in and the increased exhaust flow your engine would also need to increase its flow of gases. So, without cam, valve timing, and fuel injection modifications there's not going to be much benefit.

I am not saying you get nothing. You just don't get much more than placebo effect.


Might want to caveat that it depends on the platform. An LS motor like my WS6 has does respond to those things well. Exhaust and SLP netted 26 RWHP on the Dyno without a tune 36 with a tune. It is not the same for all engines.


I agree. My LS1 picked up a noticeable amount of power above 5000 rpm when I did the cat-back exhaust and the SLP airbox and big MAF on the intake.

 

[A_Harman]

Originally Posted By: TFB1
No engine makes anywhere near it's max power at any given RPM unless it's at WOT...

Idling at closed throttle, the average passenger car engine is making maybe 15-25Hp...


By definition, an engine at idle is making 0 HP. Accessory loads driving the alternator and A/C compressor may get up to 3-5 HP.

 

[Hokiefyd]

Originally Posted By: A_Harman
By definition, an engine at idle is making 0 HP.


This is not true. Horsepower is a function of torque:

HP = (torque in lb*ft) x (RPM) / 5,252

Torque is being produced at idle (though it is low) and work is being done at idle. The crankshaft is spinning.

An electric motor typically produces max torque at 0 RPM (torque is a measure of force), but it produces zero horsepower at 0 RPM (because the shaft is not spinning).

Originally Posted By: A_Harman
Accessory loads driving the alternator and A/C compressor may get up to 3-5 HP.


Correct -- and proof that the engine generates horsepower even at idle.

 

[A_Harman]

Originally Posted By: Hokiefyd
Originally Posted By: A_Harman
By definition, an engine at idle is making 0 HP.


This is not true. Horsepower is a function of torque:

HP = (torque in lb*ft) x (RPM) / 5,252

Torque is being produced at idle (though it is low) and work is being done at idle. The crankshaft is spinning.

An electric motor typically produces max torque at 0 RPM (torque is a measure of force), but it produces zero horsepower at 0 RPM (because the shaft is not spinning).

Originally Posted By: A_Harman
Accessory loads driving the alternator and A/C compressor may get up to 3-5 HP.


Correct -- and proof that the engine generates horsepower even at idle.


That gets into a sematics area more than pure engineering. If the engine is not propelling the car, it is not doing any useful work, and therefore not making any power. If somebody defines playing the radio and running the air conditioner as useful work, then there is a reason to be absorbing power via the alternator and A/C compressor.

 

[MCompact]

Originally Posted By: A_Harman
Originally Posted By: ls1mike
Originally Posted By: DBMaster
Intake and exhaust modifications don't help much, unless the increased noise makes you THINK the car is more powerful. To use the "increased" airflow coming in and the increased exhaust flow your engine would also need to increase its flow of gases. So, without cam, valve timing, and fuel injection modifications there's not going to be much benefit.

I am not saying you get nothing. You just don't get much more than placebo effect.


Might want to caveat that it depends on the platform. An LS motor like my WS6 has does respond to those things well. Exhaust and SLP netted 26 RWHP on the Dyno without a tune 36 with a tune. It is not the same for all engines.


I agree. My LS1 picked up a noticeable amount of power above 5000 rpm when I did the cat-back exhaust and the SLP airbox and big MAF on the intake.


Ditto; I picked up @24 hp on my MS3 when I installed a Mazdaspeed(AEM) Cold Air Intake; it chopped 0.60 seconds off the 30-70 mph third gear acceleration times. The Hypertech tune added another 22 whp.

 

[Hokiefyd]

Originally Posted By: A_Harman
That gets into a sematics area more than pure engineering. If the engine is not propelling the car, it is not doing any useful work, and therefore not making any power.


It may not be doing useful work to you or to me, but it's still doing work. The crankshaft is spinning. We may not choose to harness it, but it's still performing work.

Think of it this way: does a lawn mower engine make power as it runs if you're parked over concrete and not cutting any grass? Nothing's attached to the PTO -- no transmission to move the mower, no alternator or accessory shaft. It's simply spinning its crankshaft.

(Yes, it is making power, whether you are using that power for cutting the grass or not, just as an engine is still making power, even if you're sitting still in neutral.)

 

[d00df00d]

Looks like you proved the first half of his point by missing the second half.

My engine makes 230 hp. If I'm in a situation where I can only deploy 100 hp, then I will reduce my throttle input so that my engine will only make 100 hp. Swapping my 230hp engine for an 800 hp engine would not make me go faster in that case; it'd just mean I'd have to be even more careful with the throttle.

Similar scenario if I had an 800 hp engine but could never get enough traction to put down more than 600. I'd always be managing my throttle input to keep the tires hooked up, and the engine would always be producing 600 out of its potential 800 hp. Upgrading to 1000 hp would just mean I'd be leaving 400 on the table instead of 200.

That's the point.

 

[Hokiefyd]

I understand the point. It's factually false that an engine makes 0 horsepower at idle. The statement was that an idling engine is making 0 hp, and it appeared to be correcting a claim that is likely true or at least close -- that an engine makes 15-25 hp at idle.

 

[A_Harman]

Originally Posted By: Hokiefyd
I understand the point. It's factually false that an engine makes 0 horsepower at idle. The statement was that an idling engine is making 0 hp, and it appeared to be correcting a claim that is likely true or at least close -- that an engine makes 15-25 hp at idle.


We can go into the fundamental IC engine discussion about Indicated, Friction, and Brake Horsepower, but the subject of the discussion we are having is Brake Horsepower. And that is where the term "useful power" becomes so important.

 

[Hokiefyd]

Let's instead just agree to disagree -- I really didn't intent to derail this thread as much as I did.

 

[d00df00d]

Originally Posted By: Hokiefyd
I understand the point. It's factually false that an engine makes 0 horsepower at idle. The statement was that an idling engine is making 0 hp, and it appeared to be correcting a claim that is likely true or at least close -- that an engine makes 15-25 hp at idle.

You know what? You're right. Looks like I was the one doing the misreading and point-missing. Sorry!

 

[d00df00d]

Originally Posted By: MCompact
Originally Posted By: d00df00d

Count me in with the "don't buy a car to impress people" bunch. The vast majority of people I talk to feel that switching from a '96 M3 to an '11 RX-8 was a downgrade. Does that sting sometimes? Sure. But it'll be a cold day in [censored] when I pay a dime or sacrifice on what I want in a car just to satisfy someone else's opinion.


There is a classic BMW "wearer" who posts in the car forums at Edmunds.com. He has an F10 535i xDrive with the sport package and believes that boring sled is the greatest thing since sliced bread. The fool can't comprehend that I would rather drive my MS3 or a Charger R/T Scat Pack over his wallowing marshmallow of a snooze-mobile. His head almost exploded when another participant sold his F10 5er and replaced it with a new Mazda3 GT. I informed the idiot F10 fan that I drive what makes me smile and that I don't select cars on the basis of how often it attracts envious glances or how well it telegraphs my disposable income to other motorists.
Moron.

Wanted to pick up on this comment, having driven an F10 535i X-Drive recently.

Not gonna say I endorse the name-calling, but... holy [censored] did I NOT enjoy driving the F10. The utter lack of steering feel -- by which I don't mean minimal steering feel, but effectively ZERO -- was bad enough to ruin the experience on its own. It was extra bad because the steering ratio is very quick for a car this size, and the steering response is nice -- those would be great things, but in combination with the utterly numb steering, they just made the car feel disturbingly unpredictable. That's unforgivable in a car like this, IMO.

And yet, F10s sell like hotcakes...

 

[DoubleWasp]

Originally Posted By: d00df00d
Originally Posted By: dailydriver
Originally Posted By: 02SE
I don't ride or drive anything, to impress others.



That's very admirable of you, but, around here at least, EVERY one of those cars (as well as all Priuses, new bugs, most Miatas and Minis, and some other marques) have equal signs, and rainbow stickers on them.

So, if one does not want to worry about their orientation being mistaken in these parts, it is 'safer' to not be in one of those marques.

I'd rock an equality sticker if I didn't dislike the idea of stickers on my car. I also might have bought an MX-5 if I didn't need back seats (though more likely an S2000).

My orientation is my business and my wife's. Anyone else can pound sand. Likewise, the orientation of a Prius or Mini driver is none of my business, stickers or no. I do dislike Minis and Priuses, though. But only because I think they're terrible cars.

Count me in with the "don't buy a car to impress people" bunch. The vast majority of people I talk to feel that switching from a '96 M3 to an '11 RX-8 was a downgrade. Does that sting sometimes? Sure. But it'll be a cold day in [censored] when I pay a dime or sacrifice on what I want in a car just to satisfy someone else's opinion.


Agreed. Even having my Porsche, I still love to drive my 92 Caprice. People can't make heads or tails of that.