How Much HP Do You Really Need???
 

I am as guilty of this as anyone, but how much HP do you really need in the real world??? We get consumed by 0-60 times, etc. But what makes for a really fun car in the real world??? I know I don't drag race between lights.

My answer would be a light car with decent hp. If I were to pick a car I wanted more than the RX-8, it would have to be the Elise, in regular or SC form. That car weights around 2000 lbs. The problem with the Elise is that it is a total toy and totally impractical. The RX-8 can perform everyday duties while being fun. The Elise would stay in the garage until a sunny warm day.

Aside from toys like the Elise, the RX-8 is already one of the lighter cars on the market, particularly if you talk about a car with any real practicality. I know the current RX-8 is dead in the marketplace for all practical purposes. But, in the real world in real world driving conditions, is a RX that is much more powerful or much lighter going to be THAT much more fun to drive day to day???

10 to 1.

So an RX8 with 300 crank HP would be perfect for a DD, anything more is wasted unless you get it on a track. Not wasted 100% of the time... but 99.9999% of the daily driving I do I never go WOT.

All depends on where you drive and what traffic is like. For me, no it won't make a difference because it's an overpopulated rich upper class yuppie neighborhood I live in. We get traffic being near the neighboring state all the time and it's freaking ridiculous. Takes me 30 minutes to go 10 miles to get to work.

Only on the highway or trips is it worth it but I'm content with what I got..................













Until I move back to the boonies.

Define much more. Kane's answer of 300rwhp is very good. There are tons of rave reviews from turbo owners at ~300rwhp that say the car is exponentially better than stock.

Personally, I agree with the sentiment wholeheartedly. The car is already great around corners; giving it a bit more straight-line speed would be the tits. Especially if I don't have to shift down to 4th just to pass people and climb uphill.

We always want more than we have. When I first drove the '8 I was impressed with its "pick up.' But of course later in my life with the vehicle I find myself wanting more, even tho' I know I have enough for my typical street-spirited driving. I've NA modded my '8 about as much as I'm willing to do short of an engine rebuild/porting (better intake and exhaust flow, Cobb AP tuned by MM, BHR iginition). I endlessly evaluate FI and Nitrous, but just as endlessly overide my impulse with the practicality of overall reliability and frugal consideration of ease of resale (or ease of potential engine replacement should the need arise). I still may go Nitrous this season tho'..... ;)

Personally, 1:9 is the ratio I use for a street car.
You really can't find a situation on the road where you will, shall we say, "be sad" with a 1:9 power to weight ratio.
On the RX-8 that is about 350 HP.

I dont go WOT all of the time and I live in an area without that much traffic. So honestly if the rx8 would have just a little bit more hp, like the greddy or pettit to put it close to 300 that would be great in my opinion.

Kanes got it right when he says much past that you really just wasted money unless your going to track it

In my flying days I was satisfied with a greater than 1:1 thrust to weight ratio. That's all you need to accelerate ballistically. ;)

300 rwhp is pretty amazing in the rx8. Like heaven on earth.

What I think is actually more relevant for a daily driver is ; how much torque do you really need ? Somewhere around 200+ ft/lbs in the 3-5500 range seems like plenty to me . Most of your daily driving is in that range .

300whp at 7500rpm is something you utilise infrequently (unless you are a nutter) although that does seem to be a good benchmark.

^ true that Brettus. In traffic our superb maneuverability is a plus, but really needs to be further augmented by a bit more torque. I've always considered myself an offensive driver in that I try to preemptively avoid potential hazards (e.g. poorly skilled drivers as well as road). I rarely need off the line or top end speed, but often need more rapid at-speed acceleration.

I am going to kill myself....

:confused:

A) Torque does no work

B) Torque times rpm ======== horsepower!

Why bring up irrelevant information?

Since I am too lazy to type.

http://www.carcraft.com/techarticles...que/index.html

Torque is overrated. :D:

If you were going to look at it that way what number would you say is good in the 3-5500rpm range ?
You can't give me a single number , which is why torque is relevant when talking mid range .

Really.

I don't understand the last two points.

Torque is the primary engine characteristic from which the more talked-about horsepower value is derived, as Kane points out.


As far as torque being "overrated", the area under the torque curve, as well as its distribution is an indicator of an engine's performance; just compare two strokes and four strokes of similar tune and see where the power lies.

Gains in high end rpm typically come at the cost of low end torque without some type of manifold pressure boosting system or variability in combustion timing. High torque motors generally achieve maximum hp before maximum rpm, but can drive a higher gearset.

The way I see it, what matters is not horsepower, but how it's made and how well it suits your needs, and that all is based on... torque.

Yeah I can...

On a street driven car, I would want to make 175HP by 3500 RPMS and make 300HP by 7000 RPMS.

Guess what the torque curve for that would look like?

What car is faster? 100 HP with 9000lb/ft of Torque or a 9000HP with 100lb/ft of Torque? Same gearing.

These motor-head heuristics are annoying.

"Torque does the work, but horsepower gets the credit."

"Horsepower sells cars, but torque wins races." - Carroll Shelby

:)

Well he is wrong...physics is on my side.

torque vs. horsepower = turbo vs. supercharger ;)

torque vs horsepower = boost vs flow


:lol:

http://static.howstuffworks.com/flash/fpte-curve2.swf

This is cool illustration of what I am trying to say.

I actually drove down (and up) the street yesterday in 2nd gear, just shy of the rev limiter, for about 2 minutes.
Does that make me a nutter?

Oh no. Here we go again.

Torque does ALL the work. Horsepower IS work, it doesn't "do" it.
Time is what makes force INTO work.
Torque, utilizing the TOOL that is TIME creates work.
Horsepower is a measurement of the work that torque does.

That is what mucks up your assertion.

If you geared each of those motors appropriately, they would be completely equal.

yes - certified

Torque is referenced in this case to acceleration - which is wrong.

HP difference determines acceleration rates, not torque.

Much like the whole boost vs flow thing - torque is a static measurement of force while HP tells you what the engine is doing.

I think this is what trips most people up.

Because an engine putting out only 1ft lb of torque but can spin fast enough to generate 1,000HP will simply not have a very good acceleration rate. Stick it on a 3,000lb vehicle, and I would struggle to believe it would move the car at all (without gear reduction for a torque multiplier). Not enough torque? or Not enough HP difference?

That is what gearing is for - to transform torque over time.

Torque is a vector, Work is a number. The confusion is both are newton meters.

When we tune on the dyno, we tune for torque.
The dyno computes horsepower for us and we go to great lengths to calculate out the effect of gearing.
The instantaneous torque at any RPM is like an integral in calculus - its an infinitely small slice of the overall curve of the motor. An instantaneous snapshot of the action of combustion at that moment.
We could tune for the "instantaneous" moment of power if we wanted to, but we would still be calculating, rather than measuring because we would be attempting to remove the value of time from the measurement - something we don't need to do with torque.

Once again, much like the boost vs. flow argument, I think people are over-thinking the "theory".
Just work practically - what metric gives us the most readily useful view of exactly what is going on at the exact, timeless snapshot that we are attempting to adjust?

My heads hurts. I am waiting for RG to chime in anytime :)

I think it is almost entirely semantics, personally. Everyone saying the same thing in a different way because they understand the same basis from a different perspective.




Important semantics though... :lol:

I know exactly what Jeff is saying and I am not disagreeing with him, though it's all style points.

The problem that I have is when people say "aw man we need more low end torque" - or "this car is slow because it lacks torque". As these are just silly ignorant statements; XYZ car is slow because it lacks power / a usable powerband - whatever. But the metric is power...not torque.

But ultimately yeah - most of us are saying the same thing, just from a different perspective.

Well, when they say "this car is slow because it lacks torque", it does need more "low-end torque"!
The problem is you can't feel torque because you exist in a space which is constrained by time.
You feel the power of acceleration, which is defined by time. So, in that instance, they are talking about power, even though it is defined by torque.

But, when you get that power, you are doing so by increasing torque.

hey you guys - how about you quit messing about and give some useful advice over here ...

https://www.rx8club.com/showthread.p...27#post3427427

250 to 275 is perfect.

Can hall people and accerate on the freeway.

It's too bad all the HP is too much.

You either buy small HP or Bi HP.

They don't offer what's practicle.

Haha thanks Brettus :)

As someone who has daily driven a car with 660rwhp I can say....it was too much. REALLY fun, but not much use other than burning up sets of BFGs and destroying rear ends, clutches and torque tubes.

All in all I would say MM has it right, about 9:1 is just perfect. My vette when it was cam and bolt ons was no less of a blast to drive than after I supercharged it.

And now my boosted Rx8 with 300+ feels just perfect. More than enough to put a smile on my face and easily enough to get into trouble :D:

wish i had a little bit more power, 200lbs less and 2k more revs

You guys are such a bad influence. Really.
Once again making me contemplate F/I.

If you are not greedy... you can do FI very reliable and fairly cheap.... as long as you are only shooting for 270WHP.

But most people get greedy.

Too true :sad:

Pun intended? Greddy? :cool:

Greddy with the AP, AEM intake and an oil/water CHRA is pretty much spot on for a 10:1HP car.

I no can haz torks?

when you can't hit full boost in 2nd gear without going sideways you are starting to have too much power. trust me on this.

yes - isn't it nice to think you CAN have too much power but are able to dial it back to "just right" .

lol yep, my vette used to roll out of traction in 4th with full throttle. :Eyecrazy:

I'd say a good number you can really put down on teh RX-8 and still have fun is about 550whp...

once you break that it gets scary and its not fun anymore...its more of a "preventing death" kind of deal..lol

Chris

Lol. Try putting all that through the OE diff, tranny, axles and DS as you go around the roval at California Motorspeedway.

550 in an RX-8 would be fun exactly once.