Whats the Fastest your legacy's gone

skid542 · Post by **skid542** » Wed Aug 16, 2006 4:02 pm

Brat, like I said I've never driven a turbo so I don't know what rpms you're spinning at. It was just something I was throwing out. It very well may be completely invalid.

However, for the record, torque is what determines your top speed. Horsepower determines how fast you get there. Power is in units of work/time. I know the HP is kinda funking but I know a watt = N*m/s. Torque is the force that balances drag and rolling friction, T = F*wheel radius where F => Drag. Right?

Splinter · Post by **Splinter** » Wed Aug 16, 2006 4:10 pm

Lee, wtf are you talking about?

Horsepower is a mathematical calculation based on torque and RPM, nothing more.

All horsepower does is give you an idea of your 'top end torque'.

skid542 · Post by **skid542** » Wed Aug 16, 2006 4:59 pm

Then let me make a distinction between horsepower and actual power.

Power is defined as work per unit time. Work is defined, kinematically, as force over distance. A kilowatt has a very exact definition when someone says their engine produces so many KW of power.

So power determines how fast you get there. Obviously since it has a time unit it does relate to your top speed but I was under the impression that the torque available at that speed played a greater role than the power available.

I'm an aero engineer, our use of powers and such are different than the ME guys so maybe I'm just completely off my rocker, but surely someone understands what I'm getting at?

entirelyturbo · Post by **entirelyturbo** » Wed Aug 16, 2006 5:47 pm

Well, I should factor in the AWD on mine. It probably makes a lot more difference at those speeds.

And, while I'm thinking about it, my driver's door is misaligned from the accident and subsequent body-shop hack job a little over 4 years ago, so I'm probably getting a little extra wind resistance from that (makes a LOT of noise at 112mph).

Brat4by4 · Post by **Brat4by4** » Wed Aug 16, 2006 6:27 pm

skid542 wrote:So power determines how fast you get there. Obviously since it has a time unit it does relate to your top speed but I was under the impression that the torque available at that speed played a greater role than the power available.

I'm an aero engineer, our use of powers and such are different than the ME guys so maybe I'm just completely off my rocker, but surely someone understands what I'm getting at?

Dude, you lost sight of the rocker a long time ago...

I'm not going to go into a detailed explanation of why this is wrong. Just some examples...

1. So you want peak torque to get top speed... You would need a monstrously long 5th gear and final drive to keep 3700 rpm in our engines at 130+. How come we would rather be sitting at 5500-6000 rpm when pushing top speeds? It is far away from peak torque.

2. You are racing a honda at 120 mph. He is making a mere 95 lb/ft while you are making a healthy 130 lb/ft at the wheels who will pull away? Answer: The honda will smoke you since he is spinning at 9500 rpm and making over 171 hp while you are making less than 92 hp (with a stupidly long 5th gear at 3700 rpm). Torque numbers are not the whole story.

3. hp/weight numbers tell you (with some other factors) how fast the car will go and how much it can accelerate in a quarter mile. torque/weight numbers tell you nothing, they do not correlate with any commonly measured performance values. torque is only useable depending on the rpm it is at.... that's why they have hp. Yes, it is derived from torque, but tells a lot more of the story for things like top speed. Torque numbers are great when you are pulling a trailer from near idle revs.

I am out of breath, so I hope this works. And with all that said, I like cars built for lots of torque. More fun to drive, I don't care about the 1/10 of a second in the 1/4 and the 10 mph of top speed I leave behind without the extra top-end power.

skid542 · Post by **skid542** » Wed Aug 16, 2006 9:01 pm

I'm not talking acceleration so leave all those arguements out.

I'm talking steady state conditions, if you had an infinite long straight away. Who will reach a higher top speed, the car with 130ft/lb or 95 ft/lb? Assuming the two cars are otherwise the same, same drags/frictions/drivetrain losses.

I don't have the dyno graphs memorized between the turbos and NA's so if the turbo does have more torque than the NA at top speed then yeah I would expect the turbo to out top the NA. However, I still stand by my original point of torque determining top speed instead of power.

Does nobody remember the days of high displacement carbed torquey engines of old that would push those draggy ass muscle cars at 160 mph?

Brat4by4 · Post by **Brat4by4** » Wed Aug 16, 2006 9:39 pm

skid542 wrote:I'm not talking acceleration so leave all those arguements out.

I'm talking steady state conditions, if you had an infinite long straight away. Who will reach a higher top speed, the car with 130ft/lb or 95 ft/lb? Assuming the two cars are otherwise the same, same drags/frictions/drivetrain losses.

How can you reach a higher top speed without acceleration? I'm lost. And if everything is the same with both cars the one with more torque is also making more horsepower...

skid542 wrote:I don't have the dyno graphs memorized between the turbos and NA's so if the turbo does have more torque than the NA at top speed then yeah I would expect the turbo to out top the NA. However, I still stand by my original point of torque determining top speed instead of power.

Nothing to memorize, the turbo has more of everything above 2500 rpm and the gap never closes. The turbo has numerically higher lb/ft than the NA makes hp until 6000 rpm.

I honestly don't know what point you are trying to make. The actual torque the wheels see changes with the gears. The torque on the input shaft stays relatively the same for specific engine revolutions. So more torque in 3rd will not get you a higher top speed because the engine will run out of revs. 5th gear is needed with less torque at the wheels. But its still hard to run out that gear because friction drags the vehicle down until you are revs can't give enough Power to overcome the resistance. Your torque drops as your engine revs beyond 2700 rpm... but you still accelerate to a top speed.

That's my last try. Signing out.

skid542 · Post by **skid542** » Wed Aug 16, 2006 10:03 pm

Edit: I had a longer reply here but then felt like I was probably coming off like an a**hole to which I didn't mean to.

I still stand by my stance that ultimately torque determines top speed. A, Power is not a force, only a force can balance a force. B, how do you top out a car with a CVT?

Brat4by4 wrote:Nothing to memorize, the turbo has more of everything above 2500 rpm and the gap never closes. The turbo has numerically higher lb/ft than the NA makes hp until 6000 rpm.

Cool, I didn't realize it was that easy. I have learned something about our cars I didn't know, thank you. Though I think my peak torque is around 4500 and not 2700.

I brought this all up as a possible explanation for why our NA's were having reports of higher top speeds than a couple SS reports. My explanation is obviously wrong to explain these couple of cases. Fair enough.

I'm signing out as well.

aspect · Post by **aspect** » Thu Aug 17, 2006 2:13 am

Fastest I've gone in the legacy is about 160km/hr. Impreza, maybe 135.

Previous owner of the legacy posted on here once that he was able to pin the speedo at 220. Not really my style though

Psychoreo · Post by **Psychoreo** » Thu Aug 17, 2006 4:51 am

ease up on this Hp vs torque battle. Horsepower is an oddity in measuring true power and yes, torque is a twisting force. But they rely on each other in this simple equation:

Power (hp) = Torque (ft-lb) x RPM / 5252

thus you're both right, just neither is understanding each other.

BAC5.2 · Post by **BAC5.2** » Thu Aug 17, 2006 5:57 am

Girls, please, your both pretty.

Horsepower is determined by torque, right? It's a mathematical equation.

Horsepower = (torque x rpm)/5250

High RPM = higher HP. That's why HP is an unreliable number. It is skewed by high RPM

If you make 100lb-ft at 20,000 RPM, that's 380hp. So at 20,000 RPM, you aren't doing a lot of work, but the little work you are doing is happening really quickly.

Torque is directly related to the top speed of a car. Horsepower just gives you an idea of what the torque curve looks like.

If you make 300lb-ft at 2000 RPM and make 500hp at 6500 RPM, you'll find out that you make 403lb-ft at 6500 RPM. So from that, you can gather that your torque curve is flat as Calista Flockheart's chest.

So what does that mean for top speed?

RPM dictates speed. If the trans isn't spinning things fast enough, there's your limiting factor to top speed.

The hp figure is a more palatable way to let you know how much torque you make later in the rev range.

So having more horsepower, means that you continue to make a lot of torque through the rev range.

Therefore, top speed is totally dependant on torque.

scottzg · Post by **scottzg** » Thu Aug 17, 2006 9:55 am

laughing.

fireytom · Post by **fireytom** » Thu Aug 17, 2006 7:34 pm

I managed 130mph on some back roads between Augusta and Atlanta (GA). Maybe because my engine only has 60k on it, its willing to do so

Splinter · Post by **Splinter** » Thu Aug 17, 2006 8:39 pm

BAC5.2, have I told you lately how much I love you?

I wish I could explain stuff that well

anthonyle2002 · Post by **anthonyle2002** » Sun Aug 20, 2006 11:06 am

120mph down the freeway.

...hey, i was late for a hot date.

SuperRallyRoo · Post by **SuperRallyRoo** » Wed Aug 23, 2006 2:54 am

Burried the needle on the 5mt touring wagon @ 145mph but the tach kept going... So im guessing i topped it out at about 150mph. Closed road professional driver being me of course...
Had the rally car up to 110 on the taholah (sp?) stage at doo wops. Says the co driver...

Richard · Post by **Richard** » Wed Aug 23, 2006 6:21 am

I did 130 for over 30 minutes through the desert in May 2005 while driving it back from LA. I only slowed down for turns, which there were few of. I figured that if it didn't die out there I had a good car. Didn't see a friggin cop from outside Vegas to Breckinridge. I pegged the needle in my 93 briefly. The plastic sunroof visor thingey chattered the whole time and my ears popped soooo bad when I finally closed the sunroof, which is what made me slow down.

Wolfeyes88 · Post by **Wolfeyes88** » Thu Aug 24, 2006 9:15 pm

I havn´t hit triple digits in my suby... yet. The fastest I´ve gone was 95ish on I75 just aouth of Atlanta.

wiscon_mark · Post by **wiscon_mark** » Sat Aug 26, 2006 4:22 am

100 mph...then I ran out of road...I mean track...

monty's legacy · Post by **monty's legacy** » Sun Aug 27, 2006 9:02 pm

I got my old 91 Lsi up to 95 and considering blow suspension and shitty tires I wasn't going any faster

206er · Post by **206er** » Mon Aug 28, 2006 6:05 am

130ish down a steep part of I70. had to back out of it.

asc_up · Post by **asc_up** » Mon Sep 11, 2006 7:32 am

subyluvr2212 wrote:Seriously, I'm thinking about calling BS on you N/A guys.

My car can do 112, just like the magazines say. No more.

That's windows-up, A/C-off (or not working ), pedal-to-the-floor for about 15 seconds straight. Right at 5krpm IIRC. On a highway, flat as can be like all of FL, no wind.

i've gone 135 with mine and it's an N/A.
BUT i have a proecm piggy back so it removes the 112 governor.
so it goes faster than the magazines say.....

Richard · Post by **Richard** » Mon Sep 11, 2006 7:46 am

Are there governors on t-legs? I've never hit it, so I think.

asc_up · Post by **asc_up** » Mon Sep 11, 2006 8:44 am

i dunno on t legacys but there are on n/a.

scottzg · Post by **scottzg** » Mon Sep 11, 2006 9:31 am

the 112 limiter, is it tied to the speedo or the tach?

ive seen 115 on the speedo.

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Whats the Fastest your legacy's gone