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Old 02-24-2004, 05:59 PM   #1
suby_dude
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Default More Torque? more HP?

on a WRX track (STI folks welcome too) setup.... which would you rather have....

More Torque? why?


More hP? Why?


Track as in Road Course... i know there's short and long courses... but in general...

SD
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Old 02-24-2004, 06:24 PM   #2
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the question doesn't make sense.

I could say, I want more power in a particular curve, which would be mathmematically equivalent to saying I want more torque in a certain curve...
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Old 02-24-2004, 06:36 PM   #3
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sorry... i mean... peak hp and peak torque.
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Old 02-24-2004, 06:38 PM   #4
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Both...

Thinking about headers? If so I'd say go for it because you are only going to be losing a bit of torque down low but increasing HP and spool up a lot more. Plus in racing you are hopefully in the higher RPM range all the time. I'd say HP for the WRX though, saves that tranny a little bit.
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Old 02-24-2004, 06:46 PM   #5
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Quote:
Originally posted by NegativeC
I'd say HP for the WRX though, saves that tranny a little bit.
i'm still on stock tranny w/ 350 ft-lbs of torque at 4500 RMP.

SD
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Old 02-24-2004, 09:33 PM   #6
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if the track has alot of turns, torque would be more important, as hp is not what helps you accelerate, torque is..
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Old 02-24-2004, 09:36 PM   #7
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i guess what i'm really looking for is the ultimate track car setup...

can anyone post some dyno sheets of a car that's been setup for track.... (gary? )

i'd like to see the hp/torque and how they compare... or better yet...

here's my dyno chart... what would be optimal in your own opinion?
[img]http://www.subydude.com/images/projectsuby/dynocharts/800/800/Subydude_dyno_24L.jpg[img]
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Old 02-24-2004, 09:43 PM   #8
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here's ur pic suby dude
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Old 02-25-2004, 01:50 AM   #9
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from crawford engineering

Quote:
Torque is what you feel, Horsepower is what you talk about.
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Old 02-25-2004, 01:53 AM   #10
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I think what jmott means is hp is torque. All you want is the longest flattest torque curve you can get. That will make more hp. I dont know where these saying about hp is what accelrates or you feel torque etc... come from since hp comes from torque times rpm times a constant.

Anything that makes more hp is also making more torque at that given rpm.
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Old 02-25-2004, 02:07 AM   #11
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hp is basically a measurement of torque over time. 1hp is the ability to do 33,000 lb/ft of work in one minute. One lb/ft of torque is basically one pound of force pushing against a 1foot lever attached to the crank shaft. Use 5lbs of force- that's 5lb/ft of torque. The faster the rpms of the engine, the more "work" can be gotten from a given torque amount - that measurement is hp.


Oh yeah- one interesting thing is that torque and hp will ALWAYS be the same amount at 5252 rpms.

Last edited by ElTorrente; 02-25-2004 at 02:13 AM.
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Old 02-25-2004, 11:52 AM   #12
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So how do WRC cars, which claim to be limited to 300hp, push out so much torque - I've seen numbers in the 500ft/lb range quoted.

It seems that they either have to have torque curves that drop rapidly at higher rpms or they develop max torque at v. high rpms.

Maybe I'm all confused!
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Old 02-25-2004, 11:56 AM   #13
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Default Just a thought

I don't know what suspension you are currently using, but for road courses in a WRX, the right suspension/tire setup is going to get you much faster laps than with only hp mods, due to the natural tendency of the car to understeer and slide around in general. (Unless, of course you already have a dialed track-tuned setup.) In my experience with it, I was lapping 3 to 4 secs faster at near-stock 240/250 hp with a decent alignment and more neg camber, (and better tires), than I was earlier with 280/290 hp (with chip), stockish alignment and stock tires. When I went back to the chip I was maybe only 1 sec faster still, so the hp really didnt make THAT much difference. It may have made more of a difference on another track but I doubt it. (The extra hp also brought more understeer back into the equation coming out of turns, and without a brake upgrade I had to brake earlier anyway, negating some of the hp/speed gains on the straightaway.)

Looking back, I'd trade every dollar I ever spent on WRX power mods, for nice coilovers/camber plates, dedicated track wheels/tires, corner balancing, Cusco center rear-biasing diff., and big brakes. That's what makes the car faster on most avg. tracks. (The fastest WRX lap at Willow Springs I know of, other than a full race car, is around 1:38. That was done with fully stock motor and suspension, but with track tires and alignment including rear toe-out and max ft camber. Many 300+ hp WRX's have never broken 1:40 or even 1:42 on the same track.)

Again, if you already have a dialed track suspension and tires, more hp can't be a bad thing, but it's not the first thing. What track are you running at mostly? Laguna Seca? Infineon?
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Old 02-25-2004, 12:06 PM   #14
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Quote:
Originally posted by suby_dude
i'm still on stock tranny w/ 350 ft-lbs of torque at 4500 RMP.

SD


Please include pics when your tranny goes KABLOOWIE.

340 horse and 350 torque, at the wheels! And you want more? Go for torque or better yet, change the ratios in your gearbox. I assume that we're talking a worn stock 5 speed. Even with all your power, I doubt whether you ever see more than 135 at the track so shorten those ratios.

Quote:
Originally posted by suby_dude
i guess what i'm really looking for is the ultimate track car setup...

can anyone post some dyno sheets of a car that's been setup for track.... (gary? )...
Now that I've read that bit, you really should get some new gear ratios. Put in an STi 6 speed and lower 5 and 6 (even though you'll probably never use 6th at the track). Maybe even put in a shorter 4 as well.
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Old 02-25-2004, 12:08 PM   #15
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Quote:
Originally posted by leecea
So how do WRC cars, which claim to be limited to 300hp, push out so much torque - I've seen numbers in the 500ft/lb range quoted.

It seems that they either have to have torque curves that drop rapidly at higher rpms or they develop max torque at v. high rpms.

Maybe I'm all confused!

Exactly, Low end torque. You have HP restrictions you keep the peak torque VERY low. Unless there is another way...
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Old 02-25-2004, 12:21 PM   #16
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hp = (tq*rpm)/5252

WRC has a 300 hp limit so you run the torque to as high as you can go.

For example for 300 hp at 3000 rpm you need 525.2 ft lbs. However for 300 hp at 7000 rpm you only need 225.1 ft lbs. It makes for a very peaky ride that feels slow because you have to taper the torque so much to not go over the limit.
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Old 02-25-2004, 12:22 PM   #17
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The HP curve reflects that huge torque in that those cars make 300ish hp from like 3krpms on up.


Quote:
Originally posted by leecea
So how do WRC cars, which claim to be limited to 300hp, push out so much torque - I've seen numbers in the 500ft/lb range quoted.

It seems that they either have to have torque curves that drop rapidly at higher rpms or they develop max torque at v. high rpms.

Maybe I'm all confused!
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Old 02-25-2004, 12:41 PM   #18
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Quote:
For example for 300 hp at 3000 rpm you need 525.2 ft lbs. However for 300 hp at 7000 rpm you only need 225.1 ft lbs.
Quote:
The HP curve reflects that huge torque in that those cars make 300ish hp from like 3krpms on up.
It's pretty cool that they can do that. But with their budget, I guess you can pretty much do anything!
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Old 02-25-2004, 01:43 PM   #19
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It's the restrictors in front of the turbo. They can only flow so much air, so the engines have to make as much use of it as possible at low rpms. You can only suck so many CFM through a 34mm restrictor. Once the flow through the restrictor reaches sonic speed (1100fps, more or less), then it doesn't matter how fast you spin your turbo, it isn't going to get any more air...

Sorry, hijack.

Give me peak HP and an efficient continously variable transmission. [edit] so I can stay at my HP peak all the time .[/edit]

Last edited by Chromer; 02-25-2004 at 06:55 PM.
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Old 02-25-2004, 04:40 PM   #20
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Yeah they dont actually dyno wrc cars to make sure they dont make more then 300hp they just put a restrictor on them that theoreticaly limits them to 300hp.

You should just be tuning for the best torque curve, peak numbers dont matter. If you loose a little on your peak but make alot more torque from 5-7k rpms then its worth it as you will have more area under the curve.
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Old 02-25-2004, 05:13 PM   #21
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Default Re: More Torque? more HP?

Quote:
Originally posted by suby_dude
on a WRX track (STI folks welcome too) setup.... which would you rather have....
More Torque? why?
More hP? Why?
Track as in Road Course... i know there's short and long courses... but in general...
SD
For a road course you aren't as concerned about hp in the lower rpm ranges since you don't spend time there. You want to be able to stay in the meat of the hp range as much as possible so you pick a turbo and tune your car based on the track and gearset you are running. AM cars in autocross run special transmissions that keep the rpm at the peak hp and continuously vary the gearing to put down as much hp as possible.

I autocross and its a totally different equation there. From my data logs I've seen that I spend a significant amount of time in the 3000-4000 rpm range. In that case its more important to have as much hp as possible in that range so the car is set up differently. Big turbos on a 2L engine are bad for auto-x but probably good for road racing.

As far as how fast you accelerate you should only look at hp. Your hp multiplied by your speed is proportional to your acceleration. If you use torqe then your acceleration is proportional to your torque x speed squared which is impossible to figure in your head.

Here's an example that will help you get a feel for how it works for a given weight car and neglecting aerodynamic losses:

-At 30mph and 300whp you get X g's of acceleration
-At 60mph and 300hp you get X/2 g's (half as much) acceleration
-At 60mph and 600whp you get the same acceleration as you got at 30mph with 300whp

You might say to yourself... my car doesn't feel like the accleration drops off much as I speed up. That is true but its because as you speed up your rpms increase which increases your hp output to a certian point. That makes the acceleration feel somewhat constant especially in the lower gears.

So, whp and weight mean everything. Never even worry about the torque curve unless you are figuring how to size your drivetrain. Things break based on torque, not hp.

hope that helps.

Bottom line, don't worry about torque when trying to figure out how fast your car is going to be. Use whp and weight.
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Old 02-26-2004, 12:30 AM   #22
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A friend who makes his living writing ECU maps for major race teams (at $500 an hour) says he would gladly trade 50 hp on the top end for 50 lb ft at the bottom end.... except at Le Mans.
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Old 02-26-2004, 10:01 AM   #23
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Quote:
Originally posted by KoneKiller
A friend who makes his living writing ECU maps for major race teams (at $500 an hour) says he would gladly trade 50 hp on the top end for 50 lb ft at the bottom end.... except at Le Mans.
Thats the same as saying he will trade 50hp at the top end for 25hp (or something much lower) at the bottom end. Remember Torque x RPM is proportional to HP.

Any car that has to operate at a significant amount of time in the lower rpm range would be very concerned about bottom end. The slow sections are where you lose the most time so 25 more hp in a slow section may make up more time than 50hp would in the fast sections. Remember also that acceleration is proportional to HP x speed so you pick up a lot more more acceleration at slower speeds than at faster speeds for a fixed HP increase.
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Old 02-26-2004, 10:31 AM   #24
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Quote:
Originally posted by mbiker97
hp = (tq*rpm)/5252

WRC has a 300 hp limit so you run the torque to as high as you can go.

For example for 300 hp at 3000 rpm you need 525.2 ft lbs. However for 300 hp at 7000 rpm you only need 225.1 ft lbs. It makes for a very peaky ride that feels slow because you have to taper the torque so much to not go over the limit.
And visually, here's a plot of a fictitious tq vs hp curve with HP limited to 300. Further, say 300 hp is generated through 3000-7000 RPM.

What's so counter intuitive about this limit is it's backwards from the way we normally talk about hp vs tq. We usually want the torque curve to be as tall, flat and long as possible, which is the direct opposite case here.

The resulting torque requirements illustrates mbiker97's post:
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Old 02-26-2004, 10:33 AM   #25
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Quote:
Originally posted by vizor
And visually, here's a plot of a fictitious tq vs hp curve with HP limited to 300. Further, say 300 hp is generated through 3000-7000 RPM.

The resulting torque requirements illustrates mbiker97's post:
I want my HP curve to look like that!
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