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

 

Torque is more important then HP.
Have you seen the Dyno Comparison thread? Some of those turbos are making pretty big HP / TQ at low rpm's (contrary to conventional internet wisdom)

A turbo shouldn't peak at 3-6k RPM, if so something is wrong.

If you're looking for a car with 270 - 300hp, that can be achieved with either a Turbo OR a Supercharger, it is really going to come down to personal preference.
Had an FI car in the past? I'd encourage you to see if there are any local 8's that are FI'd, talk to them or maybe con them into letting you go for a ride in the car to see what you like best.

 

Torque is a function of horsepower; not more important than....

you cannot look at two static values and decide how the car will drive - you need at least FIVE (preferably 6).

1 - HP Peak
2 - RPM at HP Peak
3 - TQ Peak
4 - RPM at Tq Peak
5 - Vehicle Weight

*6 - Gear Ratios


Anything that doesn't have at least those 5 pieces of info isn't going to tell you much.

Example an engine that makes 9000lb/ft of torque and 100 HP is faster or slower than an engine that makes 100lb/ft of torque and 9000 HP.

Hint: with the same gearing - option 2 will out accelerate option 1 evertime.

 

If you're serious about getting into FI and you're already searching around on the boards, I'd suggest you go to the next step and starting reading some books about it:

http://www.amazon.com/Turbo-Real-Wor...5402559&sr=8-3

http://www.amazon.com/Turbocharging-...d_bxgy_b_img_b

http://www.amazon.com/Street-Turboch...=pd_cp_b_3_img

 

Or read my sticky on FI....

 

Start with engine basics; torque horsepower etc.... then realize it all boils down to airflow.... how much of it you can stuff in the motor.

Then start reading FI info and it will all become fairly clear.

 

Speaking of books wasn't someone writing one out on the RX8 that included commentary from most of the major contributors to the board plus other noted rotary/rx experts? I've been waiting on that one but haven't seen an update in a few months.

Pretty sure it was slated to be published 1Q09 so I'm hoping it'll be presaled on Amazon soon.

 

& don't forget that's how much air MASS you can stuff into the combustion chamber per unit time, not air VOLUME.

http://en.wikipedia.org/wiki/Mass_flow_rate

 

Horsepower is just a calculation based on torque times rpm. I believe the formula is:

HP = (Torque x rpm) / 5252

That is why you see diesels have such high torque and such low horsepower. They don't rev very high, but make lots of torque at low rpms. Conversely, a NA rotary makes very little torque per engine revolution, but it can make that little bit of torque a lot of times in a minute.

 

Torque is a static measurement of force horsepower is a measurement of work... so in your example

More Horsepower wins.....always. But Like I was saying there is more you need to know in order to be really sure how the engine will feel.

 

we can assume a lot of the data is constant for the rx8.

the gearing is the same, the engine is the same, the vehicle weight is the same.

if you are looking at the possibility of the MM 3071R turbo, then get it. Not only will it generate far more torque then the SC, but you can do 400 whp on it if you wanted AND you get the fastest spool times. I'm not aware of any drawbacks of this setup.

 

to answer your question, torque is what you can feel. It's what pushes you back into the seat. Something you don't feel on the stock rx-8 cause it only makes 130 torque.

In simple terms, horsepower is more about vehicle speed, torque is acceleration. Everything gets confused because of gearing, vehicle weight, and power band.

Luckly for us, the rx-8 has a wide power band

 

A SC is belt driven, so when it spins, it's able to generate power, but it is TIED to engine rpm. You're stuck with it.

A turbo is driven by exhaust gas. If you want 9 psi, you setup your boost controller to watch for 9, and when it sees over that, it opens the wastegate and allows air to bypass the turbo, keeping the boost at 9. So you're able to tell it how much boost you want, and where. If you wanted, you could set it to give you 5 psi at low rpms, and creep upwards so it feels more like a SC.

At any rate, look at the dyno comparo page. You'll notice even at the low rpms, the SC's advantage is not apparent. This is because the 3071R (and greddy turbo) spool up so fast that boost is just about immediate.

To put it in perspective - imagine you're in a drag race. Are you going to let off the clutch at 1,000 rpm and then give it throttle? If you do that, then yes, the SC would have the advantage cause you will have to wait till 3k for enough exhaust to spool up the turbo.

HOWEVER, if you rev it to 3k and let off the clutch, you'll get that boost right away.

The next time you're on the highway, watch your rpms. Tell me when you are under 2,800 rpm. If you're under that, then you'll have a delay before you hit 12+ psi. If you're over it, you'll get 12 psi (or whatver your boost controller is set to) instantly.

That is why turbo lag is not an issue if your turbo is properly sized.

If you pick a huge *** turbo that can go to 900 hp on a car with an engine that isn't going over 400 hp, you're going to see lag, and you might not get your boost till you're at 7,000 rpm... in that case your car will be a dog and you need to reconsider your priorities

The only time I've had turbo "lag" is when I was at 30 mph and still in 6th gear. Yeah, it's not going to be fully spooled when I mash the throttle for about 2 seconds.

 

Mark Warner.

Should be out in February, IIRC.

I don't even understand that thread!

 

That is not good..... maybe I need to try to make it clearer....


Or you can quit drinking Monsters...