Turbo with most increase in torque?
 

I'm curious to know what the turbo with the highest gain in torque is for the FD? I guess I'm thinking mostly torque before 4500-5000 RPM. We always see HP numbers, but what about torque? I imagine ball-bearing turbos have better torque because of the fast spool up times?...Anyhow, any info would be great...

Horse power is a calculated value from the engine torque. All turbos perform the same function (compress air to the intake), therefor the power increase will be in the same ratio. The only thing that can be effected by the turbo design is the volume of air supplied at a given pressure (total power increase) and the slope of the power curve (rate of peak power).
So the title of your thread and the content is two different questions. "Highest gain in torque" and "torque before 4500-5000 RPM" are two different charactoristics. Which are you asking?

I guess I'm looking for more torque before 4500-5000 RPM. What I don't understand is how come some cars gain so much horsepower and little torque from a turbo? Is this because the horsepower takes so long to come on?

yes and no. It's not because they dont gain torque, it's because they dont gain it until the upper rpms, where it disappears and magically becomes mondo HP! ;)

As the others have explained, you are under the most common misunderstanding in the auto world -- that torque and hp are not directly related...

As far as aftermarket turbos with the best low-end torque, none of the singles will be as good as the stock twins. Here's my list of good low-end turbos:

*M2 ball-bearing upgraded twins -- sequential
*Pettit upgraded twins -- sequential
*BNR upgraded twins -- sequential
*TO4S
*Apexi RX6

You can also see a really good comparison of horsepower curves at: http://www.catenet.net/dyno.php (thanks Wargasm for the great site)

You can see that even the quickest spooling singles don't make the same power as the stock twins until 3500-4000 rpm. The bigger turbos are even worse with some of the T-78 dynos not even EQUALLING the stock twins until after 4000 rpm. No thanks....

don't forget about the 99-spec's....... ;)

True, but since we're talking about a massive upgrade, I don't think those count. For that matter, take off the Pettit turbos. So far, it looks like only the M2 and BNR are really meant to handle the higher boost levels (15+ psi). Not that I wouldn't consider getting the 99-specs if my turbos went out.... :) (When your mechanic switches back from a T-78 to the 99-specs, it gets your attention.)

watch for the m2 turbosdyno charts that are going to come in the next couple days. Im expecting the best low end power of any to date.

jason

Thanks a lot for all of the replies. I didn't think torque and HP were "directly" related, but to some degree. From everything I've read before, the M2's look like the best bet. I've read up on the BNR's too, but I think with the ball-bearings you have an advantage.

Funny, I just finished reading a Dyno article in the latest Grassroots Motorsports, and they specifically said horsepower is a function of torque and rpm and even gave the formula. They claimed a dyno only measures torque, and then derives the horsepower curve. I'm still confused..........

Exactly. This is what was stated in the above replies. I'm not sure why you are confused?

Horsepower is just a mathmatical derivation. The dyno does just measure the "force" of the engine -- torque.

HP=torque*rpm/5250

The torque is the true amount of force the engine can generate. Horsepower is the amount of work an engine can do. The engine accomplishes more work at higher rpms. This is why a typical pushrod 350 V8 can make 2 times the torque of a smaller, higher-revving engine, but not make any more horsepower. It also explains how an F1 engine with only 260 ft-lbs of torque can make 900 horsepower -- at 18000 rpm, while a diesel can have 500 ft-lbs but only make 240 hp -- at 2500 rpm.

I would have gone for those myself rather than the 99-specs I settled with (roughly the same price), but after reading the super-long post regarding them I changed my mind. I believe you said 15 psi wasn't even enough to get into the efficiency range of those turbos. Also, the precision needed for tuning with a pfc along with horror stories of XS turned me off...... for now ;)

What about A-Spec's twin turbo kit? Does anyone know anything about this kit yet?

I believe they are in the final tuning stages. The info A-spec has put out so far looks VERY promising....

that kit is non seq i believe....while it should put out big power it wont have the downlow that seq would.

im excited about that kit though...tis the one Im watching...besides mine. :)

j

Here is a the problem with what is being asked. Forced Induction (FI) really just amplifies what the motor is doing. Rotaries aren't know for their torque. The 2 rotor just doesn't really come alive till 3500 or 4000 rpm. This reason is why Mazda went with such a complicated twin turbo system-to get low rpm power. The 3 rotor has so much more torque because it is a significantly bigger motor. If you want to learn more information on this topic/idea then go look at Honda NA to FI conversions. Look at the dyno charts and you will see the correlation. Most of the time you can see that torque is 30 to 40 percent over stock and is flat across the rpms (just like stock). It really looks like someone amplified the stock torque curve and as we know from the threads above, the HP calculations fall out of the torque curve.