bl1nk

Yeah, I was going to mention something about the psi but didnt know if the psi on turbo was the same amount of stress as the psi on a sc... guess thats common sense though lol...

Since turbos are providing more tq, and its mostly not until the 2.5-3k range... I wonder if theres a severe jerk of acceleration when you nail it from down low in the rpm range? Cause its gotta be like .... 2.1k rpms, 285 tq - 2.5k, 300 tq - 2.9k, 410 tq. Bet thatll wake ya up huh?

petepete

In the turbo cars ive hadwhen you floor it it feels normal for a couple seconds and then boom it hits you.

CrazyAl

This kind of thing is often confused and there are two parts to the explanation.

First off, HP and Torque: A lot of gearheads think of these as two different things. But the truth is that they are intimatley related together. HP is calculated from torque. The mathematical formula for American units (HP and ft-lb) is that HP = Torque * RPM / 5252.

This is how a dyno works. A dnyo measures torque only. (There is no such thing as a "HP sensor"). It then calculates HP from the torque measurement.

Note that if you look at the formula you will see that at 5252 RPM the two values are exactly equal. Any proper dyno chart using American unitswill have the HP and torque lines cross at exact 5252 RPM. So, mathematically speaking, below 5252 Torque is higher but above 5252 HP is higher. But they are related together. So if someone gave you a mod that added 10% more torque to your car, it would also add 10% more HP a the same time....anything otherwise is an impossibility.

It's common in the motorsports world to talk about "torque" when people are actually meaning low-end power and to talk about "HP" when people actually mean top-end power, but this is not technically correct. At any given RPM point the two are linked together.


Anyway, turbochargers have a reputation for delivering more HP and little torque. This isn't entirely true. Turbos, like centrifugal superchargers, are inefficient at low RPM. At lower engine speeds they just don't work very well. Consequently they don't provide much of anything at lower RPM (HP and torque). However at higher RPM they are very efficient and consequently they make a lot ofHP and torqueat that point.

Superchargers of the roots and screw type are very effective even at low RPM. Consequently they make a lot of power and torque at low RPM. At higher RPM they work well too, but sometimes a turbo is more efficient.

So, if we were to make a litte chart of Turbo/SC performance at different RPM ranges, we might see something like this:

Mod: Low / Mid / High

Turbo: Minor / Good / Great
SC: Good / Good / Good

...of course this isn't particularly accurate but the point should be clear.

bl1nk

Thanks.. I knew most of that but that cleared some stuff up. I still dont understand why they even have two estimations then... why even have HP if its just another way to measure TQ? Why not just have a "power" curve that measures your "power" throughout the rpm range... why should you need two different terms to measure it?

CrazyAl

Technically they are not the same value--TQ is a measurement of a force, and HP is a measurement of power...but if you have either curve you can simply calculate the other one. So, you're right, having both HP and TQ curves is redundant. So long as you had either one that provides all the information you'd need.

I suppose they are both listed becasue people are just used to it. To the average guy Torque readings are pretty much useless....but people love to hear HP numbers.

bl1nk

Maybe Im understanding this wrong... but it seems to me like.. you have 2 curves.. the TQ curve which starts high and slopes down, and the HP curve which starts low and slopes up... Those meet @ exactly 5252. Now the angle of the slope is dependant on how much power you have through your rpm range. Your max TQ is always before 5252 and on the TQ curve, and your max HP is always after 5252 and on the HP curve.. right? Why you cant just take the upper parts of both curves and use that to measure the power? Something like this...




When you say TQ is used to measure force and HP is used to measure power, is it accurate to say say that TQ initiates movement and HP keeps it moving? I know that alot of TQ is what you feel... that pin you to the seat feeling you get when you step on it, but what is HP? I mean, what does HP really mean... you hardly use any of the rpm range after 5252, so what good is it to really have high amounts of HP?

ECR5.0

Thanks for all of the info guys, those last post cleared a lot up, i spoke with the guy this morning, he was running a 93 oct tuneat 6 psi and got those numbers, like many people said he went with a twin turbo setup for lag purposes. I think a lot of people are forgetting this is only 6 psi, he can put more on it the system is built to handle to power, butthis tune was made to be very conservative. I hope im making the right move on this, ill keep everyone posted with pics and info. Thanks again for all of the info.

PS. The rims are raceline wheels

CrazyAl

This depends on what you are asking. If you are asking about what might be a convenient way for a racer to compare engines or mods, then sure, this method (like any arbitrary method) could work. However, it is not technically correct. The error comes when you say "measure the power". Torque is NOT a measurement of power....just the same way that inches is not a measurement of time. If you mean power in the true sense of the word, then Torque is not an appropriate term,any more than an inch is a measurement of time.

Here's another way to understand it. Imagine a linebacker in a football game. Torque is a bit like how hard he can push. HP would be like how hard can he push and run at the same time. HP is a measurement of power, exactly like "watts" in electricity. In fact, 1 HP is equal to about 750 watts. Power is a measurement of energy being applied per unit time.

bl1nk

Ahhh thanks.. the football analogy helped alot... I played alot of football

Turbosetch

Remember to..Turbos are far more efficent than S/C's. In other wordsmore output power with less input power. Its takes quite a bit of HP/TQ to turn the S/C with that belt. The turbos rob the power from the waste or exhaust. There is power loss here from constriction BUT its less then a S/C. Turbos can make more power over a wider band then a single S/C.

If you really want to have fun go with a sequential setup with a S/C and a turbo. The little wind up cars like the Mitsubishi Evolutions I used to tune guys would do it all the time. The S/C was geared to kick in and give tons of power in the low to mid-range and then a monster turbo would be spooled and kick in when the S/C would fall behind.

Also if you go with the turbos you should DEFINITLY look into methanol/water injection. Cheap kit for under $500 that will let you run more timing and boost with cheap gas. The cooling effects are so much greater than any intercooler it can lower EGT many 100's of degrees. EGT's are a problem with turbos you have to keep and eye on. Its neat when you can pull over and light a smoke on your turbo..but your turbo don't like that!! lol.