We all know how superchargers and turbochargers work... atleast we all should know. However I remember someone posting, stating that the turbo/superchargers don't start giving added power unless either its floored or pulling a load. Now using that statement... well first off is that a true statement?.. but using that statement, when you buy a car that has turbo and is rated at like 150hp(i dunno maybe @4000rpm). Doesn't that mean that the engine will never produce that much power @4000rpm, unless it was floored. So by saying this that car is slow as ***** unless its fully floored (even tho its still slow as ***** with only 150hp). I am curious cuz my friend has a 2000 A4, and it only has 150hp and you kno how much that car weighs? 3400lbs. and its the one with the turbo. BTW, its amazing how no matter what kids drive they always think their car is faster when it apparently isnt, ***** mentality. But what I'm asking is the fact that turbo doesn't work unless open throttle is used, doesn't that mean if you put an 8cyl car against a 4cyl turbo car, and the 8cyl has 300hp, and the 4cyl turbo has 320hp, and both of their throttle is pushed only 1/4 of pedal distance (not flooring) that the 8cyl will win, cuz the 4cyl is nothing unless that turbo is kickin in at full throttle?

 

Any engine is going to make less than max power at less than max throttle, thats why when you dont want to take off from the line as fast as possible you dont give it full throttle. As for the boost issue, you wont get as much boose at less than WOT but you'll probably still get some ammount of boost. Find a turbo car that has a boost guage on the dashboard and watch it.

 

As my head spools down......

Who would race at a 1/4 throttle?

 

@ss muncher, who mentioned racing, it was a hypothesis, a test, apparently you can't pick that up, down? has your head ever been spooled up

 

@ss muncher? Hmmn..

Looks like you're talking about a race to me.

My guess is you know absolutely nothing about the workings of an engine, or how/when it makes or can be made, to make HP and torque, or you wouldn't have asked such a stupid freaking question (and spent much more bandwidth that was needed) to ask it.

If you want to play "gee, what if's" and all your local benchracing buddies have tucked in for the night, we do have a board especially for these types of questions.

Cheers.

 

Once again ur dropping ashes on the keyboard. In the words of myself and my friends, u are queer, fvck off!

 

OK, lets cool it so questions can be answered before this gets locked. In order for a turbo to give its full potential it needs to be spinning fast, thus it works better on a car that has a higher redline. But when you say a car with a V8 and a 4cyl at equal throttle, just because the V8 has more HP and the 4cyl turbo needs high rpms doesn't mean the V8 will win, there is a whole HP/weight ratio you have to factor. If the V8 weighs 4000 lbs while the 4cyl turbo, let's say a RX-7 those cars are real light and I believe have gearing, another factor that comes into play not to mention the gears of the tranny the RX might just win.

 

All engines produce max HP only under load. Lets say a 300 HP NA engine makes 300 HP at 5500 rpm. With the car in neutral and reved up to 5500 rpm it's not making 300 HP. Cruising down the highway in second gear at 5500 rpm it's not making 300 HP either. Under full load is the only time you'll ever see that max HP.

HP is what you feel when you go to pass a car on the highway at 60 mph. Torque is what you feel accellerating from stoplight to stoplight.

Lets do a theoretical situation. 2 identical cars. Both make 300 HP at 5000 rpm. One makes 300 pounds of torque at 4000 rpm and the other make 325 at the same rpm. The one with the higher torque would easily win any race. Little 4cyl engines produce very little torque compared to V8's. By using boost to build more HP, they can use that little amount of torque quicker.

Remember the old VW beetle. The 1200cc engine (74 CID) only produced about 65 HP. It wasn't the quickest thing on the road but it could still drive at highway speeds. You don't need 300 HP to drive at 60 mph.

Go to the Calgary Drag Racing site and click on the tech tips button. Read the section on horsepower and torque to understand why they affect different cars differently.

 

ok, I am by no means a turbo expert, but I did used to own a talon turbo, so I know the workings on my old car. Most forced induction cars are made to produce no boost at less than about 1/4 throttle. . this is either controled by the wastegate. . or the fact thay the engine really isn't pushing enough gas through the turbo to get it to spool anymore than just enough to compensate for what the motor would like to take in. Another misconception with turbos is that the boost level is proportional to RPM, this is completely WRONG. . well not completely, but for the most part. Boost is more proportional to throttle pressure. U can run a turbo car to 9000, 10000 hell even 500000 (I know, alittle unrealistic) rpms, but if you are only doing it at say 8th throttle, you aren't going to make any boost.

Now run that same motor at 4000 RPMs full throttle and the turbo will spool it's little heart out, because more air is passing through the turbo. When I had my talon I never downshifted to pass on the highway, even up hillls unless I was racing, because all I had to do was open the throttle up all the way and I was making my 16 pounds of boost at 3500 RPMs, plenty of power to move that car. Now another thing you need to take into consideration when talkin about how fast or when a turbo spools is how big it is in comparison to the motor. My talon had a decent size turbo (capabe of 22lbs.) and yet it spooled rather quickly, usualy just around 2000 was when the boost started to REALLY build and throw you back in yer seat. But now if you were to throw a turbo from let's say Ford's 7 liter diesel on a 2.0 liter, you are going to get soooo much turbo lag I would doubt the thing would spool at all, but it would be capable of more boost at peak operation.

Maybe I am rambling on about things that no one cares about, but there really is alot more to turbocharging than meets the eye, just like any forced induction or juice applications, many variables have to be taken into account. But to answer your original question, if you had two equal weight vehicles making about the same power, one a turbo 4 and the other a NA 8, I would say that the NA 8 would win, because at 1/4 throttle boost is minimal on a 4 banger, and most turbo motor run a much lower compresion ratio than a naturaly aspirated motor (My talon had7.6:1 comp, imagine how slow that thing was if you bogged off the line) :-). . . well anyways, hope I answer one or two of you questions rather than waste both our time.