Turbocharge in cars, question.

[Xenon14]

What's the difference between let's say a 240 hp V6 Engine (Nissan Altima) and a 240 hp Turbocharged V6 (Pontiac Grand PRIX GTP)? What does the actual turbocharge do?

 

[OS]

-

 

[TomC25]

Simply, there is a device that is connected to the exhaust output of the engine that has a turbine that spool/spins up until a desired pressure level and then it releases shooting cooled compressed air into the engine.

Cooler air - better

compressed air - better (more oxygen, bigger explosion)

 

[TomC25]

oops too late OuterSquare beat me to it

 

[N8Magic]

<< A turbo is an exhaust driven turbine that pressurizes the motor's combustion chambers. >>



Exactly.

By pressurizing the combustion chambers, there is more complete combustion, and more fuel can be added, which in turn creates more power.

A turbocharger differs from a supercharger in that the supercharger is not spun up by the exhaust gases, but rather it is directly attached to the engine via a belt.

 

[MajesticMoose]

which is preferable, 240HP or 240 turbocharged HP?

m00se

 

[Xenon14]

So is a 240 hp turbocharged engine faster than a regular 240hp engine....or is the turbocharge part of the 240hp?

 

[vi edit]

Actually, the Gran Prix GTP is supercharged.

*Generally* speaking, superchargers offer a boost to low end power and a fairly broad power curve that eventually tapers off.

Turbochargers generally have a power band, or sweet spot, that they work most effectively in. These power bands tend to be higher up the RPM curve. One exception is the Audi/VW 1.8t engine.

 

[Evadman]

240 HP without turbocharging. But there are arguments fr both cases.

240HP without turbo means the engine is probably larger, or better designed. Also, it would be possable for that engine to possably make more HP if/when it is upgraded.

240 with supercharger, you have to wait for the Turbo to "spool up" The turbo does not put out any power at idle, because the impeller ( the fan that pushses in the air into the engine ) has to get up to speed before the power comes on. On the other side, the turbo will probably last longer, but you have to be sure to change that oil right at 3000 miles. Turbos eat oil for breakfast You may be able to modify the "waste gate" to get more boost. The waste gate lets excess air out of the forced induction process. Your waste gate is probably set around 6 psi. Crank that baby up to 30

<edit>
The 240 turbo includes the power generated by the turbo in that figure.

 

[BigSmooth]

Turbocharged engines can have something called "turbo lag". Since the turbo has to "spool up" or pressurize, this can cause a very brief "lag" between when you step on the accelerator and when the turbo's power will kick in.

If you are not used to this, it can be a little unsettling at first depending on how much lag there is. Most people would probably prefer a naturally-aspirated engine to a turbo if they had the exact same hp and torque.

 

[vi edit]

<< which is preferable, 240HP or 240 turbocharged HP? >>



Depends on the owner. Just about any car with a turbo/supercharger already bolted on from the factory offers an incredibly higher possibility of aftermarket tuning at a fairly inexepensive price and are moderately easy to install. Turbo/supercharged cars also do better than naturally aspirated cars at high elevations because they are more efficient in the thin air.

Downfalls are that they are expensive to repair, and are one extra part to break.

As for which is faster, well, that completely depends on many other factors. 240HP is 240HP. You need to look at torque numbers, transmission type, car weights, gearing, driver competence, ect.

 

[N8Magic]

<< So is a 240 hp turbocharged engine faster than a regular 240hp engine....or is the turbocharge part of the 240hp? >>



It depends on the engine.

If you were to take say a 240hp Altima V6 engine, a 240hp SR20DET (4 cyl turbo) Nissan engine, and a 240hp (4 cyl, redline at 9000+ rpm) Honda S2000 engine and drop them in to the same exact car, they all would perform differently in spite of their identical horsepower ratings.

The car with the Altima engine would have tons of oomph off the line, but would lack power in the high end. The turbo Nissan car would be relatively slow off line in comparision, but when the turbo kicks in at about 3000rpm, look out! The car with the S2000 engine would also be relatively slow off of the line, but once the VTEC kicks in around 6000 rpm, it also would become a screamer.

In short, the car with the big V6 would win a short race, but the turbo and higher revving cars would win a longer race.

 

[b0mbrman]

<< What's the difference between let's say a 240 hp V6 Engine (Nissan Altima) and a 240 hp Turbocharged V6 (Pontiac Grand PRIX GTP)? What does the actual turbocharge do? >>


That's not a supercharger?

 

[vi edit]

No the GTP is supercharged, not turbocharged. Two very different "means" with the same "ends".

 

[flot]

Ok, my $0.02:

Super or turbo charging basically accomplish the same goal. The -charger feeds compressed air into the intake of the engine. A stock -charged car may run anywhere between 4 and 14 psi of boost.

Superchargers are typically belt driven, just like any other accessory on the front of the engine. Bascially think of it as a "fan" that blows air into the engine at high pressure. In reality, it's not a fan - usually a screw or other type of compressor. It is not "easy" to generate hundreds of cubic feet of air at high pressures. Ever tried to blow up a balloon with a fan? Not happening. The big advntage of supercharging instead of turbocharging is that there is "no lag" - as long as the engine is spinning, it is turning the supercharger at the same rate. The faster the engine spins, the more air the supercharger pumps in.

Turbochargers are funky devices that attach to both the intake AND the exhaust. Think of them as a double-bladed fan. One fan sits in the exhaust pipe, the other in the intake. When your engine spits out exhaust, it spins that fan, which in turn causes the intake fan to spin as well. So the more exhaust, the more pressure it can build up at the intake side. This is why you get "Turbo lag" - the exhaust gasses have to have enough velocity to get the turbocharger spinning. Turbo turbines (they literally are fans) spin at very very high (50,000?) rpms - which is what allows them to generate pressure. As the exhaust fan spins faster, it make the intake fan spin faster - generating more boost and more power.

Both processes generate HOT air - that's physics, compressing a gas creates heat. When you hear about "intercooled" engines (usually in ref to turbos, not superchargers) that's basically an air-air heat exhanger (radiator) which allows the heated air to cool down before entering the engine. Usually superchargers are bolted right to the top of the engine, so no room to put an intercooler in.

The downside with either is that you've added complexity to the engine, so more things to break etc. Also your fuel management / engine computer systems get a little more complex to deal with the implications of adding all that extra air. (which means you add extra fuel, which means your little engine acts like a bigger one). It is usually easier to modify turbo or supercharged engines, because they'll have a stock "boost" level (say, 10psi) at which the system starts dumping off excess pressure. If (through some aftermarket gizmo) you raise your boost from 10 psi to 14psi, you could quite realistically see a 20-30% increase in horsepower. That's very difficult to achieve in a non-charged (naturally aspirated) engine. On some cars that is a REALLY easy modification - $5 in parts and you're there. However, you have to make sure that the engine computer, etc, etc can handle it - the biggest drawback is that you can run out of fuel before you run out of air - so you'd have to increase the size of your fuel injectors, etc.

PS: the "upside" to turbo lag is that typically turbocharged cars will hit a certain RPM when the turbos will really "spool up" and you'll feel them come on strong. In most, this would be in the 3000-4000 rpm range - suddenly you'll get a big spike in engine output. You all watched knight rider, right? hahaha. Anyway, it's an entirely different feeling from a high power V8, etc which make so much torque down low in the RPM range. Most "quick" cars (and even some not so quick) will keep up with me from a light until the other side of the intersection - around there, the turbos kick in, and I just walk away...

 

[Howard]

<< Both processes generate HOT air - that's physics, compressing a gas creates heat. When you hear about "intercooled" engines (usually in ref to turbos, not superchargers) that's basically an air-air heat exhanger (radiator) which allows the heated air to cool down before entering the engine. >>


I'm being nitpicky here, but


<< (radiator) >>


intercooler. And, some cars use water-air intercoolers.

Generally, this is the path that air takes in a turbocharged car:

Atmosphere > air filter > air inlet hose > cold side of turbocharger > [optional] intercooler > throttle body > intake manifold > cylinders > exhaust manifold (sometimes header) > hot side of turbocharger > catalytic converter > muffler > atmosphere

 

[toph99]

personally, i'd take the N/A(naturally asipirated) 240hp over a super/turbocharged 240hp. Because when you strap a super/turbo to the 240 naturally aspirated, you have more to gain than one that already has a super/turbo. just my $0.02. also, if you're looking to see which will go faster, find out the power:weight ratio, drag coefficient and the gear ratios

 

[flot]

Yucky - I said "radiator" to try to clarify what an air/air heat exhanger was... but yes, that is the intercooler itself. I hadn't seen many water to air intercoolers?

Toph, that's a little misleading. It is MUCH easier to "upgrade" an existing turbo or supercharged car, then it is to "strap on" a turbo or supercharger to a naturally aspirated engine...

 

[toph99]

<<
Toph, that's a little misleading. It is MUCH easier to "upgrade" an existing turbo or supercharged car, then it is to "strap on" a turbo or supercharger to a naturally aspirated engine... >>



true, but i didn't say anything about how easy it was it's more difficult of course, but you will get more performance out of it(usually)

 

[Howard]

<< I hadn't seen many water to air intercoolers? >>


While it doesn't count, quite a few sports cars have air-to-air intercoolers with water sprayers. Off the top of my head, the Jaguar XKR uses a intercooler submerged in coolant. Of course, you'll need a small heat exchanger for the intercooler, but it allows placement of the intercooler where air usually never reaches.

 

[4824guy]

on the supercharged Grand Prix GTP engine, it is very easy to change the pully on the supercharger unit and get a nice increase in HP. The Eaton made supercharger unit is not used to its full rating when installed on these cars.

 

[db]

Simplistically, boosting the pressure is like increasing the displacement, with the advantage that when you are *not* using the turbo, you are getting the better gas milage of your "smaller" engine.

You definately want an inter-cooled turbo.

Aftermarket items can reduce or eliminate lag, etc.

 

[LoTecha]

<<
It depends on the engine.

If you were to take say a 240hp Altima V6 engine, a 240hp SR20DET (4 cyl turbo) Nissan engine, and a 240hp (4 cyl, redline at 9000+ rpm) Honda S2000 engine and drop them in to the same exact car, they all would perform differently in spite of their identical horsepower ratings.

The car with the Altima engine would have tons of oomph off the line, but would lack power in the high end. The turbo Nissan car would be relatively slow off line in comparision, but when the turbo kicks in at about 3000rpm, look out! The car with the S2000 engine would also be relatively slow off of the line, but once the VTEC kicks in around 6000 rpm, it also would become a screamer.

In short, the car with the big V6 would win a short race, but the turbo and higher revving cars would win a longer race. >>



Close, but not exactly. The car that probably (this is all theoretical anyway) would come out on top would be the Altima engine with it's 3.5L V6.

You see, hp is usually a statement of high-end power (respective to the car's redline), which means that 3 engines which all make 240hp all have roughly the same high-end power. The difference will lie in the low/midrange, and the Altima's engine rules the roost here. The S2000 engine is all about the rev's. It only makes 153 lb/ft torque, but has 240hp, which means it makes its power at the high-end of the rpm's. The Altima's engine has 240hp, but dyno's have shown it's torque output to be around 260 (at the fly, not wheels, 15% loss drivetrain) which means that it makes the meat of its power in the low/midrange. Remember, this engine is almost identical to the one found in the Pathfinder. Does this mean that its high-end lacks? Compared to its midrange and low-end, yes, but compared to the S2000 engine, no. It still makes the same amount of hp as the S2000 engine, so relative to that, its high-end is fine.

This post is getting long, but moral of the story is that if you have a 3.5L engine making 240hp and a 2.0L engine making 240hp, the 3.5L engine is faster from start to finish. It's not that the 2.0L engine has incredible high-end. Compared with the 3.5L engine, it simply has horrible low/midrange. Hope this helps

 

[KokomoGST]

<< Actually, the Gran Prix GTP is supercharged.
*Generally* speaking, superchargers offer a boost to low end power and a fairly broad power curve that eventually tapers off.
Turbochargers generally have a power band, or sweet spot, that they work most effectively in. These power bands tend to be higher up the RPM curve. One exception is the Audi/VW 1.8t engine. >>

Hmm, a lot of "I think" guessing going on here... unofficial DSM boy for ATOT ringing in again... other people have done a good job describing what a turbocharger is so I'm not doing it again.

to answer the original question it really does depend on the design of both engines. Like the analogy of VTEC rev happy NA engines... you can indeed make all of your hp in the upper ranges of your tach. Same goes for turbocharged engines... if you have a larger turbo, it may take you more time to spool up (spin the compressor wheel) your turbo and hit your maximum boost pressure. Of course, you are throwing more air into the engine even as you spool up that large turbo so the power delivery may seem more linear. If you go with a smaller turbo, it will spool much quicker and you'll get a massive shot of instant torque and power down low... but that doesn't neccessarily mean it will run out of juice when it reaches high rpm. Again it's dependent on the flow characteristics of your turbo system... some people clip (or cut off metal from) their turbo compressor wheels (the side that feeds your intake). Seems kind of retarded to do so since you have less fan surface to push air, but what this does is allow you to flow more air on the top end of the rpm range since your compressor blades aren't impeding the flow as much.

My car has a tiny turbo and gives a massive shot of torque down low... pretty much all hell breaks lose when my turbo hits but it's not able to hold that boost up high so it gives up at the upper ranges. (It also means I'll have traction problems and usually spin my wheels before redline) Other turbo cars may have a similar feeling if they spool quickly (VW/Audi 1.8Ts). Also, Mitsubishi has a fairly strange approach to the turbocharged engine, they've been gradually increasing the compression ratio to near NA car levels. I run 8.5:1, the new Evo runs even more at 9+:1. What this means is more low torque off boost which makes the car quite drivable off boost with good low range. Another thing to note is how quickly your engine revs and how far it revs. If you take your little time to rev to a 6000RPM redline while I'm flying toward my 8K redline... does it really matter that I don't make power from 1-3K? Probably not.
The nice thing about turbocharged cars is that their power curves are quite a bit easier to mess with than their NA counterparts since they usually require a lot more internal engine design work to achieve similar curve change. DYK turbos take advantage of the wasted energy from standard combustion?

Bottom line: this just bench racing... drive the car and race it if you really wanna know
EDIT: spelling

 

[Triumph]

Another benefit of turbocharged engines is weight. Since you don't need a big displacement engine to make power, the car won't be as heavy, it won't understeer as much, and it'll typically get better fuel economy, if you stay out of boost. Of course this is with all other things being equal. But weight is the enemy of performance in almost any sport car.