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LOL! If I had that, I wouldn't need an engine.

What's wrong with old school? The car in your sig is old school.


Let me get specific on this (*sigh* again.....) since it's a sticky made for people to learn the correct things. All turbochargers are actually superchargers, but not all superchargers are turbochargers. One of the basic phrases when you learn about these types of forced induction.


Ever noticed how the 3-4 second dragsters, the ones spewing the flames of hell, use superchargers that require about 800hp to be spun?


Turbos have had to evolve so much during the years it's been around. Back when they were first introduced, they didn't even have wastegates invented (the idea wasn't even thought up). Turbos were so heavy and so hard to spool, that there was barely any risk of them overspooling while travelling around. Wastegates came later on. Years came and went, and turbos still fell short to the way of superchargers. Lag was a problem, and so was using them in big powered applications. It was hard to tune them without the tuning technology we have today. A car fell off boost, and the whole timing and fuel map had to be changed to compensate, and there wasn't the technology to do that back in the 80's, at least, not sold to the open public.


Now, even variable geometry turbos are coming up. Don't know if they are in production right now, but Porsche was going to be the first company to do it on production cars.


"Keeping up with the times" would actually mean that people should start adopting the twin charge technology being produced right now. Turbos have been around since the 50's or something (don't quote me on that), and SC's since even before. So even with the evolution the turbocharging world has undergone, and the not-so-much-evolution that superchargers have gone through, individually, they are both old technology and still have their pros and cons individually. But combined? The only actual con that can be justifyingly conceived is the weight.

Inygknok is absolutely right.

Both have been around the automobile for as long as they were put to use. Technology applied to any type of automobile have evolved tremendously. Since car manufactures always wanted their customers to feel the power of the car, they often produce a cheap engine strapped with either turbocharger or supercharger. If you know what I mean, then those monstrous valves on top of an American muscle are protruding just to have both basic ram-air induction and have space to place the supercharger beneath the carburetor.

Even to this day, both methods of forced induction are applied to buses and freight trucks. Yet, I guess that answers that "pssssssshhhhhh" sound I hear when they halt.

As said over and over again, supercharger provides excellent low RPM torque boost;turbos at a higher range. Nevertheless, the torque and highest bhp range for best performance is rarely reached which results on a gasoline car is very small.

Finally, whenever applying either forced induction upon your vehicle, beware of its price, affect on the car, durability, and noise.

the "Psshhh" when the trucks/bus stop are actually the brakes. Though they do use turbos.

Superchargers provide a predictable power curve since it's belt driven, while the turbos have the lag since it works on exhaust gases. But Turbos typically create much more power up top.

True. Some cars can't handle boost unless you build the bottom end properly, and of course, a good engine management, tune, fuel accessories, etc are a necessity.

They way I've always thought of it, was superchargers are great for bigger engines since they take up a bit of power to use, and great on low rpm engines that produce more power at the bottom end compared to the top, since it makes instant boost. A turbo works better on higher revving engines that has the powerband in the upper range. Sequential Twin turbos help with the lag and low boost potential (the point at which the turbo makes boost) by having a small turbo spooling in the low range, then slowly shifting to the bigger turbo as the rpms increase (like in the rx-7) and 2 small turbos would be good for an engine that needed big boost at a lower range or something like that. Either way, they've both been around for a wicked amount of time, and were used in planes for the longest time (I belive germany first started supercharging their planes in WWI or WWII)
You can use both supercharger AND turbocharger, but that's a bit much....

I think it really just depends on the engine you want to put the force induction on. If you have an engine that redlines at 5k but makes good torque at the low range, why would you turbo it, since a turbo loves rpms? Same with having an engine that redlines at 7-8rpm it might be more benificial to turbo instead of super. I've always been a fan of turbocharging though.

I'm pretty sure buses use air brakes, hence the PSH when they stop.

Yes, they use air brakes and so do trucks. You don't even need to have had the experience of working on a bigger truck to notice. Just drive behind one and you'll notice the mechanisms near their calipers at the back. Just follow the rear axle and you'll notice them.


Kazuki: Read every single post I have written since page 8. That should clarify the doubts I noticed in your post. If you don't get it, just say it, and I'll write a few more paragraphs as usual.....

This post has been edited by Inygknok on Aug 10 2007, 12:02 AM

Trucks use pneumatic brakes as stated but from what I have seen the shift action is also pneumatic and that is understandable if you have seen their gearbox taken apart.
So in theory you can say they are partly supercharged in that way as they DO use a compressor but not to force air into the engine, although I have yet to see a supercharged "heavy vehicle" (Truck or bus).

My mechanic education does not extend towards "heavy vehicles" but I have seen a bit of them so I know a bit here and there.

i use a truck turbo on my 240 yay... i would comment but its been all said... keep it going guys

honestly speaking... i would choose an antilaged monster-turbo with the turbine as big as my thigh...

but, reasonably, i would choose a turbo, because you can achieve higher torque values with the turbo, you just need antilag so that you don't get left back at the starting line(low compression), and you need a trained right foot(which you would have, learning to drive a car...

btw... i just saw this, and i was wondering why noone bothered to correct him...?
https://idforums.net/index.php?showtopic=33660
anti-lag is NOT sparkplug detonation, or related to adding of any heat... and neither is it squirting fuel into the exhaust manifold... it's just allowing o2 to pass into exhaust (via bypass valve)manifold, and react with the unburnt fuel in the exhaust manifold, the exhuast gases are plenty hot enough and there is already enough fuel in the exhaust vapor(engines are very inefficient), that guy offered a wikipedia article that HE DIDN'T EVEN BOTHER TO READ!!

This post has been edited by atlantian on Mar 21 2008, 08:32 AM

so to clarify stuff there is 4 way or making high horsepower

first is na
yes you can make high power from a na engine but you need to run really high compression ratio good fuel that will be able to work in that compression ration and bulletproof engine.I mean that you need to be either a racing team with a big budget or a engeniirer that have alot of money because high compression ratio put alot of stress to the engine

second is turbocharging
I think everybody know that you can make alot of horsepower with turbo charging.juste have to put a big turbo and you are ready.But you face a big problem called LAG.There is a few way to compansate it or eliminate it.You have twin turbocharging which mean you put either a small and a big turbo and a switch or a valve to direct air to one or another of the turbo depending of the rpm, or two medium sized turbo which will give the same amount of horsepower as a single turbo.But you now have less or no more lag.Another way to eliminate lag is a anti lag system also called a misfiring system that include a valve on the intake side that will direct a part of the air to the exhaust while you are braking or letting of the gas to dont lose the rpm of the turbocompressor itself and which will mean elimanating lag.Another way is running more pressure into the turbo while having a smaller turbo which will give yo the same power and less lag but like the high compression na engine,it will put alot a pressure to the engine components.So just for racing team.

third way is supercharging
you can also make power from a supercharger.Because the supercharger is driven by the crankshaft ,it has no lag so it ill corner like a na engine but with more power and torque.But like already before me ,a supercharger will add parasitic weight to the engine so it ill make less net power.People tried to lighten this parasitic weight by having the smae type of compressor as the turbo so it lighter than the normal root type supercharger.But when the engine get into the high rpm range,the supercharger will start to make less power than a turbo.You can swap the pulley of the supercharger to a bigger one but it ill lead to a lost in power and torque in the low end range.

Fourth way which is starting to be popular is twin charging
which mean you put a supercharger for low end power and torque and a turbo for high end power and torque but like the vtec system there will be that little range of rpm where there is a drop of power.but when the system is well built there should be no problem about that because ppl making the system will have put the changing point to somewhere you dont stick for too long in the rpm range.

New techonlogy in turbochargers make lag disappear unless your running crazy amount of boost.

this is called ball bearing turbo charger(dont take it bad)

Yeah the ball bearing turbos are crazy, so responsive and it provides good power.

[rantmode]Turbocharging has advantages over natural aspiration as well as roots, twin-screw, or centrifugal supercharging. Thing is... We tend not to quite use it all.

Now then... We all know that the traditional boost build involves dropping compression and running tons of boost, right? And we all know that big compression is BAD in a turbo mill, right?

Notsomuch. A bit of compression on a boosted mill isn't a bad thing per se. 10.5:1-11:1 can be had and made streetable easily enough in an NA mill, and by extension a turbo or supercharged motor. It's called staying off too much of crack, er, boost. Higher compression mills do more with the same amount of air/fuel going in to them, and therefore when off-boost make more power. The result? More power before the boost hits, and less time before it does, even with the same size turbo. Add in that you no longer need as giant of a turbo to meet a given power goal because you don't need as much boost, and all that nonsense about lag starts going buh-bye, especially when you run a twin turbo setup.

BLASPHEMY! It goes against everything known about turbo motors, doesn't it!

When cruising around town, it'll be more efficient than the general turbo mill by needing a good bit less throttle and RPM to get around reasonably, and when you hit it... You get the same power as a traditional boosted mill with less lag, a smaller turbo, and smoother delivery.

Someone point out holes in this, please. It's going on 4:30 AM here and I am tired as hell. I'd type a bit more but... It can wait until morning. Which is going to be more like noon or later...

While you can run higher compression ratios, and gain more low end torque and off boost power, you cannot run as much boost (which you stated), but some turbos have an efficiency at higher boosts. Thus, you gain more power. So in the long run, for a street-able car higher boost is of course better with less boost, but for an all out, race engine/car lower compression and a larger turbo.

Or you could just use a turbo that's more efficient at the lower boost levels...

Or run just slightly less boost. Of course, higher compression makes more of the boost you throw at it so...

Win.

But that isn't the question here. If you were to get max power out of a turbo'd car, how would you do so without another power adder? You'd lower the compression, turn up the boost and run Q16 octane.

"Or you could just use a turbo that's more efficient at the lower boost levels..."

You want a turbo that is efficient in low boost levels? Go get a disco potatoe or a T too small. And with these small turbos which spool up insanely fast, there isn't really a reason to run super high compression because, they already have torque.

So no, you don't win. If you are aiming for 250-350hp then yes normal or "high compression" is good.

Face, meet palm, palm, meet face.

If I wanted max power out of a turbo car, I'd wind up running high compression along with a camshaft that to any engine builder you ask is completely ass-backwards and a good bit of boost. Of course, the cam timing required to go REALLY stupid is unobtanium without a billet cam simply because the blanks already have a bit of a profile ground into them and said timing is out of that profile.

And by "high compression" I mean in the realm of 10-12:1.

You want my reason for high compression with those little turbos? Power. Zero lag. They spool quick, yes, and with high compression, you make more use of what boost they do build. Aaaand thereby more power. I don't see how this is so freakin' hard to understand...

Lowering the compression ratio allows you to increase the boost. Lowering compression lowers combustion pressure, prevents pinging, detonation, knocking, etc. What is so hard to understand, I guess I must be talking to the wrong engine builders...


As I understand it, the issue is not whether high or low compression creates more power, but whether the engine can handle it. High compression will cause the more reactive molecules in your gasoline (so the smaller molecules in the case of gas made of non-polar hydrocarbons) to oxidize just from pressure alone. The pressure pushes the molecules tighter and tighter together and thus the chances of two molecules hitting eachother with enough energy and the right orientation is increased greatly with pressure alone. This means that during the compression stroke, the greater the number of smaller molecules in the gas, the more likely two will hit with enough energy and explode. If this happens before the spark, you get knock, which is the sound you get when the explosion is early and pushes the piston down with a lot of force while it's still trying to go upwards. Eventually something has to give, and the something tends to be pistons or the walls of the combustion chamber.

Now since more power comes from a bigger explosion, you need more air and fuel in the combustion chamber and this causes increased pressure. So a few things you can do to keep power but not destroy your engine is to reduce the pressure, reduce the heat or make the fuel mixture more tolerant to higher pressure/temperature. This in where low compression comes in. It allows you to create more power without changing your fuel because you can cram more stuff into the combustion chamber since the chamber is larger. The reason to do this is we're limited to what type of fuel we can get at the gas station so road-going cars running high-boost compensate for the increased heat and pressure of the air going into the engine with lower compression. It's a trade off since a high boost engine with high compression would cause the most powerful explosions, but race gas (a high octane fuel) is not exactly cheap.

I don't understand why its so hard for you to understand.

This post has been edited by Xcert on Jul 15 2008, 05:51 PM

And that's where the cam timing that most find absolutely ass backwards comes in...

It still comes down to what compression you are running. You can advance the timing all you want (or retard it) but you are still limited by the static compression ration which occurs within the combustion chamber. When you advance the timing, you are subjecting combustion to occur earlier than optimal and you can run into knock/detonation. When you advance the timing, you make more top end power, and more power overall but there is still a limitation set.

I don't understand why you are arguing a useless case.

Rotary Junkie, there's a little thing that you're forgetting. It's called REALISM. Obviously you have no idea how difficult and costly it is to get the kind of package you're looking for... a boosted and high-compression motor that runs reliably. Something like that from the factory (rare enough as it is) is going to be on a relatively pricey car, and to make something like that in the aftermarket arena is still going to be pricey.

Obvious and vague.

"Easily?" Let us know when you build something like this, along with how "easy" it was and how much it cost. Very few motors meet this criteria stock (as only VW's turbocharged 2.0-liter I-4 and BMW's twin-turbo 3.0-liter I-6 come to mind, though the VW's unit is much more biased toward practicality while the BMW's unit isn't a cheap option), and to put together such an engine with aftermarket components isn't as easy as bolting parts on--and if it is, trust it's going to be expensive. There's a reason why back in the day, most Integra Type-R owners usually avoided forced induction of any sort, and, more recently, why RSX Type-S owners either stuck with an NA setup with every bolt-on imaginable or ponied up the money for a decent turbo kit, sometimes even having to swap out pistons to get a lower compression ratio to avoid detonation, unless they had the resources to put their car through weeks of tuning.

Obvious and vague once again. As I stated before, this ideal setup is difficult to do without the proper resources, which most people don't have. This is highly unrealistic. And unless your power goals are well within the reach of a streetable setup relative to the engine's size (i.e., 200 hp for the VW 2.0-liter I-4 or 300 hp for the BMW 3.0-liter I-6), then you will most definitely have some sort of lag, even if it's a factory setup (i.e., 286 hp for the Mitsubishi 2.0-liter I-4). Take your pick, a linear, relatively lag-free power delivery with a modest top end, or a slower to boost but most exciting adrenaline rush from the mid-range all the way up top. You can't have both, unless you're bringing a few suitcases of cash.

You mean a smaller turbo with a restrained maximum power output? Or a more advanced turbo (like a unit with Variable Turbine Geometry) that is found on very expensive and found on cars like the $130k Porsche 911 Turbo?

Again, increasing the compression ratio of an already boosted motor to above 10.0:1 or boosting an NA motor with a higher compression ratio than normal isn't easy. Have fun tuning it.

We understand the concept just fine, but what you don't understand is the huge challenge of doing something like this. I'd put money on you not being able to accomplish this with a certain amount for a brand new car, mods and tuning, with your goals (higher than a 10.0:1 compression ratio, streetable power delivery practical for daily driving) while being able to outperform a factory force-fed car of the same price as what was invested in the car and modding (otherwise what's the point of all the hassle?). And let's not forget how this dream setup will almost certainly not be smog legal, seeing how high-strung the motor is running at any given time.

I hate resorting to pointing out people's ages, but it's funny how the 14 year-old is trying to school people on a topic like this.

Yeah, yeah...

Ever hear of a Miller cycle engine?

Bingo. Bleeds off some pressure by leaving the intake valve open after BDC.

You wind up with less of a charge in the cylinder, but because you compress it more, you get the same or greater reaction.

Lastly, I'm not trying to "school" anyone. Just bringing up a different way of looking at things.

Great. Set up a car like that.