BootCamp

I was referring to the STS turbo kit - universal application. I agree about the distance between the turbo and the intake, spooling time, and lag issues you mentioned. While the location of the turbo in that kit helps with heat issues, it creates too many other problems to overcome (that you mentioned) to be what I'd consider "efficient".
I had a 1978 Mustang III with the 2.3L Turbo. I had to overcome detonation and pre-ignition issues with that system, as well as turbo-lag since this was very new technology in American passenger cars at that time and there was little documentation to troubleshoot from. The wastegate on that car was set for 7 lbs, which wasn't extreme by today's standards, but the lag was very noticible (I would guess it was around .3 - .5 seconds). The odd part is that the system was fairly compact and all of the plumbing was in the engine compartment, with the turbo sitting in the rear of the engine well near the firewall - yet the lag was so noticible. I can only imagine what the lag would have been like if the turbo was mounted by the differential.

Nitrous is pretty straightforward. As you stated, there are "bottle pressure" issues, but the efficiency of the nitrous systems inherently overcome most of the "location" problems they create.
My understanding of the Nitrous system (and it IS limited) is that the HP gain from using it is a result of the extreme drop in intake temperature - more than anything else. The bigger the jet, the more nitrous is delivered and the lower the intake temperature. Subsequently, the amout of fuel (gasoline) has to be adjusted to compensate for the engine's efficiency with the cooler combustibles being brought to the power stroke of the cycle, as well as running cooler spark plugs so as not to "lean out" the engine.
Am I on the right track here?

RLSH700

Actually from what I have been told, a Supercharger can be part time if you want it. Just drop the pulley belt when you don't want it. Turbos can hurt fuel economy on some vehicles so also take that into effect. Also superchargers tend to be easier on the engine and do less wear to the engine.

Jeremiah 29:11

A few questions:

1. If you drop the pulley, how does the air get in.

2. What are the factors that maek turbos hurt fuel economy?

3. What ways are superchargers easier on engines?

Chris

2. The turbo works by cramming more air into the engine. Without a corresponding increase in fuel injected, the air/fuel ratio goes too lean and you have detonation, which will harm engine components.

3. The supercharger is easier on the engine because they typically don't create the power a turbocharger does. That extra power tends to really tax engine components: cylinder walls, cylinder heads, crankshaft, rods, etc. It seems that OEM engine parts are built to a degree of redundancy that is acceptable for the relatively smaller power gain of superchargers, but the not the larger gain of turbochargers.

Jeremiah 29:11

1. This question was not answered?

2. Of course, Turbos and SuperChargers both do more cramming of air. The question was not answered. What are the factors that make turbos hurt fuel economy?

3. I partially agree with you on this one. On launch, Supercharger stress components more than a turbo. While modern turbos that are lighter and made with special alloys spool up faster they do not stress on launch like a supercharger. Superchargers do not spool up, they are in synch with the crankshaft and have maximum boost in the lower RPM range. I do agree that turbos provide more HP at the higher rpm range.

BootCamp

I'll take a shot at this.

1) If you turn a fan off, the acceleration of air from the fan ceases, but air still flows through it. I'd assume a supercharger is much the same in it's various incarnations.

2) As the turbo spins, it increases the air/gas pressure through compression. Therein, it's taking in more air and fuel in the same amount of time that it would if it were running naturally aspirated. Increase the air/fuel flow, you increase fuel consumption. The rate increase is not direct, but more exponential because of the change in programming to get the air/fuel mixture correct under higher pressures and at higher rpms. Additionally, when the wastegate opens (once maximum predetermined pressure is reached), the system is theoretically less efficient since more intake is being produced than the engine requires/can handle.

On a side note, *** from a friend who has been running and building dragracing cars for many years, he indicates that Superchargers tend to "oval out the cylinders" after a while. He said this happens at differing rates depending on the heads on each motor. His experience is that the cars with intake valves set closest to dead center of the cylinder/top of the piston usually hold up best because the pressure from the SC is not coming into the cylinder from such an angle to the top of the piston, reducing the side pressure and not pushing the pistons away from the motor's center. He said this tends to collapse the rings or force them into the cylinder walls, causing more wear, friction and heat. The three combined shorten the life of the block.
***This friend has been drag racing since the 60's against the best local talent (over all of these years) in sanctioned and "other" events. He still build cars - he's currently working on a 38 Chevy which dyno'ed 980HP - and raced against Shirley Muldowney when she lived and raced in this area.

Overpowered

Still no answer on dropping a drive belt for a super charger.

If there is a drive belt on a supercharger than it is probably a blower of some sort.

If a blower stops spinning, so does the airflow thru it. No air/airflow, then combustion will be super rich/non-existent.

I know Mad Max turns his off, but thats a movie & not real life.

I have not heard of anyone devising a blower bypass to get naturally aspirated air into an internal combustion engine. Help me out here??

A turbo can have its wastegate lowwered to such a low release pressure that it can effectively be turned off, but why bother having it then?

Eric

Jeremiah 29:11

1. Thanks that is the correct answer.......there is no air flow thus you cannot just drop a belt.

I had heard of several companies years ago that had an electric clutch and at the flip of a switch could free spool teh supercharger and at the same time open up an inlet for free breatching but I have not heard anybody doing that these days I think because of reliablity problems. If anybody is doing that anymore please let me know.


2. Superchargers are always physically connected to the crank thus they have parasitic drag and therefore hurt fuel economy. Turbos can actually increase fuel economy during normal driving. What you have to watch out for is the incredible eat generated from the Turbos due to the exhaust gases. With a good design Turbos are better for fuel economy during normal driving.

3. Turbos are easier on powertrains than superchargers because they bring on power easier. Turbos usually do not have boost at 2K RPM while a supercharger can have boost as low as 1.5K RPM.

BootCamp

All correct.
BTW - Because the old style superchargers were "roots" types, they did have electric clutches available as you referred to. The new superchargers (being used on most street applications, such as F1's and Paxtons) operate differently and can't be disengaged with an electric clutch.

Chris

I don't understand... did you know the answer in the first place and were just testing everyone or asking an actual question?