I guess you should never put a SC on a GEO Metro......not enough power to spin it..LOL..........seems pretty high when AC units take about 15 -20 HP.

 

The turbo doesn't use normally wasted power, it actually adds a load to the engine that isn't there in n/a form. The piston is always pushing exhaust out of the cylinder, but it isn't pushing it against an impellor until you put a turbo in the equation. In n/a form the piston is pushing only against the resistance in the exhaust system, nominally 2-3 psi of backpressure. If you are forcing 12 psi of boost into the intake, you are putting at least that amount against the piston which is a force that isn't there in n/a form. The energy to push the piston up against the force imparted by the turbo must come from somewhere. Where?

I was old enough in the 60's and 70's to remember when turbos were labeled as "more efficient" than blowers. The comparison was between turbos and roots type blowers. Where is the proof that transmitting energy through an exhaust system is more efficient than transmitting energy through a very slim and lightweight serp belt in modern centrifical blowers?
I like my D1SC but I'd trade it in in a heartbeat if it can be shown that turbos are more efficient. I worry that my serp belt will break when I least expect.

 

Phil likes to conserve words.
If you don't know him, he's a tuner with an outstanding reputation. Probably what he's saying in shorthand is something like:
"On an LSx, given my experience with installing and tuning superchargers, measured air flow versus power output indicates that about 80 horsepower is disappearing at maximum boost. From my calculations, that's what's used to drive the supercharger."

 

Do a search. I gave an example of same car, two different power adders, comparable boost. Check out this site it'll give you an idea:

Turbo (@ 8.5psi):
http://www.svspower.com/case_study_detail.aspx?id=21

S/C (@ 10psi):
http://www.svspower.com/case_study_detail.aspx?id=20

 

I looked at both and the s/c doesn't show anything of the install, like size of ducting or the like. What type of blower is a Sean Rowe? Never heard of it.

 

Turbochargers produce higher power at lower pressure ratios than superchargers as there's greater mass air flow and lower charge air temperature.

 

All right, I'll bite...

Not sure what Newton you're talking about, but I don't think it's the Isaac most of us read about in Physics class.

Thermodynamically, it is more efficient to convert exhaust energy to compressor work through a shaft floating on oil/bearings than it is to convert it through pullies and gears.

Yes, turbos take energy to run. You absolutely do not have to have equal exhaust pressure as intake pressure to maintain constant engine rpm, and with turbos you generally have around twice the exhaust pressure as intake pressure (at higher power levels, not at idle, etc). If you do the math you can figure out how much power the turbo is taking to run and if you had a SC dyno to measure how much power it is taking to turn the SC alone you'll find the turbo nets out to less loss (assuming a reasonably well matched turbo setup). Or, you can just skip the math and thermo and take Earl's real world example on his Viper...

As far as Phil quoting the 80 hp, that would be at a some power level... not all the time. If it took 80 hp all the time you wouldn't be able to start your Vette unless you had a 80+ hp starter.

In the end it still comes down to preference. They all have quite different driving characteristics and packaging constraints which most people weigh more heavily than which is the most thermodynamically efficient choice for their car. All of them help us make more power than they consume, so for the FI folks, they're still all good... no matter what any of the Newtons say...

 

Well, I'm not sure what you mean by not showing the install. SVS removed the blower and long tube headers from my car ('98 GTS) and put it on the car in the case study. It made the same power on my car. They then fabbed a twin turbo setup on my car. Its a perfect way to do a side-by-side comparison...dyno results came from the same dyno.


RE: blower, it is a Roe blower...same basic unit as the Kenne Belle. The Roe blower has made a max of 750rwhp (no NOS) in Viper applications.

 

Still a few wild cards. I doubt they were using the same charge cooler setup. How do the intercoolers used on the two setups compare? A maximum of 750 on a Viper with the twin screw suggests that with the blower, the charge cooling may not be as good, the supercharger may be undersized for the displacement of the Viper, or it may not have been sealed very well. It would be interesting to compare IATs.

 

http://forums.corvetteforum.com/show...t=supercharger

 

Are you trying to tell me that heat and the resultant thermal expansion are not wasted energy in an internal combustion engine. A large portion is used in the power stroke, but there is a tremendous amount just being wasted.

Your exhaust theory is flawed. You are thinking of the motor as a simple air pump and not considering combustion and the resultant release of energy. The volume of gases that goes into the cylinder during the intake and the volume that needs to exit during exhaust are completely different. The cylinder does not have to push all the gasses out, a large portion will move on its own to fill the lower pressure area. This movement continues throughout the exhaust system and is what allows the turbo to spin without sucking all the power out of the motor.

The bottom line is that the turbo can run the compressor with less parasitic loss than the SC. The key word being "can". If things are not located/sized correctly it becomes a bottleneck. Each turbo system has a window of efficiency that is better than the SC, but much smaller. If you balance it all just right you can create a turbo system that will make more power than the SC.

The thing that makes the decision difficult is not the power adder, but the platform it is going on. The ls1 just happens to be a motor that can make a crap load of power without a power adder and the c5 happens to be a car with some packaging constraints. The decision quickly turns to packaging, power band ... and away from efficiency. SCs can hold their own for sure.

 

OK RoadRebel, I'm sure you know the answer.
Based on airflow per output horsepower (using a stock LS1 as a baseline) what's the horsepower lost to drive a centrifugal compared to the horsepower lost to drive a turbo at, say 600 horsepower, all other things being equal?

 

This is good reading...........keep it up

 

This happens every time I do this. I am showing you two systems...systems that I owned. There are no wild cards. Same engine/same car/same system. Re: the max of 750rwhp...that is where that blower maxes out. I believe its a 2.2 or 2.4L Twin Screw. Do the math (i.e. check the CFM rating).

No one is saying that turbos are better than s/cS, just more efficient. S/C cars can run fast too (just not as cool )..kidding. Pick which one you like and go with it. No big deal. I just choose turbos (see sig.).

 

who cares?

To me all I care about is what does the rwtq curve look like and how much does it cost to get (ie install cost and maintance, not fuel cost).

the cents make a ramped tq curve, the turbos make a hill right in the center that starts a little later in the rpm band than say a roots set up, then the roots/PD blowers make a flat tq curve that starts low in the rpm band.

decide what kind of rwtq curve you want then install that type of SC application.

bottom line, any of these setups will be limited by your drive train long before you max out the power that you can make. on a smaller motor this may be more of an issue but on the LSx I just don't see that any of the SC options are bad.

IMO

More Than Zero

 

I understand that you owned both systems on the same car, and I'm not arguing that a supercharger is more efficient. Just asking if both systems used the same intercooler. Also suggesting that the horsepower gap seems bigger than one might get with an ideally sized twin screw, or with a centrifugal. A 2.4 twin screw or roots can be spun fast enough to have sufficient displacement for a 500 CI engine on paper, but spinning the heck out of it heats the charge more than a larger blower turned more slowly, and the higher the boost, the greater the leakage past the seals. There comes a point (except for interference fit single-pass blowers) where spinning them faster doesn't result in greater air density. They're maxed out.
So we might be comparing a less than ideally sized blower (I understand, it's all that's available) to a custom idealized turbo setup with (possibly) a different charge cooler configuration. These are some of the things I consider wild cards.

 

I went from an ECS D-1SC to a TTi X kit. The difference is about 100 rwhp at the same boost level. I think you'd be hard pressed to say the ECS FMIC is less efficient than any of the others on the market.

Granted I was using a 4.50 pulley with the D-1SC, but I was also running more timing with the blower than I am with the turbos.

Mark

 

No Mark we need REAL examples...your turbo car must have been tuned on a 20 degree day or the D1 must have needed oil that day...

Now if we cold only find a good example...

 

To me this suggests the turbo would be less stressful on engine at any given HP/TQ. Longer engine life perhaps ?

The Turbo sounds better ... which to me is very important factor in my purchase.

 

Which is also why blowers need larger injectors at the same power level (all the extra power it takes to spin the head-unit).

Mark