SteveM928

And you really believe that Tony?

Yes, that would be the one that's been doing well with the centrifugal supercharger on.

mspiegle

So in order to argue for CS units, you will use racing examples (which have plenty of variables), but when you're arguing against positive displacement, you're telling us we can't use racing examples?

SteveM928

I just posted that to add to the information on the car that Hacker-Pschorr first mentioned in his response to John's statement:

Thanks for confirming that centrifugals do have merit John, since it looks they are starting to appear on race cars. I do still say that trying to make direct performance comparisons of the different systems available now by using ANY form of racing results is pretty worthless.

GoRideSno

SteveM928,
Love your sig.

Andy K

SteveM928

Thanks Andy. I have to admit that I "borrowed" it after seeing it in another discussion board, but how could I NOT use it.

Old & New

The top chart is courtesy of Tim Murphy, an 8psi CS, and the bottom one is the Bastard as posted above. I equalized the x and y scales on the two charts; now they can be compared directly. I also plotted turbo data points onto the CS chart. Red dots are turbo torque data points, green dots are turbo horsepower data points.

What happens to the turbo over 5K rpm??? The CS is pushing over 100 more horse at 5500 rpm, and 150 more by 6000! I expect that there would be better breathing in the four valve motor, but I understand that an exhaust restriction can also cause this type of problem...

Tony

Come on man!! A good eveing of in a bar solves all the worlds problems, including Centrifugal vs Turbo vs Whipple.

Yeah, I suppose it can create a few other problems as well, but that's what the next bar down the street is for!

bcdavis

I still think that the best comparison will be when goridesno and the murph guys get some k-jet kits installed on early 4.5 liter US cars. Then we can directly compare 8 pounds of boost on each setup, with the same engines.

Jim bailey - 928 International

John what I was referring to is that you calculate HP as equal to torque x RPM divided by 5252 So the hp curve and torque curves intersect at 5252 rpm where the 5252 rpm cancels the 5252 denominator and HP = torque . Inertial roller dynos do NOT measure torque they measure work over time which is horsepower then calculate the "appropriate" torque numbers . The overlay of the two boost levels just really looks odd and I have no doubt that each is accurate with the exception of the RPM .

Old & New

Jim,

Maybe because the horsepower and torque are on different scales... when I plotted them onto Tim's chart (that has the same scale for tq. & hp), they crossed much closer to 5252.

John.

Yes congratulations guys, you have figured out there are factory cars with superchargers, but each and every one of them is positive displacement. It is a fact you guys just don't seem to understand that there in not one OEM using a CS setup even though it is an easy (make that easiest) swap.

HP and torque are two different things altogether. The 5252 is a conversion factor that comes from taking 550/(2pi/60), those are the conversion factors when using RPM and ft-lbf. It is just a conversion factor to break the units out. If you plot them on the same scale then I suppose there is some magic as to where they cross but I see them as two different things, I can have 1000 ft-lbs at 1 RPM, but that is not any amount of power to do anything with.

Yes great, compare a boosted base 316 HP 5.0 liter NA motor with a boosted 4.5 liter base 219 HP motor. That makes a lot of sense? The torque curve on my 4.5 has the same shape as does the stock torque curve. It is the way the 4.5s are cammed as well as the heads.

John.

Yes hacker whatever....that lag you refer to is followed by instant boost to the wastegate setting, while you wait to redline to make full boost with the centrifugal blower. I would argue the blower itself is far more complex than the turbocharger and will have longevity issues. For a bolt on in a weekend package, I can't disagree with your statements, but good things come to those who wait.

Call it chest beating, call it whatever you want, the fact remains the turbo and positive displacement blower are the chioces of OEMs and the more serious tuners out there. Show me an OEM setup with a CS? Why can't any of you provide this information? Show me a LeMans winner with a CS.

Talk to all of the experts out there and you will hear the same information.

Old & New

John.,

No pissing match, really. I'm just on a fact-finding mission here.

Understood about camming being responsible for the sharp dropoff at such a relatively low rpm. I'm interested in that the low-rpm slopes of the two charts are very similar... it seems to indicate that the engine response ("real world drivability") of turbo vs. CS are similar, regardless of the pressure-rpm charts previously cited.

My gut feeling is that positive displacement may have an edge... can someone plot their "Andy" curves on the chart above?

SteveM928

"Lag followed by instant" Kind of an oxymoron isn't it? It does seem to be generally accurate for turbos though. Floor gas pedal, change radio station, think about what to have for dinner, change radio station again, boost!! I remember the first time I ever drove a turbo car. Scared me to death because I thought I broke the guy 's car when I floored the gas pedal and nothing happened.

www.vortechsuperchargers.com/news/model_u.html

http://www.ford.com/en/innovation/en...Combustion.htm

The Ford Escape hybrid SUV is scheduled to be available this Summer.
www.fordvehicles.com/escapehybrid/frameset.asp

First that race car with a centrifugal that was mentioned already now this, eh John?

Speaking of racing, look at what Ford's racing parts divison sells:
http://www.fordracingparts.com/parts...tKeyField=1866

BC

I can't wait myself!