Comparison between a supercharger and a turbocharger at the same boost level

[Sellout]

Originally Posted by buditjoenawan

I missed that. Has Vortech confirmed that map does indeed correspond to the shipping unit?

budi

Yeah they have, couple posts after that one. This link actually takes you to that post in the thread instead of a single post view: http://www.ft86club.com/forums/showt...660#post876660

I bet that if you pair the hotside of the larger turbo with the cold side of the smaller turbo, you'd see the gains - at the same boost level.

In the example I gave, the smaller turbo's compressor is physically incapable of flowing the additional 100hp. At any boost level.
I gained 100 HP through a combination of lower backpressure AND better compressor efficiency

Also, someone else mentioned that if you make the turbos the same, then of course they'll do the same amount of work... Your comparison only works if you have a turbo that has the vortech compressor wheel in it, and you compare it to a vortech supercharger on the same dyno/same conditions. Then you would see the difference between them, but we don't need to. We can already see that turbos are making more power at even lower boost levels.

[carbonBLUE]

Originally Posted by Sellout

In the example I gave, the smaller turbo's compressor is physically incapable of flowing the additional 100hp. At any boost level.
I gained 100 HP through a combination of lower backpressure AND better compressor efficiency

essentially a turbo has limit which it can flow air, not in pressure but in velocity. i think this is called "head loss" correct me if im wrong. It is where a fluid such as air becomes condensed and its surface area (the amount of air molecules that come in contact with the pipe) increases along the inside of the tube. This causes friction and slows the air down an heats it aswell causing a drop in pressure, thats why turbos have max pressures!

[Scoobyrs25]

Originally Posted by Sellout

We can already see that turbos are making more power at even lower boost levels.

Ok, so what everyone is forgetting is the boost curve. The superchargers make peak boost at redline. A properly tuned Subaru motor (please don't bother bringing Toyota into this, it's really NOT a Toyota) will make peak boost between 3-4k rpm and taper towards redline. The supercharger isn't making any boost when the motor likes it and maxes out where it really doesn't run well with boost. The supercharger delivers hot air where the Subaru motor does poorly with it. Because of this, we tuners must take out gobs of timing up top and power suffers.

The classic, superchargers make more torque argument really does not apply here since the turbo makes fantastic power everywhere. It's kinda funny that the NA stock motor and the supercharged motors feel laggy while the turbocharged FA20 makes great power from idle to redline.

[buditjoenawan]

Originally Posted by Scoobyrs25

Ok, so what everyone is forgetting is the boost curve. The superchargers make peak boost at redline. A properly tuned Subaru motor (please don't bother bringing Toyota into this, it's really NOT a Toyota) will make peak boost between 3-4k rpm and taper towards redline. The supercharger isn't making any boost when the motor likes it and maxes out where it really doesn't run well with boost. The supercharger delivers hot air where the Subaru motor does poorly with it. Because of this, we tuners must take out gobs of timing up top and power suffers.

The classic, superchargers make more torque argument really does not apply here since the turbo makes fantastic power everywhere. It's kinda funny that the NA stock motor and the supercharged motors feel laggy while the turbocharged FA20 makes great power from idle to redline.

This is true only of the centrifugal type superchargers. Positive displacement types behaves sort of the opposite, but modern twin screws which compresses does far better in this department. But parasitic drag is still parasitic drag. No power is free.

budi

[Drift-Office]

Originally Posted by buditjoenawan

Then just get all three different kind of FI systems on the same day, on the same fuel, on the same dyno. The difference will be very apparent.

I might be able to arrange that. Not sure what the hoopla is about, some say torque, some say boost. People will want to see what they want to see though.

You can pump relevant information in their faces till they're blue but the bunch of armchair critics who've read a few books would certainly be able to tell you otherwise with obscurities to boot.

I prefer to let the customer's decide what's best for themselves, but certainly, cutting down on the noise is a different story...

Cheers!


Bob @ Drift-Office, LLC

[Drift-Office]

Originally Posted by SloS14

sorry, but horribly misinformed comparison.

Still waiting on how this is 'misinformed' since the dyno with sensors is how we quantify the tangibles like, HP/ TQ / AFR / BOOST as units of measure. That is unless, you're saying we've all been doing it wrong all this time?

Bob @ Drift-Office, LLC

[jamesm]

Originally Posted by carbonBLUE

i know boolean, its java right? i thought it was a mistype and i wasnt bashing you in any way or form lol

mathematical equations not preformed in computer language is what i am used to

i remember using boolean expressions in algebra 1 but that was back in the 6th grade... lol

it's the same for pretty much every language (with some rare exceptions). the sample was actually ruby. sorry, i'm a nerd.

[AVOturboworld]

Let's say that, for the sake of argument, the two main forms of FI are used to get towards a goal of maximum power on 93 octane gas on an identical FA20 with a free-flowing exhaust system, upgraded fuel pump, and upgraded fuel injectors. And lets say that, give or take 10~15ft/lbs, that is about 260 ft/lbs of torque. Because, of course, torque is what is being measured to produce hp figures.

Here is the possible issue - say the two systems are similarly efficient and are forcing in roughly the same amount of air into the pistons. Theoretically, they are all making the same power at that point give or take the compressor charge temperatures.

What modifies that value further, though, is the amount of parasitic drag.

Very unscientifically (since there is not a lot of specific figures):
Turbocharged system may reach about 255ft/lbs - loses some power due to the backpressure at the turbo.
S/C systems may reach between 210-240ft/lbs - loses some power due to parasitic loss at the pulley.

Now, that power lost to a pulley doesn't mean that the s/c engine is running at less power, it means that it's pushing the same amount of air and fuel into the engine, producing the same amount of power (or more) than the turbo, but that the pulley system is then eating up that specific amount of produced power.

[wparsons]

Originally Posted by Drift-Office

Still waiting on how this is 'misinformed' since the dyno with sensors is how we quantify the tangibles like, HP/ TQ / AFR / BOOST as units of measure. That is unless, you're saying we've all been doing it wrong all this time?

Bob @ Drift-Office, LLC

I would argue the dyno is misinformed because it claims that it's parasitic drag (pulley losses) making the entire difference in hp/tq. In reality the difference is from the boost curve, the compressor sizing/efficiency/etc and the parasitic losses of both the pulley on the s/c and the hot side on the turbo.

Claiming all the differences present in the dyno is purely from the parasitic drag needed to spin the supercharger is what is misinformed.

I'm not arguing that one will make more power than the other, just that there is a lot more at play than just the power needed to spin the s/c.

[buditjoenawan]

Originally Posted by wparsons

I would argue the dyno is misinformed because it claims that it's parasitic drag (pulley losses) making the entire difference in hp/tq. In reality the difference is from the boost curve, the compressor sizing/efficiency/etc and the parasitic losses of both the pulley on the s/c and the hot side on the turbo.

Claiming all the differences present in the dyno is purely from the parasitic drag needed to spin the supercharger is what is misinformed.

I'm not arguing that one will make more power than the other, just that there is a lot more at play than just the power needed to spin the s/c.

Aaaaah, I told myself I won't post again, but I have outed myself as a liar.

Even if what you say is true, then how does one explain when boost levels meet at 6500rpm? The Vortech car in this example has a full exhaust, so backpressure should be as low as it can possibly be - giving it a theoretical advantage over the turbocharger's turbine and housing. I have been corrected in that Vortech has indeed published their compressor's map. The AVO kit in question uses a 38-ish lb/min turbocharger (with a smaller hot side) and from the looks from the Vortech map, the supercharger has a 40 lb/min compressor at peak efficiency. So again, advantage supercharger. So yea, the chart does show, as well as it can, the difference between a supercharger and turbocharger's output to be mainly –*mainly –*drag induced. How else can you explain the difference in torque output at >6500 when boost levels become identical?

budi

[wparsons]

Because there are still more variables at play. Just because the s/c flows more at peak efficiency doesn't tell you how close to peak efficiency is it running on this engine at 6500rpm? More flow doesn't mean more efficient in every situation.

It's the same reason two different turbos at the same amount of boost won't make the same power on the same car.

The only way to measure the power difference caused by the parasitic drag on the s/c is to run identical compressor wheels and housings and regulate the boost pressure so they match up the same across the RPM range. You can work out theoretically how much hp the s/c needs to spin as well, but that's not measurable.

[200hp/tonne]

Or you could use the compressor work equation and factor in the isentropic efficiency (or adiabatic eff. in case of twin screw SC) to figure out power/torque consumption of an SC at a given boost level...

[Toma]

It is well known that moving air at pressure requires power. The superchaeger takes out of the crank. The turbo takes it from blowdown pressure. Some pumping hp and some temperature (as seen with the 300 degree temperature drop we have logged on a 12 psi kit across the turbine).

[Ammonia]

If you guys math any harder I will fertilize my keyboard