What does GRM think of the Supercharge vs Turbocharger debate?

Ever since I have begun my mechanical (motorsports) engineering degree, I seem to find myself in supercharger vs turbocharger debates on a weekly basis.

I feel like when approaching this issue we need to narrow our thought process down. First off, I feel I can assume that most of us are not drag queens. We all prefer turning left and right when we race. It would seem to me that we would want something that gives us the most linear response when we roll on the throttle post apex. My first inclination here is supercharger, even though I've always loved the design of a turbo system.

Let's assume we are talking about an inline four engine, as I feel most of us use the straight four. Let's also assume that we are not primarily drag racing.

There are a few key things that I would like addressed.

1) low end torque (idle to 2500 rpm)

2) mid range torque (2500 - 4000 ?)

3) high end torque (HP) (4000 - redline)

4) effect on engine longevity at similar power outputs

5) effect on cruising gas efficiency

From the little I know about superchargers, it seems to me that:

1) supercharger would produce the best low end torque

2+3) the turbo would produce the same or more mid/high tq

4) I have no idea what the difference in intake temps would be

5) the turbo must be more gas efficient because cruising throttle sees no boost

It also seems to me that a supercharger would be best on a roadcourse / autocross because it would give you instant linear power.

My only experience with a supercharger was a mini cooper S. There was no lag. One of my experiences with a turbo was an 06 STi. E36 M3 hit like a brick comparatively.

I just love the sound of a supercharger, that would be my main consideration in adding one to my car.

I also love the sound of a turbo though so it would be a hard decision.

10 pounds of well tuned boost is 100HP (kinda).

with a turbo, its 100HP with the cost of exhaust pressure stealing back 10HP (again, kinda)

with a SC, it takes 30HP (30% of total on average) to make the same +100.

your max power at identical boost levels/tune would almost have to be lower with a SC. other than that, i agree with Taiden.

all i remember is an article about a 4.6 stang with a supercharger. the rag swapped in a turbo, nothing else. ran stock ECU tune, boost levels, manifolds, throttle body, everything they could. went from 336 HP to over 400. at the same boost. cranked it up to 15psi, added a chip and injectors, and it was 450HP. im paraphrasing intensely, and the numbers are likely wrong, but the effect was there, and i was sold. i bolted on a 50trim precision turbo to my thunderbird three months later...

JMHO

-J0N

oh, i like game shows...

Super charger: What is... Parasitic drag...

Turbocharger: what is... excessive plumbing..

lots of advantages of each, but i always felt the only debate has to be about a specific set up vs general. there are many instances where a turbo would be better, and then again, just as many where an sc is a better option.....

1) low end torque (idle to 2500 rpm)

Can't say I've ever found a need for boost pressure at idle.

Fwiw, I've found having a boost build curve that roughly follows the power curve of the engine to be the most pleasant. Sizing really matters. Volvo has some shining examples of this with their turbos (regular or GLT turbo vs the R or T-5 turbos).

4) effect on engine longevity at similar power outputs

Boost pressure is boost pressure. At least as far as the crankshaft and piston are concerned. There can be some differences as far as the oil is concerned, particularly with an oil cooled turbo vs a sealed bearing chamber supercharger. But those are more matter of the turbo life vs the supercharger life, not the life of the engine.

5) effect on cruising gas efficiency

Most of the loss of gas mileage is from the drivers foot stimulating the drivers mind with the "whee!" factor of a blown engine.

Under mild load steady state cruising, N/A or blown are very similar in fuel use. Under heavy load (trailer towing for example), where the boost is being used to perform work, mileage goes down.

I like both, at the same time.

Really.

Actually I am dreaming right now of building a 3.0L DOHC Ford with two Mitsubishi eclipse turbos (one from a manual and one from an automatic) as well as an older Vortech supercharger all running through one large FMIC with a digitally controlled blow off valve that controls boost pressure release and softens out the peaks.

I would really like to hook it to a Focus six speed but a Contour five speed will work fine.

Best answer?

Run both.....then show us

disclaimer: this post was written by a guy with only naturally aspired engines in his stable

Positive displacement blower=instant gratification. They're not perfect but they produce gobs and gobs of torque, and torque is fun. At one point the engine on my Supercoupe was only making 312 RWHP but it made 446 RWlb-ft. Someone mentioned no need for boost at idle, but having all that torque down low means less need to shift on an autocross course. I could just leave the car in second and no matter how slow I got (almost) the car could still pull out of the corners like nobody's business.

Yes, a turbo will make more peak hp for the same amount of boost. It's a tradeoff.

I had formerly been on the suercharger side of the debate, but have been coming over to the turbo side.

which type of S-charger? positive displacement (roots, whipple, ect) or scroll type (vortech, paxton, powerdyne) these have different charastics

• positive displacement very good instant response and low end power, poor ability for heat management. If you are going out on a road course its gonna be a problem.

• turbo, easier heat management, ability to computer control the boost level (subaru at our local auto-x has a instant boost button on the steering wheel (jumps to 450 crank HP )

• belt driven blowers, i have seen problems with belt longevity

apples and oranges, but there are some shortcomings to some.

3 words for you, "variable vane turbo"

Porsche has them now and they are the way of the future.

To me they are two different tools to do the job. Nothing to really debate; its a game of trade offs and money.

I remember reading that the new ZR1 supercharger consumes 70 horsepower off of the new Corvette's engine. So when they read the power at the flywheel at 640 hp or whatever it is, its actually 70 hp more, so actually the engine's internals are really producing 710 hp. Just something to think about when considering durability and longevity.

I would rather drive a NA car on a road course any day so really, to me, they are just ways to get more power with some degree of compromise to each. I dislike the additional complexity as well. A high-revving responsive NA motor is a hard target to beat.

The supercharger is a little like NA in delivery but it has a drag that if not properly compensated for feels like a huge heavy flywheel. I have driven a few twin screw BMW M3s and its a pretty impressive result anyway. One of them broke head gaskets in two seperate weekends so I'd say there is some extra stress on the hardware but... that could just be the wrong motor to go putting more atmosphere into w/o dropping the compression. I'd go this route only because I had to to run with the class with whatever motor I was stuck with.

Turbos demand that you work around them... the older 930 Turbos come to mind. If you were even a little wrong complete lack of thrust would follow... then total chaos. Some of the newer cars seem better but my experience with puffers has been with overheating, pinging, and generally finicky driving mannerisms that make it a drawback. I would avoid it completely if at all possible.

GregTivo wrote: 3 words for you, "variable vane turbo" Porsche has them now and they are the way of the future.

Shelby did them 20 years ago and they were the wave of the future when the Shadow was the hot compact ticket.

So were the polymer wheels that also never caught on!

I had a small turbo (Drag racers and some others would say undersized :) ) 2.4, and power was available EVERYWHERE off idle. Response wasn't a problem, though it definitely ran out of steam above 6k rpm. A turbo can often be sized to provide very similiar power/response to a supercharger. I'd like to have either in the M3, but a recent auto-x schooled me as to how unnecessary more power will be right now.

The variable vane turbos are not the future (IMHO), they're complex and costly, see prices on them and rebuild costs. Variable geometry turbines are the future...

Varbiable geometry turbine housings are a much simpler and cost effective solution, such as what's found on the new breed of VGT3xx, 4xx, and 5xx series from Holset. They have a moving housing that actuates based on a number of inputs to the control unit such as RPM, Throttle position, Boost level, etc (full list availble on Holset's site). This is the way of the future IMO because it solves the down low boost issue of a turbo because you can operate it at peak efficiency from idle to max power with the correct application exhaust housing geometry. Now it will never be quite as efficient as variable vane because that prevents flow separation around the vanes due to correcting the vane angle for a given flow rate but it is simpler, costs less to implement and the only penalty is some added weight to the turbine housing (10-20lbs heavier, not too bad a tradeoff for the simplicity, read reliability, of the design).

There's a fella, Aero, who's on multiple other boards (DSM Tuners, TurboTalk, TurboFord, etc where this debate has raged) has a VGT3XX series on his DSM and it produces significantly better boost results down low than a traditional turbo. The only thing is since no one has been able to figure out how to control it with the OEM controller he's got a manual wastegate on the actuator arm to open the turbine section as boost builds to prevent overspinning but at the same time not open to fast to have a huge lag. This form of manual actuation is cool and alternatively you could give yourself some neat capabilities with it. Say for instance you wanted 3 different tunes, one for drag, one for autoX, one for street, you could add a stepper motor to 'preset' the initial turbine housing size to give you quicker boost response, slower boost response, or something in the middle. Add a MegaSquirt or other stand-alone with one of those nifty aftermarket LCD interface controllers that can carry multiple tunes and you could have multiple 'turbo/tune' options at the flick of a switch. Or figure out the best variable setup and have all the low end boost of a supercharger with the peak power of a turbo, with the efficiency of a turbo, and the ease of temperature control of a turbo, albeit with more plumbing...

They all push me down the track. I just use the one that fits the application.

My Miata was built for boost of some type. It has a total of 100hp. I'd rather not lose any of that to...making more power. So I went turbo. Seems to work well and ultimately make more power than a supercharger pushing the same amount of boost (5 - 6 lbs).

If I had a V8 would I go the same route? Don't know.

I can say, after turbocharging my Miata I'm looking at all sorts of vehicles in a different way. 4.0 Liter Jeep's? Hmmm....

I prefer N/A on everything. BUT.... the tow rig/family hauler is the only one I'd consider F/I on and that would be a whipple-esque roots style blower. The truck LSx motors love s/c and my 4.8 could use a little more low end grunt.

Lets see, picking a power adder....do you pick something that spins to 120,000 rpm and see's temps of over 1,000 degres F, or do you pick something that might spin to 20,000 (roots type) and may see 200-300F temps? Turbos will make more power but for something you can bolt on and leave alone for 100,000 miles, take the blower....

A few points. First, most "roots" type blowers have a bypass for idle and cruise, so they don't create as much drag as they used to. Second, IMO centrifugal blowers are a horrible choice as they have all of the downsides of both a turbo and a blower. And third, I love properly sized turbo applications but if you mess up driving the off-boost power is torture.

I used to be heavily into turbo cars (DSM's, 2.3T Fords, Turbo Probes, etc) but once I started racing N/A they love went away. While great for good response or big power, to do both required more money and engineering then I cared to have in a car. Now I'm on a roots blower kick. The instant power, gobs of torque, and new efficiency are all drawing me in. I've taken a few rides in upgraded 3800 S/C cars and a twin-screw Cobra and I'm really seeing the technology march.

Eventually my RX-7 will be sporting a Camden Supercharger in SSM. And although I'm likely to stay N/A with the P71 (with an LSx swap) I have an AMC 401/5-Speed combo begging for a car, and the 9.5:1 compression (which drops to 8.5:1 with aluminum heads) is begging for boost...

Raze wrote: Variable geometry turbines are the future...

I used to work for Holset.. which is now Cummins Turbo Technologies. They're already moving on from this technology to other technologies. It is not the "wave of the future" They'll be around for a while, but people are dumping them due to their innately sensitive nature. They are very prone to sticking and are very sensitive to foreign objects. They are more durable than a swing vane(and cheaper) but they are less efficient of a device. They produce more backpressure at certain nozzle positions than should really be allowed. In back to back testing the Holset's are also less efficient. They work good, but aren't as good as a swing vane, hands down. Porsche would never be caught with a Holset. I also worry about their current "cost savings" initiatives...

Sizing. Get it right and either can be beautiful. Get it wrong and either can suck. In general, the "rules" are spouted off by nitwits who don't know what they are talking about.

mustclime wrote: Lets see, picking a power adder....do you pick something that spins to 200,000 rpmand see's temps of over 1500 F, or do you pick something that might spin to 20,000 (roots type) and may see 200-300F temps? Turbos will make more power but for something you can bolt on and leave alone for 100,000 miles, take the blower....

FYP.

But I do want to point out that the parts in a turbo are very much designed to survive that kind of treatment for the full lifetime of the vehicle. At least in new cars. If you buy good parts, even bolt on hardware will survive just fine.

Eric

Someone mentioned that roots-type (positive displacement) superchargers make lots of heat. They do, but methanol injection does wonders for them. On my SC the meth injection only made an extra 13 hp at peak, but the higher the revs, the higher the boost, the higher the temps. Once past peak meth provided 40 extra hp and 40 extra lb-ft.

Also, roots blowers are by far the cheapest, most reliable way to hit a given power figure. There's a reason OEMs choose them. They're also great on heavy cars like the SC, Cobra, Lightning and GTP.

I'll admit I'm a bit of a roots fanboy. They don't solve all problems but they're great at solving specific problems.

alfadriver wrote:

mustclime wrote: Lets see, picking a power adder....do you pick something that spins to 200,000 rpmand see's temps of over 1500 F, or do you pick something that might spin to 20,000 (roots type) and may see 200-300F temps? Turbos will make more power but for something you can bolt on and leave alone for 100,000 miles, take the blower....

FYP. But I do want to point out that the parts in a turbo are very much designed to survive that kind of treatment for the full lifetime of the vehicle. At least in new cars. If you buy good parts, even bolt on hardware will survive just fine. Eric

I was trying to keep the numbers low so noone would call "bs" but the point is the turbo's have to "live" with some tough heat cycles....yes, they are designed to do that but some do and some do not.....imo turbos are great for race cars and show cars, blowers are great for a dd cars.