What does GRM think of the Supercharge vs Turbocharger debate?

I don't care what's compressing/pumping your air. It's all about the implementation. People get wound up in the fundamental technologies and forget about that while having internet pissing matches.

Porsche uses turbos. Ford used superchargers on the GT40 and Aston used them on the Vantage 600. MB went from superchargers to turbos. VW checks both boxes. The auto makers can't decide either!

In the Miata aftermarket, we have a customer with over 300,000 miles on his turbo kit. Turbo failures are extremely rare - we see about as many weird engine failures ("you broke a camshaft??") as we do turbo failures. Magnusson recommends rebuilds every 100,000 miles on the M45, but there are a bunch of Miatas out there with at least that much or more on them. I've seen badly designed setups repeatedly toast high-end twin-screw compressor bearings, and I've seen turbos starved of oil. So again, reliability is a function of the quality of the implementation.

If you spend a few minutes driving a turbo car, you can adapt to its power delivery if it has anything odd going on. Same with a supercharged car - if it's mounted in a way that increases the throttled volume you can get some weird behavior. I've actually run the same car both ways and it took no time at all to adapt to the change in the spinning stuff underhood.

As for fuel economy, on a highway cruise, we usually see a slight increase in mileage with the turbo and a slight loss with a super. Not much - 1-2 mpg - but it's there. We see a bigger change from engine management and even more from driving style, of course.

I personally like the smooth power rise of a supercharger, no nasty surprise sudden boost waiting to pitch me in the ditch. I have driven several turbo cars and all of them had some 'hit' unless you did all kinds of fancy footwork to keep it spun up. I ain't that coordinated.

I plan to run a 13BT (single turbo) in the Jensenator eventually and I guess I'll either have to learn that fancy footwork or plop down the bux for a Vortech or similar.

I like the Roots type blower for compact size etc but there's a lot of difficulty running an intercooler. A Vortech would be pretty easy to intercool but the setup takes a lot of room.

There's no such thing as "surprise boost" on a turbo car. Unless something's really wrong, it will deliver its power exactly the same way every time.

Keith wrote: I don't care what's compressing/pumping your air. It's all about the implementation.

winnar...

I've seen stock big rig diesels get 500,000 and more miles on a single turbo. They were designing for a 1 million mile service on the turbo of a 15L when I left. If the turbo or supercharger dosen't last a long time, then I think you've boffed up your installation. Most likely poor matching and oil starvation.

Oil starvation, mostly improper flow, is what killed 95% of the turbos I tore down(Could be from cold temps or coking due to improper use, but still flow killed them) I used to do failure analysis for a turbo company for a living.

ignorant wrote:

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...

How many people are 'dumping them'? I've read all about the sticking issue, doesn't seem like anything a redesign couldn't correct. As for FOD, no turbine/moving part is going to accept FOD 'well' or be 'insensitive' to it. If you're talking about smaller sized FOD than normal turbos causing problems that's kinda to be expected due to the tolerances and the extra moving parts. Like I said in my earlier post, they're not as efficient due to design (I worked for Pratt & Whitney designing commercial and military engines) but the genuis of the design isn't the efficiency, it's cost, and similicity. Fix the sticking issue and you're in business for alot less than the cost of the variable vane tech, just my opinion.

Keith wrote: There's no such thing as "surprise boost" on a turbo car. Unless something's really wrong...

like overflowing your wastegate or having a wastegate actuator failure :)

Keith wrote: As for fuel economy, on a highway cruise, we usually see a slight increase in mileage with the turbo and a slight loss with a super. Not much - 1-2 mpg - but it's there. We see a bigger change from engine management and even more from driving style, of course.

To get the fuel economy, you need to do more than just slap on a "boosting" system. Probably the cheapest way of doing it is using a much taller final drive- say on the Miata, put in a 3.6x from a 4.10 or 4.40. WIth the available torque, the no downshift performance is normally good enough to warrent the much lower engine speed for cruising. It's bascially the reason why the Solstace GXP got SO much better mileage than the n/a Solstace.

One has to engineer it as a system to really take full advantage of it.

BTW, Raze- on most modern control systems, even IF you broke the wasgate so that it's always stuck off, you can control things to "limp" quite well to the dealer to get them repaired and not break anything.

After working on gas turbos for roughly the last 6 years (I did Panama prior to this GTDI work I'm finishing now, for those of you who have some inside knowledge), I'm really appreciating what modern, well engineered turbo systems can do.

Still, there are tradeoffs to both side. Just on my specialty (emissions), I can fill a page from both sides.

Basically, done right, neither side is wrong. And neither side is right.

Eric

alfadriver wrote: BTW, Raze- on most modern control systems, even IF you broke the wasgate so that it's always stuck off, you can control things to "limp" quite well to the dealer to get them repaired and not break anything.

I agree, I only mention it because we just overflowed our wastegate due to a mismatch of sizing vs wastegate sizing...

I guess I should expand on 'surprise boost'. What I mean is that yes turbos do have a 'lag' still (or at least every turbo car I have ever driven does). So if a situation arises where I have to slow way down for a corner and then get my boot back in it, unless I do all the fancy footwork necessary to keep the boost up there's a lag which messes up my driving 'style' (ha ha). Since I'm lazy I prefer a smooth power delivery.

It's a simple issue to me. If torque isn't your #1 priority and you can wait a second for the power to kick in, use a turbocharger. Otherwise, use a supercharger.

Raze wrote: How many people are 'dumping them'?

Cummins and Holset want to due to the massive warranty costs; and I mean massive. New engines will be much more less reliant upon the technolgy and it will go away shortly.

I've read all about the sticking issue, doesn't seem like anything a redesign couldn't correct.

HAHAHAHA.. I'm not laughing at you, It just I was in product development for many years. Sure we could fix the problem, but never for a cost that made it worthwhile to produce. However, 5 years into the product and they only realized the problems they had when they switched to a much more sensitive control system(electric actuator). The materials are already so specific and expensive that further forced cost reductions have been made. This of course causese more problems in the field. As for FOD, again it has always been an issue with turbos, but again never shown to be a large issue until the electrical actuator came into being. The old pneumatics would just ram through any issues with a mighty push. The electrical actuator is needed to meet the accuracy requirements that are needed to provide the emissions.....

I can go into detail further but.. the design is so interconnected that say a change of 100 microns on the tolerance around the vanes to make them less sticking prone cause cause you MASSIVE effeciency losses.

I can't say what they're made of out, but those little pushrods that attach the nozzle to the vg mech are made of some expensive prorietary stuff. Each rod, on a Heavy Duty turbo, is worth about as much as a nice dinner for you and the missus. That was cost we had to add in to make them less sticky. The company is working on it, but the newer engines will have more conventional turbos on them, urea takes care of the emissions so no need for mechanical wizardry.

I have both. A supercharged Mini Cooper S and a Sequentially turbo charged 93 RX7. Both are cool.

With the sequential turbos, I get a nice kick when the second turbo comes online. The kick is also partially due to a 2 lb drop in boost as the transition occurs. If it weren't for that, it would be seemless. You can't feel the primary turbo become active. Size the turbo appropriately and you won't really feel that big of a kick.

I also had a few FC Turbo II RX7 with their small OEM turbos. I never really noticed a big kick or transition as the turbo spooled up. Unless of course it was equipped with a larger turbo or a intercooler setup with miles of piping. A short intake/IC tract helps with that laggy feel and the kick associated with the turbo coming into boost (along with an appropriately sized turbo).

For competitive road racing, give me NA. Too much heat management and expense related with FI setups.

For me its engine size, below 3 liters turbo, above 5.0 supercharger. Above 10 liters turbo again.

I drove a bud's 300ZX turbo with a big intercooler and all kinds of piping, that thing made SERIOUS horsepower but it has (to me) pretty serious turbo lag. Darth Chuck (the owner) could drive it like nobody's business until it blew up, he was always a serious threat for FTD. (He's currently building another one which should be even quicker.) He turned me loose in it one day and I floundered around like the squid I am. It took about 3 runs for me to get where I didn't semi loop it at least once. Of course, this was greeted with much hilarity by the crowd.

Turbo tech has come a long way since the 300ZX was new, as has engine management. If you're building an autocross car, you'll typically use a smaller turbo than you would if you're building for serious horsepower. If you've got a car with a big turbo, it'll hit hard. Seat time would definitely be an advantage! We had a Miata here for a while that had nothing below 4000 rpm and then all hell would break loose. You could drive it smoothly, but not on first acquaintance.

My wife's Miata used to be supercharged. I pulled it an installed a turbo. Same engine management. The car is just as easy to drive now as it was with the super. It took no time at all for her to learn to autocross it, but it's not a big turbo. It's never going to make 300 hp, but that's not what she wants. Again, implementation.

Well, it's not what she wants in this car.

Heard at Keithco : "Keith, hunny, can a ZR1 6.2L supercharged engine fit under the hood of the BGT?"

DILYSI Dave wrote: 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.

Anyone remember a Chrysler 2.5 auto with the mitsu teo4h? Yes, boost off idle was possible, no, high rpm's were not possible. The current mopar 2.5 turbo I have would probably show a 100 hp difference over a 500 rpm change. Yes, I'm doing it wrong, but its fun.

In a recent article I read about Callaway performance (corvette turbo guys) they discussed their change to superchargers. The main argument was: for a larger company to produce power increases with the lowest cost and lowest warranty issues, superchargers produced greater bottom line profits. That's all. Not more power, not better delivery etc, simply the cheapest avenue for the narrow market of C6 corvettes.

The biggest problem we are seeing with the VGTs is soot building up and sticking the vanes. Gas engines don't have this problem anywhere near what we do with our diesels. one of the biggest reasons alot of diesels are having issues is that they don't get run hard enough to prevent the buildup. I have been researching vgts for my jeep project.

I've got a '97 M Edition Miata with a coldside M62 blower. I love the sound of it (and the Borla duals) when I put my foot in it. It delivers solid power from the time I do step down. It's an early Jackson Racing supercharger and the belt tension is adjusted by the stock alternator bolt. This makes belts somewhat of an issue, probably the only real problem I've had with it since I bought it about six months back. I've about gotten a handle on adjusting them, but it ate several before I got the knack of it. (BTW, if someone knows a source for a more advanced belt tensioner for it, I'd love to hear it. Everything I see looks like it's for the newer version with the blower hotside.)

My biggest disadvantages are the belt design, gas mileage (mostly my fault as I flog it pretty hard virtually everywhere I go), and the need for premium gas. OTOH, it's a joy to drive, makes me grin till you can count molars, and the premium adds a measly two bucks to a fillup, so screw it.

We've had four Miatas now, a 96 M and a '99 NA, and a 92 with the M45 and the 97 with the M62. Every one has its charms, but the '97 narrowly edges out the '99 for my favorite.

Guess I'll have to try a turbo on the next one. I can't talk intelligently about them yet.

MA2LA wrote: . I have been researching vgts for my jeep project.

Gas engines will have the same problem. A good bit will be from the fact that the balance holes in the nozzle ring are specifically designed for the gas loading of a very specific engine. If you do not have flow balanced between the main gas passage and the flow that "escapes" behind the nozzle you can get into some very funky actuation characteristics. One of the most famous is being sucked shut. Where the nozzle ring will move on its own and close off the nozzle gap. If this happens at any appreciable amount of engine RPM's turbo overspeed will occur. Gas engines also tend to crack shroud plates( when run hard).... Now thats a sicking situation that you won't find info about.

MA2LA wrote: The biggest problem we are seeing with the VGTs is soot building up and sticking the vanes. Gas engines don't have this problem anywhere near what we do with our diesels. one of the biggest reasons alot of diesels are having issues is that they don't get run hard enough to prevent the buildup. I have been researching vgts for my jeep project.

I agree, I know this is partially true because on our Holset, it had alot of soot deposit buildup from the diesel rig, now after running in a gasoline engine you can eat out of the turbine housing, and even the 3" downpipe that came with that was all sooted up has been magically cleaned out...

Only direct supercharger vs. turbo comparison I can make is the MINI Coopers I used to have regular access to. The SC engine they used at launch was just fine and would make more power with a pulley/standard stuff. It felt like a reasonably quick car.

The turbocharged version they launched a few years back felt like a completely different animal. It accelerated hard, had very little lag and pulled hard all the way to redline. Yes, boost would hit more suddenly than the SC car and torque steer was more apparent, but nothing that couldn't be controlled when driving fast.

Given an opportunity, I'd take the turbo MINI any day of the week. Great response with a smidge of sacrifice in power delivery...but again, not enough to be significant IMO.

What about idle drop with superchargers?

I will let you know this fall when the Ti gets the downatlanta SC... then I will have a NA Fiat, SC BMW, and TC Saab...

honestly, the saab drives me crazy with it's power delivery.

Here's one data point. I have a stock 2001 Toyota Prerunner and drove it a while as-is, then had the dealer add the Eaton Supercharger (it's a factory option.) It raised power from 190 to 270 hp.

For a V6 DOHC truck it was perfect, filling in the low-end torque typically missing from smaller truck engines. I did notice though that the higher the revs, the less it seemed to work. Kinda like dating a supermodel where she starts to remove her top, and you're thinking, boy, this is going to be a great time. Then, she suddenly remembers she has a date with someone else and leaves you sitting there - every time!

As far as reliability goes, the nose bearing went out at 70K miles, sounding like I had a diesel in the car. Got it fixed, then at 75K, it started to fail again. Took it off and am happy to be rid of it.

The mid-engine Locost on the other hand will have a turbo 2.4 liter Honda, THAT should pull to redline instead of leaving before the fun starts.