N/A or Boost.......

A naturally aspirated engine's output is determined by the position of the pedal and the engine speed, period. Turbos change that into a complicated matrix with far too many variables for a driver to keep track of.

"complicated matrix"??????

it's not that complicated if you know your machine and have reasonable hand-eye-foot coordination and can hear your engine. if the author can't "keep track of" that he sounds too stupid and/or uncoordinated to be driving anything.

Toyman01 wrote: The proper answer is a positive pressure supercharger of course.

Aren't they all? I certainly wouldn't buy one that wasn't.

Negative pressure superchargers suck.

Keith Tanner wrote: Negative pressure superchargers suck.

It's funny when someone does upgrades to their supercharged engine, then the engine makes less boost afterwards. Funny because the owner is often upset about this, completely ignoring that the supercharger is still moving the same amount of air, and actually it will be moving more air because less boost = more mass flow for a given supercharger speed. I've seen large, flow-efficient engines draw more air than the little eggbeater miniblower on top for visual effect could move, resulting in negative boost. "But it made 6psi before when it was smaller displacement and had a small cam and stock 50 year old heads..."

This came up in conversation yesterday, actually. An exhaust upgrade on a CTS-V had it lose 3psi boost. It gained 71whp, though.

MattGent wrote:

Toyman01 wrote: The proper answer is a positive pressure supercharger of course.

Aren't they all? I certainly wouldn't buy one that wasn't.

I guess I should have said positive displacement rather than positive pressure.

Centrifugal = no better than a turbo due to lag. They have to be spooled up to build boost but will build more absolute boost.

Roots or screw type, are positive displacement and are producing pressure at all RPMs and = boost at idle. They literally move more air than the engine can swallow at any RPM due to the displacement of the supercharger. That means no lag. They do suffer heat issues at high boost pressures that a turbo doesn't though. I still prefer them over the centrifugal.

I like both. Especially on L series engines but the turbo is just a little for fun for hoonery.

Toyman01 wrote: Centrifugal = no better than a turbo due to lag. They have to be spooled up to build boost but will build more absolute boost.

Centrifugal superchagers cannot lag because they are directly connected to the engine. You will never be in a situation where the engine is accelerating more quickly than the supercharger, unless the belt is slipping.

Roots or screw type, are positive displacement and are producing pressure at all RPMs and = boost at idle. They literally move more air than the engine can swallow at any RPM due to the displacement of the supercharger. That means no lag.

Positive displacement superchargers have a VE curve just like any other fluid moving device. They bypass internally at low speeds and they choke for flow at high speeds.

Laymen have a hard time distinguishing between lag and spool up time.

Keith Tanner wrote: Laymen have a hard time distinguishing between lag and spool up time.

Semantics, either way, you are waiting on boost pressures to climb.

I stand by my original statement. To live with daily, and for predictable driveability, give me a supercharger that produces positive, usable pressure at all engine RPMs. Waiting for things to spool gets old. What can I say, I'm impatient.

kanaric wrote:

Mr_Clutch42 wrote: I've autocrossed a 2012 Golf R that is turbocharged, yet it felt naturally aspirated, so it can be done.

I've driven multiple modern turbo cars and I don't see how anyone complains of lag anymore. It makes me think these are the people who complain about panel gaps on cars but only noticed them after Top Gear started to become popular. Maybe it's a factor for professional racers but they are like the NFL compared to our back yard football. Even then in pro racing turbos are incredibly popular. On the other hand on my Nissan you can very well feel the lag. However that is a 1989. Anyone who complains about lag and hasn't driven a recent turbocharged car needs to check them out again.

Minis turbo engine sucks for normal driving, has no torque to get the car moving when you are just trying to calmly leave a stop and then when you increase throttle the smallest amount, you now have all the torques.

I drive one quite regularly and cannot drive it calmly smoothly.

It's a 14 countryman s.

Keith Tanner wrote: Laymen have a hard time distinguishing between lag and spool up time.

I find a lot of people call lag just not being in the powerband. Like you are at 2000rpm and whining about "lag". Yes. You will how no power there. Neither will a naturally aspirated engine.

Opti wrote:

kanaric wrote:

Mr_Clutch42 wrote: I've autocrossed a 2012 Golf R that is turbocharged, yet it felt naturally aspirated, so it can be done.

I've driven multiple modern turbo cars and I don't see how anyone complains of lag anymore. It makes me think these are the people who complain about panel gaps on cars but only noticed them after Top Gear started to become popular. Maybe it's a factor for professional racers but they are like the NFL compared to our back yard football. Even then in pro racing turbos are incredibly popular. On the other hand on my Nissan you can very well feel the lag. However that is a 1989. Anyone who complains about lag and hasn't driven a recent turbocharged car needs to check them out again.

Minis turbo engine sucks for normal driving, has no torque to get the car moving when you are just trying to calmly leave a stop and then when you increase throttle the smallest amount, you now have all the torques. I drive one quite regularly and cannot drive it calmly smoothly. It's a 14 countryman s.

1.6l engine? I have only driven 2l or higher turbo cars. The Skyline i have is a 2l which is the smallest displacement turbo i've driven and it is a bit laggy and with little power under 3500 rpm.

Toyman01 wrote:

Keith Tanner wrote: Laymen have a hard time distinguishing between lag and spool up time.

Semantics, either way, you are waiting on boost pressures to climb.

Ever drive a car where the engine out-accelerated the turbo in lower gears? The boost doesn't climb until you shift and slow the engine's acceleration rate down.

That's turbo lag. I think what you are describing is just driving the engine outside of its powerband, which is something easily fixed by shifting into the proper gear.

Toyman01 wrote: I guess I should have said positive displacement rather than positive pressure. Centrifugal = no better than a turbo due to lag. They have to be spooled up to build boost but will build more absolute boost. Roots or screw type, are positive displacement and are producing pressure at all RPMs and = boost at idle. They literally move more air than the engine can swallow at any RPM due to the displacement of the supercharger. That means no lag. They do suffer heat issues at high boost pressures that a turbo doesn't though. I still prefer them over the centrifugal.

Actually it's worth noting that roots type blowers are different from twin screw or "whipple" superchargers. The roots type supercharger is often referred to as a blower because, like you say, it literally pushes more air into the engine than the engine can consume. Instead, the twin screw supercharger is actually physically compressing the air. Both are positive displacement superchargers but they function slightly differently. Screw type are a little more efficient and have a bit less issue with keeping heat down while pushing boost.

bL79 wrote: Actually it's worth noting that roots type blowers are different from twin screw or "whipple" superchargers. The roots type supercharger is often referred to as a blower because, like you say, it literally pushes more air into the engine than the engine can consume. Instead, the twin screw supercharger is actually physically compressing the air. Both are positive displacement superchargers but they function slightly differently. Screw type are a little more efficient and have a bit less issue with keeping heat down while pushing boost.

My employer mentioned that, on his dad's T/A dragster, switching from a Roots blower to a screw compressor sent boost up from 45psi to 60psi and it took signficantly less power to turn, too.

The part that blew my mind was that they were upshifting the car on a 5.5 second pass. I'd thought anything running that quickly was single gear and clutch slip.

kanaric wrote: I find a lot of people call lag just not being in the powerband. Like you are at 2000rpm and whining about "lag". Yes. You will how no power there. Neither will a naturally aspirated engine.

Disagree, they'll make plenty of power if properly designed for it.

My Super Coupe makes 315 lb-ft at 2600, in factory dress. It pulls well anywhere above 1800 to about 5K. Eaton blower.

My truck makes 400 lb-ft at 2200 and pulls well anywhere above 1200 to about 4500. It's NA.

They are both low HP, high Torque engines.

Having driven 700hp, 0 torque, fire breathing, turbo monsters, I still stand by my statement.

I prefer an engine that makes power from idle to WOT. Not one that struggles to get to 4K+ and pushes like the "hand of God" from there to redline. I like lots of torque throughout the rpm range, rather than lots of HP, but only in the twilight zone. Driving a peaky engine is like dating a high maintenance woman. Fun for a spin around the block, but you wouldn't want to deal with her crap every day.

It's a preference thing.

In reply to Knurled:

Yes, driving through town at 4000 rpms just so you have enough power to merge into traffic sucks.

Toyman01 wrote: Driving a peaky engine is like dating a high maintenance woman. Fun for a spin around the block, but you wouldn't want to deal with her crap every day. It's a preference thing.

Very well put.

Toyman01 wrote: I prefer an engine that makes power from idle to WOT. Not one that struggles to get to 4K+ and pushes like the "hand of God" from there to redline. I like lots of torque throughout the rpm range, rather than lots of HP, but only in the twilight zone. Driving a peaky engine is like dating a high maintenance woman. Fun for a spin around the block, but you wouldn't want to deal with her crap every day. It's a preference thing.

True, which is why N/A is best. Make power everywhere, not at the whim of whatever device is bolted on to cram more air into the engine.

Disclaimer: I do play with rotaries, which don't really have "powerbands" so much as you shift when you feel like shifting. I upshift my bridge port at 2000 or so in the city and I wind it past ten sometimes when racing. It's perfectly happy with either

Bragging about "OMG the TORQUE!" just means to me that the engine has a narrow powerband that forces you to shift early.

^ Torque envy

Eh, it's traction problems on a 95 inch wheelbase. Whatever amount of torque I make, it's a hair too much, until I find more traction anyway Then I'll drop the final drive down until the traction problems come back...

My first car had a 429. Even then, it bugged me that the engine didn't make power past 5k. NASCAR ran to 7500+, I wanted that.

My second car had an EA82. Talk about your paradigm shift. And narrow powerbands, it made power exactly from 3500 to 5200 and nothing above or below, to the point where it would not cruise at 60mph at 2800. Internet lore said those EA82s were "torquey". I decided the Internet was full of E36 M3, it's not torquey, it just doesn't rev very much.

My third car was an RX-7. Finally something with a decently wide powerband

I love my turbo C30, so much instant torque at low rpm. Ask Tom Spangler, he's driven it. I feel no lag, but it's a properly sized turbo not a high end blower. Properly sized turbos have no detectable lag.

In reply to Knurled:

Disclaimer.

You have seen this I assume? It's in the driveway. Granted, it's blowed up.

And this? It's in the garage.

Both of mine are NA, carbed, 12a, so I usually shift before 8500.

Edit some more: I'm well versed in the addiction that is magic spinning triangles.

So yeah, there is that...

Edit: It's all good, it just a difference in preference. I love a turbo, I love a supercharger and I love a big honking torque monster. Day to day, I'd probably pick a SC. Instead I drive a Ford van because it does what I need it to.

Another edit: 4.2 in the van, 3.8 in the SC. I little machining...Hmmm...

Sorry for all the edits, the drugs and fever are really starting to get to me.

Adrian_Thompson wrote: I love my turbo C30, so much instant torque at low rpm. Ask Tom Spangler, he's driven it. I feel no lag, but it's a properly sized turbo not a high end blower. Properly sized turbos have no detectable lag.

He speaketh the truth. For that matter, neither does my Ecoboost truck. My '86 951, on the other hand, was a different story.....

Anyhow, can't I love both? I love the instant torque and wonderful sounds of my GTO, but I also love the easy tunability and whistle of a turbo motor. For a track car, I generally prefer NA for heat reasons, but that's not an absolute, either.

Knurled wrote:

Toyman01 wrote:

Keith Tanner wrote: Laymen have a hard time distinguishing between lag and spool up time.

Semantics, either way, you are waiting on boost pressures to climb.

I think what you are describing is just driving the engine outside of its powerband, which is something easily fixed by shifting into the proper gear.

Exactly. A naturally aspirated engine with high specific output usually has a cam profile that means you need to spin it to make power.

Example! I've had several examples of Miata 1.6.

Here are three dyno charts of Miata 1.6 engines making around 150 rwhp.

This one's naturally aspirated. High compression, fairly hairy cam, individual throttle bodies, etc. The two runs compare two different length velocity stacks which is interesting on its own.

This is another one with a Roots supercharger and a turbocharger. This chart actually shows the same car on different days, it's the most direct comparison you can get! For those who care, it's an M45 supercharger and a little GT2554 turbo.

Now, the naturally aspirated engine dyno has SAE correction applied - as it should at 5000' elevation. The forced induction ones are not because the ultimate power of this car comes from the injector size, and corrected numbers would not reflect what would actually happen at sea level.

You can see how the turbo car has just as much going on at 3000 rpm as the naturally aspirated one does. More, really, as the N/A engine is corrected. So spoolup is obviously a problem on naturally aspirated engines You need to be "on cam" for the engine to perform, the spool up is no different. And of course, spool behavior on a smaller turbo is not an all-or-nothing thing. The turbo may not make peak boost until 3700 rpm (in this case) but it's making some boost just off idle and the boost level continues to rise.

Now, if you have a big max power turbo, the transition will be more abrupt when you get to the spool point. Just like a "full race" cam will hit hard. No difference there.

Once you're above that boost threshold, lag comes into play. That's the delay between you asking for full power and it being delivered. It's usually pretty small and you can adapt to it very, very quickly.

Now, of these three engines, the turbo is the fastest one. And it cost the same as the supercharged version. The naturally aspirated version is the most expensive - but it's also the most glorious to drive. It's the most operatic engine I've ever driven. So much fun, so characterful, so annoying if you let it drop below 4000 rpm coming off a corner.

BTW, on Roots vs screw superchargers, the screws are more efficient at full boost but less efficient at partial boost. Not an issue for a drag car, but more of an issue for street cars as they can heatsoak more than you'd expect.