Now, if we're throwing specific output out as a factor and just looking at absolute output, here are two more Miatas making about the same power. As you can imagine, they drive very differently. One is a highly boosted 2.0, the other is an 11:1 6.2 with a very entertaining cam. They're both pretty quick on the track but there's a massive difference on the street.
Oh, and OMG the TORQUE 
Look at how narrow that power band is.
In reply to Keith Tanner:
The pictures in the other post aren't working.
Of the two above, I'll take the blue one. 
If CanAm taught us anything, it's that more power is always better. Doesn't really matter how, just more, and let the driver sort it out. 
In reply to Keith Tanner:
That blue line is what my torque curve looks like, but the horsepower goes flat over 8500 or so instead of 6000. So my question would be, what does it take to get another 2500rpm of powerband out of that thing?
In reply to Knurled:
Cubic dollars.
In reply to Toyman01:
But the Internet told me that piston engines are a lot cheaper than rotaries
My $.02: I went boosted because of the very real loss of power as altitude is gained in a hillclimb. With N/A engines you start off at a power deficit because of the thinner air, when you gain a thousand feet of altitude over a 2 mile course it's even more pronounced toward the end. I'm willing to accept the tradeoff of some turbo lag in exchange for having more Hp/torque when I really need it. I use the stock Hitachi HT18 instead of the larger units everybody else is enamored of specifically because while it has some lag it's not as much as a larger turbo. Stock RX7 TII dyno chart:
Notice how flat the torque chart is compared to some peaky dyno queens, I'm going to say Mazda did their homework on this setup. On my car, the HP signs off at about 6700 RPM in 5th, beyond that it doesn't want to pull any more. before everyone rolls their eyes, given the 28 inch diameter tires, 4:30 rear axle and .7 transmission ratio that's about 141 MPH. 
With a few aero mods like a short windshield I think I could bump that to about 150 MPH.
I'm willing to trade some max HP for driveability and so far it seems to have been a good decision at the open track events I have run with it. Vid of Road Atlanta event: https://www.youtube.com/watch?v=LMV4hjJQGOg The 6700 RPM/141 MPH was achieved on the back straight.
On the subject of lag: even though the TII wasn't unmanageable in this respect Mazda went through a lot of trouble to design the sequential turbos for the third gen RX7. Having driven more than one example of that wunnerful car, I can say they did a good job of making a broad powerband and good driveability combined with raped ape acceleration.
The next thing you know people start running them on dynos in search of that magic max HP number, the first thing they do is rip off the carefully engineered sequentials, throw a big single on in their place and go after that magic max number completely ignoring the driveability side of things. 
Knurled wrote: In reply to Keith Tanner: That blue line is what my torque curve looks like, but the horsepower goes flat over 8500 or so instead of 6000. So my question would be, what does it take to get another 2500rpm of powerband out of that thing?
You've got 400 ft/lb or more from 3000-8000 rpm? That's impressive. Got any charts?
The engine in that car can be bought, brand new, for about $7500 with a two year warranty. Dunno if I'd consider that expensive. It's flexible enough that I can lap Laguna Seca pretty quickly without having to shift out of fourth gear - although I do hit the limiter in a couple of spots on the track in that case due to the narrow power band
Mazdeuce is right, Can-Am proved that when it comes to power vs power/weight...power wins.
Curmudgeon wrote: The next thing you know people start running them on dynos in search of that magic max HP number, the first thing they do is rip off the carefully engineered sequentials, throw a big single on in their place and go after that magic max number completely ignoring the driveability side of things.
Not all of them.
http://www.rx7club.com/single-turbo-rx-7s-23/autox-fd-dyno-956766/
Note similar powerband to twins but a lot more of it. Early torque peak that fades yet carries out a long time is excellent powerband shape for a traction limited car, IMO.
Keith Tanner wrote: You've got 400 ft/lb or more from 3000-8000 rpm? That's impressive. Got any charts?
No, it's more like 170 or so ft-lb. I'm not all that interested in how much torque, just how broad the expanse is. It's already too much torque for the traction available, but having a broad expanse is critical for being able to drive the car instead of constantly screwing around shifting.
As a bonus, when the fuel pump starts crapping out because it's overheating and also sucking air, it doesn't kill the engine when it runs dead lean at peak power and the driver keeps his foot in it because lifting is what people who aren't fast do
I like the torque curves you get from positive displacement. This my Focus, 2.0L 4 cylinder with an M62 supercharger.
In reply to Knurled:
Yeah, not everybody goes bonkers. He even says he's surprised to 'get that much from such a small turbo' and being an autocrosser he's not going to go nuts on the compressor size, he wants it to spool quick at low RPM to avoid lag.
Typically, the bigger the turbo the more it shifts everything to the right of the dyno sheet and adds to the peak, but the loss on the left side is felt as 'lag'. That's what a lot of those guys are looking for, a dyno sheet they can wave around. problem is they wreck the driveability while going for that peak number.
I'd like to see someone do a Camden supercharger with EFI instead of a carb. That should give a nice broad torque band. :) http://www.camdensuperchargers.com/index.php?pag=403
Boost, cause there's not a chocolate bar named after n/a....
Hal wrote: I like the torque curves you get from positive displacement. This my Focus, 2.0L 4 cylinder with an M62 supercharger.
I wish setups like this were more common. Personally I would like to see a supercharged setup on a RB20DE or RB25 but nobody does that because the cars are stock turbocharged. I bet it would be great with a supercharger
Knurled wrote:Keith Tanner wrote: You've got 400 ft/lb or more from 3000-8000 rpm? That's impressive. Got any charts?No, it's more like 170 or so ft-lb. I'm not all that interested in how much torque, just how broad the expanse is. It's already too much torque for the traction available, but having a broad expanse is critical for being able to drive the car instead of constantly screwing around shifting. As a bonus, when the fuel pump starts crapping out because it's overheating and also sucking air, it doesn't kill the engine when it runs dead lean at peak power and the driver keeps his foot in it because lifting is what people who aren't fast do
So that powerband I posted is peaky and narrow? As someone who's actually driven the car, I respectfully disagree. Very little screwing around with shifting, note my reference to Laguna Seca in one gear.
If you don't have enough traction to handle 170 tq, you need to spend more time on the chassis!
I'm pretty sure that 170tq is being used on dirt at sub 60mph speeds through substantially narrow rally tires.
I found more grip by going from 205/215 width tires to 185s, to boot. But still, on anything but a perfectly cleaned off surface, the useful gears just blow the tires away even at the end of the straights, so that meets the objective criteria for "enough"
I've driven both. My Toyota Tacoma had a screw-type supercharger on it and frankly it was great - for a truck. However, it was something of a letdown above 5000 rpm, but that's to be expected.
Regarding turbos, they've gotten a bad name mostly because people put huge ones on their car and show dyno curves where nothing happens until 5000 rpm, then power doubles from 400 hp to 800 hp in 1000 rpm. Not my idea of controllable fun.
However, size the turbo properly and suddenly it's a very usable powerplant. I wanted something that was spun up by 3000 rpm and that continued making that power all the way to redline, and I have that now on Midlana.
The talk about the engine "being dead below 3000 rpm" on a turbo is misleading. That is, the turbo may not be spun up at low rpm, which means that the effectively normally aspirated engine is making exactly the same amount of power it would hae without the turbo. It's a power adder not subractor. If there was no turbo, for some reason people don't complain when that same engine isn't an animal below 3000 rpm.
kb58 wrote: The talk about the engine "being dead below 3000 rpm" on a turbo is misleading. That is, the turbo may not be spun up at low rpm, which means that the effectively normally aspirated engine is making exactly the same amount of power it would hae without the turbo. It's a power *adder* not subractor. If there was no turbo, for some reason people don't complain when that same engine isn't an animal below 3000 rpm.
This is very true, and something that bugs me, namely people saying a turbo is "unstreetable" because it doesn't build boost at low RPM. Boo fricking hoo, your 13B doesn't build boost until 4000rpm. Mazda made 12As and 13Bs for decades before your funds dumpster without any turbo at all and they were perfectly streetable.
I want to size the turbo for my VW monstrosity so that it does not build boost at all at low RPM. Why should it? For close to 100,000mi I have driven the chassis with a smaller engine with probably less compression and it was perfectly acceptable to drive naturally aspirated. Why would I need to build boost at low RPM? Heck, the way it is geared, it cruises at 4000rpm and if you shift it at 5500 then the revs never drop below 4k either, so what is the point of making boost that low? It is AWD so it is not something traction limited where you need lots of powerband anyway, so a 4500-7000rpm powerband is perfectly acceptable. And a bigger turbo means less exhaust manifold pressure means less detonation means more happy on pump gas. It's not going to be used for motorsport, so throttle response is not critical, and a good measure of "where's the power? oh THERE it is!" is a bit enjoyable in a street driven vehicle.
400#/ft or 170#/ft.... in reality it isn't either that makes it to the ground... why? Because we are forgetting gearing, and the mechanical advantage (torque multiplier) that the transmission, and final drive produce.
As to 170#/ft causing loss of traction, and therefore further chassis development, again it really isn't 170#/ft, but more like 1000#/ft(assuming 1st gear and a moderately low final drive) once all the advantages of gearing has occurred.
I spent most of my effort on the first Targa Miata build on the chassis instead of the engine to ensure I could use the torque I had. The engine was built to be good enough, then it was considered a done deal as I kept working on the suspension. When the big engine went in, I was able to take advantage of the torque. Not on dirt, but in the rain at least.
That 430+ hp Miata at the top of the page (the turbo one) is Jekyll and Hyde. Around town, it's a poossycat. Then you get the revs up and it goes completely bonkers. Personally, not my thing. But it's great juvenile fun because it's so dramatic. It feels fast.
Toyman01 wrote: In reply to Knurled: Yes, driving through town at 4000 rpms just so you have enough power to merge into traffic sucks.
I have to say... i've driven some pretty slow cars in my time, but i don't think i've ever driven one that actually needs to be revved like that to merge with traffic. Got any examples?
I want a positive displacement screw supercharger on my protege5.
This thread makes me want to boost everything I own. Thanks.
If turbo lag is causing a handling problem you have one or more of:
Swank Force One wrote: I have to say... i've driven some pretty slow cars in my time, but i don't think i've ever driven one that actually needs to be revved like that to merge with traffic. Got any examples?
Worn out 8.5:1 engine dragging a cylinder because the fuel distributor isn't sending anything to cyl #4, top speed maybe 80mph if the road isn't downhill. On pretty much all Interstate on-ramps, I need to turn in at high speed and keep the throttle matted and click off upshifts at just the right time and it MIGHT be able to merge with prevailing traffic... Mind you that it is geared low enough that a full-boogie run up through the gears has 60mph halfway through fourth.
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