Forced Induction *chat* cause we know this girl needs more power

[madfast]

Originally Posted by cobrabyte

I noticed your dyno plot is from BOE Fabrication. These guys do a great job in the Lotus supercharging world and I was wondering if you've heard from them about getting into the 86 platform.

i dunno, i just ripped this dyno off their site because they are well known for making great SC kits. i sincerely hope they see the market potential to make a kit for the FRS/BRZ. this dyno is an example of the possible gains from a PD SC. imo its not unrealistic to eventually see a FRS with a similar dyno plot. 300+ whp with a flat tq curve? imo that's ideal for this car...

[AVOturboworld]

Originally Posted by mike2100

So with all that said let's talk forced induction on a road course.
Ignoring natural aspiration, what's the best? I'm limited to my experience with N/A cars at the track and to my research into forced induction. I get the feeling that centrifugal supercharging is the best.
I get that feeling because it seems that careful throttle modulation will be easier than with a twin-screw or a turbo, and therefore dancing on the edge of the friction circle will be easier.

At what level of racing?

In N/A form, the car is great at the track because you can drive it at 110% and have very little chance of losing control in a bad way. Even if you overcook it, you can recover it easily. The problem is, that's because it's still not going that fast.

When you hop up to the 230-350whp levels, the "going fast" part changes dramatically. Terminal velocity has gone up, and corner entries start looking like a movie suddenly going fast forward. With sticky tires on, you are braking hard in a straight line, easing into the corner, "modulating" the throttle/brake for a few split seconds, then flicking the throttle light switch to On and holding on for dear life till the next corner.

Now, that mid-corner feel in the 3-4 setups will change according to what rpm you are at. In n/a, you'll be keeping it as high an rpm as possible because, well, it has very little torque. In S/C form, it'll be somewhat the same deal because the boost available will be at the higher rpm's. With the turbo, if set up well it has a beefier mid-range as well as top end. You'd still be working with the top-end in the corner, though, for max shot out of the hole.

Basically, you end up with somewhat the same technique, and in all scenario's you are using the best part of the power band possible. Net result being that the only clear winner on a race course will be the one that makes the most power.

The entire "throttle modulation" part is overblown, IMHO, because if you are sitting in the middle of your power band, a well tuned turbo isn't going to be "spiking" boost. Unless you are shifting mid-corner, which is generally not a good idea with any of the setups.

All that said, I wager if you had 3 professional drivers drive 3 different FR-S, all with roughly 250whp in n/a, turbocharged, and supercharged format, they'd end up roughly with the same times give or take a few milliseconds.

[RedLeader]

I think, from research I've done on different types of FI, a PD SC will keep nearly the same power and torque curve of the original engine, but just slide it up the graph a bit. A turbo will probably make more power in the end.

This may be the wrong place to say this, but part of me would love to see a high revving (8-9K RPM), high output NA motor. This car is built for the high revs already, I'd love to see someone go S2000 on it and push close to a 10K redline. That being said, I'm hoping the Innovate kit produces good results. Maybe in a few years when the aftermarket has had time to mature, an effective twin screw SC will come out for an affordable price. We'll have to see.

The TRD kit interests me only if they keep the factory warranty, it makes decent power, and it doesn't cost an arm and a leg.

[Siberian Husky]

I agree with most opinions offered here, but what I agree with the most is the fact that an SC would provide the type of powerband that would compliment the nature of the car the best. I am a turbo guy, always have been and always will be, but the FRS is a unique car in that its balance is paramount given other cars of the same class--we all know this. The first company to come out with a positive displacement SC application with close to 300rwhp gets my vote!

[mike2100]

Originally Posted by AVOturboworld

The entire "throttle modulation" part is overblown, IMHO, because if you are sitting in the middle of your power band, a well tuned turbo isn't going to be "spiking" boost. Unless you are shifting mid-corner, which is generally not a good idea with any of the setups.

All that said, I wager if you had 3 professional drivers drive 3 different FR-S, all with roughly 250whp in n/a, turbocharged, and supercharged format, they'd end up roughly with the same times give or take a few milliseconds.

Excellent way to put it. That leads me to another hunch I had.
Another unfortunate thing I "learned" from watching Initial D is that a turbo makes your tail wag.
Ok seriously, stop laughing. As silly as it is to base all of one's knowledge off a cartoon, the show was written with the help of some knowledgable people. Anyway, my hunch is that that turbo lag thinking is outdated (the show was written over a decade ago).
What's really unfortunate is I'm the type of person that's only going to learn the hard way. So until I drive each type I'm not really going to "know" it.

[madfast]

Originally Posted by AVOturboworld

Basically, you end up with somewhat the same technique, and in all scenario's you are using the best part of the power band possible. Net result being that the only clear winner on a race course will be the one that makes the most power.

generally speaking, the powerband of a turbo is more narrow, no?

[AVOturboworld]

Not really, no. Useable powerband of the turbo is longer than that of the superchargers. Everybody commonly says that a supercharger is always on, which is technically true, but if you look at the graphs from the perrin/vortec thread, you'll notice that the parasitic drag has negated the power gain till after 3000rpm. Then since boost builds with rpm's, it's not till peak rpm that you reach peak torque.

Contrast that with the smaller turbo build, where we reached peak boost at 3000-3800rpm (gas quality/tune/etc), and it is still holding out till redline.

At issue here is what turbo charts people commonly see on the internet. People don't brag about small turbo/daily driver tunes, they bring out their biggest peak hp builds and talk about how they made 400/500/600whp. So that leads people to believe that that is what most people do, and base their arguments against turbochargers on that.

[White Shadow]

Originally Posted by AVOturboworld

At issue here is what turbo charts people commonly see on the internet. People don't brag about small turbo/daily driver tunes, they bring out their biggest peak hp builds and talk about how they made 400/500/600whp. So that leads people to believe that that is what most people do, and base their arguments against turbochargers on that.

Yes, I've been trying to make that same point over and over again. A lot of people are quick to say that a small turbo is a waste of time/effort/money, but the truth is that smaller turbos often have excellent benefits for a street-driven car. Smaller turbos spool up fast (which reduces or can even eliminate turbo lag) and they can provide a really wide & flat torque band, starting at a very low RPM. In my opinion, that's exactly what these cars need.

Big turbos with lots of top end power are great too, but speaking from my own experience, a big turbo that makes lots of power up top is often a pig in the lower RPM range. As much as the high-RPM pull of a big turbo is satisfying, what really sucks is when the turbo doesn't even start building boost until 4000 RPM. I've seen so many cars set up that way and it doesn't make for very much fun on the street, although it can be big fun at the track where you're never really under 4000 RPM very often anyway.

[RedLeader]

Originally Posted by AVOturboworld

Not really, no. Useable powerband of the turbo is longer than that of the superchargers. Everybody commonly says that a supercharger is always on, which is technically true, but if you look at the graphs from the perrin/vortec thread, you'll notice that the parasitic drag has negated the power gain till after 3000rpm. Then since boost builds with rpm's, it's not till peak rpm that you reach peak torque.

I can see this being true of a centrifugal SC, but what about a positive displacement SC? Wouldn't that be closer to an "always on" power increase that people are looking for? Also, why not do a twin turbo/bi-turbo set-up, assuming there was room?

[FreshFRS]

Originally Posted by cobrabyte

I noticed your dyno plot is from BOE Fabrication. These guys do a great job in the Lotus supercharging world and I was wondering if you've heard from them about getting into the 86 platform.

TVS 1320 if im not mistaken. this is similar to what i would like to do.

[FreshFRS]

Originally Posted by RedLeader

I can see this being true of a centrifugal SC, but what about a positive displacement SC? Wouldn't that be closer to an "always on" power increase that people are looking for? Also, why not do a twin turbo/bi-turbo set-up, assuming there was room?

twin turbos would be expensive and a lot heavier than a single turbo. positive displacement chargers have by-pass valves to re-direct air (in most cases Roots and TVS) to reduce drag on the rotors and allow them to spin freely eating only a fraction of a HP under low load/ no load situations. it does create boost instantly once load is applied and tend to have much more area under the curve as compared to a centrifugal. and even have a little more power(and better response) over turbos in the lower ranges 2k-4k rpm

[Jeff86]

Damnit... every time I start leaning more towards a particular kit, something happens that starts to change my mind again.

AVO has certainly improved upon the exhaust note of this car.

[Sportsguy83]

AVO has so much going for them, innovative oil pump, turbo placement, OEM look, UEL headers.... I can't justify going with anyone else based on how much things I WANT they offer. Every other kit has something that I don't want/like.

[Silverpike]

Originally Posted by mike2100

So with all that said let's talk forced induction on a road course.
Ignoring natural aspiration, what's the best? I'm limited to my experience with N/A cars at the track and to my research into forced induction. I get the feeling that centrifugal supercharging is the best.

The answer to this is actually easier than you think.

The correct answer for track racing is whatever system is available which has the best heat management and reliability. Track racing places the engine under prolonged loads, and most street variety aftermarket kits tend to fall down under these conditions. Crappy hoses break, bad couplings come off, turbo bearings cook, and the water temp. will go very high if you choose a crappy setup.

Each car should be considered on a separate basis. Positive displacement superchargers are generally at a disadvantage here, because they don't usually allow for intercooling. Intercooling is a must for track racing. Strapping any decent boost supercharger and running it full throttle without an intercooler for hours at a time will both make detonation a huge problem as well as overload your cooling system. Any system that can be intercooled should be preferred, either centrifugal supercharger or turbo.

Oil cooling is also a priority for turbos and centrifugal compressors. Oil cooling should use high quality oil lines, fittings, and filters. Intercoolers should be mounted for best aero effect, and should have screens to protect the front face. Air/water intercoolers should be avoided, because the water will reach high temperatures quickly under load, and without enough radiator surface area will not be able to scrub off the heat faster than heat is being added by the intake air. Air/water systems tend to work well on the street, since the high intake air temps last for only short bursts of time. On track it's quite the opposite.

The BRZ is so new that I don't know which of the available kits would have the best reliability. I see some that should do very well, but I have no direct experience with them so I won't make any judgements here.