It's not like I don't appreciate 370 hp. But the best thing about this turbocharged engine is the fact that it whistles like a tea kettle.
The setup that AMS Performance has developed for the Evo GSR's TD05H-152G6-12T Mitsubishi turbocharger has a smooth-bore intake duct the size of a sewer pipe. It's unencumbered by all the cleverly shaped devices that car manufacturers use to reduce intake noise, so every time you breathe the throttle, the compressor bypass valve blows off and you can hear the rush of air through the ventilation ducts in the GSR's dash.
As Engineering Editor Jay Kavanagh explains to me, the compressor bypass valve (it's not the wastegate, which is the relief valve for the exhaust turbine) minimizes the damaging effects of compressor surge when the throttle is closed abruptly.
Actually this Mitsubishi 4B11 T/C doesn't exactly whistle, at least not like the 1978 Saab 99 Turbo, the car that popularized turbochargers in performance cars in those dark days just after the first fuel crisis. Instead the GSR just breathes heavy. But like the Saab, the Mitsubishi's tea kettle thing gives it a distinctive personality.
Sure, this engine's 370 hp makes the Evo feel like it's going to jump out of its skin. But it's the sound that gives the horsepower an extra dimension of excitement.
This Evo reminds us all that it's not the volume of engine noise that counts, it's the quality
Michael Jordan, Executive Editor, Inside Line @ 15,550 miles
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Finally! Someone that understands!
"As Engineering Editor Jay Kavanagh explains to me, the compressor bypass valve (it's not the wastegate, which is the relief valve for the exhaust turbine) minimizes the damaging effects of compressor surge when the throttle is closed abruptly."
That's true, and the blow-off valve also minimizes the slow down of the compressor wheel when lifting off the throttle between shifts, which helps the turbo get back into boost quicker upon completion of the shift.
But the #1 reason kids install blow-off valves on these cars is because they think it sounds cool. They won't admit that, but that is the #1 reason.
"Actually this Mitsubishi 4B11 T/C doesn't exactly whistle, at least not like the 1978 Saab 99 Turbo, the car that popularized turbochargers in performance cars in those dark days just after the first fuel crisis. "
That Saab did sound nice, but the best turbo whistle I've heard has to go to the 1983-1984 Thunderbird Turbo Coupe, with it's Garrett T-3 turbo. That car's turbo had a really nice loud whistle as it spooled up and down. It really sounded cool.
They changed something in 1985 and later though, as those cars didn't have that whistle at all.
My car doesn't have a turbo so it doesn't whistle, but I just installed a CAI and exhaust, don't think I've gained much horsepower, but the sound it makes now makes it worth it.
@stingray,
Most of my friends with SRT-4's decided to get the Mopar Rice Plate (http://www.calibermotorsports.com/Mopar%20BOV%20Adapter.jpg) for the sound. It was pretty cheap, but it showed that Dodge had their audience pretty well figured out.
I was sad a few weeks ago when someone in an STI accused my SRT-4 of having the insert when I have an HKS SSQV for my 57 trim turbo.
Stingray - The 88 turbo coupe I owned sounded like a police siren when it spooled (I had a manual boost controller set to 17 PSI which would come on around 3000 rpms IIRC). I still remember looking in my rear-view mirror all-too-often.
It's funny, my 08 Legacy GT has/had a way too quiet engine. No real turbo noises unless you are hammering on it, and a dead-silent exhaust note. Shame, cause the boxer engine is not exactly glorious sounding without a good exhaust note or turbo noise.
Anyway, I replaced the stock air filter with an aftermarket dry panel filter. Literally, that's the only modification.
All the sudden I can hear the whooshing, spooling, and by-pass valve. Whish, whoosh, Squish. Etc. :)
Still doesn't sound great, but at least it's interesting now. Next up: Hogzaust. (Don't ask).
Joe
P.s. I intend to add an external wastegate to my car, which should reduce back-pressure and extend turbo life.
Joe, an external gate will do neither of those things. To reduce backpressure your best bet is a less restrictive exhaust.
A larger gate only allows you to divert more exhaust flow away from the turbine, which you'd only do if you wanted less boost than you have right now.
joefrompa - the whistle I was referring to in the '83-'84 turbo coupes was at low boost, like when just spooling up from idle to about 2 psi. That was when the whistle was the loudest, and it was definitely the compressor side that was whistling away, and it was more like a high pitched howl.
Under full boost, most of that whistle was gone, replaced by a quieter turbine whistle through the exhaust, and a WOOOSSSSHHHHHHH sound from the compressor side. That sounded cool too. :)
My car didn't have a boost gauge, just a Turbo LED light, and an overboost LED light, but you almost didn't need a boost gauge - you could approximate how much boost the turbo was making just from the sound of it.
Will be interesting to see how / if "chipping" is the next step.
I ran an '84 Turbo Coupe as my work beater for about three years. Cheap fun.
Back when I had my '97 Accord, the first thing I did was the CAI. In addition to the noticable increase in hp, the engine response was so much better. That was the biggest gain.
I loved the sound of my 1990 Saab 900 SPG's engine. It made this lovely gurgling sound, with the low boost spool for around town. It might have been the coolest car I'll ever own. My current 1996 Saab sounds similar to the old 900, but to a lesser extent. It still gurgles, but the turbo noise is gone! How sad!