Thursday, January 12, 2006


Time for our quarterly commuter rant.

Listen WMATA. You do right by me, I’d say, 60% of the time. And for that I appreciate you and your lack of dedicated outside funding. But when the bus comes 3 minutes early (leaving three riders standing jaw agape a block away) and the next one doesn’t come for 30 minutes and it’s packed with the heat stuck on Gobi and I have to sit between two sweaty Pentagon schlubs (who probably weren’t supposed to be talking about their involvement in the Able Danger program so openly) while that Information Leafblower gets to sit next to the cute blond (who just started wearing an engagement ring, too bad) and the Metro platform sign (convenient) says the next Blue line train won’t come for another 27 minutes (inconvenient) and will only have four jammed cars, well, then I get a little crazy and write the Post.

But the next day it’s back to normal so all is forgotten.

What is not forgotten, though, is my little insane grudge against the WMATA for not writing me back when I had a simple question about how their buses work.

I was not a bus rider when the natural gas buses hit the street back in 2002 so I may be a little late to the game on this one. And only recently have they been added to my route. But as a frequently-occasional bike commuter, anything that lessens the amount of bus exhaust black-lunging my trips to work is appreciated. And I like the seating arrangement in the CNG over the diesel. (More “accidental” eye contact with the until-recently single, cute blond.) And the fact they run quieter is something everyone loves. Who cares if they cost more to maintain. Less exhaust means less chunks of federal buildings 'roding and falling on me.

If you’ve ridden the CNG buses, you may notice that at times they occasionally admit a sound that is relatively difficult to describe. A whooo-whooo or hoooowooo, perhaps. But no exclamation points because it’s too sad sounding. As in “I’m tired of driving around Washington Circle again, wwooo-woooo, sigh.” It’s a noise similar to the one the controls of the Death Star made when Obi-wan was balanced over the chasm and powered down the tractor beam. Or what I imagine King Hippo would sound like if he was a real person and you punched him in the stomach in a manner that would cause his pants to fall off.

I wanted to know what this sound was. So I researched natural gas engines on the web, looked at the John Deere, Bluebird, WMATA, et al. web sites to no avail. Then I did what any crackpot would do, I sent an email to Metro. And they never wrote back. I even talked to a friend who just started to working for WMATA and he told me to bugger off, they had more important things to do.

Screw you Metro, you’re not the only game in town.

So’s I looked up who sold WMATA their crappy buses for jerks. Enter the awesome Cummins Westport and Westport Innovations Inc. I wrote the wonderful people there and they wrote me a nice letter back…

Thanks for your recent inquiry to Westport about the noise pattern you are hearing on the WMATA buses you ride frequently. I work with the fine people at WMATA and, thus, have been asked to respond.

Without sitting next to you on the bus and hearing the noise, it is difficult to pinpoint what it may be. There is a lot going on in the engine compartment and the noise you hear could come from a couple of sources. I'll take a stab a what sound you may be hearing.

The C Gas Plus Cummins Westport engine installed in the buses uses what is known as a "Waste Gated" turbocharger. With this design, the turbo-charger assists the engine in getting up to speed quickly to allow the bus to accelerate but, at times, releases some of the exhaust gases through the bus exhaust system to prevent the turbocharger from going into an overspeed condition. What you may be hearing is waste gate cycling which impacts on airflow through the engine turbocharger and, in turn, bus air intake system. It makes a distinct sound and this may be what you are hearing.

It could be how the hydraulically driven radiator cooling fan cycles on and off to respond to the engine cooling system needs. The buses use a hydraulic pump to drive a remotely mounted radiator fan. There is a hydraulically driven pump mounted off the end of the air compressor that supplies the hydraulic pressure to drive this cooling fan. When the electronically controlled pump pressure modulates the fan speed, you hear the rush of air through the cooling radiator. Depending on the outside temperature and air conditioning demands, the fan may or may not be running...

As you can imagine, there are a number of different systems on a modern bus all designed to make for a quite, enjoyable ride and allow the driver to concentrate on your safety. I may or may not have hit on the exact one with the above response that creates the noise you are hearing but I'll bet I've planted a few seeds for some additional listening on your part.

Best wishes for the New Year.

David C. Super-nice-guy

Yeah. So my guess is it’s the Waste Gated turbocharger. And even if it’s not, it’s still a kick ass thing to talk about next time the bus makes that noise and people look up curiously. You can say “oh, that’s just the waste gated something or other and it blows to the turbocharger.” And that cute blond will cast of her engagement ring go home with you, happily ever after.

And if you’re ever in the market for a large bus or people mover of any kind, I can not recommend Westport enough. What a great company, doing their part the save the environment and to appease idiots like me.


The Governess said...

and to think, someone left me a comment saying looking for a trumpet was the new nadir of nerdiness. (of which to I say: zenith, compared to this.)

PS, that blonde girl knows yr hitched, dirty old man.


topic15 said...

The whistle goes woooooooo! Actually, I think the WMATA guy had it about right, it sounds like it would either be related to 1) airbrakes or 2) a blow-off valve (helps maintain even pressure on a turbo...very popular among the fast and the furious crowd as it let's out a massive Pheeeeeesh when you let off the accelerator).