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Fresh Pond

Some CNG Questions...

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I'm a big CNG fan and there's some questions that I always wondered...

 

1. How does a CNG engine work compared to a diesdel engine? (DD50 vs. DD50G, etc...)

 

2. In the Orion Vs, what causes them to ring like that? My friend told me it had something to do with the wastegate being open (or some s**t like that...yes, he actually said the last part lol)

 

3. What causes them (all CNG buses) to do that choo-choo-choo sound every time the driver lets off the throttle?

 

That's basically it, please & thanks

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I'm a big CNG fan and there's some questions that I always wondered...

 

1. How does a CNG engine work compared to a diesdel engine? (DD50 vs. DD50G, etc...)

 

2. In the Orion Vs, what causes them to ring like that? My friend told me it had something to do with the wastegate being open (or some s**t like that...yes, he actually said the last part lol)

 

3. What causes them (all CNG buses) to do that choo-choo-choo sound every time the driver lets off the throttle?

 

That's basically it, please & thanks

1. So am I a huge CNG fan (mostly Orion VII), but I don't know that response

2. On the Orion V it's the way that the engine and it's counterparts are placed, don't know much about it to say though

3. I guess it has to do with the CNG and the pressure of the air itself. Depending on the air pressure that is put on the Engine, it will make the noises

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A CNG engine compresses Natural gas into a stronger bust of energy from the gas and it lets off some air that why they backfire. If you notice, the C40s dont do it as bad as the Orions. It depends on how much air is realeased after compression of gas. If the driver lets go at 25 mph, you just get a soft choooooo. 45, and you got a violent chuggg chugg chuggg. If mishandled, that air can combust, thats why, while it sounds great, backfireing is actually a bad thing. .

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Oh God I hate these buses but the Choo choo choo sound is sick when you keep doing it (Pedal on&off) I could make her whistle I swear.

C40's also make a very low choo choo sound I've noticed but I'm waiting for these buses to get louder or I'm hoping to hear from any source that A C40 sounds loud .

 

When the retarder kicks in along with a good let off from the pedal ,You will be pleased:)

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I'm a big CNG fan and there's some questions that I always wondered...

 

1. How does a CNG engine work compared to a diesdel engine? (DD50 vs. DD50G, etc...)

 

2. In the Orion Vs, what causes them to ring like that? My friend told me it had something to do with the wastegate being open (or some s**t like that...yes, he actually said the last part lol)

 

3. What causes them (all CNG buses) to do that choo-choo-choo sound every time the driver lets off the throttle?

 

That's basically it, please & thanks

 

#1. CNG engine works just like a diesel engine. The just change the injectors and swap out the braided fuel lines for hard gas lines (I'm not %100 sure on the lines so don't quote me on it)

 

#2. You wouldn't hear the wastegate as it opens and closes. Most likely the ringing sound is just the boost building up. Once again I'm not %100 on that b/c I haven't been on an O5 CNG for a while and i can't hear what you are hearing as you ride.

 

#3. The "choo choo choo" sound I do remember and that is actually my favorite part about that bus. The is the blow-off valve letting off excess boost pressure as the driver take his/ her foot off the pedal and the throttle closes...that sound brings back a lot of memories.

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Skip to 0:24...

 

 

 

^Video belongs to RTS CNG Command, who goes by darkqiviut on YT...

 

I'm not 100% sure on this, but I'm pretty sure the sound you hear from the engine is actually dependent on the exhaust setup... with the Subaru in MHV's clip, I heard the engine's firing order is what is responsible for the Boxer engine's distinct exhaust note.

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too bad CNG is hard to come by here..i'd definitely go and buy a CNG car lmao

 

I dont think CNG cars make the sound effects you love :o

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The D60s do almost the same exact same ringing noise, just a little quieter. Lots of DD50s make that sound.

 

 

 

So it is a blow-off valve, okay. I always hear that noise and think of some import car with a loud turbo BOV. That noise happens on NGs and LFSAs too as well, I assume those all have the same type of BOV with the turbos?

 

 

It's louder on the O5's because it uses the older style muffler for it. The newer buses have a different muffler for the BOV. Some have even switched to a diverter valve that recirculates the boost pressure into the intake manifold instead of letting it off into the atmosphere like most turbo charged german cars

Skip to 0:24...

 

 

 

^Video belongs to RTS CNG Command, who goes by darkqiviut on YT...

 

I'm not 100% sure on this, but I'm pretty sure the sound you hear from the engine is actually dependent on the exhaust setup... with the Subaru in MHV's clip, I heard the engine's firing order is what is responsible for the Boxer engine's distinct exhaust note.

you might be listening for the wrong noise. the blow off valve sounds like an air brake equipped bus when you apply the parking brake.

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CNG cars just act like diesel cars. What you want is a car with a turbocharger, and a non-muffled blow off valve.

 

Yes like this...

 

 

 

Also why does some Orion V CNG blow off valve sound like this v

 

 

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Another good example below of an interior recording

 

(Courtesy of myself)

 

 

 

And an example of a "newer-style" muffler CNG

 

 

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I think the (MTA) tries to keep their fleet as varied as possible, and not limit to one suggestion. We do have a lot of CNG, diesel and hybrid buses currently in service around the city if you think about it. CNG, I think, are the cheaper kinds of buses of the three, then diesel and then hybrid, according to an ad I got from Orion. Correct me if I'm wrong.

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LA's NABI 60-BRTs have the best backfire: (And the one in this vid wasn't that loud as compared to how loud I've heard them.)

 

Note: Not my vids.

 

 

The DD Series 50 CNGs on the NABI 40 LFWs are just beast. Here's a vid of a Riverside Transit Agency 40 LFW:

 

 

That backfire is music to my ears.

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While I'm at it, I never could tell when the bus was in lockup and when it was actually upshifting. I always heard a whirring under the actual engine, and that the engine would sort of stay at whatever RPM while the whirring died down. I haven't been on an Orion V in almost a month, I can't remember.

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LA's NABI 60-BRTs have the best backfire: (And the one in this vid wasn't that loud as compared to how loud I've heard them.)

 

 

The DD Series 50 CNGs on the NABI 40 LFWs are just beast. Here's a vid of a Riverside Transit Agency 40 LFW:

 

 

That backfire is music to my ears.

 

wow the dd series sounds exactly like the orion Vs

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THIS is an actual backfire... What you normally hear when the driver lets off the gas is the turbo boost release

 

 

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