turbo'd s10, big v-8
http://www.youtube.com/watch?v=pRYZrQIP1yE
shit is absolutely obnoxious

then here's some of NC's finest: Buck Spruill's 1300hp Duramax (featuring a dodge 47RE transmission, allison couldnt hang)
http://www.youtube.com/watch?v=46XP57sPJpY

quickest cummins exhaust note:
http://www.youtube.com/watch?v=mVq4FzYBrZ0










BUT THEN AS I WAS CONSTRUCTING THIS THREAD I CAME ACROSS GALE BANK'S CREATION... and have no more basis for thinking turbo gassers are louder
http://www.youtube.com/watch?v=zt7ojzhA2JM





sippin dat 190% diesel

2/4/2009 9:32:05 PM

this thread sucks


jibber jabber on, jibberdy jabberdy box

2/4/2009 9:37:44 PM

or maybe the kind of guy who is going to spend a gazillion dollars on an aftermarket turbo'd gas v8 is also going to have a loud exhaust.

2/4/2009 9:53:07 PM

but each case is running an open pipe from turbo....


I'm going to venture a guess at possibly camp profile and timing

2/4/2009 10:07:16 PM

ask zxappeal

2/4/2009 10:09:59 PM

you don't know the specs on the turbine wheels and turbine housings either.

2/4/2009 10:11:58 PM

^good call. what would you hypothesize? Larger housing=louder (assuming less sound energy is transferred to the turbine wheel with a more open housing)?

well i hope he would chime in, even though this thread is the suck. and its pretty much moot point, considering gale bank's truck


[Edited on February 4, 2009 at 10:13 PM. Reason : -]

2/4/2009 10:12:00 PM

hypothesis? I'm guessing that the level of restriction in the turbine housing (and its associated backpressure) would also have a muffling effect. How much of an effect? Quantifying that would be difficult for an internet armchair engineer. But I'd speculate that more restriction = more backpressure and more muffling to some extent. More restrictive exhausts tend to be quieter, no?

What contributes to backpressure in this case? A bunch of factors, but it's pretty much the interaction of the turbine blade size/shape, the manifold runner design and hotside inlet size (T25, T3, etc), the turbine housing A/R, and the corrected mass flow of the engine.

here's kind of an interesting read on pressure ratios in turbo diesel engines, although I can't vouch for its complete veracity: http://www.dieseltruckresource.com/dev/showthread.php?t=168543

2/4/2009 10:39:53 PM

one spins really fast; the other, not so much

2/4/2009 11:03:06 PM

Quote :

"ask zxappeal"

For the most part, the combustion event in a diesel's cylinder is over and done with when the exhaust valve opens and initial blowdown occurs. Most traditional diesels have a relatively short injection event, as fuel delivery is controlled by a cam lobe...that cam lobe might be on a sorta "swash plate" like in the Bosch VE pumps, a real camshaft inside an injector pump, such as the Bosch P pumps, inside a ring like in the Stanadyne/Roosa Master pump, or on the engine's actual camshaft (like all Detroit 2-strokes prior to DDEC and on all early Cummins engines such as the fabled NTC and KTA). The cam's duration in degrees is rather fixed, and effective duration is simply controlled by raising or lowering the pump plunger's or the injector's fuel bleedoff port. On injection event, of limited duration (pretty close to all at once).

Diesel fuel's burn rate is based on several things:
1. Dynamic compression ratio and chamber temperature (DUH)
2. Air charge velocity and the design of the swirl chamber in either the piston or the head.
3. The spray pattern and orifice sizes of the injector tips.
4. The overall injection pressure.
5. The general ignitability of the fuel (measured in effective cetane rating)
6. The rate of vaporization of the fuel droplets as combustion occurs. Fuel can only burn when vaporized and exposed to adequate oxygen. Fuel viscosity and vapor pressure contribute to this as well.
7. The total number, duration, and timing of injection events.

Now think about #7. Traditionally, diesels were limited to one injection event per power stroke...unless somebody out there came up with some elaborate scheme to run multiple injectors per cylinder and two injection pumps. Injection occurred, and initial combustion was pretty instantaneous and somewhat of a shock; hence the traditional diesel rattle and the immense size of most diesel engine wrist pins and sturdy construction of their pistons.

The fuel burn rate was primarily dominated by how fast the fuel droplets could evaporate and the flame front could propagate. Contrary to popular belief, diesel fuel is VERY ignitable; a cetane rating is almost a polar opposite of effective octane rating. Bottom line: higher octane gas resists autoignition and burns very smoothly. Diesel doesn't. By the time the diesel's piston approaches the end of its power stroke and the exhaust valve opens, combustion is pretty much done. You'll never really see a diesel with glowing exhaust ports. On the other hand, when a gasser's power stroke is done, the exhaust valve opens, blowdown occurs, and still-burning gases are leaving. There's much more of a pressure drop, and the blowdown charge leaves almost explosively, still burning. Listen to a gasser idling with open headers and no exhaust. You can hear it.

On newer diesels with common rail injection and computer controlled injection events, the ball game changes up quite a bit. Most of these engines have multiple injection events per power stroke. Some have 3, others 5, maybe more. This is done for several reasons:
1. A small pre-power injection event prior to the main one helps to alleviate the instantaneous pressure rise or spike that has traditionally occurred. Less stress, less noise.
2. Several power injection events help to control peak combustion and optimize its timing and duration to deliver maximum leverage to the crank smoothly.
3. When cylinder pressure doesn't spike as much, and remains much more controlled and constant, then gaseous dissociation is much less likely to occur. The primary target here is to minimize the formation of oxides of nitrogen.
4. Small post-power injection events help to do three things: keep the heat up a little higher and exhaust gas velocity up, which results in better turbo response AND provide fuel afterburn to help keep the catalyst lit up AND help to regenerate/clean out the diesel particulate filter in the exhaust.

Okay. I'm shutting up now.

No...no. I'm not done. On electronic engines, you can increase the post-power injection event's duration. Hell, you can remap the fuel curve entirely. Want that turbo to spin up faster (holding turbo size constant and disregarding variable nozzle turbos)? More fuel later in the game. More exhaust noise.

[Edited on February 4, 2009 at 11:07 PM. Reason : blahblahblah...shit I could hash this out for hours on end.]

2/4/2009 11:04:48 PM

thanks guys, and feel free to go on, as I actually enjoy reading such long posts/discussion. This kind of stuff is for the most part beyond my normal thought process - but knowledge is power!


ALSO, your discussion points are where i was wanting to go with this thread





[Edited on February 4, 2009 at 11:14 PM. Reason : carry on]

2/4/2009 11:11:31 PM

Yeah, knowledge is power...but let's compare it to incoherent light (such as from an incandescent bulb or maybe a fire or traditional fluorescent tubes or whatever)...versus coherent light (laser).

You can have all the wattage in the world, but if it has no focus or coherence, well it ain't gonna do much more than offer a bit of illumination over a scattered area.

Now if you focus that knowledge, if you get it all going on mostly the same wavelength, then that fucker has POWER. Enough to cut steel, etch diamond, measure distances to celestial bodies.

If I could focus my knowledge, I'd be a dangerous motherfucker. Right now, I'm not a whole lot more than a gross annoyance, kinda like the toothache I have right now.

2/4/2009 11:17:24 PM

^you do realize that, until I meet you in person, the voice in my head while reading your posts is none other than Mike Boles?





from arghx's article:

Quote :

"Higher compression ratio would increase peak combustion temps, but average operating temp of the piston will actually go down because the peak temp exists for a split second, and the temp and pressure decay faster with higher compression-- giving an overall cooler running engine. Another variable is RPM. If I take the exact same air/fuel ratio, the exact same engine timing and so forth and double the RPM, my EGTs will go up. This is simply because the TIME available to completely burn the charge is less, and you are more likely to be expelling hotter, still burning gasses. That's why an engine needs more timing advance as RPM increases, and also why a 12V can't be optimized for a very broad range. You can either set it up for higher rpm, or low rpm, or midrange, but you'll give up one to get another. These guys running 22º timing aren't blowing people away with bottom end grunt. They are screamers running 4K rpm and then some."

[Edited on February 4, 2009 at 11:26 PM. Reason : im guessing static pump timing from the p7100- zx i think you stated that to me long time ago]

[Edited on February 4, 2009 at 11:31 PM. Reason : my shit's going to be bottom-mid range, im betting. the 14&22cm turbine housings will help anyways]

2/4/2009 11:25:24 PM

Let's just say, among friends, we were to try to get this fuel to burn more evenly. You know, talking about it over drinks or good food. How do you think we could do this? What's getting in the way of that fuel just going up all at once?

BTW, Mike Boles and I got along pretty damn good. He was one of my all-time favorite professors.

[Edited on February 4, 2009 at 11:44 PM. Reason : I miss that fucker.]

2/4/2009 11:43:41 PM

the thermo guy? he talked about putting together engines in thermo class once haha.. seemed like a decently cool dude

..and he passed me in thermo so he can't be too much of an ass

2/5/2009 7:58:02 AM

He gave me an A in Thermo, so I dig.

And Corson gave me an A+ in 410, so he's like my hero.

And Gonzalez, may God rest his soul, was a wonderful prof who saw fit to actually pass me in Fluids in summer school. And he was a helluva guy to boot.

2/5/2009 8:57:48 AM

boles was great as was corson

2/5/2009 10:03:03 AM

Quote :

"A small pre-power injection event prior to the main one helps to alleviate the instantaneous pressure rise or spike that has traditionally occurred. Less stress, less noise."

the gasoline direct injected engines are doing a pre-power injection too

2/6/2009 7:39:11 PM

^^^ yeah, a lot of people had a hard time with Gonzales, but I always found him to be a really good dude.

I liked how when explaining really dry material, he'd stop and say something to the effect of "Yeah, I know that this sucks, but not many people know how to do it--so suck it up and learn it so you can buy a Porsche." Most engineering concepts ultimately boiled down to their use in terms of buying a Porsche, haha.

Quote :

"the voice in my head while reading your posts is none other than Mike Boles? "

I've known Dan for what, 7-8 years? I can tell you that he's not at all like a professor of any sort, other than maybe that M.E. professor we had who'd been an engineer for submarines. He ended up dropping dead all of a sudden. I'm drawing a blank on his name at the moment, but I can picture him clear as day.

2/7/2009 7:16:14 AM

I hope that is not an omen of sorts, Josh.

2/7/2009 11:32:10 AM

No, I'll remember your name...but might suppress the memory of the mental images.



just kidding...nah, I didn't mean it like that. I just can't think of his name and am trying to describe who it was. He only taught for a year or two.

2/7/2009 12:41:08 PM