Db test on exhaust??

AZ it was not my intention to bash anybody. That's the thing about keyboard discussions. A lot is lost or inferred wrong. That's my fault with trying to get info from brain to tube. I'm glad your at a good school I think they are great for new guys that are getting into the Auto/bike repair/build industry. The best real world performance site I would suggest you check out is Speed Talk: Interviews - Racing Books - Racing Forum These are the builders and manufacturers that build engines etc from anywhere from circle track to F1. you will find out hopefully that all the theory you learn that some of it is just that.

Because an engine is dynamic that when you change one thing you may or will have to change other variables for max performance. For example: Most don't know that static compression is just a number like hp. The motor doesn't run on static compression it runs on dynamic compression. That can be changed with a cam/rocker ratio change. It starts basically when intake valve closes. That dry flow bench testing of heads is not real world compared to wet flow testing. That calculators that figure carb size for a particular engine are general and simulate VOE of that particular engine. Most of the time a larger carb is needed. That changing rocker ratios can make a cam look bigger or smaller to the engine. The most important I feel is what do you want the engine built for. Hp, pulling power, driveability, fuel mileage etc.

The only real discussion I wanted was about your statements that putting a header on a bike will not give you more power and the factory times the exhaust pulse perfectly on all engines. Making a blanket statement like that is misleading. Of coarse when you change pipes you may/will have to rejet or recarb, retune FI. That's all part of changing headers. How do you explain the difference in pipe lengths on a VFR and still say each cylinders exhaust is timed perfectly. The compromises come when having to fit the exhaust into a package within the body and the pipes are bent around bike parts. Even the front two are not bent the same.

Just one last thing. You stated: "The rest of your retort is nothing but opinion and intentional slamming using automotive analogies that don't hold water when it comes to motorcycle engine design, which if you haven't noticed is quite different from the designs and mechanics used in building car engines as you said that you have done. I would NEVER allow an auto mechanic to fix my motorcycle, just as I would NEVER allow a motorcycle mechanic to touch my car. Two different styles, two different theories."

An engine is an engine. It doesn't know that it's a car, motorcycle or what ever engine. They use the SAME theories to make the engine work. Both are air pumps, well actually heat exchangers. They use the same parts, work the same way, ingest fuel air mix, compress it, explode it and expel it. The difference is how they go about doing it for the job they are intended to do and the package design. They need all the same basic parts and theories to do that. They are not really different. The designs(packages) are different about how they do it but not the workings of what must be done to turn the wheels. That's another misconception in the real world.

 

Actually, it's pretty darn close. I tested my iPhone with that app against a calibrated Db tester at work. They displayed the same reading.

 

So what your saying is that you both like Turtles...


I actually read the whole post......yeah I was that bored....Exhaust is an interesting thing. It has been a while since I went to any automotive classes, but IIRC that the pipes were kept to the "same length" to avoid the exhaust "pulses" from hitting each other on the way out.. that would disrupt the pattern blah blah blah technical mumbo jumbo... Turtles... you both have sound theories and I think Tink is right If you guys sat down in the garage over a beer, a bike and some exhaust parts to play with you might agree on this.....

My question is SO how many DB's does a gutted can produce as compared to a stock as compared to after market? I think that was the original question.

AZ- Don't take this( personal....Internet has a way of NOT conveying attitude humor of sarcasm correctly.... Grey is The "old Crusty guy"...... I resent that usage... crotchety, cranky, crabby, yes, but Crusty no don't use that......LOL

 

So which is the loudest ??

 

^^^ Jardine's are in terms of aftermarket, at least on any VFR that I've heard. Straight pipe if crazy loud is the only goal.

 

LOL yeah, I thought about that when I typed it out, Crusty. It's a term we use in school all the way back from Theory to describe the old grumpy guy that's "been there since the shop opened and don't take shit from no rookie tech coming in out of some high trottin motorcycle school thinkin just cause he paid good money to learn him how to fix a bike that he knows more than me" kind of mechanic. I thought it was just Brian Foote's funny little sarcastic story telling, but apparently all the other instructors either knew him or his twin brothers... must have been a big litter!

Tink, your probably right. Going back and reading both our comments, we are pretty much on the same latitude of thought... and it'd probably be a long, drawn out, boring ass conversation that lasted hours... maybe even a six pack. It's being able to talk about stuff like that though that makes it totally worth the money spent to learn what I have over the last 14 months.

Oh, and Ward... I downloaded the app on my Droid and it's pretty accurate. Stock pipes on my '86 registers 83 Db from the seat at idle. Incidentally, my girlfriends ear piercing scream registered 100 Db from 3 feet away indoors. Yeah, I get that bored too, Crusty.