Not sure if this should go here, or in general racing talk. It's not really racing related, so I'll post here.

Why is it that big old mostly American V8 engines are louder off throttle than they are actaully accelerating. I was in town the other night, and there's always cruising on weekends. A lot of the cars would accelerate, and be fairly loud, but then as soon as they'd let off the throttle, they'd get two or three times louder.

I dunno if it's high backpressure exhausts causing a lot more engine braking, or what. I'm curious.

I think its something to do with the presure from the outlet manifold,
On the throttle, and off the throttle differences, or maybe, because the car was accelerating he was in an open street, then he went into a street with houses on both sides? creating an echo which just sounded like the car volume was amplified *EI no delayed sound*

Quote from 96 GTS :

Not sure if this should go here, or in general racing talk. It's not really racing related, so I'll post here.

GTS, I think you're completely in the wrong forum altogether . You know these guy's opinions of us, our cars, and everything else. It might not be all true and folks like us on this forum get dumped into the stereotype simply from where we are, but we do.....

I'm trying to think of what you mean. Are you talking street cars or race cars? Modern American V8 or classic musclecar era? In the musclecar era, a built up V8 or stock?

I don't care what kind of super exotic car they mention, give me a 427 SuperCobraJet any day, or my ultimate dream car, the AC Cobra 427 SC.

Quote from mrodgers :

I don't care what kind of super exotic car they mention, give me a 427 SuperCobraJet any day, or my ultimate dream car, the AC Cobra 427 SC.

Not a Shelby? Talk about class the Shelby is probobly more famous over in the US

Quote from mrodgers :

I don't care what kind of super exotic car they mention, give me a 427 SuperCobraJet any day, or my ultimate dream car, the AC Cobra 427 SC.

Can't beat a classic British muscle car.

dezigned and made by a brit... very fast like an e type jaguar... but just about as safe.... :ices_rofl

Quote from mrodgers :

I'm trying to think of what you mean. Are you talking street cars or race cars? Modern American V8 or classic musclecar era? In the musclecar era, a built up V8 or stock?

Classic, like late 60's mostly, although there was a probably 96 Caprice that sounded the same way. Way built up sounding. Not all the V8s were doing it, but a good share were. I dunno how else to describe it, but like, as soon as they'd let off to shift, the car was like 5 times louder.

Quote from theirishnoob :

dezigned and made by a brit... very fast like an e type jaguar... but just about as safe.... :ices_rofl

Mate, the AC cobra was waaaay faster than the e-type jag. The cobra was/is able to do over 180mph, even faster i think.
And shelby/AC made another model, but a racing one (name??) which went over 200mph. o.O

Quote from Nathan_French_14 :

Mate, the AC cobra was waaaay faster than the e-type jag. The cobra was/is able to do over 180mph, even faster i think.
And shelby/AC made another model, but a racing one (name??) which went over 200mph. o.O

The Shelby Cobra Daytona, and that had very little to do with AC Cars.

Quote from 96 GTS :

The Shelby Cobra Daytona, and that had very little to do with AC Cars.

could'nt remeber whether it was a shelby or AC

The original Cobra had a body based on the AC Ace (or Bristol, I've read both ways.) The Daytona had a completely new body, but the frame may have been shared. It was still part AC, but less so than the Cobra.

Take note, I did say the 427 SC, which is the brute american hunk of gigantic iron that Shelby did put into it. Yeah, the AC was british, then Shelby tore it down and rebuilt it with a monster under the hood. AC Cobra 427 SC = Shelby Cobra 427 SC. The car is still an AC, it matters not if you put AC or Shelby in there, the important part is the ground stomping 0-100-0 in 13 seconds 427 .

Remove the Shelby 427 part of it, and, yeah, you brits sure designed a cute wittle car, hehehe

Can I hazard a guess about the off-throttle sound being compression ratio? Modern cars, at least over here, are usually designed at an 8.5:1 ratio, where the musclecar era cars were 10.5:1? I don't really know what that would have to do with the sound, if anything. I'm just grasping at straws.

Pretty sure you have it backwards Mike; most modern cars use much higher compression ratios than older ones - as a generality...

Old cars used to run on leaded gasoline with much higher octane ratings than today. I don't think it was uncommon for a standard American V8 to have an 11:1 compression ratio, such as the Chevy 302 (5 liter) in the 1967 Camaro Z28. Even by today's standards, that's pretty damn high. The Honda S2000 only manages to match that number, as does the C6 Corvette, Ferrari 360, McLaren F1, etc.

Yeah I thought of the leaded gas after the fact.