Rasp Question ???
Tech Resident
Joined: Jan 2006
Posts: 5,117
Likes: 3
From: Philly
go outside, stick your face by the tailpipes and let someone rev it up to 5 grand in neutral then quickly take their foot off. it won't be a smooth deceleration. it'll pop and go *BLAT BLAT BLAT BLAT BLAT BLAT*
Originally Posted by ChocoTaco369
go outside, stick your face by the tailpipes and let someone rev it up to 5 grand in neutral then quickly take their foot off. it won't be a smooth deceleration. it'll pop and go *BLAT BLAT BLAT BLAT BLAT BLAT*
Tech Resident
Joined: Jan 2006
Posts: 5,117
Likes: 3
From: Philly
Originally Posted by LSUxBlake
Again, rasp has NOTHING to do with how an exhaust sounds after you rev it. That popping you'll hear is more of a backfire than anything else. If that was rasp, the only people who would worry about it were those who sat in their driveways and revved up their cars a lot. LS1's rasp shortly after 2000rpm and hold it for about 500rpm. This is the rasp 99% of the people on this board are referring to.
who said anything about backfiring? it's not backfiring! it's popping due to unequal firing order in the motor and an uneven length y-pipe. that's the definition of rasp that i've ALWAYS heard and used on boards i've been on (i.e. not just on LS1tech). it's the gurgling in the exhaust. it's not a backfire. it's not tuning issues. when you rev your exhaust in neutral and it gurgles when the rpm's go down, THAT IS RASP. that is the universal definition on boards i've been on.
rasp has everything to do with how your exhaust sounds when you rev it. if it gurgles, it's rasping.
Originally Posted by LSUxBlake
Yes, its a splatty sound that occurs in the RPM range I listed. Drone is a totally different animal. Here's a vid clip where I intentionally made the car rasp. It happens in the very first part of the clip when I'm in second gear, you can clearly hear the exhaust rasping during that rpm range while I accel. Granted it's very toned down on this video due to the nature of the exhaust, but it can still be easily heard. It's an 11mb video, so not 56k friendly. Of course the best way to hear rasp is to just watch someone drive away with LT/ORY/Borla.
http://www.lsuxblake.com/Trans%20Am/SLPDD.wmv
http://www.lsuxblake.com/Trans%20Am/SLPDD.wmv
Originally Posted by LSUxBlake
Again, rasp has NOTHING to do with how an exhaust sounds after you rev it. That popping you'll hear is more of a backfire than anything else. If that was rasp, the only people who would worry about it were those who sat in their driveways and revved up their cars a lot. LS1's rasp shortly after 2000rpm and hold it for about 500rpm. This is the rasp 99% of the people on this board are referring to.
TECH Fanatic
Joined: Nov 2003
Posts: 1,241
Likes: 0
From: MD
Rasp is the sound made around 2000 rpm not when the exhaust depressurizes and and goes bla aaaaaaaaaaaaaaah. That is not rasp. That is the exhaust depressurizing. With a high flow exhaust you are going to get that.
As for cats. A good tune and a good merge and exhaust and you don't need them.
As for cats. A good tune and a good merge and exhaust and you don't need them.
Tech Resident
Joined: Jan 2006
Posts: 5,117
Likes: 3
From: Philly
Originally Posted by Dal1as
Rasp is the sound made around 2000 rpm not when the exhaust depressurizes and and goes bla aaaaaaaaaaaaaaah. That is not rasp. That is the exhaust depressurizing. With a high flow exhaust you are going to get that.
As for cats. A good tune and a good merge and exhaust and you don't need them.
As for cats. A good tune and a good merge and exhaust and you don't need them.
rasp has more than one definition. that is the problem.
TECH Fanatic
Joined: Nov 2003
Posts: 1,241
Likes: 0
From: MD
Originally Posted by ChocoTaco369
that is the definition of rasp that i have heard on numerous boards including LS1tech. look up rasp. cars that go blat blat blat are regarded as raspy. that's why V6's are considered raspy. they all go blat blat.
rasp has more than one definition. that is the problem.
rasp has more than one definition. that is the problem.
Tech Resident
Joined: Jan 2006
Posts: 5,117
Likes: 3
From: Philly
Originally Posted by Dal1as
The problem with that reasoning is that true duels, which do not have rasp, have the blaaaaaah sound when the revs come down from accellerating. It is the depressurization of the exhaust. Rasp is the blat blat blat sound around 2000 rpm.
the BLAT BLAT is caused by the firing order/uneven exhaust tubing lengths, that i'm pretty sure are the overwhelming causes. as for that tinny sound, god i have no clue what that is caused by, it's just the LS1, but i'm clueless to the part. all i know is, my dual/dual has no tinny sound rasp to it. it does BLAT a little if i rev it high in neutral and when i go WOT and it shifts, but other than that it's great. i'm on stock manifolds though. i'm sure headers will cure most of the BLAT. it's so minor i don't even care.
TECH Senior Member
iTrader: (1)
Joined: Apr 2005
Posts: 8,807
Likes: 0
From: Vancouver,[KITSILANO].B.C. Canada *WestCoast*
Originally Posted by ChocoTaco369
who said anything about backfiring? it's not backfiring! it's popping due to unequal firing order in the motor and an uneven length y-pipe. that's the definition of rasp that i've ALWAYS heard and used on boards i've been on (i.e. not just on LS1tech). it's the gurgling in the exhaust. it's not a backfire. it's not tuning issues. when you rev your exhaust in neutral and it gurgles when the rpm's go down, THAT IS RASP. that is the universal definition on boards i've been on.
rasp has everything to do with how your exhaust sounds when you rev it. if it gurgles, it's rasping.
rasp has everything to do with how your exhaust sounds when you rev it. if it gurgles, it's rasping.
Staging Lane
Joined: Apr 2006
Posts: 57
Likes: 4
From: Space Coast, FL
I agree with the rasp definition being on the accel a little after 2000 rpms...
BLAT BLAT is most definitely the unequal pressures coming out with very little backpressure (as most ORY/LT/catback cars have) to hold them back and squish them together....has a little to do with the unequal length pipes, but its more a symptom of low backpressure...which is precisely why cats or an extra bullet muffler in the Ipipe reduces it...increase in overall backpressure....
Just about any motor with headers and minimally restricive exhaust can BLAT BLAT....even ricers....put old fashion glasspacks or cherry bombs on any carbureated V8 and you will hear it Blat Blat...but rasp (I'm pretty sure anyway), as someone mentioned before, is a byproduct of Y-pipes and the way the gases mix in the Y...thats why the true dual guys have less issues with it....
Just my .02...
BLAT BLAT is most definitely the unequal pressures coming out with very little backpressure (as most ORY/LT/catback cars have) to hold them back and squish them together....has a little to do with the unequal length pipes, but its more a symptom of low backpressure...which is precisely why cats or an extra bullet muffler in the Ipipe reduces it...increase in overall backpressure....
Just about any motor with headers and minimally restricive exhaust can BLAT BLAT....even ricers....put old fashion glasspacks or cherry bombs on any carbureated V8 and you will hear it Blat Blat...but rasp (I'm pretty sure anyway), as someone mentioned before, is a byproduct of Y-pipes and the way the gases mix in the Y...thats why the true dual guys have less issues with it....
Just my .02...
Launching!
Joined: Apr 2005
Posts: 253
Likes: 0
From: Wausau, WI
Im with Choco on this. The rasp is the gurgling you hear when you rev, let off, and downshift...that gurgling or blat as choco called it is usually what people think.
Last edited by RedZoutlaw; Sep 18, 2006 at 02:03 AM.
TECH Fanatic
Joined: Nov 2003
Posts: 1,241
Likes: 0
From: MD
Originally Posted by RedZoutlaw
Im with Choco on this. The rasp is the gurgling you hear when you rev, let off, and downshift...that gurgling or blat as choco called it is usually what people think.
Then practically every car rasps then. The exhaust depressurizing and gurgling (Blaaaaah! sound) is very common with almost any free flowing exhaust. You'll hear it in Formula 1, Nascar, Cart, etc.
