Need some input - changed exhaust -awful sound
07-03-2005, 02:09 PM
#31
Hi wally! 
Thanx for the warm reception.
I finally decided to gas my shark, and it seems at least one of the fellas here has some experience with n2o, so i figured it'd be best to get some direction before i go and do something stupid...
Nice board they got here, nowhere near as 'snooty' as rumored.
Thanx for the warm reception.
I finally decided to gas my shark, and it seems at least one of the fellas here has some experience with n2o, so i figured it'd be best to get some direction before i go and do something stupid...
Nice board they got here, nowhere near as 'snooty' as rumored.
07-03-2005, 04:28 PM
#33
I'm in philly. My car is a 1983 US 928S A/T, which i've owned for about 3 years(my first porsche, i was always a GM muscle car guy before).
Best recorded 1/4 mile: 13.67@103.1(no, not stock, lol).
0-60(Gtech pro): 5.8 seconds
Best recorded 1/4 mile: 13.67@103.1(no, not stock, lol).
0-60(Gtech pro): 5.8 seconds
07-03-2005, 07:46 PM
#35
Three Wheelin'
Join Date: Nov 2004
Location: Gatineau/Ottawa Canada 84 928S triple black
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Originally Posted by bcdavis
I wonder it a couple of those inline bullet versions, right after the cats, might work some magic?
07-03-2005, 08:37 PM
#36
Drifting
Join Date: Jul 2002
Location: Los Angeles, CA
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I could see that happening...
Especially with mosture in the exhaust, heat, rust, etc...
If you used the tailpipe version, at least you could test it and lubricate it from time to time...
Especially with mosture in the exhaust, heat, rust, etc...
If you used the tailpipe version, at least you could test it and lubricate it from time to time...
07-04-2005, 03:50 AM
#37
"Sniper:
Good to see you here from Phil's board. There are lot of experience here and it only rarely gets nasty."
Bill, thanx for the kind greeting bro, you fellas are making me feel right at home here.
Good to see you here from Phil's board. There are lot of experience here and it only rarely gets nasty."
Bill, thanx for the kind greeting bro, you fellas are making me feel right at home here.
07-04-2005, 03:33 PM
#39
Inventor
Rennlist Member
Rennlist Member
Without an external control (like a vacuum solenoid), I think this will clatter at low engine speeds, like a weighted cap on a bulldozer exhaust. At least, that's what happened when I made something similar. Exhaust pressure builds up and burps past the valve, then closes.
Even though I took off the clatter valve, was a good excercise for me to see how much the exhaust flow is pulsed, and not a continuous flow, as I generally pictured it.
A way to get more backpressure at low rpm, to get more torque, but once the exhaust really
starts to flow, the valve opens up...
The valve may be good for low speed noise reduction. To improve flow for better extraction, what would be ideal would be a variable diameter pipe, or several pipes with different ID's, and valves to select the size for optimum gas velelocity.
I was considering oval pipes with a moveable section inside to vary the ID of the whole pipe.
What you don't want, it seems, is any thin flat areas in the pipe, which cause resonance. A hollow cat is a great resonance transmitter. Squarish mufflers are usually very thick walled to combat this.
Even though I took off the clatter valve, was a good excercise for me to see how much the exhaust flow is pulsed, and not a continuous flow, as I generally pictured it.
Originally Posted by bcdavis
A way to get more backpressure at low rpm, to get more torque, but once the exhaust really
starts to flow, the valve opens up...
I was considering oval pipes with a moveable section inside to vary the ID of the whole pipe.
What you don't want, it seems, is any thin flat areas in the pipe, which cause resonance. A hollow cat is a great resonance transmitter. Squarish mufflers are usually very thick walled to combat this.
07-04-2005, 10:15 PM
#40
928Fan4Life: "What kinda setup do you have on your car to get that 0-60 time? If you have lightened the car, what did you take of to make it not so heavy?"
Items removed:
Entire OEM exhaust(which is very heavy) replaced with a 928Specialists test pipe, single 3" borla XR-1 and single 3" straight pipe.
Yanked AC system(hot weather doesn't bother me much).
Yanked Spare, jack, toolkit(carry a AAA card, much lighter, lol)
Removed Air pump assy
Removed OEM leather power seats and replaced with 19lb contoured cloth driving seats.
42lb factory battery replaced with a 14lb Drycell
Removed front grill
Removed stock clutch and electric fans and replaced with a high output electric pusher.
Removed belly pan
Removed all kinds of extraneous brackets and bolts from undercarriage(about 15lbs worth probably)
Yanked factory amp.
I'm sure i'm forgetting a few things. I've taken off a lot of little stuff in the three years i've owned the car.
At any rate, it's a bit more than 300lbs in total.
The car was already much faster then stock when i got it, and i never met the original owner(i'm only the 2d owner, but i bought it at auction), so i honestly have no idea what's been done to the motor. It did come with a beautiful hand built 3 core aluminum radiator though, and one does not normally add that sort of thing unless they've done the motor work to justify it.
Since i bought it i installed 3" smoothwalled intake runners, adj pressure regulator, bumped the timing way up(which seemed to produce what i can only describe as a 'massive' increase in power), removed 3 belt driven accesories(which makes a significant HP difference at high RPM), and added what is in effect a straight-up racing ehxuast(the borla XR-1 is designed to help race cars meet track Db restrictions, and is in no way intended for the street...hence my selecting it, lol), and went with lower/wider tires.
My car already had the 85 up exhaust manifolds when i got it. I think i'm probably forgetting something though. I'm not much of a record keeper, and sadly my memory is not what it once was. Basicly though, beyond the weight savings, all i've done is the time-honored basic bolt on stuff.
I suspect that there's a lot more going on inside the engine than i'm privvy too, and i'm disinclined to take it apart as part of a fact finding procedure...
Here's a better close up of the motor(this is an old pic, before i pulled the A/C system):
Items removed:
Entire OEM exhaust(which is very heavy) replaced with a 928Specialists test pipe, single 3" borla XR-1 and single 3" straight pipe.
Yanked AC system(hot weather doesn't bother me much).
Yanked Spare, jack, toolkit(carry a AAA card, much lighter, lol)
Removed Air pump assy
Removed OEM leather power seats and replaced with 19lb contoured cloth driving seats.
42lb factory battery replaced with a 14lb Drycell
Removed front grill
Removed stock clutch and electric fans and replaced with a high output electric pusher.
Removed belly pan
Removed all kinds of extraneous brackets and bolts from undercarriage(about 15lbs worth probably)
Yanked factory amp.
I'm sure i'm forgetting a few things. I've taken off a lot of little stuff in the three years i've owned the car.
At any rate, it's a bit more than 300lbs in total.
The car was already much faster then stock when i got it, and i never met the original owner(i'm only the 2d owner, but i bought it at auction), so i honestly have no idea what's been done to the motor. It did come with a beautiful hand built 3 core aluminum radiator though, and one does not normally add that sort of thing unless they've done the motor work to justify it.
Since i bought it i installed 3" smoothwalled intake runners, adj pressure regulator, bumped the timing way up(which seemed to produce what i can only describe as a 'massive' increase in power), removed 3 belt driven accesories(which makes a significant HP difference at high RPM), and added what is in effect a straight-up racing ehxuast(the borla XR-1 is designed to help race cars meet track Db restrictions, and is in no way intended for the street...hence my selecting it, lol), and went with lower/wider tires.
My car already had the 85 up exhaust manifolds when i got it. I think i'm probably forgetting something though. I'm not much of a record keeper, and sadly my memory is not what it once was. Basicly though, beyond the weight savings, all i've done is the time-honored basic bolt on stuff.
I suspect that there's a lot more going on inside the engine than i'm privvy too, and i'm disinclined to take it apart as part of a fact finding procedure...
Here's a better close up of the motor(this is an old pic, before i pulled the A/C system):
