Help With Sound of Fabspeed Catbypass vs X-Pipe and Other
09-30-2006, 11:54 PM
#16
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Originally Posted by 993inNC
I think my site has been altered (and not by me). All those clips sound the same all of a sudden. I really need to redo those clips.
Eccentially my pipes will accentuate sound, they are tame for cruising around town, but once you get the revs up over 4K......look out
Also, these have been described as auto art, not just a cheap bolt on. They are all hand made by a friend of mine and I and we try to make every effort to put out the best quality we possibly can. Its sort of similar to you can go buy a pair of shoes at any local shoe store or you can get a bespoke pair......and the price will be different.
Eccentially my pipes will accentuate sound, they are tame for cruising around town, but once you get the revs up over 4K......look out
Also, these have been described as auto art, not just a cheap bolt on. They are all hand made by a friend of mine and I and we try to make every effort to put out the best quality we possibly can. Its sort of similar to you can go buy a pair of shoes at any local shoe store or you can get a bespoke pair......and the price will be different.
10-01-2006, 09:40 AM
#17
Race Car
Yes but all 911's have utilized merged exhaust systems. The only difference with us is that our "merge" is not a "camber" as in with your current factory cats, but a point of merge. We have found there to be no excessive heat issues with the "X" location itself (no hotter than the point that the exchanger connects to the cat/by-pass), and should have some dyno #'s shortly via one of our own RL'ers which will hopefully prove that our "merge" is not detrimental.........and I hope to make Bill a happy customer once that happens 
10-01-2006, 12:34 PM
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It would also help for you to have sound clips (start, idle, drive-off, drive-by, etc) with various mufflers (including motorsound or stock) if you say the ones posted do not represent the actual sound or are corrupted in some way. Again, one of my other objections is the price, but I'm sure there are plenty of people willing to pay $700. Thanks.
10-01-2006, 01:00 PM
#19
Yes but all 911's have utilized merged exhaust systems
10-01-2006, 02:29 PM
#20
Race Car
Yes but we aren't talking about reason Bill, what was mentioned was whether or not the idea was appropriate or not. Cost and reason are secondary.
With no excessive heat generated by my pipes, it would stand to reason that the exhaust discharge isn't being held up or over taxed in any way as they meet at the "X".
That location also is at a bit larger diameter than the factory pipes which I'm sure aid in the flow from each side as it reaches the "X". Again hopefully soon we'll have some real numbers and the story will be told.
With no excessive heat generated by my pipes, it would stand to reason that the exhaust discharge isn't being held up or over taxed in any way as they meet at the "X".
That location also is at a bit larger diameter than the factory pipes which I'm sure aid in the flow from each side as it reaches the "X". Again hopefully soon we'll have some real numbers and the story will be told.
10-01-2006, 02:33 PM
#21
Race Car
Originally Posted by all623
It would also help for you to have sound clips (start, idle, drive-off, drive-by, etc) with various mufflers (including motorsound or stock) if you say the ones posted do not represent the actual sound or are corrupted in some way. Again, one of my other objections is the price, but I'm sure there are plenty of people willing to pay $700. Thanks.
10-01-2006, 07:58 PM
#22
Originally Posted by 993inNC
What should be there is motorsound with the X pipes, stock cats with our "Cup" style muffler. They now all seem to sound like the latter. The motorsound with X-pipes is a great oldschool 911 sound (from inside) and a nice growl (very untypical of a 6 cyl) from the outside.
They sure to look nice, though
10-01-2006, 08:21 PM
#24
Race Car
Mark, all I would have is interior track video with that setup. Unfortunatley there's also alot of wind noise as well, so not alot of representative clips. I could try and post it on Putfile. I'll have to isolate sound video and see if I can do that. I'll try this week if I get a chance.
You had me, then you lost me... What (I think) most of us want is the old-school 911 sound that is very much typical of the flat six. That was lost when the 993 came out, unfortunately. If the x-pipes are moving farther away from the flat six sound,
They sure to look nice, though
And thats part of what ya payin' for
They don't sound oldschool from outside, just inside (you'd have to be there....). Outside is 993 just at an elevated level without the resonance inside.
You had me, then you lost me... What (I think) most of us want is the old-school 911 sound that is very much typical of the flat six. That was lost when the 993 came out, unfortunately. If the x-pipes are moving farther away from the flat six sound,
They sure to look nice, though
And thats part of what ya payin' for
They don't sound oldschool from outside, just inside (you'd have to be there....). Outside is 993 just at an elevated level without the resonance inside.
10-02-2006, 09:24 AM
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I recently had the same dilema and wanted to understand the differences in sound. I fealt the Fabspeeds lost some of the 'flat 6' sound, but had a nice rasp to them.
I thought the DACH pipes were a bit pricey to get to the UK especially if I did not like the sound when I got them on. In the end I decided to modify the standard cat. Quite easy really if you cut the cat in the right place, the cat core just drops out. Weld back up and bolt back on.
The sound is vertually perfect for me. On start up and tickover it's not much louder. Drive away and give it a boot full and you get a glorious rasp outside the car. Inside you are aware it's loader and it sounds great on WOT. No resonance problems at all. Also you get the added bonus of the odd pop on the over run or as you bounce off the rev limiter.
The only downside is you use more fuel flooring it everywhere you go....
I'll be really interested in the comparative power test as the cats look very restrictive to me. I'm looking to get mine a live re-map to see if there's any 'free' power to be had.
Nick.
I thought the DACH pipes were a bit pricey to get to the UK especially if I did not like the sound when I got them on. In the end I decided to modify the standard cat. Quite easy really if you cut the cat in the right place, the cat core just drops out. Weld back up and bolt back on.
The sound is vertually perfect for me. On start up and tickover it's not much louder. Drive away and give it a boot full and you get a glorious rasp outside the car. Inside you are aware it's loader and it sounds great on WOT. No resonance problems at all. Also you get the added bonus of the odd pop on the over run or as you bounce off the rev limiter.
The only downside is you use more fuel flooring it everywhere you go....
I'll be really interested in the comparative power test as the cats look very restrictive to me. I'm looking to get mine a live re-map to see if there's any 'free' power to be had.
Nick.
10-02-2006, 09:27 AM
#27
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Originally Posted by Bill Verburg
An even fire engine does not benefit from a x-over pipe. Look at factory race headers and tail pipes, they are separate for a reason.
Do not confuse the merge design where the 2 banks are sometimes brought together in the same way that the 3 cylinders on a single bank are merged. These are what are called 180 degree headers and the pipes are cut to specific lengths and carefully merged. The resulting pipes smear out the torque curve, peak power is slightly reduced but the wider power band can be very desireable, akin to the way v-ram broadens the power band.
A x-over is only usefull on an odd firing engine such as US 90 degree V-8, they are useful there because there are always 2 cylinders on one bank that fire consecutively into the same collector. The x-over allows for smaller banks while relieveing the extra pressure on the one side.
Do not confuse the merge design where the 2 banks are sometimes brought together in the same way that the 3 cylinders on a single bank are merged. These are what are called 180 degree headers and the pipes are cut to specific lengths and carefully merged. The resulting pipes smear out the torque curve, peak power is slightly reduced but the wider power band can be very desireable, akin to the way v-ram broadens the power band.
A x-over is only usefull on an odd firing engine such as US 90 degree V-8, they are useful there because there are always 2 cylinders on one bank that fire consecutively into the same collector. The x-over allows for smaller banks while relieveing the extra pressure on the one side.
Curious since that's different information from what I have been told.
I'd like to know more why for Porsche cross over exhaust design is not desirable.
I understand 6 it different than 8 but information I have (from exhaust designer) prefers very much cross over pipe for Porsches.
Factory header designs are also confusing (to me) since the headers in Porsche race cars are not equal length design and that's not optimal either.
10-02-2006, 11:00 AM
#28
Porsche flat 6 and Ferrari 180 crank(single plane) engines are what are called even fire.
Front of car
3 6 -------------- Firing order 1,6,2,4,3,5
2 5
1 4
left ********right
collector****collector
1-2-3----------6-4-5
here is a typical factory configuration which continues to be used to this day
Notice that a cylinder firing on the left bank is always followed by a cylinder firing on the right bank, then back to the opposite bank
Ferrari 180 degree crank has a similar firing pattern.
For these engines there are several ways to configure the exhaust so as to take advantage of acoustic tuning which enhances cylinder filling and scavanging.
Method 1- most common, enhances hp & torque in a relatively narrow rev range, where power is enhanced is determined by pipe length and diameter
equal pipes of an approprite length and diameter from each bank are merged(carefully) then the exhaust is led to a muffler or atmosphere
Method 2- most complicated, smears the power band out a little more than method 1, often called a 180degree header, again the power curve is shaped by the length & diameter of the primary pipes but also by the length and diameter of the secondary pipes.
equal pipes of an appropriate length & diameter from each bank are merged(carefully) then the exhaust continues thru a secondary set of carefully designed length & diameter, eventually the secondary pipes are merged(carefully) in the same manner as the primaries.
Here is an example of a very nicely done 180degree exhaust , courtesy of Autometrics
here are parts of another, off the car
Tuned pipes rely on valve overlap so modern smog motors w/ little or no overlap don't benefit as much from exhaust tuning.
American V-8s w/ 90degree(2 plane)cranks on the other hand are odd fire engines,
Front
8 4 ----------- firing order 1-5-4-2-6-3-7-8
7 3
6 2
5 1
* typical configuration , not representative of any specific engine
there are always 2 cylinders on 1 side that fire consecuutively, dumping 2 slugs of gas into the same pipe. You could make the pipes on that side bigger to accomodate the excess gas volume but then that would interfere w/ acoustic tuning. So the solution is
solution 1
180degree exhaust pipes
left ********right
collector*****collector
5-2-3-8--------1-4-6-7
This is not the same sort of 180 exhaust described for even fire engines. In this arrangement alternate firing cylinders are dumped into a single collector, this means a left pipe has to x-over to the right collector and a right pipe has to x-over to the left collector. From there the pipes are run separately to atmosphere or muffler. This method is most commonly seen on mid engine 90 degree crank V8s, thingk Ford Gt40 w/ it's "bundle of snakes" exhaust.
solution 2
x-over connection
in this method commonly used on US hot rodded V8s/Nascar etc, there are the usual left and right equal sized collectors, again tuned by length, diameter and merge configuration. But soemewhere in the pipes, there is a x-over connection, where it is is not critical, the size and shape are not critical, the merge confiuration is not critical. It's sole purpose is as a vent for the onde side that has consecutively firing cylinders
Front of car
3 6 -------------- Firing order 1,6,2,4,3,5
2 5
1 4
left ********right
collector****collector
1-2-3----------6-4-5
here is a typical factory configuration which continues to be used to this day
Notice that a cylinder firing on the left bank is always followed by a cylinder firing on the right bank, then back to the opposite bank
Ferrari 180 degree crank has a similar firing pattern.
For these engines there are several ways to configure the exhaust so as to take advantage of acoustic tuning which enhances cylinder filling and scavanging.
Method 1- most common, enhances hp & torque in a relatively narrow rev range, where power is enhanced is determined by pipe length and diameter
equal pipes of an approprite length and diameter from each bank are merged(carefully) then the exhaust is led to a muffler or atmosphere
Method 2- most complicated, smears the power band out a little more than method 1, often called a 180degree header, again the power curve is shaped by the length & diameter of the primary pipes but also by the length and diameter of the secondary pipes.
equal pipes of an appropriate length & diameter from each bank are merged(carefully) then the exhaust continues thru a secondary set of carefully designed length & diameter, eventually the secondary pipes are merged(carefully) in the same manner as the primaries.
Here is an example of a very nicely done 180degree exhaust , courtesy of Autometrics
here are parts of another, off the car
Tuned pipes rely on valve overlap so modern smog motors w/ little or no overlap don't benefit as much from exhaust tuning.
American V-8s w/ 90degree(2 plane)cranks on the other hand are odd fire engines,
Front
8 4 ----------- firing order 1-5-4-2-6-3-7-8
7 3
6 2
5 1
* typical configuration , not representative of any specific engine
there are always 2 cylinders on 1 side that fire consecuutively, dumping 2 slugs of gas into the same pipe. You could make the pipes on that side bigger to accomodate the excess gas volume but then that would interfere w/ acoustic tuning. So the solution is
solution 1
180degree exhaust pipes
left ********right
collector*****collector
5-2-3-8--------1-4-6-7
This is not the same sort of 180 exhaust described for even fire engines. In this arrangement alternate firing cylinders are dumped into a single collector, this means a left pipe has to x-over to the right collector and a right pipe has to x-over to the left collector. From there the pipes are run separately to atmosphere or muffler. This method is most commonly seen on mid engine 90 degree crank V8s, thingk Ford Gt40 w/ it's "bundle of snakes" exhaust.
solution 2
x-over connection
in this method commonly used on US hot rodded V8s/Nascar etc, there are the usual left and right equal sized collectors, again tuned by length, diameter and merge configuration. But soemewhere in the pipes, there is a x-over connection, where it is is not critical, the size and shape are not critical, the merge confiuration is not critical. It's sole purpose is as a vent for the onde side that has consecutively firing cylinders
