I think I am off to a good start!
02-11-2011, 07:47 PM
#46
Burning Brakes
Bill & Vince - why did Porsche Motorsports not use a long tube design in the 993 and 997 RSR's?
I am in the process of having the headers/exhaust system of my 964 and 997 GT3RS upgraded now.
I am in the process of having the headers/exhaust system of my 964 and 997 GT3RS upgraded now.
02-11-2011, 08:13 PM
#47
Rennlist Member
I can tell you that we did engine dyno testing on a 993 Cup car with a very well known race shop and compared long tube headers (28" - 30" long) to the Porsche Motorsports header (~23" long). The long tube headers made huge gains (75 ft pounds at 4000 rpm) in the midrange, but lost 2-3 hp at maximum power. They were not interested in the gains made down low and saw the loss of power on top as an issue. They may have been happy with zoomies. For a street application, autocross etc.. I think they would be tremendous. I would like to have gotten some track testing and seen data, but we never went that far with it.
I need to see if I can dig up that data.
02-11-2011, 08:27 PM
#49
Rennlist Member
Hi guys. Excellent debate.
However the OP has dissapeared as you have stollen his thread!
I think we are discussing a subject matter akin to the opposite end of the engine (intake configuration) i.e. a subject that has its roots in physics and engineering but lives in the real world of multiple variances impossible to assimilate under contolled contitions. Application is the keyword for these types of modifications. You can build a solution which works for a given application but when you are pushing the 95th percentile the trade off is a compromise of performance for applications outside the parameters of the design brief. I think we can all agree this is why the factory stuck with 50th percentile solutions to create a rounded package that would work for a variety of customers and applications....
One thing remains constant however. I dont think any of these designs can be perfected without engine/chassis dyno or onboard fed data (think Motec M600/800). Im sure none of teh factory race header - exhaust solutions were worked out on spreadsheet without being proto built and put on the engine dyno before a jig was build to produce them in quantity. You need decent resources for that!
In any case. It seems there are a number of designs that work well for mostly race cars. Our OP has take this step with a customised set of tubes for a road car in warm climes. I think thats ballsey and merits salutation. The missing part of the equation is the Cams. I think everyone agrees that you can increase exhaust effeciency but without the ability to change the timing and get the gasses out of the cylinder its kinda a half solution. Camlob starts with a 272 bhp 243lb motor. He now has changed the headers and removed the Cat converter - once dyno tested we know the start point on whuich the Cam chage he has planned in a few weeks time will build upon. For me this next data point with an initial guestimate chip via Steve Wong or Steve Weiner is the next interesting data point. Assuming 98RON/93 MON fuel and all ancilaries (MAF, plus, Disti and timing) are in order Im betting the end result should be at least 295 bhp for 260lbft and hopefully 300 bhp for 275lbft although dynbo variances will obvious make a big difference -hence the need for a like for like data point before the work is done....
May the discussion continue. its a great place to learn this! Just a shame in some regards Porsche didnt leave much on the table with these engines. If it were Japanese we would have 20% improvement in power for less than a set of tyres and wheels :-)
Cheers
M
However the OP has dissapeared as you have stollen his thread!
I think we are discussing a subject matter akin to the opposite end of the engine (intake configuration) i.e. a subject that has its roots in physics and engineering but lives in the real world of multiple variances impossible to assimilate under contolled contitions. Application is the keyword for these types of modifications. You can build a solution which works for a given application but when you are pushing the 95th percentile the trade off is a compromise of performance for applications outside the parameters of the design brief. I think we can all agree this is why the factory stuck with 50th percentile solutions to create a rounded package that would work for a variety of customers and applications....
One thing remains constant however. I dont think any of these designs can be perfected without engine/chassis dyno or onboard fed data (think Motec M600/800). Im sure none of teh factory race header - exhaust solutions were worked out on spreadsheet without being proto built and put on the engine dyno before a jig was build to produce them in quantity. You need decent resources for that!
In any case. It seems there are a number of designs that work well for mostly race cars. Our OP has take this step with a customised set of tubes for a road car in warm climes. I think thats ballsey and merits salutation. The missing part of the equation is the Cams. I think everyone agrees that you can increase exhaust effeciency but without the ability to change the timing and get the gasses out of the cylinder its kinda a half solution. Camlob starts with a 272 bhp 243lb motor. He now has changed the headers and removed the Cat converter - once dyno tested we know the start point on whuich the Cam chage he has planned in a few weeks time will build upon. For me this next data point with an initial guestimate chip via Steve Wong or Steve Weiner is the next interesting data point. Assuming 98RON/93 MON fuel and all ancilaries (MAF, plus, Disti and timing) are in order Im betting the end result should be at least 295 bhp for 260lbft and hopefully 300 bhp for 275lbft although dynbo variances will obvious make a big difference -hence the need for a like for like data point before the work is done....
May the discussion continue. its a great place to learn this! Just a shame in some regards Porsche didnt leave much on the table with these engines. If it were Japanese we would have 20% improvement in power for less than a set of tyres and wheels :-)
Cheers
M
02-11-2011, 09:09 PM
#50
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Camlob - Cool looking pieces and especially for the price. Well done.
I'm at work so I'll have to read through this thread in more depth later (looks fun) but here is an old crappy pic of the "equal length" pieces that I built for my car a while back.
If I remember correctly the runners were all within 0.25" of each other with a total length somewhere around 28".
Burns collectors, 321 stainless and custom flanges.
I'm at work so I'll have to read through this thread in more depth later (looks fun) but here is an old crappy pic of the "equal length" pieces that I built for my car a while back.
If I remember correctly the runners were all within 0.25" of each other with a total length somewhere around 28".
Burns collectors, 321 stainless and custom flanges.
02-11-2011, 09:13 PM
#51
one last thing stock 993 headers aren't half bad
here is what a Bischoff looks like when stripped
they used stripped versions of the stockers on the Cup cars, along w/ gutted cats
02-11-2011, 09:14 PM
#52
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Hi guys. Excellent debate.
However the OP has dissapeared as you have stollen his thread!
I think we are discussing a subject matter akin to the opposite end of the engine (intake configuration) i.e. a subject that has its roots in physics and engineering but lives in the real world of multiple variances impossible to assimilate under contolled contitions. Application is the keyword for these types of modifications. You can build a solution which works for a given application but when you are pushing the 95th percentile the trade off is a compromise of performance for applications outside the parameters of the design brief. I think we can all agree this is why the factory stuck with 50th percentile solutions to create a rounded package that would work for a variety of customers and applications....
One thing remains constant however. I dont think any of these designs can be perfected without engine/chassis dyno or onboard fed data (think Motec M600/800). Im sure none of teh factory race header - exhaust solutions were worked out on spreadsheet without being proto built and put on the engine dyno before a jig was build to produce them in quantity. You need decent resources for that!
In any case. It seems there are a number of designs that work well for mostly race cars. Our OP has take this step with a customised set of tubes for a road car in warm climes. I think thats ballsey and merits salutation. The missing part of the equation is the Cams. I think everyone agrees that you can increase exhaust effeciency but without the ability to change the timing and get the gasses out of the cylinder its kinda a half solution. Camlob starts with a 272 bhp 243lb motor. He now has changed the headers and removed the Cat converter - once dyno tested we know the start point on whuich the Cam chage he has planned in a few weeks time will build upon. For me this next data point with an initial guestimate chip via Steve Wong or Steve Weiner is the next interesting data point. Assuming 98RON/93 MON fuel and all ancilaries (MAF, plus, Disti and timing) are in order Im betting the end result should be at least 295 bhp for 260lbft and hopefully 300 bhp for 275lbft although dynbo variances will obvious make a big difference -hence the need for a like for like data point before the work is done....
May the discussion continue. its a great place to learn this! Just a shame in some regards Porsche didnt leave much on the table with these engines. If it were Japanese we would have 20% improvement in power for less than a set of tyres and wheels :-)
Cheers
M
However the OP has dissapeared as you have stollen his thread!
I think we are discussing a subject matter akin to the opposite end of the engine (intake configuration) i.e. a subject that has its roots in physics and engineering but lives in the real world of multiple variances impossible to assimilate under contolled contitions. Application is the keyword for these types of modifications. You can build a solution which works for a given application but when you are pushing the 95th percentile the trade off is a compromise of performance for applications outside the parameters of the design brief. I think we can all agree this is why the factory stuck with 50th percentile solutions to create a rounded package that would work for a variety of customers and applications....
One thing remains constant however. I dont think any of these designs can be perfected without engine/chassis dyno or onboard fed data (think Motec M600/800). Im sure none of teh factory race header - exhaust solutions were worked out on spreadsheet without being proto built and put on the engine dyno before a jig was build to produce them in quantity. You need decent resources for that!
In any case. It seems there are a number of designs that work well for mostly race cars. Our OP has take this step with a customised set of tubes for a road car in warm climes. I think thats ballsey and merits salutation. The missing part of the equation is the Cams. I think everyone agrees that you can increase exhaust effeciency but without the ability to change the timing and get the gasses out of the cylinder its kinda a half solution. Camlob starts with a 272 bhp 243lb motor. He now has changed the headers and removed the Cat converter - once dyno tested we know the start point on whuich the Cam chage he has planned in a few weeks time will build upon. For me this next data point with an initial guestimate chip via Steve Wong or Steve Weiner is the next interesting data point. Assuming 98RON/93 MON fuel and all ancilaries (MAF, plus, Disti and timing) are in order Im betting the end result should be at least 295 bhp for 260lbft and hopefully 300 bhp for 275lbft although dynbo variances will obvious make a big difference -hence the need for a like for like data point before the work is done....
May the discussion continue. its a great place to learn this! Just a shame in some regards Porsche didnt leave much on the table with these engines. If it were Japanese we would have 20% improvement in power for less than a set of tyres and wheels :-)
Cheers
M
Carry on....
02-11-2011, 09:26 PM
#53
Its a good thing that Bill V and Vincer77 pitched-in to this discussion. Exhaust theory has always interested me. I have learned so much from their discussion that we all have to thank them. Concepts such as the pressure wave response and where it ends or begins is actually mind boggling. Needed several cups of coffee to digest this.
Carry on....
Carry on....
02-11-2011, 09:29 PM
#54
Back to the 997RSR exhaust
Here's the specs for a 3.8 997RSR, note the rev range it works in
Engine type M97/80
Cylinder bore (mm) 102.7
Hub (mm) 76.40
Cubic capacity (cm³) 3797
Compression ratio 14.5:1
Maximum power PS/KW 485/357
Maximum power at 8250 rpm
Maximum torque Nm 435
Maximum torque at 7250 rpm
Maximum revs 9000
Dry weight (kg) 174
Engine oil Mobil1 (0W – 40)
Mobil1 (5W – 40)
Here's the specs for a 3.8 997RSR, note the rev range it works in
Engine type M97/80
Cylinder bore (mm) 102.7
Hub (mm) 76.40
Cubic capacity (cm³) 3797
Compression ratio 14.5:1
Maximum power PS/KW 485/357
Maximum power at 8250 rpm
Maximum torque Nm 435
Maximum torque at 7250 rpm
Maximum revs 9000
Dry weight (kg) 174
Engine oil Mobil1 (0W – 40)
Mobil1 (5W – 40)
02-11-2011, 09:59 PM
#55
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I have been frequenting the Pelican rebuilding forum and gained a lot insights. I think that the DC 24 of John D will suffice for my needs. According to John D, it will work well with the 3.6 as well as a 3.9, just in case if I go that route. It is the most aggressive cam that the stock DME can handle. Together with the long tube header, I hope things will blend in. What do you think about the cam?
As I was talking with my bro, silverboy, I told him at this stage I feel very close to what I am aiming for. This was again from on how the car felt at full throttle. Coming from an E39 M5, I am looking at 240hp/ton. And I think the cam will give me that extra nudge hopefully.
With so much already invested on the car, I will actually take whatever the cam will give!
02-12-2011, 03:35 AM
#56
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Better pic of the LT headers
Pls forgive me on the heater tubes. Ill remove them when the cam comes in. Ill also clean up the engine and suspension components. I dont think I would like it longer since the obvious improvement is from 3k to 7k rpm which I like. I think also the cam would thrive on the higher rpm band. But I will observe and will make adjustments if needed.
02-12-2011, 09:27 AM
#57
Rennlist Member
Thicker sway bars with your JIC install, solid rear suspenson mounts are good for the list. locking kit for ERP toe link if you dint have it nd single RS pully. Just some ideas for your $$$$
M
M
02-12-2011, 09:49 AM
#58
Rennlist Member
02-12-2011, 09:53 AM
#59
Thanks Bill!
I have been frequenting the Pelican rebuilding forum and gained a lot insights. I think that the DC 24 of John D will suffice for my needs. According to John D, it will work well with the 3.6 as well as a 3.9, just in case if I go that route. It is the most aggressive cam that the stock DME can handle. Together with the long tube header, I hope things will blend in. What do you think about the cam?
As I was talking with my bro, silverboy, I told him at this stage I feel very close to what I am aiming for. This was again from on how the car felt at full throttle. Coming from an E39 M5, I am looking at 240hp/ton. And I think the cam will give me that extra nudge hopefully.
With so much already invested on the car, I will actually take whatever the cam will give!
I have been frequenting the Pelican rebuilding forum and gained a lot insights. I think that the DC 24 of John D will suffice for my needs. According to John D, it will work well with the 3.6 as well as a 3.9, just in case if I go that route. It is the most aggressive cam that the stock DME can handle. Together with the long tube header, I hope things will blend in. What do you think about the cam?
As I was talking with my bro, silverboy, I told him at this stage I feel very close to what I am aiming for. This was again from on how the car felt at full throttle. Coming from an E39 M5, I am looking at 240hp/ton. And I think the cam will give me that extra nudge hopefully.
With so much already invested on the car, I will actually take whatever the cam will give!
You should also think about the valves and valve train. You don't want to raise revs much w/o going to Pauter or GT3 rods, if retaining stock rods do at least update the bolts.
02-12-2011, 07:12 PM
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That's roughly equivalent to the GT2 Evo cams, Thats a lot of lift(2.4-2.6mm@overlap) and duration for stock Motronic and stock pistons, the most aggressive cam I've ever seen w/ stock intake and pistons is the ss cam(DC20 or 21) w/2 mm of lift at overlap.
You should also think about the valves and valve train. You don't want to raise revs much w/o going to Pauter or GT3 rods, if retaining stock rods do at least update the bolts.
You should also think about the valves and valve train. You don't want to raise revs much w/o going to Pauter or GT3 rods, if retaining stock rods do at least update the bolts.