4" exhaust
01-04-2005, 01:01 AM
#46
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In relation to what the cup cars did or didn't have. I was trying to find some pictures that a rennlister had posted a couple of years ago. Unfortunately the pictures are no longer hosted but at least this is some information from a person that has held one of these exhaust systems in thier own hands. This is what he had to say.
"Ok, I found this at hershey. The guy said it was made by a canadian company, I forgot the name, for the 944 turbo cup cars. It is stainless steal and looks to go from stock diameter to 4"s. He also has a muffler that bolts on to the flang that he is shipping me. He was asking $950. I paid $500. what do you all think?"
"Ok, I found this at hershey. The guy said it was made by a canadian company, I forgot the name, for the 944 turbo cup cars. It is stainless steal and looks to go from stock diameter to 4"s. He also has a muffler that bolts on to the flang that he is shipping me. He was asking $950. I paid $500. what do you all think?"
01-04-2005, 01:19 AM
#47
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The Chinese have a saying : TO STOP THE GRASS FROM EVER
GROWING, YOU MUST UPROOT IT. Like Fast said the root is at the hot housing.
Going 4 inch exhaust is a band aid solution which is of small improvement.
Since it is a " MONSTER " motor, there must be buget to try different
combos of turbine & hot housing to get the least back pressure with
provision to good overall performance offcourse. Seeing that it uses a
big hot housing does not mean it's got a low back pressure. A housing
by it self may produce very low back pressure but if used with the wrong
turbine, that combo will still produce alot of back pressure. Same applies
to turbine selection as well.
GROWING, YOU MUST UPROOT IT. Like Fast said the root is at the hot housing.
Going 4 inch exhaust is a band aid solution which is of small improvement.
Since it is a " MONSTER " motor, there must be buget to try different
combos of turbine & hot housing to get the least back pressure with
provision to good overall performance offcourse. Seeing that it uses a
big hot housing does not mean it's got a low back pressure. A housing
by it self may produce very low back pressure but if used with the wrong
turbine, that combo will still produce alot of back pressure. Same applies
to turbine selection as well.
01-04-2005, 01:33 AM
#48
Three Wheelin'
Someone must once again emphasize what has been said many times in this post, but some people still do not understand. The turbo hotside has an effect on backpressure that is in a different and much greater order of magnitude than any part of the exhaust from there back. This whole conversation is faily pointless until you get to bigger turbos. I look forward to Powerwerks data, my prediction is that the 4" shows no gains. Maybe if the 4" chips are better, then the dyno graphs will look good, so this still isnt an exact science.
Porsche can be wrong, this was the 1980s, without todays analytical equipiament. They sure didnt do a good job designing our fuel lines..
I was beat to the punch
Porsche can be wrong, this was the 1980s, without todays analytical equipiament. They sure didnt do a good job designing our fuel lines..
I was beat to the punch
01-04-2005, 01:50 AM
#49
Race Director
Hang on Mark, dont question Porsche now! You HAVE to believe those resources! lol
Yeah data would be very handy. I dont think that "monster" has the budget or not, its not even using a standalone computer. You would expect at least an aftermarket computer to tune it and take advantage of XXX other benefits.
Yeah data would be very handy. I dont think that "monster" has the budget or not, its not even using a standalone computer. You would expect at least an aftermarket computer to tune it and take advantage of XXX other benefits.
01-04-2005, 04:20 AM
#50
Rennlist Member
I know this will probably be falling on deaf ears, but....
The backpressures and pressure change with the graduated 4 inch exhaust were measured not guessed at. And they were measured on more than Robs car.
If your 2.5 liter can make the 375 rwhp at 15 psi, good for you. My K27/8 at 18 psi kept even from a 30 mph rolling start to 125 with a car that dynoed 340 rwhp at 18 psi that has a much larger turbo and 3 inch exhaust. Oh, yeah, both on street gas.
Before you go bashing the Lindseys about 350 rwhp on robs car you might want to consider instead of just using current bolt-ons and getting the gains you would expect going to a 3 liter, they are trying make as much reliable power as possible with a 3 liter engine at 15 psi on pump gas. When tackling project such as this you can surely expect unexpected problems. In this case it looks like the backpressure seems to be disrupting the flow enough that it is not only limiting the car to 350 rwhp, but is also backflowing enough to carbon up the intake. Just as the gains from increasing boost can seem exponential, so can the losses due to problems.
The graduated 4 inch exhaust was developed trying to reduce the back pressure on Rob's car. It was discovered from before and after pressure measurement with the prototype that even 2.5 liter cars running 15 psi boost or more would benefit from the exhaust. Each of the owners noticed a significant increase in acceleration with the graduated 4 inch exhaust over their 3 inch exhaust.
I have no idea why they don't do before and after dyno runs before releasing a new product. Maybe it's because they feel their product and reputation is good enough that the time and money spent on dyno runs is not necessary and would only make the product more expensive.
The backpressures and pressure change with the graduated 4 inch exhaust were measured not guessed at. And they were measured on more than Robs car.
If your 2.5 liter can make the 375 rwhp at 15 psi, good for you. My K27/8 at 18 psi kept even from a 30 mph rolling start to 125 with a car that dynoed 340 rwhp at 18 psi that has a much larger turbo and 3 inch exhaust. Oh, yeah, both on street gas.
Before you go bashing the Lindseys about 350 rwhp on robs car you might want to consider instead of just using current bolt-ons and getting the gains you would expect going to a 3 liter, they are trying make as much reliable power as possible with a 3 liter engine at 15 psi on pump gas. When tackling project such as this you can surely expect unexpected problems. In this case it looks like the backpressure seems to be disrupting the flow enough that it is not only limiting the car to 350 rwhp, but is also backflowing enough to carbon up the intake. Just as the gains from increasing boost can seem exponential, so can the losses due to problems.
The graduated 4 inch exhaust was developed trying to reduce the back pressure on Rob's car. It was discovered from before and after pressure measurement with the prototype that even 2.5 liter cars running 15 psi boost or more would benefit from the exhaust. Each of the owners noticed a significant increase in acceleration with the graduated 4 inch exhaust over their 3 inch exhaust.
I have no idea why they don't do before and after dyno runs before releasing a new product. Maybe it's because they feel their product and reputation is good enough that the time and money spent on dyno runs is not necessary and would only make the product more expensive.
01-04-2005, 04:30 AM
#51
Race Director
Yeah $50 for a dyno run is out of the question? They should have a dyno on site with all the work they are supposed to be doing! Still dont see any data. Thats the problem... Rob does not even know and its his car they were supposed to have tested.
01-04-2005, 08:15 AM
#52
Drifting
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RDK,
Again Lindsey should be looking at the turbine/hot housing instead.
If you want reliable horspower you would want to keep the exhaust
temperature at a managable level. It is the back pressure between
the head & hot housing that matters most if you're looking for reliability.
Again Lindsey should be looking at the turbine/hot housing instead.
If you want reliable horspower you would want to keep the exhaust
temperature at a managable level. It is the back pressure between
the head & hot housing that matters most if you're looking for reliability.
01-04-2005, 09:26 AM
#53
Race Director
Originally Posted by fortysixandtwo
In relation to what the cup cars did or didn't have. I was trying to find some pictures that a rennlister had posted a couple of years ago. Unfortunately the pictures are no longer hosted but at least this is some information from a person that has held one of these exhaust systems in thier own hands. This is what he had to say.
"Ok, I found this at hershey. The guy said it was made by a canadian company, I forgot the name, for the 944 turbo cup cars. It is stainless steal and looks to go from stock diameter to 4"s. He also has a muffler that bolts on to the flang that he is shipping me. He was asking $950. I paid $500. what do you all think?"
"Ok, I found this at hershey. The guy said it was made by a canadian company, I forgot the name, for the 944 turbo cup cars. It is stainless steal and looks to go from stock diameter to 4"s. He also has a muffler that bolts on to the flang that he is shipping me. He was asking $950. I paid $500. what do you all think?"
I have photos of this exhaust on a Canadian Cup car, if people would like I could find them and post them.
01-04-2005, 09:58 AM
#54
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A friend of mine has a dry sumped 2.5 that made 530 crank HP @ 6900rpm @ 18psi. He used a 2.5" downpipe / half testpipe into a 4" cat area and 4" cat back. I can't give you the dyno sheet but is anyones been to limerock CT, they know the car.
01-04-2005, 10:07 AM
#55
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Originally Posted by RKD in OKC
I have no idea why they don't do before and after dyno runs before releasing a new product. Maybe it's because they feel their product and reputation is good enough that the time and money spent on dyno runs is not necessary and would only make the product more expensive.
Its easy, no dyno charts no sale. Thats why a can't justify the SFR header that I drool over, all the time..
You need real back to back test and they should be on stock motors as well as modified motors..
None of this seat of the pants ****..
01-04-2005, 10:21 AM
#56
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For right now I will say nothing on the 4 inch system we are making........ as we have not tested it or built the chips for it!
Once we have done this and have some actual firm data, then I will post our findings!
We are will be testing many designs and configurations to see what the true gains are.... nothing we sell will be hearsay! Every item will come with data and dyno.
As I mentioned... we have access to 3 original factory Rothmans Cup cars! The cup cars only had 300 or so hp and the Canadian cars ran a 4 inch test pipe / exhaust.
If I recall correctly the Canadian cars with the 4 inch systems had a reasonable amount more hp! Wasn't it 23 hp gained!
Pipe size and correctly managing pressure is the key..... we successfully built a 911 exhaust / header system that hands down beats anything on the market! And we have a LOT of dyno, lap times and data to prove it.
Strangely enough we found a smaller pipe on the headers actually works better.... it gives better and more even compression. Manufacturers such as B&B etc... clearly have not tested their product to the degree we have, as they would see using larger diameter piping for the headers looses HP!
Give us a few weeks then we will give firm data to prove one way or the other.
Cheers,
Paul
Once we have done this and have some actual firm data, then I will post our findings!
We are will be testing many designs and configurations to see what the true gains are.... nothing we sell will be hearsay! Every item will come with data and dyno.
As I mentioned... we have access to 3 original factory Rothmans Cup cars! The cup cars only had 300 or so hp and the Canadian cars ran a 4 inch test pipe / exhaust.
If I recall correctly the Canadian cars with the 4 inch systems had a reasonable amount more hp! Wasn't it 23 hp gained!
Pipe size and correctly managing pressure is the key..... we successfully built a 911 exhaust / header system that hands down beats anything on the market! And we have a LOT of dyno, lap times and data to prove it.
Strangely enough we found a smaller pipe on the headers actually works better.... it gives better and more even compression. Manufacturers such as B&B etc... clearly have not tested their product to the degree we have, as they would see using larger diameter piping for the headers looses HP!
Give us a few weeks then we will give firm data to prove one way or the other.
Cheers,
Paul
01-04-2005, 11:14 AM
#57
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Precisely Paul, going bigger pipe on the header is a bad
choice. What we want is to keep the velocity as high as
possible. Going bigger will not only slow down the gas
it may actually cause turbulance & increase back pressure.
For me I think it goes with turbo down pipe as well. I feel
that the down pipe should be match to the size of the turbine
outlet before stepping up in size from down pipe onwards
choice. What we want is to keep the velocity as high as
possible. Going bigger will not only slow down the gas
it may actually cause turbulance & increase back pressure.
For me I think it goes with turbo down pipe as well. I feel
that the down pipe should be match to the size of the turbine
outlet before stepping up in size from down pipe onwards
01-04-2005, 11:59 AM
#58
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J chen.... we have been testing and playing with the turbo down pipe. I will post our findings soon!
I think using a 3 inch is ok but you will need to have the turbo to justify it!
We have made many little design and engineering changes throughout the entire exhaust system that will make a big difference. I will offer more info on this shortly.
The whole system needs to be well balanced or otherwise the gains will be countered and lost.
We are not just making parts that look pretty.... we want to make sure they work or what's the point!
To long has there been unproven and false claims made by manufacturers..... who are very willing and eager to take our money, but not back up their product.
I know how frustrating this feels as I have been on the customer side for 10 years! I feel I have wasted a LOT of my hard earned money buying things hyped up by the manufacture.
There seems to be a list and a pre-set speech on what you need and what you should spend your money on....... half the stuff doesn't work. Actually we are finding most of it due the poor way it is designed is actually making things worse!
So we are really taking our time on this and making sure what we have really does work! ...... and just like our 911 system we will have plenty of test data and dyno to prove it.
Cheers,
Paul R
I think using a 3 inch is ok but you will need to have the turbo to justify it!
We have made many little design and engineering changes throughout the entire exhaust system that will make a big difference. I will offer more info on this shortly.
The whole system needs to be well balanced or otherwise the gains will be countered and lost.
We are not just making parts that look pretty.... we want to make sure they work or what's the point!
To long has there been unproven and false claims made by manufacturers..... who are very willing and eager to take our money, but not back up their product.
I know how frustrating this feels as I have been on the customer side for 10 years! I feel I have wasted a LOT of my hard earned money buying things hyped up by the manufacture.
There seems to be a list and a pre-set speech on what you need and what you should spend your money on....... half the stuff doesn't work. Actually we are finding most of it due the poor way it is designed is actually making things worse!
So we are really taking our time on this and making sure what we have really does work! ...... and just like our 911 system we will have plenty of test data and dyno to prove it.
Cheers,
Paul R
01-04-2005, 03:58 PM
#59
Race Director
Originally Posted by evil 944t
I hope they don't think this way.
Its easy, no dyno charts no sale. Thats why a can't justify the SFR header that I drool over, all the time..
You need real back to back test and they should be on stock motors as well as modified motors..
None of this seat of the pants ****..
Its easy, no dyno charts no sale. Thats why a can't justify the SFR header that I drool over, all the time..
You need real back to back test and they should be on stock motors as well as modified motors..
None of this seat of the pants ****..
01-04-2005, 04:00 PM
#60
Race Director
Originally Posted by J Chen
RDK,
Again Lindsey should be looking at the turbine/hot housing instead.
If you want reliable horspower you would want to keep the exhaust
temperature at a managable level. It is the back pressure between
the head & hot housing that matters most if you're looking for reliability.
Again Lindsey should be looking at the turbine/hot housing instead.
If you want reliable horspower you would want to keep the exhaust
temperature at a managable level. It is the back pressure between
the head & hot housing that matters most if you're looking for reliability.
