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Just tossing a quick feeler out for those modifying their 718's...with very well made high flow catalytic converters being pretty readily available these days...are there a good number of folks out there who still prefer to go catless? If so, is it primarily for power gain or for the sound? With the EPA cracking down on sellers of emissions bypassing products this is a piece of information that our business would love to know. We are the #1 North American importer of German HJS High Flow Cats which flow very close to straight pipe set ups but give you enough emissions scrubbing to not throw a check engine light nor smell like a bus to those driving behind you. Which way are 718 owners tending to go with your exhaust setup lately?

 

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In Australia exhaust modifications can be dicey—they still have to pass our noise regulations. If they find you without the mandated anti-pollution gear it can be really bad news.
 

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Catless definitely sounds better IMO. But unless you are willing to tune (or live with the CEL) then its not worth it.
 

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APR claim they have tested stock cat vs catless with no benefit, so it is not clear which is true. It would be great if we had dyno graphs of the 3 options on a stage 1 tune, but obviously that takes some money/effort to arrange for a 718 owner, and companies selling the parts in question are likely to be biased.
 

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I like catless on most my vehicles for additional sound. But it is somewhat raspy and stinky. I will most likely do a sport cat downpipe on this car to A. Keep it not stinky and B. Remove some of the unwanted noises from the soul straight pipe exhaust I have on order.
 

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As with most engine modifications -- heck, as with most cause-and-effect relationships, period -- any change, 'gains', 'losses', etc. that are actual quantifiables must be presented using the Scientific Method: present a test without the change, then present that same test with the change with no changes to any other variables in the system.

One of the endemic problems with the engine modifications industry is that results that properly apply the Scientific Method are almost never presented. Power gains from an exhaust (or a cat, or a downpipe, or what have you) frequently require a tune, which is a variable change. Tests are run on two different dynos -- that's another variable change. Tests are done on two different days during which the weather is significantly different -- Hey! Another variable change! :-/

When asking this kind of question, it's important to ask what else is different other than the component being touted. Not doing so basically means you could be sipping snake oil.
 

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I agree with above. I have worked in this industry. There is always a vested interest in the result. It is quite easy to run a dyno in a way that increases power if desired. Customers who get a workshop to do mods to their car expect to see improvements. Dyno operators know how to keep customers happy. When I was tuning my WRX, at the end of a session if I wanted a big number, I could adjust the tie down straps in order to get around 20kW more power.

Given the relative simplicity of changing the downpipe in a 718, it would be fairly easy to perform a test at a workshop with a dyno where a 718 with a state of tune that supports catless operation (APR Stage 1??) could be run in 3 states with stock cat, 200 cell cat, and test pipe. This could be done on the same day. A protocol of running a warmup phase and following with 3 power runs could be done. It is not that hard.... but it requires access to a car with tune and several downpipes which is beyond my resources to organise. Someone like Fabspeed or Soul could do this but they have a vested interest in the outcome, so we may not get true results.
 

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I agree with above. I have worked in this industry. There is always a vested interest in the result. It is quite easy to run a dyno in a way that increases power if desired. Customers who get a workshop to do mods to their car expect to see improvements. Dyno operators know how to keep customers happy. When I was tuning my WRX, at the end of a session if I wanted a big number, I could adjust the tie down straps in order to get around 20kW more power.

Given the relative simplicity of changing the downpipe in a 718, it would be fairly easy to perform a test at a workshop with a dyno where a 718 with a state of tune that supports catless operation (APR Stage 1??) could be run in 3 states with stock cat, 200 cell cat, and test pipe. This could be done on the same day. A protocol of running a warmup phase and following with 3 power runs could be done. It is not that hard.... but it requires access to a car with tune and several downpipes which is beyond my resources to organise. Someone like Fabspeed or Soul could do this but they have a vested interest in the outcome, so we may not get true results.
I'm game if a manufacure wants to pay for the labor and dyno time. I've made the investment in 200 cell cat and test pipe setups where the only variable will be the cat/no cat. Still have the factory downpipe set up too.

For what it's worth...

I noticed a negligible difference in stock cat vs 200 cell power levels. Gain? Sure but again negligible.

From 200 cell cat to catless test pipe, negligible to zero change in power. Sound is greatly improved and my driving force for the cat delete. I don't care about the stink... I'm not the one getting whooped by a 4 cylinder Porsche!

I should start handing out rape whistles to the dodge boys... 😆 It's even funnier when you embarrass them with a Tesla.
 

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I'm game if a manufacure wants to pay for the labor and dyno time. I've made the investment in 200 cell cat and test pipe setups where the only variable will be the cat/no cat. Still have the factory downpipe set up too.

For what it's worth...

I noticed a negligible difference in stock cat vs 200 cell power levels. Gain? Sure but again negligible.

From 200 cell cat to catless test pipe, negligible to zero change in power. Sound is greatly improved and my driving force for the cat delete. I don't care about the stink... I'm not the one getting whooped by a 4 cylinder Porsche!

I should start handing out rape whistles to the dodge boys... 😆 It's even funnier when you embarrass them with a Tesla.
how is the sound with cat delete? What exhaust do you have?
 
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I agree with above. I have worked in this industry. There is always a vested interest in the result. It is quite easy to run a dyno in a way that increases power if desired. Customers who get a workshop to do mods to their car expect to see improvements. Dyno operators know how to keep customers happy. When I was tuning my WRX, at the end of a session if I wanted a big number, I could adjust the tie down straps in order to get around 20kW more power.

Given the relative simplicity of changing the downpipe in a 718, it would be fairly easy to perform a test at a workshop with a dyno where a 718 with a state of tune that supports catless operation (APR Stage 1??) could be run in 3 states with stock cat, 200 cell cat, and test pipe. This could be done on the same day. A protocol of running a warmup phase and following with 3 power runs could be done. It is not that hard.... but it requires access to a car with tune and several downpipes which is beyond my resources to organise. Someone like Fabspeed or Soul could do this but they have a vested interest in the outcome, so we may not get true results.
For this reason we display third party dyno charts on our website as we expect people to be able to repeat these numbers should they have their own dyno session. If anyone wants to dyno our downpipe, we're happy to display the results no matter the outcome. If more power is made, great! If less is made, that's real data as well that we can't devalue. The more information the better. Different dynos read differently, different cars perform differently, different days lead to different conditions.

As far as doing several operations back to back on the same day, we'd have to eliminate the possibility of the ECU needing to learn driving habits in between modifications. While the technology is different and modern turbo cars learn faster, Scott at Softronic told me today that he needed to allow up to 25 laps at Sebring or a full session on the 2009 World Challenge cars to allow them to adjust and realize full power potential.

-Mike
 

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As far as doing several operations back to back on the same day, we'd have to eliminate the possibility of the ECU needing to learn driving habits in between modifications. While the technology is different and modern turbo cars learn faster, Scott at Softronic told me today that he needed to allow up to 25 laps at Sebring or a full session on the 2009 World Challenge cars to allow them to adjust and realize full power potential.

-Mike
So what your telling me is that I need to stop the grandpa driving... Because I'm teaching my car bad habits!

28004
 

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For this reason we display third party dyno charts on our website as we expect people to be able to repeat these numbers should they have their own dyno session. If anyone wants to dyno our downpipe, we're happy to display the results no matter the outcome. If more power is made, great! If less is made, that's real data as well that we can't devalue. The more information the better. Different dynos read differently, different cars perform differently, different days lead to different conditions.

As far as doing several operations back to back on the same day, we'd have to eliminate the possibility of the ECU needing to learn driving habits in between modifications. While the technology is different and modern turbo cars learn faster, Scott at Softronic told me today that he needed to allow up to 25 laps at Sebring or a full session on the 2009 World Challenge cars to allow them to adjust and realize full power potential.

-Mike
I respect and appreciate that approach Mike. It is really the best you can do. But even in the case of customers doing dynos, the results are likely to be tainted. Even sometimes not intenitonally. Typically a number of dyno runs will be done, and it is highly common for the dyno operator to provide the customer with the runs that make the customer happiest... so the worst before run and the best after run.

ECU learning is a thing, but if you are not changing much, it should learn quickly. A little bit of post turbo flow should not alter the tune requirements much. A warmup phase on the dyno at varying load and RPM followed by a period of coasting with fans on intercooler to get intercooler temps stable followed by 3-5 runs with a coast down (1-2 minutes) to cool intercooler between should be adequate. Using the final run for comparison. It is likely that this would provide better results than doing comparison runs after a several day time for ECU learning. No two days have the same conditions, and dyno corrections for turbo cars are really just a guess (modern cars try to correct themselves so old school NA corrections are not helpful).
 

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Sound is amazing... Loud outside, yet quiet in the cabin!

Factory PSE with the Soul cat delete downpipe.
are you getting a CEL? i was thinking about going this route. i have catless on my BMW but used a Vibrant o2 spacer which prevents the CEL from coming on so i was wondering what you did? thanks!
 
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