488 Decat / Test Pipes- Very specific question

Great question, I am interested on first hand experience on this aswell!

The video posted by zooyorker doesnt sound particularly great to me but maybe a bad representation of what it sounds like aswell.

 

Hi Michael,

I was wondering if you manage to decat your 488 with the stock exhaust on? If yes, can you please post a video of it? I'm thinking of doing the same with mine

 

I too would also like to see a video of it.

 

This red 488 has cat bypass pipes but it also has out Xpipe exhaust. Hopefully this helps.

 

No offense that you don't understand what you're talking about.

Again, no engine needs backpressure, backpressure does not increase low end torque, it is never a desirable trait.

If you want to modify your car with removing converters and the undesirable side effect is inconsistent boost control.....you fix the inconsistent boost control....not choke up the exhaust flow post turbo.

That would be easily accomplished by a lighter wastegate spring and an electronic pwm boost controller.

Moral of the story is, if you modify a turbo car you may have to touch more than a single component to do it correctly. Hope you learned something.

 

Incorrect.

 

I'll try to explain this to some degree in regards to backpressure in a turbocharged engine.

Measured between the exhaust valve and the turbine would be considered turbine drive pressure. Smaller more restrictive turbos will have higher turbine drive pressure and be -very- responsive.

Move to a larger turbo (this is all very basic because we need to get into compressor wheel size, turbine size, housing a/r, if it's variable vane/etc)....anyway again, move to a larger turbo and you will reduce turbine drive pressure which comes at the expense of response for the benefit of additional power, shifting the power curve over to the right. Later peak torque and later peak horsepower, and higher peak torque and horsepower. 2opsi in the intake manifold fills a cylinder more when it required 30psi of turbine drive pressure to achieve and not 50.

Secondarily you have post turbine/turbo pressure. Here unlike turbine drive, you never get to a point where more restrictive is more response, again, never. The shortest least restrictive exhaust post turbo will always result in the highest delta/performance across the turbine resulting in the fastest response and power.

So yes, of course if you have moderate/high backpressure post turbine and relieve the system of this pressure (by means of decat for example) with a conventional boost control system (simple spring wastegate referenced off of manifold pressure) and rate will increase (amount of boost that can be achieved vs time and/or rpm) and absolute manifold pressure will likely also increase.

Since you increased the efficiency of the system but are still directing the same amount of exhaust gases through the turbine this will result in higher compressor speed (being they are connected) and therefore boost level.

Which is, why, it was mentioned that when de-catting, a tune would be required. (or if going back to the F40 days, wastegate spring change/modern boost controller install) in order to maintain desired boost rate/level.

 

Thank you for your very insightful info


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Wrong!!!!! On turbocharged applications reducing back pressure after the turbocharger improves turbocharger performance and allows it to spoil and make boost more efficiently. Where do people come up with these myths?


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So a low restriction cat can only help...??

 

Speaking generally, low restriction or uncatted can only help on turbocharged applications. The ancillary challenges you may encounter is the creation of "overboost" or "boost creep" conditions where the turbine efficiency has increased to outflow the wastegate. Uncatted and some high flow catted applications may also trigger check engine lights if they are installed without a tune.

 

Thanks. Because on both my F12 and 458SA the low-end power is noticeably less than when they had 400CEL cats. I clearly understand why however did not relate the benefits on a turbo car; for sure will put a set of sport cats on my 488PA once received.....

 

Phil From Fabspeed here.
In order to get the most out of the vehicle a decat and a tune will get the most sound and performance. However if you are nervous about tuning a sport cat will help you pull the most out of the vehicle without tuning. We just had a 488 in for sport cats, charge pipes and valvetronic. No CEL. Most important about doing sport cats is quality and size. Fabspeed uses 200 cell XL Hjs cats.

 

Anyone done this and have a video?

 

Here you go:
Catbypass and Fabspeed x-pipe

 

that is not with stock catback

 

Fab speed do you have the dunk numbers and curve?