How necessary is the Downpipe?

[HarrisRacing]

This was the only time back to back racing I’ve done with the car. It felt sluggish while it was glowing. Ran the car to let it cool but I bet it would have burned oil if I shut it off without realizing. It’s « ok » for turbos to glow under high stress but it will also shorten the life to get beat up all the time. I have catless sitting in my garage ready to go in this spring

You've got me curious to how it has held up. I'm sure circuit racing guys are abusing them much more than most drag guys are. I agree with all that there are likely gains, and likely increased reliability from one less part to fail, but I was just curious on what level this happens at is all.

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[Mason]

You've got me curious to how it has held up. I'm sure circuit racing guys are abusing them much more than most drag guys are. I agree with all that there are likely gains, and likely increased reliability from one less part to fail, but I was just curious on what level this happens at is all.

What makes you think the circuit guys have their stock cats on? ?

My turbo has held up fine because I now know the limits it can handle. It honestly seems you are well on your way to breaking a lot of stuff. The attitude against a <1,000$ cat holding you up is nothing compared to the 2,500$ fuel system or 5,000$ trans build or 2,750$ axels upgrade. If you’re in for high horsepower then take the advise, and prepare to swipe that credit card. Or just lay back and enjoy the car stock, stock is better than broken

 

[HarrisRacing]

A simplier one is this: blow through a straw, then jam a brillo pad in there and blow through it again.

Is it possible to push the same amount of air through it. Absolutey. Is it harder to blow through it with the brillo pad in there? Absolutely.

Anything exhaust flow will cause the turbo to work harder.

I'm not sure why you'd expect the horsepower or 1/4 miles numbers to change if catted vs. not catted if you don't change your boost targets. If the turbo is spooling to 22psi (or whatever) then it's spooling to 22psi. Same as my port injection example above. Sure you can crank the boost and hit 600hp with no supporting mods (there's a reason they're called supporting mods), but you're going to run lean and pop the motor.

Forcing the turbo to work harder means it's going to generate more heat. See @Mason's glowing turbo. Not only is heat bad for performance, but it's bad for the longevity of the component.

But again, if you don't want to hear it, that's fine. I'll be done in this thread now - it seems your mind is made up. It's unfortuate I already sold my stocker turbo though.

What makes you think the circuit guys have their stock cats on? ?

My turbo has held up fine because I now know the limits it can handle. It honestly seems you are well on your way to breaking a lot of stuff. The attitude against a <1,000$ cat holding you up is nothing compared to the 2,500$ fuel system or 5,000$ trans build or 2,750$ axels upgrade. If you’re in for high horsepower then take the advise, and prepare to swipe that credit card. Or just lay back and enjoy the car stock, stock is better than broken

I'm sure when these car companies do their on-track and in-house powertrain dyno testing they are testing the parts to ensure they can handle a racing environment. If not, I don't know how they ever plan to make a single lap around the nurburgring in them. Think about the massive amount of heat energy in the catalytic converter system on a stock car around the Nurburgring.
Here is an example of what they do

LOL swipe that credit card - no need to be insulting or rush to judgement here as I'm going through the steps correctly. Truth be told, I left the dealership with this Supra and a $40k check when I traded in my 2017 GTR 3 weeks ago. Read above where my downpipe IS ON THE CAR (so are my welds, ecutek, flex fuel, Rexspeed wing, etc.). Also read where I read my logs and verified my fueling and knock numbers. I'm not some poor dumb kid that doesn't know what he's doing, I just don't want to mess with tuning this car so I can focus on my 1300 HP 1977 Celica racecar. I specifically asked about a limitation and every answer here except for the guy that ran 10.77 @ 126 has been a guess so far. You guys are literally "guessing" that this will happen or X...and you are arguing tooth and nail against a guess "because" someone else said so. It's like the monkeys that won't touch the banana. Sorry but I came here looking for proof and got a bunch of guesses.

HOWEVER - YES I AGREE A DOWNPIPE WILL ULTIMATELY HELP REDUCE A POTENTIAL FAILURE POINT AND ULTIMATELY MAKE MORE HORSEPOWER. You guys can be sorry that you repeated that so many times (I already knew this!) without knowing the actual answer I was looking for.

Also - go watch more turbo cars dyno in a low-lit shop - exhaust glows all the time (this starts at 900F btw).

 

[Mason]

 

[HarrisRacing]

GESUNDHEIT (best I can do with one word)

 

[zrk]

the guy that ran 10.77 @ 126 has been a guess so far.

Ask Luis. lg_supra on instagram, he's really kind, i'm sure he'll give you whatever answer your looking for.

1300 HP 1977 Celica racecar.

Honestly, I'd looove to hear more about this one. Did you run it at TX2K a bunch of years back? There was a sick 70s celica (i forget the year) with a 2JZ swap and 80something mm turbo. Thing was a beast.

I'm not sure why I didn't think of this earlier, but where's @Marshall@ViscontiTuning? I'm sure he knows more about this than @Mason and I.

 

[Mason]

That’s a pretty good attempt is suppose. I didn’t want to assume that you cannot afford a 300$ catless downpipe (that would be very scary if you own a 60,000$ car) but I did assume that you didn’t really know what you were talking about. I have no idea how you would have a 1300 HP car without knowing the cats will have to go to get big power on the Supra. I may just be ignorant but I’m being honest with how this thread is coming off.

There are real data tests that some companies did with their dp compared to stock, along with other test that refer to power gains on higher boost pressure, all of the point to a catless for best performance. We simply just gave you the answer, it is far from a guess. If you don’t trust anyone here and you NEED evidence for this simple concept then I’ll get you started with one thread. https://www.supramkv.com/threads/catted-vs-catless-my-story-with-data-to-share.6116/

Next I’d recommend to call up downpipe manufacturers. Maybe you will believe them ??‍ Don’t know. Good luck

 

[Bflood]

What a bizarre question.. This is right up there with people running 87 pump gas arguing that premium wont make a bit of difference. ?

 

[underdonk]

This is my turbo glowing because of the stock cat. Can’t dump the pressure or the heat fast enough. If everyone on here is giving you the same advise and you still don’t want to take it, then I’m not sure why you asked in the first place

Damn that's pretty.

 

[razorlab]

This is my turbo glowing because of the stock cat. Can’t dump the pressure or the heat fast enough. If everyone on here is giving you the same advise and you still don’t want to take it, then I’m not sure why you asked in the first place

This is 100% normal on a turbocharged car after going WOT a bunch at night. Same thing during the day, just harder to see the glow. Most cars have heatshielding on the exhaust manifold. Supra does not, so easier to see. Cat or not. My Evo did that 100% stock and also now at 700hp with no cat.

Don't look at rotors on cars tracked at night, that will really blow your mind.

 

[Meraki Autoworks]

AA catted downpipe is a must in our books..

-Josh

 

[Mason]

This is 100% normal on a turbocharged car after going WOT a bunch at night. Same thing during the day, just harder to see the glow. Cat or not. My Evo did that 100% stock and also now at 700hp with no cat.

I bet it would have burned oil if I shut it off without realizing. It’s « ok » for turbos to glow under high stress but it will also shorten the life to get beat up all the time.

 

[razorlab]

Again, that glow is 100% normal. Your post made it sound like it's a bad thing which is inaccurate. 100% normal.

People pay good money for shielding that keeps that heat in the turbo for better exhaust response.

 

[Mason]

We need to add a face palm reaction on these forums ?

 

[SD_MK]

Don't change your downpipe, only morons do that.

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