REAL RESULTS.. Is it really worth running NO CATALYTIC CONVERTER? We test it on our big power SUPRA.

It's no surprise that we all want as much power as possible, but sometimes the smell of unburnt fuel can get overpowering, make you stink like you've been at a gas station all day and infects the upholstery in your car... So we have always wondered just how much power we would be gaining if we decided to run NO CAT at all..
This is a tricky one because from factory, cars typically come with quite a restrictive catalytic converter, so the real question here is - how does a completely gutted or removed cat compare to a decent sports exhaust with a high flow cat?
We hit up XForce Performance and GT Auto Garage to help us answer this one.
Our JZA80 Supra makes around 850whp on 33psi of boost, so this was going to be quite a demanding task on the catalytic converter, since at those power levels, we are probably getting to the region of maybe needing to look at a 4in system instead of a 3.5in. So even the mufflers and resonators are going to be giving some restriction, let alone a 100 cell cat.
But, there was only one way to find out just how much power a cat robs, and that was to throw it on the dyno.
With the assistance of MDSFab, we got a 3.5" "test pipe" made up, and a direct bolt in 3.5in cat on some matching flanges so we could easily swap out the test pipe for the cat and run some back to back tests.
We did 3 runs for each setup, with the results being quite consistent and within a few horsepower of each other.
It should be noted that the real difference only comes into play at the very peak power levels. Average punters with 500-600hp cars will see absolutely no gains in removing their cat, while people with 1000+ hp cars will probably see a further improvement by going a bigger exhaust all the way through.
Now that we have answered this, let's see what we can do with a 4" system!
For anyone interested in the T51 sound mod, hit up / turbomodpro
Engine specs:
Stock 2JZ VVTi block
Kelford Cams V202-D 272/278 10.2mm lift cams
Kelford valve springs to suit
Hypertune 100mm intercooler & plenum
Turbosmart 60mm gate, BOV & RR-FPR
GCG Turbochargers Pty Ltd GTX3584RS-2
Turbomod.pro compressor housing modification (T51mod)
6boost exhaust manifold
Haltech Elite 2500 ECU
PWR Performance Products radiator
Southam Engineering R35GTR ignition coil conversion
Hardrace Suspension Australia engine and trans mounts
Wiring by Whitey's Wiring
Boomslang engine harness
2200cc Bosch injectors
ARP head studs
XForce exhaust with 100 cell high flow cat
Tune by GT Auto Garage

[@mikeysuperfly1997]

Testing no cat starts at 7:00 your welcome.

[@YyouTTubeE]

thank you. have a nice day

[@stevecvntniko8271]

Thanks champ

[@samlaw6075]

Thanks a lot dude

[@SpadeNya]

Take your like, timestamp.

[@sv9241]

Thanks

[@mihailpetrovici5044]

15 minutes for 2 numerbes, damn no cat: 764 hp 768 hp, 767 hp xcaat (sport): 755 hp, 753 hp 752 hp less power, less loss

[@StreetFXofficial]

it's not just about the numbers, people may be interested in learning something and seeing how it's done? I would much prefer to make 20 second videos, as it is far less work.

[@2511jeremy]

Your not very good at counting i see 6 power figures 18 numbers and you cant spell "numerbes" we got a real intellect here

[@mihailpetrovici5044]

@@2511jeremy 😂😂😂haha, numbers*

[@2511jeremy]

@@mihailpetrovici5044 lol i spelt it like that because i was coping your spelling lmao dumb ass numbers is how you spell it kid

[@sli-fox]

Try getting off graveyard and watching this. Fell asleep twice just waiting for the result.

[@755hp]

4:17 Every SINGLE mod he just read off is an absolute DREAM! That’s how you build a high quality 2JZGTE engine!!

[@bobbyromo69]

Maybe you should run this test again with a factory cat. Cause the people watching this video are probably looking into cutting off their factory cat

[@nelayo4894]

the result would be different yes. I´ve tested it on a supercharged camaro (about 680 crank HP) and it was about 730 crank hp without a cat. so a bit under 10%. With a street legal tuning cat we still got around 705 hp. The question now is what you intend for the car. you wont really miss those 25 hp in a daily car but its definetly better for the environment (and also illegal to drive without a cat in some countries). I agree that the test is not perfect, but it at least shows that a aftermarket cat is an acceptable option compared to deleting the cat.

[@177SCmaro]

Removing the factory cat from a factory car probably won't do much either. I built a delete pipe on my mostly stock celica gts and all it really did was make the car sound worse so I put the cat back on. Toyota knew what they were doing when they sized that cat. The only car I've had were it made a significant difference was on my old 78 camaro when it was stock but now we're talking those awful pellet filled cats they haven't made for decades.

[@nelayo4894]

@@177SCmaro yeah, in my expierence (i live in germany) its not worth the hassle with police and the tax office (if you delete your cat they tax you as if your car has no exhaust cleaning at all which forces you to pay higher taxes besides the fine for driving without a cat) so its easier to change the intercooler or do something with the software

[@southjerseysound7340]

@@nelayo4894 I've seen similar results of 5-10% and these days I don't think it's worth not running one on a real street car that sees a lot of street driving. The only time I've seen a cat reach 10% or more loss is when a car has been run pig rich in the tune.

[@adamweaver6351]

Yup

[@ts8744]

Great video, I really appreciate that you put the results in the description!! Most people would have you watch the whole video when you just want the couple sentence answer.

[@in54ne82]

Some catalytic converters that are connected right after the turbos like in the bmws makes the turbo seals to fail usually when running higher boost. In some vehicles it's better without cats for reliability and they also run cooler.

[@LucoreAuto]

Excellent video thanks for the info and straight forward comparison! There also seems like a bit of a drop in PSI between the test pipe and high flow as well? Any way you look at it though, go high flow cats save the environment (a little bit), avoid a fine or worse, and don't smell quite as much like a service station!

[@StreetFXofficial]

NOTE: There is an error in the video that I need to correct: The high flow catalytic converter as shown is a Metallic substrate which is coated in ceramic, and not a straight up ceramic honeycomb substrate as mentioned. Their functionality is essentially the same. Also note: Please read the annotations in the video. This is not to say that there aren't gains to be had from removing your factory cat.. but the comparison here was between decat and a high flow sports cat which any decent exhaust system should have.

[@AmirPomen]

Hi.. can u guys get a stock sports car so some economy car that often people mods, and see with just removing the cat without any other mod, will we see any gains?

[@StreetFXofficial]

@@AmirPomen we will be testing this exact thing in our A90 Supra soon :)

[@AmirPomen]

@@StreetFXofficial awesome! Cant wait

[@JesusisJesus]

Could you also test it with a complete exhaust system bypass valve like they secretly put on police cars when they throw the switch that turns on the lights and they go full rip on open headers to chase down Supras and Skylines.....?

[@PKperformanceEU]

Decat definitely makes a big difference in any force inducted car. Cut the BS..my car gained about 20hp just from DPF delete. And there's the second cat that gives another some power if deleted as well as soo much better EGT. Here in the video without a tune 15hp with a euro3 cat delete only speaks for itself

[@freakyRunner]

Get a 5inch Catalytic converter. In this case size matters. HJS (Worlds best Catalytic converter Producer) says with a 5 inch 200cpsi Cat in a 3inch exhaust you only lose 2% of flow. Greetings from Germany 🇩🇪

[@pec1739]

thanks for the info, i guess it wont be cheap after all since alot of exotic metals inside the cat

[@freakyRunner]

@@pec1739 HJS Catalytic Converters are never cheap but they work perfect.

[@hoonaticbloggs5402]

It’s a problem to fit a 5 inch cat on most cars. Especially lowered cars

[@CP110]

in CA we cant get any cats that arent CARB legal delivered to a CA address. not even for "Track cars"

[@vsewerv]

@@CP110 deliver it to a po box in Arizona...

[@_ez4u2c_9]

Thank God someone conducted this test properly, great job guys

[@Weird.Dreams]

Yep, 13hp is pretty decent. Happy with my decat!

[@alexburlya9700]

This is one of the NICEST Supra's put together Ive seen really great job bro i love all the upgrades you've done to it looks amazing i love every single thing about it ! 5 ☆☆☆☆☆

[@StreetFXofficial]

Thank you :)

[@jacksmith3189]

Excellent information Thanks Beautiful car

[@jfro5867]

Good vlog chaps. I don't wear sandals but seeing as we are all suffering from extreme weather around the world I'm gonna leave my CAT in my motorcycle exhaust after watching this, seeing as having it makes bugger all difference 👍👍

[@brandon8783]

Thanks for this. I'm shooting for between 500-600whp on an sti and a lot of people are telling me to go catless or I'll lose 500rpm spool and around 50whp. 🤦🏾‍♂️

[@ChrisMotorONE]

Man!! That’s a clean Supra

[@madmike5144]

Cool video thanks for sharing with us

[@genedowen9183]

so - 2.1%. And no stink. But for the track... With larger diameter exhaust I bet the delta drops. And another cat with a larger diameter (say 6" cat diameter) maybe even less. I really like this direct comparison. good job.

[@Anthony-ub1df]

love the build! one question how did you get the DBW throttle body to clear both power steering lines? i used a PHR fitting for one, but the high pressure one Im not sure on.

[@Mikey6048]

Don't give a shit about the environment, when it comes to going faster. The most truthful statement I've heard on KZbin.

[@madmod]

Cars don't operate in the environment. They are on roads and in cities.

[@mohammeddmalik]

Great content. Subbed!

[@deimosadrastos6172]

so what about a Stock CAT vs a High Flow CAT?

[@Zcypot]

the video i needed to see thanks! I am going to need to run a cat and I was worried how restrictive it would be. If 700whp will flow fine then I am ok.

[@mandip1188]

might also be worth doing a test with different cats too - 200 cell, 400 cell etc etc

[@lordozi3113]

I broke out the cat on my w124 with the M104 motor and I can tell you with confidence it's much happier past 3k rpm, high flow cats aren't restrictive at all but say on a stock car, especially like a Supra or old Benz they do rob some power, or so I'm convinced any way The cat wasn't borked to begin with, car didn't feel sluggish or anything but after knocking it out it seemed to have slightly better response... Also sound

[@knoxvitela2277]

I came for one thing and you explained everything

[@RadDadisRad]

That whistle mod is badass.

[@StreetFXofficial]

hell yeah it is :D

[@texasflysuperstar]

RIP headphone users

[@dillanmistry]

13:21 is that blinding lights, wow i just subscibed

[@damoncrowfeather4655]

I wouldn't expect to see much of a difference with high flow cats.. but with factory oem cats.. Yes!

[@2011samv]

I'd suggest a soundproofed style custom valve cover may reduce some of your engine noise

[@nazimelon6653]

Ngl, this is probably the nicest Supra ive seen in a long time if not ever. Damn.

[@sstevocamaro]

Awesome video!!

[@ZheikoNileth]

never happened to me to be stinky from exhaust fumes when running decat and actually driving somewhere. Sitting inside closed garage and having the car running is different story altogether, but I would not advice doing that for completely different reasons!

[@AndrewM62]

No Cats = More Power, Thanks for the video! Great work

[@firstnamelastnameisallowed7943]

All the epic turbo sounds!!! Awhhhwwh I love it!! Should make a soundtrack of nothing but turbo noises. LoL id bump that shit

[@hoonaticbloggs5402]

4th feb here in the uk was 4deg C and the air is dense and damp. Perfect turbo car weather.

[@arc00ta]

IMO The bigger problem with aftermarket forced induction is if the cats can take the heat (literally). Modern cars have variables in the tune for cat protection to help cool them down - something I suspect cars like the GT500 and Hellcat rely on heavily to stay legal and carry the warranty duration- otherwise you end up with a blown motor from a suddenly clogged exhaust pipe. Seen several factory cats melt on boosted coyote cars personally and it isn't pretty.

[@2dannyboy584]

Gorgeous car mate..

[@sacrificialrubber779]

I’d guess 8-10 HP difference max, hf cats are pretty good now!🤷🏻‍♂️🤘🏻

[@SI0AX]

You have to look at it percentage wise. HP gains are about percentages not a fixed number. With the high flow cat it's about a 2% power loss.

[@97markviii]

It's 1-2% loss. Pretty minor for most people.

[@SteveBrueck]

Who cares, they sound better.

[@danieldelpha1315]

Thank you

[@CP110]

on a boosted engine exhaust piping diameter actually matters as well 3in vs 4in vs 5in and the amount of HP you make matters, on supra forums we have a well documented thread of people running higher horsepower making more power with bigger exhausts/no-cats once you get to the 1000-1200 hp range you will see gains in the 50hp range by just going to a 4in-5in downpipe/exhaust. which makes it drone like mf so we still recommend 3.5in downpipe and either 3.5 or 3in exhaust for the street

[@StreetFXofficial]

We're planning on switching out to a 4in turbo back. Got a brand new, discontinued HKS Super Drager we managed to find, so am keen to hear what it sounds like with that 🤗

[@Brocep]

What I want to know is if there's a cat that will hold up to sustained or repeated two-step? I've seen a few vids of people running stock cats with big hp, just revving a bit in a parking lot and out comes a fireball and plume of cinders of what used to be inside the cat.

[@hedleyt8095]

Need to do it with a factory cat. People are looking to remove factory cats on car that doesn't have big power. Do the same test on an everyday car... Video is informative though 👌

[@ardennielsen3761]

is it normal for the exhaust tips on a duel exhaust for a 4.6L OHC Ford to be able to boil water on contact? think i am running a bit lean? just driving around no faster then a Toyota Prius would. think it might be the catalytic converters making the exhaust system so hot.

[@carlbrooks90]

Im running no cat and I noticed no power lost on my vehicle.

[@Marticus518]

Don't forget the added visual effect when running a cat by having glowing particles shooting out of your exhaust during 2-step ;)

[@StreetFXofficial]

aha that's always a bit of fun :P Love looking up the tail pipes of lambos and mclarens and seeing the cats glowing red hot :D

[@RadDadisRad]

Lol 2 step is pretty good at blowing out cats

[@SuperSpiderHulk]

Just curious if that would be different for car to car or different exhaust especially if you're running one or more cat

[@ZZZracing]

It'd be interesting to also see testing with current air filter, a bigger filter, and no air filter.

[@sinnieleeonUtube]

My cat. conv. was just stolen and I'm wondering if it worth it to replace it with a pipe. I just want to reduce the noise rather than getting more HP. It seems the engine is still very loud with the pipe installed. Does the pipe reduce the engine noise at all than without the pipe nor the cat. Conv. installed ?? Also can you drive temporary without the cat., It seems the engine is roaring hard when I step on the gas, even lightly. Thank You for any feedback.

[@james10739]

Well i assume the turbo will make the same boost there will be some restrictions in the exhaust i figure a max would be less but I dont know I guess was will see

[@755hp]

12:03 HOLY SHIET!!!!!!!!!! I was spot on!!!!! 755whp!!!!! YEAHHHHHH THATS my number baby!!! 😎👍⭐️⭐️⭐️⭐️⭐️

[@sbfguy7793]

@anonymous 🍪cookie?

[@StreetFXofficial]

@anonymous it's 755hp at the rears. It's not adjusting for drivetrain loss.

[@izzyplusplusplus1004]

@anonymous Add about 15% for drivetrain losses. 755 + 15% = 868

[@ricardoreis7298]

So, less than 2% difference? Thanks for the video!

[@18nabeel]

Holy mother of inline 6 that jz just sounds so good! 😍😍😍😍😍

[@aveirozinou2919]

Straight to my experience, i gutted the cat in my exhaust manifold and i replace the 2nd catalytic with a resonator, the car has 85 HP stock, but i feel like i have another car with better engine Ps : i didnt run a horspower test

[@hendrahendra]

Your stock Catalytic Converter would be very restrictive, the high-flow cats are less restrictive as shown.

[@Luminous65]

How old are your car? Maybe your stock catalytic converter are old and broken so that can be why you feel gain.

[@andrewmcintosh9832]

Gutting your cat creates turbulence. It's better to get a test pipe.

[@TofumanFC3S]

Dude, people don’t delete high flow racing cats, they delete decades old, clogged, restrictive OEM cats...

[@StreetFXofficial]

This video is more to show whether it's of significant benefit to do a complete decat, or just add a high flow when you're otherwise planning to swap out your factory unit.

[@fatTony666]

@@StreetFXofficial you explained that clearly, hey what city are you in ? Aussie Aussie Aussie

[@asjmpickle]

@@StreetFXofficial yeah but how much does a high flow cat over 300-500mm of stainless 3"pipe?

[@jayswisher575]

TofumanFC3S very good point. Still an interesting video tho.

[@allenhawkins1110]

Or they take them off, smash the guts out of them, and bolt them back in. That way they look legal.

[@james10739]

I wonder how hot it gets and long it will last because ay those power levels it is surely rich

[@matthewbailey5921]

With that ticking sound I had the same thing drive me mental when i went big cam and single turbo it was the mls gasket on the turbo manifold to the head have a look and make sure you haven't got an exhaust leak

[@StreetFXofficial]

Yeah I know the noise you mean, but in our case the noise isn't there til the vvti switches off cold start. It's actually quiet when the car is first fired up, then when it's warm it just makes that ticking sound. Unplugging the solenoid or advancing the timing also changes the tone. We tried advancing the idle timing to take up the "slack" and shut it up but it didn't work :(

[@festungkurland9804]

@@StreetFXofficial Does the car have an egr system?

[@D3AThCAl2DS]

My bet is valve spring rates

[@minimanadam]

100k$ car and a 50$ jack..lol

[@S13KON]

It did the job..Who cares!

[@RicondaRacing]

Are you the Snap-on truck guy?

[@755hp]

I’m going with a guess of 755whp!

[@tedtedness184]

Please do this the i30 Hyundai.......a style car most of us can relate to. $$$$ wise.

[@felixf5211]

We've done a lot of testing in the Evolution community. On a mildly tuned Evo it's less than 10whp loss. Not worth it to me.

[@NikkisNugs]

That's a huge difference. My EVO Zero is cat-less and now spools faster. I would take any whp even 1.

[@wildbill7535]

Does cutting the factory cats out interfere with the running of the car?..make it throw codes or cause electronic glitches?

[@jonasr.3083]

15 Hp are worth it to care a bit about the environment.

[@onionman500blin8]

Yeah

[@dagas94]

How about no?

[@jonasr.3083]

dagas94 we're all living in the same world and it is beautiful so we have to do something to keep it healthy

[@dagas94]

True. Removed the cat on my scirocco here the other day. Replaced it with a downpipe. Totally worth it

[@tiko5876]

dagas94 hell yes Man. I love vw too haha. Straight pipe VR6 all day I don’t care about the environment, Talk to the corporations about their pollution before you come at the common man about their hobbies polluting a wee bit. And then ill be on board lol

[@pseudonymBOB]

Answer @ 14:28

[@Thedirtyfernie]

The more power/airflow, the greater the restriction. Its exponential. Lower hp will loose less power naturally with the cat because if its lower power.

[@ChurchAutoTest]

Turbo cars are actually somewhat easier to add a catalyst too because after the turbo they really aren't dependent on anything other than raw flow rates for power. For NA cars (and some supercharged models) the location of the catalyst can make a big difference in exhaust scavenging from the header pipes, to the point where some big cammed NA engines can really suffer unless you move the cat way back of the collector. The only drawback to that is the cat really doesn't heat up enough to do its job then.

[@StreetFXofficial]

We will test an NA car next :)

[@supradma71]

What is your vvti set to at idle? Typically putting a few degrees of vvti in at idle gets rid of the rattle, or did you already try that?

[@StreetFXofficial]

Tried that. 😓

[@LNFFTW16]

what are the full throttle afr set at with or without the cat?

[@StreetFXofficial]

Ahhh.. you know your stuff :) while the first run was back to back with no fueling changes, the AFRs did go slightly leaner without a cat and needed to be adjusted. It was not enough to worry about and we didn't want to get too technical in the video. But you're right, the fueling was later adjusted to compensate for the slight afr change.

[@bigred8438]

Are you guys in WA?

[@denisdimitrov5051]

It is interesting, how much is the diference of bad smoke gases. Even with catt I doubt this car will get Euro 1 standart.

[@meroj1935]

Your mechanic looks like an older version of Paul Walker😁

[@legoegoman789]

Matters a lot more on NA engines. K20/k24 make an extra 5-10whp from a cat delete, and they only make 200-300whp, so it matters way more then

[@oliverzbinden3762]

I wonder if twin high flow cats would flow enough to not lose power and still do their work 😂

[@brightlife3691]

Clean supra I ever see.

[@z3speed4me]

About to add a 3.5” 200 cell to my car and see what happens… very interested to see the results at semi comparable numbers ~700 wheel.

[@dominikkozela9763]

Hi can you share your results? Was it restrictive and 3.5" inlet/outlet or 3.5" body?

[@jeremyr7147]

Sick, but I'd get that timing belt covered. Something falls in there, flys up from road you'll know it.. The tail light flicker is sick, you gotta admit.

[@jeremyr7147]

7:14 wow it looked like that exhaust cam stopped from the illusion

[@DrInsane76]

Any changes in sound? Is it less noisy with cat?

[@logical_volcel]

hiflow cats are pretty good now so staying legal is always great for worries, but for those of us with pre82 cars that came catless its great, This is 100% better than one video i saw of a cat company running an old 60s v8 up on the dyno cold then installing a cat and making 1 hp encouraging everyone to put it on their cars, if you dont need it dont run it

[@Mr_jz_12]

my car was reg'd as 83 (not sure how, its an 86) and was fine catless? This was in vic though if thats any different? This was a good 10 years ago though.

[@brendanrandle]

1984/5 commodores were still leaded so definitely no cats in them

[@logical_volcel]

@@Mr_jz_12 brendan randle wasn't too sure some cars got cats earlier some later, my 82 mazda was leaded and still has a cat, my 81 one doesnt though

[@allenhawkins1110]

after '86, unleaded was mandatory for new cars. Before then, it was up to the manufacturer what fuel to specify.

[@SupraHenry]

So off topic here but what size exhaust housing is on that turbo? I’m thinking about running it on my car as well

[@StreetFXofficial]

Tbh we might decrease the exhaust housing to make it less laggy. The supra v161 6sp combined with this turbo leaves a big flat spot.

[@SupraHenry]

Street FX Motorsport TV so would you recommend a .82? I assume this is a 1.0 or larger

[@alexgorelov9634]

Wanna see charge air temp. numbers in this video. Noticed the catted run had a big ole fan feeding air at the front vs no fan on catless runs. Or did I miss something? But really in my experience running catless on n/a cars is a waste of a test pipe. On boosted cars your not only looking for rwhp gains, but also less bp on the turbine for those quick spools.

[@StreetFXofficial]

All listed power runs had the fan. We did a couple of other runs without just so we got to record sound clips without additional noise. That fan is crazy loud.

[@c.h.r.i.s2253]

Things have changed so much from the original cats in the 70’s. The cats back then were super restrictive but things have changed while the “bad cat” mindset has remained

[@ElliutN]

At 700+ hp any restriction hinders performance. I doubt it would make much difference on anything under 500hp. Very interesting to watch.

[@boarderboi7]

It's great if you have a 760whp car, but 15hp and 15ftlbs of tourque is a significant difference even in a car with say 300hp, even more if a car had 150-200, and that's usually why people want them gone in budget/grass roots Motorsport. Your guy's build is sick but few of us can actually relate to that much power in a street car. IDK just my .02 🤷🏻‍♂️ car looks and sounds sweet as though 👍

[@StreetFXofficial]

Look at the dyno graph for anything under 650hp... there was less than 1hp difference.. at 300whp you're losing less than half a horsepower.

[@boarderboi7]

@@StreetFXofficial thanks for that, knowledge is always welcome with me. I know I wouldn't say no to 15 extra up top on either of my cars (FB GSL, Hawkeye WRX wagon), but of course neither flow enough air/fuel to make that kind of power anyway. With the WRX though it has a cabin air filter so I've never really noticed the smell of pump gas, but the FB is a different story (being carbied), plus there aren't really heavy emissions penalties here in certain parts of North America that aren't California lol.

[@StreetFXofficial]

It's unlikely that we would be pulled up for emissions testing, but it honestly isn't fun making all my clothes smell like fuel lol.

[@carsandcoldbrew6489]

HFC for the win! Sounds better too

[@jamesgargan4679]

Would like to see it done with a cat-co cat no x -force

[@RadDadisRad]

Did you retune the car for the catless install or did you just use your cat friendly tune in the car for the test?

[@StreetFXofficial]

The car originally had a cat, which was removed for our test. Then the car was retuned for catless (with the test pipe). We needed to make some other tweaks to the tune anyway. Once the new cat went in, we did back to back runs to get the exact power figures without making any changes at all (which are the numbers shown in the video). Afterwards, you're quite right though, because some changes should be made to accommodate a cat. A cat will change AF ratios slightly, so the tune was altered to compensate for this (but not before the results were compiled). The cat restriction also meant we were making slightly less boost (around 0.3psi less). Which in itself could make up for the power loss anyway.

[@vroomvroom773]

No catalyc converters= Less restriction and more horsepower.

[@bigstrawgaming9166]

Apexseals depends on your state laws/tolerance. Here in Florida, just about everyone runs there car cat-less.

[@BladerBP146]

Apexseals the feds will definitely check your car instead of the local cops

[@vroomvroom773]

@Apexseals Don't forget in some states even in my state it's legal and people can get away with it easily. Especially, with states that have no auto inspections. The only way they can get you is in states that have auto inspections.

[@bigstrawgaming9166]

Vroom Vroom 666 exactly, here in Florida, everyone gets away with it lmao. Once I get my tax returns, I’m buying some catless long-tube racing headers from kooks, for my 04 trailblazer I6

[@vroomvroom773]

@@bigstrawgaming9166Awesome👍😀 Same here in South Carolina. We too can go catless all we want. I wish all the best on your trailblazer👍

[@kknocks2378]

A Porsche Cayenne GTS makes about 500hp and has four cats. The factory cats are engineered to treat a specific volume of exhaust gas. If you try to use a factory cat on vehicle you heavily modified, obviously it create a restriction, because the cat wasn’t engineered to treat a larger volume of exhaust gas than what the engine produced from the factory.

[@Kvistkontot]

This test would have shown a bigger difference if the car wasnt detuned before the test. Second, It would be more fun to see the difference on a stock supra, going from stock exhaust/cat to the cat or race exhaust/cat.

[@StreetFXofficial]

We will be running that very test on our A90 supra :)

[@joelhaakana8033]

in a turbo engine its best to run straight pipe to drop backpressure and in a na engine it needs backpressure

[@StreetFXofficial]

Absolutely. We will look to run a test in future with a non turbo car, I expect it would have little to no gain by decatting.

[@coreywildbore7716]

Did you test the back pressure with and without a cat?

[@yadiel1231]

You don’t need back pressure

[@ericalvarez9821]

What happens when you try to do the smog?

[@4BillC]

15 hp is a big difference when the vehicle only make 200hp.

[@tobymobilia4756]

High flow 100 cell cat flow way better then stock

[@4BillC]

@@tobymobilia4756 and straight pipe flows even better...

[@tobymobilia4756]

@@4BillC yeah compare stock cat to straight pipe you will see bigger gain

[@4BillC]

@@tobymobilia4756 unfortunately where I am you have to have a cat to pass the inspection, then it has to pass an emissions test.

[@StreetFXofficial]

Look at the graph at 200hp... there's zero power difference between cat and no cat... that's part of this test. Only comes into play when you're getting to the limits of the exhaust diameter.

[@justinwyatt9048]

Was there a tune change between the two? Because the main reason to remove the cat is to reduce backpressure (which of course hurts flow) - but which also creates more heat and limits how much timing you can put in the tune. If all you did was tune with a cat and then add a delete, or vice versa, what you've done is stuff up your tune. Go back and tune each one for the same afr, but for max timing and you'll find (depending how much backpressure is being created by the cat) you can add maybe 1-2deg more timing safely and get maybe 4-5% instead of 2%.

[@mrnonpc9885]

A third test comparison with a original equipment cat would have been good.

[@RadDadisRad]

I picked up 35whp when I went catless. I went from 360whp to almost 400whp. Small twin turbos on a 3.5 v6

[@StreetFXofficial]

going from a stock cat to no cat is a big change. I suggest to stay legal, and environmentally friendly, and so your car doesnt stink like a gas station, throw a high flow cat like this one in and you'll lose nothing noticeable.

[@cindysue5474]

@@StreetFXofficial Agree here in the states its federal law that you must have a cat.

[@i_am_tinny_man_2267]

Cindy Sue sams as Australia, I think it’s up to a 10k fine in some states.

[@jonathan7744]

@@cindysue5474 Wait federal Law? really? hmmm didn't know that...

[@spankthemonkey3437]

Fukyeahfknoath that's crazy expensive. But I also thought that cats stop global warming guess that didn't stop the warming this summer

[@Fosgen]

About 1.3% more power without CAT. Remember people, you lose some torque on bottom for some power on top. I still prefer no CAT. Eco shit.

[@YyouTTubeE]

i have question. i don't know much about tuning. what's the advantage/purposes of unburnt fuel? if i pay $50 of fuel, i want to use them all, not wasted it. please explain..

[@StreetFXofficial]

it helps keep the engine cool, and safer. Leaner tunes mean they run hotter and closer to the "edge".. Leaner makes more power but likely to detonate and kill your engine. Tuners typically richen the fuel mix up to protect the engine.

[@RJ-sz1kk]

15k fine for 15hp.........i think ill put the angle grinder down now...

[@sethfrancissimracing7558]

$15k fine! Is this true?

[@redtra236]

thought it was $500 but I've never heard of them checking for cats here in Missouri

[@stlchucko]

@@redtra236 From my experience, they only check for cats during an inspection for tags. Technically if it came from the factory with one, it's supposed to have one to pass safety, though it's possible to get an inspector to look the other way. I've had douchebag inspectors before.... Like failing the safety on my 68 Camino because I didn't have a heat riser tube from the exhaust manifold to the air cleaner.

[@Sauhcington]

40 degrees is hot in Australia. Must be nice.

[@nejjc2]

I assumed he meant 40 degrees celsius

[@electric7487]

Celsius.

[@damonlancaster5233]

So 100 Cell CAT is legal in Australia? I am in QLD.

[@tepidtuna7450]

Has anyone ever tried running two small-ish cats in parallel? ie. the pipe splits into 2, goes through the cats, and then joins back into 1 pipe. In electrical circuit design, parallel resistors have significantly less resistance. A cat is a resistor to exhaust flow. Might be able to get big flow this way without needing giant cats that barely fit under the car. I'd imagine 2 3" cats would be cheaper than 1 5" cat? Food for thought.

[@SIKCAR]

Running 2 cats would not be beneficial, the 1st one would have already converted all the molecules from the polluting gas. The job of the cat isn't to restrict airflow on purpose, unlike the purpose of a resistor. It's like running a longer and thinner wire is worse than running a thicker wire. The thinner wire would provide less current thru, and nothing you do after that will improve the flow.

[@sef7992]

@@SIKCAR ^that guy said parallel, not series. Not sure what would happen... but I doubt fluid dynamics and electrical dynamics work identically. Also the billions of R&D $$ spent by auto manufacturers and it's not done in this manner is telling.

[@Liveforeever]

That's a 1.7% difference if all runs are averaged. I wonder if the difference will be even less for an NA engine?