KrazyKat

Anyone do it and dyno before and after results?

Not looking for speculation, just actual experience with it on the Genesis 2.0T.

Thanks!

flylow

But why??? This is more bad than good u know that right?

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6MT FTW

+1

Hollowed-Out Catalysts - Power Increase - Import Tuner Magazine

KrazyKat

The speculation just adds clutter. Experience on the Genesis 2.0T only please.

The import tuner article does not deal with close coupled cat to turbocharger's, like we do. I know for a fact there is a substantial gain, as spool is nearly 500 rpm faster, and overall response is much improved. Just looking for those who have actually done it, and perhaps dyno'd their cars before and after.

BKED

orrrrrr buy test pipes?

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Chuckie

For the time spent to do this and exposure to a known carcinogen, I think buying one of the many aftermarket parts is a better route. Yes, there will be power gains, but not more than a full replacement part would give and they aren't that expensive.

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2012 Hyundai Genesis Coupe 2.0T - ARK, HKS, K&N, RMR | 2009 Mazda 6 GT - Injen, KSport, Rotora, TSW |

KrazyKat

Its already done. Many reasons for doing this, where I live. Trying to maintain as close to stock underhood appearance as possible. The gutted secondary and stock downpipe are being replaced by a 3" downpipe with a Magnaflow metallic core cat welded in, with the secondary o2 sensor after (pigtail extended). The idea is to pass any kind of random visual inspection with ease. The gutted primary cat is remaining in place, with my WB o2 in hole 2, primary o2 in hole 1.

I keep asking for no speculation because its already done, and Im well aware of the alternatives. Just looking for an actual dyno chart, out of curiousity. Test pipes and high flow primary cats dont pass visual here, not when a LEO or other EO pulls a suprise inspection on your ass.

Call it 'sleeper'.

Suns_PSD

I'm not aware of any dyno results on the 2.0 but it has been proven on the 3.8 that cat deletes loses significant power accept at very peak rpm.

Sent from my SGH-T959V using AutoGuide.com App

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Chuckie

I've gotten stuck in the random roadside emissions checks here in CA. Running a hfc in the downpipe is a good idea.

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2012 Hyundai Genesis Coupe 2.0T - ARK, HKS, K&N, RMR | 2009 Mazda 6 GT - Injen, KSport, Rotora, TSW |

Snoopy0812

The 3.8 loses power because you're freeing up the exhaust and removing back pressure, something the car has to be tuned to compensate for. NA engines are usually very sensitive to back pressure changes. Turbo'd cars however usually get their best gains if there is only about a 12" exhaust post turbo and the wastegate dumps to atmo rather than into the exhaust. This however is illegal in I'd say.. everything except offroad (ie on a track).

As for the OP.

Gutting the cats will affect you negatively. What you're doing is actually increasing back pressure which causes resistance on the turbine which lowers fuel economy, increases lag and lowers peak boost (increased backpressure with increased exhaust flow).

Why?
This is because of what happens naturally in a cat. The reason cats are fatter than the rest of your exhaust is because they have internal volume being used by the catalytic material, to compensate for this usage they increase the size of the containter, optimally, your increase in exhaust chamber = the displacement of the catalyst. High flow cats do this at a near 1:1 ratio where as stock is about a 1.6:1 ratio, a tad more restrictive but better for the hippies.

When you remove the catalyst but keep the exhaust housing the same size you increase your chamber volume and turn it from a slight restriction to an expansion chamber. Once the exhaust gasses have been allowed to expand and cool it requires energy to compress them back into the smaller exhaust tubing. That energy comes in the form of restriction on your turbine. More restriction on your turbine means less scavaging which means your cylinders are double pumping exhaust, lowering efficiency and power.

The purpose of the test pipe is to maintain the exhaust piping volume when removing the catalyst there by negating any negative effects. Small performance increase would be seen as the restriction would be less, though in reality on the Genesis Coupe 2.0T we're talking about maybe 2-3hp.

If you're wondering about how much hp you've lost by gutting your cats, you could be looking at about 3-5whp for one cat, and a grand total of about 10whp for both (primary cat is located very close to the turbo and it would increase turbulance in the exhaust flow, further reducing power). I'd hazard a guess at appx. the same amount of torque lost too.

If you want to know your changes, you should have dyno'd your car before you gutted them and then dyno'd again after. Few on this forum would ever dyno their car for something that minor of a change on their car, most don't even dyno their cars for full builds.

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flylow

errrmm... fake cats... theyre cheap and they fool anyone...

http://www.siliconeintakes.com/produ...roducts_id=572

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Chuckie

For the gutted cats, I've always inserted a straight pipe inside to remove turbulence. However, my state has roadside e-machines, so visually, fake cats won't work and the machine will screw me either way. HFC is the only way to go.

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2012 Hyundai Genesis Coupe 2.0T - ARK, HKS, K&N, RMR | 2009 Mazda 6 GT - Injen, KSport, Rotora, TSW |

KrazyKat

Holy smokes, how many times must one ask for no speculation? Snoop, backpressure is never desirable, the goal in an N/A setup is minimum backpressure, and maximum flow velocity, to assist with scavenging. A turbo car needs neither, post turbine.

Shouldn't have asked the question.

KrazyKat

Same here, but this platform's primary cat is a little tricky.

2012-Rspec

Wow sounds like a lot of you guys live in nazi Germany. Sniffers? Random inspections? Wtf

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AKGC

Ummm. IM testing. I can assure you, California is more nazi, when it comes to emissions and modding engines legally, than germany is.

csu87

You keep asking for no speculation, yet you are speculating that what people are telling you is wrong? Since you already did it, why dont you go jump on a dyno?

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Snoopy0812

Sorry, if you can't adjust fuel you shouldn't reduce back pressure from stock. It's just a scientific truth, which is you re-read my comment you'd see that I said you'd need a tune to compensate.
This is a fact that's been proven by many 3.8 owners on this site.

Back to your question, I answered it for you. Don't expect gains, expect losses. The only one on this ENTIRE site that can give you the answer you're looking for is you. Fact is most people on this site believe gutting cats is for ricers. So post your pic up in our local rice thread.

For anyone else who'd interested in dyno comparison of stock/gutted cat/test pipe.
http://www.importtuner.com/tech/impp...ct_or_fiction/

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JewishThunder

Calm snoop Calm. He does have plenty of ways to adjust fueling to compensate for his added loss of backpressure. He has a cmd with a return line setup.

He will see a quicker spool up most likely but it won't be anything earth shattering though. Maybe 200-300rpms quicker just because you're only taking out some back pressure but you still have the restriction of the stock size piping.

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KrazyKat

All that was asked in the original post was whether or not anyone had dyno'd back to back. Amazing the different answers that come back, for a question never asked.

The import tuner article has absolutely ZERO bearing on the stock 2.0T primary cat situation, and turbo cars in general. Cats directly after the turbine are a big no-no, when it comes to performance. Yes, there was a ~500 rpm spool improvement GUTTING the primary cat. No other changes. Yes, there was a definite power improvement. All that is being asked here:

HAS ANYONE DYNOED BACK TO BACK?