HP Gain From Just Adding High Flow Cats?

[Vipuronr]

Looking to do mods slowly and curious, after listenting to the RT hi-flow cat change, what kind of hp increase you get if you keep the stock exhaust.

Just keeping all my opinions open at this point.

Thanks.

Peter

 

[dave6666]

Here is an oldie but goodie in regards to mods and power.

According to this list, HF cats on a 3" cat-back are worth about 5hp.

http://forums.viperclub.org/performance-modifications/521912-power-upgrades-ordered-list.html

 

[Vipuronr]

Thanks, very helpful perspective...even if it is old, it does show the relative gains for each basic mod.

Btw, do most move to a 3" cat-back system with stock car or stay with stock 2 1/2." And, other than the increase in flow, what does 3" do? I recall that sometimes, if you went to larger diameter exhaust without making certain mods, it actually reduced the hp of the engine.

Thoughts?

Thanks.

Peter

 

[Russ M]

The reason to delete cats is not a power boost, but rather a fix for something that ruins enjoyment of the car.

When you remove the cats, side sills become normal temps, foot wells become normal temps, and your paint no longer changes color on your side sills.

 

[dave6666]

Without being too scientific here, as I do not have personal dyno experience on the topic, but yes there is a relationship to hp and how the air flows through an engine. That relationship goes all the way back to the cam, and if the pipe is too big you can upset the relationship of all the components and lose power. Since I have not studied that and I doubt others have spent tons of time on it, you could make your judgment call this way:

Stock exhaust...

-> Some just want their car stock. Period.
-> Some may not want additional sound.
-> Factory designs are typically conservative. I mean, look how much power you can get out of that engine just doing N/A airflow mods.

Cat-back exhaust...

-> Somewhere, someone (or many...) have done the testing. Just look at the number of people that have done this mod. Can't be that many dumb people.
-> Really enhances the sound.
-> going from 2-1/2" to 3" pipe is not a major change. I've heard of at least one with 4" pipe. I would suggest that size to be verified for power gains.

So my bottom line 0.02 on a cat-back is, just do it...

 

[mjorgensen Woodhouse]

I have seen a decrease on midrange with the cat delete, you will gain a small amount on the top end but for me it was not worth the trouble and smell.

 

[Tom F&L GoR]

Depending on where you are in NY or CT, you will need the cats to pass inspection.

 

[dave6666]

I have seen a decrease on midrange with the cat delete, you will gain a small amount on the top end but for me it was not worth the trouble and smell.

Depending on where you are in NY or CT, you will need the cats to pass inspection.

I don't think he's looking to delete the cats. He's looking for high flow cats and possibly a cat-back system.

 

[Vipuronr]

Yup Dave....not looking to delete cats, just maybe go to a better flowing cat setup. Was just curious about the difference between changing just the cats and going the whole route of cat-back. I do not want to go for headers, as for me, it is just not worth the additional money.

Thanks very much.

Peter

 

[JonB]

I have seen a decrease on midrange with the cat delete, you will gain a small amount on the top end but for me it was not worth the trouble and smell.

I agree with Mark.................and despite the fact that dynos and common sense and SOTP can suggest that you have gained a few HF cat HP (5-10 HP, year and mods matter) it is very difficult to Repeat-Provably that you gained just 1.5% HP on a dyno. Accuracy is only 98%.

In other words, on a 500 HP motor, it is hard to prove 7HP

The COOL TEMP is a FREEBEE!!!!

 

[Vipuronr]

Okay, thanks all...looks like that is a smart mod regardless of hp increase. Should add a little to the sound of the car as well.

I'll add it to the list of upcoming things to modify.

Appreciate all the input.

Peter

 

[chimazo]

Since you're going to have to cut the stock exhaust to install the hi-flo cats, why not do the exhaust, too? Better sound and better looks, too. I went with the 2.5" because that is what the stock manifold downpipes were, then bolted on a Borla exhaust with it. FWIW, I went with the 2-muffler, 2-resonator Borla and it is PLENTY loud. Even with the cats, my sills are never hot to the touch.

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[Vipuronr]

Nice!!!! Thanks.

Hey, still undecided, as the hot door sills make a great grill for parties, lunches, get togethers.....cooks hamburgers and hot dogs lickedy split!!!!!

Peter

 

[eucharistos]

Hey, still undecided, as the hot door sills make a great grill for parties, lunches, get togethers.....cooks hamburgers and hot dogs lickedy split!!!!

not to mention the cool viper brand you and the wife get on your calves

 

[RTTTTed]

My last GTS had Roe Hi-flow cats and Random Tech 3" catback. With the only changes being Roe 8# sc, w/m, filters and smooth tubes it dyno'd 598rwhp/644rwtq. Waaaay too much power for the runcraps I used on it. Sound was awesome. Loudest when idleing and slightly more than stock loudness cruising and WOT.

My present Roe GTS has well over 720rwhp with a 10# Roe, headers, cat delete and Corsa track exhaust. Other power mods, but the sound is LOUD and good. Cruising and off is the only times this Viper is quiet. And I'm lovin' it.

I can place my hands on my side sills. I've seen 2 cars that had fires because of the side sill heat. Personally, I think the cause was too lean or plugged stock cats, but ... I wouldn't take a chance that my baby (wife or car) could burn because of the "choker" cats. Change 'em.

What year is your Vipe? If it's a 96 with the cast iron exhaust manifolds you should at least change over to the Gen 2 stock headers. If your car is a 97 it came with the GTS headers (Gen2). I have a set for sale in the classifieds.

Ted

 

[Vipuronr]

Thanks Ted. Its actually a '98, so it has the later (Gen II) headers. Its sounding like the hi-flow cats is the necessary change and something I should look at doing soon. Next time I talk to Chuck, I'll see what I'm going to be in for.

So, I have heard about Roe and Random Tech for hi-flow cats. Are there others and what is everyone's opinion about which is better....or are they just basically the same and you buy Sean's to support his move. Seriously, is there a difference in sound and possibly power?

Thanks all.

Peter

 

[eucharistos]

I have heard about Roe and Random Tech for hi-flow cats. Are there others and what is everyone's opinion about which is better

here is a good thread, there is another, (many others) i'll post if i can find it
http://forums.viperclub.org/rt-10-gts-discussions/608580-roes-cats-vs-random-techs.html

 

[Vipuronr]

Thanks, helpful kind of, but almost makes me want to stick with the stock cats...except for the heat factor.

Peter

 

[eucharistos]

except for the heat factor.

Down here, the heat is a big factor about 11 1/2 months a year!!!

 

[viperdude118]

The bottom line here really is just how many times do you want to have to remove the side sills and then put them back on? Unless your Dave6666 who's a self proclaimed expert at taking them off and on, they are kind of a pain. You might as well just do the exhaust the way you want the first time, which might include the headers and catback and not have to mess with it anymore.

 

[RTTTTed]

Thanks Ted. Its actually a '98, so it has the later (Gen II) headers. Its sounding like the hi-flow cats is the necessary change and something I should look at doing soon. Next time I talk to Chuck, I'll see what I'm going to be in for.

So, I have heard about Roe and Random Tech for hi-flow cats. Are there others and what is everyone's opinion about which is better....or are they just basically the same and you buy Sean's to support his move. Seriously, is there a difference in sound and possibly power?

Thanks all.

Peter

At VOI X I checked out the Corsa "muffler". Amazing! The exhaust pipe goes straight through the "muffler" and the only holes are a couple slots that allow some exhaust into the multi chambered outershells. The tone and sound comes from Sound deadening technology to change the sound/frequencies that you hear. The material of the pipe and components as well as the length and diameter all combine to give YOUR cars sound.

I've put three vids on YouTube - Broadcast Yourself. so that people can hear the different sounds of the exhausts. Search Viper and Corsa, Random Tech, exhuast, burnout, etc. and that may help with your choice. Just having a rear exit exhaust makes a big difference in enhancing your exhaust sound.

Ted

 

[Vipuronr]

Thanks Ted and everyone, I found this a very helpful discussion for me. Since I am fairly new to Vipers (bought mine in June), I am still learning alot of the ins and outs of the car. Having been at the great OCC event a few weeks ago, I could hardly hear my car, as just about everyone elses was drowning me out. Not that I want the loudest, but did really like the sound of a number of Gen II's I was near. Surrounded by Gen III's, the only way I new my car was running was because it was moving!!!

My objective is not to have a heavily modified car, as with two young children its a matter of priorities. Given money no object, I would definitely go for a ROE SC and all that goes with that type of mod. But, in the real world, looks like exhaust change maybe the biggest thing I do.

Again, thanks for all the great insights.

Peter

 

[Vipuronr]

Ted, just heard your car.....yup, loud, but sounds really great, love the idle sound.

Peter