So removing cats reduces restriction so that means less boost/less power on a supercharged car ?

[Unas2k5]

I was just wondering because I’m reading conflicting information. So basically, you make less power if you remove your catalytic converters?

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[Joshinator99]

I was just wondering because I’m reading conflicting information. So basically, you make less power if you remove your catalytic converters?

False. With your supercharger running the exact same pulley combo, less “boost” means you’re now moving the air with less resistance. In other words, the engine is now more efficient at being an air pump. This allows you to spin the blower harder and make more power at the same boost level. It’s all about moving air…not boost…boost is just the level of restriction.

 

[jpjr501]

Less resistance equals more power especially if you have stock cats which shouldn't be run with a supercharger. They are only rated to like 460hp.

 

[robvas]

If you lower the boost by going to a larger pulley, you will lose power. If you lose boost by making your engine breathe better, you will gain power.

Removing cats will only make you lose like a half a pound anyway.

 

[Unas2k5]

Less resistance equals more power especially if you have stock cats which shouldn't be run with a supercharger. They are only rated to like 460hp.

I had high flow cats but I removed them to prevent detonation. So I figured I would make less boost and that would be less HP. I was thinking that I should go to a dyno day to see how much power I’m making now.
Also you know how tuners tell you that on a coyote you can’t have more than 10-12 PSI on 93? If everyone’s boost level is different and that nets a different power outcome as well then how can they use such an inaccurate number to gauge this ?
So basically I can have 10psi on 93 using a 4.0 blower and get 1000hp but if I’m using a smaller blower I’m still limited to 10psi and just making 600?

 

[jpjr501]

I had high flow cats but I removed them to prevent detonation. So I figured I would make less boost and that would be less HP. I was thinking that I should go to a dyno day to see how much power I’m making now.
Also you know how tuners tell you that on a coyote you can’t have more than 10-12 PSI on 93? If everyone’s boost level is different and that nets a different power outcome as well then how can they use such an inaccurate number to gauge this ?
So basically I can have 10psi on 93 using a 4.0 blower and get 1000hp but if I’m using a smaller blower I’m still limited to 10psi and just making 600?

They should probably use HP rather than PSI when discussing cats and fuel. I got told the same thing, I wanted to run pump gas but my tuner said you're making 11-12psi so with high compression it's not ideal. They probably say that so they are not liable if you get really crappy pump gas and get knock. For them it's just easier to tune when things are happy. I'm already on a big 120MM pulley but making over 750. I don't have cats.

 

[robvas]

So basically I can have 10psi on 93 using a 4.0 blower and get 1000hp

That will never happen (on an anywhere near stock engine at least)

 

[jpjr501]

That will never happen (on an anywhere near stock engine at least)

Of course, it was satire on how these tuners evaluate boost levels and not being specific of the combo.

 

[Unas2k5]

They should probably use HP rather than PSI when discussing cats and fuel. I got told the same thing, I wanted to run pump gas but my tuner said you're making 11-12psi so with high compression it's not ideal. They probably say that so they are not liable if you get really crappy pump gas and get knock. For them it's just easier to tune when things are happy. I'm already on a big 120MM pulley but making over 750. I don't have cats.

Ok I see thanks for clearing things up. I’m on 9.5 compression and I have a 4.25 pulley that’s about 10.5 PSI. I’m thinking of going to a 4.0 pulley I’m just not sure how low I can go on 93 right now. I do run a 3.5 pulley for E85 that was 21PSI 853Whp

 

[Unas2k5]

My 4.75 pulley gave me 7.75 psi and 4.25 gave me 10.5

 

[jpjr501]

Ok I see thanks for clearing things up. I’m on 9.5 compression and I have a 4.25 pulley that’s about 10.5 PSI. I’m thinking of going to a 4.0 pulley I’m just not sure how low I can go on 93 right now. I do run a 3.5 pulley for E85 that was 21PSI 853Whp

Ah, in your case with low compression you have that ability. For stock motor Coyote's, me on a Gen3 with 12.0:1 compression we are much limited. I'd be able to make 850 on a 110MM pulley but not ready for that yet. Tuners say we are pushing it over 15psi. I saw 18psi on my boost gauge once, it was the hardest rip I've ever felt in my car. The weather just happen to be perfect and I had E90 in the tank. When I saw the video later and saw it the gauge, I was was freaking out.

 

[CrackedHorn]

Engine is an air pump. The more air it can flow (or the less restrictions there are) the less amount of boost (force) is needed to pump the same volume of air.

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