Hey guys.
Did I tell my buddy an untruth this morning?
He got the Stage 3 dealer installed 114” kit installed the other day.
We were talking se8-498 cam dyno results and the Stage 3 is on the HD site being approx 110 decent horsepower. Other posted results on the forums are a lot less.
The cat topic came into play and I said de-cat has little to do with flow or numbers. Mainly a nicer throatier sound and reduced heat.
Bottom line, does the cat make a difference on dyno with or without at this level of build?

 

Ever see a dragster with Catalytic converter on it? Of course they decrease power.

 

Performance of any motor is a matter of air flow; Catalytic converters restrict the amount of air flow passing through the exhaust, so no matter how much air/fuel you put in, if it cannot be discharged via the exhaust the engine will suffer in performance.

Tuned headers provide a balance between flow, with enough back pressure to maximize the combustion cycle...cats restrict the out going air flow to the point that your motor must run very lean, thereby reducing its potential.

 

the new Corvette seems unaffected by emissions requirements...just imagine if it didn't have to be handcuffed by them...damn, we could have 1000 hp street car! LOL

755 horses and 715 lb-ft of torque

 

Pretty sure I've seen some dyno sheets from a couple of vendors that showed that the stock header without the cat only gained like 1 HP/TQ.

 

I wouldnt be surprised. And if I recall correctly, a few years ago there was someone that actually *measured* the air flow, stock vs no cat, and there was not a significant difference. Wish I could find that post.

 

We will see that number over 1000 with the cats in place once the aftermarket gets a hold of it. The cats aren’t always a “bad thing” you have to understand how they work, it’s not about restricting flow (which they do to a certain degree) it’s about how they actually reduce carbon emissions with the design and material contained within. Engineers have done an outstanding job with flow characteristics over the years. To the point that some cars/trucks/ bikes might see a decrease if the cat is removed.

Or

What we are seeing on the M8, it looks like removing the cat is really just changing the sound with very little increase or decrease in performance.

 

What we have found in testing the M8, is on a stock bike removing the cat doesn't do much of anything. Now start increasing the performance and it will have an effect. At about 90 Hp and up it becomes a problem. A perfect example package would be a Stage II type. We see about 95Hp with our torque package but remove the cat and re-tune we see 99 Hp. The further up in power you go the more and more of an issue it becomes. It's a much better cat setup then what was on the Twin Cams.

 

Early catalytic converters were very restrictive. Newer cats are far superior.

 

That’s what I thought except I can’t find any confirming that