on an otherwise stock engine? I have no pre-cats or cats and this would possibly be the next mod for the car. I dont know what benefit they would give in the short term. Any comments??

Thanks!

 

Since you're already not passing emissions you might as well install a set of long tubes and remove all of the AIR plumbing from under the hood. Not only will you pick up 10-15 hp and a lot of mid range torque you'll also clean up the engine compartment a whole lot.

In theory they can improve your gas mileage as well if you don't drive it any harder, I wouldn't know.

One more thing, you'll probably want to disable the EGR function in the computer, otherwise you can have some prooblems after you remove all the AIR plumbing.

 

It's an expensive 10-12 hp. You'll also get a different exhaust note.

 

It's not really that expensive if you consider what it gives you. True it only gives a PEAK of 10-12 horsepower, but that's not all. The problem with peak numbers is that they are very misleading. You can make 100 pounds of torque and suddenly have a spike in the high rpm's and still have high peak numbers in a dog slow car.

You have to look at the torque curve, or more importantly the area under that curve. You can increase your mid RPM torque and do absolutely nothing to your peak horsepower. This still makes the car faster because you have increased the horsepower at a point other than the peak. How often are you really at the peak anyway?

Here are my dyno graphs to illustrate that point. Here is my car bone stock, notice the flat torque curve?



Now here it is after the cam and rockers, etc. Still on stock heads



Notice the torque curve is still very flat. The torque peak only increased by 12 foot pounds. This means that for seat of the pants you don't feel much of any difference for daily driving. Sure I picked up 44 horsepower, but it's all on the top end, beyond where you drive most of the time. Yes the car is certainly faster but it doesn't really feel that much faster until you go beyond where the engine used to rev.

Now look at this graph, after the headers / x-pipe / flowmasters. The peak horsepower is a little bit higher, but look at the torque curve.



That spike in the torque curve equates to a huge increase in the feeling of speed. Also, since horsepower is directly linked to torque you'll notice the horsepower curve is higher through the mid point as well.

I'll agree with you that 10-12 horsepower at the peak is hardly worth $600-700, but you get so much more than that. It's just so easy to get caught up in peak numbers that we can sometimes look at things in the wrong light. That's why I love the dyno, it's the ultimate B.S. detector. There's just no good way to say what headers do for you without drawing a picture. Oh, and they will also enhance the affects of any other mods you do later.

:cheers:

 

Youll pick up alot of mid-range and top end HP, that is the torque and HP integrals will be bigger, but only a peak of 10-15hp.

Plus it will be louder by quite a bit depending on the catback, and youll likely run into a little more resonance, again depending on catbacks.

 

Equal length headers should give you better exhaust scavenging, so you can cram more fuel into the cylinders = mo powa!

But most of all, they sound cool. :reddevil

 

Thanks everyone, I didnt think it would do much more than 15hp, but I didnt expect an increase across the midrange. Would there be any effect on the low end? (the cats were removed before I bought it) Comparing to other vettes that still have the factory exaust, my bum dyno tells me that I dont have the same low-end power as stock.

 

On the low end, its possible that you might feel less UMPH off the line, but thats very minor.

But since you have a M6, you might not notice it as much as somebody with an A4.


[Modified by vader86, 8:13 AM 3/12/2003]