I dont agree. You stated earlier that you had an old classic and had a crapload of HP, but couldnt get all that power to the pavement. Just because you arent going faster on the 1/4 mi doesnt mean you dont have more power. Thats what the dyno results are. I dont know exactly how you would fake a dyno sheet, other than have other mods on the vehicle other than headers. Dont get me wrong, that is possible. I am just saying, for the millions of people who invest in headers, it does something right, right?

Garrett

 

Yes Garrett. Headers are a very important building tool in making a faster motor. However, if you buy a brand new car stock, and slap headers on it, you will effectively receive the same results as if you slapped on a high flow dual exhaust system on a stock motor. You WILL lose horsepower. No doubt, absolutely. Ask any muffler shop.

When I bought my truck and drove it off the lot right over to Midas, the guy told me that I would lose horsepower after installing the flowmaster. And he was right. But if you go to Flowmasters site, they will make claims of gaining horsepower.

Yes, eventually you will gain horsepower from the exhaust, but only after you increase the air and fuel intake.

Same goes with headers. The backpressure on your vehicle must be equal to, in some mathamatical equation, the amount of intake and combustion.

Aftermarket headers on a stock engine will DECREASE horsepower. I don't care what anybody's website says.

The dyno charts don't tell you what other modifications they've done to the vehicle before they installed the headers and dyno'd it. I'm sure it was NOT on a stock vehicle.

Besides, I don't want to install them anyway. They look so delicious, i just want to smear peanut butter on them and lick it off!!!!! mmmmmm.

I know that with running my nitrous, those headers will make a big difference.

As a matter of fact, it says just that in my instruction manual for my nitrous kit. It tells you that installing aftermarket headers will increase the performance of your nitrous application.

I think I'm going to get them. I just wonder if my braces will caught while knawing on them.

Tom

 

I may have had a set back with the SC today...I have to call, but it sounds like crap and Im extremely POed at the moment. I will come back to FTE after I can make this phone call.

Garrett

 

That sux! What happened with it? I'll give a size ten to the nose if they give ya a hard time!

ps: if you get the SC, give me your intake?

 

Garrett, did you check out that site on superchargers i posted for you?????

The site states all kinds of numerous problems with superchargers and that they require constant maintenence.

Not only that, but they don't install them on 4.2's very frequently so you may even run into additional problems.

Maybe not a good idea??????

I think you should just spray it!

Tom

 

As a little aside, I find the whole subject of exhaust gas flow (from the standpoint of flow dynamics) to be pretty interesting. I believe there is a lot of misconception on the whole subject of backpressure and exhaust gas flow.

About 1.5 years ago....well....here's a link.

https://www.ford-trucks.com/forums/s...2Bbackpressure

Get yourself a big cup of coffee...it's a longgggg thread!

Also, try: http://www.nsxprime.com/FAQ/Miscella...cellaneous.htm

click on exhaust theory

 

Hey Brian,

Nice post. I have a comment regarding your last paragraph,

"If backpressure REALLY helped, top fuel dragsters, NASCAR, Indy cars, etc, would all have some sort of "restrictive" device added to increase bacpressure by reducing gas flow rates. They do not use such a device. They all run OPEN exhaust, TUNED open exhaust systems. "

As we are talking about stock vehicles here, there is a difference between a stock motor and an Indy race car.

I don't know the mechanics of it Brian, however I have read about the energy pulses and so forth.

I do know this much though.

On most new motorcycles, especially Yamaha's, in the exhaust under the bike hidden by plastic, is a valve. This valve remains closed for the most part. It remains closed in order to create back pressure. Honda's new bikes also have this same valve.

As you increase throttle, the valve begins to open but only slightly until your WOT. The purpose of this valve is to create back pressure which gives the Yamaha R1 an extremely high torque output.

If you replace this portion of the exhaust with a full race system, you will lose so much power that the bike will barely be functional.

This is a fact, as many of my friends have experienced this and have re-installed the stock setup with just an aftermarket slip-on instead.

This valve is called the EXUP valve. And has been on Yamaha motorcycles for 20 years.

Check it out http://www.yamaha-motor.com/products...cy&cid=5&mid=6

So, although to some degree in high performance situations that an open exhaust is beneficial, on a stock motor it is definetely not. It's easy, just ask any muffler shop and they'll tell you.

Be it called back pressure or some other scientific name, whatever it is called, you NEED it on a stock motor. Don't ask me why, you JUST DO, and that cannot be argued.

Ask your Ford dealer, ask an muffler shop, ask any Chevy dealer, ask any motorcycle manufacturer, you can pretty much ask just about anybody and you'll come up with the same answer every time. On a stock motor, you need it.

Drop the EXUP off a Yamaha and lose 40 horsepower and you'll see.

Tom

 

Also,

Another way to prove myself. Certainly you must know of someone who is fixin to buy a new truck.

Be there when he does. Then pay 50 bucks to have it dyno'd.

Then drive the truck over to Midas and have a flowmaster 40 with larger diameter pipes installed.

Take it back and have it redyno'd.

I'll bet 500.00 of my hard earned dollars that he just lost 20 ftlbs of torque.

Because that's what I did with my truck. I bought it new, drove it drove it for a day, took it to midas, had the flowmaster installed, the guy at the shop told me i would lose power, after he installed the system, i got in my truck and immediately noticed a loss in torque and horsepower.

Same on my motorcycles, That's why I don't install full race systems anymore, because you lose horepower. I just toss a slip-on for looks and sound, and I still lose a little torque.

Tom

 

Brian,

That thread was great reading. I’m firmly in the camp of “backpressure is bad for performance.” You just cannot logically argue against a good free flowing “tuned” exhaust system.

Ron

 

I think Brians whole point is that the vehicle is tuned for open though, Tom. You could run straight pipes, and gain crazy HP, IF its TUNED. Which I notiecd is how Brian wrote it. I agree with that 100% Now, if you are running that with NO tune, then I am 100% in agereance with you, Tom. This is my theory, and what I have ALWAYS done. If Im going to get exhaust, I already have an intake on order. You CANT do one without the other, like marriage. Now, if your vehicle is TUNED for an open exhaust, then theres no way you can argue that it will lose power. I think you two were talking about different items. So I agree with you both.

Thanks for the post Brian.

Garrett

 

I agree Garrett.

Case closed.

Tom

ps.

I'm stopping at publix to stock up on that peanut butter

 

Tom
At idle and part-throttle, when exhaust volumes are low the EXUP valve closes down, which effectively re-tunes the pipe for efficient exhaust scavenging at low RPM. When you nail the throttle and RPM’s come up, the EXUP opens and the engine sees a large-diameter free-flowing exhaust which gives you efficient exhaust scavenging at high RPM. This effectively nets increased power throughout the rev range. Pretty slick. Too bad they don’t make something like this for our trucks.

 

I agree Sigma.

The Exup apparently works so well that Honda has adopted it also. They should test it on cars as well.

Tom