i have a question for someone who knows their low end power. i have been told by numerous members to go with exhaust, air intake, and then a chip. i need exhaust info though.... i'm thinking about getting flowmaster 40 series DI/DO. what size pipes should i use and tips so i dont open the exhuast up too much and loose low end power??? help please!
thanx
JP

 

Silver......I'm no engineer but I've read about 300 posts from this and another board over the last week or so on this very subject. From what I can tell (and by what the manufacturers web sites claim) low end power, i.e. torque, is not decreased by using a DO exhaust...at least not either Flowmaster Force II or Gibson Dual Sport. It is actually increased though not as much as with the SO setup. I actually spoke to a Gibson tech today comparing the SI/SO Swept Side vs. the SI/DO Dual Sport and he said the SO should result in approx 25 ft./lbs extra torque whereas the DO setup may only reach 15-20. So either way, there is an increase it's just more in the SO configuration.

BTW....the SO uses 3" pipes and the DO uses 2.5". In a dual out, you would lose to much backpressure resulting in even less of a torque boost and perhaps, possibly even a loss.

Hope this helps. Good luck.

Natty

 

What?? tell me more about the loss. i dont understand. if i get smaller pipes i loose more backpressure?? help
JP

 

I think what he meant was if the dual out used 3" pipes, you would end up losing low end torque. Low end torque actually requires some back pressure but too much is bad. I called gibson and they stated that the so is the best for performance enhancement.

 

are true duals with an X-pipe better for torque than a SI/DO?

 

Sorry Silver...I wasn't too clear at the end of my last post. Basically, as XLT was nice enough to clear up, if a DO used 3" pipes, there would be too much back pressure loss, thus torque loss. That's the reason for the 2.5" pipes in DO.

Natty

 

Just FYI, you do not want back pressure. Gases expand to exert equal pressure on all surfaces. As a gas expands, it cools. As it cools, it becomes more dense. As the gas becomes more dense, it slows in it's momentum.


For a longer explanation, click the link.

Exhaust system

 

Great link Sidewalk with good info. Your point is well taken. Having said that, everyone i've spoken to re: cat-backs for the Triton engines (manufacturer techies included) all say those engines need a certain amount of bp. Surely, the cat converter alone will provide some. I guess, as you stated in your linked post, one must decide if they want the power at the mid to upper rpm ranges (if I'm not mistaken, that would mean a more open exhaust) or if they want the low rpm, off the line sort of push (which I think would be a more restrictive exhaust) say for towing, hauling or stop light to stop light sort of stuff.

Good info, thanks again.

Natty (ain't this great stuff!)

 

Since I did not mention cats in that post (VW's didn't use them much), I will say it here.

Removing the catalyctic converter will improve performace all around. However, the problem is if you hollow it out. If a converter is hollowed out, it will act as an expansion chamber. It would be like placing a 5" diameter pipe a foot or two long in the system. The open area will allow for the gas to expand, and, well, you get the point.

But a cat is a neccesary in todays modern pollution controlled cars for the reduction of CO and hydrocarbons. Damn the luck.

 

I'm not sure I get this exactly. The whole gas expansion thing, does this mean that BP all has to do with the pipe size and not the actual restriction? This would explain the cat convertor thing but I know that taking the cats off a triton and running straigh pipes, even if they are small, will decrease low-end. can you explain this?

 

Sidewalk....sadly, the cat converter is here to stay (at least if you want to pass motor vehicle inspections). I miss the pre-cat days...remember them well. Think I'll break out the old pics of my 69' Mach 1 and '68 Torino Hurst GT and reminisce. :-) Thanks again for your very technical and proficient analysis.

Carman....I'm sure Sidewalk can do an infinetly better job than I at clearing up the issue. I'm a "hacker" so to speak whereas Sidewalk sounds like a pro.

Natty

 

Pro, I wish! Do to the availabilty of message boards like this, I have learned a great deal. The exhaust size thing was explained to me by someone on the RRORC boards. Unfortunetaly, I have to run a cat as well. Does your inspection include a "sniffer" test? Some places just look to see if a cat is on there.

CarMan - As far as the Triton issue, I would assume that it is related to the computer. Back pressure is related to both restriction, and pipe size. Too small a pipe, too much restriction, to much pipe, and too much restriction.

 

Yes, NJ has one of the most stringent auto inspections in the country. Probably second to Califormia. The leave the sniffer in the pipe for a good 10 minutes. Ten minutes doesn't sound like a long time but when you're waiting and the line behind you is looooooooooong, it seems like an eternity.

Natty