has anyone taken back pressure readings of the factory exhaust? I am getting ready to get a bung welded into my exhaust ahead of the cats (for a/f readings) and figured while I am at it I might as well get my dual magnaflow setup tested. I would like to compare it to a factory reading to see where it stands......Anyone wanna help??

Andy

 

i cant help but i can ask for more info
first of all whats a bung? second i have flowmasters on my truck which i wanna change eventually but for now they are ok. anyway somone once suggested to me the backpressure of the flows was either too much or too little[dont remember] and that is why my engine blew. now i didnt believe that and am almost sure it wasnt the cuase but as some of you know i have a new engine on order and dont want to **** this one up because of my exhaust. so basically should i be ok with the flowmasters? not too much or too little backpressure?

 

as for the flowmasters, I would assume that people think that they create too much back pressure. A bung is like a tap. It give you a point to do things like add o2 sensors or in my case tap in to get better a/f readings.

Andy

 

what are you going to be using to read the a/f? got a link? sorry for the stupid questions

 

it's for dyno tuning. They have the a/f equip there. Instead of them sticking it up the tail pipe(hahahahah) they can tap in ahead of the cats for better readings

 

oh i get it, is just for more accurate readings?

 

That is where the saying "bung hole " came from. Wooden kegs of beer and wine had a hole in them and they put a bung in it.

 

Backpressure is a term that has been given a very bad meaning by alot of exhaust companies for quite some time. Our engines are tuned to have a certain amount of pressure delay between when the exhaust pulse exits the cylinder and when it hits the O2 sensors approximate area. This length of time is pretty critical. Reducing this amount of time by installing an exhaust system which speeds the gases flow or rather, not slowing it enough, without compensating via the computer programming will throw your vehicle into a poor state of tune (at the least) or can even lead to the MIL light (check engine soon) coming on.
A Flowmaster muffler deals with this situation very uniquely. Initially, there is a slowing of the gasses as they pass around the chambers. Then there is a rapid accelleration of the gasses as they fill the void left by the pulse ahead of them. By the end of the muffler, the overall 'drag' through it is actually less than the initial restriction in front of it. This is a hard concept to grasp, and a harder one to explain. One must be familiar with airflow dynamics and pressure differentials in order to get the full understanding of how they work. But they do work. And they are the only muffler that effectively deals with these air pulses. The air that comes out of your engine is not steady state flow like a flowbench. It is pulses. The flowmasters didn't cause your engine to blow. I have yet to see a vehicle (and I've witnessed literally hundreds of dyno pulls) that didn't make more average torque and more average hp than with a properly set-up flowmaster system. And they all got slightly better gas mileage, too. But some folks don't like the sound they make, or they've had bad experiences due to poor installation or tuning so they kinda get a bad wrap. They also aren't the best in snowy climates, as the steel tends to rust. So to reply to the guy asking if Magnaflows will reduce the backpressure more than his stock muffler, I say yes- to a small degree. Is that a good thing, I say no, not necessarily. If you want your exhaust to be a bit louder, and you want to pick up a few horses, then your best bet is a dual-inlet, dual-outlet muffler from flowmaster. If you absolutely can't stand the notion of having a Flowmaster, then go with a dual inlet/dual outlet muffler from the company of your choice. The X-pipe into two single mufflers works, and it's easier for the exhaust techs to do, but I think that is better for the top end racing vehicles that are custom tuned and making 16 lbs of boost at 6500 rpm. A street/strip vehicle will lose hp and torque with this kind of set-up.

Not trying to flame- just sharing the fruits of my research.


Hope this helps,

 

so does anyone know the stock back pressure? I read that it's 2.5 pounds of back pressure at 6,000 RPM

 

can or has anyone tried ruinning just the catalytic converters without a muffler?

 

wrongday,
thanks for the explination,
a few questions
i have dual 40 series mufflers. two single in single out. is that bad? Should I convert to a dual in dual out? in your opinion, is the dual 14416 setup a good setup?

 

J15BIG-

Do you have an X-pipe or some other crossover before the mufflers? If so, then if you plan on adding pulleys and a custom tuned chip, then I wouldn't change it over. If you plan on keeping the boost levels stock and using an 'off-the-shelf' chip, then I'd convert it over to a 40 series DeltaFlow. No X-pipe, as the muffler itself is the bank-to-bank pressure equalizer. In fact, the muffler does a better job than any X-pipe can.

Qball- I don't know what the exact pressure is, because it varies so much at any given point due to heat, pulse timing, distance from the exhaust valve, etc. There really isn't a way to measure exhaust back pressure per se. One can only average using some kind of pressure transducer and real-time data logging equipment. Even then it's iffy at best. The bottom line is. . .you want that pressure. It helps cushion and equalize the two banks of cylinders in your engine. Plus it gives the computer a little more time to make accurate and timely A/F tuning adjustments. There's more to be gained by letting the computer tune properly than there is by losing the small amount of backpressure.


Hope this info helps you,

 

You sound like just the guy to talk to about this. I am just about ready to change exhaust. I will have a 4# pulley and Superchip. I was planning on 14416 Magnapacks. Really think the stocker is too quiet. So I'm just looking for better sound and don't expect any performance improvements. Are they a good choice? Got suggestions? x-pipe or no X-pipe? For sound I really don't see any point in spending 6-700 dollars. BTW, the reason I pick the Magnapacks is I heard them and like the sound. Haven't heard Flows on this truck.

 

j,
right now i have a blown engine but soon i will be running somewhere around 17-20 lbs of boost along with a dyno tuned chip. oh yeah, i dont have an x-pipe of any sort. will i be in trouble if i keep that exhaust?

 

Dr.D

I have the xpipe too. If you want a couple good video/sound clips shoot me your email.


Btw is only cost me about 275 dollars to make the catback, and that includes labor.
Andy