Elijah Moore

On my 92 SR5 ext cab turck i cant figure out if it is a limited slip/posi or if it just has the intependent. i was going to take it apart but thought i might ask first. and it has a wire comming out of the top of the rearend, not sure what it might be, maby a sencor wire or somthing else.... then i was just wondering what might happen to the V6 3.0L motor if i leave it straight piped. i had to gut the cadilitic converter and there was no muffler on it when i boutgh it, it just had duals on it after the cad.. i got a thrush muffler 40 serios. but i dont know if that will do anything for back pressure.....

Jay351

Chances are its an open diff. To check simply jack up the rear end and spin one of the rear tires. If the opposing rear tire spins the same way, you have a limted slip/locker, then you can go from there. If it spins the opposite way, you have the stock open rear end.

The "wire" comming out is the rear ABS speed sensor. If removed it will throw a ABS light... untill you remove the bulb

The exhaust is not right. Throw a high-flow cat on there and a single muffler. Run a single 2.25" pipe. Anything bigger is going to hurt your motor. You need to keep the exhaust hot.

Elijah Moore

Thnak you for the help. i do belive that both tires spin but i dont remember, i do know that if i hold one tire and spin the drive shaft the other tire spins and the tire i am holding tuggs a lil on my hand in the same derection as the other wheel. i will check to see if the one wheel spin will spin the other in the same direction.. with the high flow cat will it give me back presure and decreas my deseables or stay the same.. right now my exuaste sounds excelent, i am running stock pipe i think 2 in.

gamerndm

You don't need any backpressure at all. On a 2-stroke engine, yes, you do need some, but on a 4-stroke its a no-no. You want the highest exhaust velocith you can find with optimum flow, basically, getting the most gas out the fastest.

NicCantDecide

Exactly, all that crap about needing some back pressure is just a myth (at least with 4 strokes, dunno about 2 strokes). The more gas that can escape, the more pure the new combustion mixture is.

Jay351

Which is why you need the right size exhaust pipe to keep the exhaust gases hot enough for optimum flow.

Stock pipe size is 2 1/8. Bump it to 2.25" and you're good.

dirtoyboy

Really? Do you say this from personal experience? have you ever tried to run a toy with no exhaust? It runs and sounds like absolute poop

georgiayota

when i took my ford in to get duals i wanted him to cut the cats off and he told me that he didn't want to because when people do that the truck could shut off at idle

norcalsvx

w/out any backpressure you are going to have all your power in the upper rpm's not down low where you need it

UKMyers

Hmmm where to start on this one...

First off running without a cat is ILLEGAL!

Second it makes your rig stink, not run properly, and it's not helping out the environment any.

Third you guys have no clue what your talking about when your saying that a small displacement 4 banger or V-6 needs no back pressure.

Elijah Moore

maby down in the states it is illegal to run with out a cat but up in alaska there is no such law, look it up.. i know when you do stragit pipe a toy it dose sound like crap and stink but you know what they way mine is stright piped it sound excelent. the cat is on my truck but it is gutted right now. the material in the cat got broken up and i could hear it ratteling around so i emptyed it. my truck dose not shut down at idel... i would be willing to bet that my truck is running cleaner than most of the older vehicals out there that all have the required emesstions specs.. only becuase i have rebuilt my motor compleatly. if it is a myth that you need backpressre (on 4 stroke) or not i have no clue. but i do know that if you dont have bake presure on a 2 stroke it will cause the motor to sease up, or burn up.. i didnt think it would be this big of a conversation?!!! lol

gamerndm

The reason that 2 stroke engine need backpressure is because they use reed valves.. thats basically it.

In certain situations backpressure can inprove the preformance of a 4 stroke engine, yes. If the engine has a unusually long valve overlap, then a small amount of pressure will help to contain the charge in the cylinder before the exhaust valve closes. However, with proper tuning, injector timing, cam timing, and valve overlap (which is required, but not in excess), this is not a issue, regardless of engine size. The more pressure there is in your exhaust manifold, the more work the engine has to do to expel the next exhaust charge at the end of the combustion cycle, therefore decreasing total outout power. a negative pressure in your manifold will pull the exhaust gasses out most effectivley, but will create a sharp drop in compression in the cylinder with any amount of valve overlap. The end goal is for the engine to do the least amount of work expelling the spent gasses, while limiting the fresh charge from being sucked out the exhaust valve. An optimum flow scenario will have positve pressure in the exhaust manifold ("backpressure"), but in minimal amounts required for the application.

Basically, you can tune any engine to run with no cat or muffler on the exhaust plumbing, but it will take just that, TUNING. I agree that no engine that is tuned for stock setup will most likely see a drop in numbers going to a pipe in a larger diameter with no cat or muffler.