marc_w

I would give your truck a few days to adjust the fuel trims... since you freed up the exhaust so much, I'm quite sure that they're 'off'.

I'm running 2.5" to the 2-in 2-out muffler (with mild crossover abilities), to 2.125" tailpipes. I PICKED UP lowend...

I'm up in the air about the backpressure thing. I personally don't think you can have 'too little' with proper tuning.

snoman

Todays vehicals are highly "tuned" devices from intake to tailpipe and major monkeying with the exhaust will generaly produce more loss, especailly at lower speeds, than gains overall. Older vehicals with high compression radical cams and carbs are a different matter.

rgvsierra

iTrader: (7)

have you even read any posts in the external section, do yourself a favor and do so.

snoman

I no first hand what happens and as many have found out after the fact. It is all about image and hoping to magically transform their big SUV into a higher MPG unit. If it really worked they would come tha way from the factory because Detriot is trying to sqeak out every last bit of MPG for EPA ratings. Think about that!!

rgvsierra

iTrader: (7)

you didnt answer my question, did you read any threads in the external engine section, please do so .

i monkeyed around with my exhaust, running dual 2.5 strait through mufflers, 2.5 pipes, no cats, midlenth headers and i havent lost any low end, mpg,anything.. i'm only faster and getting a tiny bit more mpg.

BigKID

iTrader: (5)

I believe the term "backpressure" is being misunderstood and/or misused. What affects the lowend torque is exhaust velocity which is directly proportional to exhaust pipe diameter. You can build an exhaust with very little to no backpressure with smaller diameter pipe that has a high velocity and make great power thruout the rpm range. A true dual 2.5" setup may be too large for a fairly stock 4.8/5.3 because there is not a high enough volume of air to promote a high velocity thru the said flowarea. On the other hand you can have an exhaust too small to flow the output air from the engine in which it 'backsup' in the pipe(s) creating backpressure. This will NOT create more power on low end, it just feels that way because you are loosing power inthe higher rpms because the exhaust cant flow that volume of air but in the lower rmps it is on the edge of its flow capibilities in turn creating a high exhaust velocity. So with this being said, if you still think 'backpressure' is the key, go put some restrictors on you tail pipes with the same diameter piping and tell me if the power output of you truck increases throughout the rpm range.

styleandspeed

For changing an exhaust that much you really do need to get a tune to make up for all of the changes. Some people think that a tune doesn't matter that much, but it does. Your truck is probably freaking out now without all that backpressure, and would be helped greatly by just getting a good tune. Try that before putting te stock setup back on.

bodyguard6799

So what you saying is that for a fairly stock 4.8/5.3 even with headers, keep the cats and merge the two 2.5in. pipes into one 3in. into one big muffler and you will get a better gain and save money on the exhaust setup??????

Silver2004

I'm going to agree with BigKID, I think it's got more to do with exhaust velocity than least amount of backpressure. The stock y-pipe looks to be fairly well designed. If going to true duals offered such an advantage on stock and mildly moded trucks, then the aftermarket would be flooded with companies selling them. The only aftermarket y-pipe replacements that I've seen are the Dynatech headers w/ y-pipe and high flow cats, and magnaflow y-pipe with high flow cats(I've only seen this one on a thread, never advertised)

bodyguard6799

But when you switch to mid or long tube headers dont you have to junk the stock y-pipe???