Need some opinions on my Moddified exhaust..

[RubySlow]

Ok as many may know I have dual 40 series 2 chamber flows 2.25 inlet, 2.50 outlet, Secondary cats removed, hpipe/ crossover tube installed...




here is the video

http://www.youtube.com/watch?v=2SyjEkVFLbM

Ok well Since Ive been running this setup My gas mileage has dropped, Iam assuming it has to do with the backpressure or lack there of...



So My Question is, would it help to install some secondary mufflers to apply some backpressure which the computer will like, or should I install some secondary mufflers and remover the primary cats and have a custom chip made....?

Oh I have these mufflers laying around and thinking about having them installed..

here some specs... T304 Full Stainless Steel Inside and Out . Most Other Ebayer Mufflers are Stainless steel on the Outside meaning that they eventually will rust from the inside out .
Fully removable Silencer
Straight Cut Tip
Lifetime Warranty for as long as you Own your Vehicle
Straight Thru Design for Better Flow
Measurements :

Lenght Of Muffler : 20" Inches (From Inlet Tip to Exhaust Tip)

Muffler Inlet : 2-1/2" Inches

Exhaust Tip Diameter Size : 4" Inches

Exhaust Tip Lenght from Canister : 4" Inches

Muffler Canister Diameter : 5-1/2" Inches

Muffler Canister Lenght : 14" Inches

 

[hunterdan]

I doubt your drop in mileage has anything to do with a lack of backpressure. The 2 flowmasters and retaining the primary cats would retain backpressure. I would look elsewhere before blaming your exhaust system. Could it be that you are in the the throttle now more than you used to be? Have you tried disconnecting the battery for a few hours to reset the computer? When was your last tuneup performed?

Dan

 

[Turdle]

Your gas mileage went down, because youre foot goes down more now!
What kind of intake are you using?


No, do not remove the primary cats!

I would try for a rear exit though--those fumes cause drain bamage

 

[snocross1985]

I think adding some tailpipes would help out. Please don't put those ricer mufflers on there.

 

[Turdle]

Umm,
Can you get your driveshaft out?

 

[toypaseo]

Oh I have these mufflers laying around and thinking about having them installed..

I have seen trucks with those, and 100% of them sounded like crap. Looked very out of place on them.

Look elsewhere

 

[Afboy143]

please, no ricer mufflers. Your gas prolly went down due to loving the sound of the exhaust so your foot is into the pedal. You're running the V8 motor so backpressure isnt that much of a prob as it is for us V6's. Backpressure kills mostly low end torque, not so much gas milege. Age can also kill too...maybe do a basic tune up? Get injectors cleaned professionaly (not put a bottle in the gas tank, actually getting them cleaned), new air filter, fuel filter, check tire pressure, synthetic oils, can of RESTORE in oil, ect.

 

[Xan]

i don't how many times i've said it but having your exhaust cut off like that under your truck will heat your gas which will make you lose power and milage that and that one muffler is kinda over close to the gas tank so that probaily doesn't help either.
i'm not to sure if you lost all that much back pressure considering you got 2 mufflers and a cross over.
I will say i know you just lowered it too did you get a alignment after you did that? that will affect it too.

if you think you'd like the sound of those mufflers put them both out the back of your truck. if you'd like the look thats up to you i'm not gonna dog on you for them. i got some big tips that a muscle car guy called them ricer tips (they were called truck/suv tips only used them cause i had one) but then i've had like 3 girls say it makes my truck look sexy and 10 guys say it looks mean as hell

 

[Afboy143]

i don't how many times i've said it but having your exhaust cut off like that under your truck will heat your gas which will make you lose power and milage that and that one muffler is kinda over close to the gas tank so that probaily doesn't help either.

Please explain

 

[Xan]

Please explain

An intercooler cools the air going into the engine, some racers put ice inside their coolers to make a cooler denser air/fuel charge. air and fuel burn better at cooler temperature because its more dense. when something is heating up your gas such as your exhaust (i bet your floor even gets warm around where they are) then you will have a less dense charge making it less efficient to burn.


if you don't beleave this go out and run down a strip when its 105 degrees out then go down and run down the strip when its about 65-70 degrees out and see which one is faster

 

[Afboy143]

I just dont see how exhaust dumping under a truck will effect performance. Sound? yes. Fumes in truck? yes. Performance? ehhh

 

[Xan]

I just dont see how exhaust dumping under a truck will effect performance. Sound? yes. Fumes in truck? yes. Performance? ehhh

if you think so ecspecialy with the muffler close like that set up

ask an exhaust guy...

 

[sid23man]

I think adding some tailpipes would help out. Please don't put those ricer mufflers on there.

2x's

 

[Afboy143]

if you think so ecspecialy with the muffler close like that set up

ask an exhaust guy...

I did last night as I was at a friends shop who specilized in mustags. He said he has never heard such a thing. Most big trucks, like cargo trucks and such, has the exhaust dumped right under the truck after the cab.

Outside air temp has nothing to do with a muffler dumped under your truck. Your intake is totally different than your exhaust. A cold air charge is more dense, hense a stronger spark and more power. If Im reading right, your saying if I dump the muffler under my truck, the exhaust fumes will surround my gas tank and heat the gas up correct? If so, does hot gas not burn as well? I dont think the temp of the gas matters as much as the air temp. Have you actually seen where the gas tank is compared to where the mufflers dump? Do you think the muffler exhaust fumes are really going to heat up the gas that much? It just doesnt click. Maybe if you're in stand still traffic forever it would, but if your constantly moving, the airflow under the truck would vent out the exhaust fumes. Ive heard of turbos in underhood setups burning stuff up because everything is so close and in an confined space. Muffler dumping a truck tho? Its so wide open and spread apart, I doubt anything happens.

 

[hunterdan]

I did last night as I was at a friends shop who specilized in mustags. He said he has never heard such a thing. Most big trucks, like cargo trucks and such, has the exhaust dumped right under the truck after the cab.

Outside air temp has nothing to do with a muffler dumped under your truck. Your intake is totally different than your exhaust. A cold air charge is more dense, hense a stronger spark and more power. If Im reading right, your saying if I dump the muffler under my truck, the exhaust fumes will surround my gas tank and heat the gas up correct? If so, does hot gas not burn as well? I dont think the temp of the gas matters as much as the air temp. Have you actually seen where the gas tank is compared to where the mufflers dump? Do you think the muffler exhaust fumes are really going to heat up the gas that much? It just doesnt click. Maybe if you're in stand still traffic forever it would, but if your constantly moving, the airflow under the truck would vent out the exhaust fumes. Ive heard of turbos in underhood setups burning stuff up because everything is so close and in an confined space. Muffler dumping a truck tho? Its so wide open and spread apart, I doubt anything happens.

I have to agree with this statement. Cooler gas does help produce power, but not enough that we will ever notice. Plus as you move airflow under the vehicle, even though it may not be front to back will provide enough ventilation so as not to heat anything up too badly. The only thing that may get hotter because of it would be the rear diff.

Dan

 

[trucku]

I think the only thing you have to worry about with very excessive heat (more than ambient can ever be) against and affecting a gas tank, is how much pressure the tank builds up, because of more fuel vaporizing. And that should not be an issue with pressure relief. I don't think though you would build vapor in your fuel lines. I think gas boils at over 400F

Just make he can make a heat shield and call it a day.

 

[Xan]

I think the only thing you have to worry about with very excessive heat (more than ambient can ever be) against and affecting a gas tank, is how much pressure the tank builds up, because of more fuel vaporizing. And that should not be an issue with pressure relief. I don't think though you would build vapor in your fuel lines. I think gas boils at over 400F

Just make he can make a heat shield and call it a day.

What a heat shield But look at the above statements it wouldn't do anything why would you wanna do that?
Obviously any kind of heat shield on a muffler or cat wouldn't do anything because theres no way the heat could effect any kind of preformance and theres no way a muffler or a cat holds heat or radiates heat and no way that the wind going under a car doesn't cool everything because air cooling gets all the heat out of everything cause the bottom of a vechile is flat and and no way heat could stay under there in a heat pocket or something crazy like that

 

[trucku]

What a heat shield But look at the above statements it wouldn't do anything why would you wanna do that?
Obviously any kind of heat shield on a muffler or cat wouldn't do anything because theres no way the heat could effect any kind of preformance and theres no way a muffler or a cat holds heat or radiates heat and no way that the wind going under a car doesn't cool everything because air cooling gets all the heat out of everything cause the bottom of a vechile is flat and and no way heat could stay under there in a heat pocket or something crazy like that

what exactly are you disagreeing with or responding to in my post?

They don't radiate heat?????

You need to review your statements.

I also never said anything about performance.
I also didn't say he had excessive heat issue. I was stating what to worry about excessive heat.
I think the setup is fine.

and theres no way a muffler or a cat holds heat or radiates heat and no way that the wind going under a car doesn't cool everything because air cooling gets all the heat out of everything cause the bottom of a vechile is flat and and no way heat could stay under there in a heat pocket or something crazy like that

:bdrunk:

 

[rocket 5979]

What a heat shield But look at the above statements it wouldn't do anything why would you wanna do that?
Obviously any kind of heat shield on a muffler or cat wouldn't do anything because theres no way the heat could effect any kind of preformance and theres no way a muffler or a cat holds heat or radiates heat and no way that the wind going under a car doesn't cool everything because air cooling gets all the heat out of everything cause the bottom of a vechile is flat and and no way heat could stay under there in a heat pocket or something crazy like that

You are talking about two different things. Heated fuel and heated intake aircharges are two different things. Actually I would surmise that warmer fuel (not hot) fuel would be better than colder fuel due to its ability to atomize better into the air stream because of its evaporation point. Colder intake aircharges are always better due to more molecules of air being packed into a given volume, which will see higher cylinder pressures due to stronger combustion. That of course will lead to more power because of what I mentioned above and also being able to run more spark timing before detonation occurs. This is also the reason why people always make more power on a cold night than a hot one. Barometric pressure is higher at colder temperatures due to the molecules falling and pressing towards earth. This cause essentially earths normal sea level atmospheric pressure of 14.7 psi to go up (or down if low BP) which shoves more air into the cylinders.

The only feasible reason how I could see a vehicle make less power and less mileage with hotter fuel is if the fuel expanded so much so as to cause higher gas tank pressures and slightly overpressurize the fuel lines which would make your fuel system act bigger than it is. That could cause a rich condition to occur which would hurt mileage and also hurt power. However I really don't think the normal Joe Schmo should worry much about it.

With as much air that is moving underneath a vehicle at any given cruising speed I do not foresee the exhaust system in question affecting fuel temp in the tank by anything more than ZERO unless it is pointed directly at the tank. Now at a standstill while heat soaks into the bottom nooks and crannies of the truck it may be a different story but once the vehicle takes off and the heatsoak under the car "sluffs" off then temps will lower to close to ambient.

Overall I think you guys are nuking it in here. The most likely reason why that guy is getting worse mileage is because he is getting on the loud pedal a little more to hear the exhaust. Even the occasional romp on the gas pedal will kill gas mileage.

 

[trucku]

I agree...good sound usually equals heavier pedal for more good sound.