Flowmaster Exhaust

[rikhek]

Wanted to give an update on my exhaust "situation" with FACTUAL information.  I ran a Flowmaster Delta 50 Series single 3" in and dual 2.25" out on my 5.3L for about four months with the following results:

 

1.  Significant loss of low end power and general overall loss of performance even in timed ~1/4 mile runs.  Prior to the Flowmaster I could "spin" the rear tires by flooring the accelerator.  I really felt the loss when towing a 21' ski boat w/a tandem axle trailer.  With the Flowmaster the tires didn't even come close to breaking loose.  I ran these tests even with the stock air cleaner removed and the air box open for several "runs" for testing purposes so "opening" up the air inflow (as a K&N would provide) was not an observable factor.

 

I subsequently removed the Flowmaster and had the stock exhaust system reinstalled (yes, I had saved it).  I have been running the reinstalled stock system for the past 3 months.  Low end performance is back as the tires can be spun with ease (this observation is provided as a qualifier, I do not make it a habit of of spinning the tires).  Towing is much improved as is power throughout the powerband.

 

2.  With the flowmaster installed I LOST 2 mpg on every tank of gas.  Since reinstalling the stock system I have realized an improvement of just over 2 mpg.  I now get over 350 miles to a tank as oppossed to 280 with the Flowmaster.

 

Wanted to share this info as there is significant discussion on aftermarket exhausts, especially Flowmaster.  On my old 93 350 engine I had a similar Flowmaster system with great results, however, it proved terrible on the 5.3L.  It cost me quite a bit of money to buy/install/remove/reinstall the systems and wanted to make the information available so hopefully, someone else won't make the same mistake.  All I can imagine is that people claiming  "performance improvements" with this setup are letting the "noise" cloud their judgement.

 

Rick

[Shaners]

These newer motors require backpressure for performance (especially lowend).  I've considered the 70 series flowmaster for my truck, but I can't afford any power loss.  I tow a heavy 4-ton plus travel trailer, and I need all the power my 6.0L can make...  

[rikhek]

Boy do they need the backpressure!!!  It was an expensive mistake.  The only benefit I realized was in reinstalling the stock exhaust I had the welder raise it 3" to match the 3" body lift giving additional ground clearance and eliminate the system from "hanging down" below the body.

 

Rick

[Shotgun]

I have flow masters on my truck and haven't noticed any power loss..I noticed improved towing and milage......Gun

[rikhek]

Gun - how do you quantify "improved"?  Did you time the truck or have a qualifier, although silly, such as spinning the tires?  How about the gas mileage?  Can you quantify the before and after?

 

For what it's worth, my loss of power and gas mileage were not "noticed", but are actual numbers generated through 6,800 miles of documented usage.  I'm not looking to bad mouth Flowmaster, I'm just providing the results. I've used their products for years with good results until this specific application.

 

If what you "notice" is accurate, all I can imagine is you have Flowmaster mufflers and/or inlet/outlet piping small enough to provide the needed backpressure to make these engines perform as designed.  With the configuration I had it was loud and sounded "good" if that's what you're into, but if you're looking for performance improvements you're not going to get it going the route I went.

 

Rick

[Shotgun]

Well I didn't do a scientific study,but when I am pulling my 8,600lb travel trailer I can notice the improvement and I picked up about 1.5 to 2 mpg to boot.My pipes are 3" and they are true duals,2 mufflers and 2 pipes,front to back....Did you remove your cataltic converters?  I did not.Did you check your O2 sensor.I do not believe back pressure to be a factor on V8 engines.I may be wrong , but I just don't believe it and every mechanic I have talked to agrees.I did investigate this before chopping my factory exhaust off.The more air you suck in and exhaust you blow out = more power.Why do headers give such a good horse power and torque improvment? Simple.Less resrtiction or back pressure.You ever heard of Banks power packs? Their whole system is based on getting more air in and out of the engine and it works well too.I haven't seen many race cars running factory exhaust.It would be funny to go to A nascar race and not be able to hear the cars ...hehe.

[DeezBlueZ]

While you may have lost low end torque you probably gained high end horsepower.  I have heard that mods done to the induction side will give you more torque, while mods to the exhaust end will give you increases in higher r.p.m. horsepower.  While high r.p.m. power is not the ideal range for our trucks, the low end torque is.

 

 

P.S.  Hey shotgun, sweet ride! :thumb: May I ask what kind of grille you have??

[Shotgun]

Deez I pretty much agree with what you say except on the low end torque.I rather have my torque in the higher RPM range for towing reasons.When running down the interstate @ 70mph towing my camper I like climbing hills and bridges without having to down shift.Unlike Fords,which have the torque on the low end ,Gm has desiged their engines with this in mind.I drive an F-150 company truck and it will smoke the tires off the rim if you want to,but when on the highway going over hills and bridges at 70 - 75 mph,I have to take it outta overdrive even when the truck is basicly empty...Gun

 

 

Deez, my grille is made by carrige works and thanks for the :thumb:

[AZ-Z71]

I'll have to agree with Gun.  My boss has a 2002 Tahoe with a K&N filter and a cat back system and that thing hauls.  To see maximum benifits you really need to open the intake and the exhaust.

[rikhek]

As I previously stated, I ran my truck with the air filter completely removed and the air box open for maximum flow to see if it would help and it didn't make one ioda of a difference.  Smells like snake oil in here....

 

BTW - I have a throttle body spacer I'll sell for a reasonable price for a throttle body engine which will give you a 15 hp improvement and bolts on in 30 minutes and will throw in some ocean front property in Arizona.   :thumb:

 

Rick

[MiSdIrEcTeD_1]

The more air you suck in and exhaust you blow out = more power.Why do headers give such a good horse power and torque improvment? Simple.Less resrtiction or back pressure.

Well said... Why cant  everyone take that simple concept for granted??