Dynoed my truck after installing my gibson swept side cat back,how about it lost 12 HP----yeah thats right 12 HP...and 8 ftlb of torque. The system looks and fits great, but holy crap WHERES THE POWER!!!!! Most of the power I picked up with the chip the exhaust took back. I even pulled the chip and made another pull,thinking maybe the chip and exhaust didnt like each other, but it still killed it. Oh well, looks like I'll be buying a supercharger sooner than I thought! GIBSON

 

Must have the wrong system lol, I got the Gibby Super Truck and picked up 12 HP, no chip.

 

I actually called Gibson this morning and talked to a tech. He told me I needed to put 1000 miles on the truck and re dyno it. Well since I had put about 300 miles on it so far,I redynoed it...same thing 214rwhp,put fact. exhaust back on- 228rwhp...put Gibson kit back on-212rwhp . I dont know, I guess I'll just leave it on ,it does sound and look good. Whats up with putting 1000 miles on it before dynoing? We dyno about 20 cars a week and I've never heard of that on exhaust systems. The only real difference I could see was the straight through design of the muffler,the pipe size was all the same.Oh well, Whipplecharger will be here in about four weeks, maybe it'll work better with some boost!! Anyway, I still love my truck!

 

Single exhaust right? Thats your reason, as well as the quiet/little more restrictive muffler than a loud one.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster American Thunder Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds .

That's it for mods now, saving for a Stang. Check out my Gallery for a look-see.

 

There's definitely a 'break in' period for most turbo-style mufflers in as far as their sound. I don't know why, but I've experienced it, and so have many others. Apparently some of them have a 'packing' that must break-in. But there are designs without packing - I don't think Flowmasters have any type of packing, just different chambers.

I'd leave the system on for 500 miles, or even the 1000 the guy said (though that does seem like a bit much), and dyno it again. Listen closely to the sound and see if you perceive a change over time, too.

But you're right - a see-through design seems like it ought to be better from the get-go.

Best,

 

>Single exhaust right? Thats your reason, as well as the
>quiet/little more restrictive muffler than a loud one. The reason I went with the single was to keep low and midrange power,we tow alot with the truck. opening up the exhaust more would decrease torque. Every exhaust kit we've done a before and after dyno on (with a mostly stock application) the large single kits make more power across the whole RPM range ,where as the dual kits generally dont increase until the upper portion of the RPM range. That said the Gibson muffler is a Straight through/baffled muffler, the stock muffler was a more restrictive offset baffled muffler. So freeing up the backpressure( at least in my case)actually hurt my power. It really isnt enough to even tell, if I hadnt dynoed it I would have sworn that it felt better!( it will actually leave four 20ft black marks from a dead idle now!)Im about over being upset about it , time to move foward with the 'charger. I was hoping to get it on before we pulled the car to the NMRA finals in Bowling Green, but dont think thats gonna happen.:-X23 .Gotta go work on the race car ,Later! --Philip,ATS Performance

 

The thing is, with the Gibson single, its a 2.5" pipe, at least it was last time i checked. For that big v10, you really do need a dual exhaust, or a 3" pipe.

 

>The thing is, with the Gibson single, its a 2.5" pipe, at
>least it was last time i checked. For that big v10, you
>really do need a dual exhaust, or a 3" pipe.
The Gibson kit for the V10,pt.no 619652, is a 3" kit with a 3.5" tip. The factory was 3" also. The single kits for the 4.6 and 5.4 are 2.5". Personally I would never run a single smaller than 3" on anything(v8-v10).

 

Yeah, It's a 3" pipe, which on a V-10 might be alittle small but hey i'm not an exhaust expert. I had a Gibson dual sport, I didnt notice a change in exhaust note over this "break in" period, but it's possible that it was a slow enough change that I didnt notice it. It takes me a few months to drive 500-1000 miles because I don't drive much. The stocker was a 3" pipe, and we all know how restrictive stock systems are. From the pipes it mostly from the bends though, not the size. I can't help much more, I think that there's so much restriction in a factory exhaust that the little gibson kit aint gonna help much, thats phase 1 of 3 phases (cats and headers). Try an MSD ignition too, get one with the supercharger that has boost control. I wish i could dyno my truck hehe. I don't see a reaso for it to reduce power though. What did the dyno look like, did it increase low end and take away from high end where your HP peak is more to the high end? That would seem right, but not if you lost 12hp in many places on the curve.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster American Thunder Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds .

That's it for mods now, saving for a Stang. Check out my Gallery for a look-see.

 

Why would you replace the factory exhaust with the same size? It doesn't make sense. That's the main reason you aren't seeing an increase in performance, you basically swapped systems.

 

>Why would you replace the factory exhaust with the same
>size? It doesn't make sense. That's the main reason you
>aren't seeing an increase in performance, you basically
>swapped systems.
The reason the single kits retain the same pipe diameter is to not lose bottom end torque. The muffler design is totally different,the Gibson muffler is a straight through muffler. Every single kit we've dynoed (Flowmaster, magnaflow, even Gibson) has picked up between 5 to 18 hp , none that we've dynoed have ever lost power - and all of those kits retain factory pipe diameter, just a different muffler style. Actually a customer came in with a Gibson single kit, we dynoed the truck before he had duals with 40 series flowmasters installed and the truck lost 3 HP. So bigger isnt always better when it comes to exhaust,thats why they offer several different kits (for pulling, top end power, etc.). Either way the truck should noy have lost power.

 

Bigger isn't always better, but same size almost always equals the same performance. I personally would have at least gone with a 3.5" system.

 

>Bigger isn't always better, but same size almost always
>equals the same performance. I personally would have at
>least gone with a 3.5" system.
If they made a 3.5" kit I probably would have went with it just to have it. The difference with the aftermarket single cat back kits is the style of muffler,flowmaster has a chambered design, Gibson and Magnaflow have a straight through design. with a factory muffler, the exhaust runs through a series of baffles before leaving the muffler, thats where the restriction comes from. So the power gain, or in my case power loss, comes from the less restrictive muffler not pipe diameter. If you look at the Gibson or Magnaflow exhaust kits , the highest power level kits are single catbacks with factory size piping.As a general rule ,large dual exhaust kits only help high RPM performance,at the expense of low RPM torque. The looks and sound of of the kit are enough to offset the power loss, for me anyway. Like I said earlier hopefully the 'charger will benefit from the exhaust. Guess I'll find out soon enough.

 

Hey!!!! Give me a hint what exhaust produced
18 HP. I have a 87 351-4V that I'm getting
ready to put headers and exhaust on. Thanks
in advance for your dyno experiances. Dan

 

>Hey!!!! Give me a hint what exhaust produced
>18 HP. I have a 87 351-4V that I'm getting
>ready to put headers and exhaust on. Thanks
>in advance for your dyno experiances. Dan
Actually it was 19HP,202rwhp to 221rwhp,--Magnaflow pt. no. 15900-- on a '01 PSD with a superchip. Cant help you with that 87 4 valver though Anyway your welcome!