hp gain

[jstreet0204]

But not above what the motor is already putting out unrestricted. If you have a motor dyno'd at 400 HP with the stock set-up then move to a more free flowing exhaust then yes you would gain but not more than you already had meaning without the stock exhuast your motor would dyno at 420 unrestricted for example.

What you are missing is the differnce between gross and net horsepower. Since 1972 manufacturers started using sae net hp for the fwhp numbers. This is measured with the full exhaust. Gross hp pre 1972 measured with unrestricted exhaust. The 260 hp rating was measured with the exhaust intact, so by removing the restrictions in the exhaust you will gain hp at the fw using the SAE net hp standard. Using the gross hp standard you would not. Your engine dyno example explained a gross hp measurement.

 

[jstreet0204]

Understood...but you are only freeing up what is already there. The engine, unrestricted, lays down a certain HP. Each accessory drains that power. You find ways to drive those accessories more effieciently but not more than what the engine put out unrestricted. You will not add power, just free up what was lost.

I know what you are saying that this will still be measured at the flywheel and the gains will be there...I guess is boils down to whether the 260 rating is an unrestricted HP or if it was with accessories and exhaust. Given that then yes you would add to the totla output HP of the engine. But if that is unrestricted numbers, and that is what I based my early reply on, then you wouldn't add to that 260...just get closer to it.

I think you figured it out before I finished typing my last post...

 

[CanadaStang]

What you are missing is the differnce between gross and net horsepower. Since 1972 manufacturers started using sae net hp for the fwhp numbers. This is measured with the full exhaust. Gross hp pre 1972 measured with unrestricted exhaust. The 260 hp rating was measured with the exhaust intact, so by removing the restrictions in the exhaust you will gain hp at the fw using the SAE net hp standard. Using the gross hp standard you would not. Your engine dyno example explained a gross hp measurement.

Thanks jstreet, you just saved me a lot of typing
SAE net [260] is rated at the flywheel with all accesories and factory exhaust.

 

[mrvax]

i just ordered a bbk x o/r pipe and flowmaster am thunder cat with mil elimaters my first mod whats factory hp and how much will i gain

The off road X pipe will probably give a N/A Mustang about 12rwhp gain. The Flowmaster cat back will probably lose about 5 (chambered). I'd say a net gain of 7rwhp.

 

[COramprat]

Vax...you really think you lose 5HP compared with a stock catback?

 

[mrvax]

Vax...you really think you lose 5HP compared with a stock catback?

I'm not guessing. I'm going by several people that have posted here or on Corral. Some of them replaced the stockers and "thought" they may have lost a few ponies. Several of them dynoed and lost 5. Now, I know that dyno results vary day to day but the general consensus between about 8-10 posters was a loss of about 5 rwhp!

If you look inside a Flowmaster muffler, the exhaust really bounces around in there before making an exit. If anything, I'd want to ADD rwhp over stock. Going with anything other than straight-through mufflers may sound nice but will not get optimum performance.

 

[Dragstr05]

The only mods to my 2000 GT are a K&N drop in and a Flowmaster American Thunder cat-back. I didnt notice anything at all after the filter. I MAY have gained a little up top from the cat back because it seemed to break the tires loose a little easier, but soon as I started driving it I noticed an immediate loss in low end torque, which I dont notice now anymore since its been a couple weeks. If I did it all over again, I prob would have got a mid pipe and weld ins route, but oh well.

Also, be prepared to have some fun with the flowmaster catback. It sounds ok with the stock H (I deffinately want it louder though!), but I'm not happy with the fitment at all! I even got it on my old highschool alignment rack so the car was at normal ride height since it doesnt change the suspension height, and I still couldnt get the driver side tip to come out right.

 

[Scott_95GT]

10 hp

 

[twogts4us]

Understood...but you are only freeing up what is already there. The engine, unrestricted, lays down a certain HP. Each accessory drains that power. You find ways to drive those accessories more effieciently but not more than what the engine put out unrestricted. You will not add power, just free up what was lost.

I know what you are saying that this will still be measured at the flywheel and the gains will be there...I guess is boils down to whether the 260 rating is an unrestricted HP or if it was with accessories and exhaust. Given that then yes you would add to the totla output HP of the engine. But if that is unrestricted numbers, and that is what I based my early reply on, then you wouldn't add to that 260...just get closer to it.

First, sorry if you felt my tone was harsh...no harm intended.
Second, I think your angle is that power adders (that truly 'add power' above and beyond what is 'already there') and what we might call here 'power freeiers' (for lack of a better term at this moment, items that essentially free up available power based on the original configuration of the engine) do not relate at all. The fact is they do...you can GAIN power with bolt ons - not just free up what is 'already there' - I mean, you do free up power, but in doing so you are making power. The 260 HP rating is not the ceiling. Your statement leads the reader to believe he can never make more than 260 HP unless he uses a power adder and that is simply not true. Look, if you start with a stock 260 HP, put it on a dyno (motor only, with stock exhaust manifolds and whatever tubing and muffs the dyno shop has around) and find you really got 250 FWHP...put it back in the car (still stock exhaust front to back) and dyno it there...and end up with about 220 RWHP. OK? Then put full exhaust on it - long tubes, O/R mid pipe, catback and hit the dyno again - you are rewarded with around 240-245 RWHP, right? Now pull that motor and put it on a dyno (motor only again, but with the long tubes now) - don't you think you'd be above the original 250 FWHP? And if you kept adding little 'power freeiers' (plenum, TB, pullies, etc.) that you could easily pass the 260 FWHP rating?

 

[ponysarepretty]

I'm not guessing. I'm going by several people that have posted here or on Corral. Some of them replaced the stockers and "thought" they may have lost a few ponies. Several of them dynoed and lost 5. Now, I know that dyno results vary day to day but the general consensus between about 8-10 posters was a loss of about 5 rwhp!

If you look inside a Flowmaster muffler, the exhaust really bounces around in there before making an exit. If anything, I'd want to ADD rwhp over stock. Going with anything other than straight-through mufflers may sound nice but will not get optimum performance.

Whats your opinion of X pipe sans mufflers

 

[COramprat]

First, sorry if you felt my tone was harsh...no harm intended.
Second, I think your angle is that power adders (that truly 'add power' above and beyond what is 'already there') and what we might call here 'power freeiers' (for lack of a better term at this moment, items that essentially free up available power based on the original configuration of the engine) do not relate at all. The fact is they do...you can GAIN power with bolt ons - not just free up what is 'already there' - I mean, you do free up power, but in doing so you are making power. The 260 HP rating is not the ceiling. Your statement leads the reader to believe he can never make more than 260 HP unless he uses a power adder and that is simply not true. Look, if you start with a stock 260 HP, put it on a dyno (motor only, with stock exhaust manifolds and whatever tubing and muffs the dyno shop has around) and find you really got 250 FWHP...put it back in the car (still stock exhaust front to back) and dyno it there...and end up with about 220 RWHP. OK? Then put full exhaust on it - long tubes, O/R mid pipe, catback and hit the dyno again - you are rewarded with around 240-245 RWHP, right? Now pull that motor and put it on a dyno (motor only again, but with the long tubes now) - don't you think you'd be above the original 250 FWHP? And if you kept adding little 'power freeiers' (plenum, TB, pullies, etc.) that you could easily pass the 260 FWHP rating?

Gotcha...pretty much determined that the 260 rating was with all of the "restrictions" so going with less restrictive items you could see higher than 260...

I know mine is higher thatn 215 now...

 

[mrvax]

Whats your opinion of X pipe sans mufflers

I don't know about running w/o mufflers. I'd guess there would be some peak HP gain, but small. X pipes usually give more power than H pipes do.