Stock Exhaust vs Stage 1 Exhaust, Dyno Tested Results!

[vwdmc16]

This is a test I have wanted to do from many years and I finally had the time to do after purchasing a lightly used Houston Stage 1 stainless system from fellow member Fox2506 in NC, a few months back. I hope it is educational or atleast entertaining.

The premise of this experiment was to confirm or deny the power levels that could be unlocked from our PRVs with a full exhaust system upgrade, over the years Ive hear many claims about just how much the factory exhaust restricts our engine, claims from 10 to 35hp. To test this I needed one key piece of specialized equipment, a Chassis Dynometer. This plan: dyno my healthy engine on the dyno with three pulls to get an average, remove the factory exhaust and dyno again after the new exhaust is installed. The Dyno im using is a Dynocom 5000 2wd Eddy current style machine. Its very simular in design to Mustang brand dynos which are considered the standard in power measurement int he racing/tuning industry, Speaking of which I have had this very car dynoed on a Mustang 2WD machine and got just slightly lower numbers than this Dynocom {10hp and tq less on the mustang}. The important information we are looking for is the before and after difference in output which is what I got.


The car:

Vin 1768
stock K-jet
Stock internals with 70k+ miles
stock air box and filter, cold air intake tube
MSD blaster2 coil and coil resistor deleted (this mod created a 12hp gain alone on the mustang dyno years ago)
fully stock exhaust
extra 2 degrees in ignition timing
CO adjustment optimized for 12.8:1 AFR




Dyno Time:









I used the optical RPM pick up that shoots a light at the crank pulley that has a small reflective sticker on it, the sensor detects the reflection and counts it at one rotation. I ran the car up to 5500rpm as there is no more power past 5200 anyway. Result was an average of 115hp and 141 tq. This is constant with the numbers I got off this machine early last year and again a bit higher than the Mustangs results {105hp/130tq}







The New Parts:

<10k mile used all stainless system, I cleaned it up with a media blaster and inspected the cats and muffler for wear, all look to be in great condition.






Out With The Old







Tools:






Another picture of my newly finished Bilsten HD project that I made another thread about








after bit of cleaning, still pretty filthy







Weight Difference
Another answer I couldnt find was how much lighter is the new system, So here is a ll the old stuff that isnt being reused:






55lbs!!





All the new stuff




48lbs! a savings of 7lbs, Not much...

[vwdmc16]

After cleaing and new gaskets it was time to install, My studs were only a few years of and still very clean, came out easily. The driver side was easy but the right side was a pain even on a lift. With the limited room I had to remove all but two of the manifold studs to get the clearance to get the manifold on the head, also you see the starter/ alternator wires need to be re routed around the front side.





Clearance to my tow hooks ( not stock btw) were a bit close but not enough to hit





passenger side is even closer to the frame






After the headers it was quite easy, easier than installing the stock muffer.






Back To The Dyno







Another 4 runs were made with an average of 133hp and 149tq, keeping in mind that a the this dyno measures about 8.5% higher than a Mustang brand we really get a more realistic power of {121.6 hp and 136 tq}

so an increase from 115 to 133hp (18hp) or on a Mustang {105 to 121hp} (16hp)

and an increase of 141 to 149tq (8ftlbs) or on a Mustang {130 to 136tq} (6 lbs)



Conclusion:

This exhaust system does increase power and torque but not nearly the gains that were rumored when measured on this dyno or approximated on another. Full disclosure that there are many variables at play and everyone's results will differ I tried to keep testing conditions as close as possible by measuring before an after all in one day but relative temp barrametric pressure and humidity did change a few degrees as my dyno is not indoors, so take these results as you will, it wasnt the most scientific test but it was something. Also the AFR was slightly leaner than the 12.8 I got during the baseline tests so there could be a bit of power left on the table there. All in all I believe it is a worth while upgrade as the sound is so much better and to me the car's engine note just feels liberated, that makes it a much more enjoyable drive.

Thanks for reading.

[jawn101]

Awesome tests and very interesting results. I can personally attest to the fact that the car feels faster than before (though 1768 has never been a slouch.) More importantly, though, was the responsiveness, feel and sound. Clint's car sounds like they all should have. Great upgrade! Now just to see how the smog goes next year

[Jedidentist]

Very nice test and write up. Thanks for sharing!

[DavidProehl]

Great post! The car sounded unbelievable on Saturday. When you and Jon went for a drive the rest of us were just looking at eachother with our jaws on the floor listening to it. That is how the car should sound!

[Dangermouse]

Very interesting, thanks.

I assume that yours is a Manual?

[Trstno1]

Your system looks great!

Question: What did you use to properly clean the exhaust manifold mating surface on the engine block? Also, did you use any RTV sealant in addition to the gaskets in order to create a better seal? I'm guessing not, but thought I might ask. I am about ready to install the same system as yours and just want to get all my ducks in a row prior to starting.

Thanks for the info in adavance!

[jamesrguk]

"...so an increase from 115 to 133hp (18hp) or on a Mustang {105 to 121hp} (16hp)"

It's easy to be a bit disappointed with the increase figures, but when you're starting with such low numbers it's probably best to work out the percentage increase.

115bhp to 133bhp is almost 16% increase that's a 7th more power! I'd say that's not bad just for changing an exhaust.

I'm crap at maths so feal free to ridicule as required lol


James

[vwdmc16]

Very interesting, thanks.

I assume that yours is a Manual?

Yes 5 speed

[vwdmc16]

Your system looks great!

Question: What did you use to properly clean the exhaust manifold mating surface on the engine block? Also, did you use any RTV sealant in addition to the gaskets in order to create a better seal? ...s:

I used a small 3m bristle disc on a 90' air sander to get the sealing surface clean. All gaskets dry without rtv

https://www.google.com/search?q=3m+b...56106882989591