4.7 L jet USA dyno runs.....exhaust comparo.. +28whp
09-23-2011, 02:26 PM
#16
Drifting
09-23-2011, 02:50 PM
#17
Supercharged
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Remember, Hacker's pushing 18psi of boost.
When i did my exhaust sizing calculations, I recall the general rule of thumb is dual 2.5" for up to 500HP, and 3" takes you up to about 725. That means a single 3" it good for about 360HP.
IIRC Hacker should be able to squeeze 500 out of that motor. And when it blows up (it will eventually), I think he's going to do something a bit more radical.
When i did my exhaust sizing calculations, I recall the general rule of thumb is dual 2.5" for up to 500HP, and 3" takes you up to about 725. That means a single 3" it good for about 360HP.
IIRC Hacker should be able to squeeze 500 out of that motor. And when it blows up (it will eventually), I think he's going to do something a bit more radical.
09-23-2011, 05:14 PM
#18
Rennlist Member
221 is very good. headers and 3.5" was good for . i had a very weak 84 that got to 200 with those mods, but it was only 175rwhp to start. i think your increases to 221 were gained over a restrictive set up or other issues with the AFM , dont know for sure, but reast easy that a lot of 84s have got 220rwhp with a set of headers and varied exhaust systems. I have the dyno runs from devek and others that show this. mine being so weak , was interesting to see it at least get near the 'strong' 84s that ive seen. yours is definitely strong, at 221 and being an automatic! good for you! heck, you might even gt up to 250hp vs my old 84 part euro 240hp with the euro intake and cams. 
09-24-2011, 02:59 AM
#20
Race Director
Thread Starter
UPDATE
It turns out there was NO timing adjustment...only fuel + exhaust.....here is the BEST dyno run of the same engine shortly after we 1st installed it compared with the new setup...the pic also shows the AFR near the bottom.... results are my old average HP from 3000-5500rpm was 178whp...it NOW is 197whp....it gained EVERYWHERE....
The fuel changes where made by "modifying" the AFM....the race shop I use is very skilled in Spec Miata which also uses a similar style AFM....so they were able to add fuel by adjusting only the AFM...
I also enclosed pics of the exhaust...the pic of the dual 2" OD pipes coming off the headers is slightly blocked by the trailer (large cross member in pic)....
It turns out there was NO timing adjustment...only fuel + exhaust.....here is the BEST dyno run of the same engine shortly after we 1st installed it compared with the new setup...the pic also shows the AFR near the bottom.... results are my old average HP from 3000-5500rpm was 178whp...it NOW is 197whp....it gained EVERYWHERE....
The fuel changes where made by "modifying" the AFM....the race shop I use is very skilled in Spec Miata which also uses a similar style AFM....so they were able to add fuel by adjusting only the AFM...
I also enclosed pics of the exhaust...the pic of the dual 2" OD pipes coming off the headers is slightly blocked by the trailer (large cross member in pic)....
09-30-2011, 02:34 PM
#22
Race Director
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09-30-2011, 02:59 PM
#23
Inventor
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Putting a balance pipe in (as close to the bell housing as possible) might make more power. It will at least make it a little quieter.
32V down pipes (55mm OD) into 2.25" would definately make more HP. (Grind header outlet to 32V gasket size.)
32V down pipes (55mm OD) into 2.25" would definately make more HP. (Grind header outlet to 32V gasket size.)
09-30-2011, 03:07 PM
#24
Race Director
Thread Starter
Putting a balance pipe in (as close to the bell housing as possible) might make more power. It will at least make it a little quieter.
32V down pipes (55mm OD) into 2.25" would definately make more HP. (Grind header outlet to 32V gasket size.)
32V down pipes (55mm OD) into 2.25" would definately make more HP. (Grind header outlet to 32V gasket size.)
09-30-2011, 03:47 PM
#25
Race Director
Thread Starter
Here is the baseline run with the new exhaust and the comparison with increasing fuel......take a look at the bottom line, which is the AFR comparison....it was far too lean before...increasing fuel just shot the HP & Torque up!!!!!
