ok, in dec. i dynoed my car right after the longtube and ory install. car made 275rwhp. started having spark issues and changed plugs/wires/opti. sent for a tuned pcm, got it in and dynoed again. after all the new stuff and tuned pcm, it only made 271rwhp. im wondering if i should get a new tune, or try dynoin the tuned pcm and the stock one back to back on the same day? the first time i dynoed the 275, it was 45-50 degrees with little to no humidity, and the day with the tuned pcm was about 5 degrees out. the A/F looked good. i was also considering buying lt1edit and dyno tune the car. i just want to make sure im getting the most out of my bolt ons before i start adding more performance parts.

 

Have you taken your car to a track and run it? A quartermile et and trap speed are a much better indication of how your car is running than dyno numbers.

Also, not all dynos read the same. Do you know anybody with similar mods as you that has dynoed at the same place? What did they put down?

 

havnt been to the track, its over 2 hours away. no one i know has dynoed a car at the first shop that i got those numbers from, but im thinking about goin to a shop were someone else i know dynoed their bolt on Z to see if the numbers are close.

 

Dynos vary from day to day and from dyno to dyno.

 

i get this, im just wondering why my numbers went down after i installed the tuned pcm

 

well i have almost the same setup as you steve97. i ran into the same problem a month ago. i had dynoed my car when i installed Pacesetter LT's and ORY(november), through an OEM LS1 muffler. i was happy with 279hp/289tq without the cutout open, but A/F was at 13.5 so there was some improvement to be had. last month i went back with true duals/xpipe/bullets and a chip and only got 251/hp/261tq(w/out chip) then 261hp/281tq(chip). i was pretty pissed off but i still run times in sig. even the guy that owns the shop told me that his 8 sec. mustang was off from the #'s he put down in november. dont worry though just get some track times and put this to rest .

 

275 RWHP seems kind of low...

Most guys with those mods are making 285-295.

 

did you dyno with those heavy a$$ ZO6 wheels, because i did that in december to try out the cutout i had on the ORY and i only did 267hp/28xtq. i know that having larger/heavier wheels creates more rolling resistance, which can affect #'s as well. case and point, i ran a best of 13.9@99 w/a 2.2 60ft on 17"/18" ZO6 wheels, and then slapped on the stockers/et streets and skinnies and ran times in sig. but really though just get some sticky tires and go to the track, take a friend cuz driving 2 hrs gets lonely. i drive for about an hour to and from the track and i get bored soemtimes.

 

haha, I drive 2 1/2 hours to my gf's every weekend, I've grown used to it

 

i did dyno with the zo6 rims on, how ever they were on both times, before and after.the cars gonna sit for a while, i need to buy 2 o2 extendeds and a new o2's(or corvette o2's), and some other bolt ons, hook up my guages that have been sitting hear for ever. and hope i can get the car all squared away by mid may.