low end loss
06-18-2005, 01:17 PM
#1
Staging Lane
Thread Starter
Join Date: Dec 2004
Posts: 98
Likes: 0
Received 0 Likes
on
0 Posts
low end loss i put a 78mm fast intake and tb on my car. i lost lot of low end horsepower. i also had 1.8 rockers arms put on and headers. The car doent really take off untell 3500rpm. anyone know what i did worng or how to fix it?
1998 Trans am WS6
4A 32,000 miles
1998 Trans am WS6
4A 32,000 miles
06-18-2005, 04:05 PM
#2
TECH Resident
Join Date: Dec 2004
Location: K-W, Ontario
Posts: 845
Likes: 0
Received 0 Likes
on
0 Posts
You did nothing wrong except change the dynamics of the motor.
With a 1.8 rocker, you're changing valve timing and critical events like overlap, IVC, etc.,
which bleeds off cylinder pressure.
At lower RPM when the engine efficiency is not as good for your new parts,
the cylinders are getting less charge which equates to less power per power
stroke.
Aside from that, changing a TB at times needs tuning/calibration.
Has the motor been tuned to accept the new rocker ratio and TB ?
With a 1.8 rocker, you're changing valve timing and critical events like overlap, IVC, etc.,
which bleeds off cylinder pressure.
At lower RPM when the engine efficiency is not as good for your new parts,
the cylinders are getting less charge which equates to less power per power
stroke.
Aside from that, changing a TB at times needs tuning/calibration.
Has the motor been tuned to accept the new rocker ratio and TB ?
06-18-2005, 08:26 PM
#3
TECH Enthusiast
Join Date: Mar 2004
Location: Australia
Posts: 647
Likes: 0
Received 0 Likes
on
0 Posts
Lose the FAST manifold, keep the ported 78mm TB, rockers and headers. Get it tuned after. You will likely lose power without a tune because you have changed the volumetric efficiency and AFRs.