LT1 performance

John Nechiporchik · 07-29-2015, 06:17 PM

Over the past month, I have been flogging my 98 Firebird LT1 since freshening the engine and installing the FAST XFI 2.0.
After several iterations to the VE table, we have a consistent A/F result with maximum correction at 3% at one point.
Overall, the performance of the car has been sub par with a best of 10.95 @121MPH in 2800'DA.
Additional info:
A/F target is set at 12.9-1.
converter flash is 5400...ATI 8"
shifting at 7000....RPM drops to 5800 on gear changes
Converter slip is 4% in high gear ( at end of run)
5.14 gear with 30x9 Hoosier bias tires (3 years old)
vehicle weight is 3240#
60' at Milan is 1.43-1.46 on Test and tune night (marginal track)
Just checked valve springs (PAC 1409X....170# on seat)
checked compression.....185PSI all holes
initial timing is set at 40degrees until coming off two step at 3300rpm....then pulling timing back to 36.

Questions:
Based on this info, thoughts on A/F ratio at 12.9???. I have been told the LT1's like to run fat....but I'd like to hear from someone who has experience ...preferably that runs a FAST system.
Next, I have rec'd mixed signals on the timing for this combo. Again, can someone with an LT1 stocker help me out here?
Lastly, I believe the converter is too tight based on my review of the racepak data. Again, would appreciate input based on the data presented.
BTW, I did replace the rear tires yesterday with Hoosier 18212 Lightweight radials (30x9) on a 10 inch rim...but no test results yet.
Any input is appreciated. Gotta wake this thing up !!
Thanks,
John

07-29-2015, 06:17 PM	#1
John Nechiporchik Member Join Date: Mar 2007 Location: Grosse Ile Mi. Posts: 316 Likes: 84 Liked 13 Times in 7 Posts	LT1 performance Over the past month, I have been flogging my 98 Firebird LT1 since freshening the engine and installing the FAST XFI 2.0. After several iterations to the VE table, we have a consistent A/F result with maximum correction at 3% at one point. Overall, the performance of the car has been sub par with a best of 10.95 @121MPH in 2800'DA. Additional info: A/F target is set at 12.9-1. converter flash is 5400...ATI 8" shifting at 7000....RPM drops to 5800 on gear changes Converter slip is 4% in high gear ( at end of run) 5.14 gear with 30x9 Hoosier bias tires (3 years old) vehicle weight is 3240# 60' at Milan is 1.43-1.46 on Test and tune night (marginal track) Just checked valve springs (PAC 1409X....170# on seat) checked compression.....185PSI all holes initial timing is set at 40degrees until coming off two step at 3300rpm....then pulling timing back to 36. Questions: Based on this info, thoughts on A/F ratio at 12.9???. I have been told the LT1's like to run fat....but I'd like to hear from someone who has experience ...preferably that runs a FAST system. Next, I have rec'd mixed signals on the timing for this combo. Again, can someone with an LT1 stocker help me out here? Lastly, I believe the converter is too tight based on my review of the racepak data. Again, would appreciate input based on the data presented. BTW, I did replace the rear tires yesterday with Hoosier 18212 Lightweight radials (30x9) on a 10 inch rim...but no test results yet. Any input is appreciated. Gotta wake this thing up !! Thanks, John