Problems on the dyno - can you help
Thread Starter
Teching In
Joined: Aug 2003
Posts: 11
Likes: 0
Problems on the dyno - can you help If anyone had ideas on how to fix this please just throw them out on the table here cause I'm lost
I have 8 runs that look like this one
A&A KIT - ATI P1sc - 4.10 pulley - single intercooler - 42lb injectors - racetronix fuel pump - otherwise stock 00 corvette.
using ls1edit - started from base file and never really modified anything in the trouble area.
Starting at afr of 10 or less and a few degrees of knock we were able to ~11 AFR and no knock but EVERYTIME we get to ~5300 RPMS there is a big drop off in power. EFIlive during the runs shows no knock retard, no changes in timing, everything seems to run the same through the low power area it just makes less power...
Dyno 1 (same as above)
Thanks,
Brian
Staging Lane
Joined: Feb 2002
Posts: 69
Likes: 0
From: Norfolk VA
Re: Problems on the dyno - can you help You need new valve springs, they are losing control of the valves right at that RPM range. You are reducing the spring rate by 7~8 pounds with the boost and they can't control the valve's actions.
Change out the valve springs and you won't see that ugly dip.
Change out the valve springs and you won't see that ugly dip.
Thread Starter
Teching In
Joined: Aug 2003
Posts: 11
Likes: 0
Re: Problems on the dyno - can you help Someone else mentioned that except he said if the valves springs float under boost, you wouldn't see the power come back after the drop. How can you tell?
the other theories at this time are:
bad plug wires - Dont know how to check them besides buying new ones
Belt slip - boost looks like its staying constant and an MMS bracket with a 4.1 pulley shouldn't slip
Thanks!
the other theories at this time are:
bad plug wires - Dont know how to check them besides buying new ones
Belt slip - boost looks like its staying constant and an MMS bracket with a 4.1 pulley shouldn't slip
Thanks!
Staging Lane
Joined: Feb 2002
Posts: 69
Likes: 0
From: Norfolk VA
Re: Problems on the dyno - can you help With the boost the springs are hitting a natural harmonic at that rpm/boost and that is why they come back.
If it was plug wires the would break down and not come back.
Plus I saw it on my dyno graph last year and replaced the springs and it fixed the problem. That is why I am pretty sure that is the problem. I know wires would cheaper and easier to replace.
If it was plug wires the would break down and not come back.
Plus I saw it on my dyno graph last year and replaced the springs and it fixed the problem. That is why I am pretty sure that is the problem. I know wires would cheaper and easier to replace.
Staging Lane
Joined: Feb 2002
Posts: 69
Likes: 0
From: Norfolk VA
Re: Problems on the dyno - can you help
Thanks for you help I think I'm going to try the springs
Good luck, be greatful it's a C5 not a F-body.
