scottfromwantirna
New Member
- Joined
- May 12, 2012
- Messages
- 7
- Reaction score
- 1
- Points
- 3
- Age
- 36
- Location
- Melbourne
- Members Ride
- VY Commodore S 3.8
Hi Gents - I'm hoping someone might be able to give me some sort of explanation on why a VY v6 might be making less power/torque after a top end rebuild and a stage 1 cam. The story goes a little something like this:
I decided that after 300,000kms the old ecotec needed some love and organised a couple of weeks off work to do a partial rebuild and install a cam. Previous modifications included 1.9:1 ratio rockers, CAI and a full exhaust system - I had a custom tune done 2 years ago by Grant at Custom Tuning Services Cheltenham (I cannot speak highly enough of Grant and would recommend him to anyone interested in a custom tune or any sort of mechanical advice/servicing/anything! He is very meticulous and offers a great service!). The car made 130kW at 5000rpm and 325nm at 3500rpm (see attached .pdf file for comparison).
The recent rebuild consisted of:
-full head reconditioning (at hoppers heads who are also amazing and I would happily return if I ever needed the service) with new valves/seats/valve guides/valve stem seals and some gear from Mace including 105lb valve springs/collets/retainers.
-Stage 1 Crow Cam for high ratio rockers CROW CAMS TO SUIT V6'S WITH HIGHER RATIO ROCKERS - Mace Engineering Group
-Crow Cam timing set (including cam gear, crank gear and single row chain)
-New roller lifters
-Cleaned everything as I went along and installed new cam angle sensor, crank angle sensor, front main seal, rear main seal, harmonic balancer, O2 sensors, TPS sensor, PCV valve, new injectors, fuel filter, fuel pressure regulator, EGR valve, knock sensors and more. Heads went on with a set of ARP studs. Obviously replaced all gaskets along the way with no shortage of RTV!
No leaks, no warning lights, no funny noises/vibrations or anything noteworthy (smoothest running engine I've ever felt, starts first go, oil pressure is good and the new cam has given it a nice bit of chop at idle).
Here's the problem. At the current stage (4 pulls on the dyno) in the tuning process, its producing 13% LESS power and torque the whole way through the rev band - at 5000rpm it breaks even with the previous tune. One disclaimer I have to make is that I did NOT degree the cam when I installed it and so I am putting faith in the cam card being accurate (I'm regretting this as it would have been a nice thing to rule out just in case it was wrong). The 210 inlet and exhaust duration with an LSA of 114degress was selected as I had bottom end torque in mind (personally I think its more practical for a daily driver).
So I guess the question is - Can anyone suggest a reason for the lower power/torque? Has anyone experienced/heard of this before? Springs too heavy maybe? Likelihood of cam being inaccurate/not degreed (I lined up the timing marks dot to dot with no advance/retarding)? I would have thought that even if the cam was too big for the application I selected or if the timing had been somewhat retarded due to me not degreeing it, that it would at least be producing some power up high?
I appreciate any comments made on this topic.
Cheers,
Scott
I decided that after 300,000kms the old ecotec needed some love and organised a couple of weeks off work to do a partial rebuild and install a cam. Previous modifications included 1.9:1 ratio rockers, CAI and a full exhaust system - I had a custom tune done 2 years ago by Grant at Custom Tuning Services Cheltenham (I cannot speak highly enough of Grant and would recommend him to anyone interested in a custom tune or any sort of mechanical advice/servicing/anything! He is very meticulous and offers a great service!). The car made 130kW at 5000rpm and 325nm at 3500rpm (see attached .pdf file for comparison).
The recent rebuild consisted of:
-full head reconditioning (at hoppers heads who are also amazing and I would happily return if I ever needed the service) with new valves/seats/valve guides/valve stem seals and some gear from Mace including 105lb valve springs/collets/retainers.
-Stage 1 Crow Cam for high ratio rockers CROW CAMS TO SUIT V6'S WITH HIGHER RATIO ROCKERS - Mace Engineering Group
-Crow Cam timing set (including cam gear, crank gear and single row chain)
-New roller lifters
-Cleaned everything as I went along and installed new cam angle sensor, crank angle sensor, front main seal, rear main seal, harmonic balancer, O2 sensors, TPS sensor, PCV valve, new injectors, fuel filter, fuel pressure regulator, EGR valve, knock sensors and more. Heads went on with a set of ARP studs. Obviously replaced all gaskets along the way with no shortage of RTV!
No leaks, no warning lights, no funny noises/vibrations or anything noteworthy (smoothest running engine I've ever felt, starts first go, oil pressure is good and the new cam has given it a nice bit of chop at idle).
Here's the problem. At the current stage (4 pulls on the dyno) in the tuning process, its producing 13% LESS power and torque the whole way through the rev band - at 5000rpm it breaks even with the previous tune. One disclaimer I have to make is that I did NOT degree the cam when I installed it and so I am putting faith in the cam card being accurate (I'm regretting this as it would have been a nice thing to rule out just in case it was wrong). The 210 inlet and exhaust duration with an LSA of 114degress was selected as I had bottom end torque in mind (personally I think its more practical for a daily driver).
So I guess the question is - Can anyone suggest a reason for the lower power/torque? Has anyone experienced/heard of this before? Springs too heavy maybe? Likelihood of cam being inaccurate/not degreed (I lined up the timing marks dot to dot with no advance/retarding)? I would have thought that even if the cam was too big for the application I selected or if the timing had been somewhat retarded due to me not degreeing it, that it would at least be producing some power up high?
I appreciate any comments made on this topic.
Cheers,
Scott
