While we are reviewing cams.....
Aug 18, 2015 | 12:04 PM
#31
I have a few thoughts here.
First is that this is a LOT of overlap. Likely more than you need, and you will run less boost, effectively lowering your boosted CR.
Second is that the intake close is very late. That will rev very high. It's later than I would have liked to see, but that can be changed advancing the cam.
Third is that the exhaust open is much later than I would like to see, again it can be fixed to a certain degree by advancing the cam.
This same cam on a 115+5 looks a lot more attractive to me. It brings overlap to 23* from 29, and changes the intake close to 53*, and the exhaust open to 70*. A 62* Exhaust open is later than tooley's stage 1 blower cam just to put that in prospective... way too late for the boost you're running with twin 1900's.
First is that this is a LOT of overlap. Likely more than you need, and you will run less boost, effectively lowering your boosted CR.
Second is that the intake close is very late. That will rev very high. It's later than I would have liked to see, but that can be changed advancing the cam.
Third is that the exhaust open is much later than I would like to see, again it can be fixed to a certain degree by advancing the cam.
This same cam on a 115+5 looks a lot more attractive to me. It brings overlap to 23* from 29, and changes the intake close to 53*, and the exhaust open to 70*. A 62* Exhaust open is later than tooley's stage 1 blower cam just to put that in prospective... way too late for the boost you're running with twin 1900's.
Aug 19, 2015 | 04:45 PM
#32
I have a few thoughts here.
First is that this is a LOT of overlap. Likely more than you need, and you will run less boost, effectively lowering your boosted CR.
Second is that the intake close is very late. That will rev very high. It's later than I would have liked to see, but that can be changed advancing the cam.
Third is that the exhaust open is much later than I would like to see, again it can be fixed to a certain degree by advancing the cam.
This same cam on a 115+5 looks a lot more attractive to me. It brings overlap to 23* from 29, and changes the intake close to 53*, and the exhaust open to 70*. A 62* Exhaust open is later than tooley's stage 1 blower cam just to put that in prospective... way too late for the boost you're running with twin 1900's.
First is that this is a LOT of overlap. Likely more than you need, and you will run less boost, effectively lowering your boosted CR.
Second is that the intake close is very late. That will rev very high. It's later than I would have liked to see, but that can be changed advancing the cam.
Third is that the exhaust open is much later than I would like to see, again it can be fixed to a certain degree by advancing the cam.
This same cam on a 115+5 looks a lot more attractive to me. It brings overlap to 23* from 29, and changes the intake close to 53*, and the exhaust open to 70*. A 62* Exhaust open is later than tooley's stage 1 blower cam just to put that in prospective... way too late for the boost you're running with twin 1900's.
This cam is supposed to peak at 6700 and was apparently spec'd around the flow characteristics of my ETP heads...actually they used the data for the similar MAST heads.
So on 115+4 rather than 112
Intake open 11* BTDC becomes 13
Intake close 55* ABDC becomes 53
Exhaust open 62* BBDC becomes 70
Exhaust close 18* ATDC becomes 10
DCR 7.85:1 becomes 7.96:1
Boost CR 18.53:1 becomes 18.79:1
Overlap goes from 29 to 23 as stated
Given that exhaust opening is a balance between getting the most out of the power stroke and getting the exhaust out....How do we determine the best timing for it?
Last edited by DrX; Aug 20, 2015 at 11:21 AM.
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