Mismatching cam timing (maruha)
08-13-2021, 11:34 AM
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Location: Maranello, modena
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Mismatching cam timing (maruha)
Ok guys, we're rushing to dyno a BP 1.8 naturally aspirated here in modena and we surged against some ... mismatching with the maruha info.
So i try to recall the internet hive mind in order to solve this question asap if possible.
Try to follow me.
The engine is a 1.8 BP mazda, 1993 NA. The max lift as per manual is 111° both for IN and EXH. Maruha PM us a value of 115° max lift for a street use engine.
We installed on the adjustable sprocket and the F-cam from maruha, leaving no offset in the adjustable sprocket an installing them actually as original sprocket.
Now, timing the cams, we found 101° both for IN and EXH. We had expected the maruha cams to be "centerlined" with the original.
We had measured the maruha and stock cams, founding 5° offset centerlining between them (camshaft degrees, so they can account for this 111-101= 10° main shaft degrees offset).
The adjustable vernier pulley allow for a max 6° tuning (so 12° main shaft tuning) in one direction. In order to reach the aforementioned 115° PM from maruha we NEED to "jump a teeth" because we exceed the maximum lenght of the slot (101+12= 113, aiming to 115).
Is this even happened to anyone? Buying from the same vendor i would have expected this not to happen.
Anyway, i always can time the cams to 115° WHATEVER IT TAKES a-la Mario Draghi, jump a teeth, tune with the now sufficient slot and go.
So i try to recall the internet hive mind in order to solve this question asap if possible.
Try to follow me.
The engine is a 1.8 BP mazda, 1993 NA. The max lift as per manual is 111° both for IN and EXH. Maruha PM us a value of 115° max lift for a street use engine.
We installed on the adjustable sprocket and the F-cam from maruha, leaving no offset in the adjustable sprocket an installing them actually as original sprocket.
Now, timing the cams, we found 101° both for IN and EXH. We had expected the maruha cams to be "centerlined" with the original.
We had measured the maruha and stock cams, founding 5° offset centerlining between them (camshaft degrees, so they can account for this 111-101= 10° main shaft degrees offset).
The adjustable vernier pulley allow for a max 6° tuning (so 12° main shaft tuning) in one direction. In order to reach the aforementioned 115° PM from maruha we NEED to "jump a teeth" because we exceed the maximum lenght of the slot (101+12= 113, aiming to 115).
Is this even happened to anyone? Buying from the same vendor i would have expected this not to happen.
Anyway, i always can time the cams to 115° WHATEVER IT TAKES a-la Mario Draghi, jump a teeth, tune with the now sufficient slot and go.
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