2.7 & 3.2 cam characteristics/swap
03-20-2018, 03:55 AM
#1
Track Day
Thread Starter
Join Date: Aug 2016
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
2.7 & 3.2 cam characteristics/swap
hi guys,
has anyone used 2.7 cams in a 3.2 or v versa?
to cut a very long story short, i am in the final stages of putting together a Boxster 3.2 litre engine. the car/engine was involved in a workshop fire, sustaining damage to the plastic bits. a spare engine was sourced which suffered valve damage to one bank, though apparently not IMS related. we just wanted the plastic bits, but it became evident we could do with two cams to replace corroded originals. the engine was purchased as a 3.2 but it became evident when we removed the cams it is a 2.7.
both engines are later three chain engines.
rather than purchasing cams i would like to explore the possibility of using the 2.7 cams.
i downloaded the manual from easymanuals.co.uk which as it turns out seems to pertain to the earlier five chain engines.
nonetheless, it contained cam specs as follows (with calculated duration in brackets) -
2.7
Inlet opens 14 after TDC
Inlet closes 44 after BDC
outlet opens 141 after TDC
outlet closes 8 before TDC
(intake duration 238, ex duration 329)
3.2
Inlet opens 14 after TDC
inlet closes 60 after BDC
outlet opens 141 after TDC
outlet closes 6 before TDC
(intake duration 254, ex duration 327)
does this suggest the 2.7 might be a torquier cam down low?
the world of cams is a dark and mysterious one !
has anyone used 2.7 cams in a 3.2 or v versa?
to cut a very long story short, i am in the final stages of putting together a Boxster 3.2 litre engine. the car/engine was involved in a workshop fire, sustaining damage to the plastic bits. a spare engine was sourced which suffered valve damage to one bank, though apparently not IMS related. we just wanted the plastic bits, but it became evident we could do with two cams to replace corroded originals. the engine was purchased as a 3.2 but it became evident when we removed the cams it is a 2.7.
both engines are later three chain engines.
rather than purchasing cams i would like to explore the possibility of using the 2.7 cams.
i downloaded the manual from easymanuals.co.uk which as it turns out seems to pertain to the earlier five chain engines.
nonetheless, it contained cam specs as follows (with calculated duration in brackets) -
2.7
Inlet opens 14 after TDC
Inlet closes 44 after BDC
outlet opens 141 after TDC
outlet closes 8 before TDC
(intake duration 238, ex duration 329)
3.2
Inlet opens 14 after TDC
inlet closes 60 after BDC
outlet opens 141 after TDC
outlet closes 6 before TDC
(intake duration 254, ex duration 327)
does this suggest the 2.7 might be a torquier cam down low?
the world of cams is a dark and mysterious one !
03-21-2018, 07:00 AM
#2
Track Day
Thread Starter
Join Date: Aug 2016
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
i cant find the values for M96/23 and M96/24 but the values for M96/25 and M96/26 are as follows -
M96/25
intake open early/late 21 BTDC/19 ATDC
intake closes early/late 9 ABDC/49 ABDC
outlet opens 39 BBDC
outlet closes 8 BTDC
M96/26
26 BTDC/14 ATDC
20 ABDC/60 ABDC
39 BBDC
6 BTDC
i had been using this calculator ( https://www.rbracing-rsr.com/camshaft.html ) but hadnt noticed the issue of inlet opens ATDC rather than BTDC. how can one calculate the "late" duration?
M96/25
intake open early/late 21 BTDC/19 ATDC
intake closes early/late 9 ABDC/49 ABDC
outlet opens 39 BBDC
outlet closes 8 BTDC
M96/26
26 BTDC/14 ATDC
20 ABDC/60 ABDC
39 BBDC
6 BTDC
i had been using this calculator ( https://www.rbracing-rsr.com/camshaft.html ) but hadnt noticed the issue of inlet opens ATDC rather than BTDC. how can one calculate the "late" duration?
