upping the compression ratio
- dingo
- IAC Addict!
- Location: oregon - calif
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upping the compression ratio
What is the simplest way to bump up the compression ratio...using stock pistons ?
'71 Kombi, 1600 dp
';78 Tranzporter 2L
" Fill what's empty, empty what's full, and scratch where it itches."
';78 Tranzporter 2L
" Fill what's empty, empty what's full, and scratch where it itches."
- germansupplyscott
- Trusted Air-Cooled Parts Vendor
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- dingo
- IAC Addict!
- Location: oregon - calif
- Status: Offline
I already have the stock pistons....i was wondering if there was a way by shimming the jugs.....(i may be way off the track here)
Ill preface by saying that im not an expert on this subject: I believe higher compression ratio will give you more h-p or torque or both...i already mix up my own octane cocktails, so i thought i would experiemnt on the next 2L engine i put togetherThis may be a stupid question, but why would you want to do this?
'71 Kombi, 1600 dp
';78 Tranzporter 2L
" Fill what's empty, empty what's full, and scratch where it itches."
';78 Tranzporter 2L
" Fill what's empty, empty what's full, and scratch where it itches."
- dingo
- IAC Addict!
- Location: oregon - calif
- Status: Offline
from Chiltons VW 1970-1981 page 70
72-73 Bus w/ Type 4 1679cc CR : 7.3 : 1 HP: 63/4800 , Torq:81/3200
'71 411 w/Type 4 1679cc CR 8.2: 1 HP 85/5500, Torq: 99.5/3500
'72-'73 914 w/Type 4 1679cc CR 8.2:1 HP 76/4900, Torq: 95/2700
'73 914 Calif. " 1679cc CR 7.3: 1 HP 69/5000, Torq: 87/2700
72-73 Bus w/ Type 4 1679cc CR : 7.3 : 1 HP: 63/4800 , Torq:81/3200
'71 411 w/Type 4 1679cc CR 8.2: 1 HP 85/5500, Torq: 99.5/3500
'72-'73 914 w/Type 4 1679cc CR 8.2:1 HP 76/4900, Torq: 95/2700
'73 914 Calif. " 1679cc CR 7.3: 1 HP 69/5000, Torq: 87/2700
'71 Kombi, 1600 dp
';78 Tranzporter 2L
" Fill what's empty, empty what's full, and scratch where it itches."
';78 Tranzporter 2L
" Fill what's empty, empty what's full, and scratch where it itches."
- Bleyseng
- IAC Addict!
- Location: Seattle again
- Contact:
- Status: Offline
You can just have the head decked to raise the CR but what cam are you using? The stock cam barely works with the stock CR of 7.3 to 1 as is causing high cylinder head temps under load (375-450F) which kills the aluminum head over time. Raising the CR will result in higher temps...so have you done you calculations to determine what you have now. Measure the deck ht, CC the heads and piston dish etc to figure it out.dingo wrote:I already have the stock pistons....i was wondering if there was a way by shimming the jugs.....(i may be way off the track here)
Ill preface by saying that im not an expert on this subject: I believe higher compression ratio will give you more h-p or torque or both...i already mix up my own octane cocktails, so i thought i would experiemnt on the next 2L engine i put togetherThis may be a stupid question, but why would you want to do this?
BTW I am running USA914 94mm pistons but with 1800 heads and keep the CR at 7.5 to 1.
Geoff
77 Sage Green Westy- CS 2.0L-160,000 miles
70 Ghia vert, black, stock 1600SP,- 139,000 miles,
76 914 2.1L-Nepal Orange- 160,000+ miles
http://bleysengaway.blogspot.com/
77 Sage Green Westy- CS 2.0L-160,000 miles
70 Ghia vert, black, stock 1600SP,- 139,000 miles,
76 914 2.1L-Nepal Orange- 160,000+ miles
http://bleysengaway.blogspot.com/
- bottomend
- Hardliest Working Man In Show Business
- Status: Offline
Wow. Bleyseng, I would've thought your CR was higher.
Dingo> go over to westy78's thread and look at the pics of him CCing the heads and pistons. He made a disc of plastic that fit's into the bore of the head and seals it with a little grease.
There is a small hole drilled in the center of the disc in order to inject colored liquid ( easier to see againts the aluminium head) into the space now created by the disc, which acts like a roof. The syringe used is graduated so he can observe exactly how much liquid it requires to fill up the void. This # represents the volumn of the space. Most heads should be around 50-55cc. Most piston dishes are around 12-15 cc.
All the numbers need to match between componants or the combustion chambers will be uneven in size, which in turn causes an unbalenced engine. If the chambers are even and the rotating parts of the engine are balenced the sukka should purr like a kitten.
I've got to get over to Sluggos house to record a snippet of his engine. We didn't balence the rotating mass but we did balence the recipocating parts and CC'd the chambers and pistons. They were EXACT... and it produced really sweet results.
Dingo> go over to westy78's thread and look at the pics of him CCing the heads and pistons. He made a disc of plastic that fit's into the bore of the head and seals it with a little grease.
There is a small hole drilled in the center of the disc in order to inject colored liquid ( easier to see againts the aluminium head) into the space now created by the disc, which acts like a roof. The syringe used is graduated so he can observe exactly how much liquid it requires to fill up the void. This # represents the volumn of the space. Most heads should be around 50-55cc. Most piston dishes are around 12-15 cc.
All the numbers need to match between componants or the combustion chambers will be uneven in size, which in turn causes an unbalenced engine. If the chambers are even and the rotating parts of the engine are balenced the sukka should purr like a kitten.
I've got to get over to Sluggos house to record a snippet of his engine. We didn't balence the rotating mass but we did balence the recipocating parts and CC'd the chambers and pistons. They were EXACT... and it produced really sweet results.