Bliue dm Posted July 29, 2020 Share Posted July 29, 2020 Ok. So i just recently purchased a 97 688s with a e7 400. Semi electric. Its only making 25psi boost. I know our etech 400 is making around 32psi. Is my boost preasure off our is 400hp achieved thru timing? Or is my boost preasure low? Quote Link to comment Share on other sites More sharing options...
Bliue dm Posted July 29, 2020 Author Share Posted July 29, 2020 I would like to also know the difference between it and other e7 400. There is so much on this topic like. I hear some of these engines have two piece pistons... Some people say the compression ratio are different but when you look at a mack chart you see thats not true? Quote Link to comment Share on other sites More sharing options...
brettj3876 Posted August 4, 2020 Share Posted August 4, 2020 On 7/29/2020 at 7:13 PM, Bliue dm said: I would like to also know the difference between it and other e7 400. There is so much on this topic like. I hear some of these engines have two piece pistons... Some people say the compression ratio are different but when you look at a mack chart you see thats not true? Your boost sounds a bit low. Think it should be 28 at the min to 32. Don't have the book in front of me now. They have 2 piece piston. Steel top/alum skirt. Give mack the ser# to find out what comp pistons it has. They were all over the place in diff years. For example the 93's 250-400 all had 16.9:1 (conflicting info around) some literature says 375 and up 15.3 and below that 16.5 but mack had changes over the yrs. One book said our 93 was 16 5 and another 16.9. It ended up being 16.9:1 (591 tops) I doubt it's 16.9 could be 16.5 15.7 or 15.3 Quote Link to comment Share on other sites More sharing options...
JoeH Posted August 4, 2020 Share Posted August 4, 2020 My 95 e7-350 (all mechanical) tops out at about 25 psi boost. It has trouble getting out of it's own way, but it gets where it's supposed to go. Will make 1200+ degrees EGT, though I try not to push that number. I just assume it's working as it should.... Quote Link to comment Share on other sites More sharing options...
brettj3876 Posted August 4, 2020 Share Posted August 4, 2020 2 hours ago, JoeH said: My 95 e7-350 (all mechanical) tops out at about 25 psi boost. It has trouble getting out of it's own way, but it gets where it's supposed to go. Will make 1200+ degrees EGT, though I try not to push that number. I just assume it's working as it should.... Post turbo probe? I would keep try to keep it under 1050. Our says 1025 max and 99 says 1100 max. 1200 won't hurt it for short bursts but deff don't pull a couple mile grade like that Quote Link to comment Share on other sites More sharing options...
Bliue dm Posted August 6, 2020 Author Share Posted August 6, 2020 On 8/4/2020 at 12:51 AM, brettj3876 said: Your boost sounds a bit low. Think it should be 28 at the min to 32. Don't have the book in front of me now. They have 2 piece piston. Steel top/alum skirt. Give mack the ser# to find out what comp pistons it has. They were all over the place in diff years. For example the 93's 250-400 all had 16.9:1 (conflicting info around) some literature says 375 and up 15.3 and below that 16.5 but mack had changes over the yrs. One book said our 93 was 16 5 and another 16.9. It ended up being 16.9:1 (591 tops) I doubt it's 16.9 could be 16.5 15.7 or 15.3 I will get serial number 4 you... its suppose to be a 400. Sounds like it can use a valve adjustment. Quote Link to comment Share on other sites More sharing options...
Bliue dm Posted September 2, 2020 Author Share Posted September 2, 2020 9d Quote Link to comment Share on other sites More sharing options...
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