 7A-FE Compression Ratio, Looking at changing the CR of my 7afe when I rebuild. |
 Mar 30, 2012 - 12:00 AM
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 Enthusiast  Joined Mar 15, '12 From Wrightstown, NJ Currently Offline Reputation: 6 (100%)  |
Hey all, I'm trying to decide what to do with my 7AFE (have to take it apart due to a rod knock anyway). I've kicked around a few ideas (or maybe a lot
 ), and I'm currently researching what an increase in compression ratio might do. Does anyone have any info on this? I'm unsure of the potential difference in performance, and I can't seem to find any hard data on what pistons (4age, smallport 4age, 4agze) result in what CR. I've been trying to make sense of these tools and formulas - http://www.csgnetwork.com/compcalc.html http://s-86.com/s-cr.html and http://s-86.com/s-cr-chart.html - but I'm having a hard time digging out the relevant numbers. Doing the math myself or using the calculator I come up with significantly different numbers than their little handy chart, so I don't know what to think. Is this a futile exercise? Will I even be able to notice a performance difference over the stock 9.5:1 without having to use higher octane?-------------------- 1989 Celica ST Automatic "King Cobra" -- 2005-2006
1994 Celica ST 5-speed "King Cobra II" -- 2011-???? |
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Replies
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May 3, 2012 - 5:37 PM
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Enthusiast Joined Mar 15, '12 From Wrightstown, NJ Currently Offline Reputation: 6 (100%) |
QUOTE (mandrek @ May 1, 2012 - 11:42 PM)  there are no ARP bolts/studs that fit the 7afe stock rods.. you will have to go after-market rods or just get a fresh set of stockers.. Is that definite? I'm not being rude or challenging, just trying to find out for sure... Different people say different things, you know!  I've seen some posts like these that say they'll work, and heard hearsay along the lines of "they'll work but you have to work on the block a little to keep them from contacting it during the stroke".... ... But it's probably a moot point anyway, as it's most likely not going to be boosted at all... However, there are no guarantees of how high I'll be revving it, or how often during the course of just fooling around during random driving, and the state of the main bearings and rod bearings make me nervous. I just wish I knew what caused the damage, that would ease my mind a bit... QUOTE (mandrek @ May 1, 2012 - 11:42 PM) and IMO if you are not planning on boosting the 7a, then a fresh stock set of rod bolts will do fine.. and even if you are, a fresh set will work well for low boost (as far as my research shows), but if you are wanting to go as far out as you are indicating, then just get your self a set of belfab rods and have them include ARP2000 units with them. (an option you can request).. the cost on the rods is not that much (compared to aftermarket rods for other applications) I will end up just using fresh 7a bolts, though, if there are no reasonable alternatives between that and forged rods. -------------------- 1989 Celica ST Automatic "King Cobra" -- 2005-2006
1994 Celica ST 5-speed "King Cobra II" -- 2011-???? |
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May 4, 2012 - 12:47 PM
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 Enthusiast Joined Oct 29, '11 From Haltom City, Texas Currently Offline Reputation: 1 (100%) |
QUOTE (PaukST @ May 3, 2012 - 5:37 PM) QUOTE (mandrek @ May 1, 2012 - 11:42 PM) there are no ARP bolts/studs that fit the 7afe stock rods.. you will have to go after-market rods or just get a fresh set of stockers.. Is that definite? I'm not being rude or challenging, just trying to find out for sure... Different people say different things, you know! I've seen some posts like these that say they'll work, and heard hearsay along the lines of "they'll work but you have to work on the block a little to keep them from contacting it during the stroke".... ... But it's probably a moot point anyway, as it's most likely not going to be boosted at all... However, there are no guarantees of how high I'll be revving it, or how often during the course of just fooling around during random driving, and the state of the main bearings and rod bearings make me nervous. I just wish I knew what caused the damage, that would ease my mind a bit... QUOTE (mandrek @ May 1, 2012 - 11:42 PM) and IMO if you are not planning on boosting the 7a, then a fresh stock set of rod bolts will do fine.. and even if you are, a fresh set will work well for low boost (as far as my research shows), but if you are wanting to go as far out as you are indicating, then just get your self a set of belfab rods and have them include ARP2000 units with them. (an option you can request).. the cost on the rods is not that much (compared to aftermarket rods for other applications) I will end up just using fresh 7a bolts, though, if there are no reasonable alternatives between that and forged rods. Probably a PO who didnt keep up with the oil changes. At least your cylinder bores are nice and clean. As for the rods, 4 cylinder engines are hard on the rods. Thats why you dont see big displacement I4s even though they produce superior torque to a equal sized 6 or 8 cylinder |
Posts in this topic
PaukST 7A-FE Compression Ratio Mar 30, 2012 - 12:00 AM
Bitter 9.5:1
Will need cams too
Tune
Higher octane Mar 30, 2012 - 7:31 AM PaukST My initial thoughts were to replace the 7AFE pisto... Apr 2, 2012 - 2:07 AM Smaay dont bother trying to drop in 4A parts. its not wo... Apr 2, 2012 - 11:51 AM PaukST Hm, I guess it may just be the wrong route to go f... Apr 2, 2012 - 1:58 PM stephen_lee import performance parts . net sell "HP KITS... Apr 3, 2012 - 2:27 PM Smaay the problem is you have a 7A-FE, that was the econ... Apr 4, 2012 - 8:58 AM PaukST QUOTE (Smaay @ Apr 4, 2012 - 9:58 AM... Apr 4, 2012 - 11:33 PM Smaay did you see the thread i made in the stickys? its ... Apr 5, 2012 - 9:24 AM Special_Edy My local import machine shop charges $35 to d... Apr 5, 2012 - 12:37 PM
mandrek QUOTE (Special_Edy @ Apr 5, 2012 - 1... Apr 5, 2012 - 10:17 PM Special_Edy QUOTE (mandrek @ Apr 5, 2012 - 10:17... Apr 6, 2012 - 11:47 AM PaukST As far as I can tell, it would only take 3cc less ... Apr 5, 2012 - 5:38 PM Special_Edy Just have it decked. Do the stock rebuild.
You are... Apr 5, 2012 - 7:43 PM richee3 QUOTE (Special_Edy @ Apr 5, 2012 - 7... Apr 5, 2012 - 8:00 PM Bitter timing advance is similar to a compression increas... Apr 5, 2012 - 9:41 PM PaukST Given what Smaay mentioned about the one he tore d... Apr 5, 2012 - 10:36 PM PaukST It looks like reducing the chamber height by ~ .5m... Apr 6, 2012 - 11:35 PM Special_Edy QUOTE (PaukST @ Apr 6, 2012 - 11:35 ... Apr 7, 2012 - 12:50 AM celica74 Let us know what you decide to do, the progress an... Apr 20, 2012 - 11:01 AM Special_Edy QUOTE (celica74 @ Apr 20, 2012 - 11... Apr 20, 2012 - 11:23 AM celica74 QUOTE (Special_Edy @ Apr 20, 2012 - 12... Apr 20, 2012 - 2:41 PM Bitter with 15 degrees total base advance (+5 from stock)... Apr 21, 2012 - 1:45 PM celica74 QUOTE (Bitter @ Apr 21, 2012 - 1:45 ... Apr 22, 2012 - 9:10 PM Special_Edy Well and besides the price of higher octane, lower... Apr 21, 2012 - 2:13 PM Bitter I think it'll turn all the way to 25 but the g... Apr 22, 2012 - 9:29 PM Special_Edy QUOTE (Bitter @ Apr 22, 2012 - 9:29 ... Apr 23, 2012 - 1:35 AM celica74 QUOTE (Special_Edy @ Apr 23, 2012 - 2... Apr 23, 2012 - 7:16 AM celica74 QUOTE (Special_Edy @ Apr 23, 2012 - 2... Apr 23, 2012 - 7:16 AM Bitter I found 15 deg gave me more low end actually, ther... Apr 23, 2012 - 7:34 AM celica74 QUOTE (Bitter @ Apr 23, 2012 - 7:34 ... Apr 23, 2012 - 8:45 PM Bitter What year is yours? I never heard knock, I monitor... Apr 23, 2012 - 8:58 PM celica74 QUOTE (Bitter @ Apr 23, 2012 - 8:58 ... Apr 23, 2012 - 9:48 PM celica74 QUOTE (Bitter @ Apr 23, 2012 - 9:58 ... Apr 25, 2012 - 7:31 AM Bitter http://www.contactmagazine.com/Issue54/EngineBasic... Apr 23, 2012 - 9:09 PM Bitter Did you set the base timing correctly and check wi... Apr 23, 2012 - 10:44 PM mandrek umm IIRC correctly its TE1 and E1, in the dieg por... Apr 24, 2012 - 12:19 PM Special_Edy Another thing to add- make sure your idle is 650-7... Apr 24, 2012 - 1:21 PM mandrek indeed, and assuming that the tension on the throt... Apr 24, 2012 - 1:38 PM celica74 Ha more things to do then i thought. Ive been driv... Apr 24, 2012 - 1:54 PM Bitter But did you have the pins jumped on a hot engine w... Apr 24, 2012 - 9:39 PM celica74 QUOTE (Bitter @ Apr 24, 2012 - 10:39... Apr 24, 2012 - 9:46 PM Bitter Fine, but were the pins jumped? Apr 24, 2012 - 10:59 PM celica74 QUOTE (Bitter @ Apr 24, 2012 - 10:59... Apr 25, 2012 - 12:01 AM Bitter QUOTE (celica74 @ Apr 25, 2012 - 12... Apr 25, 2012 - 7:17 AM PaukST Got my engine fully apart, I'll put up pics or... May 1, 2012 - 12:18 AM celica74 QUOTE (PaukST @ May 1, 2012 - 1:18 A... May 1, 2012 - 2:13 PM Special_Edy I think he meant having the block or heads milled.... May 1, 2012 - 2:28 PM PaukST QUOTE (Special_Edy @ May 1, 2012 - 3... May 1, 2012 - 10:10 PM mandrek there are no ARP bolts/studs that fit the 7afe sto... May 1, 2012 - 10:42 PM celica74 QUOTE (mandrek @ May 1, 2012 - 10:42... May 1, 2012 - 11:58 PM mandrek CAN you? yes. its is worth it? NO... sure you c... May 4, 2012 - 12:35 PM richee3 ^^ I love inline engines May 4, 2012 - 1:16 PM Special_Edy QUOTE (richee3 @ May 4, 2012 - 1:16 ... May 4, 2012 - 2:02 PM PaukST QUOTE (mandrek @ May 4, 2012 - 1:35 ... May 4, 2012 - 4:59 PM Special_Edy Id replace the oil pump while you have it apart. S... May 4, 2012 - 6:53 PM |
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