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12-31-07, 14:47
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#1 (permalink) |
 
 
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FE3 overbore problem and solution for those with skill.
Hi,
foreword : This applies less to NA builds than turbo ones, but it STILL applies. The pressure from combustion and piston side load is increased with boost, but it is still significant at high rpm on an NA engine, particularly if stroked, and a weakness is a weakness. It regularly comes up that member XYZ wants to overbore his engine significantly. For a number of reasons this is a BAD idea. It is a bad idea despite what DJFake and Randy think about it. Any boring should be kept to a minimum. By that i mean that if the bore isnt scoured and is true you should just hone it and order 86.0mm pistons for it. If its scoured you should take the minimum overbore you can to get fresh pistons into it. Consider for a second that the amount of torque and power you gain is in the order of 5% at most, and the strength you lose is more like 30 - 50%. If you think of it like this you will quickly see why its a bad idea. This is amplified when you live in the US of A and have to import your engine and pay an extortionate price for it. Why take it to the max bore right off the bat? Why not leave it ready to rebore when your tuning efforts are shown to be less than adequate by a melted piston and scoured bore? The wall thickness of the bores on the FE3 are about 4 - 5mm thick, however the material is a rough cast finish on the coolant side, porous, and will vary in thickness and strength significantly. if you consider that its 4.5mm and you over bore 3mm taking 1.5 from each side, thats 33% of the wall gone assuming the wall was strong out to 4.5mm the whole way round which it just wont be. Add to this the fact that you want to make around 2 - 3 times the oem stock power and its apparent why its a terrible idea. The only good way to go to a larger bore is with custom or adapted liners. the block could be machined to accept these and a commercial liner of the desired bore could be obtained from a comparable rebuildable diesel engine. here are some pics of liner engines : how they look in the deck :   how they fit into the block :  and a close up :  hopefully this thread will serve to quite the overborers down somewhat :-) heres the link to what happens to your bore if you bore too much : http://www.mx6.com/forums/fe-dohc/16...k-anybody.html (cylinder crack - anybody?) in summary, leave your bore alone unless you know what you are doing :-) enjoy :-) fred. Last edited by fredio54 : 1-8-08 at 5:53. |
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12-31-07, 14:48
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#2 (permalink) |
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the broken engine is a cat v12 and the new one is our C series cummins.
i should mention that all serious engines that are designed to be rebuilt use liners like this. the throwaway automotive stuff we use is not really designed for the long haul. nothing to stop one of you taking the lead and doing it though :-) fred. |
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1-1-08, 18:42
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#4 (permalink) |
 
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totally agree with you fred, it's not worth gaining a very small percent of horsepower to weaken your engine's cylinder walls. If you need to bore it out and don't want to get another oem mazda block from overseas, then just locate a kia one.
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90 MX6 GT http://www.cardomain.com/ride/2036393
Stock: 15.446 @ 88.78 F2T Best: 12.71 @ 104 FE3T: 11.941 @ 99.03 (missed 4th) Best MPH: 12.24 @ 117.03 videos:http://videos.streetfire.net/uploaded/Shwine617.htm |
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1-2-08, 2:33
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#7 (permalink) | |
 
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Not from me. The block is stout enough as is with 86mm bore. Not to mention FWD with an open diff. Now maybe if I was doing what Fred is doing....different story.
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Quote:
Quote:
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1-2-08, 5:35
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#8 (permalink) |
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Fred do you no what the liners are made of and do you have picture of a liner out of a engine. My engine is built now . So im starting on a different build im thinking of going 102 stroke and bore out to the max and put in steel liners $4000 for the 102 stroke billit crank iv done a little reserch on over bore and stuff just tring to fine out info about liners . Perfect timing this thread fred
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1-2-08, 6:41
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#9 (permalink) | ||
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Quote:
one thing i would like to add is that it would be childs play to add a spacer on the block if you were doing this to aid in rod length and therefore make high rpm an ok proposition. at 102mm stroke, you will need titanium rods if you wanna spin any sort of half decent rpm. not spinning 7k + with a bucket style head is a damn waste if you ask me. the thing with the sleeves is that they arent cast and are consistent in their wall thickness and steel quality. not the case with oem cast bores. this sort of stuff is only needed if you want extreme power. i'm struggling to imagine wanting more power than 450hp from a 2.0 engine. if i wanted more i would step it up to the j series 3.0 v6 which IMO is an excellent rwd swap, or an rb30det or a 2jzgte or even a 1uzfe. but 400hp is quite a lot! just a little diet and the ute will run high 12's with that. who really needs more? Quote:
fred. |
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1-2-08, 18:11
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#10 (permalink) |
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Im looking at 600-650 whp with the motor i just built just the head cost me $7000 . So my aim in future is to go fast with th 2.0 or what ever i can get it out to .Do your best with what you have . Every body has 2j's RB30 RB26 ,FE3 sounds better and to much money spent on it To go different. In the laters ZOOM mag there is an write up on a 4G63 with a 102 stroke Manly I-beam rods it still revs it to 8500 with steel rods .
Last edited by Stroker : 1-2-08 at 18:17. |
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