Shot peening connecting rods & why..

[88Accord-DX]

Shot peening is a cold working process in which the surface of a part is bombarded with small spherical media called shot. Each piece of shot striking the material acts as a tiny peening hammer, imparting to the surface a small indentation or dimple. In order for the dimple to be created, the surface fibres of the material must be yielded in tension. Below the surface, the fibres try to restore the surface to its original shape, thereby producing below the dimple, a hemisphere of cold-worked material highly stressed in compression. Overlapping dimples develop an even layer of metal in residual compressive stress. It is well known that cracks will not initiate or propagate in a compressively stressed zone. Since nearly all fatigue and stress corrosion failures originate at the surface of a part, compressive stresses induced by shot peening provide considerable increases in part life. The maximum compressive residual stress produced at or under the surface of a part by shot peening is at least as great as half the yield strength of the material being peened. Many materials will also increase in surface hardness due to the cold working effect of shot peening.
Benefits obtained by shot peening are the result of the effect of the compressive stress and the cold working induced. Compressive stresses are beneficial in increasing resistance to fatigue failures, corrosion fatigue, stress corrosion cracking, hydrogen assisted cracking, fretting, galling and erosion caused by cavitation. Benefits obtained due to cold working include work hardening, intergranular corrosion resistance, surface texturing, closing of porosity and testing the bond of coatings. Both compressive stresses and cold working effects are used in the application of shot peening in forming metal parts.

Pics of shot peened rods.

http://www.valvers.com/20xe/images/rods/deseamrods02.jpg

http://www.valvers.com/20xe/images/rods/deseamrods03.jpg

http://www.valvers.com/20xe/images/rods/deseamrods04.jpg

http://www.valvers.com/20xe/images/rods/deseamedrods05.jpg

[mykwikcoupe]

questions Ive tey to get conclusive info on. Youll notice the grains in those shot peened pics. Is it worth while to have it micropoliahe afterwards to even eliminate those? Afterall you are trying to eliminate any possible existing crack or whatever. Another thought, after the peeneing process is it neccassary to have them rebalanced?

Oh and man those are pretty, where did you go and how much. Thats what Im doing but cant find a local shop

[88Accord-DX]

Whether are not Honda Corp. use Cygentics as part of their manufacturing process is beyond my knowledge.


Is it worth while to have it micropoliahe afterwards to even eliminate those? Afterall you are trying to eliminate any possible existing crack or whatever. Another thought, after the peeneing process is it neccassary to have them rebalanced?

Oh and man those are pretty, where did you go and how much. Thats what Im doing but cant find a local shop
I'm not sure on the micropoliahe question. Yes, most shops balance rods after shot peening. Them pics aren't my particular rods. I just wanted to show a good example of them. I was told that my rods where shot peened by someone before. Here are some pics of my rods, but the shot peened isn't clearly seen & to the extent of the previous pics. I'm not sure on the price to have them done either.

http://img.photobucket.com/albums/v488/ddude2uc/newpistonsonrods.jpg

[mykwikcoupe]

sorry about my typing I meant to say micropolished after the peening process

[88Accord-DX]

sorry about my typing I meant to say micropolished after the peening process
I don't think micropolishing is part of shot peening process. I beleive it's just removing the rough edges that are proned to cracks, while the shot peening process hardens the the steel.

[AccordEpicenter]

micropolishing is what the do to the journals of cranks etc. Shot peening works wonders on stock rods. You can also polish your rods for a measure of strengthening also, but id bet that the shot peening is better

[mykwikcoupe]

micropolishing is after the shotpeening to further inhance the overall product. Id agree shotpeening by itself is better between the 2 but micropolishing might do something afterwards.

Anyone know what the hp strength of a shottpeened accord rod is?

[Justin86]

yea polishing does help due to limiting stress raisers like the rough casting surface. Becareful cause this also reduces surface area and the ability of parts to cool so the block should never be polished.

cryotreating would also be a good idea with cast parts.
Another thing to do is low friction coatings for bearing surfaces and pistons. It dosn't seem to be really popular in the sport compact group, but the V8 crowd and racers are all over this stuff and it relatively cheap too.

If you guys really look in to engine buliding, there is a good amount of little tricks to help with engine longivity and performance. You might have to buy a couple books and talk to guys that build race motors for a living but you wil find out a lot.

[AccordEpicenter]

Honda has made bearings in some B series engines that were coated with a fine coating of these pyramid shaped crystals that helped retain oil better in the bearing/journal reducing friction and wear. Anti friction coatings on piston skirts help also, so does knurling the piston skirt. Cryotreating i hear works good too especially on gears/gearboxes but it is spendy. I dont see why you couldnt get atleast 400hp on the stock shotpeened rods if the rev limit was kept at 7k or below, they are actually pretty beefy for stock pieces.