Rods and Pistons

[papa roached]

is it better to have OE piston with strong rod or high strength piston with OE rod in a mostly stock turbo motor, i know both is better but im just curious

[maldo]

With proper tuning, your rods will fail before your pistons do. The rods are weak to begin with, the pistons aren't. One of the weakest parts of the rod is actually the rod bolt which doesn't have the tensile strength to support the high hp demands. If money is a factor, get some good rods and keep the stock pistons. I would suggest Crower for the money as they can handle just about anything that is thrown at them. They are superior to Pauter from an engineering stand point but that doesn't always matter in real life. No one has reported failures with Pauter in the way that they should based on their design.

[papa roached]

k, thanx, im gathering stuff for my SOHC turbo project and i wan gonna get a shortblock to put in there and was wondering if i should change the rods for higher than 8 lbs of boost, thanx

[maldo]

If you are going higher than 12psi, than yes for longevity of the engine. Otherwise, you should be fine...no guarantees though.

[papa roached]

i will do it anyway, becuase 10lbs and frequent excursions to redline can take its toll

[jaydog5678]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by maldo:
With proper tuning, your rods will fail before your pistons do. The rods are weak to begin with, the pistons aren't. <hr></blockquote><p>Even with the best tunning money has to buy, do you think the rods will fail at 15psi??<p> <blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by papa roached:
i will do it anyway, becuase 10lbs and frequent excursions to redline can take its toll<hr></blockquote> <p>With increasing rpm's come higher inertial loads.

[maldo]

I have seen them fail at 10psi in both the B6 and BP. Do you feel lucky? Unfortunately Mazda realized that the B6T rods were extremely overkill for the NA B6 and BP so they used the newer, lighter version which is prone to failure when boosted.

[ProtegeSTS]

my opinion is that they are mostly tuning errors...<p>As has been shown by people like Lauzier and Ric, stock blocked BPs can handle serious power.<p>Just my 2 cents.<p>The later B6s CANNOT, and are weak, as Chris said.

[OsoSlo z28]

the 1.8 gtx uses the same rods as the n/a bp and are known to hold upwards of 20psi and/or 400+hp.

[ProtegeSTS]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by cre8v mx3:
the 1.8 gtx uses the same rods as the n/a bp and are known to hold upwards of 20psi and/or 400+hp.<hr></blockquote><p>
Or in the case of braden, upwards of 900 psi... because the turbo is so small, and is as such poor efficiency at that level, that it actually has reverse flow...<p>(inside joke if you know Braden..., not otherwise true)

[OsoSlo z28]

haha....now that's funny.

[maldo]

Like I said, I have seen them fail as low as 10psi. Boost levels really aren't the determining factor here. Look at all the '99 model BPs with thrust bearing failure, just a simple machining error that Mazda likes to deny. The rods themselves aren't always the problem though, the bolt is the weakest point structurally. The bearings also tend to deteriorate at a quick rate, soon sending the rod thru the block.

[jaydog5678]

Speaking of bolt's and studs, I'm a firm believer in doing things right the first time. For me, I just didn't have the funds to sink any more money into the BP-t. I would have liked to replace all of the bolt's with studs, including the cyl head bolts just to insure everything was going to stay put. I did'nt, and I regret it for my engines sake.<p>When I built the engine, I was concerned with how much I had to torque these bolts in order to achieve a good oil clearence. I later read that over torqueing the bolts would result in lowering the tensile strength of these bolts; certainly not a good thing. I did'nt torque them but 6-8ftlbs over per bolt using the fatory specs. This included main and rod bearing bolts. This put some doubt in my mind as to how well this was going to hold up. Any thoughts?

[maldo]

When I rebuilt my B6T I was re-using the factory bolts. I didn't have my torque wrench with me so I used my gf's Dad's wrench which is fairly old. Obviously it wasn't calibrated properly as I snapped one of the bolts, believe it or not I only went about 10ft-lbs too far. I switched to ARP head studs after that.

[UnkleDuke]

In this discussion about rods and such...I'm having second thoughts about boosting my 92 RS. It has about 190 000 on it. I am wondering about these claims about the sohc being able to run up to ten pounds boost with proper fueling and cooling.
Any thoughts?