legacycentral bbs

I was looking for some info for my OTHER project car, my 09 wrx, and ran across something interesting on the COBB website. They were talking about tuning engines that had been built with forged parts for durability and the fact that the stock detonation detection system is fairly aggressive. So they were outlining how to go about desensitizing the system via software in the ecu. Probably no surprise to some of you, I get that. But it was interesting to me. Then I thought, has anyone tried figuring out how to do this with the first gen turbo leggies? Just a thought....could also help for well built NA engines I would think. Any discussion, comments etc?

I can't advocate you do this, but I read about others relocating their knock sensors to the top back of the block. I did this myself a while back when I ran my built ej20g. It worked, but I spun a bearing after 40k miles. Though the exact cause is hard to pinpoint, I have always wondered if moving the knock sensor removed a layer of protection. Before I moved it, I couldn't hit 18 psi without the Robtune pulling timing.

+1 on the knock sensor to the top of the bellhousing....but I also was having other issues (later diagnosed as a cracked ringland) that probably were the main issue - stock block. But moving it allowed the RT to work better.

I'd think this would be more 'noted' on here if it were a common issue w/forged pistons as I think there have been a # of Wiseco, etc. forged pistons installed? So, I'd also NOT recommend it.

Ok, this is why this forum is such a valuable resource to me. Im running forged internals in an NA ej25d and the knock sensor is already mounted at the back of the block near the bell housing in the factory location. This begs the question if it would be worthwhile to move it forward and mount it in the same location the turbo EJ motors use. When the engine that just came out of that car was disassembled, #4 rod bearing was trying to spin and had begun to do so. hence, a new bottom end...included in the rebuild was the next to the largest oil pump available for that engine. I await the answers of the oracle...

I don't have any specific knowledge about moving the knock sensor any other place, but I am not aware of a different location for knock sensors on turbo cars?

What are you doing for engine management? I'm pretty sure any decent system would let you adjust the sensitivity of the KS. If you're running stock EM, then I suppose you could cheat the system by putting a very thin spacer between the KS and the block, but I'm uncomfortable with that idea as I mentioned above, since I think it removes a level of protection.

What Pistons are you running? And did your machine shop set a loose piston to wall clearance? Last time I used wisecos, they were audibly noisy till they warmed up, but even then, the KS was picking up their noise under higher boost.

As an aside, I always wanted to build up an N/A ej25 with ej255/257 block halves for added rigidity. My theory is the unsupported cylinder walls vibrated enough over time that they slipped on the head gaskets, eventually causing the BHG's we know and love. Just an unsupported theory.

Yeah I think there's a little of that but also the n/as came with garbage headgskets. They even kept putting the coated ones in the sohc 2.5s until the FA/FB came out, and still do if you go into a dealer for headgaskets. The phase 1 dohc gaskets are mls though. And ARP does make headstuds for sohc engines.

Anyhow, I've always kept the p/w clearance as close as possible even with forged pistons and I think that definitely helps. Some manufaturers recommend 0.0035 to .004" and that's just way too much. Even on the time attack engine we were at more like .003.

For what it's worth, my forged pistons have been pretty quiet and no issues with the knock sensor in the stock location. I have a secondary knock sensor/light from Link that is mounted on the bell housing and I'll get an occasional flicker of indication on deceleration, but I know that's just a false indicator.