High compression pistons, need forged rods?

[MIKe30]

Im using weisco's for my e36 turbo build. Ipp sells them cheap, but they have a 5 week waiting period for custom cuts. They have rods for cheap also. As a matter of fact I'm sourcing almost 100% of my motor parts from them. P.S, lemme get that pic of the door.

I'm gonna take that pic in few minutes :)

Your rods will bend somewhere north of 600rwhp with proper tune. I wouldn't sweat it.:pimp:

Well I should be pushing close to that NA so looks like I'll be getting some new rods Funny you said that, I have a pm at about the same time as your post over on e30tech mentioning the same exact thing. The pm mentioned ICS bending the rod at 600. can you imagine 600 na in an e30!? wouldn't even be able to get out of your driveway...

the advantages to aftermarket rods is usually strength, S50 rods are already pretty light.

ah, gotchya. thanks.

The pistons are CP - got them through VAC.
The head I bought mostly completed and pieced the rest together. It's got Schricks, +1mm stainless valves, ti retainers, port/polish.


It sounds like you're doing a pretty similar build to mine. I plan on talking to Matt (Racer's Market) from this board when the time comes, as he does custom chips.

I'm staying obd2 and as of right now TRM only does obd1 tuning. They do have some pretty sweet set ups on their website (i.e. that multi-variable tune at the turn of a nob!)

Interesting, have a link to the bf.c wiseco thread? I'm gonna search it now. Also, why grinded? Shot peened is weighed/balanced? Pardon my ignorance, you can tell I have plenty of reading to do...

a machine shop will smooth out the ridges and then shot peen them for added strength, not a have to, but why not. of course balance them. the thread on bfc was in the fi section, sigma and someone else were having problems with there specs and a few others chimed in as well. plus the fact that vac stocks the cps is alot better then waiting 3-4 weeks and possibly having a wrong part.

Thanks for clearing that up. Yea, vac stocks the cps, but iirc they only had 11:1 or 13:1 in stock. There was an option for custom compression for an extra $50.



So now it's a matter of deciding 11:1 or 11.5:1. Also, I believe I read somewhere stock clearances are .007 - .015, should I be telling the builder what I want them to be at? What should they clearance be with aftermarket pistons and higher compression?

[mazur]

Haha, that's funny. The guy who runs ICS is pushing 730rwhp out of his MCoupe right now with his twin turbo'd S52 with stock internals. He runs it hard and it's still running great since last I heard.

Check youtube for vids, some are pretty funny. This one's my favorite - http://www.youtube.com/watch?v=JeLS3OX_7go

[MIKe30]

Haha, that's funny. The guy who runs ICS is pushing 730rwhp out of his MCoupe right now with his twin turbo'd S52 with stock internals. He runs it hard and it's still running great since last I heard.

Check youtube for vids, some are pretty funny. This one's my favorite - http://www.youtube.com/watch?v=JeLS3OX_7go

That's a nice MCoupe. Guy recording sounds so unintelligent cursing every 2.5 words.

[mazur]

That's a nice MCoupe. Guy recording sounds so unintelligent cursing every 2.5 words.

The guy recording used to work for the MCoupe owner, tuning cars I believe, and now runs his own shop catering mostly to Evo's and Subaru's. I think he tries to be gangster and says "bro" way too much

[mentaleeill]

I'm gonna take that pic in few minutes :)

Well I should be pushing close to that NA so looks like I'll be getting some new rods Funny you said that, I have a pm at about the same time as your post over on e30tech mentioning the same exact thing. The pm mentioned ICS bending the rod at 600. can you imagine 600 na in an e30!? wouldn't even be able to get out of your driveway...

ah, gotchya. thanks.

I'm staying obd2 and as of right now TRM only does obd1 tuning. They do have some pretty sweet set ups on their website (i.e. that multi-variable tune at the turn of a nob!)


Thanks for clearing that up. Yea, vac stocks the cps, but iirc they only had 11:1 or 13:1 in stock. There was an option for custom compression for an extra $50.



So now it's a matter of deciding 11:1 or 11.5:1. Also, I believe I read somewhere stock clearances are .007 - .015, should I be telling the builder what I want them to be at? What should they clearance be with aftermarket pistons and higher compression?

you shold get the pistons and give them to the builder with the block. that way there's nobody else to blame if they don't fit.

[matt]

Pistons come with their own specs. Forged pistons expand more as they get heated, so cold clearances are larger than stock.

[MIKe30]

you shold get the pistons and give them to the builder with the block. that way there's nobody else to blame if they don't fit.

Pistons come with their own specs. Forged pistons expand more as they get heated, so cold clearances are larger than stock.

ah, ok - didn't realize they came with their own cut sheet. Yea I was reading a little bit about piston slap, apparently caused by cold forged pistons slapping the cylinder walls before the motor warms up to operating temp.

any thoughts on 11:1 vs 11.5:1? reliability, longevity, power output, etc?

thanks again.

[matt]

More compression = less longevity and slightly more power. If you're building a pump gas motor, you might be OK with either of those, but probably not much higher.

[nando]

piston slap isn't a big deal if you get higher sillicone content (~15% or so). the sillicone makes them more brittle (not great for boost, but fine for na) but it makes them expand less. I've never had piston slap in 30,000 miles with forged pistons (Weisco/MM).

[MIKe30]

More compression = less longevity and slightly more power. If you're building a pump gas motor, you might be OK with either of those, but probably not much higher.

I think 11.5 is the limit and what I'm leaning towards. Obviously I don't know first hand, but I don't think it'll shorten the life of the motor significantly - and at the same time, it probably won't be too much of a significant bump in power either. Guess I'll have to find out the hard way.

piston slap isn't a big deal if you get higher sillicone content (~15% or so). the sillicone makes them more brittle (not great for boost, but fine for na) but it makes them expand less. I've never had piston slap in 30,000 miles with forged pistons (Weisco/MM).

Interesting. I'm assuming weisco and wesico are the same brand, just everybody makes a typo?

[MIKe30]

Any dyno's to back that up? Not calling you out, I just thought I remembered reading threads with less than 250 on that setup.

How do the Sunbelt's affect the TQ curve? Is dead down low and a screamer up top? That may suck for something you drive on a regular basis.

http://forums.bimmerforums.com/forum/showpost.php?p=11001723&postcount=245

I pm'd him, that dyno was on the sport cams NOT the race cams :D

I know he said IP, but I asked him anyway if that was on stock compression. We'll see what he says. He also said in his first reply that the motor felt like it got stronger as it broke in more. He totaled the car it was in, now it's going in an e30! He said he can't wait to dyno it after it's in the 30.

-mike

[z31maniac]

That's fucking nice!

[GGray]

Sunbelt cams

Be aware you cannot spin the sunbelts as high as advertised without grenading the motor... LOTS of problems with club racers using them and popping motors. They may have the issues under control now but they were pretty bad at first...

With OBD2 you will be lucky to crack mid 260whp... You REALLY need to switch to OBD1 so you can get a TRM custom dyno tune. That alone will be good for probably 10-15hp over an off the shelf fash.

I am planning on building a solid lifter 3.0 alum block engine ( lighter) for mine this summer with CAT CAMS mechanical lifter cams, unless I can find another cam source for the mechanical lifter cams. Rev limit will depend on power peak.

If you have not bought pistons try to find a M52B28 alum engine. Use the S52 crank and custom pistons you end up with 3.0 and 30-40 lb lighter motor.... Thats my plan...

[MIKe30]

Be aware you cannot spin the sunbelts as high as advertised without grenading the motor... LOTS of problems with club racers using them and popping motors. They may have the issues under control now but they were pretty bad at first...

With OBD2 you will be lucky to crack mid 260whp... You REALLY need to switch to OBD1 so you can get a TRM custom dyno tune. That alone will be good for probably 10-15hp over an off the shelf fash.

I am planning on building a solid lifter 3.0 alum block engine ( lighter) for mine this summer with CAT CAMS mechanical lifter cams, unless I can find another cam source for the mechanical lifter cams. Rev limit will depend on power peak.

If you have not bought pistons try to find a M52B28 alum engine. Use the S52 crank and custom pistons you end up with 3.0 and 30-40 lb lighter motor.... Thats my plan...

Thanks for the heads up. I don't plan on going over 7k or 7.2k. The OBD2 tune that bimmerworld (AA tune) provides is off the shelf, then you can send back once for free with a dyno and they custom tune it for you. Dyno posted above was on 2nd try. Looks pretty decent to me. Not knocking TRM by any means, everybody swears by them! I actually contacted them in order to find out about obd2, which isn't quite ready yet. But getting back to your point, TRM would be no more custom than Bimmerworld. Both are remote, and trial and error really.

And yes, aluminum bottom end sounds sweet - but 30-40lbs isn't quite sweet enough for me to go through the trouble at this point.

[e30polak]

Invest in some euro headers if you can. The guy from bimmerworld said thart with head work and sunbelt race cams, they've seen between 8-14whp just from those. :nice:

And are you upgrading to the Dr. Vanos stage 2, and nice valve springs? I would.

Also you might as well get some bigger valves in there while your at it. :twisted: