Let's say I bought the RRM pistons and rods and have upgraded the fuel system and everything. What would be the maximum amount of boost it could handle?

Just curious.

 

For one thing, they aren't RRM pistons and rods, they just resell them from a supplier. I think the pistons are JE and the rods are Pauter. If I remember correctly Rob had the shop Lancer running at 14psi or something like that, but someone else will need to confirm it.

omarboy is running 15psi on aftermarket internals.

 

Basically running higher boosts is all about tuning. If you have the AEM and good fuel, good internals, good drivetrain... then you can tune for what you'd like. With the compression ratio of the motor i'd say you're looking at peaking around 18psi though as by that time you'll be pulling so much timing and adding so much fuel you'll be at a wall. If you decompress then you can go higher than that. Might be able to play with vlv timing as well to get you some extra ponies at lower boosts. It is really all about the tuning and what tuning capabilities the car has.

 

If they are Pauter rods and JE pistons, assuming you have the corresponding mods, you can boost pretty high. Although on the "baby" motor, the 1.8L, I have seen some insane boost levels on Pauter / Wiseco combinations....

 

My only concern at that point is the valvetrain. I don't know how strong the valve stems are, but I would fear for their well-being. At any rate, the pistons and rods willl add durability, but they are not infallable. Like Boe said it comes down to tuning, and proper fuel adjustment and timing are the keys to success.

 

I don't worry to much about the vlv's themselves though. They are stainless so they should actually hold quite well. For boost over 15psi i'd be more worried about the springs/retainers. Definately upgrade them so that you ensure a proper seat at higher boosts. It would be bad to have a vlv leak and float on you during that much boost with the high compression in our motors.

 

Ah great. Thanks for the info on the valves, Boe.

Now there's an understatement.

 

how much hp would you be looking at with those mods and then at 15psi boost?

 

260-280 at the wheels depending upon tuning method... aem280ish...emanage260ish.

 

thanks boe and that is mainly with everything that Roadracemotorsports offers am i right? i was thinking bout putting a nx ntercooler kit on my car after i got turbo in january, would that be a good idea or bad idea with all aftermarket parts..........and you said i would be at 260-280 depending on tuning but what bout with that ntercooler kit also?

 

hard to say... its something you'd have to try/dyno.

 

just as a side note Omar (omarboy) hit 20psi...

 

when did he do that... he was running 15psi bloody rich... now he's got the aem and is boosting 12psi. This is what he's told me. Maybe there is something new happening but he's on stock rods still so i don't think he pulled 20. His rods, new pistons, and head/cam are still waiting to be put on.

 

this question may be a little off topic but what are stock internals capable of holding as far as psi? i thought it was 9 safely but someone else told me its like 10 or 12 safely. What about HP? is there a HP number that our motors will be in danger of running?

 

I thought Boe and Rock had answered this already with their kit. "Safely" is kind of a subjective term when you think about it. You can safely push boost right up to the level of engine knock, but it really isn't that good for engine longevity. For the RRM Stage 1 kits, 7psi is the understood safe level even though those kits come set at 5psi. With engine management you might be able to run in the neighborhood of 10psi, but you're still pushing the envelope of rod life. If you see pictures of the rods (there are some floating around comparing them to the Pauter rods) you'll understand how stressing them won't lead to long life. The Nissan Spec-V guys know this all too well, because their stock rods are even thinner than ours.

One factor that's being overlooked would be the head bolts. If you're running high psi, more air is being compressed, so there is a high level of stress on the head bolts. I've seen cases of heads on Supras completely lifting off the the block, it's not a pretty sight. This will even affect non-stock internals, although I can't imagine changing internals and not changing to stronger head bolts. I would assume that the head bolts would outlast the rods under high stresses though.