Engine internal upgrade question.

[lonewanderer]

Hey guys, searched for a thread on this and couldnt find anything. Maybe I am wording the search weird, but I felt it may be easier to post a thread with my question. So. I eventually want to build a motor on the side of my current SR. I like the idea of a built motor, but not very fond of the maintenance in which comes with it. That being the case, I am looking to do a complete OEM upgrade to the engine. Keep it simple, reliable and still increase the HP. Obvious oil upgrades would be included, with s15 SR Parts (this is an s13 blacktop) as well as fuel like the simple z32 TT fuel filter upgrade.

I was looking to upgrade to VG30DETT pistons that are 87mm in diameter compared to that of the OEM SR at 86mm. I was also considering using KA24DE pistons, however, at 89mm I may have to resleeve the block which is expensive as you all know. My question is that due to the upgrade in piston size, does the stroke of the rod change? Would it be possible to use the SR rods, or would it be wise to use the rods from the engine I choose to take pistons from? Would also consider utilizing aftermarket rods with the pistons but would like to overall keep an OEM build upgrade due to the availability in parts still available for both engines and that it is significantly cheaper than aftermarket items.

This engine is for street and minor track purposes. The goal is to have an easy maintenance engine that is easy to rebuild in worst case scenarios where engine failure can occur. So if after a track day, I develop a rod knock or something, I am not x amount of dollars in the hole because of aftermarket parts. Pistons and Rods from any of these engines is far easier to stock pile in case of emergencies.

Thanks for looking guys

[d9m13n]

Build it once and build it right. Its not about having a stockpile of cheap oem internals you can throw in once something goes wrong. Rod failure? New block. Rod knock? new bearing, possible bearing resize, machine work. Piston failure? New piston, probably going to have cylinder damage. Gonna have to bore it anyways, then you need 4 new pistons of that size and machine work.

If you want to go the oem route, know the limits well and stay comfortably under them. Dont build the engine in your garage, its the easy route towards premature part failures unless you really know what youre doing. Take the engine to an experienced machinist who knows the sr well. Pay the (lots) of money for blueprinting and machine work and the peace of mind of having a well built engine.

Honestly, buy a built bottom end from a partout. Or buy used, forged, aftermarket internals and raise your power potential by far more than you can risk squeezing out of the oem internals, then take it all to an engine builder and get it done. This can be done over a long period. Buy my used CP 86.5mm sr pistons local to you and get a head start :hsdance:

To be honest, try to get 300 wheel out of your stock internal sr thats already in your car. It will take it well if you take care of it with periodic maintenance and care. Its more than enough to have fun and grow into the s chassis.

[lonewanderer]

I understand the principles of building an engine right, but like everything, shit happens and it could eventually go. But thank you for the input, I appreciate it! on the OEM note, VG30DETT have been known to push 500 hp before detonating. Now, I'm not saying I'm looking for 500 hp, Im thinking a tad over 400 but even that sounds extreme. Using z32 TT piston have been used before in upgrading an SR. Do you know if the piston size would change the piston stroke as well? I am assuming yes, but I am trying to learn and its not on the basis that I am cheap, its more so on the basis that I would like to be able to handle my own maintenance and do everything myself. Some of the best cars Ive seen were built in someones shed somewhere and I admire that. Its something I aspire to, Id like to move slowly away from having another person do stuff on my own vehicle, even engine rebuilding, if that makes sense

[tuzzio]

I guess I don't quite understand the advantage of using OEM z32 pistons over after market forged pistons designed for use with an SR.

Unless the valve reliefs, rod sizing/wristpins are identical I wouldn't even think about it.

That being said, what real maintenance do you have to do to forged pistons? Do built engines wear faster than OEM ones? Sure. But will they handle more abuse? Sure.

Z32 pistons (from the 2 minutes of googling I did) seem to be a cast piston, so with ANY detonation (tune related, not piston related) you MAY experience a similar ringland failure any cast piston would, where as a forged piston can handle that better.

Its just not the route I'd take. I also don't understand where KA pistons would come into play in this either.

What i'm really trying to say is, if you want to upgrade, buy forged pistons designed for use in an SR.

[Krusty_s13]

Someone can chime in if I am incorrect, but as I understand it, Stroke only changes with rod length and crank radius, see below;

https://upload.wikimedia.org/wikipedia/commons/thumb/3/36/Piston_motion_geometry.png/500px-Piston_motion_geometry.png

http://www.wisemanengine.com/images/equation1.gif

For the same rod length as a stock sr20, your stroke won't change if you use a z32 piston. Only issue would be if the distance from wrist pin center to top of piston is larger than the Sr20 piston dimensions, you may run out of room and make contact with the valves and/or head.

You would have to know how much room youd have, with the piston at TDC, between the top of the piston and the surface of the head and/or valves at their respective positions.

https://upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Squish_band.svg/220px-Squish_band.svg.png

If the z32 piston has the same dimension from wrist pin center to top of piston, then the only benefit would be a increase in piston diameter (bore) and a potential for a different ring land design.

Hope this helps somewhat.

[mewantkouki]

Vg30dett pistons are the same shit cast aluminum as sr / ka pistons. The material isn’t stronger, the two extra cylinders and the second turbo are what’s responsible for the increase in power. Higher hp will always be made easier on a larger engine.