SR20DET internals weaker link: stock rods or pistons?

[600supersport]

i know this has been discussed Many times as i've read through a lot of it. Im really looking for the opinions/advice from a consistent group of guys on here with a lot of helpful experience and info that i find here pretty often as im about to make my final decision on my short block rebuild in the next week or so...

i have an S13 redtop and rebuilt 5spd trans which god only knows how long will last in my zenki, but Z32 trans will wait til this trans blows and i rarely drag race.

im running 420-440whp, cosworth HG/ARP studs, BC springs, JWT S4 cams, tomei RAS, oil cooler and thanks to the stock oil pan dent i was stupidly unaware of from the previous owner while i was ripping 3rd gear up a steepish on-ramp, oil starvation spun the #2 rod bearing resulting in me adding a good stock crank, ACL race bearings/thrusts, ARP main studs, new oil pump/seal/pickup, isis oil pan, while cleaning/inspecting/measuring/honing/polishing everything on disassembly.

A few tweaks can probably get me another 50whp which is likely the max id ever take the SR anyway so this is probably just me being cheap, but the plan was to run $ into as much tracktime as possible on the road course this year, not more expensive parts just yet.

I obviously dont want to take the engine apart again anytime soon and who doesnt always want more power. I've read plenty of opinions about "stock internals holding 500whp" but i dont really know for what kinds of abuse and for how long tho some say lots of abuse for years so that's reassuring. then there's tons of people that say the stock rods/pistons are only reliable to 400whp, but a good tune is always important.

I really dont wanna throw $800+ for pistons and rods (unless i can find a good deal second hand which wouldn't be $800). Im leaning toward the manley rods for about $335 as people seem to mention stock rod weakness more often or if im fine with the stock rods/pistons. I cant find much good info about stock pistons strength, but i guess this is where im looking for some good advice and there's not many SR gurus locally.

[fliprayzin240sx]

All on the tuning...but honestly since you're already in there, might as well toss some Eagle Rods and Cp pistons. But if you're really on a budget, atleast buy fresh OEM rods and pistons. People have issues with these engine since they're all beat on in Japan.

Also, if you're on a budget, boring out the block to 87mm and running Z32 VG stock pistons is a good option over the stock SR pistons.

[Croustibat]

400WHP is already past what the transmission is known to hold reliably ... When you break that gearbox, you will face a hard choice. Finding a GWO gearbox is hard, really, and if you ever find one, it WILL break again. So you can chose to keep chasing good gearbox, or spend $3000+ in a transmission upgrade. I'd rather go Z33 gearbox instead of Z32 though... the problem with Z32 gearbox is that they are good, but only when new, which they arent now. And the gear ratio is painly long. Every Z32 transmission swap i have seen felt sluggish, even with 400+ HP at the wheels.

I have seen a SR20DET with a Z33 GB and boy was it much better in every way ! I think it will be my next upgrade. My GB is starting to make some noises i dont like, and i had to use 2 "good gearboxes" plus my previous one to make one that does not leak too much, has good gears and good shafts. It was rebuild less than 15.000 miles ago ...

Anyway since you are rebuilding, throw at least some new pistons. 400+ WHP i would put new rods too, but that is down to personnal preference and the peace of mind level you want. I like peace of mind. I do think rods upgrade is worth it at that power level, if you want reliability. That and if you ever need to change them later, it will cost quite more to do it than doing it now (labor, gasket set, bolts...). The problem is of course that it costs money now, and if you plan to sell the car sometime, you will hardly get your money back on them. So no definite answer here.

[Mikester]

400+ hp build... motor still disassembled.

Simple choice in IMHO... New pistons & rods will be worth it; whether it be OEM or 'upgrades'.

As far as :"weakness" of SR internals- Like Ray said, most JDM engines are beat on for eons before we get a hold of them.

Ultimately, on a fresh, good-quality rebuild; the absolute KEY FACTOR is the tune.

[VNG704]

Cheap? Arp rod bolts on the stock rods.

[600supersport]

thanks guys. all great info. I'm definitely gonna do pistons, but I guess I just need to justify another $350 for rods for the "might as well machine" lol.

I've priced the z32 trans swap around $1300 and I'd love a dsg which should cost a fortune, what's your guess on the z33? I'm not liking sluggish feel take

[PoorMans180SX]

I'd run stock SR rods with ARP bolts and get some forged pistons. I doubt any of the China H-beams are much stronger than stock, SR rods are beefy. If you're worried send them out to get WPC treated or shotpeened and call it a day. H-beams are probably a good bit lighter though.

[Mikester]

For a 350+hp setup, he can get the Wiseco/Eagle SR combo set for 600-700 out the door. Also comes w/ARP rod bolts.

[600supersport]

compelling argument for the stock rods...cheapest I've found those rods/pistons is $800, u have a suggestion the the cheaper price mikester?

[Croustibat]

thanks guys. all great info. I'm definitely gonna do pistons, but I guess I just need to justify another $350 for rods for the "might as well machine" lol.

I've priced the z32 trans swap around $1300 and I'd love a dsg which should cost a fortune, what's your guess on the z33? I'm not liking sluggish feel take

In any case, nissan small casing gearboxes suffers from many flaws. Bigger casing like the Z32 are less prone to destroying the gears but they eat synchros, so you are likely going to change them before using one.

I found these. It looks like the Z32 and SR20 ratios are quite similar... i dont know why it felt sluggish. Maybe this data is wrong.

Z32 gear ratios:
1st: 3.214
2nd: 1.925
3rd: 1.302
4th: 1.000
5th: 0.752

SR20 :
1st - 3.321
2nd - 1.902
3rd - 1.308
4th - 1.0
5th - .838

Z33:
gear 1: 3.794:1
gear 2: 2.324:1
gear 3: 1.624:1
gear 4: 1.271:1
gear 5: 1.000:0
gear 6: 0.794:1

$1300 including box, adapter and propshaft is cheap, but you surely need to add some rebuild labor and parts on it (synchros, bearings, clutch).

I am talking about the Z33 6spd, we have a local tuner here who makes full kit containing a custom adapter plate, custom propshaft, brand new gearbox from nissan and the required machining on it. I think it was around 3500€, but you wont come to France to get your transmission :D

This is one hell of a deal though, the gearbox alone is worth that price when bought directly from nissan.

Anyway i did not try that one, but i know the owner. He says gear changes are very fast, gears ratio is also closer (the 5th speed being a 1:1).
The box is super smooth, locks well, has a very good feeling and so on ... not so much surprising considering it is brand new. The guy is a pro drifter, he used to kill 1 to 2 boxes per season before. So far he has not been complaining so my guess is it is going to hold, even if he is getting more and more power through it :D

[Mikester]

compelling argument for the stock rods...cheapest I've found those rods/pistons is $800, u have a suggestion the the cheaper price mikester?

I found them on Ebay for like $650-something last year... right now the cheapest set I see is $756- still not that bad of a deal. Pretty sure you wouldn't be paying THAT much less for OEM once you add everything else up.

[fliprayzin240sx]

Why do people like Z33 transmission when people blow them on stock VQ setups?

[600supersport]

maybe the S14 SR stock rods would be worth sticking with for strength, the S13 ones i have will probably be worth swapping since nissan thought adding 100 grams was a good idea...

"JDM N14

Crankshaft: 12200-54C05 / weight - 37.71007 lbs.
*Connecting Rod: 12100-54C01 / weight - 710 grams or 1.56528 lbs.
Piston with pin: A2010-54C00 / weight - 480 grams or 1.05822 lbs. (real world weight measurement of 505 grams provided by @Kyle)
(A) Piston with pin: A2010-75F60 / weight - 430 grams or 0.947988 lbs.
Bearings con. rod (set):
Ring set - Piston:


JDM U13

Crankshaft: 12200-60J10 / weight - 37.919509 lbs.
*Connecting Rod: 12100-79E00 / weight - 612 grams or 1.34923 lbs.
Piston with pin: A2010-75F60 / weight - 430 grams or 0.947988 lbs.
(A) Piston with pin: A2010-54C00 / weight - 480 grams or 1.05822 lbs.
Bearings con. rod (set):
Ring set - Piston:"

[jr_ss]

The Z32 trans is almost identical as he pointed out in a later post. I never felt like my car was sluggish at 360whp with that box. No different than my SR trans anyway.

[PoorMans180SX]

Why do people like Z33 transmission when people blow them on stock VQ setups?

You must be confused? The revised (later than 03) transmissions are bulletproof.

[Croustibat]

Why do people like Z33 transmission when people blow them on stock VQ setups?

Because they dont blow anymore.

[600supersport]

im doubting it, but do you guys remember if the Z32/Z33 trans felt much heavier than the SR?

[Mikester]

Wondering what this has to do with pistons & rods?

[600supersport]

without knowing the exact reason for the rod redesign by nissan from S13 to S14 SR, im guessing the S14's beefier rod is stronger and the one id feel more comfortable pushing to the higher 400whp mark. Im going with CP/Manley since i have the S13 SR and im assuming those are the stock rods that the haters have had problems with.

[whitey240]

Do the Xterra 4.86 ring mod to the diff and that sluggishness you speak of will disappear

[maverickmotorsports]

The Z33 boxes typically don't blow up. The early models had issues with syncros which caused a lot of them to be warrantied or replaced. The later CD009(06+) boxes got the best syncros and it's pretty much stayed the same since.

We've seen 900+ whp cars with 6 speed make 100+ passes on slicks. Typically the diff is the weak point once you get to those levels. For most people out there pushing 350+ whp on the SR the Z33 box is a perfect setup. Gearing, strength, shifting, and the ability to use your current clutch is unbeatable for the price.

Shoot me a PM if you want more info on this. We've been making the adapters for a long time now and have sold a ton all over the world. Ours are the original full face adapters and the first on the market. KA now available too! [/shameless plug]


EDIT: On the topic of pistons/rods. Our test car is running a GTX3076 and pushed 550whp to the wheels. It has been chewing up bottom ends but it has always been rod bearings. We've had stock blocks, built blocks, and more recently it will be getting 11:1 setup.

My recommendation would be that whatever you do, get the 19mm rod bearing upgrade. With good tuning and E85 you won't be melting pistons as easy and the stock rods are pretty stout. The weak point in the SR is the 17mm rod bearing. Get it machined for 19mm or GTIR and party on.

[PoorMans180SX]

What rod bearing clearance are you running George?

[Kingtal0n]

EDIT: On the topic of pistons/rods. Our test car is running a GTX3076 and pushed 550whp to the wheels. It has been chewing up bottom ends but it has always been rod bearings. We've had stock blocks, built blocks, and more recently it will be getting 11:1 setup.


I think its because you are running too much ignition timing. I've tuned quite a few SR20s and in my early days, I too thought that 14* was okay. It is not okay. The mid-top end of 400-500 horsepower sr20det engines requires around 9* BTDC of ignition timing when using 93 octane fuel. That might fix your rod bearing issues, it did for me.
Idk about ethanol timing numbers; but the same rule applies. light it off too early and you hammer the rod bearing as the leverage arm attempts to squeeze through TDC with a flame building.

I find the oem pistons to be the weak link. A common issue on redtops is cylinder #2 ringland.

[600supersport]

what timing would u suggest in general in the 4-500 range on a 100 octane tune (mainly so I can see what my tuner has set)?

it seems the rod bearing and pistons may be the weaker links, granted the tune is good. Maybe I'll look for some s14 or GTiR rods...

[Kingtal0n]

what timing would u suggest in general in the 4-500 range on a 100 octane tune (mainly so I can see what my tuner has set)?

it seems the rod bearing and pistons may be the weaker links, granted the tune is good. Maybe I'll look for some s14 or GTiR rods...

When you start increasing the octane, you need to watch your EGT to get best results. I would not go much above 10* btdc though. Depends on the RPM- as you increase RPM above 7,000 you might have as much as 11-12* btdc with 100 octane. But if the turbocharger is small and building boost as early as 3,000rpm you may have as little as 7* BTDC.

Your EGT will guide you. That and engine torque. Keep the timing out of it, and watch to make sure it does not skyrocket and melt anything. You should not be seeing anything over 1450*F on a long 4th gear run. I would like to see around 1250*F. It depends on compression ratio and turbocharger size as well as intercooling capacity and a hundred other variables.

As usual I will use a real world example of an engine I tuned. This is an S13 engine, oem bottom end, Top mount typical cookie cutter setup with some cams.

http://i9.photobucket.com/albums/a90/kingtal0n/Recent_tune/Karlfinal400hp6-23-11_zpsn2ybtuj4.jpg (http://s9.photobucket.com/user/kingtal0n/media/Recent_tune/Karlfinal400hp6-23-11_zpsn2ybtuj4.jpg.html)

Karl's car. AEM Stand Alone.
I street tune everything first, then put it on the dyno to finalize wide open throttle (safe way is to verify on-board wideband with the dyno's wideband). This engine took 9* BTDC with 93 octane and at 11.8:1 gave me a perfect 1250*F EGT and 400whp. Pulling a little fuel raised the EGT slightly and gave a little more power but I decided to leave the gas in it for safety.

Notice that was 2011. Karl is still rockin the same OEM bottom end redtop to this very moment. (2013) I havn't spoke with him recently but I should ask (2015).

[maverickmotorsports]

What rod bearing clearance are you running George?

I'll check on that. The car is my buddies car that we've been developing together. A few of the blown SR's were user created. Haha.

I think its because you are running too much ignition timing. I've tuned quite a few SR20s and in my early days, I too thought that 14* was okay. It is not okay. The mid-top end of 400-500 horsepower sr20det engines requires around 9* BTDC of ignition timing when using 93 octane fuel. That might fix your rod bearing issues, it did for me.
Idk about ethanol timing numbers; but the same rule applies. light it off too early and you hammer the rod bearing as the leverage arm attempts to squeeze through TDC with a flame building.

I find the oem pistons to be the weak link. A common issue on redtops is cylinder #2 ringland.

Possibly. It is E85 so the timing is definitely more aggressive. I don't have the tuning software on my work computer but when I get home I can bring up the numbers. I actually thought about that too. There might be too much timing around 3500-4500 where the engine is loaded up a lot.

[Croustibat]

I'd take kingtal0ns anwer with a pinch of salt. He recently told to someone who he sold a car that overheating is normal when driving an SR20DET at more than 65mph. Because these are old engines.
And that he should "disconnect the turbine" to lower temps (he later admitted that "disconnecting the turbine" meant disconnecting the wastegate actuator arm from the flapper). His buyer ended up upgrading the radiator, and problem was solved ...

compared to pump hi octane gas, e85 roughly needs 4 to 8 more ° when VE is maximum, up to 10° before, and up to 18° at WOT, depending if the car was mapped safely or at the verge of det.

The funny thing is the EGT drop when using e85. I can get up to 800°C cruising (ok, like 100mph cruising on a hot day, for more than an hour, after a trackday) ... but if i go WOT and hit 160, it goes down to in the 650-700 range. So much for colder plugs ...