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sre30s14
09-07-2021, 03:22 AM
So I gave my car to my engine builder/tuner guy. I was hoping to just get bumped up to 300 BHP. But when he opened the motor he noticed it has 2JZ-GTE pistons in it and I thought my car was stock. So he had to tear down the whole block to see if anything was done incorrectly. So I am getting new piston rings now.

But I got thinking about making 350 to the wheels. Seeing that the pistons are great and what not. My question is, is it worth it? Is a new turbo going to make the car more enjoyable? Or will I just put around and be that guy who never goes above 4K RPM? Because I'd be seeing a thousand dollars on top of all of that sorta work. Manifold and what not.

In my head I am thinking I've done the 3 inch exhaust, the F-Con, Skyline LSD, Skyline Brakes, my intercooler has a dent in it, new piston rings, 2JZ pistons are sitting there, a beefier clutch, 500 ccs so why not just go the extra mile.

But on the other hand am I just wondering if I am being greedy for no good reason. What does 350 WHP feel like against 275 WHP or 300 WHP? I am probably gonna be running E20 so I hope that gives me a little more.

Kingtal0n
09-11-2021, 06:46 PM
What engine and how is the car used

2jz pistons are the same size as sr20 so I cant tell if you have a 4-cylinder or 6-cylinder

In general a stock sr20 can support 360rwhp to 380rwhp this is considered a minimum for me as a reliable daily driver (20 years 200,000 miles)

For 2jz-gte the minimum is simply 150% of stated or 360rwhp times 1.5 = 540rwhp

Thus your target goal is very low, and confuses me with the engine mods.
In other words, it takes NO Modifications to a stock engine besides cam/spring to make those stated numbers and ANYTHING you do or have somebody do is going to reduce the reliability of the engine.

I would be surprised if you see 10,000 miles from an engine that somebody opened up and fooled around with the bottom end / pistons/rings/etc... It generally ends poorly. Whereas if you take a perfectly stock 140,000 miles 2jz-gte and produce 550rwhp you can take that engine to 240,000 miles easily (+100,000 miles and 10 years of service) with no modifications or rebuild necessary.

sre30s14
09-12-2021, 12:24 AM
What engine and how is the car used

2jz pistons are the same size as sr20 so I cant tell if you have a 4-cylinder or 6-cylinder

In general a stock sr20 can support 360rwhp to 380rwhp this is considered a minimum for me as a reliable daily driver (20 years 200,000 miles)

For 2jz-gte the minimum is simply 150% of stated or 360rwhp times 1.5 = 540rwhp

Thus your target goal is very low, and confuses me with the engine mods.
In other words, it takes NO Modifications to a stock engine besides cam/spring to make those stated numbers and ANYTHING you do or have somebody do is going to reduce the reliability of the engine.

I would be surprised if you see 10,000 miles from an engine that somebody opened up and fooled around with the bottom end / pistons/rings/etc... It generally ends poorly. Whereas if you take a perfectly stock 140,000 miles 2jz-gte and produce 550rwhp you can take that engine to 240,000 miles easily (+100,000 miles and 10 years of service) with no modifications or rebuild necessary.

I am opting to go for 300 whp. Keeping the T28. Might do cams. It's a funny car. I bought it 8 years ago, I drive it fairly often, and I didn't have any reason to rebuild it. It's an SR20DET powered BMW E30. I know I know. Not smart.

Anyways I was getting a new headgasket so I could safely raise the boost. The engine builder found out it always had pistons from a 2JZ-GTE. It's quite miraculous it survived this long. Bearings were perfect. But I figure I should focus on getting myself some experience with the power before bumping up. I could put the extra monies into refreshing suspension components. Its a strange thing the pistons. The engine is in good shape and nothing else is modified on it. Just the pistons.

Kingtal0n
09-12-2021, 10:46 AM
yeah but the pistons are the same so it doesn't actually make any difference in hardware

the only difference is whether or not somebody opened a factory engine and disturbed parts, it can decrease reliability, dramatically

never open an engine unless you absolutely have to

sre30s14
09-13-2021, 12:46 AM
yeah but the pistons are the same so it doesn't actually make any difference in hardware

the only difference is whether or not somebody opened a factory engine and disturbed parts, it can decrease reliability, dramatically

never open an engine unless you absolutely have to

Yeah wish we didnt have to but apparently it was tampered with a decade ago so it had to come apart. It was surprisingly ok. Praying it doesnt blow up now haha

sre30s14
09-17-2021, 08:46 AM
yeah but the pistons are the same so it doesn't actually make any difference in hardware

the only difference is whether or not somebody opened a factory engine and disturbed parts, it can decrease reliability, dramatically

never open an engine unless you absolutely have to

So if I buy a new long block I can't tell if its been opened before as well. So how do you approach that dilemma?

My engine builder opened the block and found out the pistons were scored from the previous owners mistakes in their rebuild.

But say if I buy a new block how would I know if that will run fine? That it too doesn't need a rebuild?

Sorry for derailing, my thing became a mess as usual. How simple things start I guess.

Thursday7
09-17-2021, 09:38 AM
the only difference is whether or not somebody opened a factory engine and disturbed parts, it can decrease reliability, dramatically

never open an engine unless you absolutely have to

where does this logic come from? Is precise engine assembly with quality parts something you've never considered?

sre30s14
09-17-2021, 11:44 AM
where does this logic come from? Is precise engine assembly with quality parts something you've never considered?

I kinda get where he's coming from. It's sort of like respraying a car. The factory paint is the best paintjob it could ever have.

The hermetically sealed factory of Nissan back in the 90s, absolutely lint free, the perfect run in, etc etc.

If your builder even makes one little tiny mistake your motor could fail. If you fail to run it in correctly due to a lapse of judgement. The motor could fail. It's a sensitive time when a motor is being rebuilt.

Kingtal0n
09-26-2021, 02:41 PM
Exactly there are thousands not hundreds, its thousands of ways to screw up and engine build. I've never seen any rebuilt sr20 or ka24 go past 50,000 miles whereas every single factory sr20 and ka24 will easily 250,000+ Miles.

Sure, everybody knows that one rebuilt engine that did pass 50k miles. There is always 1 guy who claims this happened and maybe it did,

but when you compare that there MIGHT be 1 single rebuilt engine out there which can somehow manage to reach 50,000 miles with the fact that every single factory sr20 is guaranteed to surpass 250,000 miles (when treated properly as we've seen they all can) Its a no brainer to avoid the rebuild altogether considering the end result, and what do you get from a rebuild? If its a stock rebuild you get nothing for all that trouble. If its a slew of aftermarket parts, what this really means is heavier internals (stronger) which can support an additional maybe 100hp or 150hp over what the factory internals can (400-450bhp = Factory, 450-600bhp = aftermarket internals)

Then compare the cost of aftermarket parts plus assembly WITHOUT the risk, lets say the rebuild is 100% successful what do we have? Around $6000 invested in the build for an additional 100 to 150hp from a 4-cylinder thats lost all it's low end torque and most of the daily drivability and spool character.
NOW factor in the risk and the fact that I've never seen an aftermarket internal sr20 reach 50,000 or even 35,000 miles (Sure there is that ONE but...)

And when your done thinking of all that risk, consider that there is an engine out there called an L33 which weighs the same as the SR20DET and can support 1600bhp, around three times what an aftermarket parts fully built sr20det can acheive, and that the L33 will easily 250,000 miles just like the OEM sr20 engine. Oh and to top all that off, the L33 is roughly half the price of a stock sr20det.

Its a no brainer. Don't try to rebuild anything. Just use the correct OEM engine for the application and be done.

Kingtal0n
09-26-2021, 02:51 PM
So if I buy a new long block I can't tell if its been opened before as well. So how do you approach that dilemma?

My engine builder opened the block and found out the pistons were scored from the previous owners mistakes in their rebuild.

But say if I buy a new block how would I know if that will run fine? That it too doesn't need a rebuild?

Sorry for derailing, my thing became a mess as usual. How simple things start I guess.


It takes experience to inspect an engine. From 2005 to 2012 I inspected around 1000 imported JDM engines and installed and tuned many of them.

Some rules:
Never take the engine with modifications, always look for factory air box, OEM air filter, OEM nuts and bolts, OEM silicone color (is it white around the valve covers? iirc).
Must have factory turbo and complete factory PCV system.
Inspect the intake, compressor, and throttle valve for signs of pitting due to improper air filtration.
The engine should not appear washed (pressure washed) look for signs of being harshly sprayed (oblong or strange marks in the filth where a high pressure stream left signs)
Its OK to pressure wash the engine but YOU should be the one to do that
Look at all the plugs for signs of abuse they should all look the same and be pretty clean, but not NEW or recently replaced (look for good looking old plugs with factory heat range 6)

The rest is experience I guess, you have to be able to detect modifications and errors in the setup easily. What you want is a 100% untouched stock engine with 80k or 150k miles, those are ideal. But sadly there are none left so this is all moot....

In todays world your best effort is to find one that hasn't been apart, still has all the OEM equipment, its okay if the turbo is leaking or smoking as long as its factory, check the plugs and health of compression and stuff, make sure all the pcv is there, everything is good its just tired. Make sure its always had a paper air filter, factory air filter or similar (ONLY PAPER).
If you get the 100% factory stuff, paper filter, well maintained, smoking turbo leaking engine, 250,000 miles, it should still have clean looking oil if there was a full PCV system and PAPER air filter, that is the ideal candidate to rebuild back to stock. Hone the cylinder throw in some new rings and use the color code bearing system and its good to go with a new chain and some head refresh.


Reverse checklist (same thing but what NOT to buy or do)
Never take or try to rebuild an engine with:
1. modified PCV system
2. aftermarket air filter
3. aftermarket turbo
4. internal modifications
5. "head" work or "cam" Upgrades
6. very dark/black oil

If the PCV system or air filter is modified there is a good chance that any rebuild no matter how careful you are will fail due to debris inclusions ingestion which is undetectable by the human eye and can not be washed out by any machine shop or process we have.

IF the turbo was modified there is a chance the engine suffered some abuse due to erroneous tuning or fuel quality etc...

Any internal or head mods also lead to failed rebuilds frequently because most machine shops and individuals do NOT know enough about SR20 engines to effectively perform those mods

Very black oil and dark oil is a sign of poor maintenance and lack of suitable PCV and air filtration during operation, the black tar-like goop you see is MUCH worse in the stagnant reservoirs of JDM engines (in other words, if you can see dark oil on the dipstick or from the oil pan, it must be MUCH worse in the places you CAN'T see) And this leads to oil system issues (varied) which can not be corrected by any general means we have available and likely the reason the engine is for sale or ruined.

sre30s14
09-26-2021, 07:29 PM
Exactly there are thousands not hundreds, its thousands of ways to screw up and engine build. I've never seen any rebuilt sr20 or ka24 go past 50,000 miles whereas every single factory sr20 and ka24 will easily 250,000+ Miles.

Sure, everybody knows that one rebuilt engine that did pass 50k miles. There is always 1 guy who claims this happened and maybe it did,

but when you compare that there MIGHT be 1 single rebuilt engine out there which can somehow manage to reach 50,000 miles with the fact that every single factory sr20 is guaranteed to surpass 250,000 miles (when treated properly as we've seen they all can) Its a no brainer to avoid the rebuild altogether considering the end result, and what do you get from a rebuild? If its a stock rebuild you get nothing for all that trouble. If its a slew of aftermarket parts, what this really means is heavier internals (stronger) which can support an additional maybe 100hp or 150hp over what the factory internals can (400-450bhp = Factory, 450-600bhp = aftermarket internals)

Then compare the cost of aftermarket parts plus assembly WITHOUT the risk, lets say the rebuild is 100% successful what do we have? Around $6000 invested in the build for an additional 100 to 150hp from a 4-cylinder thats lost all it's low end torque and most of the daily drivability and spool character.
NOW factor in the risk and the fact that I've never seen an aftermarket internal sr20 reach 50,000 or even 35,000 miles (Sure there is that ONE but...)

And when your done thinking of all that risk, consider that there is an engine out there called an L33 which weighs the same as the SR20DET and can support 1600bhp, around three times what an aftermarket parts fully built sr20det can acheive, and that the L33 will easily 250,000 miles just like the OEM sr20 engine. Oh and to top all that off, the L33 is roughly half the price of a stock sr20det.

Its a no brainer. Don't try to rebuild anything. Just use the correct OEM engine for the application and be done.

According to my SR20 specialist, you need new headstuds and a new gasket to go past 300 rwhp. Should I just ignore that recommendation or is that what I should do with the new long block?

Actually hmmm I need a new thread. I mean this isn't even about the turbo anymore. This is a Rebuild vs New Motor thread. I am honestly quite unsure. My mind is being split in half.

Kingtal0n
09-28-2021, 06:44 PM
According to my SR20 specialist, you need new headstuds and a new gasket to go past 300 rwhp. Should I just ignore that recommendation or is that what I should do with the new long block?

Actually hmmm I need a new thread. I mean this isn't even about the turbo anymore. This is a Rebuild vs New Motor thread. I am honestly quite unsure. My mind is being split in half.

haha this is exactly why I don't trust anybody else to do anything to or with my car and engine.

NO You do NOT want head studs OR a strong gasket on the sr20 or 2jz engines for cast piston applications.

That is one of the quickest ways to destroy the engine especially if you are not a true professional at tuning and safety setup.

The factory gasket and factory head bolts should ALWAYS be kept when the engine is using OEM cast pistons, this goes for sr20, 2jz, and LS engines producing 1000rwhp- same deal.

Why? It may seem strange if you are new (like less then 20 years of experience I guess) to engine performance - I'll try to explain briefly, simply,

Head gasket:
The OEM pistons are very brittle. They will not tolerate shock or abuse or high temperature. Especially high temp.

When the pressure rises dramatically suddenly due to various reasons (MANY reasons, bad gas, poor tuning, high temp IAT, ignition issue, crank/cam trigger scatter, w/e) All it takes is one good shock and the piston materials crumbles into pieces and a chunk breaks off.

To HELP prevent this situation (Not completely but it will really really help) You MUST use the OEM head gasket. The OEM gasket is specifically designed to protect the OEM piston- That is, they will blow out when the pressure rises beyond the point at which the Piston might break apart, thus saving the piston(s).

There is a longer story here, about mathematics, pressure integral, shaft work, flow work, fluid mechanics and so forth.... The pressure exerted by combustion isn't a DIRAC the way it is modelled in the thermydynamics book for the sake of simplicity, it is actually an INTEGRAL of pressure over which some dynamic range of rodxstroke angle may perform work on the crankshaft... Here I have a picture
https://i.postimg.cc/7h53JgMG/engine_analyzer.png

Take long look at the picture and try to imagine the force exerted on the piston throughout some range of engine crankshaft rotation. Then imagine the difference in the rising rate of pressure due to increased temperature, or additional air mass (more boost pressure). Also consider if the engine is under load during an acceleration through different gears or with varying vehicle weight (i.e. tuned on a dyno and then you add passengers or luggage etc... more weight in the car at a later time) How this will affect the rising rate of pressure and ultimately the highest PEAK pressure.

Keep in mind there is 0lb-ft of torque being applied to the crankshaft during TOP DEAD CENTER. In other words when the piston is at TDC no matter how much pressure is exerted on the piston there is ZERO torque produced at the crankshaft (NO work done) Thus the rising rate, temperature, expansion of gas, etc... exerts a STRESS and STRAIN (deformation and pressure) even when the engine is not output any work from the cylinder, and thus all must be taken into consideration when tuning the engine in terms of spark AND setup (temperatures of the oil/air/fuel, rate of acceleration, rate of combustion expanding gas, rate of piston velocity, etc...)

What I am trying to say is, there is more than one SHAPE of the integral "curve fitting" for an infinite number of potential power output figures.
For example say an engine makes 400hp with a peak pressure of 1000psi but the pressure rapidly falls off after some crankshaft rotation.
Another engine or tune strategy or different fuel (lets say higher quality fuel) might produce the exact same power- 400hp as above- but with a REDUCED peak pressure of say 700psi, but the pressure remains for a longer duration of crankshaft rotation (more area under the curve with a lower peak pressure) thus we can have the SAME work output (400hp) with two completely different peak pressures which of course means one engine will experience more stress, more deformation, more easy to break a brittle fracture of some materials, but they both can produce the same exact power.


Next, Head studs, now there is a real issue with head studs.
First of all You MUST Machine the engine using a deck plate with head studs. The engine must be completely dissembled and you can rent a deck plate from mazworx and put in the head studs, bolt everything down and machine it that way. This must be done because the clamping force of head studs will DEFORM the cylinders differently than head bolts, thus the machining is necessary. Same thing with main studs- you bolt down the main caps with the main studs but without the crankshaft and LINE BORE the engine at a machine shop to use those studs, otherwise the bearing will not be round just like the cylinders won't be round if you skip this step.

Now- using the head studs in the first place is NOT desirable unless the engine is going to experience a LOT of pressure peak for some reason, and this means you are also using forged alloy pistons (aftermarket pistons can withstand more abuse and pressure without breaking). And since the OEM pistons are good to approx 450rwhp sometimes 500rwhp I would sufficiently to say that Head studs are really only useful for engines producing beyond 500rwhp and even then its a toss up, I would rather keep the OEM gasket and OEM bolts because it will force the tuner to err on the side of safety and low pressure peaks, and to seek power gains from lengthening the pressure INTEGRAL rather than by increasing the primary peak pressure. This can be done several ways but the ideal and simplest methods are Reducing IAT, water injection to cool the cylinder, and increasing fuel quality.