1jz questions

[nalchlan]

gday to the 1jz people
Are there many differences between jza70-jzx90 1jz's for the engine's mechanical? (head, bottom end etc)
does anyone have an r154 clutch fork they wish to sell me?
I'm going to put a single on, but funds limit me to a stock ecu and injectors. What turbo should i run?
opinions please: i have a china t4 exh mani. my goal is to run standalone and bigger injectors. I just want the car running driving.

[bk_]

gday to the 1jz people
Are there many differences between jza70-jzx90 1jz's for the engine's mechanical? (head, bottom end etc)

JZX90 uses 4-row ECU plug, JZA70 uses 2-row ECU plug.
JZX90 is front sump, JZA70 is mid/rear sump.
Turbo outlet is 90 degrees on JZX90, JZA70 is 45'ish degrees.
Older JZA70 engines have issues with cam breather hose design/location.

The main thing is if the engine hasn't been abused with budget mods (boost cut removed, OEM ECU, stock turbo dumps, running 15psi+ and hitting 6000 RPM).

I'm going to put a single on, but funds limit me to a stock ecu and injectors. What turbo should i run?

I run stock twin turbos & stock injectors with an aftermarket ECU. I've seen a HUGE difference between OEM ECU vs a properly tuned setup, with nothing else changed in between (FMIC & custom dumps & 3-inch exhaust stayed the same)

re: choosing a turbo... I'd run a borg warner EFR twinscroll.

opinions please: i have a china t4 exh mani. my goal is to run standalone and bigger injectors. I just want the car running driving.

Avoid cheap manifolds. You will regret it a few years down the track.

[nalchlan]

Thanks mate, and as far as you know the bottom end are the same? I've got all the parts of a jzx90 1jz , but the cranks shagged, and i have a jza70 long motor.
I no longer have the twins, but how high do you run your boost?
unfortunately a borg warner would send me broke, im thinking kinugawa td06h-25g kind of money ~1 grand

[bk_]

I dont know if they're the same or different, I just know some people destroy them without explanation

I've had my JZX81-based engine for the last 8 years. still going strong.

I run 11psi boost, although it did run 10% (1.4 AFR) too lean after replacing old spark plugs and other various changes (changing end-of-injection timing, and conversion to full sequential injection). I run closeloop wbo2 so it self-learns towards target AFR anyway.

With stock injectors, I'm limited to 14-15psi otherwise I'll exceed maximum injector duty cycle after 5500 RPM (injector duty cycle is pretty much constant after 5500 RPM, atleast for stock cams/stock twins).

Running OEM ECU on single aftermarket turbo, the tune requirements is so different, you have to be crazy to do so.

The OEM ECU is just a 6502-like 8-bit microcontroller running at 12mhz. A souped up commodore 64 if you wish

[midnight_purple_GA70]

there is nothing wrong with running a single turbo on an aftermarket turbo.
providing you do the following.

dont run a ridiculously sized turbo
have an safc or similar to add or reduce fuelling.

have done that on a 2jzgte auto in a jza80 supra with gt35r and an auto... makes a bit over 400rwhp and has gone 11.2 @ 123mph
has run reliably like this for over 4 years...
also on an ebay spec chinese manifold...

same principles can be done on a 1jz.

sure there are gains on aftermarket computers and its about to get one with bigger injectors etc to go into the 10s but it can be done.

make sure if you are doing it that you use a 10psi spring in the wastegate as a maximum
if you are not going to put an safc on it then at least get the afrs checked on a dyno.

now when it comes to a turbo cheap shitty little turbos are a waste of space.
you may as well put the stock turbos on instead for $250 for a full set in working order.

otherwise look for a 2nd hand gt30 or gt35

i could supply a reasonable priced new version of the above but you would need to be spending around $1500

also dont skip on a wastegate buy a proper tial or turbosmart etc

[nalchlan]

Thank you both. BK: i found part numbers for the head on JZA70 and JZX90 are the same.so that answers my own question. Im assuming you meant to say you ran at 100% of your injectors duty cycle with an AFR of 1.4? How, what is a closeloop wbo2...a wideband oxygen sensor? what does this do? adjust the amount of fuel injected dependant on the amount of oxygen present in the exhaust so as to maintain the correct/desired AFR?
As far as running an aftermarket single on the factory ECU, im not trying to tune it for power, i just want the car running. It wont know the twins have been replaced by a single. After i can save, i will then install a standalone, bigger injectors and a bigger fuel pump, then get a tune. Also, Im pretty sure the ECU in my VS commodore was a 64-bit!

midnight_purple_GA70: I don't want a ridiculous turbo, but i also want to make some numbers around 300kw with the appropriate fueling and ECU to match.
I do have an SAFC but it looks to be the older, square shaped version, by APEXi. I also have 2JZ injectors, so its possible to go down this path as well. It is hard to find solid advice on using these injectors for the 1JZ-GTE, some say you need to run resistors, some say they bolt straight in no worries, others say they bolt in, just need a tune.
As far as using the twins, they are long sold, and i specifically want a single.
China turbo's often last a long time, and are good on a budget. This time next year i may want to go bigger, so i doubt it will be on for very long... funds permitting.
I just cant decide on the size of the turbo to use. I've been told a ct26, a td06-25g are a good idea. I already found that the VVti single manifold does not fit the non VVti

Cheers for your time!

[bk_]

Thank you both. BK: i found part numbers for the head on JZA70 and JZX90 are the same.so that answers my own question. Im assuming you meant to say you ran at 100% of your injectors duty cycle with an AFR of 1.4? How, what is a closeloop wbo2...a wideband oxygen sensor? what does this do? adjust the amount of fuel injected dependant on the amount of oxygen present in the exhaust so as to maintain the correct/desired AFR?

I mean a difference of 1.4 AFR (10% fuel). So if it was originally tuned to 12.0-12.4, it was actually doing 13.6... I did have it originally tuned on the dyno when I knew _nothing_ about tuning, but that was years ago. Altering a few things (EoI timing, conversion to sequential, replacing old spark plugs) made such a big difference. But anyway... that's why you need to be careful, even if it's been tuned and you change something on the engine, the fuel requirements will change. Make modifications to the engine running an OEM ECU, you can't trust it to provide correct fuel requirements _anywhere_.

my (unsupported) ECU supports per-cell closeloop target AFR with wideband input, so I take advantage of it.

As far as running an aftermarket single on the factory ECU, im not trying to tune it for power, i just want the car running. It wont know the twins have been replaced by a single. After i can save, i will then install a standalone, bigger injectors and a bigger fuel pump, then get a tune. Also, Im pretty sure the ECU in my VS commodore was a 64-bit!

If throttle response is not an issue, then go for it.

I had one guy (and his friends with the same engine) comment to me the tune I did for him, the engine / car feels far superior than the chipped (mines) ECU he had, even though he's running a 2jz vvti with stock injectors but with single turbo, between 11-13psi... until he can source sard 800cc injectors.

My rule of thumb based on my experience:
* if no aftermarket ECU and bad throttle response. OEM ECU is the problem.
* if aftermarket ECU and bad throttle response, something on the engine is fubar'd.

It is hard to find solid advice on using these injectors for the 1JZ-GTE, some say you need to run resistors, some say they bolt straight in no worries, others say they bolt in, just need a tune.

Only the 550cc variant (USDM? non-JDM?) you need to run resistors.

I'd say that's not enough - 650cc is the sweet spot for 1jz 2.5L, 800cc for 3.0L, for reasons of throttle response. (end-of-injection timing plays a more important part the bigger the injectors you have)