sc3boost

i read all i can about the 1jz and the 1.5jz, but i need to undestand something.

common sence will tell me that you need to do some changes to the engine management if you add an additional .5L to an engine (correct me if i'm wrong).

what do the guys running the 1.5 do, just add more fuel pressure or something.

and i heard that 7500rpm on a 1jz is actually 6500rpm or something on a 2jz, will the addition of 3L bottom end change the rpm cluster?

these are just some of the things that i'm curious of

Gamer

I do not think you will find many people who have done the 1.5jz conversion in the States. Your best bet is to ask the questions over on the Australian Soarer forums as quite a few of them have actually done it over there.

http://www.lexus.australia.as/entry.htm

JZZ30TT

To my knowledge there are only 3 1.5j's in the states. One is in Maryland. He is running Standalone. But, no.. you do not need to compensate for the extra .5 liters. The stock 1j computer will work fine. Are you aware of whats needed to do the conversion? It's not as much as people think

ki_soarer

OT: but who and where in maryland?

SinisterSC

Yeah who in MD? I'd like to meet em and see the car.

sc3boost

i'm thinkig that you just need a new head gasket, once you know the proper squish of the new bottom end and the current 1j head.

i'm in the process of finding a soarer clip to do the swap, and then i'll just take my time and build up my current 2jzge bottom end, i'm in no hurry.

and is the person with the 1.5 on this forum???

got_trd

It shouldnt be any different than putting a b20 block on a b16 head for example. The rpm and all that will still be the same...

sc3boost

ok that sounds simple enough, so you just swap the bottom end and leave it alone.

the ecu will work everything out, i thought it might be a little more challanging than that.

Bean

iTrader: (1)

No.
They run the same compression ratio.
They have the same pistons.
They have the same rods.
Find the logical conclusion

You'll need the 2jz timing belt (cam gears are interchangeable on both motors)

I think you don't understand what an ECU does.
It calculates how much fuel you need for a given amount of air. The air volume changes yes, but the ECU can still measure that volume of air and still inject enough fuel. You'd still be using whatever air-sensor that the car was already using (whether it being a stock 1jz map sensor, or something else like an aftermarket 3bar or a MAF sensor)... so the measurement SCALE will not change... it will be reading more air, but the ECU will already know what to do with it...
It also adjusts timing, which won't change.

Understand?

Things like displacement don't have to be custom tuned... things like cam changes, head ports, injector changes, etc DO

sc3boost

i got it, makes alot more sence now, thanks

you should be a teacher

JZZ30TT

He drives a mk3 supra, he's on supra forums.. Althought I don't think he's a very popular guy on there right now. Anyways, my roomate helped tune his car, nice guy.

Bean

iTrader: (1)

Oh lord, I'd seriously mess some peoples' heads up

SimonR

I'm in the process of converting to a 1.5jz and am installing 800cc injectors at the same time. The Emanage is currently set to cut back fuel by approx 16% after a previous upgrade from 380s to 440s on the 1jz engine.

The new engine will be a 3 litre rather than 2.5. I'll need to cut back the fuel to allow for the 800s. I'm currently thinking that an overall fuel reduction of 45% (as a starting point) will allow for the move from 440s to 800s.

However, I will be keeping the original ECU from the 1jz (which was set up for a 2.5 engine) and your post has made me wonder if my thoughts on fuelling are correct. Can you comment please?

sc300tt

I think Bean had a brain fart. Unless you are using a MAF, any change in engine displacement will affect the fuel settings since it is computing the air ingested from the manifold pressure and an X factor specific to each size/type engine.

As far as your setup, I don't know how well the stock ECU is going to be able to control such a LARGE jump in injector size (from 330 to 800). Your idle/startup is probably going to suck.

SimonR

Yes, that's the point. With a 3 litre engine and 800 injectors, will I be:

1/ Cutting back the fueling by 45% (approx) on the basis that I have 3 litres which would normally use 440 injectors (in the 2jz) or;

2/ Cutting back the fueling by 52.5% (approx) on the basis that I am still running the 1jz ECU and that it will automatically cater for the additional airflow (as I understand Bean to be suggesting).

The latter would be a problem as I believe that the Emanage can only cut fuel by a maximum of 50%.