I want to tune my ALL MOTOR 2000 Lexus GS 400. I want to know what handheld tuning device will be good for my Lexus. I’m super new to this. (1UZ 4.0 V8)

 

There's really no plug in tuner that will do anything. The best way is to install a piggyback or stand alone ECU. That's the only way a tuner could make changes to a/f ratios etc. The cheapest way for a good tuner is an AFC-Neo. Or a used SAFC-II. These wire in and piggyback off the ECU and allow for tuning.

What do you have done to your 1UZ? Full bolts on's doesn't really even warrant tuning. An all engine build usually consists of heads and cams work, along with intake and exhaust. That would be a big enough change to need some a/f adjustments. Intake and exhaust mods alone are within the factory ECU's ability to correct for.

 

All that is done to my 1UZ is a cat back straight pipe. What do you mean “Piggy back off the ecu” how would I be able to do that?

 

Step 1: determine what your goal is

Step 2: determine what your budget is

Step 3: determine how you can achieve that goal

Step 4: shop for parts

 

By piggyback you are still running the car off the factory ECU but the piggyback module that plugs into the original ecu such as the Apexi will change certain parameters.

 

You wire it in. The ECU stays the same and controls everything. The piggyback unit distorts input readings, like from the MAF and throttle, to make the ECU control the fuel system with more or less fuel at desired rpms. You can install a wideband o2 and gauge and fine tune your own air/fuel ratio with the AFC-Neo or similar controller. It's too expensive and complicated for a car with just bolt ons. Your A/F ratios are fine with intake and exhaust mods. The factory ECU can adapt for minor changes to the airflow. Any amount more of air you can flow through intake and exhaust changes will be read by the MAF and the ECU will command fuel to inject accordingly. The o2s will keep the ratio "stoich". A tuner device allows you to force a change though if you want to lean out a little from the factory settings and pick up a few ponies. Like I said, not worth the effort.

 

Actually, an Apexi NEO works quite well and it absolutely holds the tune, unlike what some may claim. I have a detailed install video and street tune video on my YouTube channel. Just search “gs400 forward_momentum” on YT and my channel will come up. The GS loves fuel in the midrange, but how much to add is where tuning comes in. Expect gains in the 15-25 whp range and up to 40 TQ, depending on mods.

 

Quote:

Expect gains in the 15-25 whp range and up to 40 TQ

I'd like to see a dyno chart of that. That would be excellent value if true.

I was a little confused by your street tune video because you mentioned it was running rich, and were aiming for a leaner AFR, but later on say you are adding fuel. A dyno plot with an AFR plot to match would be decisive.

 

There’s an old thread here in CL that has dyno charts. I cannot recall if it was rock-a-lex or not. I think it may have been. I still have a hard time with the +40 TQ. That’s just insane.

On my vid I was discovering that my engine seems to like the 12.5-12.7 AFR mark. My comments may have been related to “out loud thinking” and the tweaking of the AFRs on the fly. I can absolutely feel the midrange gains. It is a huge increase when passing and the VVTi switchover, while cool, has been smoothed out.

I plan to dyno tune when it gets warm. For the record, I do not think I gained 25whp and 40tq. I don’t have some of the mods these other guys had (such as headers). But the tune worked and held. I think that is a potential max power gain with various mods and the right tune.

Thanks for your comments.