12H-T power boost

[Tim-HJ61]

Hello,

Warning: modifying the settings for your turbo boost and injection pump can cause an adrenalin rush: so I did it! Touch any of these settings at your own risk.


After enjoying the extra torque of the fat exhaust, I set about increasing the boost and fuel to get more performance. Some had suggested my 12H-T was a bit of a slug.


First. Boost.
Ages ago I had installed a simple bleed boost controller purchased from ebay. Standard boost is 7psi. I have been running at 12.5psi for a year or so. My advisors suggested 16 psi or more. I've settled on 15psi as it is what my gauge measures and also it matches the overboost warning light provided by Toyota.







Second, measurement.
Instal a quality EGT, Exhaust Gas Temperature, Gauge or Pyrometer I could tell what EGT I was running. EGT is affected by load, fuel, boost and is an excellent indicator of the stress on the engine. I back off the throttle when the EGT reach 600°C, my advisors say I could go higher. I'm nervous about pushing it too much.








Third, more fuel.
The little screw that holds the key to more power.
Required 2x 10mm spanners, and 1 x 3mm allen key.
As shown in the photo, undo the cap cover off fitting marked in yellow paint. The outer most is a cap. the inner nut is a lock nut. Under the cap is a long screw into which fits an Allen Key. Mark your start point, undo the lock nut, unscrew the long fuel screw half a turn, tighten the lock nut and test. Keep doing this until you get the solution you are seeking. Caution needs to be exercised and this adjustment should not be done by the faint hearted or those wanting iron clad guarantees of consequences. Things may break.....









Outcome.
I unwound the fuel screw two full turns and have been amazed at the power increase. I now get full boost at 1800 rpm where it used to be around 2000rpm. The engine is very keen and willing in the higher rev range and spins easily to the orange line of 3500 rpm. Acceleration from 80kmh to 110kmh in 4th or 5th gear is brisk.



Downside is the ease of too high EGT.



Solution, add more air ie increase boost. As a test, I ran without the waste gate actuator connected and found the turbo spun to about 22psi and EGT's did not rise as much as before. Even at full power climbing a hill at 110kmh EGT dropped from 600°C to 500°C in the same circumstances. This was far more acceptable with regards EGT, but driving without waste gate connected is just too risky for my liking. The orange warning light was flashing on when I accelerate hard and can become annoying and ignored rather than a valuable tool. Boost is now comfortable at 15psi maximum and EGT only rise to danger levels when I push hard at 15psi, essentially creating an overfuelling leading to high EGT.


Fuel consumption has not changed to any noticeable extent. I recently completed 3000km on vege oil with the high power settings and got 12.5l/100km.



EGT was the most expensive component. Boost controller about $30 from ebay, fuel screw adjustment is free! All these mods are interdependent with the exhaust upgrade.


Hope this helps someone looking to play with their 12H-T.



Tim