boost gauge

My new SR5 is lots of firsts for me. First Toyota, first 4WD, first vehicle I can talk to, first auto. trans. since 1980, and first turbo. One of the half-gazillion screens I can choose is the "iForce" gauge. It shows amount of boost. Is this just a relative thing, none to max, or are there units of measurement involved?

 

I’m pretty sure it’s a PSI gauge last time I looked, so it’s not totally bs

 

It is a PSI gauge in U.S. (not sure what units it uses for metric). I got tired of it after a week and put something useful on that screen (oil pressure, oil and trans temperatures).

 

My truck shows units of measurement as psi with a maximum on the scale of 15 psi. 15 psi is equivalent to one atmosphere of pressure at standard temperature and pressure. Look up what that means if you aren't already familiar with the term.

I don't know why your display doesn't have the units of measurement visible. It may have a different scale than mine, as well as no units.

 

2025 no units on boost gauge.

 

Interesting. I would suspect the 2025 is a "non-dimensional" range of 0 to 100% range of deliverable boost pressure.

 

0 to 100% is about the only thing us users need to know, I guess.

I'm personally impressed that the truck can safely use two atmospheres of air pressure, effectively creating a 4.8 liter inline 4 engine.

Most of the time, it's a frugal 2.4 liter engine.
j.

 

Id briefly had a subaru with 2.0 bar and it was interesting, if you held the throttle and rpm at specific positions you'd see 1.8-2.1 bar.

The tacoma really doesnt like to give full boost at lower speeds. I'd like to drive one that let full pressure go in 1st gear.

 

Low RPM and high throttle (fuel and air) causes knocking, especially when hot. Knock sensors should cut fuel and boost to protect, but why trust knock sensors? I personally only use full throttle at higher RPM. That's just me though. YMMV
j.

 

My screen is usually on the mpg option. I have no idea what the theoretical max mileage is for this vehicle, given a flat road, no headwind, and the optimum speed, but I'm approaching it asymptotically because the changes are tenths of a mpg. On my regular weekly 145-mile trip, I pass the highest point in Michigan's lower peninsula while transiting from one lowest point (Lake Michigan level) to another (Lake Huron level, which is the same as Lake M.). OK, it's not exactly Rocky Mountain elevation changes, but the truck does have to gain altitude and then lose it again. No matter how light the foot, I can lose a tenth on the net uphill and gain it back on the net downhill.

As an old guy, I find myself driving like my Dad now. If there is an afterlife, he's looking on with considerable amusement at that development. But on occasion,like when some #$*&!!! is driving 45 on the state highway and the 3 cars behind are too timid to pass, I will ask the vehicle to make noise and hustle. The 4-cyl., naturally aspirated Ranger can pass 3 or 4 when necessary, by selecting the right downshift. And when I'm in the mood for feeling the seatback pressing, the Mustang GT is in the garage.

On the new Tacoma, I'm mostly chasing that elusive extra tenth of a mpg. I had to go to VT to buy it and drove back via NY and Canada. In Canada, there must be a law that evry driver has to get on the 401 at least once a day. And they're all going north of 80 mph. I started off being a polite American and staying within 5 mph of the limit but pretty soon I was just trying to stay under 90. Even then, the gas mileage was shockingly good. Drive a V-8 at those speeds and you are visiting the gas pump often.

 

Getting the engine into a band where it won't experience low speed pre-ignition is a solid habit to be in. LSPI happens at low speeds and high loads. LSPI is how you break ring lands. Don't lug your engine!

Note: this really only applies to folks with manuals. Between the fluid-coupling behavior from the torque converter and the fact that the transmission will kick down when you toe in enough throttle that this would become an issue, folks with automatics shouldn't really run across this.

 

Toyota also adjusted the MT tune to encourage downshifting. It makes peak torque 1000RPM higher than the MT T24A-FTS.

Everyone should be running 91 for the knock protection, but the MT guys really need to not lug their shit lol.

Thankfully we have port injection with our DI setup. So the valves get a nice little bath (also why Top Tier fuel is important) which also reduces carbon deposits on the piston which reduces LSPI and super knock event frequency.

 

I was pretty disappointed mine only shows the pressure as a blue bar and not PSI after watching several Tacoma videos showing the PSI. My previous car had the PSI boost gauge and it’s nice to see an actual value reading instead of a blue bar with no data. Can’t understand why no PSI on the Sport model. Also the MAX gauge has the same blue bar with no data readout. Also with not much pedal while going up hill it seems the gauge will max out even at low 2k RPM. Is this full 15 PSI??

 

You have discovered the upside to combining a tiny twin scroll turbo and undersquare engine.

Small turbo spools fast, large exhaust volume thanks to long stroke makes it spool even faster. Retard the timing just enough to not knock to death on 87 (don't run 87 btw) and you've basically got a faux diesel in gasser form and lots of low end torque.

 

Sorry if I’m uneducated, what’s an “undersquare” engine?

 

I know what "oversquare" is: bore longer than stroke, so I assume undersquare is a long-stroke engine.

 

The T24A-FTS is an undersquare engine because the distance the piston travels is longer than the diameter of the cylinder bore:




87.5mm (bore) to a 99.5mm (stroke)

This is part of why the engine doesn't rev very high, since the longer the stroke the higher the piston speed at higher RPMs compared to a shorter stroke engine.

That's fine though because with the tiny twin scroll turbo and long stroke setup it makes a lot of low end torque.

 

Thank you for the explanation and the diagrams. My previous was an 86mmx86mm bore/stroke. New rabbit whole of learning to go by. Hope I didn’t hijack the thread.

Has anyone seen the aftermarket boost gauge that replaces the JBL pillar speaker? I saw a photo and now can’t find it.

Is it as easy to tap a vacuum line to get the turbo readout on an aftermarket gauge? This would be something I want 110%!

 

FA20? GR86 or something with a K20 or 2JZ?

My Scan Gauge can report boost pressure, the Banks iGauge can be pillar mounted, can also report boost pressure.

 

J30AC