Big BORE throttle body - Maxbore

Hey TW,

Just sharing the info love today. I searched high and low for big bore tb info and I mostly came up with the URD adapter plate and using a 4Runner (70mm) or Tundra TB (75mm). There is a lot of mixed info mainly pertaining to the gains for a forced induction 4.0l. Also, it seems that the URD adapter plate is not necessarily matched to the intake requiring port matching to the intake which some one complained about. Additionally, if you want to use the factory intake like I did, the adapter creates a fitment issue since it move the TB out by an inch or so plus I’d think the larger inlet of a 4Runner or Tundra may pose an issue fitting the stock hose to the air box. One thing is for sure no one is claiming any big power gains from a larger TB. I didn’t dyno it so I’m not going there. I did it because I was interested in a pedal commander for improved throttle response but after reading some issues with the pedal commander working/not working or being inconsistent over time, I decided I still wanted better throttle response but I would go w the big bore TB to do it.

I sent a TB in to George at Maxbore in Fl. He said he commonly bores TBs about 3mm out with a machine taper on the inlet. He will also shave down the shaft and put in a new butterfly. So while the bore is only 3mm over stock, you gain a little more air volume w a shaved down shaft. It may all be insignificant but those are the details. The cost is $185 + shipping to Maxbore. That includes return shipping costs.

The install:
It was super easy and took about 40 mins from start to finish. If you’ve ever removed the stock intake you know how easy it is to get to the TB. It is completely plug and play. Everything fits and reassembles as it should and it’s stealth.

After the install, it wanted to idle at 1,500 or so RPMs. I did a battery disconnect for 10 minutes and it was all good after that. No CEL or strange idling and no need to mess with the idle screw. Throttle response has been increased and it pulls smooth all the way through the power band. These motor redline so low, it seems like the redline should be in the upper 5k instead of the lower 5k or so where it shifts.


Here is what I measured.
Stock inlet 71mm exit is just over 65mm
Bored inlet 73mm exit is 68mm
Stock intake manifold is 68mm

What good is a thread without photos? Here it is...

 

i used this company for years for my race cars. never thought about doing it for my tacoma. wonder if there would be performance gains for AllMotor setups. intake headers bored TB and exhaust

 

Nice write up. Just to confirm, you're currently only running a pedal commander, the Tundra throttle body, and the URD adapter on a non-supercharged Tacoma? I’m non-supercharged, no pedal commander.

 

This is common type of modification on racing engines where the engine ports, intake manifold to cylinder head, headers to cylinder head, etc. are "matched" to each other by grinding away metal so there are no obstructions to upset the flow and cause turbulence. Even gaskets were trimmed. The ports were them polished as smooth as possible to reduce turbulence even further. Commonly known as "porting & polishing".
It makes a difference on a 500hp racing engine where you're looking for hundredths of a second in the quarter mile. On a regular engine, performance gains would be minimal, if any and the procedure is a lot of dirty work.

 

This is just an OEM bored out throttle body on a naturally aspirated 4.0l- nothing else.

 

Due to an unfortunate accident on (12/21/23), all Maxbore business is on hold until further notice.

• Packages will be returned to sender.

I hope and pray my uncle George will make a full recovery.