I recently tuned ITBs for the first time on a factory GM PCM. Truck was dyno tuned before I was called in. Loads of driveability issues on the dyno tune. Lacked throttle response, it bogged, spit, sputtered, had trouble idling among other issues. Drives like an injected LS should now. Had to synchronize the ITBs, then got the IAC working, then had to adjust the Alpha N TPS multiplier table under 1,600 rpm and add the fuel back that the prior tuner had removed because he decide not to use Alpha N to reduce the idle fuel. I just thought I would share because they are not commonly used on V8s outside of Richard Holdeners testing and Holdens in NewZealand and Austrailia. Then not many tune them without using some kind of standalone ECM. This one has a P01 0411 PCM using a HP Tuners 1-bar Speed Density custom operating system that allows for the TPS to be used as a multiplier of the VE table. I was able to lower the idle after sorting the IAC to where it idles 900 rpm in Park and 750 rpm in Drive and will sit there with the AC on without bogging down or causing drivability issues No stalling coming to a stop. Fires up cold like a stock LS with or without the AC on, idles at 1,200 rpm right after it fires, then idles down normally as the engine warms up. Cammed 6.0L for what it is worth and it has a pretty good sized cam in it. Idles far smoother with ITBs than it would with a shared plenum and single throttle body. I have tuned the same cam with a truck intake and a car intake they definitely ran lumpier. Intake duration is low 230s exhaust is upper 230s, it has a 112 LSA and 0.600 lift.

https://youtu.be/BYo-EHgxapY?si=fNp3gK42XWHuSec0

 

At first I was like WTF is ITBs. Then I watched the video. Oh OK now I understand. Pretty cool.

 

The mere fact that people do not realize what an ITB is by the acronym somewhat proves my point. Just not commonly seen or used. I agree they are very cool. Compared to the same sized cam with a shared plenum this one runs so smoothly as well. That was my biggest surprise of the whole thing. Also extremely snappy with minimal throttle movement. That 5,500 rpm snap was a quick little jab at less than 1/2 opening.

The intake manifold vacuum is minimal and the valley pan is used as a sort of reservoir for the brake booster, IAC and MAP sensor. With the lack of vacuum under the throttle blades during the overlap period there is a lack of vacuum pulling exhaust gases into the shared plenum. Makes the same cam act like it has much less overlap.

The truck accelerates like crazy too. The biggest issue is filtration. The trumpet stacks have tiny round K&N filters in them for street use. At the track one would be removing those filters and running open trumpets or else lose a ton of power.

 

They install the ITBs often on the other side of the Pacific ocean.

This one has a 236/242 @ 0.050 cam in it. 306KW is 410HP.

 

I watch Holdner's videos too. I just thought ITBs was some tuning parameter I don't know about yet. Individual Throttle Bodies. We used to run individual carbs on our little 4 cylinder mini trucks back in the day.

I guess it cuts down on intake tract reversion and A/F mixture robbing on sequential firing cylinders on a non-flat plane crank engine. Paired up with properly designed Tri-Y headers and exhaust system or a 180* exhaust system and I bet it sounds sweet too.

 

I worked on little Toyota with multi carbs years ago. Also had a friend with a 600 cfm Holley 4bbl on his Mazda, it was a REPU with a 1.3L rotary though. People would gasp seeing the big Holley on it but that rotary loved it. Those REPUs had a serious drinking problem though. V8 like fuel economy even stock. His actually got better mileage with the Holley after dialing it in. I always wondered if the 500 cfm 2bbl or 390cfm 4bbl might not have been a better option though.

 

I love watching this video with all of the intake tract reversion. Not EFI but still ITBs more or less.


This is the A/F mixture chaos going on inside the batch fire TPI induction system except you can't see it happen. People think port fuel injection is so clean and precise but it's really a mess in the runners and plenum but they just can't see it.

 

I love how you can see the reversion in action on setups like that.