Brz throttle body issue (Grams 72mm)

[Tomomi]

Just wondering if anyone on here has this issue before or I'm just being stupid. I just recently purchased a grams throttle body and installed it. Disconnected the battery and reconnected after 30 mins and put the car on the on position pressed the gas pedal around 20 times did it 3 times to make sure the throttle body was recalibrated, and drove around 150 miles with the new throttle body. Just noticed that when I'm in first gear or second gear in my neighborhood the car would not slow down when I let off the throttle. It would just get stuck around 1700ish rpm around 9 to 10 mph like cruize control or something is on. Any help would be nice. Still kinda of new to this platform after just letting my rsx type s go recently.


Here link to the video I recorded.

[PulsarBeeerz]

I had the same issue while I had one. I think you have to remap the TB in the torque request tables. Although I saw a quantitative increase in MAFv usage while using it, I felt a bored out +2mm OEM would deliver the same results without the anomalies. I would a good decision and overall would have been cheaper....But curiosity.

[nikitopo]

Yes a bored +2mm OEM unit is the best option, without a need to touch the ECU.

[Ernest72]

There are many threads showing virtually no benefit for a bigger throttle body. Why invite issues. You likely need it tuned. Sorry I can’t help with the problem.

[Tomomi]

Thanks for letting me know guys. Should of known that I would need to retune it or mess around with the ecu. Ended up getting it since a friend sold it to me for real cheap lol...
Still had the same stupid idea that a bigger throttle body would make a difference, since was running an rbc mainfold with a hybrid racing throttle body with a tune on my type s. Thanks for letting me know.

[Ernest72]

Originally Posted by Tomomi

Thanks for letting me know guys. Should of known that I would need to retune it or mess around with the ecu. Ended up getting it since a friend sold it to me for real cheap lol...
Still had the same stupid idea that a bigger throttle body would make a difference, since was running an rbc mainfold with a hybrid racing throttle body with a tune on my type s. Thanks for letting me know.

Save it , when you have done everything else, like going FI with other mods, it might be worth it then. But ask your tuner.

[FunnyGopher]

I too experienced the same thing you're experiencing after installing it. I got into the habit of putting the car in neutral when going over speed bumps to stop the high idle. After mentioning this to my tuner and sending a log over, it's now fixed.

Compared to butt dyno and real dyno sheets of other modified 86s I've driven, there is noticeably more throttle response and torque delivery with the larger throttle body. There's a lot of people who say it doesn't do anything and not to waste your money. My experience with it is much different.

[Ernest72]

Originally Posted by FunnyGopher

I too experienced the same thing you're experiencing after installing it. I got into the habit of putting the car in neutral when going over speed bumps to stop the high idle. After mentioning this to my tuner and sending a log over, it's now fixed.

Compared to butt dyno and real dyno sheets of other modified 86s I've driven, there is noticeably more throttle response and torque delivery with the larger throttle body. There's a lot of people who say it doesn't do anything and not to waste your money. My experience with it is much different.

Not disagreeing with you, but the butt dyno is not that accurate. I have done many mods that I swear I feel it, but others don’t think so. I am now more of a test and see person. As long as the expense is not too high, and the car is running well, and you like it then all is good.

My example is I researched doing the Crawford blocks on my BRZ which has header, fr pip, exhaust and tune. Some said not much difference, others said it was worth it. So $300 later and a bit of a pain install, I definitely felt a difference and the car does pull better in the mid range. I am staying NA so every little mod helps, but is it worth $300, my official opinion is maybe., leaning towards yes.

[nikitopo]

The gains of a bigger throttle body are very very minimal, but the most obvious change is the throttle response. Some might argue that this can be achieved by other ways like a tune, but I prefer a mechanical solution

[FunnyGopher]

Originally Posted by Ernest72

Not disagreeing with you, but the butt dyno is not that accurate.

I stated I had actual dyno chart comparisons showing a difference in initial torque delivery. The "butt dyno" being a metaphor for driving feel. Throttle response is a driving feel, not a peak number on a chart, which is why I felt I share my opinion on the throttle response of different 86s I've driven with a combination of tunes/no tunes and larger/stock throttle bodies.

[86TOYO2k17]

Originally Posted by FunnyGopher

I stated I had actual dyno chart comparisons showing a difference in initial torque delivery. The "butt dyno" being a metaphor for driving feel. Throttle response is a driving feel, not a peak number on a chart, which is why I felt I share my opinion on the throttle response of different 86s I've driven with a combination of tunes/no tunes and larger/stock throttle bodies.

This same effect can be achieved by changing the throttle mapping in the tune or with a throttle manipulating device like pedal commander. i have testing this first hand with a larger TB, pedal commander and changing mapping in the tune all individually and every combination thereof.

All that is happening is the larger TB at say 10% throttle is now open flowing more air as if stock TB was really open 15% so it "feels" like it has higher response / torque delivery when driving around but that's also why peak numbers at WOT do not change unless you have FI and have a greater demand for air than the stock TB can fulfill.

This is also why people have no throttle "coasting" high rpm/higher speed issues because it is flowing more air at zero throttle input than it was before.

[PulsarBeeerz]

Originally Posted by 86TOYO2k17

This same effect can be achieved by changing the throttle mapping in the tune or with a throttle manipulating device like pedal commander. i have testing this first hand with a larger TB, pedal commander and changing mapping in the tune all individually and every combination thereof.

All that is happening is the larger TB at say 10% throttle is now open flowing more air as if stock TB was really open 15% so it "feels" like it has higher response / torque delivery when driving around but that's also why peak numbers at WOT do not change unless you have FI and have a greater demand for air than the stock TB can fulfill.

This is also why people have no throttle "coasting" high rpm/higher speed issues because it is flowing more air at zero throttle input than it was before.

Peak number and Tq delivery won't change without port matching the TB the manifold. You have to go beyond just slapping it on. Necking a 72-70mm, which is over kill anyway in my testing down to 66mm isn't going to have the same result as a 68mm port-matched to 68mm. But this will only be effective after throwing on all the usual bolts on. It work on just about every engine as long as the TB inlet is still flared. Straight through ones no matter how larger do not seem to work NA at least.

[86TOYO2k17]

Originally Posted by PulsarBeeerz

Peak number and Tq delivery won't change without port matching the TB the manifold. You have to go beyond just slapping it on. Necking a 72-70mm, which is over kill anyway in my testing down to 66mm isn't going to have the same result as a 68mm port-matched to 68mm. But this will only be effective after throwing on all the usual bolts on. It work on just about every engine as long as the TB inlet is still flared. Straight through ones no matter how larger do not seem to work NA at least.

If you pour a 1 cubic inch stream of water into a 4 inch diameter pipe, and then increase the pipe to 5 inch diameter, the volume of water and rate of flow will not increase as the restriction isn't the pipe size but the amount of water. its not like pouring too quickly in a funnel and the funnel slowly "fills" up and either spills over or you stop pouring.

The engine can only draw so much air, the TB size is already greater than the amount of air the engine can draw on it's own it is not a restriction hindering flow so going larger will have no effect on maximum power (unless FI) it will only change the throttle mapping up until maximum power because you will have greater airflow going through the butterfly valve of the larger TB at any given throttle position unless remapped to account for this.

[PulsarBeeerz]

Originally Posted by 86TOYO2k17

If you pour a 1 cubic inch stream of water into a 4 inch diameter pipe, and then increase the pipe to 5 inch diameter, the volume of water and rate of flow will not increase as the restriction isn't the pipe size but the amount of water. its not like pouring too quickly in a funnel and the funnel slowly "fills" up and either spills over or you stop pouring.

The engine can only draw so much air, the TB size is already greater than the amount of air the engine can draw on it's own it is not a restriction hindering flow so going larger will have no effect on maximum power (unless FI) it will only change the throttle mapping up until maximum power because you will have greater airflow going through the butterfly valve of the larger TB at any given throttle position unless remapped to account for this.

Sorry but in real world practice with a +2mm over-bored OEM TB or 72mm TB AND port matching IM I saw a 2-3% increase in MAFv usage. If there is a bottle neck the pressure will just be dropped at the next neck down in line. There's an entire flange after the TB which no one every takes into account. I should add I have an extrude honed IM that neckes down to ~70mm before the plenum. Grams TB uses a reducer plate to go from 72mm down to the OEM 66.5/67mm opening. Yeah it obviously wont make a different as the IM port size hasn't changed.



Your example isn't applicable to an engine for many reasons the main one being the lack of a pressure differential before and after the "funnel" and the manner in which air flows in an intake system.