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Discussion Starter · #1 ·
Well I finally did it. Got the blacktop manifold adapter I designed machined and man does this thing look a treat!

Not on the car yet since it literally just got delivered but I was excited and wanted to share

ITB turbo is the plan. Do I know that it is pretty much useless with a turbo? Yes. Do I care? No lol
 

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You may find that there will be insufficient vacuum to actuate a BOV when the throttles close with the lack of a plenum downstream of the TBs. This is one of the reasons you never see ITBs used on turbo applications.
 

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Discussion Starter · #8 ·
You may find that there will be insufficient vacuum to actuate a BOV when the throttles close with the lack of a plenum downstream of the TBs. This is one of the reasons you never see ITBs used on turbo applications.
I have the go fast bits BOV. That one is activated with a pressure differential so I don't think that would be a problem. I expect the brake booster not to be as helpful and idle map readings to be hard to tune for. I was pretty aware of some complications going into this but I'm stubborn as hell and want what I want lol.

Any other things you can thing of I should look out for? I no doubt missed a couple of things when deciding to do it.
 

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Discussion Starter · #10 ·
It'll be very hard to tune based on alpha N strategy without a good MAP signal. Not even the modern F1 turbo engines use ITBs. Good luck.
Aren't alpha N axes TPS position VS Engine RPM instead of MAP Vs RPM for the exact reason that idle is hard to tune? MAP would mainly be for boost. I'm not tuning it thankfully but thanks! lol
 

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TPS vs RPM tuning only works if the atmospheric pressure can be assumed constant. That rules out boost. You would need a third axis.

I think that the usual solution for ITBs is to take vacuum from a single runner and process it through a filter chamber that will give a averaged MAP value.
 

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You may find that there will be insufficient vacuum to actuate a BOV when the throttles close with the lack of a plenum downstream of the TBs. This is one of the reasons you never see ITBs used on turbo applications.
R34 Nissan GTR has ITB's.

It can be done, but it is a hassle and not really worth the effort. A properly sized single throttle body and the right tuning software will yield much better results with less effort.
 
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Yes you end up with alpha N base strategy with boost compensation based on a heavily filtered MAP signal.

True on the R34. It uses a mass airflow meter for fuelling and with a full plenum before the TBs it can recirculate the air from the bypass valve into there.
 

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Discussion Starter · #14 ·
TPS vs RPM tuning only works if the atmospheric pressure can be assumed constant. That rules out boost. You would need a third axis.

I think that the usual solution for ITBs is to take vacuum from a single runner and process it through a filter chamber that will give a averaged MAP value.
I found another solution at the beginning of this project was to run a vacuum line from behind each throttle into a combined block and then a line from that into a map sensor. I was planning on doing that and also using that for idle air until I decided on E -throttle
 

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You can do that, but drivability is going to suffer. As stated above, Alpha N is going to be the most robust way of tuning around this. Possibly something like GM does on the LT engines as well with VVE tables and commanded torque. Most easily done with such a novelty addition is going to be Alpha N.
 
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