View Full Version : RB25DET S1 AAC/IACV delete theory

05-07-2020, 03:47 AM
Hey everyone, so as my title states I have a theory on deleting the AAC/IACV systems on my RB25DET and I would like to see if I can get some feedback on it.. I won't lie, a huge reason for wanting this done is to clean up my engine bay, it has been one of my biggest goals with this build since I got it. Now I have read quite a few threads on this on multiple forum sites. It always seems 50/50 to me and it doesnt seem like alot of info is given from both sides, plus the threads are really old and I am hoping that someone has found a way to do this by now.

Alright so for starters I have a series 1 RB25DET
I have the Greddy intake plenum
stock turbo
stock fuel injectors and fuel rail
I have a NISMO FPR
350z ignition coils ( soon to be switching to the R35 coil packs)
and a billet throttle body

I also have removed the power steering and de-powered my rack, climate control has been completely removed since I bought it and have no intentions of adding. everything is manual and I have even removed the radio system entirely.

I know that the AAC is used for when the AC is on or when your turning and the power steering is under load, so I shouldn't need that system anyways. The IACV will control idle when the throttle is closed obviously. but some say that these systems are linked and work together to function.

Now my theory is, if I remove both systems and put block off plates on the plenum, then I can use the adjustment screw on the throttle body to slightly crack the throttle plate open to allow air in for idle. If I adjust the TPS to read zero when "closed" it will cut the fuel on decel and not dump a bunch of fuel in while not on throttle. From there I can use the adjustment screw on the ECU to fine tune the idle RPMS to where I would want them, around 900RPM. Also I am looking at contacting RSEnthalpy and having a Z32 ECU tuned to run my car, so would they be able to tune for these kind of things? I shouldn't need to make fuel adjustments to the FPR because I am not adding power just changing idle and hopefully the ECU can have adjustments made for AFR at idle.

I apologize for such a long post, just wanna make sure I have this explained well enough so I can get some opinions and hopefully find out if this will work as I plan.. Thanks for your help!!

05-07-2020, 04:16 AM
Good luck getting a solid answer for your question man, unfortunately I can?t help there but I would suggest you contact Martin at RSEnthalpy and ask him if he?s able to tune for what your asking for directly. He has tons of knowledge and can get you pointed in the right direction

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05-09-2020, 12:12 PM
That is a good idea, I'll send him an email today and see what he says. Thanks for the reply.

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07-01-2020, 01:28 PM
Well unfortunately this idea wont work. He said that its a good theory but it wont idle right cold unless you adjust it but then it wouldnt idle correctly when it's warm.

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07-01-2020, 03:24 PM
Well just block it off, and adjust idle by the throttle body and run racecar idle.

1200-1500rpm. So.etimes it works out good and is 900-1000

Thats ur option

07-01-2020, 04:04 PM
Convert to drive by wire. Use a Haltech ECU. It will eliminate the IACV.

07-02-2020, 05:38 AM
Convert to drive by wire. Use a Haltech ECU. It will eliminate the IACV.

Yea seems the most logical choice...