Hey guys,
can someone give me a quick explanation of the IACV on redtop sr20det. I understand that it uses water temp to open a valve and let air bypass the throttle body during warm up, but why does it have an electrical connector. What signal is it sending or receiving? How is the ecu affected by its operation?

cheers tony

I'm not 100% sure but would have a guess it would be constantly varied via voltage (1-5v) from the ECU dependant on a few few things. Water temp on cold start and RPM when the ECU see the TPS in idle status. When to operating temps it should only really be controlled via the ecu when the TPS is at Idle (throttle closed TPS should read 0.24v as per FSM when throttle is closed and TPS idle switch is on.). I would crank out the same question here and see what the response is http://forums.nicoclub.com/zeroforum?id=138 Cheers

This is how the CA's logic works and should be similar to the SR logic
What ECU are you running. Are you using Nistune?

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1928 Model A CC Pickup

thanks mate,
im currently using the stock ecu, but will be adding the nistune chip/software when i can get it to the tuner. I just wanted to sort out the idle issue before i hand it over.

With the iacv plumbed in and connected, im getting surging at idle when it is at operating temperature. At first cold start its not too bad, only surges when it starts to get warmer. With your thoughts in mind, im guessing that it is the ecu which has taken over and is trying to control the valve.
With the iacv wiring still connected but the plumbing blocked off, i get a nice consistent idle. I just wasnt sure what effect this is having on the ecu.

I pissed my IACV off as it was stuffed. I don't have any cold start problems at all. It runs slightly rich on warm put big no biggie (have tuned most of it out with Nistune). I would say if you can't get it running well with it piss it off. Who are you going to to tune it? Have a chat to Sam and see if he's keen. I'm sure he has synced up twin sidedrafts before so should be able to do your SR.

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1928 Model A CC Pickup

i dont know how the sr20 iac is set up but thair should be an inspection cover on the iac motor. if so remove the cover and see how much carbon buld up thair is. clean the port if needed and lube the motor sharft with light oil such as wd40. and check for vacume leeks ie: perished lines ex. or your iac could be f#*!ed its not uncomen

I was thinking to get rid of the IACV, but i wasnt sure if it was providing vital ecu info. Good to know it isnt absolutely necessary. It seems to start fine when the IACV is blocked off, so i might just keep it that way for the time being.
Sam has tuned the car once before so i was going to go back and see him about the new setup. Hopefully he is willing.

The IACV contains a solenoid controlled via PWM from the ECU which regulates the idle speed.

It also has a mechanical passage controlled via bimetal spring for improved cold idle performance. On the S13 you can adjust how much via the Phillips head screw.

There is no feedback to the ECU from the IACV itself so you can disconnect the plug without any problems if it is playing up. Its worthwhile disassembling it and cleaning with carb cleaner.

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1971 Datsun P510 SR20DET 276 rwkW
2005 Mercedes AMG E55 350 kW
1969 Datsun P510 L20B EFI 95 rwkW
1975 Ford XB Fairmont GS Wagon 179rwhp
1980 Escort Van SR20DET unfinished
2002 Suzuki GSX1300R Hayabusa 185hp

Tony, how did you go with this? Did you end up cleaning it?
Or did you end up removing it when you went to the quad throttle body system?

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
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Funny you should ask Nik, it was only last weekend that I decided to make some changes to the setup. I was originally using all the s13 gear with the Pulsar n14 quads but I couldn't get the idle below 1200 rpm. The s13 combines the air regulator, AAC valve and FICD solenoid all as one unit which was a bit of a pain to try and regulate. So I decided to try the n14 gear, which uses individual pieces. I pissed off the cold start air regulator and the FICD which is used to bump up Rpms when when the A/C is on and only left the AAC valve connected. It seems to have helped lower idle down to about 1100rpm. The surging that I was experiencing back when I first completed the setup has long been solved. I think that was a combination vacuum leaks and itb tunning if my memory serves me correctly.

Just cleaned my IACV last night. Undid the 3 bolts, careful not to damage the gasket. Removed both AAC and FICD solenoid and cleaned them out with a bit of kero and then hit them up with some Inox/CRC
Then cleaned the spring and other sections inside the IACV system and there was heaps of crap in it. it was just caked with black oil. I looked inside the inlet manifold and it was relatively clean. So bolted it back on and took it for a drive tonight, and it was excellent. Best idle after a rev in ages. Now it doesn't conk out at the lights.
Now I've fixed that, I can concentrate on a few other things...

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
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#SR20Datsun @SR20Datsun