IACV solutions when fitting aftermarket inlet manifold and throttle body

[JAAASH]

So i'm looking at getting a side feed inlet manifold (racerxfab), with 75mm throttle body (RMR), alongside chargecooler installation, etc etc.

The new throttle body will have an adaptor allowing the Toyota TPS (Throttle Position Sensor) to be fitted, but won't have anything for the IACV (Idle Air Control Valve).

So i'm wondering what my options are here. Ideally i'd like to lose/eliminate it entirely, but i'm worried about it overly upsetting my idle. I'm on a Link standalone ecu, so technically i could adjust the stopper screw in the TB to always leave the throttle plate partially open, and then have my mapper adjust fuelling to stabilise idle.
After doing some searching/googling, i'm getting mixed answers. Anybody have any info on whether this is a viable option for day to day use or is it gonna be a real pig?

Thanks.

[C35Rob]

Can your ECU control a DBW throttle? If so then you can use the throttle for idle control, bearing in mind the larger the throttle plate the coarser the 'adjustment' of idle will be.

I know people that run no IACV and just use a throttle stop like you described to control idle (or maybe 'keep the engine running' is more accurate...) they're mostly track/weekend/drag cars though, they're a bit grumpy when they're cold and not really something you'd want on a year round driven car that sees regular stop/start cold driving

[JAAASH]

Hi Rob, thanks for the reply.

Good question. I don't think mine does support DBW. Link here - http://dealers.linkecu.com/TST205Plus so feel free to have a look and tell me i'm wrong.

It is only a weekend car really but I don't want it to be a pain in the a$$!

[ashley]

Your ECU has aux outputs, so assuming it can deal with the current requirements, and has enough spare outputs....you should be able to set up DBW, but for your specific install it might be a ball ache as it is designed to be plug and play with the stock car...so new wires, and changing the ECU strategies, not to mention a new DBW pedal...but all do'able. Worth asking a decent Link mapper to check.

Could you not (for simplicity) simply add a stock ICV to your new TB? Can't see it being very hard, maybe a bit of cutting/ machining and welding...would be a lot easier than going DBW.

[JAAASH]

I'd rather not go DBW if possible, as like you say, it complicates things.

Could you not (for simplicity) simply add a stock ICV to your new TB?

I'd rather not chop and weld into a nice new throttle body. I have seen people mount them to the inlet manifold. I wouldn't be against that as I could mount it lower down and keep it looking clean and tidy.

Also, does the stock IACV not leak a small amount boost, even when fully 'shut'?

[ashley]

The stock IACV system does seem to be a boost leak in the making, but if you plumbed it into your pipework upstream of the turbo (i.e. just before or after the charge cooler), then that would illiminate any potential leak.

I had the IACV mounted directly on my old inlet manifold- definitely an option

[JAAASH]

Plumbed into the pipework isn't bad shout actually, hadn't thought of that. Would it need to be a certain diameter or would a vacuum hose suffice?

[ashley]

It really doesn't need to flow much gas to allow the engine to idle, so a small pipe should be fine- but remember if you are plumbing it into the pipework it will need to be capable of sealing in whatever boost pressure is in there...so maybe vacuum pipes aren't the best idea, I'd go for some decent small diameter hose- maybe -04 or -06...but more than open to other suggestions, I tend to be overly cautious when it comes to potential boost leaks!

[C35Rob]

the few stock idle control valves I've played with are definite boost leaks, they don't cycle far enough to both fully shut and open enough to idle, regardless of what you did with the factory adjustment (which, iirc, is just preload on the return spring)

when my IACV died on the rollers I got it home by just pulling a blanked vac hose off the inlet manifold, so I'm sure a -6 hose would be fine, but I'd probably go with a -8 just to be sure

how much difference it would make is tiny though, while it's always desirable to engineer out any boost leaks like that, when an engine is consuming thousands of litres of air a min the amount of air lost through a slot about 2mmx10mm is almost insignificant, even with a high pressure differential across the orifice. certainly not something you'd ever be able to feel.

[JAAASH]

Cheers for the insight guys
Given me a much clearer idea of what i want to achieve

[shane34]

Make sure your throttle body is suitable for boost applications.

Just gone through a painstaking effort to fix my 75mm edelbrock throttle body.
Over 10 psi these leak.