Idle Valve maps (BOSCH)

[iceman_n]

i change the pwm of the valve to this but i keep PID and enrichemnt as it was, but i don't see any improvement to idle on cold start

[stevieturbo]

If you're only going to change one aspect when others are not right....you wont expect much if any improvement.

All parts must be right for anything to work, not just some.

[MarcoV6T]

i change the pwm of the valve to this but i keep PID and enrichemnt as it was, but i don't see any improvement to idle on cold start

Besides from the other variables and maps, you must keep in mind that your hardware will not always do(mostly not) what you want it to do in theory; when I was using the Bosch two wire idle valve for example, I needed to it give ~25-30% PWM to force it for closing completely(at 0% PWM it’s open, although you can adjust the sealed screw to close the valve at rest, but still you’ll need more than 10% PWM to let it start opening), then going from 30%->90% the valve opens completely, beyond that it closes again, this also depends at which frequency you drive the valve, if you change the frequency, you can start all over again.

Thus the first thing to do is to ‘calibrate’ your idle valve, pick the frequency which gives you the widest dynamic range, and then check at which duty(PWM) it’s completely closed and at which it’s completely open. Then use those boundaries in your PID scheme(although it’s not always good to let the valve open completely, because this can give you overshoot in the PID regulation, which will in turn fluctuate your idle).

Then of course you still need to tune fuel and ignition, but you need at least one starting point(base) which you know is working as you intend it to do so, otherwise you’ll be chasing your tail.

[VR6Turbo]

Depends how quickly the engine decelerates. I've often found it helpful to open the valve early (2500ish) with a little fuel and timing (but not so much as the car drives itself with zero throttle) to bring the engine more gracefully down to idle. Opening the valve a couple of hundred rpm above idle simply didn't work. It just stalled 5 times in 10.

Your base throttle opening is too small then.

Unless very large cams are fitted, and even then it should still be ok, base idle speed should be set via throttle blade or damn close to it.

That should pretty much prevent idle speed ever faltering too low.

Idle bypass valves are there in addition to the blade, they are not a replacement. Base settings must always be sensible for any system to work well. The refinements are to do just that, make them work even better

VW open the idle valve at 3000rpm, so I thought it appropriate to do the same. I am working on a road car engine with standard cams and I like to copy the OEM's approach where possible. The OEM approach is also to close the blade completely and let the ISV do *all* of the air bypassing.

I found the same problem with both DBW and and ISV. Engage the idle map too late and it will stall.

[stevieturbo]

I can see where you are coming from, but these are no longer OEM setups, with OEM control and refinement, so some alterations may need made.

In theory yes you'd leave the blade shut, and let the ISCV do the work. Assuming you size the ISCV properly to suit your engines airflow, and have enough control over the valve at all times
DTA doesnt even seem to have an initial cranking/start setting to achieve a fast idle for the first few seconds after start which would be nice. So initial start will be difficult to get as good as OEM on that basis alone.

Obviously an ITB setup does complicate matters. But the best and easiest way to get a good base idle setting is by using the blade. And then using idle control to fine tune afterwards. That goes for any ecu, it certainly isnt anything against DTA.

On a boosted car, depending on the idle setup in use, often above a certain throttle they actually close the ISCV otherwise it can leak boost. Just depends where the fresh air aspect is plumbed. Some are vented outside the boost pipework, some are internal so can remain open.

[VR6Turbo]

I never actually checked on my S80, but I don't think it opens the ISV/DBW blade until the crank syncs. With the OEM comptuter, it doesn't wait for a crank signal to engage the idle map, it just holds the ISV/DBW blade open whilst cranking for a much quicker, more consistent start. So yeah, something like that on the DTA would be handy.

[iceman_n]

i have some news...i keep the PWM map as it is (the first one that i post) and i disable the PID loop...it start's more easy and without foot on throttle but the basic idle is at 1400 rpm without the PID loop...when i enable the PID loop it goes again at 1100rpm...

also when i try to lower the values at PWM map nothing change (without PID loops) something happens with the idle valve.

my idle valve is bosch 0280 140 516 not 0280 140 512 that DTA suggets...

i think that the problem is that is needs adjustment the internal plate...how can i do it ?

[stevieturbo]

If you lower the values to say 0-5% and your idle still remains at 1100rpm, then there is too much air entering the engine.

Either the throttle blade needs closed more, or the valve you are using is allowing too much air into the engine ( assuming there isnt another air leak somewhere )

You need to find some way of either restricting airflow through the valve, or using a more suitable valve for your engine.

But testing using the PWM map only will allow you to find the base numbers that need to be in that map for it to work.

[iceman_n]

ok thanks...
the advance in the main map where must be at 750 and 1000 rpm ??
cause when I lower the values idle lowers a little bit...

[stevieturbo]

ok thanks...
the advance in the main map where must be at 750 and 1000 rpm ??
cause when I lower the values idle lowers a little bit...

There is no generic answer. And yes the idle will drop if you retard timing at idle.

But anywhere around 5-15deg would do for starters.

if it takes more timing and is perfectly happy and emissions are all good, then more may do no harm. I would not run any less than 5deg though.