1.8t cold start, what do you do?

[QuattroCalum]

Recently I've started the car and let it run until the revs drop to normal idle speed. On cold start it will fast idle at around 1200rpm then steadily decrease once it has warmed up a little.
I find this gives a much better mpg figure. When it's running open loop the mpg will cycle from 15.0-15.9 mpg then starts again at 15.0, it will do this two or three times till the ECU changes to closed loop then the mpg climbs normally.
I was just wondering whether anyone else waits till fast idle drops to normal or do they just drive straight away?

 

[DieselJake]

0mpg sitting on your drive idling, if doing this for economy drive slowly rather than leaving the car idling to warm up. I come from a background of old Japanese turbo petrol car's and I'm in the good habit of driving slow until the car is up to temperature then leaving the car to idle for a bit after finishing the journey.

 

[QuattroCalum]

I guess you missed the whole open loop closed loop part?


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[Gazwould]

What about in the loop.

What petrol turbo Jap DJ ?

 

[QuattroCalum]

1.8t question answered by derv heads #whatsgoinon?


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[DieselJake]

What petrol turbo Jap DJ ?

Starlet GT Turbo's and Glanza's; can get away with more on newer turbo car's but the basic principles are the same.

OP if you don't want answers don't ask questions. Quite obvious what should/shouldn't be done with these car's.

 

[Gazwould]

God those Starlets are light = fun .

 

[QuattroCalum]

Starlet GT Turbo's and Glanza's; can get away with more on newer turbo car's but the basic principles are the same.

OP if you don't want answers don't ask questions. Quite obvious what should/shouldn't be done with these car's.

From the self confessed keyboard warrior. If it was quite obvious what should /shouldn't be done with these cars then how would this forum even exist?

That's rhetorical before you reply.

 

[DieselJake]

The forum exists because you haven't closed the loop.

 

[QuattroCalum]

The forum exists because you haven't closed the loop.

Away and talk to Gaz, I cannae be annoyed wi yae!

 

[DrStrange]

QuattroCalum,

Whilst i havent factored in Loop, I've tried both and to be honest i no longer do the whole 'warm up, let drop to idle before driving' thing.

I didn notice any improvement at all and agree with Jake on this one - Even in extreme cold, I turn on the car and drive immediately but always below 2000rpm until car has reached operating temperature. ALWAYS.

It even mentions this in our neglected audi handbooks that has cobwebs on it. (To not wait, drive immediately)

On a seperate note..Wish I had more time to be on here these days..

 

[QuattroCalum]

It does get a bit tedious waiting on the fast idle to drop so I just wait about 10-20 seconds. When I did wait till fast idle dropped the car was markedly more responsive and smoother albeit the difference of open/closed loop running.

 

[DrStrange]

It does get a bit tedious waiting on the fast idle to drop so I just wait about 10-20 seconds. When I did wait till fast idle dropped the car was markedly more responsive and smoother albeit the difference of open/closed loop running.

Agreed, I did notice this also.

But this is just plain science i would asume - The fact the engine is still very cold and not as smooth to drive until efficent temperature.

 

[QuattroCalum]

The car will always be in 'closed loop mode' after the O2 sensors heat up (approx. 90-120 seconds). Until the O2 sensors are in their operating temp range which I think is 600', the ECU is in OPEN loop mode and NOT dynamically modifying the mapping..

The reason the SAIP (secondary air injection pump) in installed, is to inject O2 (air) into the exhaust manifold during the first 90 seconds after the engine starts to help burn off unburnt hydrocarbons and heat up the O2 senors so the car gets into 'close loop' mode faster and not relying on a pre-programmed map.

open loop mode - ECU predetermined engine settings, no adaptability in its control
closed loop mode - ECU controls settings based on EGT, O2 sensors, ....

 

[DrStrange]

That's interesting thanks.

I've always flirted with the idea of doing the SAIP delete which is apparenlty a useful delete as the tuner say, ''its one less thing to go wrong''.

But may well not do this now.

 

[QuattroCalum]

There really isn’t much to go wrong, the pump can fail but that really only happens if the combi valve fails. In 14 years of 1.8t ownership I’ve never had a problem.


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[DrStrange]

Ah, thank you. Good anecdotal info I need. It will remain put.