Fans come on, revs dip [LS1 tuning]

[35R]

Tuning an 04 Monaro (idle) something frustrating that has been bugging me for a while. When the fans come on (set to 94 deg atm) I get a dip in revs. it seems to recover and idle ok, but sometimes it almost stalls.

I've tried re-tuning the running air flow (raf) tables a couple of times, and also bumping the accessory torque table values, but that doesnt seem to help neither (perhaps I should be decreasing values in that table?) I cant find much documentation on that table. I have a 25% UDP; which I think may be related.

Any ideas?

[SSUte01]

Dunc,

The revs will dip a little when the fans come on but should recover to the desired Idle speed.

See attached pic for where I believe your troubles lie. If RAF is fine sans fans including using PS and AC and it is only the fans then the table attached will help you out.

The worst that can happen if you make this table too large is that the STIT and eventually the LTIT will go negative to compensate when the fans are on. This can cause a dip however when the fans are first turned back off too. Best to try and get it close. Calibrate it the same way you would RAF, turn the fans on using the bi-directional controls and increase these values until the idle doesn't dip and the STIT is reasonable within +/- 0.50 - 1 g/sec. (in all honesty 1g/sec is a fair tolerence but acceptable)

It may also be a combination of RAF and fans but likely the fans airflow is the culprit.

Let us know how it goes

What are the current values?

http://www.trackchat.com.au/media/data/500/medium/Fan_Airflow.JPG

[35R]

Dunc,

The revs will dip a little when the fans come on but should recover to the desired Idle speed.

See attached pic for where I believe your troubles lie. If RAF is fine sans fans including using PS and AC and it is only the fans then the table attached will help you out.

The worst that can happen if you make this table too large is that the STIT and eventually the LTIT will go negative to compensate when the fans are on. This can cause a dip however when the fans are first turned back off too. Best to try and get it close. Calibrate it the same way you would RAF, turn the fans on using the bi-directional controls and increase these values until the idle doesn't dip and the STIT is reasonable within +/- 0.50 - 1 g/sec. (in all honesty 1g/sec is a fair tolerence but acceptable)

It may also be a combination of RAF and fans but likely the fans airflow is the culprit.

Let us know how it goes

What are the current values?

http://www.trackchat.com.au/media/data/500/medium/Fan_Airflow.JPG

Thanks for that Luke, that seems to make sense. My values are the same as the screen shot above, but i will try and tune the values as you suggest. Many thanks.

[Sonny@AutoWerks]

Duncan i dont know wats its called on hp tuners,though on efi live its called desired airflow,check those numbers,watch the fan compensation tables as too much can really make the idle unstable.

regards sonny

[35R]

Duncan i dont know wats its called on hp tuners,though on efi live its called desired airflow,check those numbers,watch the fan compensation tables as too much can really make the idle unstable.

regards sonny

Thanks Sonny, I think they are the same things as mentioned above. Still havent got around to tunign the cooling fan airflow! too much going on in the house with a newborn.

[VYss Kiwi]

My Programmer has set the cooling fans to.First one comes on, then a count of three, then the other one comes on.there is no disterbence with the Idle.works really well.Hope this helps anyone reading this.These cars only use 1 fan as stock.Programmer can make both work.This cools the engine much faster.cheers