Rich or lean?

[eben80]

Hi guys, I'm busy fine-tuning the Reece-Fish carb on the AC Fiat and I was wondering about the mixture setting...
Does the "assisting air" from the air filter and it's hose mean that you have to set your carburettor slightly leaner than you would for purely atmospheric intake?

I'm not running an aftermarket filter and wanted to know if anyone has experience with aftermarket carbs using the standard filter?

[eben80]

sigh....

[Hazey-n-Marc]

I have the standard carb, and have relocated the airfilter to the spare room. I found it was running very lean on idle to start with so I adjusted the mixture a bit to compensate.

The best thing is to drive it and see. Also, if you can get it tested for emissions you will get a better idea of the mixture.

[eben80]

Strange, that is the opposite of what I would think. No air from the cooling fan should make it richer.
Thanks for your reply. I was just hoping to "verify" my hunch

[Hazey-n-Marc]

Mine is a bis (watercooled), the easier it can suck air in, the leaner they tend to get. Someone had fitted an aftermarket airfilter to mine, very badly, so removing it was the thing to do. I never used to run carbs with a filter, and I've never noticed the cooling fan make a difference to the power or tickover. That was on Celica's, scirroco's, golf's, Polo's, Winnebago, Transit's, Maestro's, 405, Ax, Sj413's and Granada, nothing aircooled though. Found pretty much the same on all of them.

[eben80]

aah see, I didn't read what you had. In the AC the cooling fan "pressurizes" the air through the airfilter and into the carb. My question would not be relevant for a BIS.

[Hazey-n-Marc]

Could you run it without the assisted air? Might be easier to set up. The carb is probably not designed with assisted air in mind, so you might find that you have to use very extreme settings on the carb, I would see what happens without the assisted air to start with.

[Hazey-n-Marc]

aah see, I didn't read what you had. In the AC the cooling fan "pressurizes" the air through the airfilter and into the carb. My question would not be relevant for a BIS.

That's why I didn't reply earlier, but seeing as no one else did, I figured if we come up with something horribly wrong, someone will set you straight 

[eben80]

Haha why thank you Mark.
A noble attempt 

[smallcox]

A tin of worms in that question,

Hi ,

Think I understand your question, ok there are a couple off factors in that question, induction lenght and type off filter. Only relating to the filter it is unlikely there is much difference at idle between a paper standard filter and aftermarket performance filter and no filter. with a CO tester like the MOT stations have it may just make a decimal difference unless of course the paper filter is old and blocked then the mixture will get richer but you know that from your comments. Another facter that will make greater differnce is the air feed to the intake hot or cold, but again within the world of a 126 this will only be slight. As for the air feed from the cooling drum, do not think this is pressurized to make any difference to the carb. At idle no difference will be noted and at hi revs the same is true.

I have cut open the ducting and the air flow from the cooling drum has to take a toturise path and very narrow channels so if performance is the goal do not use the standard filter box, the major plus for using the standard filter from the cooling drum is induction lenght is increased and therefor torque should go up at low down in the revs and it is this that when connected to a open carb would have the most influence to the callibration when tuned without the filter connected. You may at mid range after tuning the carb find the mixture goes weak at low revs when driving the car under load, but the fish carb callibration is not that critical to this.

Here Wormy wormy