M4rk G

My 97 Uk Wagon had a badly fitted filter on it, which im in the process of putting back to the standard air box.

Problem is the join on to the Maf (the bit that can bolt on/off) is broken when the old induction kit was fitted.

i've sourced one on ebay and my bolt spaciing is the same but the diamater of my intake looked to be 80mm. Can i use the adaptor thats in the ebay add??

Will 4mm make any diffrence or have i measured it wrong??

Cheers in advance

Link: *NEW* MAF Intake Adapter 3" Subaru Impreza on eBay (end time 28-Feb-10 10:23:27 GMT)

Glowplug

iTrader: (8)

I had exactly the same problem and solved it in exactly the same way, 18 months later and NO problems

Splitpin

Any changes in the bore or (to a lesser extent) the length of the MAF tube will affect the accuracy of the airflow sensor's measurements, so the only correct replacement for a broken tube is an identical one.

If your car originally had an 80mm bore unit and you replace it with a 76, you will be reducing the cross-sectional area of the tube by over 10%, which will have a significant effect on the airflow/voltage curve - and will effectively richen up your on-boost mixtures (as well as likely limiting the ability of the ECU to correct the AFR under closed loop).

This will hurt your power and fuel economy, apart from any other issues (possible bore wash etc). You could consider this a temporary solution, but it would be far from ideal as a permanent one.

If you haven't bought the eBay item yet and you have the option to return it, why don't you buy it and check how the internal measurements compare with the OE one? If they turn out to be the same, you're sorted. If they're different, send it back.

The one thing you should avoid at all costs is replacing a tube of a certain size with one that is bigger, at least without ECU changes. That'll do the opposite of the above, leaning off your on-boost mixtures, with all the possible consequences.

As above, if you've replaced a tube of a given size with one that is a few millimetres smaller without rescaling the ECU, you do have a problem, although it isn't one that is likely to break your engine.

Glowplug

iTrader: (8)

Thanx for that Splitpin

Your opinions valued and points taken onboard as per usual

M4rk G

Hmmm confused a bit on what to do.

Can any one recomend a place to get an 80mm bore one??

M4rk G

ALl can flame me if they wish. I've managed to sort the problem.

In my haste to get it sorted i actually measured the out side of it rather than the ID. So The ID is 76mm.

I fail! Ban me if required

Splitpin

No flaming necessary! I wondered whether you might be doing something like that when I wrote my post - which is why the word "If" appears a bit.

At end of day the only thing that matters is that you've got it sorted - while the info in the thread will still be around to help others coming along afterwards (provided they search for it ).

Glowplug

iTrader: (8)

Fat chance

M4rk G

Yeah thanks again for the great advice. Just awaiting the postie dropping the stuff off and i can get using it again.

Search?? Whats that

joz8968

iTrader: (13)

I thought the internal diameter of the MY97/98 MAF tube was 80mm?! No?

If... so, and even though you've bought the 76mm MAF adaptor, then the 2mm concentric 'barrier' that this adaptor will create at the tube's very entry shouldn't affect the mixture, as the sensor is much further into the MAF tube. So the air mass has time to fill the tube before it reaches the sensor, and therfore the correct density will be measured... hopefully!