I was thinking last night... ...mpg seems to really drop off quite noticeably within a month or so of fitting a new airfilter in the standard 1.6/1.8 carb airbox. I guess this is because it is really rather small as airfilters go. Is there any obvious reason why a gti-type airbox (which I assume has a much bigger filter area) couldn't be 'bodged in' by suitable hacking around of the carb airbox? Thoughts?
you would need to use a big block SPI type airbox, though i doubt this would really make much difference. might be an interesting project to try tho
Any particular reason why it would have to be an SPI one? I think they may be a bit harder to get hold of than a digi one? Any reason I couldn't remove everything to the right of '12' in this diag, make a square to round adaptor, then plumb into the 'trumpet' bit of the existing airbox (cutting as reqd for clearance to new box), removing the old carb filter?
mainy due to the way the airbox plumbs into the inlet, the inlet fitting is oval and quite far from the airbox. you could do it as you describe i guess. since spi is basically a carb it already has the ducting all the way to a small round fitting, so it shouldnt take much work to get it to fit, assuming the hole is about the same size as a carb. tho finding one to suit a mk2 may be tricky, SEAT one prob best bet. If you can get MK2 diesel or SEAT diesel/ABF you'll have a nice round hole on it perfect for fitting rubber tube too, ABF one will also have an inlet air temp sensor in which you could use for inlet temp experimentations
On the basis of the old saying "'Tis a gert-big fool that ignoreth the advice of RJ", I shall place a wanted ad for one of the airbox types you suggest. Cheers John.
Excellent suggestion (see post #2 ). A kind member has already offered a Mk2 diesel airbox to me though, so I'll give that a try as a first attempt.
mk3 spi airbox totally wrong shape, polo mk3 GT one may fit butr again probably not quite right. lower spec polo models no good as they all have pancake filters, and the g40 used a completly different intake setup as its boooooost
if you are chasing mpg then swapping to digi efi would be a big help, andy947 did it on his driver years ago must be loads of folk out there who would donate the bits lying around in their garages
I hear what you're saying Prof, but I have reservations. Firstly, my Driver is a 1.6; aren't all digi set-ups for 1.8 and larger? If it was a case of swapping in a whole engine, I may as well just buy a GTi. I'm not even (yet) convinced that I would see significantly more emms/gee with an 8V digi; I've not seen any huge claims on here?? With what I've got now (and appropriate driving style), I'm getting high-40s to low-50s*, tank after tank, especially when the air filter's nice and new. I do have another fuel saving mod installed, but I've not written it up yet, and no, it's not an Ecotek Valve or a strategically placed magnet. *Edit: I should qualify this statement; IIRC both times I've exceeded 50mpg there were long journeys involved, rather than my usual commute, and the highest, 52.4, was only on a half-tankful.
Do you sit really far back so you can only press the accelerator a little bit? I used to do that on my mk3 when i was really short of money and petrol
the diesel box would be my suggestion and i takes a digi air filter so they are aftermarket options too.
Looking at vagcat, the diesel one doesn't appear to have a warm-air feed, which is a shame. That would seem to mean that I'll need to relocate the mixer flap bit off the carb airbox onto the entry-point of the diesel airbox, or retain the original filter as well as the new one, otherwise the warm air wouldn't be getting cleaned. Hmmm. As usual, my enthusiasm may have got ahead of my understanding.
Dammit! You read all the way to the end of the thread, and someone goes and has the idea you were thinking of TDI airbox doesn't have a flappy metery bit. An ABF one might work too, or it might be too tall for the Mk2 bonnet. You'd need to make up a big hose from the exit of the airbox, up and over to cover the carb mouth.
