Was browsing the net earlier looking for info on how to internally "tweak" an AFM & stumbled upon this... VW Vortex 8v AFM thread Might take a while to read so il summarise... Seems you can fit a BMW 535i Airflow meter as a larger, & therefore less restrictive plug & play replacement for the O.E Bosch VW item... The bias spring inside needs slackening & you will need an adjustable Fuel Pressure regulator to prevent the car leaning off at high RPM Probably of most interest for those people with increased capacity engines or considerable breathing mods where the O.E AFM may prove restrictive.. The guys on Vortex seemed to think mid range & top end breathing was a great deal improved... What do you all think?? Edited by: chrismc
Sounds promising! Ive just been chatin to an american who said that on some k-jet volvos the airbox is made of ali with a 2 and half inch cold feed and it fits vw k-jets. Go on chris give it a wurl!
Might well do.. Porsche 944 & Vauxhall Carlton/Senator 3Ls are other possible donor cars... Might have a scout round the local scrappies..
I've been banging on about this for months! A larger AFM is the only way to break through the 160bhp barrier. I've just not found anyone with the knowledge/skill to try it yet!! I spoke with Vince at Stealth a month or so ago and planted the seed in his mind in the hope that he would be interested in developing a mod on my 2litre 8v but a loose crank pulley destroyed the end of my crank last week and I've just paid out a small fortune having the keyway welded and machined (ouch!) and have therefore spent too much of the fighting fund for this quarter!! Another source of flow meters are Ford granada V6's but they have two of them - one for each bank of three cylinders and I think they could be too small. The BMW 535 would seem to be the right size...Is this a V6, V8 or a straight six? I think the secret is to think about the horsepower of the donor car, how many cylinder's are served by how many AFM's and then you can assess whether it's going to flow enough air for about 170-180 bhp.
Why not go for Digi 1 instead, then you have no AFM and no restriction whatsoever - relatively easy swap too, and cheap........
the only point at which it matters is at full throttle, at part throttle exact fuelling is important for economy and driveability. what about another flap somewhere opens a pipe that completely bypasses the AFM - but only at full throttle (maybe the boost return mechanism that runs off the throttle cable off a G60 could be adapted) , you'd need a remap to sort out the fuelling at full throttle - i think the ecu runs maps for closed/part/ and full throttle (and input from the AFM) so it can be mapped in without affecting fuelling at other points - but anyone thinkin of doin this has proly already got a chip in to accomodate other mods the fact that the ECU will think that the AFM is closed (cos it'd just spring closed) at full throttle will have to be sorted in the maps, it might be difficult to modulate the power at just off full throttle, as the air switches from goin through AFM to the bypass reckon that'd work?
I think it will be a simple enough swap to do... The new AFM will need the lid removing & bias spring slackened to allow for the fact that you only have 1800 or 2000cc capacity compared to 3500cc hence lees vacuum.. When the AFM reaches its wide open point..fuelling is then RPM based within the ECU... Because the new AFM will theoretically allow more airflow the car will run weak. An Adjustable FPR should be able to up the fuel pressure enough to richen up the top end... Bear in mind it would all need to be carefully dialled in on a RR. To go digi 1 or rig up a seperate flap etc etc seems like too much hard work to me..especially as it will only flow a certain amount more air before the next most restrictive bit of the system then holds it back....(Throttle body most probably) There seems to be a large variety of donor cars to choose from 535i,Senator,Carlton,Granada etc etc so it could prove to be a relatively inexensive mod..
Did some investigating at the Scrappies today.. The 535i AFM is the only one I could find thats bigger.. Does anyone know how to go about upping the fuel pressure regulator from 3 bar to a 3.5 Bar... I know it needs to be squeezed in a vice or something..Havent got a clue how far though...piccies of before/after would be great... Would sooner do this than shell out for an FSE Power Boost Valve as they are pricey..
GREAT! interesting idea, this forum is badly in need of more originality like this. Unfortunatly your idea wont work though, searching the net for control theory on "bumpless transfer" should enlighten you as to why. mark
Any adjustments to the FPR will effect the whole rev range. re-mapping can adjust parts of the rev range that are lean. if your injectors cannot keep up at higher revs, you need bigger ones. M.
Hook it up to an air supply and a pressure gauge, then squash it in a vice until the guage reads the pressure you want. There is a guide somewhere but I can't remember where - but it's an easy job.
If you're going to go to all this trouble, just get rid of the VAM and install a throttle position sensor. It can be wired to the VAM input on the Digi II and only requires remapping. I have many, many more details if you are serious about this.
The standard injectors are up to the job AFAIK... I guessed the FPR mod would make the car run rich lower down an adequate at the top end... The big problem with a remap is no-one seems to be interested in mk2 Golfs anymore, & I dont want to switch from an AmD chip to a Superchips Icon etc etc A different FPR would seem to be a cheaper solution in the short term, so I can at least get the car running with the BMW AFM & evaluate its performance...
read this with interest as i was always curious about tsr/amd's fix, which was something called filmstar which replaced the airflow meter with a hot film sensor and a box of tricks to match the outputs to the digisystem. was reading my boss's bmw mag over the weekend and in there it mentions replacing the afm on a 325i with a hot film sensor too. I think this would be a better investiation than just another big flap. in an old VW audi driver the fimstar was tested and returned 23bhp on it's on with no other mods!
well still got to pay for ecu TSC, but just another option. AMD used to charge a bit for it, but i'm sure there is a cheap scrap yard type option out there.
You can get the Digi 1 ECU's on German Ebay for dirt cheap - most of mine cost me less than 20 euro each!
