Griff willn,t run AFM

[wycoller]

Need some help,
SC500 Griff with Bosch AFM.
Engine died on me when giving it some,
Checked all fuel pump relays etc etc etc.
Engine will try to fire.
Disconnected AFM engine starts and runs, suspect AFM or wiring.
Note ECU not issue as swopped out and no change.
cheers for any assistance guidance spend,quinny, pasco, bluebottle, V8S, fing Lady Penelope
International Rescue for Griffs "okay and Doc"!!!

[David Beer]

I have the larger jag meter and the car cut out over a pot hole, only way home was with it disconnected. A quick search and one found on tut net at half price!

[paulathome]

Sounds like AFM, read Blizracing post on post lower down titled "1600rpm idle, kangarooing"
Paul.

[Bluebottle]

That is very interesting I've been told that i am the only one goosing afm's, and I've goosed three of the damn things in 5k miles :fume: feedback is key to sorting these issues out...Colin
(and yes, if disconnecting the afm makes the car run better its a safge bet you goosed it

I'm still trying to resolve a re-occuring missfire, and due to be on the rollers with MA next week For one last ditched effort before i through my toys out the pram and chuck the damn ecu through the nearest glass window [along with the naffi'n car :fume:]) MA will be doing mine and a mates S/C 500 which, may also have goosed a Bosch AFM last weekend as well.

I spoke the MA last week about my issue and he has been experimenting with some US made AFM's which may be a bit more robust than the Bosch unit..I'll report back when i get a bit more infor from next weeks r/r session.

[SonicHedgeHog]

What causes a AFM to fail?

[Bluebottle]

SonicHedgeHog said:

What causes a AFM to fail?

This is what i and MA have been trying to figure out, My last one wnet back to Bosch last week and i'm hoping to get some feedback on what failed, at least then we know where to look. Two schools of thought with my car, faulty wiring causing a voltage spike, which was MA's favourite but now i know of two other s/c cars that is looking less likely. My favourites are either missfire/blow back pulse or, the recirc valve is sending the air back down the inlet and the extreme temp differential is goosing it.

[SonicHedgeHog]

Bluebottle said:

SonicHedgeHog said:

What causes a AFM to fail?

This is what i and MA have been trying to figure out, My last one wnet back to Bosch last week and i'm hoping to get some feedback on what failed, at least then we know where to look. Two schools of thought with my car, faulty wiring causing a voltage spike, which was MA's favourite but now i know of two other s/c cars that is looking less likely. My favourites are either missfire/blow back pulse or, the recirc valve is sending the air back down the inlet and the extreme temp differential is goosing it.

Mmm, difficult to know how to stop any of those problems. It looks like mine has had it too so I'd be very interested if you find an answer. When do you think you'll find out about a better replacement?

[wycoller]

Bluebottle said:

SonicHedgeHog said:

What causes a AFM to fail?

This is what i and MA have been trying to figure out, My last one wnet back to Bosch last week and i'm hoping to get some feedback on what failed, at least then we know where to look. Two schools of thought with my car, faulty wiring causing a voltage spike, which was MA's favourite but now i know of two other s/c cars that is looking less likely. My favourites are either missfire/blow back pulse or, the recirc valve is sending the air back down the inlet and the extreme temp differential is goosing it.

Yeh im am going to bite the bullet and down the line go for mappable system and get rid of the AFM, by the way it was the AFM, probably heat related or maybe HT pickup! ( first looking at spending some pennies on a Tuscan S which will be well above book price as Divorce costs etc!!!!)
Well down side is that I was giving it some pain and just flashed a guy out of the way when all power went must just poured bucket fuel into cylinder and i ended up under his feet and getting a blasting, bet he had the laugh heh!! fking idiot in TVR now on hard shoulder with bonnet up. Yeh Colin get these AFMs sorted its not new now you,ve had plenty of failures.

[cinquecento]

I understand that the extra sticky oil used on the air filter to attract dust etc can find it's way onto the AFM internals causing failure.

If you use this on the air filter, don't be too liberal

[Bluebottle]

James, did the engine die when you were on WOT or as you came off the throttle? and were the revs above 3.5k rpm?

[2Munkys]

Bluebottle said:

That is very interesting I've been told that i am the only one goosing afm's, and I've goosed three of the damn things in 5k miles :fume: feedback is key to sorting these issues out...Colin

That's so bizzarre Hamish; I feel for ya . They aint cheap are they. Yet mine's been in place for five and a half years and 30,000 miles without issue.

[wycoller]

Bluebottle said:

James, did the engine die when you were on WOT or as you came off the throttle? and were the revs above 3.5k rpm?

i was flooring it in 4th well above 3.5k engine just died as though fuel pump had packed in ( similar thing happened when i went airborne, landed and power connection came loose on fuel pump,i twicked that straight away and was back in action very quickly
so tell me whats going on as i was out of the closed loop with the lambda.

Went drastically rich ? or so weak?
Whats Colin saying i,m expecting replacement under warranty i do not see prob with Colin but needs to be sorted as Dangerous.!!!!!!

[blitzracing]

If anyone has a goosed Bosch unit they dont want, Id like to have a look, both from a failure point of view, and if I can get it working, to compare it with the Lucas unit for airflow to voltage output. It strikes me it may not need a remap if you can get the voltage outputs to match for given airflow.

Mark

[Bluebottle]

blitzracing said:

If anyone has a goosed Bosch unit they dont want, Id like to have a look, both from a failure point of view, and if I can get it working, to compare it with the Lucas unit for airflow to voltage output. It strikes me it may not need a remap if you can get the voltage outputs to match for given airflow.

Mark

I'm pretty sure they don't need a remap Mark, if you get Mark Adams's tune resistor. It allows you to bring the output voltage range back within the ECU's range.

Bruce was that the Bosch unit you had? Would be interesting to see if any non supercharged installations have goosed them.
All mine have gone the same way as James', WOT over 4.5k rpm and sudden failure which kills the engine instantly.

Edited by Bluebottle on Tuesday 30th March 12:32

[spend]

Hamish have you tried separating the temp function out of the AFM? Always surprises me that the expert posts just talk about 'the AFM' rather than it being a box with the hotwire and a temp sensor ie 2 distinct functions which form inputs to the ECU.

But then again it just seems so much easier to change ECU and hope to get some of the 30bhp that Graham Walden found from mapped ignition..

[Bluebottle]

Good point Spend, no i haven't I think i have one of the old ones knocking about at Dulfords, I'll see if I can get hold of a goosed unit and give it to Blitz to play with.

[blitzracing]

Bluebottle said:

blitzracing said:

If anyone has a goosed Bosch unit they dont want, Id like to have a look, both from a failure point of view, and if I can get it working, to compare it with the Lucas unit for airflow to voltage output. It strikes me it may not need a remap if you can get the voltage outputs to match for given airflow.

Mark

I'm pretty sure they don't need a remap Mark, if you get Mark Adams's tune resistor. It allows you to bring the output voltage range back within the ECU's range.

Bruce was that the Bosch unit you had? Would be interesting to see if any non supercharged installations have goosed them.
All mine have gone the same way as James', WOT over 4.5k rpm and sudden failure which kills the engine instantly.

Edited by Bluebottle on Tuesday 30th March 12:32

Mark may well have a map specifically for the Bosch in one of the 5 available map locations thats tune resistor selective, but you would still need one of his chips. I dont think hes tried messing around with the AFM electronics itself, (its messy compared to good mapping unless by chance the voltage outputs are the same as the 5AM, and a remapping requirement is an expensive myth.

[blitzracing]

spend said:

Hamish have you tried separating the temp function out of the AFM? Always surprises me that the expert posts just talk about 'the AFM' rather than it being a box with the hotwire and a temp sensor ie 2 distinct functions which form inputs to the ECU.

But then again it just seems so much easier to change ECU and hope to get some of the 30bhp that Graham Walden found from mapped ignition..

There is no separate temp output from the AFM to the ECU, but there is an air temperature sensor along side the hot wire. This is there for reference against the cooling effect of the airflow on the heated wire, so bigger the difference, the more air is passing, and this effect is intergrated into the AFM's output voltage. Without this colder air looks like greater airflow and visa versa.

[2Munkys]

Bluebottle said:

Bruce was that the Bosch unit you had?

Yup.

[spend]

I would hate to encourage you a different line line of thought anyway Mark