Goosed 5AM ...

[rigga]

Well common i guess but of late the car has been a bugger to start,more so than the normal over rich nature,had issues in the past but they seemed to clear,but the last two starts have been awefull,very rich,revs all over the place and had to give it a big bootfull for it to catch and prevent it flooding completly,running on odd number of cylinders etc,after the initial trouble then runs fine and dandy,until last saturday,ran like a pig all day i was out,cutting out,revs fluctuating wildly as it attempted to sustain a steady idle,until funnily enough when i got home and was opening the garage and it ran perfect again ... as it would,so today armed with the excellent testing info often posted by mark (Blitz) i attempted to find the fault and the first thing that failed was the AFM,initial spike of 18-22v which is interesting on a 12v system,then 0.85-0.9v,slowly dropping to the reccomended 0.35v mark,also interesting the voltage then stays at 0.35v when the ignition turned off for a couple of seconds,then degrades down to zero ...... so my AFM i guess is foobar,now questions
1) Obviously where is the best place to source these now ? common LR ones as long as 5AM ok ?
2) once they fail can they start working ok again ? as in the different running symptoms i had,or when they go are they then always a failed part ?
3)Anyone got a good tested untit lying around they would like to part with,good tested being the main point here as i believe there are some new ones that are not exactly good quality,though i guess if you do have a good one you would want to keep hold of it for the inevitable happening.
4)Blitz ... have you done any more developments on these regarding modded versions ? i know you were experimenting at one time

And lastly,just to open a can of worms,would a TF afm be worth having along with the req chip as its a more open design and less restrictive,and would they be more reliable than the standard items ?

Edited as im an idiot with numbers ....

Edited by rigga on Wednesday 13th April 15:35

[Mr MoJo]

Someone far more knowledgable will be along shortly I'm sure, but if you're considering upgrading as opposed to replacing I would go for the Bosch AFM and Tornado chip etc.

I fitted this little lot last year http://www.actproducts.co.uk/shop/ik005-tornado-5-...
Its made a huge difference to the drive of the car and increased the power from 270 to 290 just by bolting on and plugging in. I'm booked in with Mark Adams on Monday to get it fully mapped on the rollers so should be even better again then.

Theres pages and pages on here regarding the TF kit, some great results, some not so great, but I'll let Blitz go into that when he arrives

[blitzracing]

There is something very wrong with those measurements, they seem to be out by a factor of 2, as you say you only have 12 volts to start with, so no way will you see 18 volts! As for the AFM's the 5AM comes in various shapes care of the bolt end castings, so OEM part numbers vary dependent of the origional use, but the sensor part and electronics is exactly the same, so the worse case is you have to remove the casting from your AFM and put it on the new one if the pipework wont fit. In terms of upgrades, I dont believe there is any gains to be had what so ever below about 250 BHP, in fact in a recent rolling road test of a Pattern Bosch unit electronically altered to match the 5AM,s voltage response on a well tuned 3.9 actually lost 2-3 peak BHP even though the AF ratios where identical, but I dont know why. I think there are some power gains to be had on the 5 ltr motor where the AFM can be a bottle neck especially if the engine is tuned, although Ive not had the situation to be able to test the pattern Bosch against the 5AM on a 5 ltr. Mark Adams quotes his set up with origional Bosch AFM and chip is worth about 10 BHP and 15 ftlb on a 5 litre, but its expensive. As for the Torqueflow- Im not a fan, as its just a stock AFM sensor with the electronics PCB badly bodged to try and match the altered airflow scaling of using a TVR 5 ltr chip on smaller engines. In some cases it also needs the fuel pressure to be altered.

[rigga]

Was suprised to see the initial spike,and it was just that a momentary measurment,and not only at 18v but at other variables above the normal 12v running battery value,as i repeated the test many times to confirm the readings,then it would read the 0.8-0.9v steady that i presume indicates a failed unit,and then gradually drop to the norm 0.35volts,is it normal to even read battery voltage first when the ignition is turned on ? as from the testing procedure mentioned it never says anything other than the nominal 0.35v if ok or the slightly higher o.8v or so if its failed.
Not after any real upgrades just wondering what other AFM could be used that might be more reliable,i understand the TF and its build as its been mentioned a lot previously,it was just a thought as to the tube design,mine is a 5ltr by the way

Edited as realised my voltage readings were listed wrong with the decimal point in the wrong position. ..oops sorry Blitz

Edited by rigga on Wednesday 13th April 15:33

[blitzracing]

The spike is just the hot wire warm up, the critical bit is the idle value, that should be around 1.7 volts. If you are seeing a genuine 3.5 volts it is truely goosed, and will be over fueling horribly. As for the physical TF tube design, its crude, and it has some turbulance issues at low airflows, but the ECU has a wide enough tolerance fueling wise to be able to compensate, so they do work on some cars. Ive put some of the technical stuff on the last three pages here:


http://www.pistonheads.co.uk/gassing/topic.asp?h=0...

[rigga]

Blitz,
Never started the car to get the idle value, as to my mind its failed anyway with the initial rise above 0.8v and then slowly dropping back down to the normal 0.35v value of a recognised good unit, the cold start being that bad i didnt want to risk flooding the engine,or even not running the engine long enough to fully warm it.
Ill get another unit and try that to see if its a complete cure....again thanks for the info you post, very helpfull.


Edited to show correct value readings for AFM ...... Finally

Edited by rigga on Wednesday 13th April 15:37

[rigga]

Right just to update today,the car starts fine,runs brilliantly again with no cutting out and no issues whatsoever .... and the only thing i did was release the petrol cap and had a big release of air,it is a Leven cap and might therefore be a tighter seal than the standard,but thats the only thing that i did since the last time it ran very bad,just thought id post up if it helps anyone else in the same position.

[Mr MoJo]

Out of interest have you left the cap loose ? Notched the rubber seal or drilled a small hole in it ? My cap does exactly the same and my car suffers the odd cut out / stalling episode coming to a 'spirited' stop at junctions too.

[Pasco]

Just nik the cap rigger did mine about 5 years ago works a treat

[Mr MoJo]

Pasco, cap rigger is rubber seal right ?
Did you just cut a groove from outside edge to inside or cut right through so there's a gap in it ?

[rigga]

Ive not touched the seal, just not fully tightened the cap down,its still secure but not excessivly tightened, might attack the seal if it happens again but pretty sure it was vacumn in the tank that caused my issues...... prob would never have happened if the car was used daily and therefore refueled more often.

[Pasco]

Mr MoJo said:

Pasco, cap rigger is rubber seal right ?
Did you just cut a groove from outside edge to inside or cut right through so there's a gap in it ?

I will have a look later but i'm pretty sure I cut a small V both side of the inside cap rubber seal around 180deg apart.

IIRC Levan Technology used to supply details of how to do this mod in the dim and distant passed as it a easy fix for a Bunged up carbon canister.