Air flow meter

[SwanJack]

I have a large misfire under load towards the higher end of the rev range and my local indie has diagnosed the AFM as the culprit. Anyone have any recommendations as to where to send it of for a refurb, or has anybody used the after market copies sold by land rover specialist's with any degree of success (assuming of course that TVR did not alter them for the 400 in any way). Thanks.

[blitzracing]

They are bog standard landrover parts- a Lucas 5AM. Genuine Lucas ones are around £200, second hand about £30. There are lots of Chineese copies out there that look identical, but dont have the brand name stamped on them, but I would not recommend replicas- the Bosch copies I tested where terrible- the calibration was all over the place.

[debaron]

+1

Blitz is right, the copies are terrible - I had one and ended up dumping it!

If you must get a new AFM, get a proper Lucas one but why not put that £200 to good use and go Megasquirt and ditch the whole Lucas setup including AFM?


http://www.extraefi.co.uk/RV8_Kits.html#pnp


Ryan

[chrisdurham]

on the Rv8, when going aftermarket ECU on a fairly std engine, is there any performance gains to be had? or just other factors such as reliability and smoothness etc?

[debaron]

chrisdurham said:

on the Rv8, when going aftermarket ECU on a fairly std engine, is there any performance gains to be had? or just other factors such as reliability and smoothness etc?

Mappable Fuel only - probably not a great deal

Mappable Spark & fuel - yes! The exact numbers will vary but some reports suggest as much as 30 bhp on a healthy engine

Basically the dizzy is complete compromise. The ability to control the exact timing of the spark for varying conditions is much more efficient.

[blitzracing]

An honest answer indeed- not the usual "you will gain at least 300bhp" thing.

[Bassfiend]

I had the AFM and dizzy junked and went CANEMS with MAP and MAT sensors a month ago and I have to say that on the whole it has been a truly life-affirming experience.

I do have a couple of mapping niggles that the installers are sorting out for me next week (it's taken a month simply because I've been away for work) but TBH I'm so glad to be shot of the old setup. The drive generally is so much easier, there's linear pull through the rev range and I've gone from just breaking 20mpg on a run if I was lucky to a good solid 28mpg.

Another side-effect seems to be that underbonnet temperatures feel like they have come down.

Phil

[gavgavgav]

... or you just get a good second hand one if that's all you need. There is a huge price difference between swapping out the AFM to swapping out the whole system.

[Meatball]

Theres enough of us who have junked them so there must be some cheap second hand ones kicking about - stick a wanted advert in the classifieds

[SwanJack]

There's a couple of 5AM's on ebay that have come off Jag XJS /XJ40. Will these do, or do they have to come off a Land/Range Rover??

[Ribol]

Bassfiend said:

...................I've gone from just breaking 20mpg on a run if I was lucky to a good solid 28mpg.

Another side-effect seems to be that underbonnet temperatures feel like they have come down.

Then there had to be something wrong in the first place because I have always had that sort of mpg on a run from my 400 economy model.

Not sure why the underbonnet temps would change, unless you had some sort of existing mixture/timing issues that were corrected at the same time?

[blitzracing]

SwanJack said:

There's a couple of 5AM's on ebay that have come off Jag XJS /XJ40. Will these do, or do they have to come off a Land/Range Rover??

The Jag ones are at least missing the CO trim setting on the side, so I dont know what affect that would have- Id stick to the Rangie one.

[lestershaw]

im pretty sure i have a refurbed 4.0 litre one somewhere, and a 5.0 used one if thats of any help?
Lester

[blitzracing]

Bassfiend said:

I had the AFM and dizzy junked and went CANEMS with MAP and MAT sensors a month ago and I have to say that on the whole it has been a truly life-affirming experience.

I do have a couple of mapping niggles that the installers are sorting out for me next week (it's taken a month simply because I've been away for work) but TBH I'm so glad to be shot of the old setup. The drive generally is so much easier, there's linear pull through the rev range and I've gone from just breaking 20mpg on a run if I was lucky to a good solid 28mpg.

Another side-effect seems to be that underbonnet temperatures feel like they have come down.

Phil

I think a big failing of the 14CUX is it sticks to closed loop below 3400 rpm, (which from memory is at least 85 mph in top - on a G33 anyway) so at anything below this speed it holds the mixture richer than it needs to be for cruising just to suit the emissions laws, so you fail to get anywhere near the best MPG, plus the distributor set up prevents you from advancing the timing as far as needed for best economy- both things can be addressed with an aftermarket set up.

[Ribol]

blitzracing said:

I think a big failing of the 14CUX is it sticks to closed loop below 3400 rpm, (which from memory is at least 85 mph in top - on a G33 anyway) so at anything below this speed it holds the mixture richer than it needs to be for cruising just to suit the emissions laws, so you fail to get anywhere near the best MPG, plus the distributor set up prevents you from advancing the timing as far as needed for best economy- both things can be addressed with an aftermarket set up.

That may well all be true but no healthy 400 just manages to break 20mpg on a run.

[Bassfiend]

blitzracing said:

Bassfiend said:

I had the AFM and dizzy junked and went CANEMS with MAP and MAT sensors a month ago and I have to say that on the whole it has been a truly life-affirming experience.

I do have a couple of mapping niggles that the installers are sorting out for me next week (it's taken a month simply because I've been away for work) but TBH I'm so glad to be shot of the old setup. The drive generally is so much easier, there's linear pull through the rev range and I've gone from just breaking 20mpg on a run if I was lucky to a good solid 28mpg.

Another side-effect seems to be that underbonnet temperatures feel like they have come down.

Phil

I think a big failing of the 14CUX is it sticks to closed loop below 3400 rpm, (which from memory is at least 85 mph in top - on a G33 anyway) so at anything below this speed it holds the mixture richer than it needs to be for cruising just to suit the emissions laws, so you fail to get anywhere near the best MPG, plus the distributor set up prevents you from advancing the timing as far as needed for best economy- both things can be addressed with an aftermarket set up.

3,000rpm on my rev counter in top gear was 90mph on my road angel ... to get to 3,400 rpm I would be doing well in excess of 100...

...and of course I've never done that!

Phil

[edo]

The AFM on mine was the culprit of some seriously terrible fuel consumption, kangaroo'ing at 2k under light throttle, and a soot covered rear bumper!

Picked the car up today with the new (reconditioned) AFM, and the car is running like a dream. Hoping to better 120 miles out of a tank too!!!!!

[gavgavgav]

blitzracing said:

I think a big failing of the 14CUX is it sticks to closed loop below 3400 rpm, (which from memory is at least 85 mph in top - on a G33 anyway) so at anything below this speed it holds the mixture richer than it needs to be for cruising just to suit the emissions laws, so you fail to get anywhere near the best MPG, plus the distributor set up prevents you from advancing the timing as far as needed for best economy- both things can be addressed with an aftermarket set up.

That is interesting to know. I wonder if it's more economic keeping the revs high in a high gear rather than changing down a gear?

[blitzracing]

You dont really win on that one, as the efficiency of a 4 stroke drops off as you use less throttle due to the fact you draw in less air, so the compression ratio drops and the heat released from the burn drops, so the best thing for MPG is a high gear, lower revs and a more open throttle, which of course is stuck in the closed loop region- you cant really win unless you run the non catalyst map in open loop. Even then my car still runs richer than need be at around 2000 rpm- which is annoying as this is typically what you tun at in day to day road conditions. I dont know if this is particular to my engine / map or common place. I hope to be able to crack the fueling tables in the map with the RoverGauge software, as it displays the map load values as you drive the car- so the idea is if you know when it runs rich, just reduce that value in the Eprom for that location, but I suspect its a lot more complex than this. Ive never seen more than 22 mpg on a 4 ltr engine in or closed loop- so there have to be some mpg gains in there somewhere.

[fausTVR]

Baffles me this fuel economy in chims thing. Just got a pb 26mpg on a hoonish 2up run (including town bits). I get 25mph/1000revs in top so prob a low ratio diff giving a theoretical max of 'only' 150ish. I'm assuming the lucky 1st owner specifies the diff ratio? When I bought the car I niavely thought I could coax 30mpg if I really tried -not the point of these cars I know. Seems sometimes you get your cake and eat it -when I try for economy by granny type driving (short shifting-light foot), the result at the pumps aint that impressive, it would appear you have to enjoy the thrust and revs a bit.

My car is standard and still low miles, well behaved so I can't justify the ignition upgrades, step change though they would be I'm sure.