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Both my cars are GEMS and both have singlepoint LPG systems on them so there is a mixer bolted to the throttle body although I'm not sure if this is relevant. The MAF sensor on the Ascot had gone intermittent so some days it would be fine but sometimes it would give no readings (current airflow 0.0 Kg/Hr irrespective of revs) which meant it was a bit of a bitch to start unless I forced it to start on LPG. Bought a replacement MAF sensor, genuine Sagem with a manufactured date of 10/07, so a recent one. The MAF on my car was an aftermarket one so decided I would fit the replacement to mine but would check the readings I was getting before swapping them over.

Checked the readings on my car and found them to be about right, around 22 Kg/Hr at idle, rising steadily up to around 60-65 Kg/Hr at 2,000 rpm. RAVE tuning data says it should be 20 plus/minus 3 at idle (so within limits) rising to 60 plus/minus 3 at 2,500 rpm (so a little on the high side) However, when I checked the Calculated Load Value, it was hovering around the 23-24% mark at idle in Park and not the 2.8-3.8% that RAVE says it should be. Initially thought that maybe there was a decimal point in the wrong place error in the Nano but at 2,000 rpm I was showing a calculated load value of 35-40% and not the 10% at 2,500 rpm I should be seeing. Swapped the MAF sensors so I now had the genuine Sagem replacement and checked again. Readings were damn near exactly the same.

Then fitted the known working aftermarket MAF I had just taken off my car and put it on the Ascot. Fired up immediately and left it running to warm up. Then checked the readings and they were almost identical to on mine. Airflow within limits at idle, slightly high at 2,000 rpm but still with a calculated load value far higher than it should be. I reset the adaptive values on both cars so had a baseline to work from but that made no difference to the calculated load value.

I'm wondering if the restriction caused by the mixer in the intake is affecting anything and will see if removing it makes any difference (when it's a bit warmer outside) but does anyone have any idea why the MAF readings seem about right yet the calculated load value is much higher than it should be?

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In both cases I was running on petrol although the MAF and Calculated Load values didn't change when I switched to running on LPG.

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It's been a while since I looked at CLV stuff but I would say that RAVE is wrong, although different defintions of CLV do exist.

However if you take the normal/coventional definition- " % of Max. torque at sea level etc" - then clearly 10% at 2500 RPM is far too low,
whereas 35-45% seems more likely ?

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But when there is no load on the engine, although I have since read that it will be lower in Neutral than in Park although I can't see why, just revving it up to 2,500 rpm shouldn't increase the load. Or at least that's how I would see it. If anything, once things start spinning more there will be less load due to the frictional losses in the engine and the flywheel affect of the torque converter should allow it to spin more freely? Just intrigued as to why my figures are so different to what RAVE says they should be while being the same on two different cars. Unless it is something else that the Nanocom works out and displays differently to how LR would measure it. When I have another play I'll try my generic scanner and see what figures that gives.

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Off the top of my head my GEMS (petrol only, no LPG) reads roughly 8 or 10 times the rave figure, or I think that's what I worked it out as. That was over a year ago, but my figures (I have written down somewhere) are roughly 20-25 calculated load.

MAF readings looking right from idle and at revs, and something like 20-30 on the nanocom for calc' load has happened to mine with different MAF sensors, TPS and idle screw settings. Either it reports incorrectly or rave is wrong, I haven't been able to 'prove' the car's at fault otherwise. My intake air sensor is about half a day slow to pick up, but I can't see it affecting warm running that much - maybe I'm wrong there, but they are either a bit hard to find/remortgage required, there's a reason I didn't buy a new one anyway.

I've read through a fair few older forum notes and a bit of googling in the past, other cars seem to give similar results if I remember right. Could be wrong.

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The intake air sensor always seem to read low, both mine were reading around -14 when first started from cold, rising to -6 degrees once the engine had warmed up when the ambient was about 4 degrees outside. It's my understanding that this isn't important as it only does anything when the intake air temperature gets very high (+55 degrees rings a bell somewhere) so as long as it is below that it won't affect anything.

I'm glad someone else has found similar readings to mine though.

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I think you're right about the Intake sensor, I've looked over a couple of GEMS cars now with the nanocom and (didn't always note the calculated load though - next time I get the chance on another car, I will look at it) it seems a common thing, mine's almost exactly the same as you describe, give of take the odd degree. Somewhere I have read or heard the same about it coming into play for high temps only/mostly, and not low and I'm almost positive it wasn't one of your older posts.

GEMS notes for morgans - "This sensor is located in the hose leading to the air cleaner.The signal is used to retard the ignition when the air temperature is above 55 degrees."

Might be that I was thinking of, GEMS by Poole or something the pdf is called.

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That's probably where I saw it as I've got that document and I've just had a look through it. Page 94 shows an example screenshot from Rovacom giving the Idle Air screen. That shows an idle speed of 698 rpm, with an airflow reading of 449 kg/hr (which must be wrongly displayed?) but a CLV of 21%. So maybe it is RAVE that is wrong?

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Yup - it does indeed! I CTRL/F searched 'Idle' earlier to check it was the right document, should have read it more. I personally suspect the RAVE figure is wrong. That kg/h figure in the Poole/GOMOG document would make some semblance of sense if it were g/minute (just under 27 kg/h I think) but who does that?

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Is there a posability that the Nano is wrong? I have found dramatically different readings using different tools. For instance LTFT currently on mine, Nano shows at -37.5% whereas another tool shows -11.7%.

Although not strictly to the point, in the BeCM module, Nano shows the Police spec selected and that the vehicle has no cruise control fitted. The RSW software shows no Police selected and a cruise is fitted which is correct for this truck.

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Not seen any odd readings from the BeCM (except for the really odd ones when it is confused) but I suspect most of the problems with fuel trim readings and the like is down to GEMS. OBD2 compliance didn't become mandatory in most of the world until 2000 and while the GEMS unit was compliant enough for the US (where it became compulsory from 1996) it isn't really compliant. That's almost certainly why some generic readers give odd readings or won't even read at all and most will tell you they will only work on cars after 2000. I strongly suspect that's also why they went with the fully OBD2 compliant Bosch Motronic, already in use on numerous other vehicles, from 1999 rather than rework the Sagem GEMS.

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Load seems to be calculated differently by different vehicles/ECU's. It's often loosely related to the maximum expectation of pinj x rpm, or max expectation for airflow. This of course means that even at full throttle if rpms are below the torque peak calculated load will be less than 100%.

Most OBD systems on most vehicles reckon calculated load is about 3% or so at warm idle. Iirc (but I forget what OBD readers I've used for this) I've seen calculated load much higher than that 3% at idle on P38s.

The calculated load figure isn't a reading I'd normally take much notice of. A manifold pressure reading at idle is a much better pointer for idle efficiency etc. The Rover V8's do seem to idle with a bit more manifold pressure than the average engine, I put this down partly to the cam and valve gear setup compromising a bit of bottom end charge trapping ability to gain a bit more top end (rpm) charge trapping ability.

On some ECUs OBD readings seem to change to a different kind of mode at idle. Maybe the 25% reading reflects the engine could only shift 4 times as much air at idle rpm if the throttle were opened? Does the figure increase by a lot if you put it in drive and turn all the electrical gear on?

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Re. Cruise Control, if it's petrol I think the default might actually be to "not fitted." It's a job that's hijacked by the specific ecu(s) is how I understand it. Before I rewired the comms port I'd get a 50/50 on whether it reported 'Police' or not on the '97, the '99 always says it is a police car, although I suspect it needs a clean/rewire itself. (This is, on the '97 HSE, both before and after the becm went wrong and had to be repaired).

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You're probably right Sam, as you say, the BeCM doesn't get involved in the cruise control so it probably doesn't matter whether it is enabled or not (I'll have to have a look at the Ascot as that has cruise fitted). The Nanocom documentation mentions that the Police setting should only be used if wiring mods have been done. Mine, being ex-plod, originally had Police enabled but that was disabled by Testbook not long after I got it when I took it into my local indie to have the trip computer enabled (after I'd fitted a stalk with the buttons on it). I found extra wiring and a couple of blocking diodes in the wiring for the tailgate which, I assume, meant that the car could be locked with the tailgate open. There's extra connectors in the lighting too so I suspect the Police setting stops bulb blown messages when they are used in conjunction with additional feeds to the lights.

I'll have another play and see what affect on the CLV switching lots of loads on has but it's bloody cold outside and threatening to snow so maybe not today.....

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So that's what police mode does - makes sense, I'd not thought about things like the tailgate - was imagining run-lock ignition and similar. Probably that's done externally to the becm tbh, if at all. On the subject of wiring, mine's got a nice puzzle lined up for when it goes wrong, a Laserline immobiliser which seems to be wired into fuel pump and ignition. The other car, the '99 has a special vehicle plate and calibrated speedo, but I'm pretty sure it was never a police car. It's always been blue for example.

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Some police forces ordered blue cars rather than white and were wrapped for the markings. They probably thought they would be easier to sell on when they were pensioned off. I know they had a number of blue Volvo estates around here as traffic cars. Either that or it was intended as an unmarked car. In my previous life we were given at talk by a Regional Crime Squad Commander and he said they always avoided using white or red cars as red stood out too much and white screamed unmarked police car. Most of the ones they used were blue.

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Someone posted on one of the Facebook groups the other day a blue P38 still in battenburg markings that was apparently a Blood Transfusion Service vehicle, intended to replace the bikes in bad weather.

Presumably in heavy traffic you don't weave through like on a bike, you just bulldoze it to one side.

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A blue P38 would blend in better than a white one. I was pulled over by a silver Focus estate that was unmarked about 10 years ago, and only realised it wasn't marked up as a police car after they'd been round, checked the tyres on my own (also Focus back then) car and were sending me off on my way again.

The calibrated speedo on the Thor always seemed odd as all evidence of any extra uses in real life are a couple of holes in the dash from (could be anything) something once being there and an extra aerial. I always assumed it never got used for its special purpose and probably had a car phone once tbh.

Blood bulldozer sounds like a band name c. late 1990's/early 2000's metalcore/nu-metal/whatever it's called at the moment.

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Getting back on track, just been out in mine so decided to check with it fully warmed up. At idle it was showing 18 Kg/Hr on the MAF and 22% CLV in Park with everything off (except the engine obviously). Put it in Neutral and it hopped up to 24% then dropped down to 22% again. Switched on Headlights, foglights and poked the Prog button on the HEVAC so that put the fans on full speed (so drawing about 10A each), the heated screen on (not that that will draw much as only bits of it work) and the heated rear screen. CLV went to and stabilised at 28% so it is definitely showing the load increasing. Looks like RAVE is wrong or they are calculating it in a different manner.

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Most metric live data readings use grams per second as the unit of measurement for airflow, 18Kg/hr equates to 5 grams per second which seems about right for a 4L engine.

Maybe if you lightly touch the throttle in D the load reading will increase, or maybe it will see you're on the throttle and load reading will change to an 'out of idle mode' (my term hehe).

For most intents and purposes P is the same as N except P brings in the parking pawl, same load on the engine anyway. But maybe passing R causes a momentary ignition timing retard that could see the load reading blip positive a little (idle is less efficient with retarded timing but could make for less harsh gear selection)?

For sure the engine isn't running at 28% of power producing or airflow/fuel using potential when it's just idling even in D with AC on and the alternator causing maximum drag. Doubt a normal calculated load reading would reach 28% even if it were a manual labouring the engine flat out at 1000rpm (e.g. high gear low speed uphill).