Bored out air flow meter

[road-runner]

Currently got a 5AM AFM on my Chimaera 4. Am planning a ACT induction upgrade along with carbon trumpets. Was also considering upgrading the AFM. Have seen a bored out 3AM on here and needed some advice.

I know the 3AM will produce an error code on the ECU (mines catted) but it will still work though, right?

Will i need to re-map after fitting a bored out AFM or will the value it sends to the ECU still work?

[OscarT]

The 3AM and 5AM are interchangeable.

If you want your 4 litre engine bay to remain looking standard then a bored out AFM (5AM or 3AM) will give induction improvements along with a new K&N filter, ACT smooth induction hoses, bored out throttle body(72mm) in the plenum, insulator pad and improved trumpet base will give much better response and worthwhile bhp'lb.ft improvements where it matters (midrange). Your current ECU chip should cope okay with these small but worthwhile changes. As well as these induction improvements make sure that your electrical bits, e.g. coil, plugs, leads and amplifier are all in good health. Good air plus good spark equals an efficient engine.

If you are after bigger improvements in bhp then sell your 4 litre and buy a 5 litre.

OscarT

[dwgriffith]

I know the 3AM will produce an error code on the ECU (mines catted) but it will still work though, right?

Most postings would indicate that the 3am and 5 am are directly interchangeable, from what source is your comment above? The 3am is branded hitachi and the 5am is the lucas branded version.

[GreenV8S]

If you bore out the AFM this will affect the calibration and almost certainly make it read low. This would result in a lean mixture, which is a very bad idea and likely to cost you more power than you're gaining from the extra air flow. You'd need to get the map updated to compensate for this.

[OscarT]

Don't agree.

As the original fuel/air ratio settings were set high to meet emissions and the optimum fuel/air ratios for engine performance are lower then the liklihood is that the bored out AFM will improve engine performance/efficiency.

OscarT

[GreenV8S]

OscarT said:

Don't agree.

As the original fuel/air ratio settings were set high to meet emissions and the optimum fuel/air ratios for engine performance are lower then the liklihood is that the bored out AFM will improve engine performance/efficiency.

OscarT

You think they were originally run rich for emissions and leaner will be better for power? Conventional wisdom would suggest the opposite. The bored out AFM is likely to under-read, causing the engine to run lean. That's usually bad news if you're after power.

[OscarT]

Okay then, with reference to 'How to Power Tune Rover V8 Engines' by Des Hamill

Page 181 - 3AM and 5AM "are interchangeable".
Page 182 - "The standard 3AM and 5AM airflow meter has an aperture of 55mm diameter ----- this can be bored out to a maximum of 60mm in diameter." This equates to a 19% increase in airflow.
Page 188 - "the air/fuel mixture is set at 14.35:1 to keep NOx emmissions down, a richer mixture and which uses slightly more fuel than the engine actually needs." and "if NOx was not included in the emmissions control regime, Rover V8 engines could be set to run at 15.8 to 16.3:1 air/fuel mixes --"

I read that as confirming that a small increase in airflow will be acceptable, if not desirable for the Rover V8 - unless of course you're worried about NOx emmissions.

OscarT

[road-runner]

I read on a previous AFM thread that the 5AM is fitted to catted and 3AM to non-catted engines. Apparently they can be swopped without any probs but a 3AM will cause an error code (that doesn't affect running) in the ecu.

More concerned that the AFM will not send the correct value to the ecu because it won't be recalibrated to the increased bore and the fuel/air mixture will therefore not be correct. What do you lot reckon, new map required or is there sufficient tolerance in the system?

[road-runner]

Thanks OscarT, that seems like a decent arguement based on some credible facts/data.

If it is bored out to 60mm (and therefore airflow increased by 19%) then the new air/fuel ratio would be in the region of 17.07:1. Is this going to be too lean and require attention or is the loss of power due to running lean going to be more than compensated for by the increased airflow?

[OscarT]

Well if you're still not convinced by my earlier posts then why not suck it and see first before going to the expense of a full remap?

OscarT

PS 60mm is a maximum - 58mm could be the optimum - work it out.

Edited by OscarT on Sunday 2nd December 17:07

[Meatball]

Just to add to the debate - i run a straight through bored out AFM using using the original lucas wiring (aftermarket) and i can confirm it runs like a bag of shit without a re map.

[GreenV8S]

OscarT said:

Okay then, with reference to 'How to Power Tune Rover V8 Engines' by Des Hamill

Page 181 - 3AM and 5AM "are interchangeable".
Page 182 - "The standard 3AM and 5AM airflow meter has an aperture of 55mm diameter ----- this can be bored out to a maximum of 60mm in diameter." This equates to a 19% increase in airflow.
Page 188 - "the air/fuel mixture is set at 14.35:1 to keep NOx emmissions down, a richer mixture and which uses slightly more fuel than the engine actually needs." and "if NOx was not included in the emmissions control regime, Rover V8 engines could be set to run at 15.8 to 16.3:1 air/fuel mixes --"

I read that as confirming that a small increase in airflow will be acceptable, if not desirable for the Rover V8 - unless of course you're worried about NOx emmissions.

OscarT

As far as I know the standard 3AM and 5AM are interchangeable and have the same electrical properties; a given air flow will produce the same output from either.

If you increase the bore size you will get less pressure drop across the meter and hence enable more air flow. By increasing the bore size you will also change the relationship between the air flow and the output signal; the change will result in the ECU thinking there is less air going in than there actually is, so the ECU will demand less fuel than the engine actually needs.

Engines are usually set up to run at lambda 1 (roughly 14:1). You can improve the fuel economy in cruise conditions by running much leaner than that - say up to the 16:1 you quote - however this will drastically increase NOX emissions and regulations applicable to modern engines now specify that the engine MUST be run at lambda 1. This is not really relevant to the bored out meter though. It only applies to cruise conditions, and the reason for boring out the meter is to increase power output under full load conditions. Under full load the engine will be running *much* richer, usually somewhere in the range 12:1 - 13:1. This is because the extra fuel helps the engine run cooler so it is less prone to detonation and slightly increases peak power. Having the engine run richer than it needs under full load wastes fuel and costs a small amount of power but it 'safe' in that nothing nasty happens. having the engine leaner than it needs under full throttle makes it run hotter and more prone to detonation and the potential for catastrophic engine damage. The one thing you want to avoid at all costs is an engine under load being too lean. Boring out the AFM will cause the engine to run lean. Hence my advice that if you bore it out, you should compensate for this by remapping to add the extra fuel that it needs.

Or not; it isn't *my* engine that is going to be wrecked if you're wrong.

[spend]

As long as you stay under 3000rpm won't the lambdas attempt to correct & learn the fuelling?

Dave

[road-runner]

Thanks to you all for such informative contributions. It would seem that a re-map is going to be required.

Am i going to require a custom re-map or will one of TVR Power's off the shelf chips do the job? Was planning on paying them a visit after the induction and trumpet upgrade to see if i was getting everything that it's capable of. Could keep the standard AFM then chuck in the bored out one when i go and see them. Thoughts?

[That Daddy]

OscarT said:

Okay then, with reference to 'How to Power Tune Rover V8 Engines' by Des Hamill

Page 181 - 3AM and 5AM "are interchangeable".
Page 182 - "The standard 3AM and 5AM airflow meter has an aperture of 55mm diameter ----- this can be bored out to a maximum of 60mm in diameter." This equates to a 19% increase in airflow.
Page 188 - "the air/fuel mixture is set at 14.35:1 to keep NOx emmissions down, a richer mixture and which uses slightly more fuel than the engine actually needs." and "if NOx was not included in the emmissions control regime, Rover V8 engines could be set to run at 15.8 to 16.3:1 air/fuel mixes --"

I read that as confirming that a small increase in airflow will be acceptable, if not desirable for the Rover V8 - unless of course you're worried about NOx emmissions.

OscarT

Cobblers,all it will do is amplify that lousy low speed lurching that so much of us are trying to avoid,these cars dont need leanerremember that this engine/combustion design was never designed for lean burn technology,so the outcome is it wont thank you for more air less fuel unless remapped,which explains Meatballs commentthats not to say boring out dont work,its just not that simple.

[That Daddy]

OscarT said:

Okay then, with reference to 'How to Power Tune Rover V8 Engines' by Des Hamill

Page 181 - 3AM and 5AM "are interchangeable".
Page 182 - "The standard 3AM and 5AM airflow meter has an aperture of 55mm diameter ----- this can be bored out to a maximum of 60mm in diameter." This equates to a 19% increase in airflow.
Page 188 - "the air/fuel mixture is set at 14.35:1 to keep NOx emmissions down, a richer mixture and which uses slightly more fuel than the engine actually needs." and "if NOx was not included in the emmissions control regime, Rover V8 engines could be set to run at 15.8 to 16.3:1 air/fuel mixes --"

I read that as confirming that a small increase in airflow will be acceptable, if not desirable for the Rover V8 - unless of course you're worried about NOx emmissions.

OscarT

Cobblers,all it will do is amplify that lousy low speed lurching that so much of us are trying to avoid,these cars dont need leanerremember that this engine/combustion design was never designed for lean burn technology,so the outcome is it wont thank you for more air less fuel unless remapped,which explains Meatballs commentthats not to say boring out dont work,its just not that simple.

[OscarT]

In reply to Meatball and co

Of course there is such a thing as too much air, as Hamill says on Page 182 "Note that all engines must be fitted with an airflow meter which is large enough; BUT avoid using an airflow meter that is too big, as this can cause a flat spot --"

For the smaller 4.0/4.3 litre engines a bored out AFM will be as much as is needed to get the optimum output/performance.

In reply to That Daddy

Treble Cobblers to you too.

OscarT

PS If you're worried about running lean under load then fit a rising rate fuel regulator.

Edited by OscarT on Sunday 2nd December 17:53

Edited by OscarT on Sunday 2nd December 17:58

[That Daddy]

OscarT said:

In reply to Meatball and co

Of course there is such a thing as too much air, as Hamill says on Page 182 "Note that all engines must be fitted with an airflow meter which is large enough; BUT avoid using an airflow meter that is too big, as this can cause a flat spot --"

For the smaller 4.0/4.3 litre engines a bored out AFM will be as much as is needed to get the optimum output/performance.

In reply to That Daddy

Treble Cobblers to you too.

OscarT

Edited by OscarT on Sunday 2nd December 17:53

Cobblers wasent aimed at you but that article you referred tobut thanks anyways

[Meatball]

That Daddy said:

OscarT said:

Okay then, with reference to 'How to Power Tune Rover V8 Engines' by Des Hamill

Page 181 - 3AM and 5AM "are interchangeable".
Page 182 - "The standard 3AM and 5AM airflow meter has an aperture of 55mm diameter ----- this can be bored out to a maximum of 60mm in diameter." This equates to a 19% increase in airflow.
Page 188 - "the air/fuel mixture is set at 14.35:1 to keep NOx emmissions down, a richer mixture and which uses slightly more fuel than the engine actually needs." and "if NOx was not included in the emmissions control regime, Rover V8 engines could be set to run at 15.8 to 16.3:1 air/fuel mixes --"

I read that as confirming that a small increase in airflow will be acceptable, if not desirable for the Rover V8 - unless of course you're worried about NOx emmissions.

OscarT

Cobblers,all it will do is amplify that lousy low speed lurching that so much of us are trying to avoid,these cars dont need leanerremember that this engine/combustion design was never designed for lean burn technology,so the outcome is it wont thank you for more air less fuel unless remapped,which explains Meatballs commentthats not to say boring out dont work,its just not that simple.

As That daddy says twice boring out does work i picked up around 8 bhp and the same in torque after a re map on my 450.I also installed an adjustable rising rate fuel regulator to increase the fueling which helped with the top end fueling.

[GreenV8S]

OscarT said:

In reply to Meatball and co

Of course there is such a thing as too much air, as Hamill says on Page 182 "Note that all engines must be fitted with an airflow meter which is large enough; BUT avoid using an airflow meter that is too big, as this can cause a flat spot --"

For the smaller 4.0/4.3 litre engines a bored out AFM will be as much as is needed to get the optimum output/performance.

Make sure you're quoting in context.

The problem with having too big an AFM is that the AFM becomes relatively insensitive at low air flow levels and it gets difficult to control the AFR accurately. That issue is not a problem with the map, it is a problem inherent in the sensor.

What we're talking about here though is whether changing the AFM will affect the fuelling sufficiently to require a remap. Even if the sensor is an appropriate size for the engine, changing the flow/signal characteristics will result in the wrong fuelling and you will need to compensate for this. IMO the most appropriate way to compensate is to remap it.