[fsparv]

And by we I mean you I know next to nothing.

Infinity Stand-Alone Programmable Engine Management System - Wideband O2 UEGO, Water/Methanol, Stand Alone Engine Management, Piggyback F/IC, Tru Boost Controller, Gauges, Automotive Performance Electronics

They have some videos and seem all excited about tuning via Volumetric Efficiency...

I don't see many other units that say they do that, there is an Accel/DFI one,

Accel-DFI Thruster EFI Engine Management System - Free Shipping on All Orders @ JEGS

and these folks who seem very drag race oriented...

Platinum Sprint 500 | Haltech - Engine Management Systems

So is this a new thing, or just a new thing for AEM? Is it a good thing, just another way of doing it or, mere marketing fluff? Certainly their video makes it *sound* good, but it also seems just a little bit like moving the work from one part of tuning to another.

 

[holmz]

VE is common on all modern EFI units.

 

[me73]

VE is common on all modern EFI units.

+1 Any tuner will be proficient with a manifold pressure based system. These systems have been around for decades. I've tuned my Rx-7 with a Haltech, it's kinda fun.

 

[holmz]

+1 Any tuner will be proficient with a manifold pressure based system. These systems have been around for decades. I've tuned my Rx-7 with a Haltech, it's kinda fun.

Right...
But it doesn't mean that MAF or Alpha-N are not also good for certain circumstances, just that the VE is conceptually easy and makes sense.

 

[Westrock]

The Fastworks system for our cars (and I guess the stock Lotus setup by extension) is based on VE x Load x RPM. It took a little conceptual change for me since the last tuning system I used was based on the more primitive RPM vs Throttle Position.

 

[fsparv]

Ok, cool. Seems the conclusion is that it's mostly marketing then aside from the nice colorful graphics which probably do help you spot oops-edits, things way out of whack and big picture differences in what's happened when you change a header or cam or whatnot.

 

[me73]

The Fastworks system for our cars (and I guess the stock Lotus setup by extension) is based on VE x Load x RPM. It took a little conceptual change for me since the last tuning system I used was based on the more primitive RPM vs Throttle Position.

Most non-turbo systems from the manufacturer including the one in the Elise are speed density based. Meaning that they directly measure airflow through a mass flow sensor (hot wire annomometer or calibrated flapper) and meter fuel based on it's reading and a few other sensors. A VE table isn't needed in these types of systems, the airflow IS the volumetric intake, and they are more tolerant of modifications without retuning.

 

[turbophil]

Most non-turbo systems from the manufacturer including the one in the Elise are speed density based. Meaning that they directly measure airflow through a mass flow sensor (hot wire annomometer or calibrated flapper) and meter fuel based on it's reading and a few other sensors. A VE table isn't needed in these types of systems, the airflow IS the volumetric intake, and they are more tolerant of modifications without retuning.

That's not correct. VE tables are not flat (or constant) in MAF systems as you're implying. There are several reasons for this...

Additionaly, the stock system is not speed density. Speed density (S/D) systems are without a doubt the default basis for air/fuel metering that aftermarket systems use and was used by OEMs a lot early on. I think Honda was about the last S/D holdout and used S/D into the early 2000s, as I recall. Speed-Density is used to describe an EMS (engine mgmt system) that uses engine *speed* and air *density* as a basis for air/fuel metering. Air density is measured with a MAP (manifold air pressure) sensor and an IAT (air temp sensor). Pressure and temperature will provide the density. Some, if not most, speed density systems use MAP and RPM to reference a table where injection pulse-width (PW) is referenced. Some more advanced S/D systems might use a VE reference table to calculate PW rather than a simple PW table like mentioned prior.

Anymore, most, if not all, OEM engine controllers use air mass metering (MAF- Mass Air Flow) and some use a combination MAF and S/D (such as forced induction applications where torque reduction safeties are applied with over boost, etc). MAf systems use VE where the VE is input into a table and references engine speed and calculated engine load to then calculate fuel with a host of other inputs to modify the value. This is the "standard" for OEMs anymore (including all Toyota engined Lotuses).

The lotus ECU uses MAF exclusively, not speed density (the Exige S line has a MAP sensor but it is not used in anyway in the Lotus ECU calibration). MAF has advantages to S/D in that it's much more accurate in metering air consumption particularly in running areas where manifold vacuum is low. MAF can also more friendly to modifications that are downstream of the MAF sensor, which is a good thing for us. In general, if the VE reference table and load are not maxed out, and the table is calibrated with additional headroom for power, then bolt on modifcations like an exhaust can be ran without remapping. As an example, the stock Exige S tables will max out once the TB is opened 100% and this is a bad thing, as the EMS is blind in this situation. We redesign the tables and calculation method to prevent this and enables our tunes to be friendly to bolt on mods and even more boost (within reason) without additional tuning.

As great as MAF systems are, they have a couple drawbacks. MAF is arguably less friendly to the aftermarket, as changes to the intake track in the plumbing of the MAF sensor can have adverse effects on air metering that can throw the whole system off. It's much harder for the DIYer or speedshop to correctly design an intake that is MAF friendly and then tune the MAF curve in the ECU. We've seen this in the Lotus community going all the way back to the first CAI for the Elise where good intentions to remove "restrictions" had unintended consequences when there was a lack of proper respect for the MAF sensor and the plumbing around it (this still happens today with some systems). Secondly, the MAF housing and sensor can be restrictive in some applications. You're going to have a hard time making a 1,000whp if you have draw air through a 3 inch MAF for instance . This isn't a problem for us, as a 3 inch inlet pipe will make provide for more airflow than our little motors need. This example of a MAF diameter restriction can be overcome, but it gets complicated to tune (not impossible though) when you depart from the OEM's work in this area. That's why aftermarket sticks with S/D, which is comparatively simple compared to MAF.

Bottom line, as mentioned by others, using VE is nothing new, and especially not new to OEM controllers. There's no doubt that modern OEM engine controllers (including the Lotus ECU) have much, much, much more advanced programming than even the best standalones, albeit less configurable by the end user since the OE controller and programming was designed for a specific engine or family of engines not the entire universe of engines... It's really hard to beat the OE controller provided that you have a well hacked editor to control it:up:

-Phil

 

[ageshelin]

re: Engine management systems

It is not marketing hype. You do not see any MAF's on F1 cars!

It all has to do with how well one can tune a given system and how fast it reacts to change in engine speed and load.

MAF is too slow, too fragile and is a restriction in the intake air stream. It is cheap to make and takes the whole measurement all at once (kind of like a carburator), so makes a very good street car OEM system. The same goes for running a car on an O2 sensor (most street cars do 90% of the time!).

The best is speed-density i.e using the MAP, IAT, RPM and TPS. The ECU can make all the calculations and meter fuel more precisely. A really good way to tune a mass-density is with VE and desired AFR, since they change the least over a wide RPM range. Most mass-density systems let you put in the injector pulse width for a given RPM and MAP, so evry time you tune the car, everything has to change....

Anton

Ok, cool. Seems the conclusion is that it's mostly marketing then aside from the nice colorful graphics which probably do help you spot oops-edits, things way out of whack and big picture differences in what's happened when you change a header or cam or whatnot.

 

[me73]

That's not correct. VE tables are not flat (or constant) in MAF systems as you're implying. There are several reasons for this...


-Phil

I believe all that I've said is correct except I mistakenly called mass air density systems "speed density". Thanks for the correction.

 

[holmz]

It is not marketing hype. You do not see any MAF's on F1 cars!
...

What primitive system do they use?

 

[turbophil]

I believe all that I've said is correct except I mistakenly called mass air density systems "speed density". Thanks for the correction.

No prob, but again, MAF systems do not have flat VE tables as you're implying. They are relatively flat unlike a PW table on a S/D map, but they are certainly not flat.

Won't see MAF on an F1 motor. I would guess that's largely due to the restrictions of how the intake would need to be designed. Comparing to F1 probably isn't too productive anyway. Spec ECU and a whole different world of operation.

S/D can certainly be made to have fine driving performance in part throttle applications. There are plenty of Lotus owners running EFI, some Motec, and SSC's system, AEM, etc which are generally S/D (a few are alpha N), and they're decent "around town." That said, the OE ECU running MAF has much better idle, starting, and drivability in varying conditions (temperature altitude, etc) than any of the S/D systems I've seen or heard of including EFI, AEM, Motec 400, and SSC's adaptronic. Most standalones will need -some- degree of fiddling frequently to remain perfect for the given day and conditions. They simply don't have the programming architecture to deal with the vast variables of an every day driver. They are easy to tweak to be made to work with the particular day, etc however.... but then again, the stock ECU is pretty easy to tweak anymore as well...

There are pros and cons to each...

Phil

 

[me73]

No prob, but again, MAF systems do not have flat VE tables as you're implying. They are relatively flat unlike a PW table on a S/D map, but they are certainly not flat.

Phil

In a MAF controlled system, there is no correction for volumetric efficiency. The measurement of the airflow taken into the engine is the direct measurement of the volumetric efficiency, hence not map for ve.

The corrections you are referring to are not related to volumetric efficiency per se as much as they are related to combustion efficiency, combustion speed, load, temperature and other operating parameters where there are benefits or requirements to alteration in fuel ratio and spark timing.

So again, nothing I said was inaccurate. Thanks.

 

[turbophil]

In a MAF controlled system, there is no correction for volumetric efficiency. The measurement of the airflow taken into the engine is the direct measurement of the volumetric efficiency, hence not map for ve.

The corrections you are referring to are not related to volumetric efficiency per se as much as they are related to combustion efficiency, combustion speed, load, temperature and other operating parameters where there are benefits or requirements to alteration in fuel ratio and spark timing.

So again, nothing I said was inaccurate. Thanks.

Let's break this down

You said, "A VE table isn't needed in these types of systems"

I said, "That's not correct. VE tables are not flat (or constant) in MAF systems as you're implying. There are several reasons for this..."

You said, "The corrections you are referring to are not related to volumetric efficiency per se as much as they are related to combustion efficiency, combustion speed, load, temperature and other operating parameters where there are benefits or requirements to alteration in fuel ratio and spark timing."

And then you said, "So again, nothing I said was inaccurate."

Now I say: Your original statement is still not correct. A VE table is needed and is present in all MAF based programming that I've seen to dial in the fueling. PErhaps you're assuming that each unit of air the MAF measures equates to a fixed amount of fuel as it relates to the target AFR, load, and RPM. The motor doesn't work that way. Blowby, valve overlap, among others prevent this utopian thought process from being the case. That's like an engineering question that starts with "In a vacuum,..... " You can call the VE table something other than a VE table if you like, a "catch all table" if you prefer, but the entire tuning community, including the OEMs, call this table the VE table. As far as I know, all ECU software that uses a VE map has a target AFR map that the programmer uses to dial in the desired AFR at X RPM and Y load, not the VE map. In the aftermarket, the VE map is dialed in on a load sustaining engine or chassis dyno to achieve the target AFR at those various load/rpm sites. This leaves you with the fueling equation largely being based on VE, target AFR, injector size (if that scaler is present otherwise a constant), TPS movement, temperature, baro pressure, voltage (inj latency), and RPM to calculate the injector PW for a given event.

Sorry, still don't see how you are accurate.about MAF based systems not needing a VE table-- at least in the conventional contexts of the term "VE table."

What MAF based EMS are you working with that doesn't have a VE table?


-Phil

 

[ageshelin]

re: F1 ECU

I believe that most race cars and F1 use speed density. Motec is the premier supplier to a lot of teams. Pectel, Bosch and a few others are in the market. All will run just about any control system, but speed-density is the preferred method.

Anton

What primitive system do they use?

 

[ageshelin]

Engine tuning

To put things in perspective:

If one had an ideal engiene the amount of air it would injest, normalized to 80F at 14.5psi is:

RPM/2 for 4-stroke * Displacement * Manifold prssure/14.5 * 80F/Manifold temperature * (normalized air density at 80F and 14.5psi)

Note: we need to change F to absolute scale i.e. Rankine

This is true if the engien was ideal, but most are not, we have poor breathing due to cam timing, intake manifold design, turbo blow-thorough, etc, etc. This is all hard to calculate compared to above, hence we throw in a fudge factor called Volumetric Efficeincy (VE) which is how well we are doing versus ideal. The final air formula becomes:

Real Air Flow (at RPM and MAP and IAT) = Ideal Flow (at RPM and MAP and IAT) * VE (At RPM and MAP and IAT)

Then we need to determine the fuel requirement. This is alos not constant as load confitions change, then we have the AFR fudge factor:

Ideal Fuel Flow = Ideal Air Flow /14.7, where 14.7 is ideal AFR for gasoline

Real Fuel Flow = Real Air Flow / Real AFR

We can now understand the tuning algorithms better:

1. One can input observed VE and desired AFR into an RPMxMAP table and have the ECU run all the calc for injector timing. This will require knowledge of the injector type, its flow characteristics and Fuel Pressure. However, all of that can be dupmed into VE or AFR fudge factors,m anyway...

2. One can input some injector pulse width directly into RPMxMAP table. This is what most ECU's do. This has the effect of applying Real Flow and AFR factors together all at once. The ECU needs to extrapolate between data points to calculate for actual conditions. Since, only one fudge factor is used some precision is lost....

3. One can observe that a MAF will give the Real Flow Measurement. Then ECU needs to adjust for Real AFR and some other things (blow-by, etc) that may happen that MAF cannot measure. Hence, Phil refers to a RPMxMAP mapping of AFR'ish fudge factors for MAF that is present in this type of system. MAF systems are simple to construct in this sense. Especially if O2 sensor is used for most cruising and idling to fine-tune the fuel delivery even more.

4. For natuarally aspirated motor, MAP and IAT will depend on the RPM and throttle opening (TPS) for a given ambient temperature. This makes for a very simple system that relies on TPS and RPM, only. It is called Alpha-N. It requires ambient and water temperature adjustment. Both of these change very slowly. TPS and RPM are very easy to measure very quickly. Hence, it makes for a very quick and precise system. It is ideal for drag racing.

1 and 2 are called speed-density, since the calculation is based on engine speed and air density (= MAP adjustment * IAT adjustment).

3 is MAF.

4 is Alpha-N. N stands for RPM or engine speed and Alpha is the TPS-based factor.

All of the above, have an electronic accelerator pump i.e. fuel enrichment when the throttle is opened quickly.

A carburator is an 'analog' version of MAF. It measures air-flow by measuring pressure drop across a venturi. The more air is flowing, the greater the pressure drop i.e. Bernoulli law.

None of this is very hard. What is difficult is the careful mapping of the engine to discover optimum 'fudge factors' (VE and AFR) without blowing it up.

The aim is to have a system that can react quickly and precisely to changing engine parameters i.e. RPM, pressure and load. Hence, it depends on how fast the sensors can measure those changes. MAP and RPM measure ment is pretty fast. MAF and IAT is not so fast. TPS is just a pot, so it is instantaneous.

Anton

 

[holmz]

I believe that most race cars and F1 use speed density. Motec is the premier supplier to a lot of teams. Pectel, Bosch and a few others are in the market. All will run just about any control system, but speed-density is the preferred method.

Anton

Believe or know F1 uses Speed density?

Is MoTeC is supplier to any F1 team?
I think the Aussie V8 supercars use MoTeC, but I thought NASCAR used a different supplier? (which made little sense as the V8 super cars seemed to be similar enough, but well ahead in terms of technology???)

---
AFR and VE are not fudge factors.
VE is the volumetric efficiency.

If you know the volume of the air (in grams), and you know the AFR that is desired then you can calculate the amount of fuel required to get the AFR.
And that is exactly what speed density does.

One can measure the VE (maybe by using a MAF), or emprically find it.
In the end it really doesn't matter as one ends up with the amount of fuel being injected to get to the AFR that is desired. Just with VE it is pretty apparent when the numbers are around 100% without boost that there is probably some optimism happening.

 

[me73]

3. One can observe that a MAF will give the Real Flow Measurement. Then ECU needs to adjust for Real AFR and some other things (blow-by, etc) that may happen that MAF cannot measure. Hence, Phil refers to a RPMxMAP mapping of AFR'ish fudge factors for MAF that is present in this type of system. MAF systems are simple to construct in this sense. Especially if O2 sensor is used for most cruising and idling to fine-tune the fuel delivery even more.
Anton

VE is the volumetric efficiency.

If you know the volume of the air (in grams), and you know the AFR that is desired then you can calculate the amount of fuel required to get the AFR.
And that is exactly what speed density does.

One can measure the VE (maybe by using a MAF), or emprically find it.
In the end it really doesn't matter as one ends up with the amount of fuel being injected to get to the AFR that is desired. Just with VE it is pretty apparent when the numbers are around 100% without boost that there is probably some optimism happening.

Exactly, thank you.

 

[turbophil]

Exactly, thank you.

I understand what you're getting at from a physics standpoint, but you're still incorrect in your statement. You said a VE table is not needed. I hope you understand that you're incorrect in this statement. As I mentioned in my last, you can call it a "catch all table" or as Anton calls it a "fudge factor", but that table, as it is titled, is required if you expect the target AFR table to have any meaningful values and the entire tuning industry labels it as such...

In other words, you wouldn't tell a tuner that there is no VE table in his software, when there clearly is one. You can argue the accuracy of the name all day long with some merit, but the terminology is what it is, and that's how the tuning community has come to define that table. Not much different than calling an air to water intercooler a "charge cooler", or how we refer to turbocharging as something real when it's actually a made up name for a form of supercharging. We still call an exhaust driven supercharger a turbocharger (not even turbosupercharger), even though it's actually a supercharger....

Phil

 

[holmz]

I understand what you're getting at from a physics standpoint, but you're still incorrect in your statement. You said a VE table is not needed. I hope you understand that you're incorrect in this statement. As I mentioned in my last, you can call it a "catch all table" or as Anton calls it a "fudge factor", but that table, as it is titled, is required if you expect the target AFR table to have any meaningful values and the entire tuning industry labels it as such...

In other words, you wouldn't tell a tuner that there is no VE table in his software, when there clearly is one.
...
Phil

I use the primitive Alpha-N, so the fuel table is in % of a full squirt.
But I can still have an AFR target table with it, just that the Alpha-N has no physical meaning in the physics of the engine sense... And I can still have compensations for baro, temp and humidity to correct for the air density, just that I would be using throttle position rather than MAP for the table and therefore Alpha-N versus Speed-density.

But yes for the whole rest of the world (other 99) who are using VE, it is like Phil says.


The way it may seem like a fudge factor if one make some assumptions on blowby, overscavenging, or incomplete combustion being required in the VE table.
Particularly with overscavenging is VE the amount of air that the engine pumps through it measured with a MAF? or the amount of air that that the engine gets into the cylinder when the valves shut?

Those "fudge factors" do not need to be in the VE table.
Those fudge factors, need to be in the AFR table - which are really not fudge factors as it is the AFR that is desired based on how the engine needs to run for power, or emissions, or economy, and not the AFR inside combustion chamber.

But many people actually call "the lambda" "the AFR" and believe it is correct.
There is a lesser number that believe that the measured lambda (AFR) is NOT reflecting exactly what is happening inside the combustion chamber, and they generally believe it to be more of a guide line.

If one is using Speed Density then VE is used and AFR.
VE is the air that the engine pumps, and one way to measure it is with a portable MAF somewhere even if a MAF is not used in the final set of sensors.

The AFR is trickier but most people set "to a conservative rich value", which can make 99% of people happy, but then it has little bearing on what the engine likes, wants, or needs.

The one person who we can believe may have a competent grasp on this is the OP whose said "he knows next to nothing". But that next to nothing might be like AFR versus Lambda - maybe exactly indicative of what is inside, or it may be over estimated or under estimated.