ECU Tuning Parameters for higher performance 3

[lurks]

I have been researching performance modifications for a 4 cylinder turbo car and had a question about tuning. When you purchase a "canned" tune to flash to your ecu what parameters are changed? My understanding of a vehicle's ecu is that it is a closed loop system that will automatically search for stoich air/fuel ratio. Is there something that I'm missing?

Thanks in advance,

lurks

 

[dgallup]

Most systems go open loop above certain speed/load conditions. Usually these areas are just mapped to manifold absolute pressure. These maps can be changed by the reflash. Canned tunes may not preform well depending on the differences between your engine and the engine the tune was developed on.

 

[NCShane]

Most systems operate in closed loop fuel control in idle, cruise and light load conditions. At high load the system works in open loop with fuel delivered based on the ECU map. An aftermarket "tune" can include an increased RPM limit, increased spark advance, increased boost level (for turbo cars) and increased fuel delivery in high load.

 

[TurboXS]

In closed loop if you change a sensor calibration such as the tube size of your MAF you will need to be able to adjust the ECU for this.

ditto for the open loop comments

 

[murpia]

If the reflash is for a turbo car, then it probably increases boost pressure through wastegate control.

That would be the major source of any increased power, compared to rev limit, spark etc.

Is your engine diesel or gasoline?

Regards, Ian

 

[lurks]

The engine in question is a turbo gasoline. What I am wanting to do is purchase the software necessary to do my own tuning. Does anyone have any suggestions for good research material for this?

Thanks in advance,

lurks

 

[1gibson]

Vehicle specific forum. Find out what hardware/software people are using for this platform, and then pick their brains.

 

[dgallup]

The tools tend to be be very ECU specific. For instance, I use TuneBoy from Australia for my Triumph motorcycle. It will also work on a couple of other brands of motorcycles but that is all. So you need to find a forum dedicated to your brand and find out what is available.

 

[DallasJ]

Cars generally have different tuning software packages if any at all. While there are generic tuning books about tuning, each car will be different in their tolerance for spark advance, A/F ratio, rev limit, boost limit, etc. based on things like port and combustion chamber design, head flow, cam profiles, compression ratio, turbo characteristics, etc.. Needless to say, there isn't any one perfect "tune"

Also be weary of tuners and don't assume they know their ass from a hole in the ground. Back in the day supposed "tooners" for the Evo would tune timing maps to have just 8* above a certain point. The 3d plot of the map was a factory curve below a certain RPM then just at flat 8* above it. No interpolation between either.

A good tuner for a mail order flash (or what ever your process is) has hundreds of maps from all the cars he's tuned on a dyno and knows what different mods do to the airflow characteristics and has a good idea of what will be safe. Then they'll send you what they believe is a fairly safe tune which will alter the fuel and timing maps and possibly boost control if available that will work but may only be 80% optimized for your particular situation.

Another thing a good tuner's flash will do is modify more than just the WOT fuel and timing profile. Anyone can figure that stuff out, its the meat in the middle where real tuner shows his skills.

If you happen to have an Evo a few of the things that also can be modified, 2-step launch control, Flat foot shifting, higher load capacities, Switching to speed density, Pressure based boost control (vs load based), Knock lights, knock and timing safety features, switchable maps, MIVEC tuning (for the 06), larger fuel/timing maps (better tuning resolution), Wideband o2 sensor reading (completely remove the narrowband), and plenty more..

Whats the car in question?

 

[lurks]

The vehicle that I am working with is a 2005 Dodge SRT-4. I would like to tune it for optimum performance on the street with the occassional trip to the track. I am a mechanical engineer by profession and an automotive enthusiast.

Thanks,

lurks

 

[mattsooty]

Lurks,

With all due respect: What makes you think that the present 'tune' (I hate that word) is so far wrong & that you could do a better job than the blokes who developed it in the first place through ad hoc adjustment???

There are so many people online that purport to be some sort of guru - when the sad reality is that they havent got a clue. In actual fact I can see a few on this thread already. My first piece of advice would be to not listen to 99% of them.

Sure I could read an article about brain surgery and throw a few words into a thread - but you wouldnt want me anywhere near your cerebellum.

This forum is infinitely better than most and there are some very knowledgeable guys on here - but the fact that most of the people that actually know what they are talking about have not bothered to comment should tell you all you need to know about this subject matter & the way it often progresses....

Since you are a mech. eng. my second piece of advice would be to go out and buy a copy of JB Heywoods 'Internal Combustion Engine Fundamentals' then read, understand, learn.....and forget all about talk of 'knock lights' etc etc

MS

 

[LionelHutz]

A typical car on the street uses a narrow band O2 and that is used to adjust the air/fuel ratio basically during part-throttle cruising or light acceleration. There are many other times the system is running open-loop. The closed loop has operation limits to which it can successfully work. So, after engine modifications, both the closed and open loop operation often needs to be tuned.

If you had an LSx engine then this would be a good place to go.

http://www.thetuningschool.com/

Not sure if their info is any help for other makes or models.

The first thing to realize is that a factory engine with a factory PCM is well tuned for the vehicle. However, there is much more to tuning than just changing the fuel and timing.

On drive-by-wire throttle cars you can sometimes change the pedal to actual throttle opening response.

On automatic cars you can change the transmission shift points and converter lock-up points.

On a car like yours with a turbo, you might be able to increase the boost and fuel a bit and extract a little extra power.

On all cars you can do things like change the electric fan set-points or other simple operational things. For example, my LS1 doesn't go to high fan speed until I believe 236 degrees and many people turn down that fan temperature setting by 10 to 20 degrees. The car does get to be very hot with the factory setting, and not just the engine but the radiated heat makes the interior hot too.

And then, beyond these personalizations to a factory car, almost any modifications done require the ECM to be adjusted for the changes.

I have tuned a few different GM engines, using both eproms and flash based computers but I have yet to do anything that was ODB2 - 1996 or newer. I have not got into tuning my LS1 yet but I am thinking about trying it next.

Now, after posting all this I will post one more thing. If you have no clue about this then you have a lot of learning to do. I spent many hours reading and looking at the software and the engine tables to figure out what was going on. Some time driving around watching the engine data helps too (but is not real safe). There used to be a DIY-EFI website with lots of good info but I think it's mostly dead now. Not sure but the Megasquirt website might have some good info on how the system works. In the end, the different make ECM's may appear to work differently but they all do basically the same thing (control the fuel and timing of an engine and sometimes the air too).

 

[DallasJ]

Wow Matt, way to sound like an OEM elitist.

OEMs need to make vehicles thatll survive 200k+ miles these days. With A/F rations deep in the 9.x:1 range and timing values extremely conservative, there is a lot of power to be had by getting rid of some of that safety factor.

And while yes, we are reducing our safety factor from over the top for variances (manufacturing, fuel, mechanical tolerances,...), we are doing it in a way we've found to be reliable and using sensors to tell us when its too much. No, my motor will not last 200k but I don't expect it to.

Whats your problem with the Knock sensor? It has proven to be a great tool for safety. When the safety factor is reduced, the knock sensor can be used to reduce timing and turbo pressure and increase A/F ratios. Its all part of the game trying to make power and the light is there just to tell you hey you're knocking, do something about it...Just like the check engine light.

I'm no master tuner, but i don't purport to be one either. Though, its not like I just read an article last Saturday on this either. Ive been tuning my cars (DSM and Evo) since 2002 and have learned quite a bit on what works in my particular situation.

Some of us aren't content with our measly 200whp car but cant afford or don't want some big block factory 505hp screamer.

 

[dgallup]

Factory "tunes" are wildly compromised toward emissions and fuel economy; reliability and noise to a lesser extent (many motorcycles have flat spots in their powerbands to pass noise regs). If those are not your priorities then definite improvements are possible even in non turbo engines. Intelligence, knowledge and testing can even improve power & throttle response without necessarily throwing out the fuel economy and reliability. It's a fact Matt, get over it.

 

[Lou Scannon]

^agree

When you "tune", your vehicle no longer conforms to factory specs and may experience unexpected failures. But there's a lot of tuning space left on the table by the OEM to be taken advantage of (with caveats) as explained by DallasJ. You take your own risk.

 

[patprimmer]

I have to agree that the factory engineer has to tune to the lowest common denominator in many regards.

I think they do an excellent job of meeting the best compromise within all their requirements.

An individual can choose his own compromises to suit his own preferences.

An individual will normally accommodate compromises he made to a greater extent than those someone else made.

An individual may well decide to compromise legal requirements where the factory engineer must comply to legal requirements.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[TrackRat]

Hmmmm.... In my actual experience with tuning forced induction engines, you pick a safe AFR at WOT and calibrate the igntion curve for MBT. Part throttle is closed loop and should be stoich with an optimal advance for the fuel octane. To be accurate and near the limit, WOT calibration should be performed under controlled conditions on an engine dyno in my experience.

 

[1gibson]

Throw one or two new parts at the car so the OEM guys don't get upset about you messing up their masterpiece for no reason.

But if it is unmodified, and a manual (no transmission tweaks like you'd do with an automatic) then you might spend more on gas doing the tuning than it's worth. Get a few new parts, then tune it.

 

[SomptingGuy]

"an OEM elitist"

OEM's are constraint jugglers. Many of those constraints are based more on political fashions than anything remotely connected with function. Ask those clever lean-burn gasoline guys from the 80's how they felt about the TWC strait-jacket.

- Steve

 

[mattsooty]

Actually we are elitists, havent you heard ;-)

We only do it because it gives us a nice warm self satisfied feeling inside and we actually try our best to make it seem more difficult than it is because it makes us feel better.

All that complexity is engineered in, for a laugh - not to please politicians or the awkward whinging b%stards we call customers or slave drivers we call managers. I just hope we can keep a cap on the 'independant experts' telling everyone how easy it really is & should be....

Of course we all engineer our cars with factors of safety to allow them to run for 1,000,000 miles, with AFRs well past the flammability limit and spark timing which is so retarded it actually increases exhaust temps (perversly requiring more enrichment). We arent trying to ensure that profit margins remain healthy are we.

And naturally, the reams of code & hours of calibrating an active knock system (whilst using incylinder pressure measurment equipement) could be easily done away with by just having some Heath Robinson lights wired up to a piezo sensor - so that you know 'hey your knocking, do something about it' (which is, incidentally, exactly the same ethos that I hear CARB & ECD had in mind for the Check Engine Light).

But then again, our calibrations are indeed 'wildly compromised' across the WHOLE speed/load range not only those low speed/load areas encountered on the FTP-75/MVEG-B drive cycles (where fuel economy & emissions are actually measured & optimised).

Of course the large amounts of run time & processing power that modern engine control systems now posses is a marketing ploy because 'intelligence, knowledge & testing' can all improve power & throttle response (which are obviously all lacking in OEM Elitists....)

What I'm trying to say is that all you really need to do is throw one or two new parts at the car (maybe a nice K&N filter, a red stripe down the side or indeed some of that Schlangeöl) and then nobody will get offended with their 'masterpiece' being messed up.

Or maybe my tongue is so firmly stuck in my cheek its starting to hurt.

Nobody is saying that it is impossible to increase some factors of an engines performance by ad hoc adjustment of the calibration parameters of its control system - but it is always at the sacrifice of some other parameter.

That objective compromise, to meet specific requirements within measurable constraints is what an engineer does. Anything else is just tinkering.

My point was only to highlight the fact that there are many many people who talk nothing but BS about things they only have a shallow understanding of.


Matt