Warm Up Enrichment - how much do you run at what temps?

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Fred
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Warm Up Enrichment - how much do you run at what temps?

Post by Fred »

Please post what you use, particularly if you're from a cold place and have it well tuned. Any data is good data though. I'll be unit agnostic this time because I'm the one wanting the info I should do the translation work :-)

I'm setting up the ETE default curves with the aim of producing a good result for your average engine, whatever that looks like.

I've decided on 16 temperatures from -30C to 120C evenly spaced at 10C - this should cover most anyone, including some overheating on a race track. At higher temps I've richened it up a little.

0% @ 80C
0% @ 90C
5% @ 100C
10% @ 110C
20% @ 120C

The extra fuel will help cool the engine under extreme conditions and prevent detonation, but not affect normal operation at all if the setup is running correctly.

I have no idea what to use for warm up figures though, IE, anything from -30C up to 70C

If I can get some values for the middle of that range I can extrapolate to fill the gaps. It's only a default afterall :-)

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Re: Warm Up Enrichment - how much do you run at what temps?

Post by gearhead »

Fred,

Ok, this is mine. I **know** that this is not good for 'at load' during WUE. I have it tuned so that idle is reasonable and under load is rich. When I drive on this and ambient temps are low (near freezing), it is very rich.

IMO, 2 WUEs are needed. One for idle and one for under load.

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Re: Warm Up Enrichment - how much do you run at what temps?

Post by Fred »

Thanks for the post! :-)

How about this :

One curve for the general per temp shape, and a second that scales THAT based on RPM and/or Load. This is a lot smaller than a full on 4d table :-)

I'm up for any ideas anyone has about this.

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Re: Warm Up Enrichment - how much do you run at what temps?

Post by Mops »

Some ecu's implement WUE as an extension ow PW.
so eg. at 10 deg C it's +1ms.
Then it kinda scales with load and rpm - which seems to be better behavior.... as in at hither loads (larger PW's) less wue is needed while at low loads and idle (low PW) that extra pw length is larger in terms of percentage of total PW.

If I was doing it I would try two 2d curves one in %, and one in total additional miliseconds of PW.
this "additional PW" table could be like only like 4 points.

Further to that I understand some aircooled engine have head temp sensor instead of coolant temp and these often run at 120-140 deg C in normal conditions, so it would be good if code could support that.
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Re: Warm Up Enrichment - how much do you run at what temps?

Post by Fred »

Code already has both percent and extension/fixed style stuff. Thanks for the reminder about why I did it that way, though, I'd forgotten, but you're exactly right. The fixed one just needs to be scaled from the overall fuel demand of the engine at some fixed load, though, not just micro seconds. I'll do some work on that soon.

As for air cooled, yeah, code handles either fine, I'll consult some air coolers and setup a nice default for them too.

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Re: Warm Up Enrichment - how much do you run at what temps?

Post by MotoFab »

Fred wrote:I've decided on 16 temperatures from -30C to 120C evenly spaced at 10C - this should cover most anyone, including some overheating on a race track. At higher temps I've richened it up a little.

The extra fuel will help cool the engine under extreme conditions and prevent detonation, but not affect normal operation at all if the setup is running correctly.
To cool the motor, run it further lean from the best economy ratio.

Leaning from best economy has a large affect on reducing combustion temperatures, a much larger affect than richening the ratio beyond best power.

Both have a positive affect on preignition, but the mixture range between combustion knock and lean limit of combustion is much larger. That means that controlling the mixture in the lean-of-best-economy range is easier.
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Re: Warm Up Enrichment - how much do you run at what temps?

Post by MotoFab »

Fred wrote:Warm Up Enrichment - how much do you run at what temps?
It sure would be better to have the primary focus of cold engine control be transient throttle enrichment, or XTau. With good transient throttle enrichment, warm up enrichment isn't specifically necessary. All the relevant factors are included in the XTau calculations.
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Re: Warm Up Enrichment - how much do you run at what temps?

Post by BenFenner »

Completely tuned base calibrations for many different engines are available from AEM for you to study and get a real sample size from. As for exactly how they do WUE and how many tables and factors that's going to be up to you to figure out using their PDF manual or their (very good) help feature in the newest tuner software.

I'd dig into mine right now but I can't.

Head over to their forums http://forum.aempower.com/forum/index.php and download the tuner software and any and all calibrations you want. Get the PDF manual too (which explains each and every setting and table in heavy detail). Once you understand how it does fueling for warm up you'll have dozens of different engine types at your finger tips. AEM's cold start and warm up enrichment is well known to be amazing "out of the box".
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Re: Warm Up Enrichment - how much do you run at what temps?

Post by Fred »

Ben, thanks for the tip. I'll consider taking a look at it once a few other things are tidied up and out of the way :-)

Sorry Jim, I wasn't clear. I don't want to attempt to cool the engine with this, I want to make sure it doesn't detonate. Either way, if you think you want it leaner, that is tunable with the same table too. Going richer at higher temps when the combustion chamber is hot is a definite win to prevent melted pistons from detonation. The excess fuel isn't burned but does evaporate cooling the mixture with its latent heat of vapourisation. Leaning out under load with high heat is a CERTAIN to cause permanent physical damage to the engines guts. Furthermore, there is more to cold conditions than wall wetting. The chamber itself is cold and reduces proper combustion of the mixture and surface area available to burn. Thus adding more fuel gets you a pracitcal in cylinder mixture closer to correct regardless of what your wall wetting is doing. "XTau" is a GM algorithm. Toyota have a functionally similar one that I would prefer to clone (a far more reputable car company of much much higher quality output) or not clone either and call a spade a spade. Finally, any sort of wall wetting code wont be getting written to much later, and even then, many will choose NOT to use it. This a valid choice and one that should be catered for. No need to beat the WW drum, such code will be written in due course, however even when it is, it will not mitigate the requirement for basic code like this.

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Re: Warm Up Enrichment - how much do you run at what temps?

Post by MotoFab »

Fred wrote:Sorry Jim, I wasn't clear. I don't want to attempt to cool the engine with this, I want to make sure it doesn't detonate. Either way, if you think you want it leaner, that is tunable with the same table too. Going richer at higher temps when the combustion chamber is hot is a definite win to prevent melted pistons from detonation. The excess fuel isn't burned but does evaporate cooling the mixture with its latent heat of vapourisation. Leaning out under load with high heat is a CERTAIN to cause permanent physical damage to the engines guts.
Richening the mixture above the 14.7 ratio, has a similar affect as leaning the mixture below 14.7 ratio. Best Power mixture is on the rich side of 14.7, and Best Economy is on the lean side. The motor runs much cooler at Best Economy than it does at Best Power.

Take it a step further. If you richen beyond best power, CHT goes down. And, if you lean beyond best economy, CHT also goes down, but the temperature slope is much steeper. On the lean side, you get a greater reduction in heat for the same change in mixture. The same is true for preignition/detonation.

I think people believe that lean is hot because they don't actually lean below the 14.7 ratio. There's a whole other world over there. The combustion chamber gets hot because of the presence of burning fuel, not from the temperature of the intake air.

Fred wrote:Furthermore, there is more to cold conditions than wall wetting. The chamber itself is cold and reduces proper combustion of the mixture and surface area available to burn. Thus adding more fuel gets you a pracitcal in cylinder mixture closer to correct regardless of what your wall wetting is doing.
I'm with that, you're gonna wait till later. But what the heck, since I'm thinking about it right now, here are my thoughts anyway.

The only fuel that burns is that which vaporizes before it enters the cylinder. Once the fuel is vaporized, and is at the correct fuel air ratio, it burns the same regardless of air temperature. Calculating the quantity of vaporized fuel entering the cylinder is what the XTau algorithm is all about. The full algorithm that is.

I understand the common ideology concerning Warm Up Enrichment, but a fully implemented XTau (fuel/time) algorithm does not need warm up enrichment. WUE is a crutch for poorly or incompletely implemented fuel vaporization data and calculations. The widely held idea that WUE needs two maps, an idle map and an under-load map, is evidence of the aftermarket industry's long-term lack of effective fuel vaporization calculation in their ECUs.

Through no fault of the coders, the MS code implements about 30% of the fuel vaporization algorithm. It's difficult to tune because the algorithm itself is incomplete, and also it has incomplete or erroneous data going into the formula. That isn't human error per se, it's limitations of the processor. I think that all the effort that can be done, was done, to work around the limitations. The S12X processor may not be able to do a full implementation either.
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