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DTA for Dummies

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DTA for Dummies

Post by kevhaywire on Sat Oct 25, 2008 4:35 pm

Thought I'd put up some mapping details for DTA ECUs.

I'm focussing on the S80 since it's one of the current models, but the older E48 and P8 Pro are very similar.

My aim (hopefully) is to demonstrate that there is no black art to engine mapping. If you understand your engine and it's fuelling requirements, you will have no trouble mapping it yourself.

The following maps are from my TPS v RPM map which I tuned myself on the road. 440cc injectors, 3 bar static pressure.
Many people will argue that MAP as load is the only way to map a boosted engine. It isn't. It's just another way to skin the cat. I find TPS v RPM easier to map and it can be a lot smoother too. I am working on a 3D map as load map though, and will put up details of that as and when I perfect it.

First off, assuming you successfully wired it in OK, you need to get the general engine parameters keyed in. Here is a VR6's settings for example. Standard VW 60-2 crank trigger. A lot of the 4 pots are the same, but the 1.8T uses a hall sender as opposed to a magnetic VR sensor. Most of this info is available from the net and VW white papers.

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Then you need to bash in some startup fuel. These are largely arbitary numbers and will need experimentation. The good thing with the DTA is you can run the startup map for as long as 10,000 engine turns, enabling you to fine tune the cold fuelling between that and the water temp compensation table.

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Now onto the fuel and timing. You should be able to find a base map somewhere on the net. I know there are plenty of 1.8T, 16V T and VR6 maps floating about. If not, it'll be an experimentation game. If you have a good wideband, you can't go far wrong. Always start with the low load load sites and work up.

The object of the game is to blend in a fuel map that follows your engine's torque curve. Here's my VR6 turbo one to give an example. This is one of my open loop maps and it holds 14.7 AF all day long off boost, 13.5 at 100kpa and rising to 12AF as boost increases.

Notice the pad of fuel at 500rpm (and also more timing on the timing map), this bounces the rpm back up if it falls too low when reducing the throttle abruptly.

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Timing. This isn't quite as easy to get right. You can generally 'feel' when the engine is making peak torque, and that is generally on the edge of knock. A load based dyno is the best way to map high rpm / load timing, but you can get it damned close with road mapping.
With low comp pistons, you can afford to be quite generous with timing, but this is a conservative example.

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More to come, this is just the start. The S80 has a huge feature set and very comprehensive diagnostics and data logging
Laughing


Last edited by kevhaywire on Sat Oct 25, 2008 5:17 pm; edited 1 time in total

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Re: DTA for Dummies

Post by kevhaywire on Sat Oct 25, 2008 5:04 pm

Some other settings you may find useful...

Throttle tip in. I find these work well....

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Setting throttle stops. A simple case of hitting OK at throttle rest and again at full throttle. Incidentally, DTA supports most throttle pots and nearly every sensor available....

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Or if you're using DBW, you'll need this screen too...

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Sensor Scaling. You can key in your own sensor's details, but the DTA has the common ones included already. Click the relevant radio button, or enter your own parameters.

Water....

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Air temp....

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Pressure sensor. I use a Kavlico P255 3.5 bar MAP sensor, so I had to key that in manually....

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And then of course, you have to give the engine a bit of "choke" by using the water temp map (aswell as the startup map)....

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Air temp. This can vary a lot. generally you will find with an open loop map, the longer you sit in traffic, the leaner the idle gets. Closed loop gets round that nicely. You can of course use the Boyle's law standard air compensation map, but I find that a bit extreme. This seems to work well.

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Re: DTA for Dummies

Post by kevhaywire on Sat Oct 25, 2008 5:13 pm

If you're a fan of Sequential injection, and I'd recommend it with turbos, then this is the screen you'll be having fun with. You'll need to know the cam sensor angle and injection timing of your specific application.

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Lambda control. Everyone loves a bit of wideband action. Again, the DTA has a few commonly used wideband controller settings built in. I recommend looking up PID on the net. You'll need it!

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Now this is nice, a lambda target table, or "self tune". You bash in what AFs (or lambda) you want and the ECU will alter the fuelling automatically to achieve the targets. Some playing around with the PIDs will be required unfortunately.

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Re: DTA for Dummies

Post by kevhaywire on Sat Oct 25, 2008 5:14 pm

Loads more to come, hope it's useful!

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Re: DTA for Dummies

Post by junkie on Sun Oct 26, 2008 2:55 am

Yea really good info there and you say its no black art but im now even more confused now lol.
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Re: DTA for Dummies

Post by dirtytorque on Sun Oct 26, 2008 3:08 am

I like the fact you get so much rpm resolution;i.e i think I counted 21 rpm bins.
Must give great for fine control.
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Re: DTA for Dummies

Post by nemesis360 on Sun Oct 26, 2008 5:59 am

Thanks for the info Kev, I have been reading up on mapping recently.

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Re: DTA for Dummies

Post by kevhaywire on Tue Oct 28, 2008 7:43 am

junkie wrote:Yea really good info there and you say its no black art but im now even more confused now lol.

It's really simple once you start using it mate Very Happy It's not so much the software I was demonstrating (although it might be useful), but rather the settings I've used, which people might find useful. For instance, the fuel and timing curves work VERY well and could easily be copied into Emerald, MegaSquirt etc etc.

I sometimes see people mention issues with AFs going schitt rich when they change gear or close the throttle completely. That fuel curve takes care of all that, along with the throttle transient maps.

Worth remembering that when changing gear, the air flow through the exhaust is reduced significantly and very suddenly, which can cause an 'apparent' over richness, it just depends on the speed and accuracy of your Lambda controller and closed loop map etc.

As I say, the fuel curve basically mimics the behaviour of your engine. In part throttle conditions, you have the flat planes and the gentle dip, During over run, you want no fuel at all, hence the sudden drop off at column 1 (the injector duty is too small to even open the injector valves!) and then of course the beefy hill half way across, which is of course down to Mr Turbo.

There is in addition, a pressure compensation table too, which I think I forgot to upload, which reduces and increases fuelling against manifold pressure. It's a linear table and easy to map. Think of it as an electronic version of a rising rate fuel regulator!

Hope that makes sense.

dirtytorque wrote:I like the fact you get so much rpm resolution;i.e i think I counted 21 rpm bins.
Must give great for fine control.

It's not too bad. I think for my needs it's enough, but Motec and Pectel have massive resolution Very Happy 32x32 load sites for instance.....but mapping takes twice as long Laughing

The DTA blends the cells together nicely with interpolation, which I'm sure the squirt does? So huge resolution isn't essential. You can turn that off though if you want to focus on a particular cell without any interference from it's neighbouring one.

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Re: DTA for Dummies

Post by mrbeige on Tue Oct 28, 2008 8:04 am

Yeah, MS uses interpolation from what I remember, but as you say, 32 x 32 load sites is massive and really for a street car completely unnecessary.

Very interesting reading though. Slight noob question, but what exactly is 'Tip-In'?

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Re: DTA for Dummies

Post by dirtytorque on Tue Oct 28, 2008 8:21 am

kevhaywire wrote:

It's not too bad. I think for my needs it's enough, but Motec and Pectel have massive resolution Very Happy 32x32 load sites for instance.....but mapping takes twice as long Laughing

The DTA blends the cells together nicely with interpolation, which I'm sure the squirt does? So huge resolution isn't essential. You can turn that off though if you want to focus on a particular cell without any interference from it's neighbouring one.


yeah MS interpolates between cells and so you have to take this into consideration when plugging in the numbers.And it is also why I don't like large jumps between bins,but you can use you logs to see how the ECU is filling in the gaps.
I have read that 12x12 is enough but in some areas some of the jumps are a little large for my liking.
I'd really like the extra resolution is my spark table.Just so I could really fine tune it.
I don't feel my fuel table would benifit much from extra resolution tho..
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Re: DTA for Dummies

Post by dirtytorque on Tue Oct 28, 2008 8:22 am

i rekon tip-in is analogous to MS's accel enrichment?!???

i.e accomodate extra fuel for rapid changes in throttle position to avoid temporary lean spikes.
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Re: DTA for Dummies

Post by junkie on Tue Oct 28, 2008 1:02 pm

Good Job

Off topic here but this is what i have the Haltech E6H, using the hated DOS mode and virtually eliminates the need to input numbers apparently and all done in graph form, never ever looked at it though to be honest.

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Re: DTA for Dummies

Post by junkie on Tue Oct 28, 2008 1:14 pm

And a better link

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Re: DTA for Dummies

Post by kevhaywire on Wed Oct 29, 2008 5:05 am

Nice link mate. Haltech do some good stuff. The guys who set the company up are actually ex-Bosch IIRC. So they know a thing or two Very Happy

Yep, throttle "tip in" mimics a carburettor's acceleration pump.

It's quite funny that in the 21st century, complex engine management systems still use fuelling principals pioneered duing the war!! Just goes to show how little engines have actually changed.

Part of the problem is ECUs, injectors and lambda aren't fast enough to react to the sudden change in air flow / volume, hence the tip in settings are still needed. It's very engine dependant though. Some engines don't need tip in, others do. Engines with huge throttle plates will definitley need it, where the difference in air flow between closed and 1mm open can be huge. OEs get round that with sensibly sized throttles and ramps in the throat to keep gas speed high at low rpm.

Tip in is mostly needed during cold warm up and it's not unusual to not need any tip in at all when hot, hence why all my hot tip ins are at the minimum setting.

Tip out is the pretty much the same. When you close the throttle very suddenly, you again create a condition the ECU, lambda and injectors struggle to keep up with, so with that setting you can chop a lot of fuel out momentarily, but as I mentioned before, the lambda can be a tad laggy when you suddenly take all the air away Very Happy

It's best to treat these settings as a "filler" for any flat spots and misfires during acceleration. You can also make the base map very rich where these flat spots occur, but that can cause other glitches.

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Re: DTA for Dummies

Post by dirtytorque on Wed Oct 29, 2008 7:23 am

One interesting thing with my engine is that acceleration is better with hardly any AE or or tip in.
I just use a small splash of AE now and it seems to work nicely.

One person on vortex showed me some interesting settings.
He found that his n/a car needed more AE than his boosted car.
I quized him on it and he just said"Its just what they seem to like".
He had experimented quite a bit on a dyno.

Re your tables etc are these actual numbers that you have used?
The shape of the graph is interesting.People often think that they should look linear but that is not always the case.Well in my limited experience anyway. Razz
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Re: DTA for Dummies

Post by kevhaywire on Wed Oct 29, 2008 7:39 am

Is that the same for both summer and winter? I find the tip in effect can vary with ambient temp! But you're right, some engines need very little tip in.

Yep, they are the actual numbers I used. The fuel table is a TPS v RPM map. A load base map would look a bit more linear.

Engines have their own ideas of what's right and what's wrong, the mapping is just a way to give it what it wants..... Laughing

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Re: DTA for Dummies

Post by SensibleDave on Thu Oct 30, 2008 10:02 am

Funny you should mention AE, thats the bit I struggled most with on MS. Just couldn't get it quite right for all conditions and I spent ages trying different settings and versions of software. It seemed to me that it was optimised for NA engines and just didn't work that well with FI.

Great info Kev, the effort put in shows when you show all those optimised settings. Maybe I'll get back to it some day....
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Re: DTA for Dummies

Post by kevhaywire on Fri Oct 31, 2008 2:13 am

Cheers Dave. Yeah AE is hard to get right with DIY tuning. I think it will be easier when DBW controllers filter down to the aftermarket because they have to know how fast and how much the pedal & throttle move for saftey, so you can use that data to build a much better transient map.

At the moment, you have to guess pedal speed, which can give patchy results.

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Re: DTA for Dummies

Post by mrbeige on Fri Oct 31, 2008 3:05 am

Transient fuelling is what gives the most headaches from modelling the system in the first place, to coding, and on to calibration. Getting the model right is the first place is half the battle....

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Re: DTA for Dummies

Post by kevhaywire on Sat Nov 15, 2008 10:42 am

Evening peeps....

Been playing with the mapping again, LOL! Can't leave it alone!

Did a bit of tweakage in the high rpm cruise cells to iron out a slight flatspot when punching the gas from a period of over run. This did the trick Very Happy

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DTA have now added "Lambda Target as MAP when main map is TPS" to version 45 of the soft / firmware.

It works absolutely fantastically!! Really bridges the gap between TPS ease of mapping and MAP accuracy perfectly Very Happy

It feels really crisp on the gas now, feels very much like Mass Air based fuelling now. It's a lot more responsive and holds the AFs really well.

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And for those crisp starts and accurate compensations, you can't beat a bit of Injector Dead Time / coil time against battery voltage action!

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Loving this mapping lark at the moment Very Happy

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Re: DTA for Dummies

Post by dirtytorque on Sat Nov 15, 2008 11:05 am

Do you run closed lambda control?
I only used my lambda for tuning.I could take it out now as my system doesn't use it at all,just for logging.
I seem to hit my target afr's ok now.MS uses VE tables which I think are only used on MAP systems I think..Are you using your maf to meter air ?
MS has battery voltage compensation but I have yet to tinker with it.I have left all the values at default.
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Re: DTA for Dummies

Post by kevhaywire on Mon Nov 17, 2008 7:38 am

Yep, I run full time wideband closed loop.

Can't use the MAF on most standalones unfortunately, as it's a nice way to deal with altitude and air density etc.

Yeah most people leave injector dead time at 0 for compatibility. You need to know the dead times before mapping it really.

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Re: DTA for Dummies

Post by mic_VR on Mon Nov 17, 2008 8:36 am

kevhaywire wrote:Yep, I run full time wideband closed loop.

Can't use the MAF on most standalones unfortunately, as it's a nice way to deal with altitude and air density etc.

Yeah most people leave injector dead time at 0 for compatibility. You need to know the dead times before mapping it really.

How come you can't use the MAF Kev?
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Re: DTA for Dummies

Post by dirtytorque on Mon Nov 17, 2008 1:49 pm

is your target a/f picture cut in half?
How much boost do you run in that there engine?

More than 140 kpa i'm guessing Smile

i'm Interested to see how rich your running at the top end of the scale.
I'm nosey like that.
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Re: DTA for Dummies

Post by kevhaywire on Mon Nov 24, 2008 2:30 am

mic_VR wrote:How come you can't use the MAF Kev?

The DTA doesn't support Mass Air meters mate. Not many standalones do tbh. Pectel and Motec do, but you're talking £1000s for their ECUs.

MAP sensors are linear and easy to work with. Mass air is more of a logarithmic scale and not so easy Very Happy Mass air is more popular with OEs than MAP because it measures air density rather than manifold pressure, so can work at any altitude automatically.

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