What the stock 75 TS Motronic can and cannot do. - Page 4 - Alfa Romeo Bulletin Board & Forums

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post #46 of 815 (permalink) Old 01-13-2012, 10:29 PM
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Consider the fact that during the two VVT positions, you are certainly having two entirely different ignition maps, one for very low compression ratio with an average cam LC=128* (!!) and one for higher CR with an average LC=97*. In my mind, switching between the two maps will have to follow the VVT solenoid operation; hmmm, I suppose this will complicate matters when attempting to map an aftermarket ecu, won't it?
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post #47 of 815 (permalink) Old 01-13-2012, 11:04 PM
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Why would you need two ignition maps?
If both the spark and VVT tables are rpm vs load, you'd only need one map wouldn't you, as the load points interpolate?
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post #48 of 815 (permalink) Old 01-13-2012, 11:54 PM
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Yes, but the base map depends on some basic engine constants like chamber shape and CR and this, is separated from any load signal like afm/map. Unless you have an active system always searching for the max advance value (brink of detonation) you must make allowance for CR in your base map. Visualize this: two identical load conditions, one with 8:1CR and one with 10:1CR. Wouldn't they warrant two different maps (remember, no knock sensor magic)?
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post #49 of 815 (permalink) Old 01-14-2012, 12:30 AM
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Originally Posted by Jim K. View Post
Yes, but the base map depends on some basic engine constants like chamber shape and CR and this, is separated from any load signal like afm/map. Unless you have an active system always searching for the max advance value (brink of detonation) you must make allowance for CR in your base map. Visualize this: two identical load conditions, one with 8:1CR and one with 10:1CR. Wouldn't they warrant two different maps (remember, no knock sensor magic)?
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Peak torque isn't always developed just prior to detonation. At part throttle, where the effective/dynamic compression ratio is much less than the static compression ratio (regardless of cam timing), the engine will require more ignition advance to achieve best performance (Jim, I know that you know that). But it is quite possible to advance the ignition timing even further and have the engine start to loose torque/power without encountering detonation. So this whole theory that an engine management system is constantly trying to advance the ignition timing to the point of knock and then back it off is both misleading to the average Joe and is potentially giving the ECU manufacturer's a bad reputation and technically to much credit.
Maybe/MAYBE(!!) if we used an engine with high static compression ratio and excellent breathing characteristics (and so an high dynamic compression ratio), run on pissy low octane fuel, but really, if you own a genuine achiever in the torque per litre ratio, what are you doing running on low octane fuel?
IE: A seriously octane limited engine, where in any given rev and load point, the engine could achieve better performance if the engine had a higher octane fuel and ignition mapping to get the most from it.
With a normally aspirated road car engine running on 95-98RON fuel, that isn't going to happen at less than full throttle.

I think this idea (ECU advances until knock then backs off) is a lot like the supposed principle of the bad shift characteristics in an Alfa trans axle car. The shift sux because the 'gearbox is a long way from the gear lever'. Written in a magazine once, by someone who was trying to sound like they knew what they were talking about and repeated ever since.

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Last edited by Duk; 01-14-2012 at 02:11 AM.
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post #50 of 815 (permalink) Old 01-14-2012, 01:59 AM
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The base map is a 3 dimensional table, it is tied to engine load - this I'm 99.9% sure of.
But the numbers are just starting points for the ECU's calculations, they're not the final commanded timing. There's many other environmental conditions that are applied to the calculation to get the finished product - but it has to have a number to start with.

If your CR changed by a known amount based on RPM/load, your ignition map would cater for that by having suitably scaled values in those load ranges. A 2d RPM-only map couldn't do this.
Your example doesn't fit the VVT scenario though - you can't have the same RPM and load point with VVT on and off - it's one or the other.

When the ignition table was populated by the designers, they already knew which cells would and wouldn't have VVT active.

Kind of like where the ignition map I posted last night suddenly drops the advance at load point 50 throughout the rev range - that to me looks like it expects the engine characteristics to change at that point and/or another parameter to start having a significant impact on the final calculated advance.
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post #51 of 815 (permalink) Old 01-14-2012, 07:05 AM
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I didn't say you can have both the same load and rpm with VVT on/off, that is impossible.
What I mean by 'brink of detonation' -unfortunate phrase on my part- is achieving max cylinder pressure after firing spark (which occurs somewhere ~12* ATDC) and the way this can be researched with specialized plugs like the Kistler plug/sensor. A proper ignition advance map can then be generated for various engine operating conditions, even by individuals attempting to map their engines on the brake.
Yes, all ecu ignition maps are 3D!
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post #52 of 815 (permalink) Old 01-24-2012, 12:28 PM Thread Starter
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Hey festy, are our chips about ready? I'm sure this must be an extremely brain intensive project but it sure would be nice if there was an open source program for the 75 TS ECU.

To verify, is there only one ECU model for the 75 TS? My Bosch number is 0 261 200 108 Sound about right?

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post #53 of 815 (permalink) Old 01-24-2012, 12:52 PM
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The '108 is the ECU that my ROM image came from.
I'm still working through all the code, I now know far more about the TS VVT and spark calculations than I ever really wanted to - but I'm still a while off having a DIY-tune platform ready.
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post #54 of 815 (permalink) Old 01-24-2012, 12:58 PM Thread Starter
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festy, it is great to hear that you are still at it. I was afraid that since all has been quiet on this thread you might have lost interest.

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post #55 of 815 (permalink) Old 01-30-2012, 05:27 AM
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wow, what a fantastic discussion!

I haven't as of yet, but I do plan on reading though all the linked resources, as this is an area I have always wanted to dive into. I am nearing the end of my 'Computer Science' degree (it is a VERY broad field these days) and have found this thread very inspiring.

I currently have two TS 75s at my disposal (the term loosely used!). One ECU is already chipped with the Squadra chip + fuel quality plug changed to 97RON, the other is stock. For what it is worth I have swapped both ECUs around a few times to get a feel for the different mapping, there is most definitely a notable difference! (assuming many people don't get this opportunity to switch between, as it is a soldered EPROM)

May I ask how you both (Duk, festy) became involved/interested in such tuning in Australia?

Thanks for the awesome insight.
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post #56 of 815 (permalink) Old 01-30-2012, 11:26 AM Thread Starter
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InstiTS, were there any modifications to either TS, other than the Squadra chip? And did you lose anything, like low rpm torque, poor idle, or poor gas/petrol/benzina mileage?

I gather you feel the chip is worth getting?

While I would much prefer not to have to, I would be wiling to add an additive, providing I can find one that really works. Many years ago when I lived in Pasadena (about 12 miles away) a station sold 98 octane whose cost was about double the rate of the next highest octane (92). Assuming they still sell it, I don't believe I'd be willing to drive that far to fill up.

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post #57 of 815 (permalink) Old 01-30-2012, 01:13 PM
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97RON is pretty close to what you guys call 92 octane, you shouldn't need an octane booster to use the 97RON setting.
Your 98 would be around 102RON over here - I'm not surprised it cost twice as much!

Does the 97RON plug just add ~3 degrees of advance to the ignition?

@InstiTS - My interest comes from having recently converted an alfetta to EFI using mostly GM (holden) parts (see this thread), and having a bit of experience in embedded systems programming/design helps.
When the Motronic discussion started, I was surprised at how little knowledge of the inner workings there was in the community, so thought I'd poke around a bit.
I've been doing some 8051 dissasembly recently, so was familiar enough with the processor's instruction set to make some sense of it all.
I've never seen a TS motor or ECU, so I'm really flying blind here
If you weren't on the other side of the country, I'd be grabbing my test gear and paying you a visit!
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post #58 of 815 (permalink) Old 01-31-2012, 03:05 AM
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InstiTS, were there any modifications to either TS, other than the Squadra chip? And did you lose anything, like low rpm torque, poor idle, or poor gas/petrol/benzina mileage?

I gather you feel the chip is worth getting?

While I would much prefer not to have to, I would be wiling to add an additive, providing I can find one that really works. Many years ago when I lived in Pasadena (about 12 miles away) a station sold 98 octane whose cost was about double the rate of the next highest octane (92). Assuming they still sell it, I don't believe I'd be willing to drive that far to fill up.
Both cars are running on 98RON octane (Australia).

Red TS has full CSC mild steel exhaust with oxygen sensor, cat delete, k&n pod (bad choice outside of 3am drives or Winter!). This is the car with the Squadra chipped ECU originally.

White TS is almost bone stock, only has the fuel quality plug set to 97RON (I later found out when stripping the interior. It explained why it went so hard compared to my slightly worked red car (I always thought it was the fact it had a second gear synchro that worked!). It also has a fairly growly aftermarket rear muffler which may have little bearing on performance...

I had a little run with a mate from a second gear pull and to make things fair (famously worn synchromesh). Both cars shifted into 3rd at almost the same time. Red car began pulling away in 3rd cleanly, it was more or less was side-by-side throughout second with the white car.

In regards to torque and economy with the Squadra chip. The white car starts up fine, idles smoothly (both with and without the chipped ECU) running on 97RON, open-loop setting (this car has a standard cat and an aftermarket muffler that looks like a Sprinter style muffler, haven't confirmed this). The red car is set to 95RON, closed-loop lambda control (yellow plug) and idles a little rough for a few seconds on cold start, nothing really noticiable. If the red car is changed to 97RON it runs like a pig until it sorts itself out. It will then start okay around 10 minutes after shut-off, leave any longer and it will forget it's parametres and idle rough again for a few minutes (maybe overfueling on tickover IMO, not sure what would cause this?)

Anyway, overall the chip increased economy. I recall getting approx 30-50 more km a tank, but this could be down to a change in driving distance, highway at the time, etc, but I DID NOT notice worsened economy. For performance, the chip greatly increases response throughout the rev-range, especially down low which I put down to better distributed torque curve. The car pulls more linearly in this fashion, and pretty much you don't have to hit 4k each time you want it to go, that said, I do miss the kick in the backside when it 'came on cam'.

I cannot explain the reasons why one car idles fine set to 97RON and the other is rough on cold start. They both don't use the lambda sensor at all on this setting, even at operating temp.. it wouldn't even be used when on tickover for that matter.

Anyway, I recommend the chip and playing with the fuel quality plug first and foremost with the TS, it will give you a noticable amount of power for a fairly small price, considering against exhausts/headwork. Swapping the factory ECU for the chipped ECU is nearly depressing, I can only drive one car with the chipped ECU fitted up to it... otherwise I miss it greatly!

If you do decide on the chip, maybe try 95 closed-loop/97 open-loop setting on your local fuel quality/intake/exhaust setup and see how it idles on tickover (keeping in mind catalytic converter life), either way the chip is well worth it! Hope this has been insightful.
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post #59 of 815 (permalink) Old 01-31-2012, 03:14 AM
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97RON is pretty close to what you guys call 92 octane, you shouldn't need an octane booster to use the 97RON setting.
Your 98 would be around 102RON over here - I'm not surprised it cost twice as much!

Does the 97RON plug just add ~3 degrees of advance to the ignition?

@InstiTS - My interest comes from having recently converted an alfetta to EFI using mostly GM (holden) parts (see this thread), and having a bit of experience in embedded systems programming/design helps.
When the Motronic discussion started, I was surprised at how little knowledge of the inner workings there was in the community, so thought I'd poke around a bit.
I've been doing some 8051 dissasembly recently, so was familiar enough with the processor's instruction set to make some sense of it all.
I've never seen a TS motor or ECU, so I'm really flying blind here
If you weren't on the other side of the country, I'd be grabbing my test gear and paying you a visit!
I believe the RON setting is a manual adjustment that would otherwise be handled by the CPS/knock sensor... so yes, small increments in advance would sound about right. Reference for those interested here: Craig's Place, Fuel Quality Plug (S30)

Ah yes, thought that might be the case. Embedded Systems is a whole other area, crossing over with Electrical Engineering, etc.
Thanks for the link, I will have a look through that thread tonight. Looks interesting!

Ha, yes. Was good to see a couple of other Aussies on here attempting to understand a 20 year old piece of PCB!
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post #60 of 815 (permalink) Old 01-31-2012, 04:41 AM
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so yes, small increments in advance would sound about right. Reference for those interested here: Craig's Place, Fuel Quality Plug (S30)
Thanks for that link - a few pieces of the puzzle just fell into place after reading that!

To answer my own question, no - the fuel quality switch doesn't add a fixed amount of timing, it's a seperate map.
The closed/open loop looks like it might really be a leaded/unleaded setting based on the presence of a lambda sensor, rather than specifically controlling closed loop fueling.
For instance, a 75 set to 95RON (unleaded/has lambda) uses a table starting around address 0x4337, or with 91RON setting 0x4301.
Change the setting to 97RON (leaded/no lambda) and the table starts around 0x4229, or 95RON (again leaded/no lambda) and it uses the table starting around 0x425F.
And it looks like if you select the 164 personality over the 75, there's a different set of tables called again - so there's 8 ignition tables so far...
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