Mazda ECU Programming differences - Gen I vs Gen II

[Caffeine Fiend]

I know that Mazda have made programming changes on the ECU between the Gen I and Gen II, but I've always been curious as to what they are.

I was doing some reading up on the Cobb website about their newly released AccessPORT that supports the Gen II, and I stumbled across a document written by the Cobb Calibration Team that mentions some of the key differences they ran into when developing the mapping for the Gen II (2010 model). It makes for an interesting read.

Link to full doc here: http://accessecu.com/support/docs/su...%20Support.pdf

The salient points seem to be around how the Cam Driven Fuel Pump (CDFP) in the Gen II is subject to higher levels of stress due to the ECU program than the Gen I.

The Mazdaspeed forums have been talking about the Gen II fuel pump also and that higher levels of caution need to be taken regarding even relatively simple mods, ie carefully monitoring fuel pressure levels particularly when under boost. This doc seems to add credence to much of what they're saying on MSF

Here are the key relevant points from the article from Cobb. It's a long(ish) read, but worthwhile:


Fuelling

Both vehicles work generally the same using a MAF sensor to measure air mass for fueling calculations. Both ECUs have higher resolution tables for Closed-Loop (CL) fueling targets, then switch to more simple RPM-based fueling tables for Wide Open Throttle (WOT) fueling targets. Calibrating the MAF sensor is the most critical thing to to on both of these vehicles in order to allow for consistent fueling under CL and Open-Loop (OL) conditions.

The Gen2 platforms appear to have very different logic when it comes to fueling during boost spool up. The Gen2 platform demonstrates a very different response when DI Fuel Pressre drops. As DI Fuel Pressure drops below ~1600psi on the Gen2 platform, the ECU will immediately increase fueling by increasing the Injector Pulse Width (IPW)...which puts increased demands on the fueling system further dropping the DI Fuel Pressure. The additional fuel is a good safety measure, but this behavior makes it so Stage1 (S1) calibrations will be calibrated to stay within the capacity of the stock Camshaft Driven Fuel Pump (CDFP) and not calibrated to their full performance potential. Yes, a S1 vehicle with a upgraded CDFP will likely be able to make more power because more boost can be safely generated and higher DI Fuel Pressure can be targeted. This also means that no Stage2 (S2) calibrations will be created using the stock CDFP unless users want to have boost limited to ~14psi.

Due to this new ECU logic...no aggressive AccessPORT OTS calibration can be run without the installation of a quality aftermarket CDFP (Camshaft Driven Fuel Pump). The S1 calibrations will perform better than stock and will likely have less reports of Knock Retard (KR), but to experience the full potential of the S1 hardware, an upgraded CDFP is recommended.

Any vehicle making over ~330 WHP will need to also have the in-tank feeder fuel pump upgraded to keep up with the aftermarket CDFP. Fuel supply is only as much as is greatest restriction point...which is the stock in-tank fuel pump at this time.

Every test vehicle that was running a quality CDFP has not exhibited this over fueling issue. The performance of the vehicle will not be at its full potential if you try to run an OTS calibration that keeps boost low enough to allow the stock CDFP to keep up with fueling demands. As mentioned above, the ECU appears to be calibrated to increase the fuel injector pulse width once it sees DI Fuel pressure drop below ~1600psi. When this occurs, the ECU will run the engine with excessive fuel hindering torque production.

As mentioned, for those that have a stock CDFP, we are going to need to release calibrations that keep the turbo boost within the fueling capacity of the stock CDFP. The car will not be slow, but it will not be accelerating at its full potential unless the engine has the hardware necessary (high quality CDFP) to support a higher performance calibration.

We understand that this may be sad news for some of you. We are not trying to force you to purchase more hardware, but the data is telling us that this is how upgrades need to proceed for the 2010 MS3.

Knock Retard (KR)

Both vehicles behave very similar with their knock feedback system. The
reports of KR for the 2010 MS3 decrement in lesser values (.001 vs .35 of the previous MS3 models). Both vehicle add fuel immediately when KR is reported. Since the decrements for KR are smaller for the Gen2 ECUs, the additional fueling given to the engine under these conditions is also less.

Ignition Advance

Both vehicles have higher resolution tables for ignition controls, although the Gen2 ECU has slightly more resolution in the ignition advance tables and the factory ignition curves are much more aggressive. These aggressive settings further stress the fueling system as they respond to Knock Retard values. The maximum ignition advance tables are much higher as well.

Variable Valve Timing (VVT)

The Gen2 VVT has very different settings for the partial throttle areas. Things to note...as with previous MS models, running with a good intake and TIH allows the turbo to spike more easily. Running a catless exhaust in addition creates severe boost spikes as well as over boost conditions. This new logic, as described above, runs the cars richer than desired when the DI Fuel Pressure drops so you can have higher boost an less KR, but also less torque production due to the excessive fuel that is injected at lower pressures.

I'd be very interested to get some feedback from people as to their thoughts/experiences. I know that a number of people who've done mods to their Gen IIs also have data logging/monitoring running. Would be very interested to get their thoughts/observations also.

Either way, seems like food for thought.

Dan

[thelegend64]

I should have kept it simple(ish) and got a Gen1! The Gen2 is proving to be a bit of a PITA! Great information though, I wonder if Allstar or CT have learnt of this?

[2XS]

I should have kept it simple(ish) and got a Gen1! The Gen2 is proving to be a bit of a PITA! Great information though, I wonder if Allstar or CT have learnt of this?

I'll buy a Gen 1 and swap you

[Caffeine Fiend]

Yeah I thought it was interesting. It also explains why the Gen II's give more of a smokescreen out the back than the Gen I's when you plant your foot.

But it does clearly also mean that there's nowhere near as much overhead in the fuel pump as there is in the Gen I, and something to be aware of when modding.


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[mech81]

INteresting read Dan. Some of it is a bit over my head though.

what do u mean by overhead? I'm a bit duh when it comes to the techy side of these things.

[Caffeine Fiend]

Hi mate.

The fuel pump on the Gen I and the Gen II are the same, but the ECU programming in the Gen II appears to push the fuel pump harder under full boost WOT than the Gen I. This means that therefore in the Gen II, there's less 'overhead' between how hard the fuel pump is working and it's maximum capability before failing.

As an example, say 100% utilization is the maximum the fuel pump can flow. At 101% the fuel pump fails. The Gen I might use up to 80% of the fuel pump capability at max boost WOT, thereby leaving a 20% overhead. The Gen II by comparison might use say 90% under the same conditions, thereby only having a 10% overhead before max fuel pump utilization. These percentages are arbitrary and are example only to highlight what I mean by 'utilisation'. I don't know what the actual percentages are.

Modding the car, depending on the mod, pushes up the utilization of the fuel pump (eg an SRI flows more air, therefore the ECU flows more fuel to maintain correct ratios between air and fuel. Because more fuel flows, the fuel pump utilization goes up).

Hence the apparent need to be more conscious of fuel pump utilization on the Gen II than on the Gen I when modding.


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[Caffeine Fiend]

Have any modded Gen II owners checked their fuel pressures to see what they're doing at full boost?

Anyone?


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[oohsean]

Interesting,

This would form part of the reason some shops can only tune series I?

Isn't mazedit only series I?

[Oldhead]

Have any modded Gen II owners checked their fuel pressures to see what they're doing at full boost?

Anyone?




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3rd and 4th gear WOT pulls 1675 to 1690 PSI. Interesting note that at 100 klm hr 6th gear cruising 1350PSI. Hope this helps.

[thelegend64]

I'll buy a Gen 1 and swap you

Haha, nice try!