Loren,

Here is a thread that speaks to your question

https://rennlist.com/forums/showthre...eferrerid=4234

 

Colin,
Thanks for the reply. I am not doubting your results for a moment but trying to understand where they are coming from.
I am toooo old and experienced to dismiss something because I dont fully understand it !

As I see it ,the key may be the use of larger injectors ( shorter ON time ) combined with a start point different to Motronic.Is this point fixed with Motec ?

Because the injection period could be better related to the motor cycle it could lead to better cylinder fuel filling and hence bhp?
Certainly the air flow in a flat 6 inlet maniflod is pretty complex so why not ?

Will you tell me the Bosch part no of the injectors you use or the flow rate at a fuel pressure ?

Ignition can be the same and a properly sized Hot film sensor will not represent an air flow restriction.

If this is the answer then it would be possible to make a Motronic DME give the same results as Motec which could save money !!


Geoff

 

MoTeC has a 3d table for injector timing which allows you to vary it based on RPM and Load and is typically set to the end of inejction, or the table defines when the injector should stop spraying fuel and the ECU determines the start. As with everything in the MoTeC software, it is completely user definable. Injector timing is only applicable to sequential injection systems. I have spent significant time with this table using several different strategies including a max piston speed model. I have found that you can affect idle quality and efficiency by varying the injector timing. This provides an engine that runs smoother, uses less fuel, and has better throttle response. Additionally, some engines with OEM camshafts like to have fuel sprayed on the back of a closed intake valve at idle which helps with atomization during low velocity running. Porsche 911 engines however, do not like this strategy. After about 40% duty cycle on average (camshaft duration will change this) you are spaying fuel on a closed intake valve and the engine operates much the same as a batch or multipoint injected engine. I have not found additional power at WOT using different injection timing strategies, however, I have found small amounts of power at cruise.

WRT injectors, ECUs that can control a peak and hold injector generally have better injector performance than ECUs using a saturated injector, particularly if you use higher fuel pressure or turbochargers where the fuel pressure increases with the amount of boost pressure. The peak and hold injectors have a better response time and can be measured using an oscilloscope and a current probe. MoTeC can control either type of injector and I always choose a peak and hold unit. I don't believe in fitting larger than necessary injectors and try to obtain a 70% peak duty cycle which seems to work well and fitting a properly balanced/blueprinted injector is key to smooth running and proper AFRs.

The other very useful table in MoTeC is the individual cylinder trim table and when tuning an engine on an engine dyno with EGT probes, you can build a 3d individual cylinder trim table that will keep the AFRs even across all cylinders at all RPMs. The common plenum manifolds from Porsche have some significant reversion at certain RPMs.

 

Geoffrey,
As ever, good stuff ! As a Motec user you must see where I am coming from.Faced with " Motec makes more power " I want to know why.
I think we agree that there is no real accuracy issue between the two systems .
Ignition timing is not an issue , i hope.
When using standard manifolds / throttle - no difference.
A Hot film unit does not represent an air flow problem.
That really only leaves fuelling.
Colin is using bigger injectors with cams to get sufficient flow rates.
Now you tell me that WOT injector strategy is not really significant.
Now I am baffled ! !
Hope this makes sense.
Geoff

 

ha ha.....I think we have been here before right....?

 

"As I see it ,the key may be the use of larger injectors ( shorter ON time ) combined with a start point different to Motronic.Is this point fixed with Motec ?"

- Red rooster -

I totally agree! This may be one of MANY factors/variables not accounted for when
making an engine mgmt system comparison. Maybe on a close analysis, one finds
that this is not the controlling variable, but that still doesn't prove that one system
is better. As I mentioned before, the smallest change in the timing maps can make for
noticeable power changes, as is the case for performance chips which push the timing
maps. So without knowing how the timing maps were setup, and other variables,
engine mgmt system comparison is unrealistic.

 

Actually, I am a MoTeC Dealer, not just a user and I understand your wanting to know why and think it has been netted down in the posts in this thread. Ideally, the 2 ECUs should be able to control the engine properly and be tuned to make the same power all things equally. However, things in reality are not equal. I don't believe that I'm contrary to what Colin has already said.

1) Motronic uses AFM in the 964 but can be converted by various companies to MAF. The AFM is a restriction to making power as Colin has stated. I believe the MAF to be more an economy/emissions load strategy rather than TPS or MAP which is what commonly would be used with MoTeC. Additionally, you are relying on someone's ability to change and properly tune the Motronics.

2) MoTeC has software with direct access to all engine control parameters. Motronics requies the use of an emulator written by someone (non BOSCH) accessing the tables that have been found. I don't pretend to understand the bits/bytes of the Motronics, so I cannot comment much here.

3) Because of the real time access to the tables, you can use a dyno to properly tune ignition timing and fuel without stopping to burn a chip. This makes a huge difference in the length of time it takes to tune an engine as well as the final output (my opinion).

4) Most of the power comes from the ability to optimize ignition timing, not from air fuel ratios. All modern Bosch injectors have good spray patterns and good response time so larger injectors and different fuel pressures will have little to do with power and more to do with injector duty cycle.

 

Loren,

With regards to my statement, I feel you have overstepped the mark.,

I do not understand the nuances of nuclear fusion, yet the sun still burns as bight as I have ever seen, had I understood how it works, would it burn less bright.

I think you owe me an apology.

Kevin.

 

"However, things in reality are not equal." - Geoffrey -

That and the other part of his post totally sums it up. Issue resolved!
Which is basically what I've been saying, i.e "It ain't easy to compare engine mgmt systems without factoring in all the variables."

So, Motronic ~= Motec ~= XYZ!

Example: Igntion tables;

Motronic, 3000 RPM, 50% load, ignition advance = 25 degrees BTDC

Motec, 3000 RPM, 50% load , ignition advance = 30 degrees BTDC

Motec HP > Motronic HP

Bottom line: All the tables can ALWAYS be altered to indicate one engine mgmt system > than the other!

In summary, the discussion a COMPLETE waste of time.

 

Geoffrey,
Thanks again. From all the comments made, it looks like I can rest easy that Motronic with the correct modifications , can make the same bhp as Motec.
That was my belief at the start but it was interesting to hear the informed inputs.
Geoff

 

Possibly, but I don't think you'll find that.

 

To give you an idea of what is possible, I teach engine management classes for EFI University which teaches people how to properly program aftermarket engine management systems. I have a Porsche 924S that we use as our practice car and it has the stock Motronics engine management system and an Autronic aftermarket engine management system and can be switched back and forth. The car is completely stock, down to the cat converter. The only difference between the two setups is that the Autronics has a MSD 6A ignition system since the ignitor is built into the Motronics ECU.

Here is a dyno comparison of the car on 87 octane fuel with the base run on Motronics and the final end of day tune by a group of 6 students who collectively tuned the engine for optimum ignition timing and fuel. I have often wondered what what happen if I had a chip programmed with the Autronic ignition timing and fuel from the Autronics and repeated the test.

 

As I understand it, in steady state (fixed rpm) running any ecu firing the same ignition timing and the same injector pulse width & timing will make the same power as another. However performance engines do not run often in steady state, they are constantly changing rpm. Therefore is it not possible in a real world dynamic state that one ecu makes a better job of anticipating where the next cylinder will want its spark/fuel for optimum performance?

As an expansion of this theory, one of my UK associates who works for a UK University has spent a lot of time working with Motec and EFI Technology ecu's (he mapped most of the UK BTCC touring cars on EFI a couple of years ago) and reckons that the new M600 Motec ecu will make more power than the M48 due to its greater processing power and has measured the gain on an engine dyno. I believe him, but I have no way of proving this, but maybe Geoffrey could shed some light if he ever gets the opportunity to do a back-to back test.

All things may look the same, but they are definitely not equal.

 

Certainly in some circumstances the newer Mx00 series ECUs will make more power, but that is in conditions where DBW and variable camshafts are in play where the older ECUs are not capable of controlling them. The crankshaft modes are identical between the two series of ECUs and the older ECUs do have a 32MHz 32bit Motorola processor which is more powerful than many other ECUs so for basic engine functions. I would guess (not verifyed) that they would produce the same power, but if someone has done the testing and says diffently, then who am I to argue with facts? Where I think the new ECU series has an advantage is with the Windows based software which adds some 3d tables where the older ECU may have a 2D table (individual cylinder trim table is an example), it has much faster logging rates (2x as fast in some cases), and better logging analysis capability. This does help get the job done faster and easier. Additonally, the new ECUs have updated lambda circuitry that utilizes newer sensors, updated more stable ignition control modules, so I suppose it is possible that they could contol the engine better.

The point that I would not want lost is that even the least powerful MoTeC ECU is very powerful and the DOS software is very stable and does a better job than many of its competitor's higher end ECUs.

I'd love to have the time to do testing as you mention, but it isn't going to happen.