I have an SMT-6 coming my way from an ebay purchase. Will be used to tune out a modified BMW 535.

Seller says the unit is missing the CD which doesn't seem to be too big of deal as you can download all but one manual from the Perfect Power site.

The only manual you can't download is the "Developer Manual" but Perfect Power will ship you one on CD for $6.

Here's the question - what's in the developer manual? Does anyone have the disk and are you familiar working this this unit? I'm guessing I'll need this but I would like to confirm...

TIA!

Jeff

 

do a search you will find the diagram. Watch out with the smt site because the diagram on there site is not complete.

 

Diagram? What diagram? I'm asking about the developer's manual.

Are you referring to the installation diagram - is it wrong for the BMW 535?

Did you even read my post - or yours?

 

It is probably wrong for the 535.
It has been wrong for other Bosch cars I have used it on.
For example - it is definitely wrong for 944.
You must have an in-depth knowledge of the BMW DME before you get good results.
And I don't know which 535 you have, but the SMT is not friendly to vane-meter
It will work, but you are going to chase your tail for a long time.

 

there we go ST said it better than me.

 

Jeff N, The SMT will work on the 535, however you must know how to wire it and configure it correctly. The Developer manual gives you generic information, which you must correlate/map back to your 535.

There are some limitations to what you can/should do. Depending on your application and the levels of mods, the SMT may not be the correct tool. As an example, if you have a turbo application and your VAF/AFM is maxed out, the PiggyBack will not help you much.

Things you will need:
- 535 Wiring Diagram & DME pin configuration
- O-Scope to figure out the various triggering patterns used on the car.

Not knowing which 535 you have, you might need to perform a certain tricks to get the DME to respond correctly. Early E28, E34 535 are not too bad! The tricks are not documented anywhere!

 

Thanks guys...I'm fully expecting to have to sort this out. Just curious what's in the developer's book and if I need it to get things running.

The SMT folks provided me a wiring diagram at my request - sounds like I should double check that, eh? I don't think there's too much chance to mess up the installation as the car only has a 3 position TPS and a single coil. It's BMW Motronic 1.3 which I believe is similar to the early Porsche units.

No boost on this car, just a 3mm overbore, headwork, cam and exhaust work.

Car has a Pro-M racing (out of business now as many of you know) MAF conversion kit. Ford MAF unit. I have a functioning linear translation table from the Pro-M system that I can use to start the MAF input / output voltage mapping.

I'm hoping to use the dual axis analog table in the SMT to better tune the MAF voltages over the current chip's mapping to tighten up the the fuel ratios. It's currently difficult with the limited configuration the Pro-M system provides to get the fuel dialed in at different RPM/load combinations. Running an LC1 wide band so I visibility to the A/F mixture. I plan to do the tuning with the car running open loop so I don't have to fight the motronic's closed loop feature.

Once I get the fuel dialed in, I need to tinker a bit with the advance as the car makes poor power off cam and gets pretty poor mileage to boot. I suspect that a little advance in this area should really help the driveablity of the car. Pretty well documented that cars with hotter cams need more advance off cam.

Suspect there are just a few tuning tricks with the SMT. Wouldn't ask for any proprietary information but if y'all have any recommendations or considerations, would certainly appreciate them.

John - helpful if you can elaborate what triggers are you referring to? For my application, I can think of several; some of which I know some that I don't.

- idle, mid throttle, WOT; tiggers open + closed loop as well as what map is used.
- open and closed loop; triggers fueling corrections or lackthereof.
- cold run circuit; trigger known but not really the complete impact; pretty sure it's more fueling, more advance. Not too worried about this as it's just a transient condition.
- AIT; problematic of course with the MAF conversion as the motronic incorrectly adjusts for temp correction as it's expecting the vane meter, not the MAF. Currently have the AIT signal forced to a constant with a resistor and this seems to work better. I know this signal skews fuel and advance but don't have the actual skew mapping.
- Airflow voltage; controls lookup on fuel and timing tables before adjustments for AIT, cold run, TPS, lamdba etc are applied. Must be less than 5 volts. This and the CPS signals seem like the two biggees.
- CPS signal; supports my crank trigger (i believe it's a missing tooth but I would have to check); not sure what more I need in this area.

Not really worried about things like the Air Con trigger, etc.

Jeff

 

PS - I'd never try to sort something like this out on a 951. Way too much that could go wrong. To quote Mr. Gump. "I may be dumb but I'm not stupid!".

 

Jeff, Using the PB to translate the MAF signal to look like a AFM signal is not a good idea. After lots of work, you will get close on the AFR, however your ignition timing at Part Throttle will be off (this depends greatly on the MAF calibration you are using). The best approach is to get a True MAF chip where it has been converted to Air Mass, then use the PB for fine tuning.

Double check the wiring diagram before cutting and splicing the wires. Some of the diagrams are not accurate.

Good luck.

 

Yeah...except no one is doing that for the BMW M30 motor. Mark D'Sylva in Canada is tinkering with a possible solution but it's not baked yet. Miller Motorsports claims to have one but my friend who's running one isn't thrilled with it. They seem to have the tables set in the chip but the execution when measured by A/F ratios seems to be lacking.

I could revert to the vane meter but as several of you have mentioned - that's not recommended.

I'm curious why the timing would be off at part throttle. Assuming you tune AF for stoich at mid throttle - which is where the factory motronic ties to push the mixture - why would the timing be off? Isn't timing a lookup of the AFM voltage and the CPS rate with some adjustments applied by the AIT, Temp and other tables? I could very much see it being off if I was to tune for power - say ~ 12.6 or something and run the car open loop. That would push the AF voltage off factory spec and the associated timing lookup would be wrong.

I'm sure my understanding is muddled of course...only hacking away through some basic reading and trial and error. No one seems to want to publish much in this area...feels like the land of secret handshakes and dark secrets.

So...I go it alone... (pained smile). What good is the SMT if it can't tackle some problems like this?

 

Jeff N, We have the BMW MAF conversion already done. We just didn't go after this market yet. We have a E30 M3 Turbo with our MAF conversion running in the NE..

In response to your timing question. When you alter the MAF signal to look like the AFM signal, the DME will be reading whatever you tell it. The DME uses the MAF/VAF signal to calculate load. The load value is used to calculate the ignition timing. Since the DME is seeing the modifed MAF/VAF signal, it will not calculate the actual load value, and it will calculate the ign value based on what you told it not based on actual. Of course, not many people tell you this fact!

 

John...thanks for the insight. I have no quibble with what you folks have done to setup the MAF right. My mistake - haha - is to try to mod a car that no one wants to make aftermarket parts for. Lots of E30 parts for the M20 and S14 engines. Not so many for the M30 motor. Are you planning to make your MAF kit available for the E28 and E34 M30 folk?

I think I basically understand what you're saying about the input voltage. The problem as I see it is akin to trying to squeeze a wet pumpkin seed - something unexpected always squeezes out from one side or the other.

Here's the theory that I'm working under. First, I completely understand as you adjust in input voltage to the DME you effect both the injector pulse AND the timing. And, while you may get one correct you likely only do it at the expense of the other. And, you have problems with the MAF flow response curve not matching the vane response curve which of course is what is mapped in the chip fuel curve..and timing map. Sooooo...by my read, any MAF conversion is immediately hindered unless by some act of god you can get the air volume output signal generated by the MAF to exactly equal the one put out by the vane. Certainly, the pro-m conversion is a very very blunt tool to meet that criteria.

I'm hoping that the SMT will be a less blunt tool. I believe this is how.

1 - I think I will get much better control over my input voltage as I now get a 2d map. I can now tailor my input voltage based on engine RPM and flow to drive the right A/F mixture. The 2d map gives me better ability to lay a "MAF map" over the "chip map" that is better than what I have now. I tune open loop and tune for near stoich mixture. If I want to get fancy, I suppose I could also vary the voltage to have a lean mixture at low RPMs/volumes and a richer mixture at higher RPMs/air volumes. I have none of this now.

2 - Once I get the mixture "right" (ignoring WOT as that's hard coded in the chip), I then have to accept that my timing is fubared. This is where I am now with with Pro-m. Mixtures sorta OK but I have no way to adjust the timing. Enter the SMT again. With this box, I now also have the ability to advance /retard the timing. I believe (hope, pray as this part is truely key) that the timing signal conditioning is post ECU. This gives me the ability to hold the input signal constant while I then can tinker with timing and not have the factory chip get in the middle. Of course, this theory only holds so far as when you effect the timing you will effect volume which of course will mess with fuel. Slippery slope. But, again better than what I have now.

I think the trick/black art/sacrifice to tuning gods/ is the management of this duality. If you can get your arms around this and accomidate the skewing tables, I might have something better than I have today...which is very very blunt tune. Realistically, I thinking I'll end up running the car open loop full time and may even kill the WOT trigger.

And if this doesn't work, maybe I'll s-can the whole thing and go to a megasquirt setup and just get the ECU out of the way. I'm only going to be out $150 for a used SMT and any time I invest. I figure I'll learn just a bit more....it's not like this is a race car where I need to squeeze every last HP out.

So...when's that M30 MAF & chipset coming out?