Cold start SM4

[RGA-1200]

Hi All,

First post on the new forum!

I have the install of the SM4 going pretty well now on my 3 cylinder motorbike, previously on carbs. The basic mapping and running of the motor is now basically 'right'. Now I can run through and start to address the minor issues. First on my agenda is the cold start - it is not perfect.

So far I have no idle valve, so it is all manual at the moment. I can very easily reach the idle screw on the throttle bodies while on the bike, so not such a hassle, although I'd like to enable full idle control eventually. One step at a time.

What I have been doing is giving the throttle stop screw one turn, which corresponds to about 2% throttle. This is about right to make a fast idle of about 1500 once the motor is first running. But I have to crank for a LONG time before it will even start to try to fire. Not a great thing on a bike where your battery/charging system is limited.

At present the best method seems to be leave it at zero percent throttle, crank over for 5 seconds or so, give a slight crack of throttle and then once it fires, give one turn on the throttle stop to achieve a good idle.

It seems to need a squirt of fuel to start, but there seems to be no 'cranking fuel mulitplier' setting. On the original very crude carbs, the choke mechanism bled large amounts of air and fuel in, it would go to 3000rpm and 8-stroke within about 5-10 seconds if you left the choke on, but it would always fire on the first or second turn of the crank. Normal method was to remove the choke almost immediately.

I tried a larger w-u fuel multiplier, but that seemed to make it worse. Once the motor fires it is pretty much ok and will idle straight away with the 1-2% throttle applied. Re-starting warm is perfect every time, even after only 30 seconds to 1 minute of running, it just seems to need a shot of fuel to get it to fire initially.

Is there a way to do that?

Thanks in advance
Steve

[MRMRacing]

I have spent many hours trying different start-up methods and also trying many IAC and prefer the Bosch 3-wire. It is little big on a bike you can also consider running a small valve like the the boost valve and set up a gpc function, smaller in size to fit bikes.

Regarding your start up:
When you say cold start is it Swedish winter cold start or a Aussie cold start which we call hot start here:o

You have the "P-S enrichment" which is the amount of fuel just while starting and the "P-S time out" how long the extra fuel is added.

Also your base fuel table applies to the startup, normally a value around 10-15 higher than idle is used at zero rpm. If you use MAP sensing you start with 100 load. If using TPS you start at that tps angle value cell.

You can make a log (Press F8) during start, open the log while having the base fuel table at top, walk thru the log from start and it displays the cells affected during start in the base fuel table.

The fuel during start is affected from base fuel values, W-U mul and most important P-S enrichment (and smaller amount from other corrections, like charge temp and more).

[Chris]

Post start multiplier is used on crank. Try larger or smaller values.

Chris

[Wroom]

Post start enrichment is more useful than warm up enrichment on an air cooled engine.

[RGA-1200]

Thanks guys!
I ignored P-S enrichment, because the very meaning of post-start would seem to mean after the motor has started!

I will give it a go tomorrow, one of the problems with this is you really only have one go at it, because even after the motor has run for just a minute or so it will then start easily.

And yes, when I say COLD start, I mean the depths of an Australian early Autumn with shivering temps well below +20C overnight!! ;-) As I write this close to midnight the temp has already plummeted to 21C. Actually, where I live we may see minus 5 or so overnight in the winter, so it gets at least a little cold.

Regarding idle steppers, I think I won't use a car type because of the size, though i'd like stepper control as that's just neat. Will have to find a nice small solution when I get that far. Plenty of questions to come before then.

Cheers
Steve

[Ian]

PS (Post Start) and WU (Warm Up) multipliers operate as follows;

WU mulitplier is based on Coolant temperature and Load inputs and the operating point can easily be seen in the table.
PS multiplier is based on Coolant temperature and PS Timeout value at the same temperature and also the engine run time. If the PS Multiplier table value is 4 and the corresponding timeout is 10 seconds and the engine has not reached Run speed (400 rpm) the effective value of the PS multiplier is 4. If the engine has been running 5 seconds (half way to timeout) the Starting value of 4 will have decayed to 2. At 10 seconds run time the effective PS multiplier is 0 as the timeout has completed its countdown.

The actual Multiplier applied to the Base Injection pulse is the GREATER of either the WU or PS value. They are not applied together. If the PS value is greater than the WU value at a given temperature the PS value will be applied until the engine starts and the PS value decays to below the WU value. This applies to all SMC, SM2 and SM4 (up to firmware v1.08) ECU's.

Cranking enrichment is generally applied in the PS multiplier as this has the Timeout value which allows for a high initial value that can be quickly decayed away after starting.

[roberto arano]

Ian,

I've been most impressed without the detail of your technical explanations. In only a few months much more information has been divulged on this forum than in any of the manuals or the forums. For example the lean highway mode explanation and how the trigger teeth number effects the algorithms.

I've started making my "own owners manual" from post here, that will supplement the supplied manuals (for my use).

I am sure many others are doing the same.

Keep up the good support.

Thanks. I think think evryone was a bit concerned when things changed a whiloe back, Ray was excellent, so are you. Autronic will do well, as it should.

[RAC]

Ian should look into making some manuals. It might end up being 1000 pages or more but i'd buy one for sure.

[Chris]

Ian is always very busy these days, perhaps "wroom" can put pen to paper for us.

Chris

[RGA-1200]

Thanks again everyone, I made some changes to PS and also increased WU accel enrichment, as in the first few moments it would also not take any throttle. Behaving very nicely now, positively jumps into life and revs up straight away. Great! The only thing required for more thorough testing is cooler temperartures! On to the next question, which I shall formulate and post in a new thread...

Regarding a manual, the current one and the software help files are in need to a healthy edit, firstly to remove the many spelling and grammatical errors, secondly to improve the breadth and clarity of the info. Whatever happens, it should be an official Autronic product and should ship with EVERY SM4 and be available (at least in PDF format) to all owners. The absurd availability issues and general poor quality of the manual was my only gripe with what is otherwise a brilliant product.

The above is intended as entirely CONSTRUCTIVE criticism only!

Cheers
Steve

[MRMRacing]

The only thing required for more thorough testing is cooler temperartures!
Cheers
Steve

Welcome to Sweden Steve!:D
(But in this winter I have not seen less than -4 degrees...)

[Ian]

I am working on new Manuals but I need about 30 hr days and 10 day weeks at the moment.

[blentz2sm4]

Steve,
I have this problem with the SM4 on my race motor. It's like it needs the cylinder to be "wet" to get it to fire. How big a change did you make on the PS and WU values? Did you extend the timeout as well?

[RGA-1200]

Just checked my two cal files again, didn't change the W-U Accel Enrich at all actually, changing the multiplier was enough to fix the acceleration as well. P-S Timeout I also did not change.

Changed P-S Enrichment from
-15 - 3.62
0- 2.25
20-1.3
40 - 1.25
60- 1.16

To:
-15 - 3.62
0- 2.5
20- 2.0
40- 1.5
60-1.16

Is pretty warm here right now, so testing anything much under 20C has to wait a month or two. Will probably need to bump up the zero level a bit. Will never see sub-zero engine temps so below that is a problem for the Swedes alone! :-)

Cheers
Steve

[Dark_Knight]

The fuel during start is affected from base fuel values, W-U mul and most important P-S enrichment (and smaller amount from other corrections, like charge temp and more).

Hi, I like to ask as I am using SM4 with chip 1.09 that has the Start Fuel Factor. In this case, how should I go about tuning the crank start? Is there a method of doing this?

Please advice if I am doing it correctly. Thank you!

I only adjust values of base fuel after car is warm up or coolant temperature is from 60 to 90 deg.

For coolant temperature from 20 to 59 deg, 91 to 120 deg, I will adjust P-S or W-U or Start Fuel Factor... But very confuse which I should concentrate on or when to adjust which.

For W-U, I did not adjust it unless after car is started and doesn't run well or stall at particulate temperature, I will increase that cell value to correct the problem.

[MRMRacing]

First you need the base cal table to be correct, and values at zero rpm should be approx 15 higher than the idle value.

Then you can adjust the start up fuel, the 1.09 has two start fuels that are applied differently depending of how the engine was shut down and how long it has been off.

The start config must be set to the injectors that are used and the maximum pulse width. (I use 5 mS here)

Then start fuel factor is set, normally double the P-S Enrichement table.

So the start fuel factor table is only used in some cases like overnight with normal shut off engine. Then the P-S enrichment table & Time are used.

[Dark_Knight]

Thanks for the advice :)

Right now, my base cal table is a lot more than idle value, about 25, should I bring it down to 15?


Just to clarify, with normal shut off:

If car is off for overnight, SM4 will used Start Fuel Factor?
If car is off for a short while (5min to 3hrs), SM4 will used P-S?
Thanks again for your help :)

[MRMRacing]

Yes and No, I did check my old mail and in early 2008 I did some testing for Autronic on the cold start. And I do not want to tell other makers how this is done but there are 6 different start-up "versions" depending of time and how the engine was shut off.

Sometimes the Start fuel factor are applied then P-S.
And in other cases only P-S.

[Dark_Knight]

Hi Robert,

I being trying to figure out the crank start since the last reply from you. I think I have more understanding of how it work, but some how it still take a long time for my car to start during cold start and after engine is warm up... I have attached the cal file with this reply, can you please help me take a look as I not very sure where I am doing it wrong...

Car: Mazda RX-8
Turbo Charged with 3mm Apex Seal, E-Throttle with Bosch 2 wire IAC.
Autronic CDI. Using RE High Flow Cat.

[MRMRacing]

Base fuel table seems little "unstable" at low rpm´s, I use around 15 higher values in zero rpm and below idle.

Your P-S seems to low specially at colder temps, the start fuel factor is way to low.

[Dark_Knight]

Will try to increase the value when I get my car back from the workshop. As the coldest we get over here is 28 to 29, do I stll need to increase the start fuel factor or P-S value that are below 20 deg C? Or have them the same as 30 deg C will do?

[Ekman]

Hello,

lending the topic a bit.

Im currently seeing AFR around 11 - 10.8 for a while when starting the car.

What parameter(s) do i adjust to get the AFR leaner?

Thanks in advance!

[supercharged88]

If your mixtures are too rich after the engine has started,
try adjusting Post Start Enrichmentment Multiplier,
then play with Post Start Time Out.

[underpsi68]

Hello,

lending the topic a bit.

Im currently seeing AFR around 11 - 10.8 for a while when starting the car.

What parameter(s) do i adjust to get the AFR leaner?

Thanks in advance!
How long does it stay rich for? It can either be the P/S fuel or the W/U fuel.

[Ekman]

How long does it stay rich for? It can either be the P/S fuel or the W/U fuel.

I havent measured it, but i would estimate at least over 30 seconds

[underpsi68]

I havent measured it, but i would estimate at least over 30 seconds
Than you adjust P/S enrichment (post start) for the % fuel change and P/S timeout for the time that the extra fuel is added.

Both are under the M4 tab.

[Ekman]

Here is some logged data. Two .cal files and two .dat files, taken on seperate days.

Only differense between the cal files is that i modified basefueltable.

In the cold_start_2 file you can see the AFR richening.
Right after start AFR goes to ~10.6 then leans to ~13.0
and then it is richening up to ~11.1 , so how do i stop it from
injecting fuel too much??