Speed-density
 

I´m just starting out with MS(a week or so) and I´m having trouble to sort out wich sensors I can or have to use and wich sensors I can ignore(want to keep it as simple as possible in the begining and only use MS for fuel).
It says in the "megamanual" that MS provides either speed-density or alpha-N fuel control.
Though I have a JRSC(perhaps T28 in the Winter) speed-density is the choise for me.
Can I ignore the TPS and just use MS-map+IAT+CLT+O2+CAS(outer ring for RPM)?
When I have cut the injectorwires to the OEM-ECU, will the OEM-ECU still be able to control idle??
I have a NA-95, 1.8.

/Fredrik from Sweden

Splicing into the TPS is not really a problem (it's just 1 wire) and since you have a '95, your car has a true (linear) TPS which is worth connecting (if not for anything else, for datalogging). It will run fine without the TPS though.

Yep, Mapdot accel enrich works just fine.
I don't know how the 1.8 controls idle, but you won't have any problems from connecting the injectors.

Deleted

Ryan can you please delete this part of your post.

Speed density is only one of the fuelling algorithms that is available with the megasquirt. IT DOES NOT CREATE ANY RESTRICTIONS!!!!

If anyone uses the Alpha-N fuelling algorithm on a turbo car (as Ryan's post suggests for you to do) then you WILL destroy your engine. No if's, no but's, only a dead engine.

If you cannot get the speed density algorithm working on a turbo car (and it will only be for idle) then use the Hybrid Alpha-N algorithm.

For YOUR sake, please ignore the part of Ryan's post that suggests not to use Speed Density.

I thought the 1.6 air meter was a speed-density system and that it could be deleted with most standalone systems including megasquirt, but I guess I was wrong. Thank you for correcting me ... Ill have to do some more reading about air sensors before I make a post like that again ;)

Almost every EFI system runs a speed density fuelling algorithm from the factory. The fuelling algorithm has nothing to do with the AFM on a 1.6. I agree that the AFM does create a restriction which the megasquirt will allow you to remove (as the megasquirt uses a map sensor to determine the manifold air pressure.) But that is a totally independent thing to speed density.

Yeah i just did some reading and I had my terms a bit mixed up, lol. I was thinkin he was going to use the AFM

?? This part I have a big problem understanding. If the injectors only are connected to the MS how can the OEM-ECU handle the idle? I think I´m missing a piece of the cake here. :confused: If the OEM-ECU can´t "talk" to the injectors, how can it adjust the right amount of fuel for idle? Is the IAC adjusting the idle by regulating "extra" air and the MS adjusting the right amount of fuel do to table-settings? Bare with me, I´m new to this and on top of it I´m Swedish, ;)

This was my simple plan(but it gets more complicated for every day when I see what others do):
I thought I buy a MS-1 with a V3-board, do the simple mods with the 1k 1/4w Resistor and the two 470 ohm 1/4w Resistors, share all the OEM-sensors by splicing in MS to the stock harness, cut the injectorcables to the stock-ECU and connect them to MS, and then use the MAP-sensor from the kit.

I´m just doing MS for fuel(to begin with), will it work if I stick to my plan?

Thanks for all your replies! :)
/Fredrik

Idle control seems to be done by the IAC/ISC (depending on what year your miata is) and this is controlled seperately to the injectors. There is a different version of MSnSE 029 that also uses spark to control the ignition. I am running a hi-res version of this code on my car and it is giving me an idle +- 10 rpm (840 - 860 rpm) from the perfect idle. As I get more familiar with the settings I see no reason why I can't get the idle +- a couple of rpm.

There is no reason why you can't get your car up and running with fuel only. But I will bet that once it is running on fuel only you won't wait long to get spark working as well!!

Aussie, is the high res version of code good then? I've just been reading the topic on msefi.com and it sounds very impressive.

Is the spark control of injectors included in this code too, or is that a different version again?

Thanks

The hi-res version of the code is really good. It is so much smoother than the standard code that once you try it you won't want to go back to the standard code.

The hi-res idle code doesn't have the spark controlled idle. That code has been written by keithmac from the msefi forum. I sent keith an email asking if he had done a hi-res version of the code and he sent me back his latest version of the idle code and asked me to test it for him. Really cool stuff!!

The version of the code that I'm using has an occasional spike in the pulse widths and I'm hoping to datalog that soon and send it back to keith so he can improve his code further.

Spark-controlled idle sounds like somthing i need. No additional board soldering... Would you just disable the factory computer controlled ISC and set it through the MS spark? i'm tired of idling at 1200.

I wired up the air idle control to the MS from the PWM Idle Control section of the MegaManual.

Then I installed keithmacs' code and away I went.

I'm using the closed loop idle control which I never got working properly using the standard code, and my engine idles between 840 - 860 rpm when it's up to temp.

If you want to try out the code send me your email address and I'll send it to you.