Mazda MX-5 Miata banner

1 - 16 of 16 Posts

·
Registered
Joined
·
7,975 Posts
Discussion Starter · #1 ·
Just finished hooking up the lc1 wideband with the simulated narrowband output to run with the standard ecu for now, just so i can log what the original ecu is doing.

Anywho.. all seems cool but 1 thing i have found of interest.

Upon first install everything seemed to be as it was with the narrowband sensor.. exactly identical infact, including the slight hunting i always had at idle.

I opened up the programmer and changed the update interval of the simulated narrow band to a munger interval, whatever the second longest setting was and i've now got an incredibly smooth idle... so much so that with the engine running and the roof and windows up you could forget the engine was running... which is a first for me with a 5.
 

·
Registered
Joined
·
7,975 Posts
Discussion Starter · #2 ·
well ive done a few logs with it to see how the stardard setup fuels.

Quite interesting results.

When cold the idle is at around 13.9 to 14.5
Any throttle requests a greater amount of fuel bring the figure to 12.8 almost exactly everytime.

Then when the engine warms i get a nice smooth idle at about 14.6
Now the interesting thing happens on accelleration.
If i use 100% throttle i get an AFR mix of 13.6 ish but light throttle sees it a lot richer at around 12.8.

I'm guessing this is likely to be due to the 1.6 having an on off tps. so maybe full throttle will let more air in with the same fuel mix as part throttle.

Either way its highlighted somethng id been seeing with my fuel usage.. i.e. if i put my foot down everywhere i get much the same mpg as i do taking it easy unless im on the motorway holding a speed which the afr readings show the ecu does a nice job of finding 14.7.
 

·
Rollin' on 15's, baby!
Joined
·
4,393 Posts
I'm guessing this is likely to be due to the 1.6 having an on off tps. so maybe full throttle will let more air in with the same fuel mix as part throttle.
Yes, the early manual 1.6 TPS just has switch contacts for idle and WOT (no analogue signal). The stock ECU bypasses the O2 closed-loop when WOT is detected.

If you want it a bit richer at WOT on the stock ECU then an AFPR might help, although having invested 200 sheets in an LC1 then a MegaSquirt would seem to to be the next logical step for you.
 

·
Registered
Joined
·
7,975 Posts
Discussion Starter · #5 ·
Oh im all good on the MS front, lol. I had about 15 of the buggers in my living room this time last week.
Is there an in between on the TPS switch at all.. i.e. no throttle, part and WOT as it seems to not know the difference between very small amount of throttle and all out.
 

·
Rollin' on 15's, baby!
Joined
·
4,393 Posts
Is there an in between on the TPS switch at all.. i.e. no throttle, part and WOT as it seems to not know the difference between very small amount of throttle and all out.
No, there is no analogue signal for part-throttle loads on the 1.6 with manual transmission. Engine load is determined from the MAF sensor and possibly the MAP sensor built into the stock ECU, although I suspect that the MAP sensor is just used to provide barometric correction.

I believe that the auto 1.6 does have a proper throttle pot.

Your comments further above would seem to suggest an observed difference in fuelling at WOT and part-throttle (AFR is 13.6 vs 12.8?). If the MAF flap hits the internal stop before the throttle reaches WOT then fuelling is probably not going to change much until the WOT contacts close on the TPS.
 

·
Registered
Joined
·
7,975 Posts
Discussion Starter · #8 ·
thats what i thought.. makes me think the ecu is using the tps for fueling now though looking at my results.
 

·
Registered
Joined
·
7,975 Posts
Discussion Starter · #10 ·
the fact that the afr difference between part throttle and full is so different.. and in the opposite way to what i would have expected to see.. i.e. richer at part throttle. Like you say, an on off, but almost like it goes to on and says fuel more.. then as the throttle opens further the ecu pumps the same amount of fuel in still leaning out the mix as there is more air to that same fuel.
 

·
Rollin' on 15's, baby!
Joined
·
4,393 Posts
the fact that the afr difference between part throttle and full is so different.. and in the opposite way to what i would have expected to see.. i.e. richer at part throttle. Like you say, an on off, but almost like it goes to on and says fuel more.. then as the throttle opens further the ecu pumps the same amount of fuel in still leaning out the mix as there is more air to that same fuel.
I must admit, the richer AFRs at part throttle look weird to me too, but have you got your ignition timing sorted yet? Are the O2 and engine coolant sensors good? Dodgy O2 and coolant sensors will give you a rich mixture on part throttle but will have virtually no effect at WOT.

Remember, at WOT the stock ECU will only be using fixed injector periods from a simple look-up table. There will be no adjustment due to O2 sensor feedback and the MAF sensor is probably being ignored too. In this scenario if your fuel pump is getting a bit tired or the fuel filter is getting clogged up or the FPR is out of whack or the injectors are dirty then you might not be getting as much fuel into the cylinders as expected.

I had my injectors cleaned by an ASNU franchise recently and the flow rate on one of them was 20% less than the other three.
 

·
Registered
Joined
·
7,975 Posts
Discussion Starter · #12 ·
20%


thats quite drastic.

I'm using this pre MS period to work out any niggles I can with the car first.. i.e. like you said.. injector cleaning and fuel pressure.

What im aiming for is the most rock stable afrs i can produce before fitting the throttle bodies and tuning with the MS.

Idle is a little eratic at the moment which it is always going to be but i think i can get it smoother if the injectors and spark were perfect.
 

·
Premium Member
Joined
·
19,520 Posts
the fact that the afr difference between part throttle and full is so different.. and in the opposite way to what i would have expected to see.. i.e. richer at part throttle. Like you say, an on off, but almost like it goes to on and says fuel more.. then as the throttle opens further the ecu pumps the same amount of fuel in still leaning out the mix as there is more air to that same fuel.
Open loop occours at anything above 4k irrespective of TPS position on the stock ECU, so what you say doesn't surprise me. I'd bet a good portion of £$£ that above 4k the flap in the AFM is near it's upper range, (or at least at the top end of it's linearality).

In effect you'll be at pretty much the same position on the stock fuel map yet the *actual* TPS positions are quite a long way from each other.

Obviously this is 'keyboard warrior' conjecture, but it fits the symptoms
I still stand by my ascertation that the 1.6 ECU doesn't do anything with the TPS inputs bar WOT or Idle.

and the MAF sensor is probably being ignored too
It won't be, the MAF/AFM is the primary sensor for the ECU's fuelling. (like the MAP sensor is for any MAP based ECU).
 

·
Rollin' on 15's, baby!
Joined
·
4,393 Posts
20%

thats quite drastic.
You would think that 20% less flow on one cylinder would make for reduced fuel consumption due to lean running, but rough running and poor fuel consumption suggested otherwise.

The stock fuelling arranges the injectors in batched pairs and with only one O2 sensor and a slow ECU it makes it very difficult to apply corrections on a cylinder-by-cylinder basis. The ECU assumes that all cylinders are fuelled equally so when one cylinder is thrown out of whack by a weak injector it overfuels on loopback to bring the AFR back down. This results in an unbalanced mess.
 

·
Registered
Joined
·
7,975 Posts
Discussion Starter · #15 ·
the fact that the afr difference between part throttle and full is so different.. and in the opposite way to what i would have expected to see.. i.e. richer at part throttle. Like you say, an on off, but almost like it goes to on and says fuel more.. then as the throttle opens further the ecu pumps the same amount of fuel in still leaning out the mix as there is more air to that same fuel.
Open loop occours at anything above 4k irrespective of TPS position on the stock ECU, so what you say doesn't surprise me. I'd bet a good portion of ?$? that above 4k the flap in the AFM is near it's upper range, (or at least at the top end of it's linearality).

In effect you'll be at pretty much the same position on the stock fuel map yet the *actual* TPS positions are quite a long way from each other.

Obviously this is 'keyboard warrior' conjecture, but it fits the symptoms
I still stand by my ascertation that the 1.6 ECU doesn't do anything with the TPS inputs bar WOT or Idle.

and the MAF sensor is probably being ignored too
It won't be, the MAF/AFM is the primary sensor for the ECU's fuelling. (like the MAP sensor is for any MAP based ECU).
[/quote]

I think you maybe found the nail and given it head or whatever the common saying is.
 

·
Super Moderator
Joined
·
22,535 Posts
Yep I found that much smoother through out especially at idle.
 
1 - 16 of 16 Posts
Top