NA6 stock ECU tuning - definite torque flat-spots etc.

[Jace]

you guys, my car is driving a little bit strangely.
i've recently had a bit of work done, including a new clutch, new water pump, new spark plugs, air filter etc.
i've been noticing very definite flat spots in the torque band under slight/increasing throttle.
from what i can tell, it's mostly between 1500 and 2100 rpm.
what i'd like to know is whether this can simply be tuned out/up/whatever by a car tuning place (Dalton Automotive or somewhere similar).
it's become more noticeable since i had the work done, but i'm sure it was there long beforehand. it occurs most noticeably in third gear (probably because i mostly accelerate partially in that gear), under slight throttle, maybe 1/4 or so.
help would be super awesome, thanks.

[Russellb]

The stock ECU is not tuneable
Anyway WHAT ARE YOU DOING DOWN THERE 1500 - 2100 rpm there is no power
Knock it back a gear and Shift when you hit the limiter

No seriously they dont pull the best at those revs and there are spikes in the AFR which causes your
stumble Chough miss (what ever you want to call it )


The NA6 LOVES being between 4000 - 7000 RPM
be kind give it want it wants

[Jace]

haha for the most part of my driving i'm getting wheelspin in the wet around corners through second and into third
and otherwise i'm shifting at 4-6k rpm anyway
just that i'm trying to "improve" my driving manner (drive more responsibly etc) and staying at low revs seems to allow me to achieve that.

yeah okay so i figured it wasn't tunable, but i thought it might be an error in the stock ECU's allowances for air fuel mixture or something along those lines.
hmmmm... tunable ECU time.

[kazjim]

Not just you, Im getting the same symptoms ...

I took off the pod filter and put on a "slightly holed" stock air box (3 x 2" holes - 2 in bottom and one in the side) knocked the timing back 2' (Was pinging, even with 98 octane!)

i now have definite "surges" in the power under 3000 ....

I think my fuel pump is on the way out, as even under light throttle, there are 'pulses' in the power all the time .... almost like a single cylinder was firing less than the others .... except it doesnt change with revs !

(thus thinking fuel pump ...)

Hmmmmm, so the only 'tunable' setting on the stock ECU is the timing ?

J

[Russellb]

Hmmmmm, so the only 'tunable' setting on the stock ECU is the timing ?

J

YEP That And Idle

Currently Working on a Plug and Play Autronic SM4 fro all model MX5's

[StanTheMan]

Hmmmmm, so the only 'tunable' setting on the stock ECU is the timing ?

J

YEP That And Idle

Currently Working on a Plug and Play Autronic SM4 fro all model MX5's

you can tune the AFM to an extent. But I doubt you could tune the flat spot out with that and you need to break a seal as well. I'd be checking the leads, spark plugs & O2 sensor as well.

[mx52nv]

Currently Working on a Plug and Play Autronic SM4 for all model MX5s

Woah...
NA6CE
NA8C
NB8C before model change
NB8C after model change
NB8C SE turbo (pins different)
NCEC before model change
NCEC after model change (any difference in plugs/pins???)

So will this SM4 have 6/7 different plug in adaptors/wiring harnesses or different plug connectors built into each ECU?
Are you doing all the hard work involved in using an oscilloscope to measure the signals to the NB8 alternators?
I am definitely interested in what you are doing so PM me if you have any further information or if I am able to help.
Les

Sorry for being off topic - please let normal transmission continue.

[Jace]

haha for the most part of my driving i'm getting wheelspin in the wet around corners through second and into third
and otherwise i'm shifting at 4-6k rpm anyway
just that i'm trying to "improve" my driving manner (drive more responsibly etc) and staying at low revs seems to allow me to achieve that.

yeah okay so i figured it wasn't tunable, but i thought it might be an error in the stock ECU's allowances for air fuel mixture or something along those lines.
hmmmm... tunable ECU time.

Can confirm that there are no flat spots in the stock ECU at those revs. I have a 5km trip to work and make a point of keeping engine revs low until oil has warmed up so a fair portion of my driving is 1500-2500 rpm. Apart from a slight flat spot the first time I change into third gear on a cold morning (does anyone else get that?), there is no sign of any flat spots.

And don't worry, my NA6 gets to clear its throat after the engine oil is up to temp

ummmmm, maybe not in your car

[Russellb]

Hmmmmm, so the only 'tunable' setting on the stock ECU is the timing ?

J

YEP That And Idle

Currently Working on a Plug and Play Autronic SM4 fro all model MX5's

you can tune the AFM to an extent. But I doubt you could tune the flat spot out with that and you need to break a seal as well. I'd be checking the leads, spark plugs & O2 sensor as well.

What Stan Said

( where is the DOH smiley)

[Jace]

doesn't an ECU tune itself sort of depending on what fuel it's being fed and what air it's breathing in? that's more so what i was referring to.

i think this is getting more and more noticeable every day.
it's so definite now that i can feel myself being pushed back into the seat as i hit a flat spot (it pulls a fair bit more very suddenly, more so in 1st or 2nd) always around the same rpm.
what else could cause something like this?

[Juffa]

Leads (you said plugs were changed, what about the leads?)
Plugs
Blocked air filter
AFM - some people try and take this off by undoing some screws and actually break the electrical connections, which will cause dodgy running.
Timing belt - taken off to get at water pump. Was a new timing belt put on. Is the timing out/belt jumped a tooth.
Fueling issue (blocked fuel filter/injectors)
o2 sensor (low probability)
bad batch of fuel

See if a Geelong or other member is willing to swap over stuff with you to try and eliminate the issue.

J

[kazjim]

"o2 sensor (low probability)"

Yea, i was wondering about that - isnt the ECU in open loop during acceleration ? only going closed (and thus reading the o2 sensor) when at light throttle cruise ?

I'm leaning towards fuelling for mine ... hoping to get 10 minutes to look at the fuel pump this weekend ....

J

[Jace]

thanks juffa.
i will consider all those things when i speak to a mechanic.
i'm certainly not up to diagnosing running issues yet.

is it normal for a mechanic to overtighten a timing belt to allow for stretching?
when i got my car back from having the waterpump, plugs, air filter etc replaced, he told me there's a "bit of a whining noise, because i found the timing belt was loose after i replaced the waterpump..." (der)
the noise almost sounds like it's supercharged haha. i freaking wish!

[StanTheMan]

is it normal for a mechanic to overtighten a timing belt to allow for stretching?
when i got my car back from having the waterpump, plugs, air filter etc replaced, he told me there's a "bit of a whining noise, because i found the timing belt was loose after i replaced the waterpump..." (der)
the noise almost sounds like it's supercharged haha. i freaking wish!

unlikely.
The timing belt runs around the crank shaft & cam gears. Along the way it also passes over some runners which automatically tension the timing belt. The water pump gets dríven by aaccesory belt.

Usually when there is a noise like you describe. The first suspect I'd have is the water pump. closely followed the runners.

The water pump has allegedly been replaced......
Over tightening the belt? sh*t......is that possible? or is he talking out of his arse? one of the runners is kind of pre loaded it has a specific spring loading within it to keep the cam belt tight & allow for stretching.

I have a feeling he's kept the original runners. which are making that noise & if he's managed to tighten that runner more than what its meant to be....it can't be good. Its probably then making that extra supercharging noise because its too tight( if he's managed to tighten it more than its supposed to be)

I'd almost put my bet that the runners are out......or will be very shortly.

As far as the tune goes. I doubt the runners, even if he's managed to over tighten them, will affect the tuning issue.

if the runners do break or loosen too much.....the engine will be pretty noisy. You will now about it. I doubt they will break. They just sound like they are worn out.

ohh and as far as the O2 sensor.....yes very small chance but would probably be one of my last things to check.

I would certainly check your leads & plugs

[Juffa]

Actually I had one thing around the wrong way. I said you have to remove the timing belt to get at the pump. It is other way around.

Anyway to Stan's point. There are two pulleys that the timing belt runs through. One of these uses spring tension to press against the timing belt. Without this tension the belt could slip. If it slips the cams get out of Sync with the crankshaft...not good for the engine or you (worst case). Anyway get yiurself and the car back to the shop and get it looked at.



http://www.miata.net/garage/timingbelt.html

These are usaully replaced every 100,000Km (major service) with the timing belt (and water pump (sometimes)).