Malefoda

Hi,

another question, does the stock ECU manage the KS in order not only to prevent knock but also to take advantage of higher octane level, wich makes sens to use for us 98 rated gasoline instead of 95?

Thx,
Matthieu

toplessFC3Sman

iTrader: (1)

the ECU in 2nd gens doesnt know what grade of fuel you put in, it just senses whether you're knocking or not. And if you are, it retards timing a bit, but at that point the engine may be done anyway

Malefoda

I mean on K series engines Mazda does push advance as far as it starts to knock, not in safe mode but in order to take benefit of higher octane rate.
Does the FC do the same? The advance is not dynamic?

Malefoda

Up for this,
you said "if you are..."
I ask, "if I'm not" will the ECU try further, which may mean more torque at low RPM at least...

Chief

its also worth noting, the only rx7's that had knock sensors, are turbo model cars. normally aspirated didnt have a knock sensor.
and no, the ecu really doesnt test the limits. its preset, and about the only time you could justify running higher octance, is if you have advanced the timing manually, whether by tuning electronics, or at the CAS; or you run more boost and/or timing.
the car runs great on regular unleaded in all stock (or close to) form.
and if im not mistaken, the turbo II/S5 turbo were both set up to run on 87 as well.

Malefoda

I've had a look in manuals, and yes it's a simple protection not dynamic. That said the ECU I have is the NE344 wich is for European markets et Japan, I think this can have to do with gas quality or/and emissions.
What is the average octane rate in the U.S? I remeber my Miata (NA18B) was 10° advance IT coz it was a worldwide setup. 14° was nice in France since the gas we have here is regular 95 and better 98 wich is often sold with additives. (FYI 95/98 here is RON so for matching the US specs (RON+MON)/2 it's like US 90 for our premium and 93 for our "98".
If it's done for 87, It's already out of rage to use the 95(US90). But we have nothing less
I'll have a look to IT tables soon... and hope to get benefit from 98!
Thanks for the answer Chief!

ericgrau

iTrader: (1)

Just use the lowest octane you can find then. The higher octane won't really hurt anything. It might not burn quite as completely, but it should be fine. If you have an N/A then it already runs a bit rich. That provides a nice big safety net against knocking even on low octane gas. If you have a turbo, some people like to use higher octane for a better safety net against knocking. Especially if the car has any power upgrades.

RETed

This is a waste of a thread cause the stock ECU does register the knock sensor above 4kRPM.
When talking about WOT power, it's useless.


-Ted

Chief

im not sure what your reply has to do with his thread, he was asking if the car dynamically advances timing based on octane. so the car does NOT (you left that little word out) register KS signal over 4000 rpms, thats another reason to what i was saying.

and malefoda didnt specify turbo or not, and i have yet to see a normally aspirated car with a knock sensor.

try not telling people they were 'wasting threads,' your input might be more welcome.

RETed

I don't think any stock ECU would "advance timing" based on octane.
Knock systems RETARD ignition timing based on knock.
To assume otherwise is pretty ignorant, don't you think?

Click on his profile, and it does say "Zenki Turbo".


You should go look at his post in the Aftermarket EMS section...


-Ted

Chief

ok, so assuming it would test timing advance until it reached as far as it would go would be odd, yes, ecu's start positive and go negative, this is true.

but as for the other two, if i researched everything beforehand, i wouldnt have time to post any replies.

now, im off to the EMS section to see whats going on.

Malefoda

Coooool guys!
Yes I have a Turbo, yes I want to tune it before go for MS.
I'll take advantage of the 98 when I'll pushed the IT maps.

Thanks for having making this point clear!