I've been doing a lot of searches for timing under boost with a KA-turbo engine and it seems to me like the general concensus has been to retard x amount of timing for every y amount of boost...

My question is that timing retard done by rotating the distributor so that the pulley shows ~17deg timing, for example? Or is that done under the ignition map in your fuel/ignition controller only when the engine is under boost?

To me, it seems safer to retard timing by 3deg at the crank by rotating distributor and then going into emanage and advancing timing at points where the engine is not under boost, including at idle.

Rather than putting the crank to stock 20 deg and retarding in ignition map the areas under boost.

I just want to get your guy's opinions on this subject. I have no way of measuring total timing and will have to be extremely conservative with timing. I'm also in socal and we have 91 octane for pump gas.

what type of ecu are you running?

Ideally, you would run a stock-ish timing curve at any area with vacuum...then retard for every PSI, as you know.

Start retarding the timing at maybe 2psi, and for a conservative setup, do .75 degrees per PSI if boost.

E-manage can do this, if you have the pressure sensor (MAP)...it still uses the MAF to meter the air, and does the retard by pressure.

Reason this is better than turng hte base toiming to ~17 is that you can reatin the off boost respobnse of an N/A setup, but be safe under boost.

The cheap way to do it (say, with an FMU, AFC, or Hacked MAF) is to retard the base timing. You have the means to do it right..use it.

Set your base to 20 (with the TPS unplugged!) and then tune the E-manage.

Later - Brian

:: orion :: wrote:E-manage can do this, if you have the pressure sensor (MAP)...it still uses the MAF to meter the air, and does the retard by pressure.Later - Brian

Does that mean it can only retard timing with the pressure sensor?

The other day I was fiddling with the ignition map and it looks like the unit was retarding/advancing timing according to the value I entered. This was at idle without the pressure sensor.

Michael - I have the stock 97 ecu with E-manage with both harnesses.

Also, one more thing Brian - does the ecu use a default fuel/ignition map when the check engine light is on?

MSD Retard control box or whatever they call it. THats exactly what you want.

NateDogg wrote:MSD Retard control box or whatever they call it. THats exactly what you want.

No it's not. I already have something that can retard/advance timing. I just need clarification on how it works.

yea that is the msd btm. im using one now and it works great, and it is the best way to retard timing if you are running a hacked mafs or fmu. much better than just retarding your base timing. i picked mine up for $115.

bruinbear714 wrote:No it's not. I already have something that can retard/advance timing. I just need clarification on how it works.

It uses the pressure sensor to determine boost. Once boost is measured it will then go to that corresponding point on the ignition map. It should have a layout of vacuum and boost, which are just signals from the pressure sensor.

Nismo_Freak wrote:It uses the pressure sensor to determine boost. Once boost is measured it will then go to that corresponding point on the ignition map. It should have a layout of vacuum and boost, which are just signals from the pressure sensor.

I'm not sure if that's how it works.

The ignition map is a function of maf voltage and rpm, so can't the amount of boost be inferred from that combination? It may not be exact, but you can still retard timing if the MAF voltage is higher than what it should be with a N/A setup. If so, why does one still need the pressure sensor?

Anyhow, thanks for the info everyone. I think I'll retard timing with the distributor by orion's forumula of 0.75d/psi and advance it in emanage when the engine is not under boost.

bruinbear714 wrote:Does that mean it can only retard timing with the pressure sensor?

The other day I was fiddling with the ignition map and it looks like the unit was retarding/advancing timing according to the value I entered. This was at idle without the pressure sensor.

Michael - I have the stock 97 ecu with E-manage with both harnesses.

Also, one more thing Brian - does the ecu use a default fuel/ignition map when the check engine light is on?

You can retard timing based on your MAF voltage with the E-manage... I guess you can MAP it too... But I dont have my MAP installed yet.

I was under the impression that the MAP sensor is to be used with the e-manage only to expand the resolution of the timing map itself. You can only reference up to the limitation of how high the MAF can read, beyond that you will either need a MAP sensor, or a bigger MAF.

That's how I've always understood it, although I can see how it should be possible to tune directly from pressure (boost) readings taken from the MAP. Why not switch the sensor from MAF to MAP in the software, and see if the references on the tuning chart change at all?

Did you ever consider a megasquirt system?
I know it is a wire it yourself system, but with:
CTS, CPS, TPS, MAP, O2, with wasted spark and batch fire ignition, you can have a pretty nice setup for under 600.
I have the same question as to what the original timing to this motor is. I use only map and the car idles and drives fine.
Exchange all the work that is needed for the eeprom tune on stock ecu, rigging a MAF, and all the other "mods" you need to do, a standalone megasquirt will get you on the road soon.
If you find a stock tune on ka24e, please let me know. Blowing my built motor is the last thing I need right now.