dizwiz24

Maybe Im having some trouble interpreting this correctly.

Im trying to understand how much knock retard is being applied in the following scan of my car.

In the lower right box, it shows that spark retard is 1.3. Yet timing went to 10. Commanded spark advance is 20 degrees and the max spark retard allowed at that RPM/MAP is 10 degrees.

Is it possible the decimal point on spark retard is not correct and it should be saying '13' ?

This is on a 93 supercharged corvette that was making 10 psi.

JackDidley

The only thing I can think of is, for my 87 Datamaster gives you a choice on the advance it displays. Total, that is base timing + programmed advance adjustments or just the added advance - base timing. Not sure about the display options on the LT1 cars. Click on that 10 degrees and see if it gives you a choice.

dizwiz24

No, it doesnt. I imagine the Lt1 is different as it uses optispark and all advance is 100% computer controlled.

It seems like the spark 'retard' display is off by a factor of '10'.

It'd be nice to know what the correct value (of spark being retarded) is..

VenkmanP

Just a WAG, but I think the spark retard shown is correct at 1.3, and it is only the amount of retard due to knock.

Other inputs can also cause retard. Perhaps that DTC has something to do with it?

Searching or posting over at camaroz28.com would probably get you a definitive answer.

dizwiz24

The only other input (other than the knock sensors) that can cause spark retard (on a 93 speed density), that I know of, is inlet air temp. However my inlet air temps show a very reasonable 35 degrees C (its relocated upstream of my supercharger).

So I cant figure out whatever else would cause 10 degrees of retard (from 20 to 10).

My tune indicates (from tunerproRT) that 10 degrees is the maximum spark retard that can be taken out for any reason for the MAP/RPM I was at when the event occurred.

Im trying to figure out if this spark retard of 1.3 is a known Datamaster TTS issue that its off by a factor of 10. Because thats what it seems like, it also correspondes with an event that seemed like detonation. Though Im still kind of surprised it occurred (wideband A/F was around 12.0:1 and spark advance at 20 degrees isnt anything too wild).

djxib

I saw exactly the same thing on my supercharged '92. In part throttle situations AE was a little lean and I was seeing a few knock counts and (according to datamaster) about 2-3 degrees of retard. However the car behaved like someone cut the fuel.

How is your car behaving? I'd guess that if the car is bucking then the total advance looks correct (and the retard is wrong) - if the car feels fine then the total advance is wrong and the retard is correct.

However - adding some other food for thought, I've seen that the LT1 can retard timing on individual cylinders.. maybe datamaster is reporting an average retard per cylinder?

Just my 02.

dizwiz24

This snapshot coincided with an event at WOT. A 'poof' noise, lack of power, and black smoke in the rear view mirror. Thankfully, it didnt appear to do any permanent damage.

Also, my meth injection system stopped working (need to build a sump, as air likely got sucked into it under the 'sloshing' conditions).

Even so, my AFR (its rigged to the A/C pressure input) didnt exceed 12.0:1 and 20 psi of commanded spark advance.

dizwiz24

what did TTS datamaster show under these conditions?
Did it show spark retard 2 or 3 degrees?
or did it show spark retard .2 or .3 degrees?
Or did spark retard not show anything and spark advance show what you commanded minus 2 or 3 degrees ?

djxib

It showed 2 or 3 (not .2). Same lack of correlation that you are seeing - i.e. total advance looked way too low.

I will be reloading all my tuning software in a few weeks - I'll look at my old scans.

dizwiz24

Yeah I've seen this lack of correlation before too, the fsm for my 93 says that iat input also affects spark timing.


I used to get tons of unaccounted for spark timing taken out before I relocated my iat upstream of the supercharger.

Though this is entirely separate from what im asking about here...

I want to know if anyone else gets spark retard displayed in tenths increments (they seem to be the correct # divided by 10)

armysnipe

dizwiz24 -I'm also getting spark retard readings in tenths while using Datamaster. Your spark advance plus your spark retard will equal your programmed (Main spark advance VS RPM VS Load table in Tunercat) spark advance at the given RPM and MAP (kpa), but you probably knew that already. As you have stated, I also relocated my IAT sensor and have much less spark retard now if any. Also, thanks for recommending Greg, his service has been top notch. I wound up going to the 8+6 setup with bracketry and have recently switched from 24LB INJ to 63.5. So I'm in the tuning stage. Have you had any sucesss using Tunerpro RT? For some reason I can only scan intermittently. That's why I've been using Datamaster.

dizwiz24

Same issues w tunerpro. I can tune fine, but the datalogging feature doesn't work well I haven't tried it in a while though.

No issues w datamaster tts, thoughit seems I am using an older version vs. The newest version.

I had issues datalogging w the newest da version of datamaster tts.