Ok guys, I have a timing tuning question that has been brewing in my mind for a little while.

Background: On Neptune, I have tuned my fuel curve near perfectly on the street so as not to eat up dyno time/money. I have slowly worked up to my max target boost of 26psi on E85 (around 11.8 on the wideband gas scale) on a previously tuned pump gas tune. Car pulls good, plugs look good, no signs of detonation or breakup at this stage. I am getting ready to put it on a dyno to do the timing maps as a final step. I'm trying to formulate a fast timing tuning method/technique to minimize my time/cost on the dyno.

Here is what I'm thinking I'll do. Check my thinking here, and let me know if this is sounds like a good technique for doing timing.

Set my target boost sorta low, so I can hit, say, the 12psi column, do my pulls adding timing to the HIGH CAM maps only until MTB is reached for that column. Then jump right to the 26psi column, again HIGH CAM only, and do the same. Then interpolate between the 12 and 26 column in the HIGH CAM map spreading out the columns evenly between these 2 "reference points" I just found, and call it good. Then when off the dyno, just make the low cam maps' columns' values mirror the high cam map values that I found to be correct on the dyno.

Does that make sense? What I'm saying is do high cam FIRST in 2 columns to get good reference points for max torque between the 2, interpolate between the 2, and then make the low cam timing maps columns values match high cam values right before VTEC switchover (taking proper timing curves into account and all that of course). I can post up my maps too if that helps. Any tips or pointers on how you guys go about timing tuning on the dyno would really be appreciated. Thanks!

P.S. I have read the Crome tuning manual that is floating around till my head felt like it would come off. Awesome writeup whoever did that - really good info to get started. My idea above is just a different possible technique that I need your guys' opinion on.

 

that's kinda backwards. supposed to tune low cam first with vtec disabled, then set vtec a little low and enable it and tune high cam, then find where the power curves intersect between the vtec disabled run and the vtec enabled run and set vtec to that rpm.

also keep in mind that 12psi at full throttle will want different ignition and fuel settings than 12psi at part throttle (like when you have it set for 26psi).

a technique I sometimes use for street tuning ignition is: make sure ignition is set a little lower than what you know to be ideal. then datalog AF. then advance the timing 0.5 degrees or 1.0 degree at all points in that column. then datalog AF again. if the AF gets noticibly richer, then it liked the timing increase. if AF did not change, then bring the timing back to where it was to begin with. keep doing this til AF does not get richer. then retard timing 1.0 degree. you want to see AF lean out by a couple tenths. if it leans out a couple tenths, leave it where you just set it too slightly retarded. if it does not lean out, retard the timing a bit more. if it leans out more than 3/10's, then set it back to where it was before you retarded the timing at all.

the concept is that if the timing is spot on, minor changes to timing will not affect AF. but if timing is too retarded it will read much leaner than it actually would be if timing was correct because it is not burning completely. and if timing is too advanced, it will burn very hot, and actually reads a little leaner as well especially if there is minor detonation.

just be sure to stay on the slightly retarded side to stay safe

 

Wait...won't the engine want to LEAN out if it liked the advance in timing? Meaning you are getting better burn, and you stop adding timing when it stops leaning out? From what I've read this is the case.

And is the method you described as accurate as dyno tuning ing. timing? I'm going to give it a try if you say it is.


Straight from the CROME tuning Manual: ------->

...When fuel is ignited farther in advance, more HC combusts into CO2 before reaching the exhaust which passes by the sensor unnoticed, so the O2-to-HC ratio (AFR) is leaner. O2 readings become leaner with ignition advance.

 

it will lean out if the timing is too far in either direction. which is why I stated you want af to barely change at all when making a minor ignition change, and keep it at the slightly more retarded point when you reach that point.

advancing ignition too far (1 degree or more BEYOND ideal) will burn too hot and do exactly what you just stated from the crome manual.
retarding ignition too far will cause incomplete combustion leaving raw oxygen in the exhaust making it read leaner.
when you make ignition alterations, but don't touch fuel at all, ignition is typically nearest it's ideal setting when you get the richest afr reading. just stick to the more retarded side of this area.

no this method is not as accurate as dyno tuning. it will however get you much closer to ideal settings so you wont have to spend as much time on the dyno.
it works amazingly well for part throttle tuning as well. IE: just today I went for emissions testing immediately after I finished street tuning my car. NOx was too high, so I retarded ignition 1.0 degree in the 11"-18" of vacuum portion of the tune, from 2000-3500rpms. before this change, I was perfectly at 14.7 throughout that area. after retarding timing 1 degree, all of it went straight to 14.3-14.4 afr. just to verify that was ideal, I retarded the timing another 1.0 degree, and that brought afr back to 14.7 but the guage was a little jittery. tried testing like that, failed again from too high of HC. advanced the timing back 1 degree, and it went back to the 14.3-14.4. I then pulled some fuel to get it back to stoich 14.7. it passed emissions, and made the same exact HP required at a lighter load, meaning it made more power at same load, meaning that was ideal ignition setting for that point. notice how it leaned out in both directions. richest was ideal ignition setting.

 

Ok, I think I get what you are saying. I read and re-read the info you have given me. What this means that on either side of Ideal timing is a lean area. I am a very visual learner, so I put everything you explained into a diagram to help illustrate what you are saying. Hopefully it will help others too when trying to get close when street tuning Ign. timing. Check the diagram to make sure I'm understanding this right.

Anyone feel free to chime in on this.

 

wow, nice diagram. yes that is mostly spot on to what I was trying to describe.

as a failsafe though, if you advance and af stays the same, and you advance more and af still stays the same, back the timing off to where you started, to where backing it off a hair more starts to lean it out. it's not 100% consistent at all times doing this method, so stay on the retarded side.

the only thing not accurate about that diagram is exhaust temp. less timing = hotter exhaust, more timing = colder exhaust. there is no dip to it; it's fairly linear, with a slight curve to it, where: less timing = hotter, and even less timing = a LOT hotter.
and the opposite is true for combustion chamber temp which isn't pictured: less timing = colder combustion chamber temp, more timing = hotter combustion chamber temp.

and yes, anyone else who wants to chime in on this concept is more than free.

 

Ok, modified the diagram image above. It better illustrates how you described the temperature vs timing relationship.

Does that look right?

I'm going to give this method a little shot over the weekend and will report back on my findings. If I have success with it, this will really help remove some guess work/time when dyno day comes. If I can get in the ballpark using this method, I should be able to keep dyno time to under an hour, just making minor tweaks with consistent runs.

Thanks motoxxxman.

 

yup, that looks right enough
yw