timing maps

[cadet18]

Im trying to get a hold of how people set up their timing maps. i would rather learn how to set it up than to just get a timing map from someone. i get that you take away a degree for every pound of boost, but is there anything else you guys know of. Maybe you add a certain amount to the upper side of the map right off the get go? I dont have knock ears available to me now but i can log my knock sensor. Any explanation is greatly appreciated. dumb it down as much as you want. I'm here to learn. I plan on running no more than 20 PSI. Ill probably stick to around 17-18 on my 2860rs.

Thanks

[Buddyworm]

The whole remove a degree of timing for every pound of boost is really just a rule of thumb. Problem is engines don't care about rules of thumb. It may have been developed in a region with different octane ratings than you, at different elevations, at different temperatures, on different intercoolers, different turbos, turbine A/R's, different fuel injector spray patterns, coil packs, etc. It's all going to affect the burn.

The ultimate question is how much heat are you building up in the combustion chamber.

There are so many variables that need to be taken into account and it's one of the reasons I don't recommend canned tunes, even though Enthalpy has a good rep.

The CA's knock feedback is next to useless. There is only one way to KNOW, and that's to steady state that sucker on a dyno with a proper knock monitor and run er good and hot.

I would be extremely leary about tuning an engine to 20psi on the street without any kind of proper knock feedback.


Back in the day I did it 32* advance at 0 vacuum, retarding one degree for each PSI of boost and it served me decently well at 14psi. Until 4th gear clutch kicks were tried towards the end of some extended drift runs. Engine made a loud backfire, puff of smoke out the breather AND the exhaust, it never ran the same after. Found cracked ringland on teardown.

[float_6969]

Honestly, timing maps are the hardest part to tune. Not that it's actually difficult, but because the correct timing has a HUGE impact on the reliability and how much power the engine makes. It's also REALLY variable. You can build the same engine twice, and it won't take exactly the same timing values.

As Buddyworm said, a ROUGH timing map can be built based on generic numbers, but a timing map like that shouldn't be something you go and run up to 30psi and do a bunch of drag races with. It's something that lets you drive the car around enough to break the engine in at low boost, break in the clutch, etc. all with the intention of taking it to the dyno ASAP.

A generic safe map is at low load and RPMS (basically idle), set the timing to 15°. I would then gradually increase the timing to 30°by about 3,000RPM. 32° is a common target timing value, but I've found the CA seems to have a comparatively fast burn combustion chamber and so it doesn't seem to need as much timing. This is also a safer value. I also haven't found any need to start retarding the ignition timing until about 3 psi. Then 1°/psi of boost is a rough starting point. As I said before, don't worry about trying to tune much past your wastegate pressure, as you should NOT be running the engine past wastegate pressure anyway.

[mdb4879]

Time on a loaded dyno is really the only way to do it. You can do alright on something like a Dynojet, but you'll only be able to optimize the WOT part of the tune. It's difficult to tune part throttle without a loaded dyno. The reason being that you need the dyno to see where you make MBT (Mean Brake Torque/Maximum Brake Torque). People like to go to the knock threshold then back off 2° for safety on a street tune. This works alright, but you don't know if you're making the best power or not. You might make MBT with 7° retarded from the knock threshold, and anything more than that you're losing power and making it less reliable. On the other hand, you might need more timing to make MBT. This would make 2° retarded a good choice, but you don't know that if you changed to a better fuel you could make more power just as reliably.

So a question I have which may be useful for the OP, when getting ready to tune is it safe to street tune the AFR's on the factory timing map to save time and money on dyno time by primarily adjusting ignition timing there and only having to make small tweaks to the AFR's? Or would it be a better idea to create a different base map to start with?

[float_6969]

I ALWAYS do as much tuning on the street as possible, but even then, you can really only tune the fuel maps. The only way to correctly tune timing is on some sort of load controlled dyno. These types of dyno's will allow you to optimize part throttle tuning, which isn't possible on an inertial dyno. That being said, part throttle timing tends to be more forgiving and the range of timing values that will provide near-optimal performance are broader. Also, at least in my area, finding a load controlled dyno is much more difficult. So far, it's actually been impossible for me. All of the shops around here have Mustang or Dynojets.

[Buddyworm]

Actually mdb4879, the correct definition of MBT is Minimum timing for Best Torque. Which, as you seem to understand, is the minimum ignition advance beyond which the engine will produce no additional torque.

If an engine is "knock limited" on a given fuel it means you will hit detonation under certain conditions before you reach MBT.

The CA18DET is definitely knock limited on pump fuel.



To answer your question mbd, you can get a great deal of your fueling done on the street prior to the dyno session, but it's tough to say what a "safe" advance is at higher boost. Not only that, you might find it difficult to dial fueling in on the street as the engine will sweep through multiple load cells quite quickly, and once you get it on the dyno in steady state your fueling might not be all that accurate anyway.

Expect to spend a good chunk of the day on the dyno if you're tuning an engine from scratch.

[cadet18]

awesome info guys. ill do what i can before a dyno day. im glad to have some experience chime in on this. also do we know that actual correlation between filtered and raw timing values for those of you familiar with nistune. ive heard subtract 22 degrees from the number and i have heard subtract 16 degrees from the number. i never could find a solid answer on this. just want to make sure im doing this right before i start messing with stuff.

As always thanks guys!

[Buddyworm]

In Nistune filtered is the actual timing advance the ecu is outputting and should line up with the crank pulley when using a timing light.

RAW is how the ECU deals with it internally.

[Izento]

Also, at least in my area, finding a load controlled dyno is much more difficult. So far, it's actually been impossible for me. All of the shops around here have Mustang or Dynojets.

Mustang dynos are load or eddy current dynos. Dynojets are inertia dynos. Dyno Dynamics are also eddy current.

[cadet18]

heres what ive got. criticism welcomed

[Buddyworm]

Looks like a generic "base" tune there cadet.

12deg is likely going to be too hot for the 3000-45000rpm range at 20psi. Maybe even in the upper rpm too.

I have no idea what a "safe" value will be though. The proper way to do it is is to start very retarded, like 4deg advance depending on boost level, and add timing until it stops making more torque OR you encounter knock.

Again, if you're going to do this yourself you NEED a proper knock monitor. Plex Tuning makes an excellent one. It will go a long way to keeping you safe.

[cadet18]

ill def look into plex tuning! might have to make a road trip one weekend, as i have access to free dyno time. just have to drive back home to NC to get to it. (6hr drive) I just want it safe for now as i prefer to drive the s13 to work everyday if i can. the truck isnt nearly as satisfying lol