miatauser884

iTrader: (11)

I must say that I was a little surprised by the sensitivity of the elec. det cans. It concerns me that dyno operators don't seem to use this type of device as common practice. Tners seem to base it on audible knock, what has worked on "Other" cars, afrs, or whatever. No hard evidence from my experience. So, if we consider every car different, then shouldn't professional tuners be using some kind of knock detection device during tuning???? Point being, at what point do you trust that your spark table is 100% safe?

Moving on......Is there a level of detonation that is really inconsequential? It's so low level that it isn't really doing any damage? Like a bird wiping it's beak on a 1 sq ft marble block.....one day a bird could wear through it. To most though, "It's not going to happen." is a pretty fair statement.

IF there is a "safe" level of detonation, are our knock sensors and det cans sensitive enough to detect it? In the past we worried about audible knock. Now here I am tuning out the small tic noises I here in my det cans. As I lower the timing in certain cells, I start hearing noticeably fewer ticks until they are nonexistent.

If the above is true, then it is reasonable to assume that tuning the spark table with det cans will result in a 100% safe spark table with a margin. That margin being the low level non threatening knock. My limited experience suggests that there is quite a margin between no knock, and the audible knock that is assumed to kill engines. Hell, there is a wide margin between no knock and a lot of knock in the det cans.

FYI: My flickering oil pressure gauge corresponded 100% with the detonation I heard with the det cans. No detonation, no flickering gauge.

I would like this thread to be a place for people to post their timing maps with reference to how it was tuned.

Mine started as a combination of many maps I found on MT.net, dynotuning, then finally I tuned the boost cells with the electronic det cans.

Post your spark table, and state if it was tuned with/without a knock detection device.




Electronic det cans from past group buy

Matt Cramer

We occasionally use det cans while tuning, but we've found Miata engines often let you run way more advance than will make good power before they start knocking, so I'm not sure how much det cans contributed to the map currently on our test car.

A case in point: You're running about 10 degrees more advance at 100 kPa than what we found makes good power in that area. Looks like that map started out as a small block Chevy map and had some areas tuned for a Miata, but it looks like the high RPM / 100 kPa or more were not.

18psi

iTrader: (76)

Pretty conservative at 180 and 230 IMO

hornetball

iTrader: (4)

I've only just gotten mine together. Haven't been to the dyno yet. However, when I do, I plan to bring along a homemade det can.

I plan to do most of my fuel tuning ahead of time with MS logging and wideband (AFRs to be confirmed during dyno runs). My dyno session will be dedicated to spark tuning.

For each target RPM and MAP, I'll shoot for the lower of MBT or 3°(?) away from detonation. As Matt pointed out, I would expect most cells to end up being MBT driven. I think it is a mistake to spark tune only based upon detonation margin. You also need a way to monitor your torque and identify whether you've hit a peak.

Braineack

iTrader: (62)

similar ot what I'm running, but like Matt said, that's more advance at 100kPa than most typically run.



spark 3 is my map when the A/C is on.

miatauser884

iTrader: (11)

I was hearing the knock around the interface of the 230kpa and 300kpa rows, so I pulled timing from both to lower the average between the cells. I really have no clue as to what timing at 25psi should be. I bet if I lower the 300kpa row more, I could put more back in at the 230. The area below 100kpa stems from my 440 tuning. I can lower the timing in the <100 kpa rows and it doesn't feel like it makes any difference.

So, i fit doesn't make any difference, is it best to run the minimum advance necessary?

The thing is, how much is a couple extra degrees of timing really going to make at 12 and 15 psi? I lowered the 180 kpa row as a little bit of safety. I may see what happens if I start adding back a half degree at a time.

I guess I should lower my 180, 230, and 300 rows to very conservative, and just add in slowly to each.

18psi

iTrader: (76)

This is why you need to tune spark on the dyno: so you can see exactly how much a degree or two will gain. Once you stop gaining there's no point in upping it more.

My car definitely gained a big chunk of power with 3* increase at 200kpa.

miatauser884

iTrader: (11)

My point is this: I have a professionally dyno tuned map. He looked for where the car stopped making power and backed off slightly with the timing.

This map causes my oil pressure gauge to flicker, and I can hear detonation with my electronic det cans. When I back the timing off to where I hear no det, then the gauge stops flickering.

I don't think the method of "increase until you don't gain any power", and then back off slightly, necessarily means that there is no detonation.

18psi

iTrader: (76)

Oh of course. By no means was I implying that you should advance regardless. Obviously if you see even the slightest hint of knock you need to back off 1-2*

Ben

iTrader: (33)

So are you adding timing until you hear knock while driving? If so, then you will need to remove several degrees from where you heard knock. Every setup is different, but we usually see a notable drop in torque on the dyno before we can hear knock.

If you want to do it right, tune your spark map on a load dyno.

miatauser884

iTrader: (11)

This is my spark map tuned on a load dyno. OP gauge flickers and I hear det in boost between 180 and 260 kpa

Is everyone suggesting that since it was tuned on a load dyno, and the timing was increased until it stopped gaining torque that this is a good tune? I should ignore the detonation that I hear in the det cans and ignore the flickering OP gauge which corresponds exactly with the det I hear in the det cans??

18psi

iTrader: (76)

Going from 10.3afr 16* 14psi to 11.8afr 19* and 16psi I went from 263/239 to 307/287. car is on e85 so it doesn't even know what knock is.


edit: your previous 17* @ 230kpa on pump is definitely pushing it a bit. I'm not surprised you're seeing a little knock there tbh

miatauser884

iTrader: (11)

My current logging and listening suggests that the advance in the 180 kpa row wan't causing any problem, even at 19*. It's the 230 to 300 rows. I've got limited resolution so I can run really weak right at 300, or split the difference.

I just thought about that for a sec. I should run really low at 300 since my target is only 270.

What seems reasonable at 230? 30* seems to work.

hornetball

iTrader: (4)

No. What we are suggesting is that if you tune ONLY on detonation onset, you will often have advanced beyond MBT.

Your tuner did a lousy job if he left you with a car that detonates.

You should tune for an advance setting that is the LOWER of MBT or a safety margin away from knock. MBT can only be determined on a dyno.

hustler

iTrader: (6)

I made this table and tested it with the manifold glowing yellow with a 3000-7500rpm pull on the dyno:

I also recorded the det-can music on my mp3-player at TWS where my car goes up to 156mph and heard no knock. I'm also on a low compression engine.
The 156-180kpa shift is pretty drastic, but that's MBT-3*.

hornetball

iTrader: (4)

Why (MBT - 3°)? You need a safety margin from knock, but not from MBT. ??

hustler

iTrader: (6)

Because I assumed that MBT spark angle will change with heat soak and rolling it back further considering things like hanging the tach at 6000rpm in 6th gear every lap for 45-minutes.

miatauser884

iTrader: (11)

I know there is a thread on MBT, but refresh me on how this is determined on a dyno. The tuner increases advance until he increased it until nothing changed on the dyno. Then dropped the advance to the last point where a gain was made.

18psi

iTrader: (76)

Pretty much.

miatauser884

iTrader: (11)

Ok, I found the thread where Hustler was talking about MBT.

https://www.miataturbo.net/showthrea...&highlight=MBT

It sounds like the tuner found MBT while on the dyno under the conditions at the time.