Spark Ramblings
 

Background:
I was reading a topic on another forum and one particular post by an engineer who works for Ford Australia caught my attention. This engineer spends most of his days doing; "My day gig is performing OEM engine power curves, and VCT engine developement, among other things".

One of his points that I found really interesting was; "One other point...pay attention to spark...this is MUCH more important to power than fuel. Everyone tosses off about 12.5 AFR (lambda 0.85), but never does spark loops to find MBT optimum spark!!!!!!

Going 10% rich on fuel might lose 2-3% power at the most, but 2-3 degress of retarded (or over advanced!!!) spark around pk tq or power will cost you 10% or more!!!! You could run a carby, and digital mapped ingnition, and make nearly the same power....this is where most of the gains in engine output have occured...optimising the spark at ALL engine operating points (non knock-sensor engines are generally 4 deg away from optimum already, to allow for variation in engines, drivers, etc)...and it gets worse the higher the CR!!! But show many any tuner who spends much time on spark loops????? Coz customers only want to pay the time for AFR mapping, getting that magic 12.5 AFR!!! Most modern engines i know make more power down in the 10's AFR...manufactureres aren't silly you know!!!! That's why so many cars run down there, but if you don't do the loops to optimise ALL parameters, you'll never know, ya??"

Spark Research
My next step was to have a proper read of "Mazda Miata Performance Handbook" by Norman H. Garrett III. In the chapter on ignition Norm mentions some facts about ignition advance for a 1.6 NA. The first was that 20% more torque can be found at 1000 rpm by advancing the ignition to 18 DBTDC. His second interesting point was that a stock 1.6 NA will go from 90.7 HP to 99.5 HP with an ignition advance to 14 DBTDC. He also had a graph representing a timing map of a stock 1.6 NA at WOT. This graph started out at 0 DBTDC until well over 1000 rpm and ended up at about 27-28 DBTDC at 7000 rpm.

Spark Experiment 1
So with this information in mind I decided to play with the spark settings that I had developed from the FM Link settings. My first step was to increase the settings on the spark table at the low rpm/low MAP area. The table is attached below.

I went for a drive with this table loaded into the MS and I felt a definite improvement in the low down torque. Prior to this change my car was a little hesitant in situations where I was accelerating from low speed such as after the car had gone over a speed hump. With the spark changes the car was much more willing to accelerate at these speeds.

The rest of the spark table was left unchanged.

Spark Experiment 2
I had previously downloaded an excel spreadsheet that gave the fuel and spark tables from the OEM 1.6 NA computer. This table was running at 10 DBTDC so I used this table to develop a hybrid spark table of the OEM 1.6 spark settings at 18 DBTDC for all of the values below 5000 rpm and the settings at 14 DBTDC for everything over 5000 rpm.

The table is attached below and you can certainly see the differences to the FM Link table. I drove for about 30 mins this morning using this table and it felt different to the FM Link table. The car accelerated in a different manner. With the FM table it seemed to be a great rush of speed and the car felt like it was going flat out. Now it seems to be more of a progression of speed, with the car less fussed in it's urgency but the thing is still accelerating really quickly.

Conclusions
Well the further advance at low rpm/low MAp values is a definite improvement to the FM spark table that I was using.

The new hybrid 18/14 DBTDC table based on the 1.6 OEM map didn't give any definite improvements over the first experimental table but I am really interested in getting the car on a dyno and running it with both maps to see if there is a torque/HP difference between them.

And the main point that probably isn't as obvious is that the BP engines seem to be pretty resistant to knock which is good for us to try and optimise the spark tables for our different applications and as my experiments have shown me, the spark table changes certainly can make for a more powerful and more responsive car.

Steve

Thanks for the interesting post Aussie! As I read about tuning in general I was susprised too to find that spark was so important for torque. I always focused on what fuel ratios should be.
Further reading has convinced me to want to run water/alcohol injection. I figure since I use a fairly tiny turbo (td04h-15g) could stand to have the intake air cooled. Also a nice benefit is raising the effective octane of the crappy 91 fuel we have in California. This would let me run with much more advance and combined with knock sensesing should be fairly safe. Water injection is so cheap I dont see why not?

Nice work! I guess a lot of it depends on what fuel you are running too. Obviously you'll get more advance safety margin out of Shell Optimax or BP Ultimate, and the stock fuel map was probably even considered conservative for standard ULP.

Interesting read!!

Seem to be a nice little experience..

So what table did you settle with?

Very interesting, thanks Aussie, I'll be keeping your post in mind when I attempt ignition this weekend.

Thanks for the feedback guys!!

I've still been mucking around with it and I've decided to run a hybrid version of the modified FM spark table with the Experiment 2 table. I'm pretty happy with the way that it's currently going and I would be really interested to hear of your thoughts on the way that it runs if you want to try it on your cars.

BTW as saboteur has indicated, I'm running Shell Optimax (98 RON) in the car and this could be the only reason why I haven't experienced and knock with these tables. So a word of caution if you want to give any of these tables a go. If you hear any rattling ball bearing type noises coming from your engine, get off the power immediately!!!!

Steve

Any tips on building a spark map for a turbo?

Go to the FM site here and download the latest version of the Link Tuning Manual. On page 23 is a picture of their ignition table. Copy it into MegaTune starting with the 20kpa row, then leave a row, then do the 60kpa row and then leave a row, etc.

Once you have done that make your first empty row 40kpa and then add the values above and below each blank value in the row and divide each one by 2 to get the middle value to insert into your table.

Do that for each rpm value in all of the empty kpa rows until you fill in the entire table, then divide all of the numbers by 4 to get the actual degrees. That is probably the best starting point that you can get.

Steve

Good info!

FWIW:
On my EM I set all the ignition values to advance 8 degrees in vac, 0 @ 0 and then retard a little extra in boost.
Also the MP3 ECU(P5) runs a more aggressive timing map then the stock P5, why it has a higher rated HP, and is not a boost friendly stock ecu over the stock P5.

Just to give you an example on the dyno of what Aussie is talking about. I had a mustang (65 fastback, K code) come in for a dyno session. I adjusted his timing only and picked up 50 HP. Needless to say, he stated that was the best $120 he ever spent... and all I did in the end was advance the distributor 4 degrees.

4 degrees, 50 HP. You can definately feel 50 HP seat of the pants.

Mark

wow thats pretty crazy.
Hey I just realised you are MarkP from miata.net :) welcome.

I also did a dyno tune on a Cobra with a 427 cu in SBF - and picked up 30HP by RETARDING the timing about 5 degrees. So optimal timing is important - more isn't always better - don't just advance until it knocks and then back off until it doesn't - use a dyno and use the least amount of timing that makes maximum power in that cell.

ill agree with that corner weight....
when i tuned my turbo we got to a point where advancing the timing stopped making more power even though there was no knock....
so we decided to smooth the fuel curve out a bit more and call it a day.
one thing i did notice was that with leaner mixtures the ignition timing made a bigger difference in power over the rich mixture.

my next tuning session ill try and get it leaner and see where i can get with timing.