How does your ignition timing look like under boost?

[gezed]

Just wondering if anyone knows what their ignition timing map looks like, I know its very specific to each setup and you can never be sure what the best compromise(egt, boost, timing) is but I just want to get a general range as a reference

from what I read, rb's can handle a little more aggressive timing compared to other boosted small displacement engines

I've also read as far as gasoline is concerned, the ideal timing is around 30 btdc based on the burn rate of gasoline, a lot of it also has to do with head design and the distance between the 2 farthest points during compression. But I think thats limited by knock in a boosted application

there's also talks of tapering ignition timing when peak boost/torque hits and then advancing back to what it was past that peak

I've been doing a lot of reading on ignition timing tuning and again, I know you have to hit the dyno to know for sure but I just want to know what everyone is working with. I played with the timing a bit and have been very careful, the absolute highest knock reading I've seen is 18 and afr is steady 11.3-11.8 under boost(8-10psi)

[Skym]

BTDC is the base ignition timing via CAS (say 15 degrees BTDC for manual RB20DET or 20 degrees BTDC for auto RB20DET and I think RB26DETT as well) and ECU adds ignition timing to that figure via ignition map cells to get ATDC where it fires the sparkplug on 1st cylinder, then in sequence on other cylinders.

From what I understand, pulling ignition timing is close to when engine reaches peak volumetric efficiency (peak boost, peak torque).

From what I understand, ignition timing can be adjusted until torque and hp won't rise anymore and before knock occurs and then pulled back a bit to give a safety margin (race gas and race engine). That can vary between engines due to compression, fuel octane, intercooler like bar n plate or tube n fin, size (affect's intake temps). A good tuner for road use, reliability (factory for example) will add a little bit of ignition timing (conservative tune) which gives roughly half the hp you can extract and stay in high 10's for 100% reliability or low to mid 11's and sacrifice reliability a bit.

To monitor knock, headphones, etc is best. Don't rely on knock count only.

[Dragon Humper]

FWIW I am at 30 to 32 all the way to redline, for some reason the comander is telling me that even though the map has it at 18 to 20. I double checked it with a timing light though and the reported timing is actually showing up on the balancer. Baseline is at 20 deg. I also pulled 2 deg out at peak torque so I can run pump 94 up to 1bar with no change in my knock counts. She pulls effing hard at only 1bar.



Jon.

[gezed]

thanks for the replies guys

30-32deg seems like a good place to end up, for now I'll try slowly increment it
what you're ultimately after is peak cylinder pressure at 10-15deg atdc and thats when you get the most out of the engine

Skym, whats this headphone you're talking about? it it a lot better way to monitor knock?

[Skym]

Headphones that are used by tuners to listen for knock (used with HKS Knock Amp, Link KnockBlock, etc).

HKS Knock Amp (add headphones) -

http://www.hks-power.co.jp/en/products/electronics/monitor/af_knock_amp/index.html

Link KnockBlock -

http://www.linkecu.com/products/TuningTools/g4-knockblock

[Dragon Humper]

And I must emphasize that I have a VERY strict limit on boost (.9 to 1bar) on pump 94 with that timing map. Even then I will add some octane booster (Tolulene) if I feel that outside temps or my style of driving will light up the knock sensors. I also run a MAP only system and have a much better idea of how much load is on the engine and pull some timing out right at about 5-7 psi, I'm at 34 to 36 deg up to that point, that's why my spoolup is so good with such a HUGE turbo.

On race fuel at 1.4bar, its freaking epic how much it pulls, I run toe to toe with litre bikes.



Jon.

[gezed]

Jon, is that with a T88H-33D?

If thats the case I'm sure at 1bar that turbo is pushing wayyyy more air than my -7's can at 1.3bar or even 1.4bar and at the same time, the bigger turbo will be way more efficient as well which means cooler charge temps which means you can run a more aggressive timing, I'm going to try to hit 30deg give or take and see where to go from there based on the knock readings

Thanks for the info guys, gives me a better idea of where to start

[Dragon Humper]

Yup, big hairdryer hardly breathing at 1 bar. Intake temps rarely get more than 15 deg above ambient. She actually gets most efficient at 1.4 to 1.8 bar on a 2.6L so that plays a huge role along with the 4" thick intercooler.




Jon.

[Black BNR32]

I posted my maps a few weeks back...search