My question is regarding ignition timing and why it is the way it is. I've had my ems for about 2 years now, so I am fairly fluent with it. I first learned to use it on my 91 teg with a B16, but fear kept me from experimenting with the tune too much. I had it tuned at a performance shop and pretty much reverse engineered what the tuner did to learn lots. I have a beater to play with now. Its a 90 teg with a B18A1 at 380,000 km's. It's pretty tired so I don't care if I blow it up. I've been playing with ignition timing and have come across something that I'm finding hard to understand. I decided to advance the timing until I could just start to hear detonation and then back it off 3 degrees. I assumed the timing would need to be advanced more as engine speed increased. It turned out peak timing liked to be 28 degrees at 3500 rpm at which poind it needs to be decreased up until the redline.

My timing looks like this:

(First number is 500 rpm. then 1000,1500,2000..... to 6500.)
5 7 10 18 23 27 28 24 25 25 25 25 25

Mods on the car are AEM CAI and a cat delete. Everything else is bone stock.
Compression test yields 190/200/195/200
I am using Chevron 87 octane fuel... This car just isn't worth premium!

My fuel mixture is about 12.7:1 to 13:1 right through the rpm range. I'm not complaining that something is wrong. I would just like to understand why this happens. I'm having tons of fun with this ems. It has brought new life to this rust bucket! I have no doubt that I am up at least 5-10 hp just from tuning it. Power used to noticeably drop off at about 5500 and the powerband was very choppy. Now it pulls nicely to 6300. Driveability is amazing and fuel economy is much better. I have spent weeks tweaking here and there on the fuel map and I'm now to the point where there's almost nothing left to do. It even starts like a new car. I hope I didn't leave out any important information.

Any insight to my question is greatly appreciated!

Thanks
Kyle

 

maybe your ignition is not synced w the distributor

 

oh my bad i thought you were having issues.

it maybe that the low vtec cam profiles allow you to run higher timing since theres less air introduced to the engine. then vtec kicks and so does lowering the timing.


try the knock features on aem.you can set the voltage limit determined by your rpm. honda ussually have the 600hz resonant type knock sensor. maybe that could be some use for you. mine knock is useless since i have a leak in the manifold from all those anti lag

try not pushing the timing there may be less or no gain. try fwombat's dyno he wrote a good dyno simulator where you can use the weight of the car as the dyno load itself

 

Thanks for the reply. The engine is a NON VTEC B18A1. A real powerhouse, actually it's really not! So it does not have a knock sensor. I guess my ears will have to do. I've been thinking about this timing thing for a while now and I think your on to something. At the lower rpms the engine is not in it's powerband and the air/fuel charge is not very dense which would require more timing due to a slower burn rate. Once I hit about 4k the engine is getting a good charge which burns faster and need less timing. I think that makes sense.

In the spring I will be using this ecu on my other teg. That one's got a B16. I want to be a familiar as possibe with this ecu before I use it on the good engine.