4G63 Low Adv numbers

I’ve been tuning my Evo 8 MR on Maxxecu and I’m amazed at low low the timing numbers need to be on these engines! I am approx 7 degrees at 1.0 bar @ 5000rpm and as low as 2 by the time we’re upto 1.5 bar. At first I thought I had my base timing incorrectly set but this has been checked & verified several times, even at sub 10 psi (G25-550 turbo) at moderate rpm I can run into knock very easily.

I’ve learned that this is normal for a late Evo but wondered why! Is it because of the bore to stroke ratio?

Engine is 8.5:1 cr

272 cams on stock head ports etc

Uk pump fuel - shell 99 octane

Smallish turbo

Very low charge temps - IC fairly big

3 inch exhaust

NGK 7 grade plugs now onto 8’s

Have you verified that the timing doesn't change with RPM? When setting the base timing (with a fixed timing), rev the engine and make sure the timing isn't changing with RPM. If it does, it could be an ignition delay that needs adjustment or perhaps an edge polarity on crank sensor setup.

That's because of cylinder head design. Evo's head design is very efficient in terms of mixing air and fuel (good combination of swirl an tumble) that makes it very homogeneous and allows to compress it and ignite late on compression stroke to burn af mixture very fast which helps two things: less power loses during compression stroke and lower knock threshold since af mixture burns fast and evenly. Toyota and Ford repeated the same thing on their modern small displacement engines and it gave them additional 20-30 hp just by optimising mixture burning rate.

But you are 100 percent correct, ignition timing values usually are very small comparing to other engines and can be even negative depending on the engine load and RPM.

David Ferguson - I am starting to think the same in terms of ignition delay. Very good point

What is your current ignition timing map? If you can post it I'll tell you if it's ok or not.

7 degrees at peak torque 4200 rpm then it ramps up to 15 by 7500.

since I posted this I’m stating to wonder if ecu is picking up false knock , I have a twin disc, the floater plate makes a good bit of noise, I’ve tried pulling the timing back and still picks up noise.

What's the boost at 4200 and 7500 RPM? What is fuel octane rating?

Georg1970 sorry I didn’t realise you had replied!

Charge pressure is 260kpa @ 4200

and 265kpa @ 7500

I am running the highest octane pump fuel that is available to us in the uk, I’m not sure if the octane rating Carries over to wherever you are but we know it as 99 Octane and Shell V Power 99. There is 101 octane available but it’s well known to be unstable in terms of rating and quality so most of us use shell 99, without going to race fuel or E85 it’s the best we can get unfortunately/

Im not sure if these other things will be relevant to your question but I’ll included them anyway,

At this time of year my Air charge temperature is 19 degrees C (taken from a datalog relevant to this thread) I’m using a fast acting and correctly calibrated KaNtc2 sensor (insane levels of response!

My intercooler is 167% larger than the already fairly big stock interccoler.

Turbo is a Garrett GTX2867 Gen2 with a .72 Tial housing, tube manifold from a respected supplier/fabricator , Turbosmart 45mm Hypergate, 76mm inside diameter exhaust system.

Stock Evo 8 intake manifold fitted with a 76mm Bosch E throttle body, the transition between the 2 have been blended as best as possible. Intake tube is a simple 90mm mandrel bent tube and K&N cone filter in a sealed box behind the passenger headlight, I put a lot of time into this box -2 layers of sheet metal aluminium, with heat barrier sandwiched in between and the usual Funk Gold self adhesive heat reflective tape on the outside, air is fed up from outside through a void in the body work.

The reason I’ve added in particular specs of the intake & exhaust is I know that poorly designed setups can cause issues & then invite knock.

Thanks