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Scaling speed density scaling and optimizing tune

Practical Reflash Tuning

Discussion and questions related to the course Reflashing

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So after watching the three moduals and going through the remote dyno tuning lessons everything is becoming more clear with tuning. However, this being for more stock orientated engines.

I will be building an older g body chevy, with either the 4.8 or 5.3. I will be putting in a slightly bigger cam, porting the heads (not just gasket matching but including bowl work), and either going with a 7876 single turbo on about 10 psi, or twin 61’s on 10 psi. This application will be a street/strip set up.

So when this will also be my first car I’ll be tuning, obviously I’ll start on the lowest wastegate spring setting. Should I initially add about 5% to the VE tables all across the map and start off with 10 degrees of timing across the whole map over base?

Any help is appreciated!

Hi Damen, I wouldn't suggest retarding the timing everywhere. You'll likely find the timing at low air mass is going to be similar to stock and it's really just the higher airmass values (under boost) where the timing will drop away. You can start retarding the timing a couple degrees as you get to maybe 0.60-0.64 g/cyl and progressively pull more timing as the load increases. It's not strictly as critical as you may think because you're not going to be doing a full pull to the redline as soon as you hit the dyno. You'll be able to gradually ease into the rpm and load and develop your timing map as you go. Just start slowly and methodically and gradually increase the rpm as you become comfortable that your timing and AFR are under control.

The same really goes for your VE. You can actually expect your VE to reduce slightly at low rpm with a bigger c am, but it should increase above perhaps 2500-3000 rpm. You could take a guess at this and perhaps reduce idle and low rpm VE by 5% and then increase the high rpm VE by 5-10%. Just as with the timing, these don't need to be perfect because you'll be optimising them both.

Ok, sounds simple enough. Hmm i thought with the ported heads and cam and such even at idle it would need more, however that is true that depending on how aggressive the cam is, they will pull less vaccum at idle. So yes, I would need less fuel then to maintain the same AFR at idle.

Thanks again for the wisdom Andre!