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Safe ignition map for build rb25

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Hello my name is Kenny,

I have rebuild my rb25 with forged components at home, it wil be running a holset hx40 on 98 octane fuel aiming for about 600hp using a link g4+.

I need help with creating a safe ignition map purely from experience for me to tune the fuel map completely without worrying of encountering knock but still driveable.

I will hire dynotime and a audio knock monitor to finish the final parts of the tune, but i want to spend as little time on dyno as possible because its very expensive.

Therefor i want to have 90% of the tune complete on the road. But i dont have enough experience to know what my engine wants for ignition and when it encounters knock.

Maybe there are some people here that are very experienced with rbs and can send me in the right direction.

Any help is very much appreciated and im eager to learn!!

Kenny Spros

Attached Files

Hi Kenny, unfortunately asking for advice on a safe ignition timing table is fraught with problems. The issue is that even with an engine that i know intimately well like the 4G63, I still see variations that can be quite significant from one engine to the next, even when on paper the build is identical. For this reason relying on a supposed 'safe' map can be potentially hazardous. I would personally suggest you start with conservative timing and then use your audio knock detection to get this dialled in on the road. The RB25 in my experience is going to definitely be knock limited on pump gas, and they don't take a lot of timing around peak torque. I'd start with a timing map with around 35 degrees at 4000 rpm and above in vacuum. I'd taper this down to 15-20 degrees around 100 kPa and then by 1 bar of boost I'd pull that back to 8-12 degrees. That should be relatively conservative to get you up and running and then you can experiment to find what your specific engine wants.


I know this. I am not looking for this "geused" ignition map to make max power but to be driveable enough for me to tune the fuel map on the road without hurting the engine.

I can only use the knock monitor when i have rented the dyno. Would you consider these conservative timing values you mentioned to be okay for me to tune without audio knock or is this not recommended?

If so i might need to reconsider my strategy of how i am gonna do this