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Base Idle Timing / Timing sweep / total timing

EFI Tuning Fundamentals

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Discussion and questions related to the course EFI Tuning Fundamentals

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Timing questions. Thanks.

When Building a timing map from scratch and a first timer.

I thought asking Few questions in advance of detonation is smart (lol).

Base idle timing or base timing- where do I start as rule (if any) for a safe base idle timing.

What is safer 10 or 16 before TDC?

Do I select my base idle timing off of my engine idle quality?

Or MBT?

10-16 degrees range?

Total Timing or amount of timing sweep added to base timing for total timing?

Is there any basic guidelines

To total timing sweep?

Add 20 degrees to base idle if no eddy dyno for MBT available?

Is timing sweep RPM based?

More RPM add more sweep?

Whats max rpm you can MBT timing

on eddy dyno?

"Car at 9000rpm should have 10 degrees more advance than at 6000rpm?" Any rules As an example before MBT?

Eddy dyno and MBT is applicable only when?

When is eddy dyno MBT not applicable?

If I MBT the car up 6000rpm- can i draw a correlation from the data to 6000rpm to build the rest of the hi rpm timing map? 9000rpm application as example.

Car has a glide/5500 stall installing a GT42 style turbo and is a 10.1hcr "Flex fuel e98" is planned built for hi rpm.

Mech pump 16v charging 2200cc at 43.5 13.8v

Thanks

When I use the term 'base timing', I'm referring to calibrating the ECU so that the timing on the lap top matches the timing I'm seeing at the engine with a timing light - I always feel it's important to clear that up first :)

Ok as for idle timing, there's a pretty wide range that the engine will happily idle at. Most often I will end up in the 10-18 degree BTDC region (You're not going to do any damage to the engine by over advancing the idle timing by the way). Normally I'll use idle ignition control to help stabilise the idle speed and for this to work properly it requires the normal ignition timing to be somewhat retarded from MBT so that the ECU can advance and retard the timing to affect engine torque.

The amount of total timing will depend on the specific engine, the fuel and the compression ratio just to name a few aspects. I don't offer a 'rule' as such but rather just find out what the particular engine I'm tuning requires by testing. There are two trends going on:

1. As rpm increases there is less time available for the combustion event to take place so we need to advance the timing in order to achieve MBT.

2. As airflow into the engine increases the combustion event tends to happen faster and hence we need less ignition advance to achieve MBT. These two trends are constantly in action as we move around the ignition table in terms of both rpm and load.

You can steady state tune ignition timing at 11,000 rpm if you really want to (provided you can control the engine temperature). There's little point though as we don't use the engine like this. I try and use the dyno to replicate the way the engine is being used and generally I'll tune in steady state up to about 2/3 of the rev limit and tune the remainder using ramp runs.

If you haven't already looked at it, I'd strongly recommend our practical dyno tuning course. It covers everything you've asked here plus you get to watch the process being applied in several worked examples..

Big Thank you.

I will do that.

Ty

Thanks.

Yes i copy pasted my question and asked it in another forem and got good info there too. I have watched and completed the info below - but i mist repeat because i had these questions afterwards. I plan on reviewing the data and learning more 2nd time.

Ty

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