TPS or MAP for ITB Ignition Timing Load Axis

Hi all,

I'll be putting an ITB setup on my MX5 in the coming weeks and despite all the research I've done I'm not entirely sure on how to set up the ignition advance table.

If i set it up with TPS as the load axis, would the cell spacing need to be tightly grouped around low throttle postions like the fuel table?

Alternatively, if it was based on MAP, would the timing map from the when the car had the stock intake manifold be mostly appropriate?

Thanks in advance.

Yes, use TP for the load reference for both the fuel and ignition tables. The axes should be set up similar with fine breakpoints at small throttle openings. I normally do something like 0,2,5,8,11,15,20,30,40,60,80,100%.

MAP wont work well as you will find even at quite small throttle openings MAP will be quite high and for instance wont show much difference between say 30% and 100% throttle.

Thanks for that. I thought that would be the case however the very few ITB ignition maps I've seen online had MAP as ignition load.

Good to know I was on the right path.

In terms of figuring out a base map for the ignition, are there any rules of thumb to follow? Its hard to know where to start without being able to look at examples, which are commonly available for speed density situations.

This is the closest I have to a road car ITB ign table. This was relatively high compression on pump gas so maybe a little more conservative in some areas than you might get away with.

Thanks for that Adam. Thats very helpful and makes a lot of sense.

Hey Adam, I'm facing these exact same issues, the picture you uploaded in this thread has been removed, can you please reupload it? would help me out massively!

I'm hoping for that repost as well

As previously stated with ITB's, TPS is the way to go for a load axis for both Ignition and Fuelling and they should share common break points. There should also be a compensation table for both based on MAP to take barometric conditions into account.

Regarding ignition advance values there are no specific considerations for ITB's and it should be calibrated to chase MBT with a couple of degrees of safety.

this course should help you have regarding calibrating the ignition advance: https://www.hpacademy.com/dashboard/courses/efi-tuning-fundamentals/the-tuning-process-tuning-ignition

Here is the pic that was attached above. It was more as an example how to set up the axis breakpoints for ITB's, rather than an example of timing numbers...