Aftermarket EFI Map questions

[schmaz356]

I'm a little new at the 911 EFI but I'm learning.

I have a 914 with a newly rebuilt 3.0 from a '78SC. It is single plug and has JE 9.5 pistons and a 964 cam. As for the EFI, I have Clewett ITBs and a Haltech brain that operates the EFI and spark.

I have searched the forum and can only find suggested fuel and ignition maps with the TPS being the axis (along with RPM). I was wondering if anyone has any suggested maps with RPM and Manifold Air Pressure. If anyone out there has these it would be very helpful to compare to my base map. BTW this is a street car so nothing too crazy.

Thanks.

[Dr J]

For ITBs the way to go is TPS vs RPM

[spuggy]

As Dr. J says, you might be better off with Alpha N (TPS) vs RPM; seems to be more conventional for N/A.

However, MAP vs RPM is the only game in town with forced aspiration - so there's a bunch of MAP-based ignition maps on the 930 sub-forum - should be able to just use the values from 100kpa and below.

Here's mine FWIW: Motec, 3.4, 8:1, SC cams, twin/COP.

IIRC, basically a 3.2 map with factory on-boost numbers and some jiggery-pokery to keep it in the "hole" at idle without an IAC.

MAP fuel maps are (or should be) pretty flat, so once you've got it running shouldn't be too big a deal to dial it in around your desired lambda value(s)..On the Motec, you can tweak accel/downshift etc enrichment compensations separately from the main (steady speed) table.



Most of the fractional values are either from interpolation, or in corners of the map can't be reached, at least by me - eg 1.4 bar boost below 2000 RPM? Not gonna happen without a supercharger...

[Dr J]

I recommend you watch this video. The information is useful regardless of the EFI system you use.

https://www.youtube.com/watch?v=_GDZxUVTplk&ab_channel=AndyWhittle

Also, this thread may be helpful:
The official EFI Ignition map sharing thread

and this one is a must read.

EFI Tuning - How to Process Description

[r_towle]

Where are you located? Might be a good tuner in your area.
Also, ask the same question on 914World , you may find other DIY guys doing this.

Last guess, PMBPerformance is doing aftermarket FI now. They may be helpful.

[targa72e]

As others have mentioned MAP is not the best as the primary input with ITB's. With ITB's there can be a very large change in MAP values with very little change in throttle position. This can make tuning difficult. This is the reason that throttle position is often used as the primary reference with MAP as a secondary or blended reference. MAP works much better with a single throttle body or with forced induction.

john

[Showdown]

All you have to do is scale your VE table appropriately and you can most definitely tune ITBs to MAP.

For that matter, you also have to scale your table if you’re using TPS… neither is fundamentally better than the other; they’re just different and each have pros and cons.