Fuel map - CP cam?

[JohnC]

HI brains trust,

Would anyone with EFI on a car with a CP cam be willing to share with me their fuel map please?

I have a wide-band AFR sensor on my car, which still has Lucas PI. It's set up to give almost exactly the fuel delivery for the TR5 as specified in the Lucas PI Manual, but I'm not happy with the AFR outcomes - it's much too rich at idle, and somewhat rich at mid-range throttle openings. Before I fiddle with the datum track and screws I thought it would be a good idea to see what a really good fuel map looks like, rather than the approximation that's needed for the mechanical PI. I realise that EFI uses more inputs than just RPM and manifold vacuum, but I'll work that out.

Even if you have a different cam, anything would help. My car has a gas-flowed head and intake manifold, so it's not entirely standard anyway.

Cheers,
JC

Edited November 9, 2020 by JohnC

[CK's TR6]

If you mean an AFR map that is one thing, a fueling map could be construed as the VE map as that is the basis for the fueling computations.  On my EFI, you set up a AFR map, then the software adjusts the VE basis to achieve the desired AFR.  For idle, I picked AFRs around 14.5-15.0, for WOT I picked 12.0 AFR as best power is at 12.5 but I am batch fired for now so that requires a richer mix, as for mid throttle (mid Manifold Absolute Pressures) I picked around 13.0 and then at low MAP values I go up to 15.0-16.0 (this is the overrun condition). Now, from what I was told, I can linearly correct my VE map back to a 14.7 AFR standard using a ratio computation, and that VE map would be the actual VE of the engine.  

[JochemsTR]

John, you are looking for the VE Tables?

Just how it looks or actual numbers?

I changed from EV6 (229cc) to modern EV14 injectors (267cc), CR to CP TBs with another TPS Sensor. Same car!! It changed my VE Table completely.

Anyways, just comparing tables does not really do anything unless you have matching parameters. You need to be more specific regarding your configuration.

Jochem

[JohnC]

Thanks. Having never even seen the software used to program an EFI I'm a bit in the dark. From what CK says, I think I'm looking for both the VE map (if I'm correct in understanding that dictates the actual fuel delivered) and the AFR map (the outcome of the VE map being put into practice).

What I'm trying to achieve is pretty basic - what fuel is delivered and what AFR outcome results, for a range of RPM and manifold vacuum, for an engine a bit like mine. Then I can go back to my '60s era kit and play around with a target in mind. As I said, I'm getting fuelling very close to the TR5 target data (except at WOT which is because my vacuum calibration gauge is pretty insensitive at low vacuum). What I don't know is the AFR the Triumph boffins were after at each point. And, as my head & intake manifold (hopefully) breathe more freely that the original, I don't know how much to adjust to compensate.

Jochem - not sure what other info I can provide about my setup. It's a standard CP-series engine with gas-flowed head and gas-flowed CP throttle bodies (my bad, I described them as intake manifold earlier). The AFR sensor does nothing other than report AFR, which I then record in a data logger along with RPM, manifold vacuum, acceleration and sideforce (not that I do anything with the last two). The PI is standard Lucas Mk II, with a Bosch pump.

Below is a plot of my current AFR vs Vacuum. The colour contours are frequency of observation. Idle vacuum is 10.5"Hg. Clearly plenty to do. I'm going to reduce max fuel a little to target 12 AFR (leaner makes the lean spike too obvious), and possibly reduce pre-load (adjustment A1 in the Lucas manual) to make the mixture lean out even sooner as the throttle closes. Mid-throttle of ~14 AFR I'm happy with for now, so A2 can remain where it is, other than to compensate for the max fuel and A1 adjustments. Then I need to adjust the datum track to stop the mixture getting richer as vacuum increases towards idle. I think 14-14.5 AFR at idle works well - any leaner and the idle gets a bit lumpy. Once I've done that I can tweak min fuel (A3) to avoid the datum roller pushing the shuttle against its end-stop.

That's the plan, anyway!

JC