Turbo Tech: Dial in that AFR with Water-Methanol Injection

[kmart356]

The "test mule" is the '62 Spyder with a '65 engine. OT20 cam, stock 140 heads and Mikuni HSR45 with F/B turbo. The WMI system uses (2) 2gph nozzles - one mounted on the intake pad of each head. The programmable controller varies the duty cycle of the RACE (fast acting solenoid) valves to control how much water-methanol is spraying based on RPM and Boost.
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This is the WMI system diagram (1.5gph nozzles replaced with 2gph nozzles)
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The engine was recently freshened up a bit with forged +40 pistons/full fin cylinders and the 140 heads were added.

Background details on this corvair center link: Turbo Engine Rebuild - Phase 1 complete & Phase 2 plans

The dramatic increase in head flow requires tuning the WMI system to keep the AFRs in a safe region especially at 9.2:1 compression. The 2 graphs shown below provide a record of how the AFRs are being dialed in by changing the duty cycle in the respective boost region. Boost runs are being limited to 10psi until the engine has a few more miles on it. Work continues.
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.Graph 1 shows AFRs a bit high in the lower boost region with AFR coming towrds the desired 12.2 around 8psi.
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Mar 2 2024 AFR vs Boost small.jpg (18.83 KiB) Viewed 217 times

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.Graph 2 shows two different test days. Mar 6 results were a little better but still off. Mar 8 results look much better with less variance.
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Next test will be a little less spraying in the 1-7psi range and keep the 8-10psi range the same. The waste gate is currently set for 13psi max but the programmable controller also manages max boost. The previous engine was regularly hitting 18-19psi. Not sure yet if that wastegate will be slowly turned up, up, up.

[Nashfan]

Chances are good that 19psi with your small valve heads feels pretty close to 10psi with your 140 heads... is this why you are hesitating to turning the boost up Heck of a job so far

[kmart356]

@Nashfan, you always know how to poke the otter. I'm not falling for that "turn it up" at least no yet.

Actually, my buttdyno has determined just what you mention. The over 50% more air flow with the big valve heads does indeed feel like more power at less boost like 9-10psi (where the small valve heads need 16-18psi). When the cam+heads start coming into play together at ~8psi, the boost seems to get a more agressive ramp up.

Reference this big valve vs small valve air flow chart.
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[Nashfan]

Yes it "probably" a real good idea to at least get it broke in little before turning up the boost. NAW, come on, DO IT TeeHeeHee
Boost is addicting isnt it?

[chris]

This is cool. You always do such a great job of documenting your progress and sharing it!

[kmart356]

thanks for the kind words @chris.

Well, I do believe the AFRs for 0-10psi are nicely dialed in. The graph shows results from a "rejected" control map on 9-Mar (slightly high AFR) and also shows 2 results from 10-Mar and 13-Mar that put the AFRs in the ZONE! The dotted straight lines at 11.5 and 12.2 are the desired AFR zone.
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This next graph is a plot generated by the WMI controller that shows the (blue line) duty cycle for WMI and AFR (orange) vs boost from 0-10psi.
The WMI duty cycle does not follow a straight line ramp-up and the highest duty cycle is 41% so far. The next set of tests will be to get data in the 10-13psi range.
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[toms73novass]

You number cruncher dude! Great work.