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Want to borrow my LM1 for wideband testing?


Curtis - Thanks for the offer.... maybe so. So far, my plan is to buy an LM-1 for permanent installation so I can also use it for data logging and dash gauge readout, but I haven't decided for certain. I know I don't need it beyond the tuning stage, but it seems to me that a permanent installation is a good idea.

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Frank, from my looking at the 3.8L GM (same manufacturer) blower, I was thinking that you could add that into the MS equasion. With the extra outputs of the MS relay board, maybe actually controlling boost with the bypass valve for load conditions.
EG:Uphill grade of 5% load detected by RPM's & MAP sensor = "Somuchboostpressuredesired" controlled by a PWM air bleed solenoid (converted GM IAC) to allow butterfly partial deployment. Say needed boost was 2.5 LBS, butterfly would close a specific ammount to allow that much boost & then control the diaphragm through the IAC setup.... It was how GM used the setup, if I remember correctly.


Ed - the bypass valve vacuum actuator works in a similar fashion - as load increases, vacuum drops and opens the butterfly valve in the blower. It's a gradual blend of air to the blower - not like a switch. From my earlier driving impressions pre-failure, the vacuum actuation works great and blends very smoothly. If you didn't have a boost gauge, you'd never know what was happening.... except for the sound at WOT....... <img src="/forums/images/graemlins/smile.gif" alt="" />

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I wonder if anyone has decoded the GM ECU to assist in your tuning?


Engines have their individual quirks with ignition timing needs, so I'd rather give this one what it wants to be happy. I don't have the factory timing map for it, but I did find the map for a 24v DOHC TT engine. It's quite different from what I observed on the SOHC Montero engine. Peak advance is similar, but the VR4 curve is stretched out over 8500 rpms instead of 6500 rpms. Where the VR4 has 34* of advance @ 3000 rpms/light load, the SOHC trucks have 40*.

Here's the ignition map for a 1995 3000GT VR4:

Ignition Map

I would not want to install MegaSquirt on a 24v engine - looks like a nightmare in Alpha territory.

Frank

'89 [color:"white"]G-Raider[color:"white"] [color:"black"]Supercharged 3.0L, MegaSquirt 2, lockup A/T, 2.5" exhaust, 172k, Cibie H4s/Oscar SCs, Hella Micro DE fogs, Cobra CB, Superwinch hubs, LSD rear/Aussie Locker front, Bilsteins, Lifeline AGM, Rust-Oleum