Staring down the EFI rabbit hole again, /6 intake design, Which way around for the 964 plenums in a 914? |
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Staring down the EFI rabbit hole again, /6 intake design, Which way around for the 964 plenums in a 914? |
Mark Henry |
Feb 17 2021, 10:34 AM
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
One of the locals fell on some hard times, his plans changed and his 930 was sold, so he offered me a smoking deal on an EFI system.
SDS EM5-F /6 system with twin plug coil packs, Siemens 55lb injectors, cold start valve, crank trigger and /6 trigger mount, extra relay outputs (had meth injection), Beru plug wires X2, manuals, base maps, dizzy hole block off, Bosch one wire (Djet) head temp sender plus all the cabling, fuses, etc that are not included with an SDS system. I already have a Wabro 300hp FI pump, a Djet fuel pressure regulator, 14point7 wideband O2 meter and an O2 bung in both headers. This is not a discussion on which Aftermarket EFI system is better, etc but rather on plenum based intake design. I'm not new. I've been playing with a SDS EM4-F /4 system since 2003-2004 that's now on my '67 bug T4 2600cc conversion, I know that ITB's are better for peak HP, but I'm after overall improvement, usable vacuum signal for MAP, drivability, fuel economy and etc. FYI I have also asked this on the bird board here for some more info on the build. This thread shows my /6 conversion a few years back and has all the engine specs here. Plus I've built my own motorcycle ITB's before here. Please I only want to discuss a single TB plenum based intake for performance EFI. |
rick 918-S |
Feb 18 2021, 10:33 AM
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Hey nice rack! -Celette Group: Members Posts: 20,680 Joined: 30-December 02 From: Now in Superior WI Member No.: 43 Region Association: Northstar Region |
Probably don't have to tell an experienced engine guy like you about this but for others that may not be aware, cam shaft lift and duration are key with EFI. At least with CIS as too much pulse in the intake makes for wacky reactions to drivability. Maybe you can expand on how it effects more modern EFI stuff.
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Mark Henry |
Feb 18 2021, 11:25 AM
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#3
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
Probably don't have to tell an experienced engine guy like you about this but for others that may not be aware, cam shaft lift and duration are key with EFI. At least with CIS as too much pulse in the intake makes for wacky reactions to drivability. Maybe you can expand on how it effects more modern EFI stuff. Yes Big cams with big duration equals a poor vacuum signal for the MPS (Manifold Pressure Sensor) adding ITB's (individual throttle bodies) makes the situation even worse. Aftermarket EFI can cope better with this poor vacuum signal but you can push things too far. My hope is the plenum with a single TB and a vacuum can will give me a more usable signal for the MAP. I also won't have to worry about sync issues with the single TB. You can get around this by running TPS only, also known as AlphaN, to bypass the MAP but you lose things like altitude correction and the system is more sensitive to pedal inputs, which can be a pain on long trips. But EFI of course wins on fuel mileage. Between having to run in AlphaN or carbs, I think carbs wins on drivability as they're not as touchy to pedal inputs as the EFI in AlphaN. |
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