MAP Sensor Question From The Cave

[pontiacgp]

sorta over my head here so I figure you guys can have a laugh while giving me simple answers. The Fast efi has a MAP sensor mounted to the throttle boudy and the MSD 6530 ignition box has a connection for a MAP sensor. The MSD program reads the pressure at 2 with no MAP sensor. As usual the MSD instructions suck, there is no alerts on the program altering me to any problems so I guess I can run without a MAP sensor for the box. I'm wondering if I should get a MAP sensor to use with the box, I sorta know what a MAP sensor does... 🤔

 

[motorheadmike]

Run the MAP if it is designed for it. GM 1 Bar MAPs are cheap and plentiful.

 

[fleming442]

Is the MSD input a vacuum port or a wiring input?
Does the FAST have 2 wires that would trigger the MSD?
Post up some model numbers, so I/we can see what you're dealing with.

If they both want a vacuum reference, couldn't you tee between them? You don't want them fighting each other, though. I'm sure one will do the job better than the other, but there is an off chance they're looking at the vacuum signal for different reasons. I would think the MSD input is more as a reference to pull timing under boost, where the FAST is for general idle mixture and throttle response.

 

[pontiacgp]

I have the FAST EZ-EFI Fuel Injection System Base Kit (EZ-EFI 1.0), w/4150 Black Anodized TB, w/Touchscreen FAS-30226-06 and the MSD box is 6530. The MSD box does not have any vacuum ports and the MAP connection is 3 prong electrical connection. The only connection between the Fast system and MSB box is the tach signal but I could also use the tach signal for the Fast sytem from the distributor. The Fast system needs a clean tach signal to work and trying to use the coil as a trigger screws up the Fast system

You guys are bringing some light to my cave, thanks

https://www.jegs.com/InstallationInstructions/100/121/121-6530.pdf

 

[motorheadmike]

An MSD MAP sensor is required to use this feature and three
are offered:
1-Bar, for normally aspirated engines, PN 23111
2-Bar, for 2-30 psia, PN 23121
3-Bar, for 2-45 psia, PN 23131

Hit up Amazon or Summit etc for a quality 1 Bar unit, and then you can scale your timing against vacuum/load and rpm in the software.

 

[fleming442]

Well, I don't see much online as far as the FAST installation instructions. Is their MAP built-in or separate?
I'm assuming that you have the MSD triggered off the white wire, which is the coil output from the HEI module. You used to be able to yank the module out, and trigger the purple and green off the VR sensor in the base of the distributor. I had my Olds set up like this for a long time, but removed the HEI in favor of a Pro Billet due to shaft slop. If it were me, I'd do it again. You're removing the HEI module from the equation, and letting the MSD take over full spark control. MSD boxes require that you use the "tach output" (gray wire) for anything requiring a tach signal; the orange and black are to feed the coil only. Therefore, the gray needs to be split between the FAST and the tach.
The only reason to run the MAP with the MSD is to build a curve (in a NA application), which would be optional on a stick car as far as I'm concerned. I don't know that designing a timing curve would be worth the time and effort. In any case, the MSD destructions say that you have to use their MAP.
These are just my thoughts and opinion- not the gospel.

 

[pontiacgp]

the FAST MAP sensor is mounted on the throttle body . As for the distributor I'm using the MSD E curve, it has a 3 wire connection, one power, one ground and an orange wire which is attached the white wire coming from the box. I'm using the green tach wire from the distributor for my dash tach.

 

[fleming442]

I think the box or the dist would be enough, but not both.

 

[pontiacgp]

An MSD MAP sensor is required to use this feature and three
are offered:
1-Bar, for normally aspirated engines, PN 23111
2-Bar, for 2-30 psia, PN 23121
3-Bar, for 2-45 psia, PN 23131

Hit up Amazon or Summit etc for a quality 1 Bar unit, and then you can scale your timing against vacuum/load and rpm in the software.

thanks, I just need the 1 bar but the 23111 is over $100 on amazon.ca I'll look for an alternative

 

[motorheadmike]

thanks, I just need the 1 bar but the 23111 is over $100 on amazon.ca I'll look for an alternative

Yeah, FAST/Holley/etc all just rebrand AC Delco units and charge you a premium. Check the usual scumbags for one from an '87 to '97 car. Hell, you could probably find one in the junkyard out of a late 90s GM car. Alternatively you could make an adapter harness and use and LS1 1 Bar unit - I believe the offsets are the same.