Thanks to Rodder for the info on the vacuum guage. Unfortunately, MSD doesn't use the same system as you, unless I'm totally messed up. If you look at the guages on the software they provide, they read in PSIa. What's that about?? It reads from 0-15 PSIa. With a mild cam (222-234), and at idle, it will be about 11 inches of vacuum on a normal guage and it will read something like 13 PSIa on the MSD guage. Then, as the RPM increases and the vacuum comes up, say to 19-20 inches of vacuum, the MSD guage goes the other way, down to say 5 PSIa. Weird! I guess I am eat up with the dumbass, but it hasn't fallen into place in my brain yet.
im running a victor jr intake, msd ignition, and a out of the box mechanical secondary 750 mighty demon.
im dreading taking the trans out. not sure if i should try to wrestle it out on my back or pull the whole rig out and detach the trans. its such a huge heavy bitch.
That transmission really isnt THAT bad. I'll be wrestling mine out on plywood in the grass when i have to. The trans felt lighter than the TH400 i had in it.
im a little confused what Rodder said- he has "30" with a value of 0 and 100?
30, 15, 30? did he mean 0 is 100
i think the FI cars use some kind of values to 100, a diff setup
the way i understand the map, with the engine off, no vacume, the map is seeing 14.7 psi, which is present all the time, we just dont feel it, but its there(dont know who figured it out) now, when you start the engine, vacume is present, sucking on the map sensor, fighting against the ever present 14.7 psi, which reduces the 14.7 by some figure
if the map had 14.7, and you had 14.7 vac., i would think you would see 0, but doesnt seem to work that way?
now at wot, if no vac., the map figure should be back to 14.7 (1 bar)
now on my procharged engine, at wot, it should see 14.7, plus any boost, up to aprx. 30(2 bar) because besides the ever present 14.7 w/o vac., i am now adding more pres-if you go in and change your 1 bar setup to 2 bar, you will see the graph change to 0-30(you would need the 2 bar sensor)
now, how all the numbers relate to msd figures, i have no clue, and some of what i just wrote, may be way off, lol-too much coffee this morn
Thanks to Rodder for the info on the vacuum guage. Unfortunately, MSD doesn't use the same system as you, unless I'm totally messed up. If you look at the guages on the software they provide, they read in PSIa. What's that about?? It reads from 0-15 PSIa. With a mild cam (222-234), and at idle, it will be about 11 inches of vacuum on a normal guage and it will read something like 13 PSIa on the MSD guage. Then, as the RPM increases and the vacuum comes up, say to 19-20 inches of vacuum, the MSD guage goes the other way, down to say 5 PSIa. Weird! I guess I am eat up with the dumbass, but it hasn't fallen into place in my brain yet.
psia/absolute is 14.7 at see level. psig/gage is 0 at see level.
So 5 psia is lower than 14.7 atmospheric pressure making it neg pressure.
5psia=18 inches of vac.on psig
It,s alot like converting Fahrenheit to celsius
I hope this helps and don,t confuse you more
__________________ 1994 S-10 under construction
11:1 alum.5.3,ls6 heads, 112,Holley 750 DP ,226/232 .609/.604 111LSA +2,Victor Jr,MSD6010,rossler th400 w/transbrake/4k yank,Art Morrison 4-link,3:90 in moser 8.8
Thanks, *Sheephead*. The way you explain it makes more sense to my hard head than the KPa system. Also, thanks to *forced induction* for the input on the boost aspect of it. Not saying I fully understand it, but is finally starting to make a little sense. I guess what I need to do is make myself a chart showing what negative pressures equal in inches of vacuum, something like what *Sheephead* described as 5 PSIa=18inches of vac. on PSIg. Anyway, thanks a bunch for the help guys!
Thanks to Rodder for the info on the vacuum guage. Unfortunately, MSD doesn't use the same system as you, unless I'm totally messed up. If you look at the guages on the software they provide, they read in PSIa. What's that about?? It reads from 0-15 PSIa. With a mild cam (222-234), and at idle, it will be about 11 inches of vacuum on a normal guage and it will read something like 13 PSIa on the MSD guage. Then, as the RPM increases and the vacuum comes up, say to 19-20 inches of vacuum, the MSD guage goes the other way, down to say 5 PSIa. Weird! I guess I am eat up with the dumbass, but it hasn't fallen into place in my brain yet.
Doh I'm used to HPTuners which uses KPa. Lemme convert that from metric back to SAE...
It works the same way as vacuum gauge, only the numbers are different.
Now where it has "30" (inches of Mercury), cross that out and write "0 psia" (psi absolute). And where it has "15", cross that out and write "7.5 psia". And where it has "0", cross that out and write "14.7 psia". Cross out 5/10/20/25 cuz I don't feel like converting them . Does this make it easier to visualize?
mine seems to sit around 8psi if i remember at idle on the msd software gauges /display. i have it set so no advance above 12psi on there but it only adds in upto 10 deg anyway.
car seems to like idling/part throttle at 33-35deg without getting too bothered.
What about the transmission? If we go the carb route, can we use the 4L60E? Do we need a separate controller or wiring harness for the trans, or does the msd harness work the tranny too? Sheephead, is your harness already modified? Are you selling it with the pcm?
__________________
346, LS6 Intake, 30 lb. injectors, Absolute speed stage 2.5 heads, T-Rex, ASP underdrive pulley, 425 RWHP, FLT Level 5 vacuum modulated, Yank PT4000. Smooth firewall, hidden wiper motor, Global West, Hotchkis, and Bilstein keeping the Sumitomo's on the ground.
My FQuick site: http://www.fquick.com/ls1nova
What about the transmission? If we go the carb route, can we use the 4L60E? Do we need a separate controller or wiring harness for the trans, or does the msd harness work the tranny too? Sheephead, is your harness already modified? Are you selling it with the pcm?
I,m using a turbo 400.The harness + pcm is complete unmodified to 02s,trans(4l80).
I bought a complete engine trans out of a 06 Savana van with 10 miles which had a 6.0+4l80
__________________ 1994 S-10 under construction
11:1 alum.5.3,ls6 heads, 112,Holley 750 DP ,226/232 .609/.604 111LSA +2,Victor Jr,MSD6010,rossler th400 w/transbrake/4k yank,Art Morrison 4-link,3:90 in moser 8.8
"What about the transmission? If we go the carb route"
i am using 4l65e , you have to use seperate controller, i used the hg electronics compushift with display , you can get a GM controller aswell not sure on others.
my kit came with harness and tps sensor for carb,
You do not need any of the harness to make the engine run. If you have an auto and intent to keep it electronic you will need the separate controller mentioned. Or you can convert the transmission to a manual valve body.
I bought my engine complete with harness, EFI, and computure and just sold everything i wasnt going to use on my carb setup. You dont even need your knock sensors. Your waten temp sensor you will need auto meter part number 2277 which is an adapter for the 1.50x12mm thread in the drive side head which adapts to 1/8" NPT
I bought my engine complete with harness, EFI, and computure and just sold everything i wasnt going to use on my carb setup. You dont even need your knock sensors. Your waten temp sensor you will need auto meter part number 2277 which is an adapter for the 1.50x12mm thread in the drive side head which adapts to 1/8" NPT
When you get it to 1/8" NPT, what do you do then? Add more adaptors to allow a 3/8 or 1/2 inch temp sensor to bolt to the 1/8 inch hole?
I thought about doing it that way but figured it would put the temp sensor so far outside the block that the guage wouldn't be accurate. Is that what you did and does it work? Not slamming, just want to know.
I ended up drilling out the block heater plug and installing the stock Datsun sensor into that.
About the temperature guage. I have a Dakota Digital dash panel in my '34 Ford and I just went to their web site and ordered a 12MM sender and screwed it in to the driver side head. Works perfect. I would bet Autometer and other guage manufactures offer a 12MM sender for their guages also. To *Rodder*. I printed off a picture of the guage you mentioned and I'm going to mark it like you said and try it. Maybe it will help me understand it, or at least help me set up the vacuum advance the way I'm used to. Thanks to everone who have trid to explain this vacuum vs. PSIa deal.
Oh i wasnt talking about using the datsun sender. I used Autometer Ultralite gauges. Sorry. The coolant temps sensor just barely doesnt fit inside of the adapter, for whatever reason, but i just took a bigger drill bit, held the adapter with a pair of channel locks and drilled it out bigger. It was really easy because its just brass.
. Does this make it easier to visualize?
