Floorman279

iTrader: (11)

the purpose of this thread is to see if with the little bit of data i got, if u guys can tell me if my map is loose and sucking in air. its a gm map, in an old non revised fast 90. i did buy a new grommet, and wrapped it in thread tape but it was still decently loose. so i did a bunch of black jb weld, and put it on. then i had to replace my oil pressure sending unit and while i was back there i bumped it loose. so i blindly pulled it out, did a ton of jb weld smeared around the intake hole and put it back in. its decently tight now, but still madly concerned.

so the car is on a mail order tune right now. the O2s are in open loop having only driven about 8 miles after my heads and intake swap. and the battery being disconnected. waiting for my tune day. so i have an old code reader that does do map data in "in.hg" whatever that means. i never went above 2200 rpms, and my numbers were always between 10 and 21, depending on the situation and the numbers never spiked once during my 5 mile trip today, i mean they bounced around a lot but that was every time i got on off throttle. heres the numbers

sitting still idling at 1080 is 17.7

1800 rpms sitting still is 11.5

moving at 1700 rpms in 4th gear at 34 mph 16

thoughts?

truckdoug

iTrader: (25)

inches of mercury. its just another way to measure pressure (+ or -)

17" of vacuum is a pretty mild cam. maybe turn the idle speed down? as you open the throttle blade (rev to 1800 rpm) the engines' demand for air is closer to being met, so vacuum drops to 11"

all sounds about right to me

Floorman279

iTrader: (11)

its not mild 236/238, .601 .605 stock 346.

yea i thought about messing with the adjuster screw but 1050 idle isn't ridiculously high so ill just wait for the tuner......so am i correct that as long as it never spiked at any time (besides while revving down or up) i should be ok?

truckdoug

iTrader: (25)

i'm not sure why it would spike or what that would mean if it did. this is an N/A car right?

Floorman279

iTrader: (11)

correct N/A. i was under the impression that if ur map sensor was leaking (had a bad seal and was sucking in air) u would see ur numbers randomly bounce around and not be stable or consistent

Russ K

iTrader: (1)

Actually, Map is inverse of Vacuum. At your altitude, the pressure is 28.93 in. hg. So to convert to manifold vacuum, subtract your 17.7 in. hg from 28.93 =11.23 in. hg vacuum.

And at WOT, you should have 28.93 in. hg map. This would be 0 in. hg vacuum.

Russ Kemp