krystar

I'm tracing the vacuum line coming off the intake mani. first branch goes out to the brake booster, and then the aux valve and idle stabilizer....and eventually, the vacuum line goes into the underside of the Jboot.

why does the Jboot need to be hooked up to the manifold ? i don't understand that.

Eastep

EGR maybe?

krystar

this is just off the intake mani. nothing with exh mani. besides, we don't have external EGR in the 944.

m73m95

If I'm understanding your description correctly, thats where the ISV gets its air from. Thats how it adjusts the idle speed.

moorepower

Correct. As the valve inside the ISV opens it allows air to pass from the J-boot directly to the intake manifold, bypassing the throttle plate, and raising idle speed.

krystar

i see....and if one were to have removed the ISV completely, then this entire mess wouldn't be needed and the only hookup would go from intake mani to brake booster :P

DarylJ

In fact, that mess would be a REALLY BIG LEAK if one were to remove the ISV without deleting the rest

krystar

lolol yea i just plugged the holes when i did it last year. didn't even think. wierd that the car still runs and idles smoothly with that big of a vacuum leak.... *shrug* will just finish the job then hehe

krystar

lolol so i finished up the delete. engine would start, run for like 2 turns and then die. i was like wtf.....then i thought to adjust the idle screw. so apparently the previous vacuum leak was so bad that in order to compensate for the vacuum leak, i had the idle screw turned all the way in. so after about 8 full turns out, the engine started and idled heh.

yay for really hard braking! that vacuum leak basically was cutting my braking power by 3 fold.

Will Feather

someone should really explore all the various ways to delete parts of the vaccumm system...and then tell me haah

krystar

the only part of my vacuum system left is 1 line to the brake booster and 1 line with a T to the FPR and FPD. heh

RobHeinl

Yeah, I've got mine down to FPR, FPD, Brake booster and Megasquirt. No more Jboot or anything down downstream either. Heck, I don't even have my ISV hooked up, that's where I mounted my GM IAT for Megasquirt (after tapping the threads).

For some reason it's very satisfying to rid the car of all "unneeded" vaccum lines.

krystar

rob, so wait you don't have a jboot? pix please

RobHeinl

That's right. However I did not do a clean job on the air filter piping. I went to Autozone, went to the ricer section and picked up a cone filter and cheesy 90 degree elbow to clear the hood. I'm sure I'm pulling in really hot air too. Come to think of it I could test since i have IAT readings in my datalogs.

I tell myself it's temporary because I'd like to put in a supercharge some day... we'll see.

If you look close you will see some Coil on Plugs..

krystar

lol spectre. same air filter i got :P

is that a coil on plug?