map sensor, help!

Does the map sensor need to have a vaccum line? It runs better with it. Why would I only get 15 pounds of boost instead of 17 when my other car is identical and has the 17 pounds of boost with the map sensor vaccum line hooked up? Also, when the boost builds the tacometer skips, any help would be greatly appreciated.

Technically our cars have a BAP sensor and does not have a vac line connected to it.

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mods: SDS Digital Fuel Injection, ported & polished big valve head(1.89/1.59), Solid lifters, Esslinger roller cam #2277, Esslinger adj. cam pulley, custom upper and ported lower intakes, 60-1 stage III .63 turbo, powerstroke intercooler, 60mm throttle body, 75pph injectors, Walboro 255HP pump, Kirban adj. fuel reg., ATR header, 3" exhaust with Dynomax Ultraflow muffler, MSD 6al, MSD coil, MSD Launch Control, MSD 8.5mm wires, K&N filter, Spec stage III clutch, Greddy Profec B boost controller, Weld Draglites with M/T ET Street 26x11.5/15

[This message has been edited by Glenn 88TC (edited 10-25-2004).]

Glen
How many pounds of turbo boost do you get?

Hello and welcome.

1. The TC don't use a MAP which has a vacuum line connected to the intake manifold.
TCs use a BP (barametric pressure) and it is left open to atmosphere, no vacuum line.

2. I don't know why one car would run better with a vacuum line to the BP. Also that would not control boost level. And if you are relying on the factory boost gauges for the boost readings, they can be inaccurate.

3 what do you mean the "tachometer skips"
Does the speedo skip also? Is this a 5 speed car?

Originally posted by njjoey:
Glen
How many pounds of turbo boost do you get?

I have an aftermarket boost controller so I will run anywhere between 18 and 28psi. Depends on gas(pump or race) and weather. When it was stock it got 15psi.

I have a vaccum T coming off of the main vaccum line. The one goes to the overboost, the other goes to the inter cooler. The other port on the inter cooler goes to the map sensor. My other car ran on this at 17 1/2 pounds of boost without flaw in the system. Why can't this one run like this? It runs near this but it has a miss where the tachometer skips a few rpms.