I've heard mention of electric vacuum pumps to boost vacuum for power brakes, MAP sensors, etc.

What pumps did you guys use? I know MasterPower brakes sells one; do you know of distributors for their parts?

Aslo, I've heard that several GM cars came from the factory with electric vac pumps. Anyone know about these?

Does using a vac reserve help with low vac for the MAP sensor?

Thanks
Bill

 

Using a vacuum pump for power brakes and the crank case is fine but don't hook it up to a map sensor. The map sensor is how your ecm controls how much fuel the engine needs (if you've got a 454ss it's speed density).
I know that you can use the stock smog pump and reverse it to be a vacuum pump. I personally haven't done it yet but I'll give it a try. 4th gen f-body's have an electric air pump and I bet you could reverse them as well. I'm looking for more assist with the brakes so I might try this.

 

The idea I have is to only use the electric vac pump at idle. This would achieve 2 things. It would allow more vac to my vac ref FPR to allow a lower FP at idle. 2nd, it would give the map sensor the proper vac readings to make the computer happy.

Bill

 

hold up....how do you figure a vac pump would give the map sensor a more accurate reading?
Something else is amiss. If you aren't getting low enough fuel pressure with your current vac.rFPR then there are alternative ways to go about fixing it. Do NOT have the vacuum pump just come on at idle, fuel control (map sensor) is not speed dependant, it's engine load dependant!!!

 

I understand that the MAP is load dependent. I have a different cam that causes a low vac reading at idle. I was trying to fool the computer into thinking I have the correct amout of vac at idle.

Bill

 

You don't "fool" the computer that way to get the result you want. It won't work. The computer is in control of how much fuel the engine gets, and has to measure the engine's air intake so that it can match it with fuel; it doesn't just sit there and be "happy" or not. If the computer is seeing some vacuum other than the engine's intake vacuum, which is the only way the ECM knows what the load on the engine is, it will be completely unable to meter the proper amount of fuel.

The correct way to accomplish that (adapt the computer's behavior to the characteristics of a modified engine) is with PROM programming. You need to learn to write your own code and burn your own PROMs.

 

Believe me, I know!

You guys make it sound soooooooooo easy!

 

Of course.

It's always easier to get there the right way, than it is to go the wrong way and expect to end up in the right place.

 

. It cycles automatically.

 

Is it electric? p/n?

 

cant really be more specific.. i would not think about buying one new...

It would be a killer..
this one is a little expensive.. http://cgi.ebay.com/ebaymotors/ws/eB...&category=6033

but keep your eyes peeled for this type of unit. Mine is identical to it.