mmcd vacuum reading

[4gfun]

Here is an odd one. I have an autometer mechanical boost gauge in my car, but it does not specify vacuum readings.

I can't see going through the hassle of replacing a perfectly boost gauge just because it doesn't have this feature.

I was wondering if MMCD specifies vacuum readings at idle. If so, does anyone know if they are accurate?

Many thanks!

 

[steve]

MMCd does not report on engine vacuum. There isn't a sensor for it in the car.

 

[the_mork]

You can always add a MAP sensor to the car which is incredibly useful for logging boost as well as vacuum.

I've honestly never really felt the need for a vacuum gauge on my car. My boost gauge does both but it wouldn't need to. I can tell everything that might be wrong with the car much more easily and precisely by looking through logs and doing basic maintenance (like BLTs) than I could through a vacuum gauge.

 

[4gfun]

Thanks all. I didn't know that there was no MAP sensor on the car and I shouldn't have assumed.

I was thinking more along the lines of Romraider for Subarus.

Thanks!

 

[the_mork]

2gs actually do have an MDP which reads to 1bar. They can show you vacuum readings on a log but it maxes out at around atmospheric pressure so it is of little value on a boosted engine. It exists solely as a piece of the EGR system and does nothing else.

 

[clockworktoy]

Wouldn't a MAP sensor not read vaccum accurately since it reads absolute pressure?

 

[steve]

2gs actually do have an MDP which reads to 1bar.

Since a Galant VR4 doesn't I didn't bring it up.

 

[the_mork]

Wouldn't a MAP sensor not read vaccum accurately since it reads absolute pressure?

How accurate do you want it to be? With some math you can get a reasonable conversion then check it against the baro sensor. I can almost guaranteed that is much more accurate than eyeballing a questionable quality mechanical gauge.

Steve: I was just adding information so that someone didn't get the misconception that no 4g63t cars had an MDP, no one who has been around for any length of time doubts your knowledge.

 

[clockworktoy]

My logs show big differences between the gauge and the MAP sensor. I personally don't care what it reads unless it helps me figure out a vac leak.

 

[the_mork]

Which was my original point. At some point someone wrote in a guide (or several) to get gauges with vacuum readings and so everyone does it. I don't personally think it is useful if you do frequent BLTs and pay attention to your car.

 

[steve]

I don't personally think it is useful if you do frequent BLTs and pay attention to your car.

I find the vacuum gauge one very useful way TO pay attention to your car.

It's isn't something that I feel needs to be logged however. If your putting a MAP sensor in the car to log boost you get vacuum for free but I wouldn't spend any money just to log vacuum. I also have a EGT gauge for monitoring but I wouldn't pay to log it either.

We've answered the question and the rest of this is off topic anyway.

 

[4gfun]

I find the vacuum gauge one very useful way TO pay attention to your car.

It's isn't something that I feel needs to be logged however. If your putting a MAP sensor in the car to log boost you get vacuum for free but I wouldn't spend any money just to log vacuum. I also have a EGT gauge for monitoring but I wouldn't pay to log it either.

We've answered the question and the rest of this is off topic anyway.

Yes all, this is why I want it. I want to see how much vacuum my car pulls at idle. I noticed problems with my previous DSM's when I didn't pull vacuum.

Not sure exactly what it was, but it was something or other.

Thanks again!