Just wondering what kind of numbers you guys get @ idle. My greddy profec b shows around 65 at 950RPMs. I ask because I have not had a gauge before and do not know what the average is.

 

That in KpA? 65 is as bit low. Most non ported rotarys will pull 40-45 at idle.

 

The car has a street port, and has 500km on the rebuild. I swore the day before the profec showed a number in the 70's but I might be wrong....

I am not sure what it is measured in. I thought most people have single digit numbers. Am I I suppose to divide that by 10?

 

Pfc is around 390 mmHg. Just spoke with Darryl and he said I need to divide that number by 25.4 = just under 16 inches of mercurary. I hope I got that right. Thanks Darryl

 

My basically stock port engine pulls -78 to -80kpa on the profec.

Yours sounds about right for a nice RD street port.

 

The units on the Profec are in psi multiplied by 10 (psi is an awkward way of displaying vacuum as we talked)...you can change it to metric as well.

A reading of 65 is actually 6.5 psi. That would make it just over 13 inHg or just around 337 mmHg.

Hook up a mechanical vacuum gauge to see how well all 3 readings correlate.

 

my street port 12 draws about 40-43 kpa at about 1000 rpm

 

I usually pull a Hoover or a Dirt Devil myself

 

^ zzzzzzzzzzzzzzing!

My streetported 13B pulls about 20-15mmHg at idle, depending on the load (alternator, rad fan, etc.).

 

with load my engine normally revs up a bit, and makes it go down lower

 

I don't have an idle air control system. The TEC controls, or at least tries to control idle speed with timing advance. I'm going to be adding the IAC in the spring.

 

lol don't have it neither, I'm running Individual Throttle Bodies. But the way I have the megasquirt setup is that when I'm running more things it normally wants to drop the idle, and go into a higher KPA area, but in that area there's a bit more fuel and so instead of trying to stumble it revs up a bit with the more fuel, and maintains a higher rpm

 

Lower vacuum is expected with a bigger street port. Like Daryl suggested, a proper boost gauge would be the best way to get a reading, however don't expect to pull high vacuum just because its a fresh engine. Also, I would run 1,000 RPM idle minimum with your porting. Minimum meaning it never goes below that. 390 mmhg on the PFC is a good reading for 950 RPM and the porting however, don't take the pfc reading as truly accurate as the map sensors never read exactly the same even with same calibrations.

thewird

 

I noticed after posting this the car did idles around 1000-1100RPM. It must have dipped down for a second because of the heater, fans, or some other accessory coming on or off line. The new clutch is going to take some getting use to. My drive home in stop and go traffic was interesting lol.

 

Tune will affect vacuum readings as well. Running too rich or too lean at idle will lower vacuum.

My bridgeported car pulls 10-12" at a 1500 RPM idle.

 

I'm getting about 16" on a large streetported S4

 

Also just remembered 3mm will pull less vacuum then 2mm.

thewird

 

And 1-piece vs 2-piece. I remember reading someone who had built an engine twice with each type, and the two piece made 20psi more compression (120 psi vs 100 psi)