Set your idle to 800 rpms and (when your motor's at operating temp) what kind of vacuum are you pulling?

If we get enough responses, we can use this data as a way to monitor motor health

 

This needs to be broken down to stock ports,
mild ports, and radical ports. Porting the exhaust
and/or primary intake ports affect idle vacuum.

 

I figured it wouldn't take long before someone told me the poll wasn't specific enough .

I set it up the way I did b/c many don't know what kind of port job they have...they just know they have a streetported motor.

I will say my idle has dropped from like 460mmHg to anywhere from 410-430mmHg in the last few months as the motor has broken in. Not exactly sure why; has me a little worried...

 

my idle is at 720rpm, and I get maybe 440mmhg. All of a sudden a couple of weeks ago it dropeed to like 390-400. It ended up being and short wire causing the fans to come on, thus creating electrical load, but...the PFC didn't know this and wasn;t compensating. Had horrible idle, fall out, and low vaccum.

Just an idea Rich, coudl be something else. ALthough I have no idea what is normal for breaking in a rotary.

 

Well, when my car is idling at 770 rpms, like its set to on the commander, I get around 465ish. No porting.

Tim Benton

 

What do you mean by fall out???

Before my motor went south I was getting around 460's like Tim. After killing a apex seal I'm getting low 300's like 330 or so. My idle stays perfect but my car sounds and feels like it has a cam in it!!!! Damn, I just had to push some buttons didnt I.....eerrrr, cant type about it anymore, I wont be able to sleep tonight if I'm thinking about it

Later,
STEPHEN

 

Dang you guys have me worried for some reason.

Let's see

3mm seals, mild street port,

intake, dp, mp, catback

stock size pullies

when warmed up i see -325 to -340 somewhere within that range. Of course my idle is sometimes rough at idle because of the porting and it bounces around a lot. But when it steadies out it's within that range.

Power is still pretty strong so I'm not to worried.

Motor is about 6k miles new.

On my boost gauge however it seems to read inbetween -400 and -500 so I do see a small discrepancy.

 

twinturboteddy, was your car at RotaryPerformance in Gardena, CA earlier this year getting a rebuilt engine?

I had my engine rebuilt by Jeff at Rotary Performance earlier this year, with a mild streetport(Jeff called it a smog port). I was seeing some low vacuum readings as well from the start. 13in. indicated by my boost gauge or about 360 by the PFC reading, but does not bounce around much.

This is with the car idling pretty steady in the range of 720-750. Jeff had said that vacuum may increase as the seals wear in, but after about 8k miles I haven't seen a change.

But the motor runs beatifully and pulls strong beyond 8k rpm so not really worried with the low vacuum readings...... yet.

 

Another thing to consider is if you still have an air pump running or not. I have a straight through exhaust (nice FLAMAGE) but haven't had time to pull the air pump off and save the 9 lbs. of dead weight, but I did notice that without the air pump hooked into my M2 box, I would get around 16 on the vacuum side on my boost gauge, then once I hooked it back in, back in the 17 or a tad higher range.

I have always heard that a street port would pull roughly 15 on the vacuum side, from the 4 plus years I was on the big list and from my friends who have had it done. They saw around 15 on their car.

Tim Benton

 

Fret, yes my car was at Gardena about a year ago undergoing a rebuild. You probably saw it there.

Oh yeah, I don't have an air pump either.

Looks like we share a common trait with both our engines running in the range of -350 or so.

My friend's stock motor FD (strongest stock FD I've ever seen and is the white car below) runs a solid -450 at idle

 

I usually see over 475...sometimes I am in the low 500's

Stock motor, nothing ported w/air pump..idle at 720rpm's
Autometer boost guage read about 16

 

@ 850 RPM i see about 485-490 on the PFC and 16-17 on the boost gauge

 

Can someone HELP clarify for me the whole rev/idle settings?

Rev. Limit 8100 rpm..............self explanatory!
F/C A-E 1000 rpm.......whats f/c and a-e all about ?
F/C E/C 1100 rpm....... " " " e/c " " ?
F/C A/C 1200 rpm.......Im guessing w/ the AC on?
Idle A-E 720 rpm....... a-e?
Idle E/L 800 rpm........ e/l?
Idle A/C 900 rpm........ correct me if its not the AC.

Im guessing the base settings for the idle are good but I'd just like to know what some of those abbeviations mean........

TY!

Oh BTW........if I get a response to the above Ill be able to give ya my result of the poll above.

 

Go to page 33 of your commander manual. On the bottom of the page in the notes section it will explain it all to you. The manual is available for download here on the forum if you dont have one.

 

God Im goin BLIND!!!!!!!

TY FDracer!!!

 

On your handset, plig these numbers in to bring your idle up

idle a-e 770
idle e/l 850 (eletrical load, lights, fans etc.)
idle ac 950

Thats what ray plugged in for mine when he tuned it.

Tim Benton

 

Im running arnd 410 @ 720 rpm.

Stock motor w/ approx 89000 miles.
No dp or intake YET!
Just a cat- back.

 

I don't see that this is a very good indicator of the engine's health - specifically.

My car always had about 10 inches (250 mm) of vacuum, but had great compression. Same Vacuum after my compression declined a bit, then when I got silocone hoses in I obviously replaced a leaking vacuum line someplace - and I got 380mm - even after my o-rings went.

With a reman out of the crate I now get 450-510mm, depending on idle, outside temp, etc.

A bad engine can cause low vacuum, but so can a lot of other things - including a streat port :-p

 

Well, FWIW, I read right at 490~500 at idle with no electrical load. My motor was rebuilt about 25K miles ago, mild port, 3mm seals.

 

-370 to -390 with a large side and exaust port To4R single turbo with A/R 1.0 P trim exaust housing ...

 

My car @ 850RPM pulls about 330-340mm/hg on the PFC. This enigine is fairly new and has a fairly substantial porting job on it. As it sat before with the old rotor housings and stock idle it would pull around 15in/hg, this was before the PFC. Once I had it rebuilt and had the new ported rotor housings added vacuume dropped to where it is now ~11in/hg. This shows the difference in the port job I had before to hte one I have now. Same intake porting but obviously a lot more agressive exhaust port job. Driving has become a game to see if I can keep it off boost.

 

I'm pulling between 485-490 @ 780RPMs on the PFC, my autometer boost gauge says 18-20''. This is on a new motor with about 17K miles, without a port job.

 

Mine is at about 450 at 800rpm idle.

3 mm and ported motor should give less compare to stock motor.

Timmy

 

Geez, I typically run low 400's (410 or so) maybe high 390's, no airpump, stock engine/turbos. Still strong enough to trounce a Z06 (405hp variety) however.

Full mods, straight through exhaust, large SMIC, ignition, lightweight flywheel, etc...I do admit to not having a perfect idle however. The little white plug on the back of the intake manifold is not plugged in. Can't get it to idle correctly when it is!
Michel

 

Instead of everyone stating what they have with or without ports, why don't we try to logically pin down what affects the vacuum at idle. We know a port lowers the vacuum, now what else? Some thoughts that come to mind are all the increased air flow mods... intake, downpipe, midpipe, catback, non seq(?). Also, I know atmospheric pressure will affect it, as well as humidity and temperature. How much do these mods and conditions decrease vacuum number (decrease meaning higher pressure)? I don't feel like reverting back to stock to record numbers and go through all the installs again, so if someone who reads this forum as often as I know a lot of you do, could you keep a record of these mods and conditions paired with a vacuum reading at ~800 rpm? Once we establish an average loss of vacuum for specific mods and conditions, we can then assess the health of our engine. All in favor?

@800 rpm 6k non ported motor w/downpipe, midpipe, catback, intake, non sequential, 30C intake, -29mmHg (atmospheric), 60% humidity - 440-445mmHg

Do you think the FMIC with the long pipes and increased volume between motor and outside air would affect vacuum?