What are good vacuum readings at different intervals? Idle? Cruise? etc

12A Nikki

Thanks
-Paul

 

No clue for 12a. You can check my build thread in sig to see mods. I run 18 idle..22 decel. All depends on how much gas your giving it when cruising. Can be anywhere between 0-18 for me

 

My turbo streetport motor sits around 15" Hg at idle depending on RPM. A stockport motor will likely be a bit higher. Cruise depends on too many factors.

 

Stock port 12a should be around 19 to 22 Hg. thats what mine has been at since i bough the car 5 years ago and it hasnt given me any problems.

 

Mine pulls about 18-19 at idle and atmosphere at WOT. Stock port 12a, modded Nikki.

 

the only one ive checked pulled 18 at idle. i later took it apart to fix the dowel pin oil leak, and there was no chrome at all on the rotor housings

 

Looks like I've got an issue then.

It runs pretty darn well, and dyno's at 110hp RW with the stock muffler. I've since replaced the muffler with a borla.

I get 15"hg at idle with the brake pressed and headlights on. Creeps to about 16.5 with the lights off and no foot on the brake. My alternator is kinda big, clearly it's a drag! Rock steady idle at about 13.7:1 AFR. If I lean it out, I get a little issue where if I'm in gear coasting to a stop, foot off the gas, and then push the clutch in the rpms drop to about 500, it leans way out and almost dies for a few seconds. Sometimes the engine does die. Doesn't happen with a free rev, or if I push the clutch in when I come off throttle because the dash pot catches it.


15 at steady state cruise 60-70mph 3100-3500rpm, the slightest hill it drops to 8 or less. I guess this explains why it's hard to keep cruise working at that speed on a little freeway hill.

Slow speed cruise is about 20"hg at say 25-35mph


I'm going to check out my timing system this week. Make sure the weights are working and that the vacuum pods work properly. Seems like I'm down on timing.

If that checks out, I'll try manifold vacuum for the advance. Really just seems like a lack of timing.

Thanks for the info! It's what I needed!

 

the vacuum @idle will change with rpm, so @800 rpm it'll be say 18, but @650 it will drop, and @1000 it'll be higher.

also since its running 13.7:1 at idle, play with the idle mixture, it might be too lean (although i'd take leaner over a random number on a vacuum gauge)

and then thirdly, cheap gauges vary!

 

My ported sleevless 6 port 13b has ~14in give or take at a 700rpm idle, I thought it was bad, but seems like other ported motors idle around the same area

 

New autometer gauge matches my handheld Equus gauge.

Leaner idle causes that off throttle coasting to a stop issue I posted about above.

Just seems like low low vacuum at freeway cruise while it's acceptably high at low mph cruise.

hmmm....

 

Sure enough. My Trailing vacuum advance pod is dead. Which, since the leading and trailing vacuum lines are tee-d together right at the dizzy, it was not only a vacuum leak, but also no advance!

I hooked the vacuum line up to the leading for now. Can already tell it runs a bit better, especially at say 20-35mph steady cruise.

Maybe I'll get some milage out of her yet!

Even though the idle mixture was good on the WB, I richened it up to about 13.2:1 and it's helped my engine braking/push in clutch at stop attempts at dying.

When it happens, the mixture is way lean, 16-20:1 and it slowely creeps back to 13.2 when it happens if the engine doesn't stall.

 

do you live under the sea?

it's disheartening seeing so many people rely on cheap vacuum gauges and use those figures as a rule of thumb, it's been about a year since i saw a vacuum/boost gauge that was semi accurate and that was probably simple dumb luck.

the renesis is probably the only engine that will come close to those figures, no 12A that actually lives above the surface of the ocean will ever see that much vacuum.

about the highest i have seen on any rotary engine(haven't physically tested a renensis yet though) is 18-19"Hg @ 900 RPMs with about 120psi of compression. if you see anything higher, even with brand new engine components, suspect your gauge is faulty.

 

I got 17 out of her with timing/mixture adjustments. 900rpm aswell. :O)

 

I see 19 with the mods in my sig at idle around 900 rpm.

Most engines pull around 20 if they are healthy and have no vacuum leaks. Rotaries
just a bit less.

What you see does depend on elevation and in Charlotte we are just a few hundred
feet above sea level. Seattle obviously it depends if your by the ocean or up a
mountain.

Since Las Vegas is around 2000 ft I'm sure Karack sees it differently.

 

Home is about 700ft. Work is sea level.

My Autometer gauge reads the same has 2 hand held mechanical gauges and work's expensive digital gauge.

 

here it is 2k ft above so the figures are only slightly less, but at about 20ft in sacramento i never saw anything over 19 with these engines even with slightly higher than factory idle settings with a near perfect motor.

i just found the mention of 22 being within range and 19 average/low a bit out of the ballpark completely. porting will lower the numbers further also.