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Naturally Aspirated Performance ForumDiscussion of naturally-aspirated rotary performance. No Power Adders, only pure rotary power!
From the "12A" to the "RENESIS" and beyond.
Sorry for the delay, and thanks for all the help thus far.
So compression #s :
Cold engine - ambient temp 58 deg. Rotor 1, 50-55psi. Rotor 2, 55-60 psi. All nice even controlled hits.
Hot engine - compression figures are exactly the same as cold.
When cold, 1 pump of the gas, and 1 revolution of the engine, and it fires right up. No problems, no hesitations, no symptoms of any problems at all. Elec. choke opens, and it drops into idle absolutely perfectly.
While driving (did 50 miles tonight), it runs, accelerates, decelerates, and idles just as it should. I have some tuning to do, but other than that it gives no indications that it is just about to leave you stranded.
As soon as you turn this thing off, it will not re-start.
I did not pour any oil down the carb tonight, but I assume it will fire right up, as it did when I was trouble shooting before.
I did not ever compression test the engine before I tore it down. But it ran, started, and started hot absolutely fine. I had no problems pulling into a highway gas station, turning it off, filling up, and firing it right back up......wtf.
So all corner seals were changed to solid, but all the old key hole seals were missing the rubber. I would imagine those were sealing even worse than solids.
1 - 1 pc carbon apex seal was changed. All other seals were almost new and measured out to be almost exactly the same height as the brand new one.
1 side seal was changed. I ground it down and it fit as it should. All other side seals showed no wear, and were the same height as the new one.
Again, when running, it runs like it should. Good power to 9k.
Im stumped.
I am going to assume that the corners seals need more wear time, and keep driving this thing 50-75 miles as much as I can/the weather permits.
What could I have done to screw this thing up/cause these problems?
If it ran perfectly before, why not now?
I know the compression # are extremely low, but it ran before, with zero problems.
A few more things.
The engine is not flooding with fuel. I pulled the fuel pump fuse and tried starting the car (hot) with starter fluid. No deal.
Pulled the plugs, crank the engine, no excessive amounts of fuel come out. Practically just vapors.
Open the throttle blades up and peered down into the carb with the fuel pump running (engine off) and there is no fuel going down into the engine (not overflowing the carb).
But tomorrow afternoon it will start...
Help
I have plenty of pizza $ for anyone who wants to stop by. Nice big heated garage with lifts.
The car starts multiple times cold. Did it 6-7 times in a row. Starts every time.
One thing to mention, when hot, the engine does not turn over as fast, as when it is cold.
When cold, voltage at battery/alt/starter is 12.5 (when running 13.9)
I have a huge old battery jumper and its regulator is broken (so it puts out 16 volts all the time!), and when hooked up the engine definitely spins faster, but it still wont catch. It spins faster with the jumper hooked up and hot, than just battery when cold.
Back to the things I tried today:
All on a cold engine, car started every time.
Heated the coils to 170 deg. No change.
Heated the cap/rotor to over 200 deg. No changed.
Heated the MSD boxes to 150 deg. No change.
Good spark on all plugs.
Heated the starter to 170 deg. No change.
Started the car and let it run for 30 secs, 1 min, 2 min, 4 min. Shut it off after those time frames, and it started right back up. The 4 minute was showed signs of a slowing rpm.
After the 6 min run (fans turned on/fully up to temp) the car would not start.
I am now going to start video taping the startups and no starts so you can hear the engine slow down.
I have another good battery (big *** Bosch out of my audi) and am going to swap it out now. It is only 1 yr old. And the last one lasted 12 yrs!
The only thing that jumps out to me is 'all corner seals were changed', did you measure side seal to corner seal clearance? Did side seals go back in the same slots they were originally in?
^ Yes, all seals went back into where they came out of. Side seal to corner seal was perfect fitment. I de-carboned the slots/rotors, and made sure everything was springy/working properly.
New Monkey wrench to the equation!!!!
When I hooked up the larger battery, the engine spins much faster. It will start hot, but extremely labored.
Re-tested compression (with the better battery) and found the front rotor to be hitting at 120ish.
The rear rotor hits 120 2-4 times, then consistently goes down to 60ish. But it doesn't just drop. It goes , 120,100,80,70, ect... and doesnt go any less than 60.
When compression testing the front rotor, it spins extreamly fast, and hits 120ish every time.
No voltage drops anywhere.
If i hook up the old battery, it spins much slower.
Could the po have put in the wrong starter? Is there a mazda starter that they could have used, but not provided enough torque?
I will check the part # on the starter now.
Also going to load test the old battery, but it seems like either 800 cca isnt enough, or its just shot.
What RPM should the engine be spinning with the starter?
Well starting hot even if laboured is good progress.
120psi on front sounds good. Can you measure compression on the three seperate cycles? If its down on just one face - indicates a side seal issue, two faces - indicates apex seal issue.
All the carbon was probably aiding compression before rebuild.
I dont know about the starter but if it fits i'd say its a rotary starter. High torque starters are available.
All hits are even, and all jumps on the compression tester are in succession. No erratic, out of phase noises.
I always premix 1/1.
I installed a 13b na starter, as it was suggested because it has one more tooth on the gear, (12 as opposed to 11 on the 12 na starter) and spins the engine over faster. This does make a difference, but it still is extremely labored. I have to hold down the gas pedal, and give it a few pumps of gas. sometimes it starts, sometimes the battery runs down.
I know giving it gas could possibly flood it, but its definitely not the case here, as i can crank and crank with no change in compression noise, but as soon as I pump the pedal, it gives sign of firing.
I will compression test tomorrow, now with the new starter, and start video taping my progress (or lack there of!).
Do a comp test and then add a squirt of oil into each chamber of each rotor and retest. It will give a better idea of the seal strength and whether they are the problem or it's something else.
What is 1/1? 1 oz to 1 gal? Is that about 100:1? I dont get US measurements (if you can call them that!?)
I have seen high torque starters advertised in NZ on trademe.co.nz, none seem to be on there currently. I guess if your starter is in good condition it should be sufficient.
Yes, 1 oz to 1 gal. Probably a bit higher, as I never run down extremely low. 1 to 1 is the lazy way to say it, but im merican, so lazy should be implied.
Battery cables are all new and of good quality. (car is a ground up restoration).
When I put in the new 13b starter, I sanded all areas of metal/metal contact, as well as ran a test ground right to the battery with no change in starter rpm/voltage drop.
I have a photo rpm reader, so I will compare the 12a and the 13b starter rpm ability as well.
I was unaware of the rpm's vs. compression readings, so hitting 50-60 psi at a low rpm is correct.
Had a local rotary expert stop by and confirm low compression.
Its getting worse, as today it was down to 40-60psi.
Both our testers read very close to being the same.
Starting to break up under load when driving hard.
Oh well. Probably will go back to pistons (sr20) and keep it in the nissan family, but theres a few built 13b's floating around my area.
Gonna just leave this in till its totally dead. Hopefully it will last through the up coming summer, as I have too much planned to take on the swap. 13b is much easier, as I will only have to do ecu wiring and downpipe/intercooler work.
But the sr is about the same amount of work as well. Its all been done before, so its alot of plug n play.
Oh man sad to hear. Im sure with some better quality parts and your skills you could get it going real nice under rotary power.
What do you think is losing you compression? The carbon seals breaking down for some reason? Did you use apex seal springs for carbons? These are different to standard springs i believe.
On a holley its when the float level is set to high and the boosters are "leaking" gas even when idling. The throttles are shut so the vapor just sits in the barrel. Makes it run rich and has given me restart problems in the past where you have to crank the car with the throttle open to get it to start.
I run an edlebrock, which are notorious for having the floats set incorrectly out of the box, but I know i set it to 7/8th. Cant hurt to try a bit less.
I have unplugged the fuel pump when hot, and let it run out of fuel, with the same no hot start condition.
I have also run fuel pressure as low as 4.5 (down from 5.5), with the same symptoms.
And my afr says im not pig rich (16-18) at idle.
edit: I can also toss my RB 465 Holley on there and see what happens. Car ran ok with it, but it was not big enough.
^ Dropped the float level, turned down the fuel pressure. Nothing changed.
Meh...Just dropped $315.00 on another set of (used) irons, water seals, and bridge templates...
Gotta be up and reliably running by spring!
Its too temperamental to trust right now, and twice it just decided to stall out at a stop light!
My area has way too many dumb ***** who will crash into me if Im stalled for more than a min!
Pretty funny though. Popped the hood, dumped the oil, cranked, fired, and left the intersection like a bat out of hell will a stupid huge smoke cloud engulfing everyone!!! F'em.
I just dont have the time to do a full on engine swap this spring/summer. 2 other cars have to get done! One being my daily, with a full auto trans overhaul! Has to hold 30lbs of boost
I will check back in a week or 2, with pictures of the teardown and wtf is going on inside the old engine.
Im going to stick with the edelbrock as its super simple to tune, and I already have it. It ran really well 2.5 seconds before it dropped the apex seal with it, so Im sure its not the problem.
Its either something with stuck seals, or I opened up the secondary bridges too far downward/upward, and my compression is escaping into my intake cycle.
I really dont fu@king know...
I bought fresh irons and this bridge template:
So hopefully I can have a running car for the summer.
If I am competent enough
Going to do more reading on port timing and why ports go where till the parts arrive.
Hopefully this template is compatible with my exhaust timing, as my secondary ports look exactly like the templates I just bought??? Will half bridge the primary's(the upper half).
Dissembled the engine and found nothing in the way of an explanation for low compression.
I did how ever find other problems. Mainly my rotor bearings and e-shaft is now completely shot.
I am going to say the cause is the removal of the check *****, and adding the weber 200 oil bleeds.
I raise the oil pressure by crushing the regulator and shimming the bypass, but there must not have been enough oil pressure to feed into the rotor bearings.
The front and rear bearings are fine/looked the same as when I installed them.
Oil pressure on the gauge was where it should have been (90-100 cold idle, 20-30 hot idle, 100ish at high rpm's).
Also, the rear main eccentric gear was not machined down far enough. It was self machining on the face of the rear rotor bearing.
So Im back to why the f do I have low compression, and wont start hot...
All the seals look perfect.
Let me know if you would like me to check something in particular.
Everything in the oilpan is babet or metal from the bearing machining. All the seals are within spec.
02-20-16, 08:36 PM
20160319_204538 by thomas telesco, on Flickr
20160320_125436 by thomas telesco, on Flickr
20160320_135141 by thomas telesco, on Flickr