jacobcartmill

iTrader: (6)

i have been breaking my engine in for about 1100 miles now and i started boosting about 5psi after 1000 miles per BDC's advice. its an atkins reman that i bought from shane@rotaryworks and i made sure that i had decent compression before i started boosting. it was at about 95psi with 1000 miles on it so i started driving normally with the occasional spritited driving boosting around 5psi.

now that i have about 1100 miles, i have like 75psi on both rotors................ maybe my compression tester could have been reading wrong, but i'm worried. i have my OMP blocked off and i'm running about 19-20oz of tcw3 premix in my tank. could this have anything to do with it? forget the dyno post, i'm worried about my engine!

-Spool_TSI-

Did you happen to use a normal compression tester?

We used a normal one from the local parts store and it showed 60 on both rotors, yet the reman had been broken in well and it is now a very very strong motor.

I don't think those work the greatest on these engines.

P.S. looking at your mods list I'd get some larger seondaries (720cc) before you do any real good boosting.

jacobcartmill

iTrader: (6)

i dont know exactly what you mean by "normal" but it was actually a snap-on one where it has a quick disconnect and you can change the hoses that have different spark plug threads on them.

however i think that maybe the springs in these older snap-on testers may be too stiff. actually when i changed hoses from a deeper threaded "sparkplug hole" hose to a shallower one, i got 10 more psi (the first test was 65psi...)

i'm still worried because the mechanics here have used that compression tester several times. but then again the motor feels very strong and there are even pulses on each rotor face so i dont know..

jacobcartmill

iTrader: (6)

yeah, i'm keeping it at 5psi til i'm over 1500 miles (and by that time i'll have some more fuel)

-Spool_TSI-

Well by normal I meant what you did use. Because there is a really bithin expensive Mazda tester. but its not worth it. I have heard of a lot of people having problems with the "normal" testers. Just use a few different ones and see if the results change.

jacobcartmill

iTrader: (6)

yeah i'll try the one that i got 95psi with last week. man if this engine really has 75psi this is going to be the end of my life

jacobcartmill

iTrader: (6)

i havent done a compression test since i blocked off my OMP and started running premix (20oz per tank)

could my slightly low numbers (~80psi) be because when i am compression testing, i am pulling the EGI fuse, which means there is no fuel/oil being injected? the stock OMP injects oil during cranking correct?

i'd like some input on this before i start bugging someone for some money

WAYNE88N/A

If you feel like you're getting stronger as the miles build on the rebuild, and she's running good, don't lose sleep over compression numbers.

If in doubt over the premix's ability to seal for you, inject a little oil into the housings & turn her over a couple of times by hand, then re-do the compression test. Post the numbers, I'm intrigued too now (about the premix/ compression thing). Mine's got 2200 miles on her now and runs like a bat out of hell, so doing a compression test is far down the list of worries...

jacobcartmill

iTrader: (6)

yeah my car is running real strong at ~6psi (as strong as you can expect for 6psi) and pulls good, i just kinda did the weekly compression test for my break-in and got a little worried.

rxseven

Does it fire up without much cranking? If so, you are in the clear since that would be a symptom of low compression. How about hot starts? Instead of seeing the pulses on the compression tester, just take the max reading you would get in one rev without pushing in the release button. If you are over 100psi, you are in decent shape.

jacobcartmill

iTrader: (6)

the cranking is not bad, i dont have to crank it for a minute straight or anything. it feels like it has around 90psi or so and still floods occasionally on hot starts, but nothing out of hand.

the compression certainly doesnt feel perfect, but doesnt feel too low. and it also pulls well and feels strong during accel (~5psi)

WonkoTheSane

iTrader: (2)

Just out of curiosity, since it was brought up (Not threadjacking, i swear!) what is the normal crank time for a EFI rotary? Mine takes a good two to four seconds of crank when it's cold, as does my dad's carburated 85, but only about twoish when it's warm. My dad's carb'd engine starts RIGHT up when it's warm, though.. we're talking about a half second to a second, while mine takes about two.... I'm pretty sure i'm running rich (aren't all of us NA guys?)...

Is this normal? Do I have a problem? Is my starter just getting slow?

Or am I just being paranoid?

OverDriven

Should start in 3 revolutions of the engine. My 87 TII takes about 2 seconds at the most.

-Joe

jacobcartmill

iTrader: (6)

yeah it usually takes about 2-3 seconds to start. maybe 4 if its trying to flood on the hot-start. i'm not expecting the startup and flooding to be totally gone til i'm at about 2000 miles since i have crappy used rotor housings.

but yeah, the ideal engine should take 3 revolutions to start. my NA would catch pretty fast.

Digi7ech

iTrader: (1)

How did you do the tests?

Did you get the engine to running temp and then test it?

I'm thinking you did the 90psi test in a different way than this test.

Cold engines don't give the right numbers.

Mine after running pulls 65psi on all faces and 90psi total per rotor housing right now and I have 8 miles on the engine.

jacobcartmill

iTrader: (6)

and doing the same compression tests as i'm doing now, it would get about ~95psi on both rotors (back on my NA engine)

jacobcartmill

iTrader: (6)

are you premixing or do you have the stock OMP?

i did one test with the engine cold and one test after it was up to operating temp. got 75psi on the first and 80psi on the second.

i'm thinking the whole problem is that its getting no oil during cranking when doing this test because i have the EGI fuse out and i'm premixing, so no fuel/oil is getting injected for the test to help the compression. can someone verify this?

Digi7ech

iTrader: (1)

I have some premix in my gas as a precaution but I confirmed this weekend that my OMP is functional.

jacobcartmill

iTrader: (6)

we need to find someone that has no OMP and running only premix to see what their compression test results are like.

ddub

Hmmm this is interesting. Because I compression tested my car befoe my MOP (btw it's MOP not OMP) and got 105 psi. After I blocked it off and was premixing and did some other mods, bla bla bla long time passed so I wanted to test again and all of a sudden I was getting like 85/90 psi, 95 max sometimes. We thought the compression tester I was using had a small leak in it, which it does seem like, but we still didnt know why it went down so much. Maybe this was the cause. I'm interested in knowing too.

Digi7ech

iTrader: (1)

dude it shouldn't make a huge difference.

I would assume that using premix may up the numbers a fraction but not much to make a difference.

It's not like the ATF or oil trick where you put an ounce in the chamber to build compression.

It's spraying small amounts of oil in. 100:1 etc.....

ddub

That's true, but there still is no oil in there at all when doing the test.

WAYNE88N/A

Like I said- inject a little engine oil to simulate OMP operation, if you're that freaked out about it...Considering a compression test is something you do for troubleshooting when she's not running right, I can't understand why you're so worried about it, jacobcartmill...

jacobcartmill

iTrader: (6)

not when you have the EGI fuse pulled doing the compression test my man.

Terrh

iTrader: (7)

when my carb'd FB was warm, you could just TOUCH the starter and it would fire up.

cold, however, was a different story.