Just rebuilt my motor. (S5 TII)



The motor will not start. Fuel is there. So is spark.



I did a small to medium street port to the intake and exhaust. would i have to change timing to get it started?

I have the FD Apexi PFC.



The only thing i could think of was maybe one or more of the ends of the apex seal (RA super seals) flipped or moved itself. But i have 90psi from both rotors. Would i have more after a fresh rebuild? I was thinking i should have around 110psi. The only thing i reused were side seals. How can i check this without re-opening this motor to make sure it was done correctly?

 

oops...meant to post this in the engine building section. can it be moved there by a moderator and this post deleted?

 

I read what racingbeat had to say about compression...



They say that normal compression Range is between 110 - 150 PSI



minimum compression is 75 PSI



And the maximum acceptable pressure differential between rotors is 20 PSi....

anything less then 75psi will still start the motor, But it will be hard to start once it has warmed up.....

 

I drove for a year on an engine that did about 30psi cold with no problems.



Also had an engine that was 75/55 and was a pain to start hot and almost impossible cold. The carburetor needed the idle screw turned up 2 full turns to get it to idle at 750, on the previous engine idle was set at 1100!



The way I see it, then, there is compression and then there's compression. The compression test doesn't give you the full story of the engine's strength but it gets you in the ballpark. The engine that hated running turned out to have pretty much no chrome left on the housings between the exhaust port and the roughly 6 o'clock position in the rotor housings, so it had enough compression to appease the tester but after that it would just bypass.



As far as new engines are concerned, sometimes they're cranky until they get broken in.



Also: You have fuel, you have compression, you have spark, do you have timing?

 

yeah compression isnt tested with a normal tester very well, those things vary so much its pretty useless.



and you're really looking for even bounces over a hard number anyways.

 

from my experience withe the regular compression testers on A ROTARY you should get 3 pulses or 30 for a total of 90.

 

from my experience with the regular compression testers on A ROTARY you should get 3 pulses or 30 for a total of 90.



if you are missing one pulse you could have a bad side seal(should look like this 30,30,0), if you have two pulses low you could have corner seal or cracked apex (30,20,20), if you have two really low numbers it could mean broken,warped or stuck apex (30,10,10 or less)



the results will look like this

rotor 1

30+30+30=90 good

rotor 2

30+15+15=60 bad



the numbers can be lower that 30 but they should be fairly close



on avarge the rotors should not be more that 20 apart .also a long time of wear can make the motor have slight lower compression so dont get too scared .....hey people feel free to correct me if i am wrong with any of this and feel free to add





but all that is besides the point sentwo hey make you that you alinged the crank trigger sensor when you put it in and that it was on the sencond mark on the crank

 

the pulses were 3 pulses of 30 on both rotors. i know that a regular compression checker is inacurate for a rotary. but its close enough. i set timing a few times. maybe im setting TDC wrong so my timing is off. thats all i can think of. but i havnt had a chance to go check in a few days.

 

If you've pulled the schrader valve from the comp tester it will be plenty accurate. 30 psi is far too low, and for the record you do NOT add each pulse together to find your total compression.

 

You probably have a timing issue with your distributor. Make sure your at TDC and then pull your distributor cap off and make sure your rotor is pointed at the L1 on top of the cap. If that is ok then check for fuel and spark.