I've been battling this for a couple weeks and thanks to the guys that have helped. Got a handle on it but it still is puzzling me. The motor is a 90 NA in a SCCA ITS class roadracer. All the emissions crap is removed, it runs a RB dual outlet header through dual 2.25" back to a collector at the rear axle and single 3" out the rear (common ITS setup). Six ports are removed. All the electrics are stock and all check out according to a factory manual. No vacuum leaks and compression is good. Fuel system is spot on and seriously custom. Fuel pressure is set at 50psi idle and can go to 80psi if needed. Injectors have been cleaned and flowed and are balanced.

Had a full throttle miss but that was cured with new plug wires (think I had the originals) and a set of plugs.

The problem is that the car starts and idles fine but it likes about 10* of advance to rev right. When the timing is set to stock specs the idle is a bit rough and the motor won't rev out. It misses badly and shakes violently. Anvance timing about 10* and the idle smoothes out and it revs cleanly and crisply. Why is this motor liking the extra timing? Does it indicate a problem or is it a matter of the mods that are done? Going to the ARRC next weekend and hope to get some answers there from some racers but would like to put this to bed. Any help? THANKS!

Chris

 

I saw a while back that you were having some problem with the RAcing Beat pulley and the marks. How about taking your original stock pulley and put it back on and see what happens? Also I saw where you showed someone how to set their timing, so I know that you know to do it at idle(750). Have you ever taken your timing lite and gently reved the engine above 1000 and noticed if the timing advanced and then returned to normal as the rpm returned to 750. I'm sure you have. The original pulley is the only real idea I have on this timely issue. Don't race. 7500 in forth with stock acv, airpump and the airconditioner on, uphill. Self imposed redline. Humor. You have a truly interesting problem.Edit... You do have a stock engine, don't you? Not ported, right. If ported that could be the answer.

 

If you do not have stock pulleys, you probably have lost where TDC is. Go to this URL to find out how to relocate where it is, set up your pulley to match it when you find it, and reinstall your CAS to the newly located TDC if you do not have sufficient adjustment range to set the timing to the correct value (5 degrees ATDC, I believe). Here is the URL:
http://www.teamfc3s.org/info/articles/demystifying.html
Lemme know if you have any further questions.

Irv, Keith's dad

 

i wish i could help ya with your timming issue...but,i just had a question about your exhaust..are you just running straight pipes?or a muffler?and maybe presilencers also?if yes,what kind of muffler?and,how is the noiselevel?i guess your probably just racing your car,so maybe streetability is not a issue...
thanks

 

I put the stock pulley back on and set it up correctly. The RB pulley did have 5 marks instead of 4. And those marks were about 20* off. Mazdatrix is going to exchange it for me. When it's set properly (with the stock pulley) I get the lopey idle and miss. If I advance the base timing about 10* it cleans up. I do get advance as I rev the motor. The motor has completely stock internals as the rules require.

Thanks for the URL Irv. My buddy and I were thinking about that exact thing the other day.

WANKLEHEAD, the exhaust runs straight out to the collector and then through a 3" Dynomax Ultraflow. It's a straight through glasspack. The setup is very loud. I wouldn't want it on a street car and Johnny Law would probably have a fit. At idle it's quieter than the open header was but it's about the same at WOT. If I wanna autocross the car at all I'll probably have to put a Supertrapp on the end to make our local dB limit.

Thanks again guys.

Chis

 

IRV, you's a genius! Just as I'd hoped, after finding TDC according to the tech article in your link, the new mark was right about where I was having to set the timing to get it running right. The process was VERY easy and I'd recommend anyone that is at all curious about their timing to give it a try. THANK YOU, THANK YOU!!!!

Chris

 

Chris,

How did you find which Apex seal to locate in the rear rotor? It says to locate a seal, not which one.

I'm guessing I will get the pulley to almost TDC, then locate the next apex seal that goes to the trailing spark plug hole and go from there.

I'm having similar problems as you. I think my timing is retarded too much. The engine doesn't rev freely under load. Runs okay without load though. I'm guessing if I find REAL TDC and adjust the dwell on the timing gun to 5 degrees I can set the leading ignition.

 

I brought the pulley around to the mark that was on it and then slowly turned it slowly toward the advance side until I saw a seal in the leading hole. And then backed it up to the trailing hole. It's not HARD to see the seal in the trailing hole but you need a mirror and good light. It helps to find it in the leading hole so you can kinda expect when it'll pop up in the trailing hole.

Good luck.

Chris

 

JRussel,

I think I mentioned this to someone in an earlier thread, but here goes. The rotors spin at 1/3 the speed of the crankshaft. However, there are 3 rotor faces (the triangle) on a rotor. If you think about it, you will realize that each rotor face position will always match to the EXACT same spot on the crankshaft. That is to say, at TDC, the front rotor face will be exactly at the peak of its compression stroke. It doesn't matter if it is number 1 rotor face, number 2 rotor face, or number 3 rotor face, that is the position that rotor face will be in. For the purpose of smoothness, the back rotor face is at the peak of its compression stroke at 180 crankshaft degrees. Since this is the case, when the front rotor face is exactly at peak compression, the rear rotor face apex seal is exactly lined up with the center of the front rotor face. Doesn't matter which rotor face, it always is. Therefore, if you find an apex seal in the leading or trailing plug hole on the rear rotor, it's the correct apex seal because they are all the correct apex seal (there can be no "wrong one"). If you need to see a picture of this, I believe there is an animation somewhere, like on the "How things work" web site. Let me know and I will find it for you. Have a good day!

Irv, Keith's dad

 

C. Ludwig.....that is a really interesting post and it leaves a lot of unanswered questions. Why was the original pulley mark off???? When you get your replacement pulley from Mazdatrix, I just know you will be comparing the marks on it with the original pulley marks, so will you let us know what you find out? I'm saying, was the mark off on the original equipmet? Or was it the eccentric shaft being keyed off? Or is it the pulley attach bolts, the small ones, four, being wallowed out and not aligned with their proper holes? How in the world does something like that happen? Maybe the *original* pulley is off some other year rx?

 

I just found my TDC today... It was a long ways away from the leading or trailing timing marks. To the right of the leading mark if looking from the top. I have a stock pulley too.

How many degrees is the leading mark supposed to be from TDC? I seem to remember leading was 5 deg after TDC and trailing was 15 deg after TDC. I don't know why I'm thinking those numbers though...

My leading timing mark is a lot more than 5 deg to the left of my new TDC mark. At best guess it's something like 30 degrees.

Lining up the CAS marks and installing it while the pulley is lined up with the leading timing mark isn't working at all for me. The timing seems to be way off. Off enough that the car won't start.

The only thing I have done to the car is downpipe, new engine(that I am trying to get running), ported&polished intake/exhaust ports, cat-back, and removed ACV, airpump, cat. conv.

Any ideas on my timing problems? I keep thinking I'm doing something wrong, but I've gone over it at least a dozen times and it's the only way I can get it to start.

 

Well my motor is a second hand Atkins rebuild. No idea on the origins of the parts. It is a 89+ motor and I'm pretty sure the pulley is original to the motor. JRUSSELS motor is also an Atkins. I was thinking maybe there is a procedure to time the rotating assembly when it's built and they aren't doing it properly. I'll have to go over my manual but that's the only thing I can think of and it doesn't sound real promising.

I will compare my new pulley when I get it and post back. The first RB pulley though was a real freak though. It had 5 marks instead of 4 and they were WAY off the stock marks. I don't think the bolts are wallowed out on the stocker, but I've never had it apart.

JRUSSEL, the trailing mark is at 10* ATDC.

Chris

 

jrussell.....I'm butting in where maybe I should not but........Hold the crank angle sensor in your hand with the top black cover taken off exposing the internals. Now look at the bottom of the cas and align the timing marks, the raised mark on the body with the dimple on the rotating shaft. Hold it firmly in that position. Now if you look down in the top, you will see twenty two teeth on the lower part of the shaft. One of those twenty two teeth Will be aligned with the center of that black decice with the red and white wires going to it. Make a mental note of which tooth that is. Now, with the pulley mark aligned with the stationary wire marker on the housing, insert the cas. You notice that the gears turn while inserting the cas. Big deal. With the cas fully inserted, now turn the cas body until the internal tooth that you made a mental note of, aligns with the black device with the red and white wires. You should be within just a couple of degrees of being in time. The car WILL start. You need a timing lite for the exact timing. You should not have to turn the cas more than a fraction when you time it with the lite. You probably know the above already, just thought maybe someone else might read this and it could help them with there timing someday.

 

Got it! Car runs like a stuck pig now. Was BSing on another board about removing the OMP. Guy asked me what I did to fool the ECU when I removed the OMP to run premix. "UHHH, nothing?":o Plugged the OMP up and it runs like a champ. Without the OMP it had gone into limp mode and wasn't firing the secondaries among other things.

Once I took care of that problem I could lean the fuel out a bit (was running lots of fuel pressure in an attempt to make it run right before I realized the secondaries weren't firing), and brought the timing back into spec. The idle came down some too with everything working the way it's supposed to.

I'll be working on a resistor pack to simulate the OMP so that I can remove it all together. Right now it's just zip tied in the car. I'll post my results, unless someone has already done this and now the answer?

The car goes to an autox in Nashville this weekend for it's first shake down. And then to VIR for an open track event the second weekend in December. Anyone in the areas stop by and check it out.

Thanks again for all the help!


Chris