dguy

iTrader: (8)

I'm digging the snide comments, no reason to be disrespectful I just disagreed. I stand corrected, don't let it get to your head

HAILERS

The height of the housing opening is 9.42". The hash mark b/t the sparkplug holes is 4.71" in this picture.

Even without any markings it clear the holes are not equal distance from the hash mark.

That link I posted where at the bottom of the article they suggest looking for an apex seal in the trail sparkplug hole and marking the pulley then rotating the pulley til the Lead sparkplug hole show the same apex seal, and then finding the middle spot on the pulley b/t the marks, is invalid for a series four engine. Been there and done that in the past.


See attached jpg.

scathcart

This method is not accurate (within 1/2 degree) for finding eccentric shaft TDC exactly when compared to a degree wheel. It is out by 1-2 degrees on S5 housings, worse on S4 housings.

This set-up allows TDC to be determined to within a 1/4 of a degree, exactly.

Captain Jean-Luc Picard

I am unsure why you would ever need to be within 1/4 or 1/2 degree when in most cases the cars I use lights on, the mark is not 100% stable, jumping around about 1-2 degrees as it idles. You can only get so close, and you only need to be so close, especially for the majority of FC's who are running the stock ecu which has conservative timing.

You guys are splitting hairs now...these FC owners are not going to sit here and rig up these elaborate setups. But, we will let them decide.

The next thing you know, you guys will be doing writeups on how to calibrate your speedo to within 1/2mph.

If you find the discrepancy between s4 and s5/6 to be too much to stomach, then only use the half of the measurement from the trailing plughole, which never moved. All that would be necessary would be for one measurement to be taken by one of you guys WHO DOES THINGS SO ACCURATELY AT HOME THAT YOU COULD AIM A MARS LANDER, to determine the distance (in degrees or in pulley circumference) between having the rear apex seal centered in the trailing plughole, and the stock 5*ATDC timing mark.

Then once this measurement is made and agreed on we could simply publish that measurement here for all to read, and do away with all this pipe dream foolishness that no one is realistically going to do. We could say "center an apex seal in the rear trailing plughole, mark the crank pulley, measure XXX mm from that point and there is your true timing mark". This would be the mature approach.

OR we can continue splitting hairs and *attempting* to degrade others, in this conversation meant to be a value to the community, and you guys can continue to demonstrate your *******-ery.

scathcart

I don't build street engines. I don't use low quality timing lights.
At 8500 rpm with 250 hp worth of nitrous being thrown into the motor, I don't want to be 2+ degrees advanced. I don't need 1/4 of a degree, but I do need those 2+ degrees. That can cost an engine.

I am stating that your method is not as accurate as desired for finding true top dead center. I am not being degrading. I am not being insulting. I am stating facts.

The whole purpose of this thread was to discuss methods to find TDC exactly to match it to a pulley, or mark your existing pulley for exact TDC. If this is truly a conversation meant to be of value to the community, than lets keep things as accurate as possible. Those who wish to find exact TDC may prefer not to have your misinformation about finding exact TDC clouding their research.

If you have a problem with helping others to work on their cars to the best of their ability, using simple, commonly available tools, then that is your own perogative, though I will never understand it.

CMonakar

^ Great topic. This is something I have found myself coming back to repeatedly. Virtually every method of finding TDC is indirect.

Scathcart,

Can you walk us through how you use the degree wheel and where you purchased it? The tricky part about this exercise for me is that you're really trying to figure out where the wheel marker is in relation to a fixed point on the front cover when the rotor is at TDC, but you can't see the rotor and front cover location at the same time with the degree wheel. Also, with the front of the motor off, isn't there a risk of it getting out of alignment due to a lack of bearing support on one end?

I am tempted to build up a dummy block without seals, cut a big window out of the rotor housing and or iron so TDC is visible with the engine assembled, rotate it into position, and then mark the pulley at the CAS.

lax-rotor

iTrader: (1)

Using the pictures as a guide and the primitive description, we can figure out that the TDC is not located half way between the two marks but on a split of...edit, math is wrong. Redoing it now. 38.99999%/61.000000001% (For convienence sake 39/61. I'll continue the rest in another post so I do not run out of time on this edit.

lax-rotor

iTrader: (1)

Since there's a split of 39/61 instead of a 50/50 split couldn't a replacement procedure be:

Align and mark the pulley from center of both leading and trailing sparkplug holes. Measure distance between them. Apply above percentage to find the TDC. That would seem to me to get you much closer than a 50/50 split.

More to the point, if there's a 15deg split between leading/trailing(I am just using it as an example) then the degree difference between the two approaches is:
1.65deg. This discrepency will only increase with a wider spread between the leading/trailing plugs. For instance: 20deg results in a 2.2deg difference in those methods.

HAILERS

************************************************** **********

I've not a clue what the heck your talking about. Why are your talking timing split???? Odd.

TDC is NOT located (for the front rotor) when a apex seal in the Rear rotor is halfway b/t the two sparkplug holes. Therefore the method of finding TDC in the article I posted in one of my other posts is not valid on a series four engine. It is valid for getting Near TDC, and that's all.

What I suggested doing to find TDC is simply displacing the fluid you put in the chamber. At TDC there will be less fluid. So as you turn the pulley, the fluid first rises, and then as you pass TDC is begins to fall.

Stepping the hose down from the 1/2' screwed in the sparkplug hole, down to a 1/4" makes it easier to determine the rise and fall.

I'm really not sure what your talking about in the two posts above. SPLIT is done by the ECU and has nothing to do with the location of the sparkplug hole location. It's an electronic function. Then again, I've no idea what your talking about.

If you have a engine apart you can index the flywheel/pulley. That can't be done with the engine in the car.

One reason for this post, is that in the past I've recommended using that link in my articles above for finding TDC. Since then I've gotten off my *** and found out why when I followed that advice, the new marks were quite a bit off the original marks by Mazda. It just is not a valid method. Every error made at the position of the rotor gets magnified at the pulley.

EDIT: The article I referred to is this one. Look at the bottom of the article: http://www.teamfc3s.org/info/articles/demystifying.html

lax-rotor

iTrader: (1)

Yeah, sorry about that Hailers. I was kind of tired, and I wasn't refering to timing split, but the split in the sparkplug holes and locating TDC.
Is TDC located when the Apex seal is located at the thickest part of the housing between the leading and trailing? If it is then that's what I'm trying to introduce mathmatically.
I understand, but what kind of fluid would you displace? Engine oil? or would alcohol be more appropriate?
When I was saying split, i was not refering to the timing split that the ECU does. Sorry for the confusion. I was just trying to show that the error of the 50/50 split (Being that if you locate TDC halfway between the leading and trailing plugs you have an error of about 1.75Degs of where it should be).
I'm aware, and I like your method, but there are a few things I'd like to see before doing this (have you done this yet?). Could you supply the pictures of the process when you do it, and how effective you find it. I simply wanted to show that you could probably find TDC mathmatically using the sparkplug hole method and correcting it for the S4. Accuracy would be dependent on the measuring techniques imployed as well as the scale.
I hope that explianed it better. Would that be more accurate or would it still only be ball parking the TDC?

Nick86

iTrader: (1)

Ok, I lost complete confidence in my car's timing a while back (86 GXL) and did the aforementioned "Look through the plug hole for the apex seal" method of finding TDC. Since then I have been chasing something resembling proper timing..... and it has been fruitless. Now I know why.

So, this discussion has made me want to try HAILERS method, but I have a few questions:

- How much oil do you think I'll be pouring into the engine?
- What is the danger (if any) of this? ie - if I end up pooling oil into the housing, is that bad?
- I'm assuming that getting the oil out will be a matter of turning the engine over without the plug in and simply wiping it up. Whatever is left will be burnt.... Correct?


Has this method been proven to work and be accurate - or is it simply a theory at this point?

Thanks!

HAILERS

Use that same sparkplug/apex seal in the hole method to get near. Then what you will be doing is filling just the area of the rotor where the combustion chamber is plus the volume in the vinyl tubes. I'd guess a half quart or so counting spillage.

There is a down side to this. When your through you just pull the two vinyl tubes out and the oil drains from the tubes and the sparkplug holes on to the ground etc. So put a pan under the area. It can be messy.

You don't have to turn the pulley much. Just maybe a inch counterclockwise then an inch or so clockwise. Maybe a bit more or less. You watch the level of the oil in the tubes when you do it and you can see when the oil stops rising and begins falliing.

Then you can rock the pulley back and forth and you'll notice more oil coming out the sparkplug holes. You just work at getting the most out that you can.

The real downside is if you have a working converter. You'll never get all that oil out and what happens is once the engine is cranked a bit, that residue will go into the exhaust. Not good for a converter and you will have smoke out the tailpipe in a large volume. You need to drive it for a mile or to to burn the excess oil in the exhaust.

I consider it accurate. On one car I have with marks still on the pulley, the TDC mark I come up with is within five degrees of the red mark. But I've a couple of other cars with pulley marks pretty much fouled up and I had to correct them.

I used some Outboard motor oil/two stroke from WALLMART. It has color which makes watching the oil level easier.

And I'd do this with a stone cold engine.

Look at it this way. Say you had a 1963 XKE with the straight six dual over head cams. The sparkplugs are on top of the engine. Pull a spakplug and then pour oil in the cylinder. Then rotate the engine.

IF the piston was close to the bottom, then oil would pour out the sparkplug hole til the piston was at TDC. Then as you keep rotating the crankshaft, the oil will start falling as the piston goes down. Your doing the same thing with the rotor. You turn the pulley til the rotor chamber is at its least volume which make the oil in the tubes rise, then as you keep rotating the puley the oil drops in the tube because the volume in the chamber is increasing. Between those two points is TDC with no doubts.

Or you could buy a pulley from RacingBeat with the marks already on it. Not that costly, but I think those pulleys are all undersized.

HAILERS

[QUOTE=lax-rotor;7842698]Yeah, sorry about that Hailers. I was kind of tired, and I wasn't refering to timing split, but the split in the sparkplug holes and locating TDC.
Is TDC located when the Apex seal is located at the thickest part of the housing between the leading and trailing? If it is then that's what I'm trying to introduce mathmatically.
************************************************** ***********

I thought about what you said after I posted and I think I wrote without thinking.

Yes. The *thickest* part is where the apex seal rests when at TDC. In the middle of that thick part.

When I first realized the flaw in the article describing how to find TDC, I took a look and for a while thought about how I could make a mark with the apex seal in the middle of the Trail sparkplug hole, then turn the pulley til the apex seal shows up in the Lead sparkplug hole, but instead of centering the apex seal in the hole, offset it to (I forget) either the very top of that sparkplug hole or the very bottom of the hole. Like the seal just barely showing in the hole. Then make the second mark and divide the distance b/t both marks to find TDC.

But I let that idea drop. It just isn't the way I wanted to go. Then I thought about how easy this would be if this was a piston engine. A straight six with the sparkplug holes at the very top of the head. Like 61-70 XKE type engine. Then realized that it would work on a rotary. No valves for the oil to pass into. Nowhere for the oil to go but into the vinyl tubing in each hole.

Oppps. I guess it wouldn't work on the six cylinder due to the valves.

I've an extra engine sitting on the floor. Mabe in the next week I'lll cobble up a picture.

HAILERS

Nick86. Look at the jpg. Your only filling up the area I've pointed to in Red plus the bathtub combustion chamber and vynl (sp)tubing.

Just in case: the rotor isn't sitting perfectly *square* in the housing because there's no apex seals/springs there. Best that could be done in a hurry.

That is the positon of the FRONT rotor when the rear rotor is just the opposite of this view. The second jpg would represent the rear rotor.

Third jpg shows sparkplug holes.

HAILERS

Here's a jpg of the GENERAL IDEA.

You'd put both tubes in the sparkplug holes and lift their open ends above the rotor. Then, with a squirt can fill the LOWER tube til oil comes out the top of the upper tube. Keep filling until you have a few inches of oil in the top tube.

I stepped the half inch tube down to ?? 3/8" to 1/4" and let the oil get into the 1/4" tubing. Then rotated the pulley back and forth a inch or so while watching the oil level.


I just plugged the tubes in the picture attached and filled them with some oil to give a idea of what I'm talking about.

CrackHeadMel

iTrader: (2)

Isnt an fc pully 360mm in circumference.

i just measured off the stock pully's leading mark to get the marks i needed (TDC and a 14 for idle)

NZConvertible

For a 13B with a CR of 8.5:1, the chamber volume at TDC is just over 87cc (~3oz). So you'll need a little less than that since the chamber isn't completely filled with oil. Higher CR's will have smaller TDC chamber volumes.

I'd try to remove the bulk of the oil after you're done, but whatever's left will do no harm. The engine always has an oil layer on the inside of the chambers anyway.

Correct.

It's simply geometry. It can't fail.

RotaMan99

Im going to check something out but I once read that you can point the keyway in the e-shaft straight level toward the passenger side of the engine and that would be TDC...

Im going to look at my spare parts and see if this is true.

which do we care more about? front or rear TDC? I forget.

CrackHeadMel

iTrader: (2)

nm..

HAILERS

Yeah. You could pull the front pulley and hub off and point the keyway straight towards the exaust. But you tell me how you know, accuratly , when the keyway is Exactly 90* from straight up??? What reference marks are there?. How do would you know your not ten degrees one way or the other.

I've played with this thought before. I sat a engine on a flat surface with the pan and oil pickup off and used a 12"Lufkin scale to measure with. I measured from the surface the engine sat on to the middle of the eccentric shaft then move the scale to the keyway and turned the shaft til the middle of the keyway was the same distance as the measurement from the surface the engine sat on to the middle of the shaft.

I had repeatablility problems. I couldn't do this five out of five tries and have the same result. Sucked.

With the oil method I can do over five out of five IF I don't get an air bubble in the lines. An air bubble in the line will mess with your head.

You need enough oil to fill the chamber plus the volume of the two 1/2" tubes plus spillage. It's best to step the 1/2" tube down to the next size smaller then the next size smaller than that. The smaller the tube the easier to see the rise/fall of the fluid.

Don't use water. Seeps out too fast. You can use water if your fast and persistent.

Again, not good for a converter. You will not get all the oil out. The engine will smoke quite a bit for maybe ten minutes. Less if you drive it right away. The excess oil gets thrown down the exhaust pipe and it'll only burn off once that part of the pipe gets hot enough.

It's not for everybody. It is a bit messy. Accurate. Yes.

TonyD89

iTrader: (10)

Plastic calipers?

HAILERS

That went over my head. I'll bite. What and how do you use 'em?

TonyD89

iTrader: (10)

In the pictures measuring the pulleys. I have never seen them before. Seems a little cheesy. That's all.

HAILERS

Still over my head. I'm not measuring pulleys using the oil displacement method. The point the oil starts falling is TDC. Or rather the point just prior to the oil falling in the tube.

Then mark the pulley opposite the fixed pin. Then measure the diameter of the pulley (I've dial calipers) and then find the circumfirance and divide by 360 to figure out the distance five degrees is and measure off from the TDC mark to the Lead mark.

EDIT: Ok. While writing this I realize that is what your talking about. Measuring the pulley diameter. Yeah, I used dial calipers.

mario1386

one qeustion how you put the cas in time?im still wondering how to put it on time