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Jon Hujbin (sp?, home built four rotor in the 2nd gen build thread) used oil in the chamber and a clear hose/hoses in the plug holes. TDC is when the oil previously dumped in the chamber before turning to TDC is the highest in the hose. Kinda like a water level.
Thanks guys good info. ACR-RX7. You clearly know your stuff and have all the gear around you to do what I need to. I am stuck with more basic tools and good old fashioned measurements! I see on a piston engine there is a very small window where the pulley might loosen at TDC due to the rod going over centre. Not sure how that works out on rotary though? I don't get where the bleed is happening. Bleed across the plugs would surely be much more than 20degrees BTDC? Anyway. That aside this was something I noticed when trying to stab in my CAS as my timing light shows up I am 15-20degrees advanced on L1. Checked with two lights twice both give the same result. Yet, lining up my pulley marks and CAS all looks good. I then noticed it felt like TDC on the engine when rotating it by hand was around 20degrees advanced from my TDC marking. So I am here trying to get to the bottom of it. There looks to be some error in the pulley marks referring to some old images Banzai racing posted. So trying to figure out why mine are in a different place to start with. But they would in fact put the timing out even further!
So basically I need to confine where TDC is first off and I can go from there. Need to figure the best way to get within a degree with the engine in the car.
I was wondering if I could pull a plug and connect a hose and syringe to the end and rotate the engine and see when the syringe stops moving to get TDC. Maybe a drop of oil in the rotor first to seal the tips better. So what you have described is pretty much that. Do I need to entirely fill the rotor? Presumably not but a good drop? Then rotate forwards and back around TDC a few times and split the difference on the markings if any? Or take the marks when rotating the engine backwards only to cater for potential gear play as mentioned earlier?
Cheers
Lee
Not sure how that works out on rotary though? I don't get where the bleed is happening. Bleed across the plugs would surely be much more than 20degrees BTDC? Anyway. That aside this was something I noticed when trying to stab in my CAS as my timing light shows up I am 15-20degrees advanced on L1. Checked with two lights twice both give the same result. Yet, lining up my pulley marks and CAS all looks good. I then noticed it felt like TDC on the engine when rotating it by hand was around 20degrees advanced from my TDC marking. So I am here trying to get to the bottom of it. There looks to be some error in the pulley marks referring to some old images Banzai racing posted. So trying to figure out why mine are in a different place to start with. But they would in fact put the timing out even further!
Two things:
1: Are you 100% sure you stabbed the CAS correctly? I mean without any doubt. It's been awhile, but I think 1 tooth is about 20 degrees. Did you pull the cover on the CAS to make sure it was lined up? Have the pulleys been swapped or changed at any point in time? This is critical. I do feel like you are falling down the rabbit hole on this one, instead of simply having the CAS installed incorrectly.
2: The seals are not perfectly airtight. When you roll the engine over, the seals bleed the pressure into the next chamber, or crankcase if it's a piston engine. At cranking speed, and when running, they seal just fine, but not when slowly rotating over by hand.
Think about it this way, during a cylinder leakdown test on a piston engine, upwards of 20% leakage is considered acceptable, in some cases. You will never have a 100% perfect seal. In fact, valves in a piston engine do not perfectly seal every single time during a combustion event. There is always a tiny bit of leakage. The place where the air goes is right past the gaps in the side seals and apex seals. In a piston engine, the piston rings have end gaps. This is to allow gasses to get behind the rings and push them into the cylinder walls. It also allows for heat expansion.
If these gaps were not present, you frankly would have a hell of a time turning the engine over by hand at all. You would compress the air and the engine would keep springing back at you. The effort you felt subsided because you reached a point where all of the compressed air had bled out and you were very likely at TDC, where the effort for rotation is the least.
So basically I need to confine where TDC is first off and I can go from there. Need to figure the best way to get within a degree with the engine in the car.
I was wondering if I could pull a plug and connect a hose and syringe to the end and rotate the engine and see when the syringe stops moving to get TDC. Maybe a drop of oil in the rotor first to seal the tips better. So what you have described is pretty much that.
Nope. The apex seals and side seals are not tight enough in any engine to test this way.
Do I need to entirely fill the rotor?
Yes.
Presumably not but a good drop? Then rotate forwards and back around TDC a few times and split the difference on the markings if any? Or take the marks when rotating the engine backwards only to cater for potential gear play as mentioned earlier?
Cheers
Lee
Gear play really doesn't play in at this point. If you do have substantial gear play, the engine is trash. However, after trolling for literally 20 minutes, I found the post where John and his 4-Rotor FC find TDC.
I'll close with this. Make sure your CAS is in correctly. If it is, and your marks are still off, then try John's method. This is as good as you can get without pulling the engine apart, or using a scope.
Tell ya what. I have a factory sealed engine in my garage that has never had the CAS out of it. When I bought it, it still had a nylon cap on the mounting bolt, so I will pull the CAS cover off and line it up with the marks on the pulley. I can take pictures and give you an idea of where it all should line up, but I'm willing to bet that someone already has this information out there.
Tell ya what. I have a factory sealed engine in my garage that has never had the CAS out of it. When I bought it, it still had a nylon cap on the mounting bolt, so I will pull the CAS cover off and line it up with the marks on the pulley. I can take pictures and give you an idea of where it all should line up, but I'm willing to bet that someone already has this information out there.
Thanks again ACR_RX7. Good info. I will check out Johns thread again. I followed it most of the way through! I think I will have to try this though. I have been trying to get an image of an installed CAS with an engine aligned on the L1 pulley mark but not found one confirming this was the case. The pointers hardly move when you install it then? My pulley leading mark and pointers line up just like this. The issue is this puts my timing way off when I put a light on it. So something is not right. Not really enough CAS adjustment to get the timing back in on the light and if you try the engine doesn't like it. I would guess the timing is in the right ball park and somehow my pulley marks are off. You may not have read the full story over the various posts. But, long story short. I got a junk FC with a 20b in it in stock form so I am led to believe. Swapped it into my FD. Changed the front trigger wheel but left the hub on which I assume is a 20b one but now I am starting to wonder if somewhere down the line it got an FC one fitted? I transferred the 20b marks across to the FD trigger wheel by mating them together and assuming the marks on the original pulley are correct mine are in 100% the same place. Plus I added TDC using a protractor for good measure. So, car idles pretty well if a little rich and possibly runs a touch warm for my liking. Had a break in dyno and made 420bhp ish flywheel at something like 5000rpm and 8psi boost. Which seems reasonable. Nevertheless I decided I wanted to check my timing before messing with any timing maps and it came up 15-20degress off. So I have been trying to figure out why since! Electrics are all wired correctly as I double checked last night. So there is either a global correction I have missed in the ECU or the timing marks are wrong and the CAS is all off. Hence I need to verify if my marks are I the ball park or 20degrees off! Johns idea seems sound to me certainly will tell me within a small margin.
When you say about marling tdc on flywheel is better how come? Is it because this is usually located on a dowel so more accurate? I presume you make a pointer marker on the rear iron some where to align too?
To be fair I would be surprised if you got half a degree of play in the front pulley bolt holes?
Thanks again
Lee
Just another thought that might help me. O have seen images. Of the different pullies and hubs. But can someone confirm roughly where the bolts are pointing on a 20b hub when the leadin marking is aligned? Around 15degrees off horizontal? Angled down or up? Conversely if you took the 20b hub and off a swapped it for FC or FD which I think have the same bolt pattern and then fitted the 20b pulley back and aligned the leading mark again where do the bolts point now. This might give me a quick answer as to whether the motor has an FC hub on instead of the 20b one. Then I have another gauge I can work with. As I recall doing that puts the marks out around 15degrees. Just not sure if that shows as advanced or not.
I'm willing to bet that the pulley marks are 20 degrees off, instead of your CAS at this point. The 20B CAS and 13B ones are the same, as far as I have been led to believe. It would not surprise me if the hub is not matched, or if the pulleys were swapped around at some point by the previous owner.
In any event, the CAS installation is the same as a 13B so it should be fine. You have not mentioned what engine controller you are using, but what you can do is set the timing lock to a know value of, say 0 or stock -5 degrees. Mark the pulley there and you might have to make a new pointer, or just set your trigger offset differently in your engine controller.
If your global trigger offset is incorrect, this is why your timing light is not lining up correctly.
As far as marking the flywheel, the engine is stacked back to front. As you set the first rotor down, you just mark the flywheel in relation to any point of your choosing. Usually, the flywheel has no pulley bolt play in it, like the front does. If it does, the keyway is worn out. As you stack the engine, you rotate to TDC for that rotor. mark again and continue for however many rotors you have.
180 degrees out for a 2 rotor, 120 for 3 rotor, 90 for 4 rotor. This is just for physical marking of the flywheel and then if there are any issues on the front, you can refer to the back. I know that hubs and pulleys should always be a matched set, so if they get swapped all hell can break loose.
I have been thinking about this tonight. I could be being dumb but. If the timing marks are off as suspected. I have aligned my engine to TDC with these marks and then set the CAS to these marks as well. So would that not mean that if I timed the engine or should show correct even if it was wrong unless the CAS jumped a tooth which it hasn't as my pointers line up perfect on the corners of the CAS sensors. So essentially the engine should think that is correct TDC as the sensors is what triggers the coil to fire via the ECU. Correct. Even more reason to confirm my TDC is right anyway as I need to know my baseline is right. Does this point to ECU global correction or CAS at wrong polarity even though wired up as per the manual maybe? I am on a microtech by the way ltx-12.
If someone can answer with where the pulley bolts should be pointing at TDC that will give me something to go off.
Thanks
Lee
I have been thinking about this tonight. I could be being dumb but. If the timing marks are off as suspected. I have aligned my engine to TDC with these marks and then set the CAS to these marks as well. So would that not mean that if I timed the engine or should show correct even if it was wrong unless the CAS jumped a tooth which it hasn't as my pointers line up perfect on the corners of the CAS sensors. So essentially the engine should think that is correct TDC as the sensors is what triggers the coil to fire via the ECU. Correct. Even more reason to confirm my TDC is right anyway as I need to know my baseline is right. Does this point to ECU global correction or CAS at wrong polarity even though wired up as per the manual maybe? I am on a microtech by the way ltx-12.
I think you may have answered your question. In all reality, the ECU doesn't care where it's lined up as long as the trigger and offset are programmed correctly. You can have a car run off of any point. I have worked on V8 engines where the dizzy was stabbed in incorrectly. This was a buddy of mine and it was night time. He replaced his intake that night and just needed it to run so that he could get to his second job. So, I pulled the wires off the cap. Hopped them around until it ran. Then we timed it with the dizzy several teeth off. Sure the #1 plug wire was not on the #1 post, but it ran good enough for him to get to work. The next day I pulled the dizzy out and stabbed it in correctly. The engine doesn't care as long as it gets spark to the correct plug at the right time. Where it comes from is a different story.
The ECU is only firing the spark where it's told. It has no idea where the pulley marks are located. The CAS may be wired backwards, but you would have to check the MicroTech subforum for diagrams for that.
If someone can answer with where the pulley bolts should be pointing at TDC that will give me something to go off.
Thanks
Lee
I can't help you here, but hopefully someone else can.
Hi HSMIDY, that is with FC and FD hub right? The the 20b hub is around counterclockwise about 15degs from vertical. Will check mine later. I remember seeing some images that confused me that are on the other thread started by F1pilot. There is a picture showing a 20b pulley fixed on an eshaft. The keyway is rotated to 9 oclock. If you look at the timing marks these are counterclockwise from vertical 10degrees or so. Look at the front cover of a 20b. The timing pointer is around 10degrees clockwise of vertical. So if TDC is 9 o'clock for the keyway. How on earth van the timing marks line up to the pointer? I will try and repost the pic.
Well that is interesting.. Look where your keyway is compared to the picture above. Spot the difference? So that would imply you had and FC or FD 13b hub if all the other info I have flubd is correct. Which is what I suspect I might have. So if you align you leading timing marking with the pointer on the cover your bolts are clockwise of vertical? I will swap back my 20b pulley later and post a pic buy best I can see looking now is bolts maybe slightly counterclockwise of vertical a few degrees, if at all, with leading 1 lined up. I would guess the pointer is set around 5 degrees clockwise from vertical for reference. So yes looking again at the marks in relation to the pulley bolts it could set your keyway at 90 degrees.
This is the post I am referring to. Note the bolt pattern in relation to the keyway. Ignore the FD trigger wheel. Not the same as what you have shown. FD and FC look the same. Although it looms like maybe FC holes are off a degree or two. Maybe camera angle.
Originally Posted by Banzai-Racing
There is no difference in hub thickness, dimensionally the FC, 20B & FD are the same, FD just has alignment pins.
In addition Banzai posted this showing the 20b marks put on a FD trigger wheel mounted on a 20b hub. First thing I spotted is mine are not quite in the same place. Yet have been copied exactly from my 20b pulley.
Originally Posted by Banzai-Racing
Here you go, also included the stock FD timing wheel with the 20B timing marks
Okay.. Thanks for the picture.. Interesting. Looks like it would line up pretty well on TDC. However, unless there are two versions of 20b hub-pulley setup that should not work?!
I am looking again.. All three hubs have a slightly different keyway position don't they. FD is in line with bolts holes. FC is around about 5 degrees or so and 20B is around about 10-15 degrees by the look of it. These hubs and pulley configurations are a mine field when you consider most people probably don't even realise they are different!
So HSMIDY you must have an FD hub your engine then?
08-04-16, 04:40 PM
