2slow4stock

iTrader: (18)

Ok, so I've noticed that ignition timing is -5 leading and -20 for trailing. Does that mean when I do set timing, I should have a gun that does - values?

I was trying to manually retard the ignition timing *3 back, because I don't have a tuning software yet. I am hitting +10psi, with no fuel cuts. But I don't want to be to advanced in the high rpms. (Which I think I am)

I am not detonating, but I do every now and then get a hick up at high rpms. It's most likely too much fuel, but I cannot correct it until I can retard the timing a bit and use the safc to turn fuel just a tad bit down.

So my question is, when I set timing. Do I 0 out the crank pulley to the leading mark, or use a gun with - marks. I know I have read that I'm suppose to use a 2 cycle timing light, but also searched that most guns now have both functions in them already.

ifryrice

With your gun reading 0* stock it'll fire at the -5 mark. Then you just adjust your timing gun the 3 degrees and line up the mark again and you'll be where you want to be.

2slow4stock

iTrader: (18)

But here's the thing, If I have it at 3* would that not make my timing, advanced? I thought about also, that since it's not -5 on my gun, but +5 I would be setting my timing +10* positive would I not?

I am trying to manually get the timing retarded and set all the way up the rpm to be safe. I believe what i did was advanced my ignition then retarded it. But I just want to verify, that *0 for leading would be fine.

Does anyone know where I could find a gun that does - degrees?

Thanks, Bud.

ifryrice

My bad, I kind of had a brain fart on that. The timing light is triggered from the spark pulse, to set advance it simply adds delay to when it fires so that you can locate your original timing mark X degrees behind where it's currently firing. To set retard, it would have to fire ahead of the actual spark pulse to properly flash on the existing marks. I'm pretty sure the only way you can accurately do this now that I think it out would be to measure and add a new timing mark. You could measure the distance between leading & trailings mark, divide by 5 (will give you the distance between each 3 degrees) then move behind the leading mark that distance and add a new mark, then line it up with that with your gun set at 0.

2slow4stock

iTrader: (18)

Actually... I'll re-stab the cas, to get -5*. I believe me moving it to 0* Actually advanced it. But I don't feel like doing the timing marks any time soon. I was thinking of having -8* idle ignition timing for the leadings. Or I just take off the manual boost controller and buy the stock boost controller.

jjwalker

One question I have is, why does the rotary fire ATDC anyway?

Next question. With the stock timing map, what is the highest degree of advance the ECU will go to BTDC?

Sorry for the thread jack, didn't want to post two silly questions in thier own thread.

2slow4stock

iTrader: (18)

Actually it's -5* BTDC for idle, not at directly ATDC.

And from what I've seen probably *28 advanced. I believe, but someone chime in. It's not really a thread jack, since it still has to do with the ignition.

jjwalker

I looked at the FSM yesterday and it has " 5* ATDC Leading " bolded. Trailing is " 20* ATDC " and is also bolded. Is this a typo?

HAILERS

-5 Lead and -20 Trail at idle with no a/c on and the pwr steering not being used. Hot engine also.

No set figure for when it advances when the rpms are over 1200rpm. Depends on load and Stuff on how much advance over 1200rpm.

j9fd3s

iTrader: (3)

BTDC stands for BEFORE Top Dead Center

TDC = Top Dead Center

ATDC = AFTER Top Dead Center.

so -5 degrees BEFORE TDC is THE SAME as 5 degrees AFTER TDC.

maximum the system CAN advance to is 48 degrees BTDC, you'd find that at really high rpm decel

2slow4stock

iTrader: (18)

Ahh, I think I understand now. Anything under 1200rpm, I can mess with it, but going to leave it stock at 5* for idle around 950rpm.

So from what I understand, anything under 1200rpm is a fixed timing correct? So even if you manually retard the ignition a few degrees back it won't retard those *'s in the high rpm?

Which one is it,

Will it be -5* for timing, or is it 5* at idle. I am just confused about the (-) part of the timing table.

ifryrice

It depends on what value you're reading. It has to have BTDC or ATDC to know.

When setting timing, you set it at 5ATDC (also known as -5BTDC). If you retard it any from the CAS, it'll retard the entire timing table by that value. The ECU advances only from the position that the CAS is set.

arghx

iTrader: (3)

When I rebuilt my motor I purchased a brand new crank pulley and hub set from Mazda:



That's not zoomed in, but it gives you an idea of what the new ones look like. Right now the pointer is lined up to the YELLOW mark. The yellow mark isn't pictured here (it is machined into the rim of the pulley and painted yellow), but it is opposite the green paint there. That green paint is factory. The yellow mark is the leading mark and is at -5 BTDC (5 ATDC). You are supposed to have this mark lined up when you stab the CAS. The yellow paint on this thing sucks. Mine started flaking away just after I pulled it out the Mazda packaging.

To the left of the yellow mark is the RED mark. This is at -20 BTDC (20 ATDC) and is the trailing mark. It is opposite the factory white paint mark. When you are setting the timing you line up the yellow mark to the pointer with the engine running. If you rotate the CAS so that the pointer is to the left of the yellow mark, you are retarding the timing and eventually idle quality will suffer etc. If you wanted to retard by 3 degrees, with the engine running line up the yellow mark using the timing light. It is the mark on the right. Then rotate the CAS halfway between the yellow and red marks, that would retard it about 7 degrees. Half the distance from that mid point back to the yellow mark is around 3 degrees, or 1/4 of the way from the yellow mark to the red.

I don't know where this pic is from (Hailers?), but it shows the typical dilapidated Rx-7 crank pulley lined up on what was once the yellow mark. It is that small indentation there opposite the pointer:



You are moving from the right mark (yellow) towards the left when you retard the timing.

2slow4stock

iTrader: (18)

Ohhh, ok. That makes perfect sense. I did retard the ignition timing then. Now I know I didn't do anything wrong, like advanced the timing. Thanks for all the information. I hope this helps someone else out.

I understand that the timing will be set all the way back, that is what I am hoping for. Since without a boost controller I am only seeing 4.5psi all the way to red line. (I could buy the stock ebc, but don't have funds right now) With boost controller it spikes to 14psi but lowers down to 10psi. I just want to be safe for now until I buy a standalone.

Also fuel mods are there so i'm safe in the fuel department.

KhanArtisT

iTrader: (2)

Yeah that was my problem with my MBC (ball/spring) on my old setup too, the boost curve really went to hell. It was impossible trying to set it to 5psi+ without hitting fuel cut on the initial boost spike. For some reason yours doesn't though?

You must be pulling a lot of fuel @5psi considering you're running the 680s, or are you? What are your WOT full boost AFR's with no SAFC correction?

I'm running off the wastegate too, about 5psi very low 10s on the wideband Stock ECU sucks! Its been a really reliable setup though, I've put 8,000 miles on it.

2slow4stock

iTrader: (18)

Well with 4.5psi I am rich as well with no power. If I was going to run without the mbc, I would have to put the 550cc injectors back in.

Even with spiking to 14psi and holding at 10psi, I am still in the 11.2 afr until 6849rpm anything after that is pig rich, 10-9afr. So the 680cc injectors do, do something. I think I will set the ignition timing at 0*, so I can take away from fuel from 6500rpm+.

I'm actually surprised how well the 680cc works in the secondary's, I know with 10psi before 4000rpm I lean out a little bit. But there's nothing I can do with the secondary's set at 3800rpm.

Weird, I don't have any fuel cut. But I do hit really rich spots. One thing I might have to say is, trying to get the afr were you want them to with nasty spikes are a bitch. I know the turbo is over working over 12psi.

I am not running 4.5psi since I will not take off the mbc again. (Wayyy too slow, and too much fuel.) But I would be in the 10's afr once 4300rpm comes around. (-.-)