Ckforker

I haven't checked my timing in quite a while. I was able to get the leading right on the money, but for the life of me, can't get trailing. I can get it close, but that's with the dashpot moved all the way out.

Do those go bad, or am I missing something? It runs great, cleaned up some of the exhaust, but just can't get the light to match up. I followed the manual and also an old thread on this site.
Thanks

JOE68

redrop the dizzy .... when u do this make sure to take the cap off so it go's where u want it to go...you might need to do this a couple of times until u get it where u want

j9fd3s

iTrader: (3)

couple things to check, if the engine is built right, the timing will be correct with the distributor just off center of its slot. when you put these things together, if the distributor gear on the E shaft is backwards, the distributor will end up in a different spot, this is fine, you just can't eyeball it.

two, the advances do go bad, there is a rubber diaphragm in there.

third you also should be checking with the engine at idle, and with the vacuum advances not hooked up

fourth, if you mix and match too much stuff its possible to have not enough or too much of something. the various years had different timings and advances, its all small differences, but if you mix stuff...

Ckforker

Thanks, the engine is original, never opened up, distributor never removed. PO had zero knowledge and always took it to the dealership.

I followed all the procedures, so I'll try and find a new dashpot to check. It can retard the timing, just won't advance to get it to spec.

Ckforker

Tried with a different dizzy and timing light, still can't get it exactly on trailing. The good news is that it runs great and much better fumes. I'm not gonna mess with it anymore, with my luck I'll make it worse!

I accomplished the main goal of less fumes at idle by slightly advancing the leading timing and tweaking the carb.

Thanks for the input as always!

hoang5659

iTrader: (14)

sorry I am also messing with my timing also. I am following this chart I found on Racing Beat's site. http://www.racingbeat.com/manuals/timingchart.pdf
I have a carbed SE and the recommendation is to run 6 degrees btc on the leading and 6 degrees atc on the trailing. how do you adjust the trailing? sorry for the ignorance, I have never messed with this before. also, am I suppose to do the timing with the vacuum lines connected? i read something above that says to disconnect the vacuum. there was a sticker under the hood that says to leave it connected when setting the timing. please advise...

j9fd3s

iTrader: (3)

ok, so the distributor has a bunch of stuff going on in it, so you set thus
1. Disconnect the vacuum advances, the stock setup turns them off at idle, but you may not be running the stock solenoid/ecu, so you should just disconnect.
2. set the leading timing. 6btdc is 11 degress of advance, you might want to try it halfway first and make sure its ok and then go all the way
3. to set the trailing timing, you adjust the vacuum advance dashpot. you loosen the two screws, and it slides.

make sense?

rxtasy3

iTrader: (2)

this will be very helpful to u. setting trailing timing can be found in the FSM.
Foxed.ca - Mazda RX-7 Manuals

yeti

iTrader: (1)

@j9fd3s Ok, I think I'm confused now. How is 6btdc 11 degrees advanced? I thought I understood this and maybe I do and I'm just being dumb. Post whatever pictures or learning tools you can.

In the RB chart I'm personally looking at 8 BTC / 12 ATC (Weber, streetport).

j9fd3s

iTrader: (3)

its confusing, for a GSL-SE the stock timing is 5 AFTER Top Dead Center Leading.
Racing beat is 8 BEFORE Top Dead Center Leading.

if you want to make that the same Mazda is -5 Before Top Dead Center and Racing Beat is 8 Before Top Dead Center, the difference is 14 degrees, this is a lot to advance the timing, i'd suggest doing it in stages to make sure its ok

make sense?

hoang5659

iTrader: (14)

sorry for the stupid questions... I need timing for dummies. so when you set the leading ignition timing with zero advance and you line it up to the yellow notch, is that 5 degrees BTDC? this is the first time messing with a timing gun. what I was doing was setting the advance to 6 on my gun and lining it up with the yellow notch on the crank pulley. is that the correct way to do it?

when I try to set the trailing, do you line it up with the other notch? I believe stock is 20 degrees ATDC. do some math and advance it 14 degrees to get to the 6 degrees recommended and just line it up with the notch? please advise... thanks for all the help. I've had this car for a long time but I have never messed with the timing.

yeti

iTrader: (1)

Yeah, that makes sense. I have read due to all the variations it's best/easiest to set it at 6k which is what? 23 btc total? What do you think about that? Hopefully I'm not further confusing anyone or stepping all over op's thread.

j9fd3s

iTrader: (3)

first off its best to set the gun to 0, it won't give you the right number on these cars.

Second, the Leading Notch is 5 degrees AFTER Top Dead Center, and the Trailing is 20 degrees AFTER Top Dead Center.

third, stock you just set it to the marks and you're done, since RB's spec is 6 degrees BEFORE Top Dead Center you want to advance the thing, engine rpm should come up.

sometimes its nice to spin the engine by hand (you can use the 23mm on the alternator), and watch the marks go by. TDC is right before the Leading mark hits the pointer

j9fd3s

iTrader: (3)

there are two advance mechanisms in the distributor and they operate independently. most distributors are like this. first is the mechanical advance. the theory is that since the speed of combustion is fixed (always takes the same amount of time), the faster the engine goes the sooner you need to fire the spark plug. basically the air/fuel burns at a constant speed, but the engine speeds up. so the engine wants more timing with RPM. mechanically there are two weights on springs, and the higher you rev it, the further they extend, and the more advance you get.

the second is the vacuum advance. at low loads the engine can use more timing than it can at wide open, so it uses engine vacuum to add some timing.

at 6000rpm the mechanical advance is maxed out, and well you're sort of bypassing all the advances which is fine, especially in a high performance car. you just need to be quick, 6000rpm will get hot

the example with that comes from John Wyers book. he was the guy who ran race teams for Aston Martin, Ford and Porsche, and he had a particular knack for winning at Le Mans. Anyways they had problems with the Ford engines blowing up, and eventually checked the timing at redline and found that everything flopped around so much that the timing was 11 degrees more than what they set. which of course blew the engines right up. https://en.wikipedia.org/wiki/John_Wyer

t_g_farrell

iTrader: (1)

I do my timing at about 4500 rpm which should be totally advanced and I set it to about 25 deg. leading and I make trailing about 10 less (15).

Jeff20B

iTrader: (13)

TG, I've been wondering about setting timing at 4500 for a while now and figured I'd ask you. What does that translate to at idle? Wouldn't it be easier to just set it at 0 degrees at idle for the best idle quality and not worry about 4500 RPM? I ask because there are different total timings depending on which model distributor you have. In your case I assume it is the 1980 with the J=105 ignitors? Or did you "upgrade" to an FB dizzy since then and the ford ignitors? It's been years.

And because it is somewhat relevant to this thread, I'm going to list the FB dizzies and their total advance (these advance numbers are listed "as far as I know")
81-82 N201 = about 20 degrees
83 only N231 = about 20 degrees
84-85 12A N249 = about 24 degrees
84-85 13B N304 = about 30 degrees (but it requires you to set static timing -5 degrees at idle so it adds up to about 24 at 4500)
RE-SI 13B N305 = maybe 30ish degrees but its curved slot is backwards so it ramps up differently but I assume it's in a kinda similar way to the N304 we got in the GSL-SE

Thoughts?

As for the 12A turbo dizzy, I dunno. It isn't really relevant to this thread. Just kind of interesting from an academic standpoint because it has a boost retard feature that the NA ones lack. But I don't know what its total advance is. It's from '83 but that doesn't mean it is similar to the N231.

t_g_farrell

iTrader: (1)

I'm using an 83 dizzy (I think) with HEI modules to drive the ignition. I feel I find a bit more power when I time it @4500rpm. Now it does affect the idle and I have to bump the idle up to around 850 to make it stable. I've had it timed to 27 before. I wish I had a dyno at home to measure changes with. I guess I could get a smart phone dyno app and use that now that I have a smart phone LOL.

Jeff20B

iTrader: (13)

TG, your idle might be better if you seek out an N249 dizzy. Just a guess. Might be worth experimenting.

Ckforker

I can't believe you finally have a smart phone, I thought you'd still be fighting that!

ebodyboy

My '84 SE, as new, came with 5 degrees after and 20 after. One of the performance places (either R.B., R.E. or Mazdatrix) suggested an overall advance of 7.5 degrees - - which of course would put the leading at +2.5 and the trailing at -12.5 ( so maintaining the 15 degree separation). I did this adjustment at approx. 15K. kilometers and car now at 86K. Yes, it was an improvement all around and still using 87 octane fuel and 'name-brand' 10w-40 oil. 99% stock. 32mpg (CDN). Never winter driven. Orig. brake pads! etc. etc.

ebodyboy

One year later - - not driving as still need sunroof panel but my '69 Valiant doing well as daily driver. . Oh, and the timing recommendation is from the HP books - How to Modify Your MAZDA RX7 - (1987 ed.) by Dave Emanuel and Jim Downing. Stay safe.