Jeff20B

iTrader: (13)

I'm going to use an FB front cover on a 20B. I test fitted it yesterday and it seems to fit the 20B like it was designed to. There's just a slight possiblilty that I'll need to trim it where a front tension bolt head looks like it's in the way. The front cover seems to stand off of the engine a little, but there is still some old gasket material on the engine mounting surface. I'll know more after it's been scraped clean.

The timing pins on both front covers are so close that I'll call them even. The only difference is their distance from the pulley. Since the 20B pulley is larger in diameter, the 20B front cover's pin is further away from the E shaft. The FB cover's pin is actually under the 20B pulley, so I can still line it up.

Here's a question for all you 20B people out there. Is a 20B normally advanced by 5 or 6 degrees compared to a 13B at the same RPM?

I have an FC pulley that will work with my FB front cover. With the E shaft right at 0º (the L mark) on the 20B pulley, I swapped the FC pulley in and its L mark is 5 or 6mm (degrees, heheh) to the left (towards the intake/exhaust side of the engine). To get the FC L mark to line up to the pin, I'd have to crank the E shaft clockwise a little.

To keep it simple, I'll assume that the difference is 5º between the two pullies. Since the 20B is a turbo engine, and my FC pulley came from an NA engine, could this be the reason for the 5º offset? Also, I need to mark my pulley every 120º. Should I use the FC's L mark as a starting point? Or should I go 5mm advanced to keep it all 20Bish and go from there? It's only 5º. Hmm.

rotaspec

I might be missing something, but why do you need to mark the pulley every 120 degrees?

Jeff20B

iTrader: (13)

Oops, I forgot to mention I've got an FB dizzy with pickups space every 120º, so I need the pulley to match so I'll know if it's accurately timed on each rotor.

Anyone know if I should use the FC pulley's L mark as is, or should I go advanced by 5º like the 20B's pulley?

Looking in through the L plug hole on rotor #1, it looks like the FC pulley's timing mark is really good. But then when I crank it to the T mark and look through the T hole, it's like right at the edge of the 'bathtub'. A little advance would be better I think. Hmm, maybe if I did advance by 5º it would be better? Then again, when it's running, it's advanced a little anyway. More so at higher RPM.

rotaspec

So are you making your own version of Racing Beats (Campbells Soup Can) distributor, or just using the pickups to trigger an ecu?
The stock FB electronic dizzy has 4 lobes on the wheel, giving 90degrees, times two for the half speed rotation, giving 180 degrees. I was thinking of trying to find a V6 dizzy that I can adapt for experimentation. It's scary stuff though, don't want to detonate a nice 20B

Gary

Jeff20B

iTrader: (13)

Nah, it's something I've been working on that I've decided to call TLIDFIS (triple leading ignitor direct fire ignition system). It will also employ 0º and 180º sparks which no other 20B has ever had before; unless someone beats me to it.

Here is a pic

No7Yet

Seriously... why? Why not just go with a crank trigger setup and a standalone? It's nifty and all, but it just seems like a lot of work to end up with something suboptimal.

Brandon
BR7 Racing

Jeff20B

iTrader: (13)

Sorry about the quality.

Jeff20B

iTrader: (13)

Again, because nobody has ever done it before. I'm happy enough with DLIDFIS on my other rotary vehicles.

RETed

Wow, that's crazy looking!

BTW, the FC stock pulleys are marked 5ATDC and 15 ATDC - there's a 10-degree split between leading and trailing.

The Cosmo ignition maps should be pretty close to what the RX-7 ones are like.&nbsp If anything, the Cosmo igniton maps are slightly aggressive (about 3-5 degree more advanced than the rest of the map) at around 3kRPM, which is probably for cruising ranges.



-Ted

setzep

So what does a stock 13B-RE or 20B pulley read? The same as the FC?

Jeff20B

iTrader: (13)

I wish I had a better camera. I've got another pic from the side on this next roll of film, but it may be far away-looking. That's the best I can do untill I forcebly aquire the use of a digital camera (lol we'll see).

Ted, sorry for the all the questions coming up, but my FC pulley has a yellow mark at ?? degrees and a red mark at 15 degrees after the yellow mark, which gives it 15 degrees of split. This is measured as 15mm with a cloth tape measure. Is this an accurate measurement method?

Did you mean 5 BTDC? If not, are you saying that the 20B pulley's L mark is actually at 0 degrees? It is advanced 5 degrees compared to the FC pulley. Is my pulley unique or somthing? Or are they all like that?

I'd rather start from a mark at 0 degrees, if I could.

My FB pulley is 10ATDC compared to the 20B pulley mounting bolts (yes I know one of the bolt holes is offset, and they could have changed things a little over the years) and has a split of 20 degrees. I assume this is because 12As have a longer compression area in the rotor and a lower plug location in the housing.

setzep, I'll do a side by side comparison of the pulleys as soon as my oil pan is done.

setzep

I guess I just assumed that the yellow was 5ATDC and the red was 20ATDC on my 13B cosmo pulley. But if it isn't I need to know so I don't find out the hard way!

Jeff20B

iTrader: (13)

You and me both.

setzep

SOB, think if we put a pencil in the trailing plug hole and a pencil in the leading hole then turned enging over by hand till they were both even we could find TDC that way? Or better yet use a couple dial indicators?? I'd really like to make sure I have my timing zeored in right.

Jeff20B

iTrader: (13)

Yes that could work. I'm lucky to have my engine on a stand and can look through rotor #1's plugs holes at least. #2 is covered by the engine stand hardware and #3 is visible.

I think a WD40 can spray tube (the red straw) inserted into the T hole would work pretty well (for me at least) and a pencil in the L hole.

So what I'm trying to do is to center the rotor compression dish between the plug holes? I can do that.

Is that really the way you're supposed to find TDC?

Heh, a dial indicator would be too accurate with all the carbon buildup all over the rotors. I'm just looking for a happy average that hopefully matches one of my pullies.

Jeff20B

iTrader: (13)

I think I figured out what I was wondering about the pulley 5º offset between FC and 20B. Apearantly, there were differences between pulley hubs throughout the years. This means that it's just a happy coincidence that my FC pulley just so happens to be only 5º away from the 20B pulley when aligned on the 20B hub. I read about it here: http://www.nopistons.com/forums/inde...post&id=268861

I'm glad I stopped myself after seeing how the edge of the compression dish was at the T hole when the FC's red T mark was lined up with the pin. The E shaft was a little too far clockwise at that point. Whew.

Yep, I guess all I need to do is try the pencil test and compare the results to my pullies (what's a little graphite with all that carbon in there?). I'm already leaning toward the 20B pulley's L mark as the correct one to use. I'll then transfer the mark over to my FC pulley and measure 120º both directions and average them to create three equal slices on a pie graph.

setzep, I'll let you know how many degrees the 20B's LT split is. I think it's supposed to be 15º, and I think the 13BRE is the same, but I'll let you know my readings.

rotaspec

According to the emissions plate in the Cosmo's engine bay, the timing is 5deg and 20deg ATDC. They actually write it as -5deg and -20deg BTDC.

Gary

Jeff20B

iTrader: (13)

Thanks for the info. It will come in very handy to find 0BTDC or 0ATDC or whatever they call it.

setzep

ahh... so the cosmo has the same timing as the T2 then. Good, I guess my timing is zeroed in then Thanks for the info guys!

Jeff20B

iTrader: (13)

setzep, are you using the stock pulley?

setzep

sure am

setzep

oh wait, stock pulley but FB front cover.... Think the marker on the front cover is in the same place as the cosmo one?

Jeff20B

iTrader: (13)

It's in the same place degree-wise, but it's further away from the E shaft.

My FB front cover's pin is below the 20B's pulley. I can still align it; it's just under the pulley instead of over it.

Is your pulley large like a 20B? Or 360mm circumference like an FB/FC?

setzep

it's large, looks to be about 400mm circumfrence. Probably the same as the 20B I'd guess.

Jeff20B

iTrader: (13)

It probably is the same because it came out of the same car. I'll measure mine pretty soon and let you know.