13B PP Ignition breakup - RX7Club.com - Mazda RX7 Forum

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13B PP Ignition breakup

Old 06-06-12, 06:13 AM
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13B PP Ignition breakup

Hello,

I recently bought a RX3, it has a 13B PP engine built in the UK. Don't know too much about it, but the rotor housings are RX4, with straight inlets (unlike the angles like found on the RB ones)

Its carbed, running a 48 IDA and according to the previous owner 50mm chokes. Carbin is quite good, runnign about 12.5-13 afrs at WOT and idling around 14:1 at 2500 rpm

Now the strory.

The car came with BR7 and BR9 (ET I think) plugs, which according to the owner where only to start it and get it to operating temp. after that he would swap in B10 and B11EGV's (2 stroke plugs) for trackdriving.

the startup plugs where gapped at around 1.1mm
the B10/11EGV around .65mm

now I took the car for a spin with the BR7/9, and it was almost undriveable because of misfire (huge flames from the rear). gapped them to around .7mm, which slightly improved things, but not much.

then I took some new BR8ET's (both for L and T), stock gapping of around 1mm, car drives like a dream and pulls very strong until about 7500rpm, after that it ignition starts breaking up

My idea was that it was because of the gapping, so with the engine nice and warm I popped in the B10/11EGV's, started fine but till I was at the end of the driveway the plugs where already fouled and it would barely drive, and make huge fireballs.

Ign setup is a later 12A dizzy (igniters on the dizzy itself) with locked timing, around 16 deg leading and around 10 deg of split, distributor cap and ign leada appear new

Do you guys have any idea how to improve things with this ignition setup? I would be nice if would work well till about 9500rpm without breaking up. if its not possible I might go EFI, but because the car is 40 years old, keeping it carbed and oldskool would be preferred
Attached Thumbnails 13B PP Ignition breakup-2998.jpg  
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Old 06-06-12, 12:20 PM
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that looks a lot like mine!

i recently scanned the Rx3 sports kit manuals, and that's a bridgeport, but they tell you to warm it up with stock plugs and then switch to the racing ones.... https://docs.google.com/file/d/0Byot...dXM/edit?pli=1 lots of chassis prep in there too....

anyways on my P port, i have no ignition breakup, and here is what i'm running....

same weber 48IDA, i spent a lot of time setting it up. idle is @900rpm, about 14:1afr. if yours is idling @2500, its maybe using the main circuit on the carb, and not the idle/transition circuit... cruise up to about 2500rpm is about 14.2-14.6, and then once you're on it, it drops into the 11's (i'm between jets, so i left it too rich instead of too lean).

the car drives actually pretty close to a normal car, you'll find the PP is picky, but once you give it the fuel it wants, its pretty tame. too lean, and it won't run, too rich and it'll be the fire spitting beast everyone on the internet thinks it is.

ignition is an 81-85 distributor, timing is locked. i have an MSD firing both coils at once, thru the cap, i'm running Rx8 leading plugs, which i like, and normal FD trailings. next step is to go to the race plugs for the trailing's at least.

currently timing is 18BTDC, although the engine wants less timing under 2500rpm, so someday it'll get a timing curve.

that should give you a bunch of stuff to look at!
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Old 06-06-12, 12:50 PM
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Get rid of the stock ignition and go with a wasted spark ignition like j9fd3s is doing using either
an MSD like he does or some other setup that can charge the coils quickly to support your
9500 rpm goal.
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Old 06-06-12, 06:17 PM
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oh actually you should check the voltage at the coils, the points cars see like 9v, 12V is much better, or you can wire em up to the alternator, and get 14v

so i think you should be able to get by on a stock ignition system, with race plugs (takes less power to fire them), and 12V or better at the coils. the carb will have to be spot on, and since the stock ignition power is dropping (coil charge time vs actual time) over 6k, it'll want to be lean

i'm running 1 stock ignitor to the MSD to both coils thru the cap. peejay has run the same setup for years, and it works for both of us.
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Old 06-06-12, 06:23 PM
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Very nice info, I also like the Scanned RX3 sports package document!

About the plugs, you say using the RX8 plugs in the leading, so this means the 7 heat rating which are the stock rx8 leading, or the colder 9 rx8 trailing plugs?, also for the trailing you say using FD ones, but the FD also used 7 for the L and 9 for the T..

The previous owner was using 10 and 11's for track use, so I would then lean to opt for 4x rx8 trailing ones (9 heat rating), which seem then to be the best compromise between fouling restance and low heat rating

would it be dangerous to run the car WOT with relatively hot plugs (8's)? would it cause detonation or just accelerated plug deterioration?

So what I will do is using twin coils (or single dual output coil) for the leading in a wasted spark arrangement, fed by and msd or equivalent, and then using the dizzy with stock coil and igniter solely for the trailing.. does that sound like a plan or what
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Old 06-06-12, 08:15 PM
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MSD 6AL odered wehn it arrived I will first see what it does with some old RX8 plugs (where still going well on the miata track car, but where changed to be on the sure side)
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Old 06-07-12, 10:57 AM
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Originally Posted by Rub20B View Post
Very nice info, I also like the Scanned RX3 sports package document!

About the plugs, you say using the RX8 plugs in the leading, so this means the 7 heat rating which are the stock rx8 leading, or the colder 9 rx8 trailing plugs?, also for the trailing you say using FD ones, but the FD also used 7 for the L and 9 for the T..

The previous owner was using 10 and 11's for track use, so I would then lean to opt for 4x rx8 trailing ones (9 heat rating), which seem then to be the best compromise between fouling restance and low heat rating

would it be dangerous to run the car WOT with relatively hot plugs (8's)? would it cause detonation or just accelerated plug deterioration?

So what I will do is using twin coils (or single dual output coil) for the leading in a wasted spark arrangement, fed by and msd or equivalent, and then using the dizzy with stock coil and igniter solely for the trailing.. does that sound like a plan or what
oh lol, i'm running Rx8 7's in the leading and FD 9's in the trailing, and this seems ok, but i'm running it rich and there is probably 50hp in an airbox, exhaust and dyno tune... on the track you should probably stick with 10's

i'd skip the wastespark. the wastespark systems fire the coil the same amount of times per revolution as the stock system, so you still have the same; not enough charge time at high rpm problem.

i'd just put the MSD on, and work on the carb. you should be able to idle it @700rpm, and it should just pull cleanly from idle all the way up
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Old 06-07-12, 04:15 PM
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A while back I worked on something similar but I was using 2 FC coild to Direct Fire the plugs, driven by a 6AL. What I did was modify the magnetic pickups inside the dizzy so that one was 1/2" higher than the other. I ground off 2 opposite points on one reluctor and the 2 opposite ones from the other. I set a 1/4" distance between reluctors and pinned it in place.

The point of it was that 1 coil fired rotor 1 and the other rotor 2. This gave spark at all 4 points and gave the coils time to recharge.

Clean reving all the way past 11K. Spacing is very important because if not it will crossfire due to magnetic interference.
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Old 06-07-12, 06:28 PM
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Originally Posted by j9fd3s View Post
anyways on my P port, i have no ignition breakup, and here is what i'm running....

same weber 48IDA, i spent a lot of time setting it up. idle is @900rpm, about 14:1afr. if yours is idling @2500, its maybe using the main circuit on the carb, and not the idle/transition circuit... cruise up to about 2500rpm is about 14.2-14.6, and then once you're on it, it drops into the 11's (i'm between jets, so i left it too rich instead of too lean).

the car drives actually pretty close to a normal car, you'll find the PP is picky, but once you give it the fuel it wants, its pretty tame. too lean, and it won't run, too rich and it'll be the fire spitting beast everyone on the internet thinks it is.

ignition is an 81-85 distributor, timing is locked!
I have no ignition breakup eaither, Mine uses :
81-85 dizzy, timing locked 18* 10split
Bosch hec716 coil's
Eagle 9mm leads
B7ES an B8ES spark plugs.

Havn't taken my p-port over 6800rpm yet, But run's good up to there, Very smooth too, Had same ignition set up on my HBP and no issues with that to.

My pp idle's at 2000rpm around 14+ afr's. Injected MT4 fuel only ecu.
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Old 06-07-12, 06:54 PM
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Run leading through waste spark thru MSD 6al and trailing through distrubutor.
Take the distributor cap off and look inside and make sure the rotor is not touching the cap contacts. What happens is at high rpm and also shaft bearing wear in the distributor the shaft will walk a little and the rotor will contact the cap causing missfires. I have seen it in my car but it was only on the trailing because I had my car set up for waste spark on leading. So check the cap for any marks or grooves first.

Here's a link for the ignition set up. I highly recommend it.
http://www.smbaker.com/sand-rail/maz...-rotary-engine
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Old 06-07-12, 11:57 PM
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I drive two coils with one MSD. I used to drive just two standard type coils, until one caught on fire, then I went to an FC leading coil in the leading, and a single FC trailing coil on the trailing, going through the distributor, obviously. It's stacked onto the leading coil.

The weird thing is, the engine runs like crap if the trailing doesn't work, but it runs just fine if the leading doesn't work.
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Old 06-08-12, 03:44 AM
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Originally Posted by ArmyOfOne View Post
A while back I worked on something similar but I was using 2 FC coild to Direct Fire the plugs, driven by a 6AL. What I did was modify the magnetic pickups inside the dizzy so that one was 1/2" higher than the other. I ground off 2 opposite points on one reluctor and the 2 opposite ones from the other. I set a 1/4" distance between reluctors and pinned it in place.

The point of it was that 1 coil fired rotor 1 and the other rotor 2. This gave spark at all 4 points and gave the coils time to recharge.

Clean reving all the way past 11K. Spacing is very important because if not it will crossfire due to magnetic interference.
Do I see it right when doing things this way, there should be also 2 6AL's and there is no possibilty for split as you use the trailing magn pickup for one rotor and the leading pickup for the other one?

10k rpm, means 20k ignition events (in wasted spark mode), comes to about 3 ms in between the events, does that sound like time enough to charge the coil well? on the renesis I am using this ls2 truck coils in direct fire, and IIRC the have around 5ms dwelltime
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Old 06-08-12, 12:46 PM
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Yup, that is correct, 2 6AL and no split.

With this setup at 10K each coil is responsible for half the events so no issues there.

I think it would work but spark may start getting weak on top end.
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Old 06-08-12, 06:02 PM
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Ok, I see..

I called the guy who built the engine he says 10 deg split works the best, but personally I have no idea, but if the car makes it to a dyno I would offcourse find it a good thing to see what influence the split has. He said it would be ok to run about 26 deg static (leading) timing

Do the 12A/13B dizzy fit in a 10A front cover? that would really be the easy way out to run 4 pickups to control each coil with single spark event per cycle
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Old 06-09-12, 01:35 AM
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I remember we made 225 RWHP at around 30' no split on a 13B 6 port full bridgeport. On a Holley 600 with taht setup.
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Old 06-09-12, 05:50 PM
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Originally Posted by ArmyOfOne View Post
I remember we made 225 RWHP at around 30' no split on a 13B 6 port full bridgeport. On a Holley 600 with taht setup.
Nice numbers.. I will be happy if I get this PP running both smooth and strong and still making 220 at the wheels

Here are some pics of a gearbox I got as a spare with the car, the owner said it was a mazdaspeed 5 speed. first is where second is on a normal gearbox and reverse is where first is. he also said it had a long 1st and 2nd and then the rest relatively close ratio. I looked a bit on the net but not much info is available.

Casting also looks different than the box in the rx3 sports kit manual
Attached Thumbnails 13B PP Ignition breakup-08062012784.jpg   13B PP Ignition breakup-08062012785.jpg   13B PP Ignition breakup-08062012786.jpg  
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Old 06-10-12, 01:25 PM
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i wonder if that is the SA22 competition gearbox?
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Old 07-10-12, 03:37 AM
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Originally Posted by ultimatejay View Post
Run leading through waste spark thru MSD 6al and trailing through distrubutor.
Take the distributor cap off and look inside and make sure the rotor is not touching the cap contacts. What happens is at high rpm and also shaft bearing wear in the distributor the shaft will walk a little and the rotor will contact the cap causing missfires. I have seen it in my car but it was only on the trailing because I had my car set up for waste spark on leading. So check the cap for any marks or grooves first.

Here's a link for the ignition set up. I highly recommend it.
MSD 6A direct fire Ignition for Mazda RX-7 Rotary Engine - Dr. Scott M. Baker
After looking more closely to the cap I see indeed evidence from the rotor grinding the contacts in the cap. Will need to find a better dizzy. What also was strange was that the front igniter was connected to the trailing coil..

I checked it 5 times and still I am also confident that when I was checking the timing the trailing fired around 10 deg after the leading. nonetheless I now used the front VR sensor to trigger the 6A and the trailing is kept stock.

Here are 2 photos of the install. 2nd picture is a lockable 10 turn 5K Ohm potmeters wired in series with the 5000 rpm MSD resistor to adjust the rev limiter, now the question is how well this will work as the trailing will still be firing
Attached Thumbnails 13B PP Ignition breakup-09072012812.jpg   13B PP Ignition breakup-09072012813.jpg  
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Old 07-10-12, 09:32 AM
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Originally Posted by j9fd3s View Post
i wonder if that is the SA22 competition gearbox?

I used to run 1st gen 13b NA trans in my FC.

Swap the tail end of the trans from your FC trans onto the 1st gen transmission and you get shorter 1st, 2nd, 3rd. its only about 1/10th shorter than the FC NA trans but it did help with the low power the car produced.
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Old 07-10-12, 12:36 PM
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here are the links to the Rx3 competition books

1977, early style PP https://docs.google.com/file/d/0Byot...NoT0xlaTQ/edit

70-73, bridgeport, but i think the chassis prep is the same https://docs.google.com/file/d/0Byot...ZLLU5qdXM/edit

comp parts list https://docs.google.com/file/d/0Byot...FVTTI5R2M/edit

and price list, c1978 https://docs.google.com/file/d/0Byot...UzR2hIZkE/edit
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Old 07-11-12, 05:34 AM
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Originally Posted by j9fd3s View Post
here are the links to the Rx3 competition books

1977, early style PP https://docs.google.com/file/d/0Byot...NoT0xlaTQ/edit

70-73, bridgeport, but i think the chassis prep is the same https://docs.google.com/file/d/0Byot...ZLLU5qdXM/edit

comp parts list https://docs.google.com/file/d/0Byot...FVTTI5R2M/edit

and price list, c1978 https://docs.google.com/file/d/0Byot...UzR2hIZkE/edit
Box looks way different as in the comp parts list..

Still didn't drive the car with the new ignition setup due to the rain, maybe tonight =)
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Old 07-11-12, 12:59 PM
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Originally Posted by Rub20B View Post
Box looks way different as in the comp parts list..

Still didn't drive the car with the new ignition setup due to the rain, maybe tonight =)
there is an Rx3 trans and an SA trans, i think you have the SA version.
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Old 07-12-12, 04:27 AM
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Originally Posted by Rub20B View Post
Nice numbers.. I will be happy if I get this PP running both smooth and strong and still making 220 at the wheels

Here are some pics of a gearbox I got as a spare with the car, the owner said it was a mazdaspeed 5 speed. first is where second is on a normal gearbox and reverse is where first is. he also said it had a long 1st and 2nd and then the rest relatively close ratio. I looked a bit on the net but not much info is available.

Casting also looks different than the box in the rx3 sports kit manual
This is a Mazda competition 5speed close ratio gearbox.
It's correct that 1st gear is down to the left were you normaly finds the 2nd gear and revers were the 1st gear should be
I had 4 or 5 of this and all of them had 1:1 at fifth gear.
A normal problem with this gearboxes is bad syncro rings so open it and look how they are before you run it.
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Old 07-13-12, 08:29 AM
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Ok, thanks for the info, atm there is some striaght cut tremec box in the car, does the trick. but maybe in the future the box gets a nice home an 1st gen or street rx3

Still didnt test the car yet, stuped rain, and now the weather is good but time has to be invested in other business.. :fail:
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Old 07-16-12, 10:08 AM
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Got it running, idles fine, didn't drive it due to a fuel leak and rain.

Now I read that the MSD does multiple sparks at low rpm, could it be that this confuses my timing light? when I use the light and give it a rev it seems to get confused and flashes somwhere on the pulley where there are no marks at all
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