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

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!

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.

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.

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

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)

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

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.

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.

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

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.

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

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.

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

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

i wonder if that is the SA22 competition gearbox?

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

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.

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 =)

there is an Rx3 trans and an SA trans, i think you have the SA version.

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.

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:

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

Msd= multiple spark discharge.

hmmz, so how does one set timing with a crappy timing light?

Idling on trailing plug only, somehow the Leading ign wont work when the engine is running, with ign on it works perfect if I pass a screwdriver by the pickup or if I turn the dizzy by hand, put the dizzy in and start, no spark on the leading

that car is really cool, i would street it here!

this is mine, Mr. Peepers | Facebook

i wonder if the same guy both of our housings? they both have that weird round flange

Well it looks like you have the leading ran on waste spark and trailing through the cap. Make sure you wired your MSD correctly for this.

Yep, actually it worked fine in the beginning but now stopped working, so I suspect bad ground or power, the ign on signal is taken from the + connector of the trailing coil. I have the MSD wired with the purple and green wire directly to the VR pickup, so bypassing the sotck leading igniter, so the withe MSD wire is not used. then the leading coils are 2 stock coils connected in parrallel


your def idles better, once ign is fixed I'll see what can be done on the carb.. these housings seem to be rx4 13B housings they don't have a round flange, but like a rotor shape with radiussed corners.. do yours have the blue paint as background of the mazda letters?

Got it sorted!!!

FTW almost gave up after trying and checking everything.. in the end it were the stuped leading plug which crapped theirselves and had an internal shoftcut, measured only around 20 Ohm!!! replaced them with RX8 #9's and all problems went away, pulls strong with afrs of around 12.5 across the rpm range..

bad news: tacho (stack) died for unknown reason doesnt moce anymore and also doesnt go to zero when power is appllied, so I don know what rpm it was making, but from the sound pulls easy over 9k

You didn't connect the tach lead to one of the coils, did you?

mine are 74-75 Rx2/3 housings, round flange. i do have blue paint as a background, i did it, its electric blue mica from a 2007 Mazda 3, not that it matters that much.

nope didnt do that, its connected to the negative terminal of the trailing coil.. I did same mig welding to the dizzy, but grounded the dizzy itself so doubt that could the cause..

used a scope altough on the leading coils, chargeing voltage isnt much more than 12v, negative spike just when it sparks is much more.. does triple spark only till just above idle

If you have an MSD, the coils will get over 400 volts. That is why nothing but the MSD gets connected to it.

If you connect a tach to the coil with an MSD, you will wreck the tach, assuming that the engine even runs. I've seen somebody connect an electric choke to the coil positive with an MSD once and the car would not even start. A tach is less of a current drain (really?) but they usually don't like 400v voltage spikes to them.

since i'm running leading and trailing from the MSD (like PJ), i'm pretty sure the tach is running from the MSD's tach out. which works fine. i actually have trouble with the connector on the back of the cluster, it never works after the car's been on the trailer

when exactly should there be 400v? during the carching of the coil or? I used a scope on it and the signal looks like around 12v when charging but at the moment of discharge there is a quite big negative voltage

Are you using an MSD ignition box or just MSD coils?

What you are describing sounds like a standard ignition scope pattern.

Assuming that you don't still have 12v+ tied into the coil.

Nope, using MSD 6AL with stock coils, black and orange connected to the coils

In the end the cause where the plugs, somehow they had like 3 ohm or so, just shorting the energy from the coil.

Engine is running quite well now and last weekend it did is first race (histroic cars pre 76, only NA and parts from that era allowed), which went really well, we were 3rd in the clase (sub 2500cc class) and 7th overall.

here is are the pictures of the day, so one can see the rest of the field in this race series mettet4mei | Bravo Racing

http://www.bravoracing.be/wp-content...i/IMG_3722.JPG

http://www.bravoracing.be/wp-content...i/IMG_4316.JPG


after the 30 min race session, there was maybe 1 minute of driving towards the trailer and the car was shut off. somehow both leading plugs where wet. I then changed the 2 leading coils for a single FC leading coil, did some driving on the street and found the plugs to be at least dry. could it be they are too cold? (#9 rx8 trailings in all 4 holes)

overal the engine is really going well, but after 8500 rpm torque is dripping rapidely. probaly the cause if the longer than optimal intake length and maybe port timing is conservative.

I bought a second engine made out of rx8 rotors and RB housings which will need to make at least 300 hp at the flywheel, hopefully more so we can aim for the #1 in the class next season. thefastest cars in the race are opel kadett togehter with the 911 rsr. also in our class there is a ford escort. the kadett for sure has around 300hp as its a 2.5l CIH engine spinning 8k rpm, and the ford is probaly running a cosworth engine, also easily producing around 300hp. for the overal class there is a porsche 911 rsr, and then these muscle cars which are with over 500 bhp slightly behind in in term of lap times as compared to the kadett and the 911 rsr

awesome, i'd love to go do that with mine! a P port Rx3 should be really competitive with anything pre76...

it should be yep, but there is missing about 40-50hp, once we found those sleeping ponies I think we can easily compete with the top of the field

Great car! I think the 9 heat range is too hot for track use, with a peripheral port race only car you should run 11's after the car warms up. I warm up my 12a J Bridge on br8eq14. Fires up first time.
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I have an ignition question. Running a 6AL wired wasted spark to MSD Blaster 2 coils, should I wire the coils in series or parallel?

I wired mine in parallel.. maybe you can try both and let me know what works best.. I ditched the dual coils and went for a FC leading coil.

I also have been told 9 should be warmest one should run, but after 30 min of track use the leading plugs where wet, and the trailing also dont look like they are too hot.. I then switched to the FC leading coil, after some WOT street driving I shut the engine down and coasted on the driveway, plugs still look cold but at least they were dry so I am a bit puzzled..

Damn, no edit possible..

what I still wanted to say, if you measure the resistance of the coils you can get and idea what will work best. I think for CDI ign, like the dynatek and probaly also the 6A, they write it will work best with low resistance (0.5 Ohm) coils. so if your coils measure 1 Ohm, and you put them in parallel, they will have 0.5Ohm. if yours already measure 0.5 Ohm, it will be 0.25 Ohm and this might be too low for the CDI (altough I am not sure if this really is an issue for the CDI)

the FC coil is pretty beefy! https://www.rx7club.com/haltech-foru...e-log-1019239/

yep, it has only 0.5 Ohm primary resistance, so basicly I am just using the coil with the MSD, I might try using the FC ignitor without MSD to see if that makes a difference

it might, the FC ignitor has a current limiter in it

I have been running PP road racing engines since 1997.

Do you have Mazda Factory Racing PP housings, or do you have street housings that have been made into racing PP housings?

For MFR PP housings, they are made for 20 Deg BTDC timing, both leading and trailing. These housings have the spark plugs located slightly differently than street roatary housings, so their timing requirements are slightly different.

For street housings that have been made into PP housings, I run leading 24 BTDC and trailing 18 BTDC.

I use an '81 - '83 stock distributor, and I dyno at 320 rwhp.

I warm up with 7 or 8 heat range NGKs, and then I use the 11.5 plugs for road racing. The 9 and 10 heat range plug will overheat the tip, which will cause detonation when running on straights longer than 3/8 mile. The hotter plugs will run okay for short bursts, but they engine will break up when running longer, sustained runs. For example, the 10 will run okay for one 1/4 mile pass, but if you turned around and ran 3 back to back 1/4 mile runs with no cool down in between, then the 10 heat range plugs will cause the engine to misfire. I fought this problem for awhile until an experience racer gave me a set of old 11.5 plugs, and that cured most tuning problems with my PP motor.

Also, your spark plug gap is much too wide. For a high rpm PP motor, you should be running 0.65mm gap.