rxspeed7

iTrader: (5)

Msd= multiple spark discharge.

Rub20B

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

Rub20B

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

j9fd3s

iTrader: (3)

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

ultimatejay

iTrader: (1)

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.

Rub20B

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?

Rub20B

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

peejay

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

j9fd3s

iTrader: (3)

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.

Rub20B

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

peejay

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.

j9fd3s

iTrader: (3)

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

Rub20B

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

peejay

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.

Rub20B

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

Rub20B

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






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

j9fd3s

iTrader: (3)

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

Rub20B

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

DriveFast7

iTrader: (1)

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?

Rub20B

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..

Rub20B

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)

j9fd3s

iTrader: (3)

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

Rub20B

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

j9fd3s

iTrader: (3)

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

speedturn

iTrader: (1)

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.