dannobre

iTrader: (3)

There are many versions of the CZ..... the old board with the dip switches, a unit with same + external switch, the new board with 2resistors, 2 diodes and no jumpers, the first cap fix that added a 10K resistor, 2 caps and two diodes, and 2 jumpers, the GB32....caps and 6 diodes, The pictures of the mod to remove the caps are above in the thread.

Look at your board. It should look like the After Picture above

Rotary787

Wouldn't that be 150 Hz for each rotor instead of 9kHz? (Still above 50 Hz)

9000 rpm = 9000 crank_rev/min

freq = 9000 crank_rev/MIN * 1 rotor_rev/3 crank_rev * 3 ignitions / rotor rev * MIN/60 SEC
freq = 9000/60 ignitions/sec = 150 ignitions/sec
freq = 150 Hz

RX-8 friend

OK guys, time to get our facts straight. First, the 1N4148 is a silicon diode, and is a switching type, meaning it's ok for "high speed" use. High speed means anything over about 150 Hz and under about 200 kHz (for diodes, which usually are used for rectification of 50/60 Hz AC).

From Digikey for confirmation if needed:
1N4148MSTR-ND 1N4148 RECTIFIER SILICON .15A 75V DO-35 Micro Commercial Co. High Speed Switching 75V 150mA

Secondly, while the 1N4007 MAY work, it is a "slow" diode designed to rectify 60 Hz. I chose the 1N4148 because:
1. We are controlling switching signals not rectifying AC.
2. From previous experience and the books of the prophets (the manuals) I know that rectifier diodes are slow, potentially causing problems at high RPM. You could use a high speed rectifier, but they are "hot carrier" or Schottky diodes, and drop much less voltage than a "normal" silicon switching diode (which drops 1 V when the current through it is greater than 1 mA, which is the case in this application).
3. The renesis, at 9000 RPM, has an ignition pulse rate of 300 Hz total, or 150 Hz for each leading plug. This is close to the "problem area" of rectifier diodes, so they were not used!

The caps. stopped an oscillation that was seen with one diode. When we added the second diode in series (last month) that problem went away. Hindsight being 20/20, I now speculate that one diode brought us too close to "turn on" of the coilpack transistor, and that was what caused the oscillation (any noise would trigger it, including the noise that triggering it generates - and that's what an oscillation is).

The cap. should not cause any problem that I can think of right now (yes it creates a low pass filter, and that was the point - that's how you stop an oscillation). The slow rise-rate wouldn't cause a problem because the rise of the pulse is just charging up the coil. It's the fall rate that is important. That is what causes the spark. In fact I see no effect on the scopemeter with the caps. in place. Enough owners report a power drop at lower RPM with the caps. in place, and since removing them with two diodes in series is safe, we must conclude that they should be removed! Just clip the end closest to the switch or heat it up and pull it out. IF you have the two diodes in series on each leading output, that is.

As for what all this means, what I see on the scopemeter out of the stock PCM (coil drive lines) looks exactly like what I see when we have two diodes in series as we do now. I suspect there are two diodes on each line that drives a coil inside the stock PCM IC that drives the ignition. I say this because all digital circuit types I'm familiar with do not go down to 0V or up to 5V, they all stop at 1-1.4V min and 4 to 4.5V max. so I suspect the engineers added the two diodes to protect the coils. As I said, hindsight is 20/20.

So, everyone should have two diodes in series as per the pics. posted above. You may remove the caps. if you notice poor performance below 5000 RPM. You can remove the caps. even if you don't have low RPM performance issues.

Sorry to be out of touch for so long.

dannobre

iTrader: (3)

Good to hear from you....we thought that you must have died :D

RPIRX-8

Thanks for weighing in on this RX8-Friend. Its good to hear from someone who was involved with Canzoomer in the dev of this. From that explanation I understand why they were put there and why they have been causing some low rpm issues. Thanks for your work!

Racer X-8

Oh, glory!

RX-8 friend

I'm going to sleep with a smile on my face tonight. :D

I'll read all this tomorrow, I promise! Man, I'm sleepy. Had to say hi right now though!

Yahooo!!!!

SWSDuvall

Hi all,

RX-8 Friend - glad to see you back!

I have a Stage 1.1 with the "old" circuit board and attached a pic.

I've been reading some old post, espcially this one https://www.rx8club.com/series-i-engine-tuning-forum-63/questions-about-stage-1-x-please-31438/ about "cutting resistors" and such.

With all your fresh knowledge, can you advise what we (those with the older units) should do? I can handle a soldering iron so, I can re-hab the board if needed.

Another thought, can an updated ignition board be mailed to me if I pay shipping? As all the wires are color coded and we have lots of pics it would be as "simple" as soldering the new board? Thoughts?

All in all the car runs fine, and pulls nicely with your "medium" M-flash map.

Thanks much!

Steve

Xyntax

Did it and on/off settings feel the same now. Could this be that my CZ is just bypassing now? lol

I don't feel any change if I turn it off or on with the 2 caps removed. Maybe my 8 was already fast? Adding CZ might have just added 1 HP for me. Oh well, at least its tuneable right?

RX-8 friend

Well, we are splitting hairs here, however, according to the data sheets the 1n4007 has 15 pF of juction cap. whereas the 1n4148 has 2 pF. The reverse recovery time of the 1n4148 is 4 nS, and isn't listed for the 1n4007 (because it isn't intended as a switching diode). I suspect it would be in the 30-50 nS range. What I meant is it may work, but isn't intended as a switching diode. This application calls for a switching diode. At least to me.

As for forward voltage the 1n4007 drops 0.7 or so at 10 mA whereas the 1n4148 drops 0.9 or so at 10 mA. The avalanche voltage is the breakdown voltage of the diode, isn't it? I doubt anyone will break down any diode in this circuit that sees a max. voltage of around 10 (pulse reaction spike from the coil transistor turning on).

As for older boards, check the posted pics. at the beginning of this discussion. Your older dip switch board is there with the modifications included. It's a big job to change to the newer board, best left to us. Lots of wires to move, new wires to add, and they are not in the same positions as the older board. I suggest changing to the new board be done when you're ready to return your unit at some future time - for now you can update your older style board. Updates are "free" (except for shipping expenses).

When you turn your older board equipped unit "off" the ignition advance is still functional. To turn it off you have to reverse the position of the four dip switches on the board as well as the external switch. That is one reason I recommend getting the newer board installed. Its' switch turns everything on and off.

epitrochoid

fast or not...at least it runs

epitrochoid

Took it out again today to run some errands, yesterday I pretty much drove WOT for 15 minutes.

1. If I do a 2nd gear start or am a gear up from the lowest I could downshift too, the engine lugs like crazy. I don't know if it's missing or not, but it doesnt accelerate and the car kinda leaps forward in short bursts. it's not bogging, im talking like 3rd gear 3500 rpm it does it.

2. idle has gotten a bit worse...but still way better then before the caps, could be placebo..

any thoughts guys? coils look fine.

Xyntax

I have your problem #1. I noticed it today while I was running around before going to work. There is a weird on and off surge of power under 5K in every gear. When I cruise, it finally goes smooth. It only happens when I accelerate (both slow and fast). I drove it last night with CZ off and my 8 was way faster chirping 2nd and 3rd gears and it pushes me to my seat. CZ on with caps removed feels like before my M flash. Damn it.

Speed Racer

I had similar problems but was able to smooth things out with some tuning. I noticed when I would lift off of the throttle the car would actually accelerate harder. I data logged a few 3rd gear runs at partial throttle and observed the AFR was all over the place even though the throttle was being held steady. I made some changes in each column to smooth out the transition from 0-100% throttle and that seems to have corrected the problem.

Xyntax

Good to hear that Speed Racer. I wish there was some way we all could share our maps online and put some sort of description beside it. Maybe even a sample pic of AFR diagram for the map.

I'm gonna have to purchase the cable!

Speed Racer

I was thinking the same thing. It would really help the rest of us get up to speed on tuning the engine.

Magic8

Question for those who know:

I just finish logging my car. I didn't fool around with the CZ map because I don't have the cable and software yet. I am running AFR around 14.7 everywhere, that stoich isn't it? It seem rather lean. To my understanding I should be targeting around 13.5 or detonation. Conditions in Cincinnati I rather mild so I guess that why my car hasn't run into safe mode.

Also I log several instances when the AFR hits about 25.4. It always happens when there is a steep drop in RPM so I am guessing this is normal.

Also when logging ignition advance, a negative is retard and a positive is advance right?

Looking at the data it looks like I was logging +30 to +40 ignition advance most of the time I was driving. I was driving more agressive with more instances of WOT.

What is the O2s1 Sensor measuring?

Xyntax

02S1 sensor would be the wideband 02 sensor in our car. Am I right?

For a simpler reading (uncorrected), multiple the canscan data by 14.63. More knowledgeable people here mentioned about correction charts for these readings for more accuracy. I dont know if the uncorrected data would be reliable to tune with.

epitrochoid

you can run 14.7 under partial throttle, just not WOT...

try a tps recalibration

RPIRX-8

I'm using 3rd gear for my data runs and trying to tune for 13.5-14 AFR.

slavearm

Does your CZ Canscan post pretty high AFR? Mine is producing 14.5 at anything less than 50% throttle, and its hitting 20.7 under deceleration (in gear) or 14.7 when in neutral and decelerating.

Slavearm

Xyntax

My AFR at WOT goes as rich as 11.0 (CZ or nothing)

I always reference my graphs to Maniac's, and his was tuned to 13 I think.

Magic8

That's exactly what mine is doing.

I'm going to try again but this time I'm going to record the Throttle position. How do you read the O2S1 sensor anyway. What is that measuring?

epitrochoid

are there not seperate maps for gears 1-3 and 4-6?

Speed Racer

Racing Beat said that there are separate maps for gears 1-4 & 5-6

RPIRX-8

Yup I tried messing with 50% and below throttle position on the maps, didn't work out too hot. I would leave those alone.