A topic you don't see here often: detonation?
09-17-01, 10:10 PM
#1
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Thread Starter
A topic you don't see here often: detonation?
Can my 12A be detonating? That would explain the severe powerloss I am experiencing right? Its making this funny crackling sound when I get on the throttle; the louder the sound, the more power loss. I have new fuel in it, but the truth is driving N/A RX-7's all my life I really don't know anything about it and I wonder how to cure it? Its a used motor that I just put in, it was overheating for a while but thats done now, and now the power comes and goes. Sometimes it will make a really strong run up to redline; other times it bogs down and crackles. What should I do?
09-17-01, 11:30 PM
#2
Old [Sch|F]ool
That sounds exactly like when MINE was detonating. I would describe the nose I experienced as more of a belt-chirp type noise but a LOT louder. It would start and run great, and part-throttle was GREAT, but as soon as you started to ask more out of it (like accelerating with traffic on an on-ramp) and it would buck back and chirp and sometimes there'd be black smoke. Couldn't even exceed 75mph.
First of all, I had the timing advanced 30 degrees too far. (You CANNOT use a dial-back timing light with an MSD! If you do, keep it set to 0 degrees and mark off your e-shaft pulley to find out how much advance you have.) I fixed that and the problem was pretty much gone, except for high-gear hard acceleration, like passing a truck up a slight grade at 65-75mph.
More detective work - I had the dizzy stabbed in 90 degrees off. This did not affect the leading ignition one bit because I did the direct fire conversion... however the TRAILINGS were firing at the right time but for the wrong rotor! So the trailing plugs were firing halfway into the compression cycle! Instead of pulling and re-orienting the dizzy (which would require pulling the A/C compressor and its huge-*** bracket) I just swapped the T1 and T2 plug wires - all better now!
Blame it on inattention and a still boinger-centric mind - I wasn't paying attention to the position of the ROTOR when stabbing in the dizzy, I just looked at the reluctor wheel to get it close before I set timing. Oh well, it was a 50/50 shot at getting it in right!
First of all, I had the timing advanced 30 degrees too far. (You CANNOT use a dial-back timing light with an MSD! If you do, keep it set to 0 degrees and mark off your e-shaft pulley to find out how much advance you have.) I fixed that and the problem was pretty much gone, except for high-gear hard acceleration, like passing a truck up a slight grade at 65-75mph.
More detective work - I had the dizzy stabbed in 90 degrees off. This did not affect the leading ignition one bit because I did the direct fire conversion... however the TRAILINGS were firing at the right time but for the wrong rotor! So the trailing plugs were firing halfway into the compression cycle! Instead of pulling and re-orienting the dizzy (which would require pulling the A/C compressor and its huge-*** bracket) I just swapped the T1 and T2 plug wires - all better now!
Blame it on inattention and a still boinger-centric mind - I wasn't paying attention to the position of the ROTOR when stabbing in the dizzy, I just looked at the reluctor wheel to get it close before I set timing. Oh well, it was a 50/50 shot at getting it in right!
09-18-01, 12:13 AM
#3
It's Back!
Thread Starter
YES! A loud belt-chirping noise thats it!
I think it might be that the timing is a little off. I'm still running the stock ignition system (plan on doing the shadetree MSD job once I get it running right) what is the dizzy? I've heard this term before. Sorry, I know nothing about ignition/electrical systems. . .
I think it might be that the timing is a little off. I'm still running the stock ignition system (plan on doing the shadetree MSD job once I get it running right) what is the dizzy? I've heard this term before. Sorry, I know nothing about ignition/electrical systems. . .
09-18-01, 01:37 AM
#4
I can tell you that the MSD shouldn't be used on a rotary. Oh sure you could use it, but I know for a fact that it doesn't work very well. Screw what 'racers' say. Do you really think they'ed let their competitors get ahold of their best guarded secrets?
The MSD's multi sparks end at 3000 RPM. After that it is only a CD spark which, by it's nature, is a short duration spark. Correct me if I'm wrong, but rotary engines spend pretty much all their running time reving much higher than 3000 RPM. They also like long duration sparks which the MSD cannot give. The MSD was built for points distributors on piston engines, not electronic ignition replacement on rotary engines. Oh yeah, those white MSD boxes contain the exact same circuitry as the red ones. Send them an email asking what the difference is if you want.
The term dizzy is a distributor. You obviously are new to ignition stuff, but you have an interest in direct fire so I'm going to post a link to an article I wrote on the subject.
http://www.geocities.com/cd23c/dlidfis.html
Please read it and absorb as much as you can.
The MSD's multi sparks end at 3000 RPM. After that it is only a CD spark which, by it's nature, is a short duration spark. Correct me if I'm wrong, but rotary engines spend pretty much all their running time reving much higher than 3000 RPM. They also like long duration sparks which the MSD cannot give. The MSD was built for points distributors on piston engines, not electronic ignition replacement on rotary engines. Oh yeah, those white MSD boxes contain the exact same circuitry as the red ones. Send them an email asking what the difference is if you want.
The term dizzy is a distributor. You obviously are new to ignition stuff, but you have an interest in direct fire so I'm going to post a link to an article I wrote on the subject.
http://www.geocities.com/cd23c/dlidfis.html
Please read it and absorb as much as you can.
09-18-01, 12:37 PM
#7
Yeah I could help you. Well not physicaly since you live kinda far from me.
Turn the engine clockwise by hand until the first notch on the pully comes up to the little peg on the front cover. Then, with the cap, rotor, and aluminum cover removed, the flat section of the shaft should be pointing basicaly forward toward the front of the car. A few degrees from striaght ahead is ok. Next look at where one of the reluctor vains is in relation to the forward most pickup. The sharp edge of the reluctor should be right near the little edge sticking out of the pickup coil. Loosen the dizzy hold down plate bolt/nut and rotate the dizzy untill the pickup lines up with the reluctor. If the shaft is 180* offset, now is a good time to correct it. The gears are curved so you will have to apply a twisting motion while inserting the dizzy.
Make sure the flat section is pointing forward and the vain is closest to the forward pickup.
Now for setting the 10 or 8* split, I'll let somebody else answer that one.
Turn the engine clockwise by hand until the first notch on the pully comes up to the little peg on the front cover. Then, with the cap, rotor, and aluminum cover removed, the flat section of the shaft should be pointing basicaly forward toward the front of the car. A few degrees from striaght ahead is ok. Next look at where one of the reluctor vains is in relation to the forward most pickup. The sharp edge of the reluctor should be right near the little edge sticking out of the pickup coil. Loosen the dizzy hold down plate bolt/nut and rotate the dizzy untill the pickup lines up with the reluctor. If the shaft is 180* offset, now is a good time to correct it. The gears are curved so you will have to apply a twisting motion while inserting the dizzy.
Make sure the flat section is pointing forward and the vain is closest to the forward pickup.
Now for setting the 10 or 8* split, I'll let somebody else answer that one.
Last edited by Jeff20B; 09-18-01 at 12:39 PM.
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09-18-01, 02:42 PM
#8
Super Newbie
Originally posted by peejay
Instead of pulling and re-orienting the dizzy (which would require pulling the A/C compressor and its huge-*** bracket)
Instead of pulling and re-orienting the dizzy (which would require pulling the A/C compressor and its huge-*** bracket)
09-18-01, 02:45 PM
#9
Super Newbie
Originally posted by Jeff20B
I can tell you that the MSD shouldn't be used on a rotary. Oh sure you could use it, but I know for a fact that it doesn't work very well. Screw what 'racers' say. Do you really think they'ed let their competitors get ahold of their best guarded secrets?
The MSD's multi sparks end at 3000 RPM. After that it is only a CD spark which, by it's nature, is a short duration spark. Correct me if I'm wrong, but rotary engines spend pretty much all their running time reving much higher than 3000 RPM. They also like long duration sparks which the MSD cannot give. The MSD was built for points distributors on piston engines, not electronic ignition replacement on rotary engines. Oh yeah, those white MSD boxes contain the exact same circuitry as the red ones. Send them an email asking what the difference is if you want.
The term dizzy is a distributor. You obviously are new to ignition stuff, but you have an interest in direct fire so I'm going to post a link to an article I wrote on the subject.
http://www.geocities.com/cd23c/dlidfis.html
Please read it and absorb as much as you can.
I can tell you that the MSD shouldn't be used on a rotary. Oh sure you could use it, but I know for a fact that it doesn't work very well. Screw what 'racers' say. Do you really think they'ed let their competitors get ahold of their best guarded secrets?
The MSD's multi sparks end at 3000 RPM. After that it is only a CD spark which, by it's nature, is a short duration spark. Correct me if I'm wrong, but rotary engines spend pretty much all their running time reving much higher than 3000 RPM. They also like long duration sparks which the MSD cannot give. The MSD was built for points distributors on piston engines, not electronic ignition replacement on rotary engines. Oh yeah, those white MSD boxes contain the exact same circuitry as the red ones. Send them an email asking what the difference is if you want.
The term dizzy is a distributor. You obviously are new to ignition stuff, but you have an interest in direct fire so I'm going to post a link to an article I wrote on the subject.
http://www.geocities.com/cd23c/dlidfis.html
Please read it and absorb as much as you can.
My car with an MSD DFIS setup doesn't exhibit the things that you said your REPU did, though. My car starts easily (ask rx7passion), never needs the choke, doesn't backfire, etc.
I still think I'll try your setup just to see. Its gonna have to wait until I get my bitch back together though.
09-18-01, 06:29 PM
#10
Old [Sch|F]ool
Heh, yeah, I know about the MSD's shortcomings... I'm on the Mazspeed forum off and on (username SPRT - I am the Shallow Pockets Racin' Team) and I've been following the PMDFIS thread with interest. I always wondered why the engine seemed to go a little flat past 7k - the MSD's limitations are probably why.
HOWEVER - I decided that for now I won't remove the MSD and go PMDF (Poor Man's Direct Fire). I have a 6AL box which is quite useful - no worries of overrevving. Get in the burnout box, three-pedal it at the limiter in 2nd gear, no muss no fuss. No worries about overrev when missing a shift. (Which happens all too often these days) And most importantly... true to the SP part of SPRT, my racer is also my daily driver. Daily driving entails a LOT of sub-3k running, as well as cold starts in sub-freezing temps. I love my MSD for this - it's like night and day vs. the standard ignition setup.
And another thing - 30-50mph in 5th gear - 6 seconds - from a 12A and stock gearing. NUFF SAID.
HOWEVER - I decided that for now I won't remove the MSD and go PMDF (Poor Man's Direct Fire). I have a 6AL box which is quite useful - no worries of overrevving. Get in the burnout box, three-pedal it at the limiter in 2nd gear, no muss no fuss. No worries about overrev when missing a shift. (Which happens all too often these days) And most importantly... true to the SP part of SPRT, my racer is also my daily driver. Daily driving entails a LOT of sub-3k running, as well as cold starts in sub-freezing temps. I love my MSD for this - it's like night and day vs. the standard ignition setup.
And another thing - 30-50mph in 5th gear - 6 seconds - from a 12A and stock gearing. NUFF SAID.
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