Jeff20B

iTrader: (13)

I think I met Skip in real life. Didn't he have a propane powered REPU? He was a cool guy, and if he says that it's better to not run trailing for various reasons, I'm not going to argue just for the sake of arguing.

I was waiting for RETed, but here goes. To answer your questions, this sentence:is utter BS unless the timing goes haywire from a screwy ECU or something. Maybe you didn't explain it very well. I can't understand how something like that could happen within the normal advance curve of a 13B. We're talking about severely retarded trailing ignition in the region of over 100° ATDC. Where is the apex seal of the rear rotor when the front is at TDC? The rear is between the plugs. Now maybe what you say could happen if the trailing select signal didn't get to the trailing ignitor on time and the same trailing plug was fired twice in a row, but I've never heard of that happening before. I guess a loose connection could cause it, but I highly doubt an engine tuner tuning to the ragged edge would overlook something like that (it could happen though).

Another thing you mentioned about firing too early trying to make the piston or rotor reverse its direction has some merit, but did you know the combustion forces are fairly plastic, and that if they weren't, an internal combustion engine wouldn't run? Sounds to me like running lean and detonating is a better way to crack rotor housings and dowel pin castings than too much advance.

Lastly, why is deleting the late leading spark less likely to cause detonation? It occours 180° AFTER the first spark on that rotor face. I can see how it could ignite the incoming fuel mixture too early if the timing was really retarded, but who runs THAT retarded? Not even highly tuned nitrous turbo 13B drag racers making well over stock power are that retarded. Of you have some examples of anyone who is not associated with KDR, I'd like to see them. All I have are factory service manual advance curves and what Paul Yaw and Racing Beat recommends.

RETed

Funny, this was claimed directly by the shop.
Man, I guess you missed the part about me saying - I didn't claim that; the shop did.

The stock ignition maps fire both leadings and trailings at the same time at certain engine loads.
So how do you account for that?

Have you ever indexed rotor position versus TDC?
You'd be surprised on what you find out...


-Ted

RETed

Uh, do you know how it all works?
With the leadings wastespark'd the "third" spark fires as a "far trailing", effectively allowing three sparks per rotor face.
Now, I understand that having a massively retarded (leading) ignition timing can allow for firing that "third" wastespark to fire in the next rotor face, but this should not be possible on a stock ECU (especially FD3S since you cannot adjust ignition timing unless you're stupid enough to swap the trailing spark plugs wire positions) or run some kinda aftermarket ignition retard.

I can confirm that an aftermarket retard will blow the engine up.
We had an FD on the dyno running a J&S Safeguard with 20-degree max setting that the stupid dyno operator kept telling the owner to floor it after it was making some HELLACIOUS noise due to detonation!
The J&S was pegged FULL, and the dyno operator told the owner to IGNORE the J&S display...
The engine let go after the 3rd pull.

BTW, that T78 with 20psi I'd expect to hit at least 450hp with the trailings working...maybe even closer to 500hp?
But, if you're happy as the owner, I can't blame you...


-Ted

Turbonut

iTrader: (1)

Well, without getting into a long story, you're going to loose a lot more than 2 HP when the trailing plugs go out. My '88 TII, I purchased new, developed a problem with the trailing plugs not firing after only 600 miles. Mazda and NGK engineers were working on the problem, but never came up with a solution on the S4, but on the S5's you'll see that the trailing plugs are further apart from the leading. I could really feel the difference 4,000 RPM and up when the trailing plugs didn't fire. Some people didn't know that the trailing plugs weren't firing. One car I worked on, I disconnected the leading igniter to check, and the car shut off, no trailing spark, and the fellow didn't even realize that.
Proof of the problem, Mazda bought my '88 back and gave me the S5 TII, which I still have, for dealer's cost. I also still have a letter from NGK explaining that they were familiar with the problem, and were working to correct the situation.
This is not to say you can't overcome the loss of the trailing spark, just by a richer mixture, or more boost, but my opinion is to leave the trailing plugs fire and tune it correctly througout the operating range.

fastcarfreak

Hey you guys could very well be right (most likely are) im still learning, so when you come on and just disagree and not give an explanation, it doesnt help the situation out. Now that you guys have given valid info, now I can be more likely to agree with you. Most of the information I got on this specific product was directly from skips mouth. Maybe i misunderstood what he was explaining to me? Either that or what he told me was BS. What you said came from that shop doesnt match up at all with what he was telling me about the Anti det device.

I am happy with the 435rwhp on pump gas though. I admit it may be a little on the low side for the boost and turbo (not by that much though), but it sure does make enough power to race anything in the area and usually come out on top.

Adam

I dont know anything about a propane repu, btw. So we may or may not be talking about the same person.

fastcarfreak

Hey you guys could very well be right (most likely are) im still learning, so when you come on and just disagree and not give an explanation, it doesnt help the situation out. Now that you guys have given valid info, now I can be more likely to agree with you. Most of the information I got on this specific product was directly from skips mouth. Maybe i misunderstood what he was explaining to me? Either that or what he told me was BS. What you said came from that shop doesnt match up at all with what he was telling me about the Anti det device.

I am happy with the 435rwhp on pump gas though. I admit it may be a little on the low side for the boost and turbo (not by that much though), but it sure does make enough power to race anything in the area and usually come out on top.

Adam

I dont know anything about a propane repu, btw. So we may or may not be talking about the same person.

Turbo23

iTrader: (4)

my thought is, and i am far from any expert or whatever, mazda did things for a reason. Such as why they didnt run 3mm seals, and why they choose 2 spark plugs. Im sure there is a reason as to mazda's extensive research. So im not planning on ******* with it. Ill port and all kinds of stuff, but they make a T and L for a purpose

Jeff20B

iTrader: (13)

Was Skip ever on the west coast? I met him in '00 when he worked for Atkins. He may be a different person than whom you're refering to, but he certainly knew his rotaries.

I'd very much like to try both ignition variations on a dyno and see which makes more power. LT no split or leading only with 180° late firing sparks. Then at least I'd know for sure and could put to rest all the speculation on my part.

RETed

Dude, you really need to boost the motor to feel the difference!
I have a feeling the NA's don't make that much of a difference, but on a turbo 13B it's easily over 2hp.

It's an interesting situation...
I might try and mess with the trailings on the dyno, as I might have a SC 13B going tuning this weekend.
I'll try and see if the owner is willing to play guinea pig to see what kinda numbers will pop up...


-Ted

fastcarfreak

yup, thats him. He retired from atkins rotary. Then came out of retirement when his wife got sick. I think. Skip has been working and racing rotaries for like 30+ years.

Im actually curious myself to how much power loss there really is in a turbo rotary application with and without the trailing ignition.

Jeff20B

iTrader: (13)

It must be the NA curse. I have several 13Bs and not one is boosted. They're all pre '86 style with coolant seals in the rotor housings and 3mm apex seals. All 4 ports too. Heh, the only 6 port I have is a 20B.

Ted, what type of ignition does that SC 13B have? I'm very interested in your dyno results with and without trailing because I'd like to do an SC 13B soon and am debating whether to get another MegaSquirt for spark only (it'll be carbed with no current plans to go EFI, being a 'pre '86 13B 4 port and all). I'll either trigger a 2nd gen leading coil and ignitor assembly with the MS, and trailing as well if they can get the trailing trigger/select stuff working, or stick with the good old DLIDFIS and stock 1st gen trailing through the cap (moved to the leading part for better contact and only one gap to jump), which the vehicle is already set up for, or use my MSD6AL and an MSD or Accel brand double ended coil since there is a spot to install it, or possibly try the transistor trick with a 2nd gen coil assembly to trigger it from a J-109 for proper dwell control and stuff. All those 1st gen guys installing 2nd gen coils triggered only from a J-109 produces weaker sparks than if the it was triggered by the 2nd gen ignitor it came with. Wasteful. Anyway if I can get it to work, and don't feel like soldering up another MegaSquirt, and would rather attatch my MSD6AL to something that needs a rev limiter, I'll just go with the 2nd gen leading coil assembly with the transistor trick, or stick with DLIDFIS. The MS also has a rev limiter, along with boost retard, so I'll have to make my decision when the time comes.

Yep, lots of ignition ideas. Your dyno numbers would help me a lot.

So Skip is the same guy. Cool! He was in chare of the boat stuff at Atkins and helped me over the phone with a few ideas when I was fitting a 13B in my MG Midget. He ha d a propane powered REPU when he lived here but sold it before he moved, if I remember right. I hope he's still doing fun rotary stuff these days.

13btnos

iTrader: (1)

I don't understand all this ignition talk. My setup is simple I use two msd 6al's one for leading one for trailing. I've never had ignition problems and I have a rev- limiter for safety. Yeah it cost some money but well worth it for me and my customers. I put msd 6al's on all cars I build.

Jeff20B

iTrader: (13)

Eep!

RETed

How do you put one MSD6AL for just the trailings???

Oh wait...SA22 with distributor with twin coils, right?
Doh, too much FC with direct fire ignition systems. :P


-Ted