Just wanting to see if anyone out there isnt running trailing ignition. Its not on my car and so far everthing seems normal(with the help of haltech). If any of you guys no reason not to or to run it go ahead and chime in.

Kind Regards
mike

 

Running just the leading plugs will reduce the power output, and the emissions and gas mileage will suffer. While I do not know of any problems with this, I see no advantage. Why can't the Haltech run the trailing plugs?

 

I did run without trailing ignition for a while when I had timing issues. Dragstrip HP guesstimates show that I went from 100hp (leading only) to 120hp (leading + trailing). This was on a street ported 12A that still had fuelling issues, carb flow issues, etc. (Timing was 20/10 at max mechanical advance, with MSD/twin coils for leading ignition)

Either the trailing was worth 20hp or 20% more power. It definitely was a difference, though, but didn't feel any different to the butt dyno. Time slips, however, dont lie.

 

When the trailing coil died on my work van power dropped and fuel consumption increased.

 

I also felt no difference with trailing turned off and on while driving. I did however feel the difference after I installed a clutch fan. They say a clutch fan typically uses 15HP. Man my engine felt sluggish with the clutch fan. Trailing ignition switched off certanly didn't reduce power output (by 15HP or 20HP) according to the butt dyno.

 

The clutch fan doesn't really draw more power than an electric fan turned on - after all, either way the power is coming from the crank - but the main deal with the clutch fan is that it is more mass that has to be accelerated. That's why when you aren't running two belts on the water pump pulley and a clutch fan, the belt won't squeal at a constant RPM but it will slip when you accelerate. It not only takes power to turn the fan, but it takes power to accelerate the fan. And that's what the butt dyno (and timeslips for that matter) feels, not power but *acceleration*.

Lacking trailing plugs hurts the power, the clutch fan hurts acceleration. Think about that the next time you're putting your stock 20-30lb flywheel back on, or when you're ditching those superlight 13" alloys for some 15s or worse......

 

This is a good discussion guys, lets keep it up. My idea was for easier tuning by only controlling leading not that haltech wont run trailing as previously asked. Ive got a nice msd setup, so im also hoping that will make up for a percentage of trailing loss. Not to start a argument but, i was at gateway(nopi) last year and there was a 1st gen turbo running 8.12 1/4 mile. So asked his crew about running no trailing. Hey what the hell this guys car runs great hes got to know the answer. He said "It doesnt do much but it does somethin". Thats a real nice answer from a crew running 8s. As far as the fuel economy goes, im not concerend about it, its a rx7. The plugs have been looking good so far since its been running but im leaning it out alot at idle to not foul them.

 

The trailings will provide a more complete burn. This will increase engine efficiency. whenever you increase efficiency your increasing power. I can't see why you wouldn't want that. Running without the trailing makes no sense to me.

 

All my 13Bs with DLIDFIS also run trailing because there's no reason not to. The only engine of mine that won't run trailing any time soon is the 20B simply due to the difficulty of getting everything to fit within 120º and the amount of parts it requires. Then again, my 20B is the only one I know of that also will have 0º and 180º leading sparks per rotor spaced 120º apart.

I'm going to test fire it this week or next to test my experimental ignition.

Both my REPUs are gonna use heavy stock 33LBS flywheels for now. One may get an electric fan though.

 

I'm afraid that's too technical for me to understand.

Ah, now I'm beginning to get the picture.

Road racers run 0 split for more power, even though the Motec is capable of running a split. It is possible that there was a mis-communication between you and those Nopi drag racers.

 

yeah i was questioning the layot of the plugs, was wondering if you put two side by side, then had a 3rd centered plug for late burning if it would be any more effective.

 

Has anyone ever tried to have three leading sparks per plug? L1 would look like this:

0º
90º
180º

Granted this may not allow enough time to saturate the coil at high RPM, but it would add another spark to the mix. It wouldn't be that difficult to accomplish with an aftermarket wheel on the main pulley.

 

I forgot to explain what 'driving' meant. The butt dyno felt no difference while accelerating under heavy and light loads (up a hill or flat ground).

Logically speaking, the more spark you have, the more power you'll make. I just didn't feel a difference in output from the one engine I've tested so far in several driving conditions. That said, I will always run trailing unless I've got a very good reason not to (heh, like not enough room for six coils let along three j/k).

 

been done on the infamous R26B, although i'm still thinking two plugs next to each other followed by a third centred trailing plug may be more effective, as i'm thinking the width of the rotor may be too much for one plug.

 

On the R26b (the LeMans 4 rotor, I can't remeber if that's what it was called!) it had 2 trailing plugs, and all they lost was a slight amount of power due to compression loss, but gained a few lbs of torque

 

It's my understanding that the R26B actually fired the regular L and T plugs together (0 split) only once and fired the third late trailing plug a little later. Of course the advance was cranked up too. This means only three sparks total per rotor face.

 

wouldn't it be better to just have one or two plaugs (as is) and just hook up a timing device that tells rpm to an external ecu then set up a Distributer Less Timing system (DLT) like the twin turbo supras have then just have the same plug spark twice in the time that the rotor passes therfor creating a trail through the same two plugs.

 

3 Plugs, 0 Split, Special rotors
http://www.mymazdarotary.com/mazda_r...paper_html.htm

 

Shamrock.James, The '93+ RX-7 already does this on the leading plugs. It has a timing wheel on the front pulley hub and is distributorless. It fires both leading plugs at the same time. This has the effect of sparking the L1 plug at 0º and 180º. Although it doesn't spark into the trailing section of the compression 'dish', it does its job in further igniting the fuel in the 'squish' zone.

The '86+ RX-7 uses a CAS and ECU to accomplish these dual leading sparks as well.

The little ignition mod I like to call DLIDFIS for '81-'85 1st gen RX-7s and older rotary vehicles with FB distributors, also has dual leading sparks.

Once again, my experimental ignition for the leading plugs of a 20B will also ignite the fuel in the 'squish' area by imploying the same dual leading spark idea as mentioned above.

I noticed a marked improvement in HP and torque everywhere in the RPM range of my 13B, along with better gas mileage, with dual leading sparks. It makes me wonder how the R26B would have done with something like that. Heh, four sparks per rotor face would have been great on a four rotor engine.