jack_am

Red94fd

iTrader: (5)

Yes, that happend on my tunning session, i tested a lot of things, ended up being my hks ignition amplifier. I changed somethings in the process, fc coil, race plugs 9 and 10 and got a replacement hks twin power. Change the plugs and see what happens. Do you have good fuel presure? Fuel filter changed? Check for boost leaks too.

jack_am

peejay

Try the 10s and don't be afraid to close up the gap a little bit under higher boost.

I was breaking up on 9s with N/A! The 9s were okay in lower gears but if you loaded it a long time it would start to miss.

Red94fd

iTrader: (5)

+1 on the 10 spark plugs

silverTRD

iTrader: (36)

Speed of light

iTrader: (8)

You mentioned that you're using a MSD 6A + GM twin coil on the leading. Correct me if I'm wrong, but I'm assuming this is the GM wasted spark coil serving both leading plugs. If so, I use this same combo (although now with a MSD 4224 GM replacement coil) and it has proved to be a very strong, high current ignition. It will light off everything I throw at it and I've never had any problems or misfires until the leading plug gaps grew to about 0.100" each (yes, that's 1/10th of an inch); at that point, it was starting to miss under load at about 15psi boost, and that's with a substantial amount of water injection too. Plugs were Autolite 3932's and wires stock NGK. Trailing ignition is stock with upgraded plugs gapped at around 0.025".

The only complaint I have about the forgoing setup is that it wears out leading plugs pretty quickly. BTW--I never had very good luck with the stock 9's--I noticed that once they begin to wear, the spark moves from the surface of the plug further down inside which kills throttle response and makes it feel like its misfiring at times. One thing to be aware of if you switch over to other, non-conventional plugs is that the ceramic insulator (outside portion of the plug) may be smaller in diameter and not fully seal with the plug boot. If this occurs, the spark can and will flash over the exterior of the insulator when under load leading to misfires. One work around is to build up the insulator with a layer or two of heat shrink tubing (I had this happen when I was trying out some NGK BR10EIX plugs). And while we're on the subject of spark plugs, my experience with an ignition such as this suggests better results with convention plugs that have a large diameter center electrode (as opposed to the fine wire types).

Good luck. If everything in your ignition is up to snuff, it should work great.

jack_am

Cheers guys, will give those 10s a go on the leading and see if it improves.

@Speed of light: yeah, I was disappointed that spark would be breaking up with the MSD set up. When you pull the plugs and test the spark on the chassis it's like a laser beam, so strong. However I tested it with 10s so I've not seen what the spark looks like on the 9s. The 10s I've got are NGK BR10EIX, we'll see how they go. What gap did you run without the water?

jack_am

ECU is a Power FC, car is a '93.

Speed of light

iTrader: (8)

I ran them at about .040" (an increase from the .031" stock gap). Quite honestly, I was not particularly enamored with the -EIX plugs--even with the gap opened up, the throttle response and the way the engine took load just didn't seem very good (as compared to conventional plugs such as the BR10EG/ES or equivalents).

jack_am

Cool, I'll give that a go. I'll throw the EIXs in and see how I go, I might order up some EGs as standby.

Skeese

iTrader: (11)

I had one of those HKS amplifiers die on me too, then explode into flames in the bay. Long story short I'm not a fan. That all being said....I've chased ignition breakup issues in circles before from ECU settings to coils to plugs and at last found the issue was due to 2/4 ignition wires having randomly dropped connection. I was running on L1 and T2 and as the split increased with boost the vibrations and breakup got more and more severe. It's probably worth taking a multi-meter and just checking the resistance on the wires if for nothing else just to eliminate it from the possibilities. Anything more than 200 ohms of resistance is no good...I believe the MSD aftermarket wires claim something like 50 ohms per foot.

Sounds about right. That company has no issue using your car as a software experiment. In my opinion, running their *guesstimated* software embedded with ignition timing and firing discrepancies is pretty much asking for it...if it goes kaboom, they'll blame poor tuning or the engine. It's just sketchy.

Skeese

jack_am

^^ I'm running MSD HT leads all round, will put the meter on them.

peejay

You shouldn't ever open up the gap on these super-cold plugs! The heat range is determined by how short the heat transfer path to the outer shell is, meaning how deep the "well" around the ceramic insulator is. Colder plugs have shorter wells. The R5671-10 plug has a well about half the depth of a -7 or -8 ish plug, and it has a .020" gap because if you go much more than that, it is very easy for the spark to bypass the gap entirely and surface-discharge across the insulator instead.

Some of the much colder race plugs have a gap in the .010" range!

Yes, running this kind of gap does make the engine more sensitive to tuning... When I switched from stock type 9s to the R5671-10s, I had to richen my cruise mixture almost a full ratio in some areas. Welcome to the tradeoffs of modifying...

SakeBomb Garage

iTrader: (17)

We've stopped so many dyno sessions here because of breakup.... luckily our parts department is 40 steps away so we can swap in coils on the dyno. Once and done, never think about ignition issues again. Just do it, trust me, it's THE solution.

IGN-1A High Performance Ignition System (FD3S RX-7, LHD Mount) - SakeBomb Garage LLC

jack_am

Lol. Nice plug...

I already have some IGN1As on the trailing but I want to give the MSD leading set up a fair try too. Also with the dollar being so strong against the pound I can't afford to buy anything from the states :P

SakeBomb Garage

iTrader: (17)

Why would you put a lesser coil on the leading? The IGN1A is the correct coil for the application... everything else is designed for 4 stroke motors (so half duty cycle). Even high output coils don't actually output much once you double the firing rate the coil was intended to operate under (see the LS coil issues). The IGN1A was designed from the ground up as a 2 stroke coil (fast recharge times were the #1 design goal).

So it's not a plug, buy them anywhere, but buy IGN1A's is the point. A strong dollar doesn't triple the price of the coils... and MSD is made in the states as well. Just do it once and right.

Cheers!

peejay

I have found through much trial and error that the trailing ignition is more important than the leading under light load conditions if you have a high overlap engine (aka bridge or peripheral port). To the point where the engine may not even run at all if the trailing is disabled.

That's A reason...

jack_am

SakeBomb Garage

iTrader: (17)

And that's at what duty cyle? This is the entire point.... the LS Truck coils (d585) and MSD coils, for instance, are brilliant on piston engines. Cheap and high output coils. Problem is they CAN NOT RECHARGE FAST ENOUGH... so the 135mj output is nothing close to that when you fire them TWICE as often on a rotary (or 4x in waste spark). They're not designed to recharge this quickly. The LS and MSD coils are great for what they were designed to do, but double or quadruple ignition evens is not what they were designed for. 18,000 RPM equivalent on a piston engine in direct fire, and 36,000 RPM equivalent in waste spark.

Feel free to continue experimenting, but the IGN1A was designed from the ground up as a high ouput two stroke coil (aka rotary ignition events) meaning the internal design is focused on ultra fast recharge times. This is why it's the only choice for rotary coils, no one else makes a 2 stroke (rotary) coil that's this high output and durability.

jack_am

I thought the whole point of a CDI was that dwell time becomes irrelevant, the capacitors can store more energy than an inductive coil can build?

Skeese

iTrader: (11)

Duty cycle and dwell/charge-time isn't relevant in a CDI compared to an inductive coil which generates its spark charge through current passing through its windings for a dwell time. With inductive coils, when you have to trim dwell to keep you in the rpm window you lose spark output, regardless of whether you're running in wasted spark OR direct fire. As the CDI box serves as a power reservoir from which the coils draw their charge (hence Capacitor Discharge Ignition) the coils do not have to go through a "dwell" time to charge. I don't know about MSD, but M&W CDI boxes are spec'd for a max of 10,500-20,000 rpms depending on model.

Not to mention that the CDI ignition has an extremely short spark duration in comparison to the AEM coils, which is a positive in the case of extremely high rpms as you don't run the risk of having the rotor face open to the next charge with the trailing plug still lit. Short duration spark also means more time for the plug face to cool between firing events. Sure the AEM coils are good coils for a mid-power street car, but they are not the only solution. You can't really argue for a product you're selling calling it the best when you don't know how the alternative product works.