Running NGK 5820 V-Power 10 Range Plugs. 22psi ~500RWHP @ 11.5-9 AFR, 13 degrees Timing with 700CC water.meth injection.

Car has run fine for past 5k miles / 8 months on these plugs. Recently have started to get a stumbling idle. AFR pulsing 13.5-14.0 at idle, sometimes settles out other times pulses. If I hold the throttle and RPM's at 2k, my vacuum is stable and motor is stable at around 17-18mm/HG on large streetport.

I hear all even pulses when cranking with fuel turned off.

Car still has tons and tons of power.


The other day I was experimenting with the 2-step settings in the AEM V1 box. Set two step at 6k rpms, ignition cut, NO fuel cut, and 150rpm hysteresis with 300rpm initial retard. Tried it out 3 times. Worked great every time, sounded like a machine gun and built around 8psi of boost. 3rd time the car came back down and idled at 400rpm's low vac/lumpy and died. Had to raise the idle screw to keep it running right.

Runs fine now with idle turned up to 1200rpms but the car has a random misfiring lots of back firing on/off throttle.

Pulled the plugs and this is the result of the plus in order of top/bottom in rear housing. Installed new plugs and will test out tomorrow when its not to loud during the day.

I'm hoping its only fouled plugs as the top plugs in each housing look pretty black. Seems like two step would easily foul the plugs as its dumping fuel and cutting ignition. But how the hell is the insulator missing? Doesn't it require massive detonation to completely loose the insulator?

 

Stop running $3 spark plugs and that won't happen.

But on another note, "22psi ~500RWHP @ 11.5-9 AFR, 13 degrees Timing with 700CC water.meth injection.", that sounds too hot to me. Your probably relying on whatever variant of unbreakable apex seal you have to not blow up which is the wrong way to do it.

thewird

 

I'm not familiar with those plugs. But two step is hard on all components (turbo, manifold, etc). I'm not sure how the AEM controls it, but I think it might cycle between no spark and spark retard. This could be causing enough heat that those particular plugs can't take it.

You've got a few options. Try different plugs. Stop using two-step, or adjust the way the AEM is controlling the 2-step. What coils do you have? All the various high powered coils and ignition amplifiers used for high horsepower builds are hard on plugs already.

Can you post screenshots of your 2 step settings?

 

Typically my afr is around 10.8-11.2 at peak torque to redline at 20-22psi. Its never exact and changes with weather but never over 12.0.

I guess I can add more fuel to the upper end. Car always pulls clean and hard never and hiccups.

Two step is setting in aem, I have ignition cut set at 6k rpm, timing retard set at 5.5k, and 150rpm cycle of spark cut and spark fire.

The car uses hks twin power on stock coils relocated.

I can post screenshot later on.

Perhaps this occured earlier on in the tuning process. Ill have to monitor the new plugs.

Seal are RA super seals.

 

What do you like to run at those boost levels?

 

you should also see if the remnants of the insulator are still in the trailing plug hole before they manage to work their way into the engine.

NGK 6725-105 plugs are what i recommend, everyone has their own opinion but those are what i have used in numerous builds with the best reliability. many people also run the BR10EIX but they require the special spark plug socket which i hate dealing with.

 

That is a good point. If the parcelain pieces did make their way into the housing wouldn't they be pushed out by the seals into the exhaust ports and demolished by the exhaust wheel? Or should I anticipate damage to the housings and rest of internals

This would be the first case of engine failure from cracked plugs in the rotary world I've heard of..

I didn't see or feel anything in the plug holes. I tried cranking with fuel off, no unusual noises and all even pulses through the open exhaust.

Car fired right up this morning. Going to go drop the idle back to normal and let it warm up to full operating temp.

 

many people also run the BR10EIX but they require the special spark plug socket which i hate dealing with.

The BR10EIX also drop their groundstrap or a portion of it into the engine with detonation/heat.

Had that happen twice on them.

 

[QUOTE=BLUE TII;11710473]many people also run the BR10EIX but they require the special spark plug socket which i hate dealing with.

The BR10EIX also drop their groundstrap or a portion of it into the engine with detonation/heat.

Had that happen twice on them.[/
QUOTE]

Did you experience any damage to the motor from these pieces?

Iv used the br10eix, machined my own socket. Honestly I noticed no difference between those and the plugs I'm using now either.

 

You are too lean at that power level. You should be in the high 10s/low11s AFR. You should also be running NGK 10.5s or 11s for that boost level.

 

Started it up and took it out tonight. I was able to lower the idle back down to 800rpms, pulling around 12-13in vac with a very slight brap.

Pulled a 10.8-11.4 afr across the power band along 3rd and 4th.

Im thinking now that the plug cracked simply from being too hot ( 10's instead of 11's), because it may have been dropped at the store, and/or car may have gone slightly lean during tuning a few months ago.

Going to order some 10.5. However I found another version of the same $3 ngk plugs in 11's. If they are changed frequently I don't see the reason in buying $40 plugs...?

 

If you buy an iridium R7420 it will last you 15,000 miles, look at it that way instead. And if the insulator did go in the engine, you just damaged a perfectly good running motor trying to save a buck (though to be frank that's why 90% of rotaries blow anyway, owners/builders cheap out on something).

You wouldn't be the first or the last owner to damage an engine putting cheap plugs in there. Local guy broke an engine due to some cheap autolite plug, don't remember the model.

thewird

 

If you guys really think it makes a huge difference Im strongly considering the NKG R7420. But from all I can gather, these plugs simply last much longer as they are iridium rather then copper. But if one was to change copper plugs at every oil change for $10, running correct heat range, and without breakup, then what's the difference really?

Does the R7420 or the old racing plug r6725 really deliver more energy then a conventional plug? Or simply longevity?

 

Gotcha. Just posted at same time you answered my question.

I guess its not worth risk, with 40k plus into a car, it deserves high end plugs.

Thanks

 

The R7420 and R6725 are the same plug. Only difference is the R7420 is iridium instead of platinum so it lasts twice as long. Considering they cost the same (only $1 more i think), it makes sense to get the R7420 regardless.

Copper plugs are toast in a turbo rotary in under 1k miles if the car is driven hard. Probably less at your power level. Need at least a platinum plug.

thewird

 

Any other suggestions to look for engine damage?

Vac seems normal, cold hot start normal, power normal, no smoke.

I'm assuming insulator had to have gone into the housing, no where else to go. It had to have been pushed out by the rotor?

 

Just ordered a set of 7420-11's, going to run 4 of them. Piece of mind worth every penney.

Thanks for advice.

 

Compression test would be easiest way to know for sure. Do you know what vacuum you were getting before? You'd be pretty lucky if it just went out with exhaust.

thewird

 

Cold motor will pull -11 to -13 at around 600-750rpm. I run no idle air valve.

Warm it will pull around 13-14in at 1000. If hold it at 1200 I see -15 to -16.

Seems exactly same as before.

Ra seals large sp, figure that explains the lower vac. Motor always been little hard to start vs my reman.

 

Did you experience any damage to the motor from these pieces?

Iv used the br10eix, machined my own socket. Honestly I noticed no difference between those and the plugs I'm using now either.

The first time the ground strap just scored the RA 3mm superseals at the housing to seal surface an put some marks in the rotor. It ran poorly at first and then compression came back up very quickly.

It ran the same as always once I replaced the plug but I found bad nicks in the apex seals on that rotor much later on tear down.

It did not affect the engine performance noticeably as the RA seals have such poor sealing anyways from grooving the housing surface.

Second time the ground strap became impacted in the rotor right at the edge and pinched a side seal so the motor had to be taken apart and fixed.

 

yeah i somewhat remember you mentioning that, i personally don't recommend using cheap plugs because the result is never in your favor.

up to 350whp you can usually get by with the standard 9's but above that you just have to bite the bullet. armature plugs aren't even really recommended for high power applications but they are also the only reliable type of plugs available. those AR3932 surface discharge plugs are total garbage. others have made their own versions of SD plugs by bending the strap and cutting it to arc to the side of the electrode, but this also causes the electrode to wear unevenly and quickly. all other SD plugs have excessive gaps, which are too wide for high power/boost.

would be nice if they made a plug for performance rotary applications but unfortunately there really is no ideal plug available at the moment, and probably never will be mainly due to cost because a SD platinum or iridium plug would be insanely expensive. even on single spot plugs the prices are $20 higher than standard copper core plugs, 4 points would be roughly $85 per plug but they should in theory outlast the engine.

standard plugs expose a larger pocket for combustion gases to flow backward and increase detonation risk. plug reach is very important to check especially with traditional plugs, use an old rotor housing to verify their placement.


the fact that your trailing plug is obscured and protected but took the damage tells me you more than likely were running into high levels of detonation, so you should double check your 2 step before even attempting to use it again. rotaries are probably the least focus oriented platform where standalones are concerned, so their ignition cut may not be treating it as a dual stage ignition system that it should be treated as, run more ignition retard than you think is necessary until you iron it out and be sure the retard affects all channels equally or just don't use it.

 

The retard should be affecting all channels. However I'm just going to turn it off.

I'm just hoping the motor doesnt bring along problems sooner/later from swalowing an insulator.

I ordered some new high end ngk race plugs r7420-11's.

Thanks for the input.

 

Bump that idle. That's low for a large street port. I find they idle more comfortable around 900-950.

 

I have a med-large street port, I like the 700-750 idle, only for lumpy sound it makes...


J.

 

The lower the idle the more wear you will get on your sideseals on a large streetport as there is more time for the leading seal to drop into the port.

But it sounds so good!