Hi!

Pecurliar problem i stumbled uppon with my newly built FD.

Vital mods around this problem:
Apexi pfc
AEZknights solenoid kit and new hoses all round
full 3" exhaust, no cat
BNR stage 3s seq
Removed igniter, pulled wires from igniter-contact to relay. 12V direct feed to coils via relay
4 ls2 yukon coils with built in igniter, 10mm magnecor wires
new NGK 9s all round
AEM water injection (progressive, set low boost at 2 and high boost at 10) medium nozzle for that power level
37 psi fuel pressure and a walboro 400 pump, brand new
550/1600s

running a rich cruise map, stock boost. 13s idle AF and 11s when flooring it.

I was to map the car up to 21PSI later this year, when i stumbled uppon this ignition "problem". I call it a "problem" cause, its coming and going...

When flooring it WITH water injection on, when turbo 2 kicks in, and im climbing up to 65-7000ish rpm, the engine has a tiiny sputter, you can hear it from the exhaust, like its not firing as it should, and you can feel the power level drop slightly when it does the sputter..

Turned off the water injection and the problem goes away 99% of the time, except on a rare cold occation in 3rd and 4th gear on WOT....

I cant figure out what causes this.

I KNOW the yukon coils arent up there with the mercury coils(super low saturation time), but im running stock boost and direct 12V feed, it should be MORE than enough to fire the mixture...?

Is the problem maybe caused by the car wanting to boost more than 10 psi, and being cut by the ECU?
ignition split or similar off?

What else can cause the problem? I cant see the value in tuning a car that sputters on stock levels, and waste that money....

halp pleez?

regards
Øyvind

 

How do your plugs look?
how new/mileage on the plugs?

You might need to go to heat range 10 based on your mods.

 

havent pulled em, but they are brand new,have maybe 150 miles on em?

 

Are you sure its not going overly rich when you are experiencing the problem? When you say it happens with the water off when its cold, do you mean cold ambient air temps? Is your AIT sensor downstream of the AI nozzle?

 

Whats your brand of wideband o2 sensor?

Have you compared your read outs to another o2 sensor?

I have/had the same problem on my setup. I'm rnning around 20psi on a 67mm w/ 10's plugs and hks twin power and 600cc water.

Anything under 11.2 and i breakup like nuts. Water and no water. 11.5 and it spins tires top of third gear!

I'm betting that my o2 sensor is reading leaner then the car is actually running by ~1 full point.

 

I have had a sneaking suspision about the car going overly rich.
I had a chat with my girlfriend about this, and she remembers seeing 10.4-10.5ish AF levels when i floored it, so that may be way too rich of a mixture to ignite properly?

The cold-issue... may be a faulty statement by me, so lets ditch that from the "evidence list" as of now


My AIT sensor is in stock placing underneath the UIM, while the water nozzle is fitted in the greddy elbow.

 

I have the Innovate LM-1, and i know they are abit weak when it comes to rotary(heat handling), so ive fitted it all the way on the two inches of the midpipe to remove the heat problem, at a 90+ degree angle from the vertical, so i dont collect water vapor in it. Its brand new as well.

I have not compared it to another o2 sensor, but i calibrated it in free air as the manual said, and i have it hooked up to my datalogit.

DriftDreamzSS suggested it running stupid rich, and your previous problem sugests the same.

Does anyone else see any problems it might be?

 

The Yukon coils are fine; they are very capable--just don't set the dwell too long.

You said NGK 9's--I'm assuming the stock BUR type plug. Problem with those is that the gap is really wide, which can be a big problem for a cold plug. I would suggest trying plugs that can be gapped down to .025--.030". Get some of the inexpensive autolites or ngks of the conventional (short) variety (e.g., Autolite 3933's iirc) and give them a try. Of course, you can buy the expensive plugs that many like, but it's not a necessity.

Oh, and get a non-resistor plug if your setup will tolerate it. No point in losing half your energy heating a resistor if you don't have to; as long as you have some sort of suppression wire you should be ok.

The problem with cold plugs, big gaps and high cylinder pressure is that the plug will want to fire across the insulator surface rather than the gap. The surface discharge will often be the path of least resistance on a cold plug with a short insulator nose, even if the plug is new. This is not a fouling problem per se; however, the effect is exasperated by rich mixtures and/or AI.

 

With the placement of your ai nozzle and ait sensor the water hitting it will make it read colder, so if your tune is setup to richen up the afr's for colder ait's that could be the cause. I run bur9eq's x4 with a 35r @17psi and 315cc's of water and get breakup if the afr's go below 11.0:1