breathegood

This is not something I've heard or read about until recently.

1) What is it exactly? I have an idea but would like an explanation.

2) What are the symptoms? My car just looses all it's umph at WOT above ~5000 rpm (boosting at 7psi). When I had it at the dyno, it was running super rich,less than 10.1AFR. Is it possible I'm getting the rich reading because the spark is being blown out and unburned fuel is being released downstream, or am I loosing power simplybecause I'm running so rich and need to adjust my tune? FWIW I'm not getting any DTC codes.

3) Is there an easy test to diagnose blowout?

3) What is the most common solution to spark blowout? I assume it will have to do with the heat range and gap of the spark plug.....maybe using a cooler plug and smaller gap. I'm not exactly looking forward to changing the plugs on this car, but it will have to be done sometime, probably better to do it while it has less than 10k on the ticker than wait until they are good an siesed into the head.

zkiller

Spark blow out occurs when your cylinder pressures are high enough to blow out the spark on your spark plug. Spark blow out results in unburned fuel in the combustion chamber. I was getting it at only 8 PSI so you could be getting it at 7 PSI. Your A/F sounds way too rich.
It will happen at instant onset of boost. So for example, when I was rolling at 20 MPH and I floor my car it will kick in to 1st and go to like 11-12 PSI boost instantly. This is where I would get spark blow-out. It would sound like backfiring in the exhaust, from the unburnt fuel. Pop pop pop in the exhaust is what you will hear. Engine will hesiate between pops.
It sounds exactly like you are hitting the rev limiter. You cant miss it if you are getting it.
Solutions:
1) HT0 plugs gapped down to between.032 -.028
This will solve most spark blow-out but not always.

2) High output COPs.
This will definately resolve any issues along with HT0 plugs gapped down.

breathegood

Thanks. That's what I wanted to know. Based on your explanation, I don't think I'm experiencing spark blowout. Just an ubber rich tune. I'm not hearing the backfiring (I assume this is from the unburned fuel igniting in the exhaust manifold), it just feels like it's stalling out at ~5000. I get full boost by 4000, so it definately isn't occuringat the onset of boost. It only happens as I get towards the top of the RPM range.

zkiller

You probably need your car dyno tuned - that is all.

breathegood

The dyno op said he'd like to see the AFR lean enough toshow up onhis graph before he started tuning. LOL! Even as fat as it was, it still pulled 424/453.

mygt500

If the A/f is that pig rich it is the tune and needs to be adjusted.....let us know what happens with the tune and the numbers after!

hypersurf1

Sounds like spark blow out. I was getting it at after 4500 rpm and i still dynoed 420rwhp. After some HT0 plugs gapped at .32 i dynoed 499rwhp.

breathegood

Now I'm getting mixed answers. I've been progressively leaning out the tune using my Predator, and the problem doesn't seem to be going away, but it's possible I haven't leaned it out enough yet. If I weren't so fricken busy right now, I would just shorten the gap on the factory plugs as a test. If they are new and aren't ceised into the head, how long should a plug swap take? Intuitively to me, it seems that spark blowout would cause the AFR to show rich conditions.

Simon1

Tell me you don't have the factory plugs in? You need to invest some $$ in HTOs if you haven't already.

There is a special gapping tool you can buy for $20 or so and you will need a wire gap checker.

It's not if, but when, those stockers will turn in glow plugs and break off into the cylinder putting a nice window through your piston.

I beleive thecorrect gapping for 8-10 psi is.032-.034. That and a real tune will solve your issue.

Did you do the CMCV yet?

zkiller

Don W has been running HT1 on his supercharged car forever never a problem, just needs to be gapped right. In fact he said his car did not run on HT0 plugs very well. You only need the colder pugs if you are getting spark blow-out. If you are not , then installing colder pugs could cause them to foul easily. Spark blow-out pops in the exhaust and causes hesitation too. I would see if gapping the HT1s fixes the problem. If not buy a set of HT0 and gap them to .028 to solve the issue.
Brenspeed can send you the plugs pre-gapped if you need them.