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 simply because 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.
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.
< Message edited by zkiller -- 5/9/2008 8:36:19 AM >
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 occuring at the onset of boost. It only happens as I get towards the top of the RPM range.
The dyno op said he'd like to see the AFR lean enough to show up on his graph before he started tuning. LOL! Even as fat as it was, it still pulled 424/453.
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.
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quote:
ORIGINAL: 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.
Tell me you don't have the factory plugs in? You need to invest some $$ in HTOs if you haven't already.
There is a special gapping tool you can buy for $20 or so and you will need a wire gap checker.
It's not if, but when, those stockers will turn in glow plugs and break off into the cylinder putting a nice window through your piston.
I beleive the correct gapping for 8-10 psi is .032-.034. That and a real tune will solve your issue.
Don W has been running HT1 on his supercharged car forever never a problem, just needs to be gapped right. In fact he said his car did not run on HT0 plugs very well. You only need the colder pugs if you are getting spark blow-out. If you are not , then installing colder pugs could cause them to foul easily. Spark blow-out pops in the exhaust and causes hesitation too. I would see if gapping the HT1s fixes the problem. If not buy a set of HT0 and gap them to .028 to solve the issue. Brenspeed can send you the plugs pre-gapped if you need them.
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I just Emailed E3 spark plugs, asking them if they plan to produce a plug for our V8s. I'll let you know what they say. I'd love to have the option of an E3 plug for our cars.
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Now I'm getting mixed answers. I've been progressively leaning out the tune using my Predator, and the problem doesn't seem to be going away, but it's possible I haven't leaned it out enough yet. If I weren't so fricken busy right now, I would just shorten the gap on the factory plugs as a test. If they are new and aren't ceised into the head, how long should a plug swap take? Intuitively to me, it seems that spark blowout would cause the AFR to show rich conditions.
Tell me you don't have the factory plugs in? You need to invest some $$ 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 the correct gapping for 8-10 psi is .032-.034. That and a real tune will solve your issue.
Did you do the CMCV yet?
The car only has 5200 miles on it and only ~2100 of those are blown, so no, I haven't changed the factroy plugs yet. I went with cooler plugs on my S/C Tacoma to help alleviate some spark knock that I was having, and found that the truck runs better with the hotter plugs and more timing retard, so I'm not entirely convinced that swapping to cooler plugs is a universally good idea on all F/I applications....What I learned with tuning my truck for forced inductions is that what works well for the masses at sea level, doen't necessarily apply at 6200'. If I go to the trouble of pulling the plugs, I would like to at least try the HTO's, but it seems like an expensive, and rather arduous proposition for something that ought to be cheap, quick, and easy.
The car only has 5200 miles on it and only ~2100 of those are blown, so no, I haven't changed the factroy plugs yet. I went with cooler plugs on my S/C Tacoma to help alleviate some spark knock that I was having, and found that the truck runs better with the hotter plugs and more timing retard, so I'm not entirely convinced that swapping to cooler plugs is a universally good idea on all F/I applications....What I learned with tuning my truck for forced inductions is that what works well for the masses at sea level, doen't necessarily apply at 6200'. If I go to the trouble of pulling the plugs, I would like to at least try the HTO's, but it seems like an expensive, and rather arduous proposition for something that ought to be cheap, quick, and easy.
No, I haven't done the CMCV yet either.
With only 5200 miles your plugs should come out with no issues. I've never even done the tsb for removing the plugs. I just unscrew them.
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Posts: 1543
Joined: 12/19/2006 From: Northern California Status: offline
quote:
ORIGINAL: 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.
The heat range of the plug has nothing to do with the spark gap. These are two different issues. The same heat will be produced in both applications, stock or colder plug. The difference is the colder plug will be able to disipate heat better and/or faster than the stock plug, which let's it maintain the proper operating range. Whatever power adder you have on your car, with increases in the 100 hp range it has been recomended by every source I have ever read, spoken to or listen to, to replace the plug with a cooler heat range. If your friend had issues with the HTOs in his car then he probably had a bad one in the bunch or they weren't gapped properly.
I'm sure people can get away with running them for a while with their power adder, but why would you risk it knowing they aren't made to work in the application they are being used in? A $100 invested in some security just seems like the right thing to do.
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Spark Blowout? - 
