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Racing in the rain - cylinder wash down?


tneker
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I have our engine tore down for the off season because after the last race we had some pretty high leak down rates on 3 of the 4 cylinders.  The leakage was past the rings as air flow could be heard in the valve cover vents.

 

Upon initial inspection nothing looked too bad on the cylinder walls or rings with just visual inspection.  While I wished for a better diagnosis I figured with de-glazed cylinder walls and fresh rings we would probably be back in business.

 

For whatever reason a thought jumped in my head that I couldn't reconcile myself and I thought I would ask the champcar community to help put this to rest in my head.

 

This probably about the weirdest thing I think I have ever suggested and I suspect you are all about to tell me so.

 

Our last race was Road America in Oct and the whole second day was essentially in the rain.  Our intake air filter sits in the headlight pocket and is certainly pulling in some moisture.  Is there any chance that the rain ingestion resulted in cylinder wash down?  I have only heard of way too much fuel causing cylinder wash down.

 

The little bit of data that made me potentially embarrass myself in front of my champcar peers is that the leakage rates essentially were the worst on cylinders closest to the throttle body and got better as they got farther away.

 

Just doesn't make sense to me as I would assume any moisture is just consumed by the combustion process, right?

 

 

 

 

 

  

 

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1 hour ago, tneker said:

I have our engine tore down for the off season because after the last race we had some pretty high leak down rates on 3 of the 4 cylinders.  The leakage was past the rings as air flow could be heard in the valve cover vents.

 

Upon initial inspection nothing looked too bad on the cylinder walls or rings with just visual inspection.  While I wished for a better diagnosis I figured with de-glazed cylinder walls and fresh rings we would probably be back in business.

 

For whatever reason a thought jumped in my head that I couldn't reconcile myself and I thought I would ask the champcar community to help put this to rest in my head.

 

This probably about the weirdest thing I think I have ever suggested and I suspect you are all about to tell me so.

 

Our last race was Road America in Oct and the whole second day was essentially in the rain.  Our intake air filter sits in the headlight pocket and is certainly pulling in some moisture.  Is there any chance that the rain ingestion resulted in cylinder wash down?  I have only heard of way too much fuel causing cylinder wash down.

 

The little bit of data that made me potentially embarrass myself in front of my champcar peers is that the leakage rates essentially were the worst on cylinders closest to the throttle body and got better as they got farther away.

 

Just doesn't make sense to me as I would assume any moisture is just consumed by the combustion process, right

We had so much water coming in at the Ridge that it only took about 3 laps to completely soak our air filter, then mess up the MAF readings and go extremely lean. Neither affected the leak-down readings.

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Here is a good article that would suggest that any water that made it's way to the combustion chamber would evaporate before detention from the heat.  Makes perfect sense and leaves me scratching my head to the leak down issues.

 

 http://blogs.discovermagazine.com/d-brief/2016/09/06/engine-spray-water-coolant-efficient/#.WkK8zd_tx3g

 

 

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18 hours ago, tneker said:

I have our engine tore down for the off season because after the last race we had some pretty high leak down rates on 3 of the 4 cylinders.  The leakage was past the rings as air flow could be heard in the valve cover vents.

 

Upon initial inspection nothing looked too bad on the cylinder walls or rings with just visual inspection.  While I wished for a better diagnosis I figured with de-glazed cylinder walls and fresh rings we would probably be back in business.

 

For whatever reason a thought jumped in my head that I couldn't reconcile myself and I thought I would ask the champcar community to help put this to rest in my head.

 

This probably about the weirdest thing I think I have ever suggested and I suspect you are all about to tell me so.

 

Our last race was Road America in Oct and the whole second day was essentially in the rain.  Our intake air filter sits in the headlight pocket and is certainly pulling in some moisture.  Is there any chance that the rain ingestion resulted in cylinder wash down?  I have only heard of way too much fuel causing cylinder wash down.

 

The little bit of data that made me potentially embarrass myself in front of my champcar peers is that the leakage rates essentially were the worst on cylinders closest to the throttle body and got better as they got farther away.

 

Just doesn't make sense to me as I would assume any moisture is just consumed by the combustion process, right?

 

 

 

 

 

  

 

If you have a "fresh air" system you need to block it in the rain especially heavy rain.  BUT I would think that would cause hydro-lock and not a wash down... I would think you'd develop a miss. was there water in your oil?

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On 12/28/2017 at 11:59 AM, rod rammage said:

We spray water into the intake to clean out carbon. IF you were ingesting that much water, your cylinders, piston tops, spark plug tips and valves should be pretty clean and free of carbon. I doubt your symptoms were the result of ingesting water. Were your piston tops shiny and clean?

 

The piston tops were in fact full of carbon as we have been running a bit rich at times.  Perhaps the wash down was in fact from too much fuel...

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My understanding off washdown is because gasoline is a solvent and will wash away the oil clinging on the hot cylinder walls. The water would be repelled. You might want to have oil analysis done to see if any fuel is showing up in the oil. Do any of the Pistons show signs of detonation? Is there any ring drag or chatter on any cylinders? Who gapped the rings?

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13 minutes ago, tneker said:

 

 

2nd Gen OEM with Syked Tuning Software.  We target about 12.8:1 A/F at WOT.

My limited experience is 12.8 will not wash down a cylinder as many cars tune for 10-11 under boost or for temp control. This also assumes that 12.8 is on all cylinders and there are rich and lean cylinders. 

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3 hours ago, wd6681 said:

My understanding off washdown is because gasoline is a solvent and will wash away the oil clinging on the hot cylinder walls. The water would be repelled. You might want to have oil analysis done to see if any fuel is showing up in the oil. Do any of the Pistons show signs of detonation? Is there any ring drag or chatter on any cylinders? Who gapped the rings?

 

Lot's of good  questions so I figured worth providing more background.

 

The engine build in question had 40 to 50 race hours on it and we had planned to tear down in off season regardless.  Prior to the teardown I checked cranking cylinder pressure and leak down rates.  Cranking pressures had been quite good after previous races, but had fallen after this last race.  The leakage rate test confirmed ring blow by.

 

When this build was fresh, our tune was a bit richer (mid 11 to low 12's) than the 12.8 @ WOT we targeted for this race.  The carbon build up on the pistons I believe is likely a remnant of the previously richer tunes.  We may still be too rich at idle. We had an oil analysis done previously that confirmed a little gas in the oil, enough to suggest we were too rich, but not enough to suggest we had significant fuel issues.

 

I did the previous engine build and am confident in the ring gaps etc.  The reason I suspected we may have suffered from cylinder wash down was because the cylinder walls do not look too bad, there were no cracked rings, so presumably the rings wore enough to lose some sealing without too much collateral damage on the cylinder walls. 

 

Not sure how many race hours folks are getting out of build, but I assumed we would get more out of the rings than the bearings.  After 40 to 50 hours our bearings look great, our cylinder compression, not so much.

 

 

Edited by tneker
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I personally would not be satisfied with 40-50 hours. If there was that much carbon, it is possible you might have 'stuck' a ring without it dragging on the cylinder. What brand rings are you running? I am with Mopar, guessing they may wonder about some detonation in the tune.

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The engine that showed gasoline in the oil, was it the same block? Was the block bored (more than a 10th) since then? Your cylinders may not be straight. Even if 11:1 sounds rich, I don't think the fuel volume based on your power is enough to produce considerable fuel in the oil.

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I personally don't have a good experience with the syke stuff. The stuff we have received from him has not been good at all. We lost a motor due to the tune in our cruiser and the neon we had to do a couple revisions and we were still not happy. 

 

For or whatever reason he advances the timing to some god awful amount. There is only so much timing you can put in a motor before the is diminished returns. To give an idea. We headed to the dyno with 91oct. no ethanol fuel. We saw 6-7 degrees of knock retard. We then drained the tank and filled the tank to the highest octane we can get in Ontario 94oct. We still saw 2-3 degrees of retard. So we ended up sending it back with the dyno results. We then recieved back a revised version. It was better but it still ran rich. So we ended up scrapping the whole product and went back to a mopar pcm until we can get our standalone pcm up and running.

 

 

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10 hours ago, tneker said:

Not sure how many race hours folks are getting out of build, but I assumed we would get more out of the rings than the bearings.  After 40 to 50 hours our bearings look great, our cylinder compression, not so much.

GM 3500 V6, engine had 80,000 miles on it, went through it but reused the original rings and bearings. Initial leakdown after a quick break-in was 4%. Dyno tuned after the mail order tune would barely run the engine. WOT was set to13.6-13.8:1 AFR.

 

After 80+ hours of racing and a few extremely lean incidents, the leakdown was still 4%. Valve seals and timing chain was due to freshening but otherwise good.

Edited by mender
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Tneker,

 

The only ring failures i have seen on the 2.0\2.4 engines were from detonation. I eroded some of the piston edge which quickly allowed the rings to get soo hot they were annealed and consumed. This wasn't visually obvious until i tore the motor down and cleaned it up enough to notice the piston crown edge was rolled over. Was the day in question alot colder than normal? Temp sensor or map scaling with temp off? Did the motor overheat (and detonate from high cylinder temp)?

 

The 2.4 came in dished (early) and "ski ramp" (later) designs. The ski ramp helps with mixing and part throttle efficiency, but i would guess that it has different timing requirements than the dished style. 

 

Either way the neon head is pretty efficient, and doesnt require a ton of extra fuel to run well. Similarly it shouldnt need or gain much from excess timing. I think mopar pcm settings with fuel pulled out up top (it runs fat above 5000 rpm) would be a good starting point.

 

If doing a rebuild, get high tension "thicker" rings if that is an option for the piston you select. Some of the dodge pistons used new style thin rings which you can damage during install.

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