Lost Compression in cyl 7&8 Mystery Solved!

[pro 5.0]

https://www.facebook.com/palmbeachdyno/videos/2014298802228993/

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[Crackerjack17]

https://www.facebook.com/palmbeachdyno/videos/2014298802228993/

Hmmm. I don't have the ford performance one. And he mentioned welded? Also, in that video it's hard to tell, but it looked kinda rough. Weird. The mmr one is perfect. Machined. I'll throw up some pictures. But honestly, I probably don't need it. The factory one is just as thick, so I'm not sure what difference it can even make.

 

[Gurjit]

Thanks alot for posting this, good info here and cool to see the pictures.

What were the compression numbers?




@ProChargerTECH , it's my understanding that low timing makes more heat and higher timing helps evacuate the heat out of the cylinder. Is this why you used that example? High boost and high timing would be slightly better, correct?



IMO, yes it will help. This is the main reason I went with meth injection, lowers cylinder pressures and temps, helps avoid knock/detonation, and as said above I believe it also helps lower temps by allowing more timing. But again, it will only help, with a long enough pull and enough heat even meth or E85 probably wont save a stock motor. This is why I'm holding off of 1/2 mi racing even with the methanol.

Not done tuning my meth yet, but according to the calculated Cat temp sensor I dropped from 1800F to 1600F exhaust temp on WOT pulls. Which indirectly means less heat in the cylinders and on the rings.

IMO, the drop in exhaust out temps is related to the timing advancing under WOT to allow more expansion of the gas/air mixture in the cylinder, when you retard the timing the heat is able to exit the engine @ higher temps because it has spent less time producing power.

 

[pro 5.0]

Hmmm. I don't have the ford performance one. And he mentioned welded? Also, in that video it's hard to tell, but it looked kinda rough. Weird. The mmr one is perfect. Machined. I'll throw up some pictures. But honestly, I probably don't need it. The factory one is just as thick, so I'm not sure what difference it can even make.

Yeah I wasn't sure which brand they had a problem with, when you mentioned you got the billet one it just threw up a red flag in my head lol. The stock ring is stamped steel the billet one should be more rigid hence less flex at high rpm leading to more stable timing in theory.

 

[Plimmer]

Finally a useful thread, tons of great information here.....your loss is our gain...thanks

 

[Dennisn]

It was the ford racing Cj trigger wheel they had issues with not the billit wheels.

 

[ahl395]

1 - 230
2 - 225
3 - 220
4 - 240
5 - 235
6 - 210
7 - 105 - boom
8 - 140 - boom

Thanks for sharing. Was wondering if it was a slight drop or very obvious. Just tested mine and got 205-220 between all of them.

IMO, the drop in exhaust out temps is related to the timing advancing under WOT to allow more expansion of the gas/air mixture in the cylinder, when you retard the timing the heat is able to exit the engine @ higher temps because it has spent less time producing power.

Make sense, although I cant help but think the methanol helps cool it down too. Cars that are run on 100% meth ice up their intake manifold and piping lol.

 

[Crackerjack17]

Yeah I wasn't sure which brand they had a problem with, when you mentioned you got the billet one it just threw up a red flag in my head lol. The stock ring is stamped steel the billet one should be more rigid hence less flex at high rpm leading to more stable timing in theory.

Pics... mmr vs stock one. Obviously mmr is nicer, but not sure if that makes it better. I just can't see the stock one flexing much. And can it be that critical? It's simply a trigger. If it expands under rpm, it gets closer to the sensor! But what do I know.

What looks like cracks on the stock one in the third picture are casting marks.

 

[Crackerjack17]

And... look closer at the top ring. I didn't notice it before, but it looks like a small piece of the face is missing off the ring too. I'll look at it tomorrow, to see if it's only burnt oil on it, but it doesn't look that way.

 

[pro 5.0]

That top ring has flaked apart usually a sign of high heat, as for the trigger wheel I would lay them on top of each other and if the teeth line up on both should be good to go. I personally don't think it's required but you have it so why not use it.

 

[Darthmayxj]

HAHA... I Just did a weekend long track day at Circuit of the Americas with my Whipple car. Second day last session, I got a CEL for cylinder 8 misfires and cank posistion sensor. Multiple laps that had WOT pulls to 150 Plus. Doing my compression test tonight. Could be a fun build!

 

[ahl395]

HAHA... I Just did a weekend long track day at Circuit of the Americas with my Whipple car. Second day last session, I got a CEL for cylinder 8 misfires and cank posistion sensor. Multiple laps that had WOT pulls to 150 Plus. Doing my compression test tonight. Could be a fun build!

Could be a long shot but, try doing a crank relearn? Check your plugs too, I had a misfire one time and freaked out over a blown engine and it ended up being a plug lol.

 

[Darthmayxj]

Could be a long shot but, try doing a crank relearn? Check your plugs too, I had a misfire one time and freaked out over a blown engine and it ended up being a plug lol.

Im gonna do a full look over this weekend. Pull all the plugs and take a look and do the compression check. If it all checks out Im gonna keep on sending it!

I did some quick math.

I did 6 Sessions at 30 minutes each. 180 Minutes. 4 Minutes per lap so 45 LAPS total. Each Lap has 2 Long straits where i did wide open throttle pulls to 130 MPH Plus. So basically 90 HARD pulls over 130 MPH with half of those being to 150 plus.

 

[kcc0521]

That's one thing I love about the procharger. That intercooler is awesome. IIRC, I never saw more than a few degrees above ambient most of the time. Would have to double check the logs for temps near red line though.

You will be surprised when you look at the IAT after a 4th gear pull. It will be around 30 or more above ambient.

 

[Excelerater]

all v8 engines drivers side corners are the most susceptible to detonation
which yours clearly had.
If you can custom tune it take up a extra degree of timing from that corner
would help,maybe two...

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