Rear mount turbo - Type S
#321
Burning Brakes
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This is crazy guys. I never (personally) had a bit of knock on 93 octane, without meth, and at 15 degrees of timing on a stock j35a8 (j32a2 headswapped) 11:1CR centrifugal supercharged motor. I've also never had knock when or sleeved/built as I sit now @ 10:1CR. With E85 I could push it to 18 degrees, still without a sign of knock. Also never had knock on a 250shot of nitrous on a stock j35a8 bottom end.
To clarify, i'm not saying a stock bottom end will last, but just for sake of comparison regarding occurrences of knock.
The one difference here is that I haven't run a turbo yet on a J...but many 1st gen J guys have without any issues increasing timing.
Another thought - Did you check piston to deck height? Maybe you encountered the original problem I did with piston protrusion on my first set of custom Wiseco pistons. I had protrusion of .008! I discoved this during assembly and corrected it. Many wont notice it unless you're looking for it. Maybe the piston is slapping the head with rod grow? Rod grow can get pretty crazy in itself.
To clarify, i'm not saying a stock bottom end will last, but just for sake of comparison regarding occurrences of knock.
The one difference here is that I haven't run a turbo yet on a J...but many 1st gen J guys have without any issues increasing timing.
Another thought - Did you check piston to deck height? Maybe you encountered the original problem I did with piston protrusion on my first set of custom Wiseco pistons. I had protrusion of .008! I discoved this during assembly and corrected it. Many wont notice it unless you're looking for it. Maybe the piston is slapping the head with rod grow? Rod grow can get pretty crazy in itself.
#322
Our deck to piston was .018, and we have 91 gas with ethenol bad gas. with a mix of race fuel zero knock even with more boost
#323
Three Wheelin'
How do the heads make a diff if exhaust flow is about the same?
#324
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Hot exhaust gas goes back up one of the ports. BOOM pre-ignition especially when you have a shit load of back pressure. All it has to do is cross 2-3 inches instead of 5 ft of piping
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#325
Burning Brakes
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You have to consider flow even outside of the port as well. Think about it like we have a bolted on crap shorty header.
You can improve a cylinder head flow test dramatically on the exhaust by adding a pipe to the exhaust port instead of just using the port itself.
I don't think the A3 heads are terrible by any means, but in no way as optimal as an A2 that could use a large diameter individual pipe.
The size of an exhaust pipe becomes less and less important the further from the head, so the opposite is true. Personally, I think a 3in PCD would be a BIG power gain - but no one has done one.
Richie if you're out there - I have a set of RV6 PCDs - if you want to custom mod mine to a 3in pipe for free as a test - I'll take them off and ship them too you. :-D
You can improve a cylinder head flow test dramatically on the exhaust by adding a pipe to the exhaust port instead of just using the port itself.
I don't think the A3 heads are terrible by any means, but in no way as optimal as an A2 that could use a large diameter individual pipe.
The size of an exhaust pipe becomes less and less important the further from the head, so the opposite is true. Personally, I think a 3in PCD would be a BIG power gain - but no one has done one.
Richie if you're out there - I have a set of RV6 PCDs - if you want to custom mod mine to a 3in pipe for free as a test - I'll take them off and ship them too you. :-D
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#326
J-series addict
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Then factor in increased overlap on the high speed cam profile and say hello to knock. Even on my current NA build I've been seeing very light knock due to exhaust restriction (and head design) and finally said to hell with it and ordered some PCD's because the stock precats can't flow much more as I'm running on the edge with my current tune. I've pretty much freed up the intake side but I'm beginning to see how bad these single port heads are when EGT's and combustion temps begin to increase due to their effect on the engine.
Less intake/exhaust restriction is by far the best way to combat the head design and those running precats should remove them before edging out on ignition advance. I would say I'm pretty much clear on intake restrictions. Here's my setup now with a large plenum design intake, large TB, and 3.5" intake tubing down into a high flow filter.
#327
Three Wheelin'
Well, short of increasing valve size most we can do is match exhaust pipe size to the exhaust port size, and remove as much restriction in the flow as possible, no?
So single vs multi port exhaust comes down to the head design itself, and there's nothing we can do beyond freeing up the exhaust system (air flow restrictions) other than replacing the head itself to a multi port design like an A2 head then?
Honda went to a single port for what reason, lower emissions? Tighter / smaller overall packaging (size)?
That's the only thing I've always wished we had, traditional multi port exhaust heads. But it's so expensive to swap in an A2 head onto a j35a8 with a proper header / exhaust system, and do we even know what the power gains would be on a FBO setup? Probably not worth the $ / hp ratio? Sounds like this would be more of an engine safety benefit for forced induction applications than power gains in NA form.
So single vs multi port exhaust comes down to the head design itself, and there's nothing we can do beyond freeing up the exhaust system (air flow restrictions) other than replacing the head itself to a multi port design like an A2 head then?
Honda went to a single port for what reason, lower emissions? Tighter / smaller overall packaging (size)?
That's the only thing I've always wished we had, traditional multi port exhaust heads. But it's so expensive to swap in an A2 head onto a j35a8 with a proper header / exhaust system, and do we even know what the power gains would be on a FBO setup? Probably not worth the $ / hp ratio? Sounds like this would be more of an engine safety benefit for forced induction applications than power gains in NA form.
#328
Three Wheelin'
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Just look at what the k24z guys are doing; swapping 1st gen K heads to get rid of single port (cast) exhaust side. A j32a2 headswap is worth a few horsepower for a J when stock, perhaps more when boosted (and is even more beneficial in the kseries due to cam design offerings as well as lobe design limitations too in the 2G heads) but I do agree its a better measure for safety when under FI
Last edited by gerzand; 06-11-2015 at 10:38 AM.
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#329
Just look at what the k24z guys are doing; swapping 1st gen K heads to get rid of single port (cast) exhaust side. A j32a2 headswap is worth a few horsepower for a J when stock, perhaps more when boosted (and is even more beneficial in the kseries due to cam design offerings as well as lobe design limitations too in the 2G heads) but I do agree its a better measure for safety when under FI
#331
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Pre-ignition
"Pre-ignition" is another abnormal combustion event that is often confused with detonation, but in fact is completely different. Pre-ignition is the ignition of the air-fuel charge prior to the spark plug firing. Anytime something causes the mixture in the chamber to ignite before the spark plugs fire, it is classified as pre-ignition. The ignition source can be an overheated spark plug tip, carbon or lead deposits in the combustion chamber, or (rarely) a burned exhaust valve-any of these things can act as a glow plug to ignite the charge prematurely.
Detonation-induced pre-ignition
Although detonation and pre-ignition are two completely different phenomena, it is possible for heavy detonation to induce pre-ignition. If the engine is operating in heavy detonation for a significant period of time, the excessive temperatures and pressure spikes (which disturb the usual protective boundary layer) can cause spark plug electrodes and other things in the combustion chamber to overheat to the point where they start to glow red hot. At that point, the glowing item can cause pre-ignition and rapid destruction of the cylinder. Upon teardown, forensic analysis would reveal the tell-tale signs of both detonation and pre-ignition damage, although it's the pre-ignition that ultimately did the engine in.
In a different article, we'll look more closely at the normal combustion event, and explore how our use of the engine controls - throttle, mixture and prop - affect what happens inside the cylinder.
citation :
https://www.savvyanalysis.com/articl...d-pre-ignition
"Pre-ignition" is another abnormal combustion event that is often confused with detonation, but in fact is completely different. Pre-ignition is the ignition of the air-fuel charge prior to the spark plug firing. Anytime something causes the mixture in the chamber to ignite before the spark plugs fire, it is classified as pre-ignition. The ignition source can be an overheated spark plug tip, carbon or lead deposits in the combustion chamber, or (rarely) a burned exhaust valve-any of these things can act as a glow plug to ignite the charge prematurely.
Detonation-induced pre-ignition
Although detonation and pre-ignition are two completely different phenomena, it is possible for heavy detonation to induce pre-ignition. If the engine is operating in heavy detonation for a significant period of time, the excessive temperatures and pressure spikes (which disturb the usual protective boundary layer) can cause spark plug electrodes and other things in the combustion chamber to overheat to the point where they start to glow red hot. At that point, the glowing item can cause pre-ignition and rapid destruction of the cylinder. Upon teardown, forensic analysis would reveal the tell-tale signs of both detonation and pre-ignition damage, although it's the pre-ignition that ultimately did the engine in.
In a different article, we'll look more closely at the normal combustion event, and explore how our use of the engine controls - throttle, mixture and prop - affect what happens inside the cylinder.
citation :
https://www.savvyanalysis.com/articl...d-pre-ignition
#332
Burning Brakes
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I think this is a key question and needs better understanding.
From what maddog describes, I don't think detonation killed his motor this time, but rather pre-ignition. Could it have been detonation induced pre-ignition - possibly.
My WRX would experience detonation (also known as spark knock) periodically, but it never melted a piston. I eventually spun a bearing (I think Mobil 1 caused it) and when we tore it open, we could see excessive bearing wear from repeated spark knock.
These melted piston issues - I wonder if they could be mitigated by just running richer (not ideal for power, but if it saves the motor?). Didn't Libert run like 10:1 on his back in the day?
From what maddog describes, I don't think detonation killed his motor this time, but rather pre-ignition. Could it have been detonation induced pre-ignition - possibly.
My WRX would experience detonation (also known as spark knock) periodically, but it never melted a piston. I eventually spun a bearing (I think Mobil 1 caused it) and when we tore it open, we could see excessive bearing wear from repeated spark knock.
These melted piston issues - I wonder if they could be mitigated by just running richer (not ideal for power, but if it saves the motor?). Didn't Libert run like 10:1 on his back in the day?
#333
Burning Brakes
Pre-ignition
"Pre-ignition" is another abnormal combustion event that is often confused with detonation, but in fact is completely different. Pre-ignition is the ignition of the air-fuel charge prior to the spark plug firing. Anytime something causes the mixture in the chamber to ignite before the spark plugs fire, it is classified as pre-ignition. The ignition source can be an overheated spark plug tip, carbon or lead deposits in the combustion chamber, or (rarely) a burned exhaust valve-any of these things can act as a glow plug to ignite the charge prematurely.
Detonation-induced pre-ignition
Although detonation and pre-ignition are two completely different phenomena, it is possible for heavy detonation to induce pre-ignition. If the engine is operating in heavy detonation for a significant period of time, the excessive temperatures and pressure spikes (which disturb the usual protective boundary layer) can cause spark plug electrodes and other things in the combustion chamber to overheat to the point where they start to glow red hot. At that point, the glowing item can cause pre-ignition and rapid destruction of the cylinder. Upon teardown, forensic analysis would reveal the tell-tale signs of both detonation and pre-ignition damage, although it's the pre-ignition that ultimately did the engine in.
In a different article, we'll look more closely at the normal combustion event, and explore how our use of the engine controls - throttle, mixture and prop - affect what happens inside the cylinder.
citation :
https://www.savvyanalysis.com/articl...d-pre-ignition
"Pre-ignition" is another abnormal combustion event that is often confused with detonation, but in fact is completely different. Pre-ignition is the ignition of the air-fuel charge prior to the spark plug firing. Anytime something causes the mixture in the chamber to ignite before the spark plugs fire, it is classified as pre-ignition. The ignition source can be an overheated spark plug tip, carbon or lead deposits in the combustion chamber, or (rarely) a burned exhaust valve-any of these things can act as a glow plug to ignite the charge prematurely.
Detonation-induced pre-ignition
Although detonation and pre-ignition are two completely different phenomena, it is possible for heavy detonation to induce pre-ignition. If the engine is operating in heavy detonation for a significant period of time, the excessive temperatures and pressure spikes (which disturb the usual protective boundary layer) can cause spark plug electrodes and other things in the combustion chamber to overheat to the point where they start to glow red hot. At that point, the glowing item can cause pre-ignition and rapid destruction of the cylinder. Upon teardown, forensic analysis would reveal the tell-tale signs of both detonation and pre-ignition damage, although it's the pre-ignition that ultimately did the engine in.
In a different article, we'll look more closely at the normal combustion event, and explore how our use of the engine controls - throttle, mixture and prop - affect what happens inside the cylinder.
citation :
https://www.savvyanalysis.com/articl...d-pre-ignition
#334
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Need to see the Damage and the Datalog. I want to see what the car was doing right before timing was pulled. That would help determine if it was fuel induced detonation or EGT induced
#335
Racer
Thread Starter
Pics of damaged pistons
Here's some pics of my damaged pistons from the last engine failure.
I'm also selling my turbo kit on the black market and Pauter rods on the black market.
https://acurazine.com/forums/car-par...-3g-tl-933390/
https://acurazine.com/forums/car-par...5-3-5l-933392/
I'm also selling my turbo kit on the black market and Pauter rods on the black market.
https://acurazine.com/forums/car-par...-3g-tl-933390/
https://acurazine.com/forums/car-par...5-3-5l-933392/
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