screaminz28

iTrader: (1)

I think those A2 heads make a BIIIIG difference - just comparing to all the swapped J series guys out there making 400 - 500 whp vs. the TL crowd popping motors left and right. Then again, most of the swapped setups are also running a standalone ecu. Something to think about at least.

UTAH TSX

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

FamilyGuy

How do the heads make a diff if exhaust flow is about the same?

thisaznboi88

iTrader: (7)

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

screaminz28

iTrader: (1)

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

yungone501

iTrader: (4)

AGREED.

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.

FamilyGuy

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.

gerzand

iTrader: (3)

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

UTAH TSX

I'm going to start a new thread on detonation so we clog up madogs thread

6spd-GERCO

Pre-ignition or detonation?

thisaznboi88

iTrader: (7)

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

screaminz28

iTrader: (1)

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?

6spd-GERCO

Yes, I know the difference, just looking for clarification. Engines can take certain amounts of knock/detonation but any motor will meet a quick end with pre-ignition. But as you have pointed out pre-ignition can result from detonation. Need to look at the damage.

thisaznboi88

iTrader: (7)

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

maddogtheta

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/

Pghpizzaman

good decision. you have wasted a ton of money on trying to get this to work. i feel for ya buddy. really sucks