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I've heard that the imbalance in flow of the stock manifold causes the #6 to run lean. If running 720 injectors would it be beneficial to run, say, an 850 in the #6 position. Of course it'll run at the same duty cycle as the 720's but inject more fuel per cycle to correct the lean condition? Anyone try this or have any feedback? Wanted to know before I invest in an injector I may not need.
Thanks,
--B--
 
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Theory behind this is that, under hard boost, the air violenly hits the back of the stock intake manifold, bounces back and creates air turbulence. Beacuse of the turbulence, from time to time there are differences in actual air quantity, and this can lead to a lean condition and cause detonation/pre-ignition. Commonly affected are cylinders #5 and #6.

The only intake manifold designs to carefully address this (AFAIK) seem to be Bullish Racing, Garage Bomber and Veilside.

I wouldn't experiment with different injectors. Manifold is all you need:

 
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I woul guess Garage Bomber since the radiator cover piece says "Garage Bomb". Just a guess though.

Looks like one sweet engine bay though.
 
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#6 runs hot because the egr transfer/cooler is in the back of the head and the head runs hot back there. The cooling system around the back of the head can't reject enough heat from that area. The intake has little to nothing to do with it. Fill in the hole in the #6 exhaust port and you will not have a problem back there.

Using a larger injector in #6 will have adverse affects since it will run richer all the time in that one cylinder. The ECM will then compensate because that one cylinder will introduce a more oxygen depraved pulse of gases (what the sensor reads) and then lean the overall mix out. The other 5 will run lean. Just like if you have a dead miss in one cylinder, the other plugs will run rich because the dead hole will put lots of oxygen in the exhaust stream. The ECM enrichens what it thinks is a lean mixture until the overall oxygen content is where it wants it, unfortunatly it is too much fuel for the other cylinders.

In open loop, yes you can slightly crutch the problem but closed loop it will make things worse. All the big HP engines (including Ara's) that have engine builders that really have their act together have that port filled.
 
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JZ1 said:
#6 runs hot because the egr transfer/cooler is in the back of the head and the head runs hot back there. The cooling system around the back of the head can't reject enough heat from that area. The intake has little to nothing to do with it. Fill in the hole in the #6 exhaust port and you will not have a problem back there.
EGR cooler opening in the cylinder head is well separated from the #6 combustion chamber. It could potentially damage the valve seal(s) in the head, but could not cause the #6 to run lean. EGR blockoff plates are used by everyone and their grandma, but only Bullish (Ara) and few others that have their act together are running the slanted intake.
 

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MONSTER said:


EGR cooler opening in the cylinder head is well separated from the #6 combustion chamber. It could potentially damage the valve seal(s) in the head, but could not cause the #6 to run lean. EGR blockoff plates are used by everyone and their grandma, but only Bullish (Ara) and few others that have their act together are running the slanted intake.
Not true

Have you ever has held the head in you hands

The EGR plates will help but will not solve the problem, the exhouste can still warm up the 6 cylinder
 

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It wouldnt run right like this.....and even if it did, you would then be faced with the other cylinders running lean. I'm going to assume you have or, are getting a turbo upgrade kit..... just make sure to have your EGT installed in the hottest/leanest cylinder (#6).

-Mike


ATLSUPDAWG#2 said:
I've heard that the imbalance in flow of the stock manifold causes the #6 to run lean. If running 720 injectors would it be beneficial to run, say, an 850 in the #6 position. Of course it'll run at the same duty cycle as the 720's but inject more fuel per cycle to correct the lean condition? Anyone try this or have any feedback? Wanted to know before I invest in an injector I may not need.
Thanks,
--B--
 
J

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EGR cooler opening in the cylinder head is well separated from the #6 combustion chamber. It could potentially damage the valve seal(s) in the head, but could not cause the #6 to run lean. EGR blockoff plates are used by everyone and their grandma, but only Bullish (Ara) and few others that have their act together are running the slanted intake.

Uh...... no. I'm not going to get in a debate about this. If the exhaust is allowed to back up into the port it will run hot. I've seen enough engines get wasted until they filled that in. Funny they had all kinds of manifolds. None were stock!
 
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