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Re: this is tdc


tektic
Senior Member


Galant VR-4 org Post #: 1227235 posted 04/25/16 04:11 PM     Remind Me!  Send Private Message   Edit Post      
I'm Revisiting this because I'm having knock issues and think this to be the cause. Can someone smarter than me please take a look at this picture and give me the mathematical solution to dialing in these cams to the factory spec. Everything marked is the actual measured events in my motor with the cam gears set to zero.

Thank You

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GSTwithPSI
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Galant VR-4 org Post #: 1227243 posted 04/25/16 06:15 PM     Remind Me!  Send Private Message   Edit Post      
Hey dude, I'll break this down the best I can from what I see in the picture.

For the intake cam:

Intake (Card)
Opens 1* BTDC
Closes 35* ABDC

So:
1* BTDC + 35* ABDC + 180 = 216 Duration (like the card says)

Now, your measured results:
Intake (Measured)
Opens 44.5 BTDC
Closes 68* ABDC

So:
44.5* BTDC + 68* ABDC + 180 = 292.5 Duration...

So:
216 is not even close to 292.5

So, Basically, you messed something up. It's hard to say where, since any one of the steps done incorrectly can result in the measurement being off. You'll just have to redo it until you get it right.


Moving on to the exhaust:

Exhaust (Card)
Opens 42* BBDC
Closes 2* BTDC

So:
42* BBDC + 180* - 2* BTDC = 220 Duration (like the card says)


And, your measured results:
Exhaust (Measured)
Opens 44.5* BBDC
Closes 4* BTDC

So:
44.5* BBDC + 180* - 4* BTDC = 220.5 Duration

So:
220* is close enough to 220.5*

So, your exhaust cam looks to be advanced about 2 degrees.


Regardless, I doubt this is the root cause of your knock. What fuel are you on again?

Posts: 3222 | From: Annapolis, MD | Member Since: 01/02/12 | IP: (24.145.93.250) | Report this post to a Moderator

tektic
Senior Member


Galant VR-4 org Post #: 1227252 posted 04/25/16 07:23 PM     Remind Me!  Send Private Message   Edit Post      
I did it over and over. It opened and closed. There's not much to mess up. I got the same for my exhaust.

I'm running 93 octane and even with very little advance its regesters knock. I'm going to pull my plugs tomorrow.

Posts: 1340 | From: ronkonkoma, ny | Member Since: 12/19/12 | IP: (66.249.83.227) | Report this post to a Moderator

GSTwithPSI
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Galant VR-4 org Post #: 1227255 posted 04/25/16 07:58 PM     Remind Me!  Send Private Message   Edit Post      
If your intake valves were opening at 44* BTDC they'd be bent. Not to mention, your calculated duration from the measurements you took is way off. If the picture you posted is accurate, the only explanation is something got messed up in the process of degreeing the intake cam.

Under what conditions is the car knocking? WOT? How much knock are you seeing?



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1813/2000-SOLD

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tektic
Senior Member


Galant VR-4 org Post #: 1227320 posted 04/27/16 09:48 AM     Remind Me!  Send Private Message   Edit Post      
About 8 counts above 5k @ 11* and over 22psi.

The open and close events are supposed to be in the range they fall in acording to the degree wheel.

I'm thinking colder plugs, 8es may help.


Edited by tektic (04/27/16 09:59 AM)

Posts: 1340 | From: ronkonkoma, ny | Member Since: 12/19/12 | IP: (66.249.88.58) | Report this post to a Moderator

OldHairyBastard
I take bottom on trannies


Galant VR-4 org Post #: 1227323 posted 04/27/16 11:41 AM     Remind Me!  Send Private Message   Edit Post      
Make sure you have them gaped and you could go to 9's but you will have to change them all the time if you don't romp on it enough.



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tektic
Senior Member


Galant VR-4 org Post #: 1227341 posted 04/27/16 05:55 PM     Remind Me!  Send Private Message   Edit Post      
9 seconds or 9es?

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tektic
Senior Member


Galant VR-4 org Post #: 1227345 posted 04/27/16 07:43 PM     Remind Me!  Send Private Message   Edit Post      
Those were the wrong numbers. Opens at 1btdc closes at 40abdc

Posts: 1340 | From: ronkonkoma, ny | Member Since: 12/19/12 | IP: (66.249.83.227) | Report this post to a Moderator

GSTwithPSI
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Galant VR-4 org Post #: 1227348 posted 04/27/16 08:12 PM     Remind Me!  Send Private Message   Edit Post      
That still works out to 221 degrees of duration, which according to your cam card is wrong. Calculating the duration is a quick way to verify you did everything right. If your measurements = duration, you're good. If they don't, you either did something wrong, or the cam geometry is different than what the cam card says.



820/1000
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1546/2000-SOLD
1813/2000-SOLD

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tektic
Senior Member


Galant VR-4 org Post #: 1236506 posted 04/10/17 10:45 PM     Remind Me!  Send Private Message   Edit Post   
" cam geometry is different "
What If my valve install height was different? I had oversized valves put in and I'm pretty sure the valve stems weren't trimmed... Are they supposed to be? I know the exhaust still worked out properly... I don't know.

My notes say that my measured exhaust centerline was the same as the cam card when it was advanced 5.4 degrees.
My notes say that my measured Intake centerline was the same as the cam card when it was advanced 1.5 degrees.

This is based on the centerline not the opening events like the first time I did it. Does this reduce overlap?... No it doesn't, does it?

I have to look at what my gears are timed like now. I'm pretty sure its not this though.


Edited by tektic (04/10/17 10:51 PM)

Posts: 1340 | From: ronkonkoma, ny | Member Since: 12/19/12 | IP: (74.71.69.137) | Report this post to a Moderator


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