Gutless Stroker - Page 2 - JeepForum.com
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post #16 of 25 Old 10-12-2017, 11:18 AM
jsawduste
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Originally Posted by youngjeepr View Post
Well I just found out that indexing the dist. Doesn?t adjust ignition timing it only adjusts injector timing.
That's not a true statement. The injector timing is controlled by the ECM.

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post #17 of 25 Old 10-12-2017, 11:24 AM
mike134
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If the timing is so out of spec that the computer freaks out, I can see the computer adjusting whatever it wants. And not to good effect.
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post #18 of 25 Old 10-12-2017, 12:20 PM
jsawduste
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Wish you folks would read the FSM and understand how the system works.
99% of these comments are simply wrong.
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post #19 of 25 Old 10-12-2017, 12:56 PM Thread Starter
youngjeepr
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Quote:
Originally Posted by jsawduste View Post
Quote:
Originally Posted by youngjeepr View Post
Well I just found out that indexing the dist. Doesn?t adjust ignition timing it only adjusts injector timing.
That's not a true statement. The injector timing is controlled by the ECM.
Thanks for correcting me I?m just repeating what I was told on the other forum.

So what does clocking the dist. do exactly? Did I cut the ears off of it for no reason?

88 YJ- 4.7l stroker, AW4, SOA, 8.8, hp D30 powertrax no slip,3" front stretch with waggy springs, stock replacement springs in the rear, 35/12.5 r15 goodyear kevlars


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post #20 of 25 Old 10-12-2017, 05:53 PM
jsawduste
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Quote:
Originally Posted by youngjeepr View Post
Thanks for correcting me I?m just repeating what I was told on the other forum.

So what does clocking the dist. do exactly? Did I cut the ears off of it for no reason?

Hoping to make this a short but concise answer.


1. The ECM reads the 4 sets of notches that are on the flywheel/flexplate that are 120* apart. These notches break the magnetic field causing a pulse. The pulse is read by the ECM and with inputs from the other sensors and the calibration adjusts the ignition timing.
NOTE: there is no reference point for the ECM to adjust to. It does that by the cap and rotor.


2. The cam sensor has a single notch that also sends a pulse to the ECM. This pulse provides a fuel (injector firing) synchronization signal to the ECM.


The ECM looks at the pulse signal and fires the correct injector per the engine firing order via the driver in the ECM.


When the dizzy is a tooth off two things happen.


The spark happens at the wrong time because the rotor is in the wrong position.


Plus the injector fires at the wrong time. Think cam timing and the piston/valve events to wrap your head around this.


Can you see now that the cam sensor does not adjust the injector timing but syncs the pulse to the ECM so that it (the ECM) knows which injector to fire ?


If we change the cam timing from stock than the timing of the pulse in relation to piston position/valve timing MAY fall out of the range the ECM can read it (tooth off, remember the ECM compares the signals). Or the engine will see an injector signal that is not in time with the piston/valve events and run crappy. There is more to this but if you set and think about how everything meshes together you`ll get the understanding.


The cam runs at half speed to the crank. So 4 degrees of crank rotation equals 2 degrees of cam rotation.


Compared to stock some cams are ground with a different cam timing event. Or the cam chain and gear set may have multiple keys to change the degree relationship between the crank and cam. You don't know and manufacturing tolerances can stack up. This is why you always want to degree a cam in and compare it to what the manufacture specs.


Lets pretend we build our engine with an aftermarket cam that is ground 4 degrees advanced. That 4 degrees of crank rotation. We degree it in and set our marks accordingly. That cam now has the cam sensor 2 degrees advanced. Which we now know changes when the injector is going to fire. To make all the parts play nice we need to rotate the dist. (which houses the cam sensor) 2 degrees.


I know there is a lot of info here and some of it goes against the internet keyboard experts. You have to grasp the whole ignition timing and injector sync (phasing if you wish) with the crankshaft position.


To my right as I write this is the FSM that explains how the system works. They go into a bit more detail and assume the reader has a bit of understanding on how an engine works and why.
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post #21 of 25 Old 10-12-2017, 06:28 PM Thread Starter
youngjeepr
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Wow thank you! Those are the types of posts I like.

Do you have any suggestions as to what my problem could be? I?m thinking I degreed my cam wrong when I put it in. Which isn?t letting me set the dist. properly.

I just got off work so I?m headed home to work on it again.

88 YJ- 4.7l stroker, AW4, SOA, 8.8, hp D30 powertrax no slip,3" front stretch with waggy springs, stock replacement springs in the rear, 35/12.5 r15 goodyear kevlars


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post #22 of 25 Old 10-13-2017, 01:00 AM
jsawduste
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Check the cam timing with a degree wheel and a stop. That'll be your baseline to set the dist up. Even if its needs to be fine adjusted.
After it's running turn the dist CW/CCW till the engine runs best.
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post #23 of 25 Old 10-18-2017, 08:37 PM Thread Starter
youngjeepr
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Ok well I checked where the cam is and it is to far advanced I think. My dial indicator (on the lifter) reads .074 when the instructions say it should be between .048 and .058. That?s why I think the cam is to far advanced. I then realized my timing set isn?t adjustable.... so I will be ordering an adjustable one in the morning. Any suggestions on timing sets?

88 YJ- 4.7l stroker, AW4, SOA, 8.8, hp D30 powertrax no slip,3" front stretch with waggy springs, stock replacement springs in the rear, 35/12.5 r15 goodyear kevlars


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post #24 of 25 Old 10-18-2017, 11:02 PM
lclark2074
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I used a 4.0 block and connecting rods with a 4.2 crank, question aren't you suppose to use 4.2 connecting rods because thy are shorter with longer crank?

night crew 226

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post #25 of 25 Old 10-18-2017, 11:24 PM Thread Starter
youngjeepr
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Quote:
Originally Posted by lclark2074 View Post
I used a 4.0 block and connecting rods with a 4.2 crank, question aren't you suppose to use 4.2 connecting rods because thy are shorter with longer crank?
Depends what type of stroker you build but I chose to go with the longer 4.0 rods.

88 YJ- 4.7l stroker, AW4, SOA, 8.8, hp D30 powertrax no slip,3" front stretch with waggy springs, stock replacement springs in the rear, 35/12.5 r15 goodyear kevlars


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