Performance Distributors DUI Timing Curve
#1
Performance Distributors DUI Timing Curve
Hi all,
As promised, here is the timing curve Performance Distributors put on my distributor.
I figure this will be helpful since, even though I've done a few performance upgrades to my engine, it is still relatively stock. If your specs are similar to mine (which I imagine most are), this is the timing curve DUI would send your way.
Also, these are the ONLY things they take into consideration. If you have oversized
valves, different gearing, different tires, etc. etc. it doesn't seem to matter since they don't even take it into account.
These are the questions they asked me and this is what I put down:
Year, Make, Model: 1981 Ford Bronco
Weight of Vehicle: 4500
Towing? No
Engine Make/size: Ford 300
Compression Ratio: 8.5 (stock)
Carburetion: 4bbl
CFM: 465
These are the stock cam specs, which I still have in my engine:
Cam Duration @ 0.050" 192
Valve Lift: .395"
Transmission: manual
Max RPM: 4500
Fuel Type?: Regular
Additive? No
Timing Curve:
Base 12*
<b>Mechanical Advance</b>
*Note that these all include the base 12* timing.
<table border="1">
<tr><td>RPM</td><td>Timing</td><td>Total</td></tr><tr><td>500</td><td>0</td><td>12</td></tr><tr><td>750</td><td>2</td><td>14</td></tr><tr><td>1000</td><td>6</td><td>18</td></tr><tr><td>1250</td><td>10</td><td>22</td></tr><tr><td>1500</td><td>13</td><td>25</td></tr><tr><td>1750</td><td>15</td><td>27</td></tr><tr><td>2000</td><td>17</td><td>29</td></tr><tr><td>2250</td><td>18</td><td>30</td></tr><tr><td>2500</td><td>20</td><td>32</td></tr><tr><td>2750</td><td>22</td><td>34</td></tr><tr><td>3000+</td><td>22</td><td>34</td></tr>
</table>
<b>Vacuum Advance</b>
<table border="1">
<tr><td>Vacuum</td><td>Extra Timing</td></tr><tr><td>0</td><td>0</td></tr><tr><td>1</td><td>0</td></tr><tr><td>2</td><td>0</td></tr><tr><td>3</td><td>0</td></tr><tr><td>4</td><td>0</td></tr><tr><td>5</td><td>0</td></tr><tr><td>6</td><td>0</td></tr><tr><td>7</td><td>0</td></tr><tr><td>8</td><td>0</td></tr><tr><td>9</td><td>1</td></tr><tr><td>10</td><td>5</td></tr><tr><td>11</td><td>7</td></tr><tr><td>12</td><td>11</td></tr><tr><td>13+</td><td>14</td></tr>
</table>
So, when I'm driving down the interstate at 65mph, my RPMs are 2150. I'm usually pulling around 10hg of vacuum. 2150 = 30* and 10hg = 5* for 35* of total timing.
As promised, here is the timing curve Performance Distributors put on my distributor.
I figure this will be helpful since, even though I've done a few performance upgrades to my engine, it is still relatively stock. If your specs are similar to mine (which I imagine most are), this is the timing curve DUI would send your way.
Also, these are the ONLY things they take into consideration. If you have oversized
valves, different gearing, different tires, etc. etc. it doesn't seem to matter since they don't even take it into account.
These are the questions they asked me and this is what I put down:
Year, Make, Model: 1981 Ford Bronco
Weight of Vehicle: 4500
Towing? No
Engine Make/size: Ford 300
Compression Ratio: 8.5 (stock)
Carburetion: 4bbl
CFM: 465
These are the stock cam specs, which I still have in my engine:
Cam Duration @ 0.050" 192
Valve Lift: .395"
Transmission: manual
Max RPM: 4500
Fuel Type?: Regular
Additive? No
Timing Curve:
Base 12*
<b>Mechanical Advance</b>
*Note that these all include the base 12* timing.
<table border="1">
<tr><td>RPM</td><td>Timing</td><td>Total</td></tr><tr><td>500</td><td>0</td><td>12</td></tr><tr><td>750</td><td>2</td><td>14</td></tr><tr><td>1000</td><td>6</td><td>18</td></tr><tr><td>1250</td><td>10</td><td>22</td></tr><tr><td>1500</td><td>13</td><td>25</td></tr><tr><td>1750</td><td>15</td><td>27</td></tr><tr><td>2000</td><td>17</td><td>29</td></tr><tr><td>2250</td><td>18</td><td>30</td></tr><tr><td>2500</td><td>20</td><td>32</td></tr><tr><td>2750</td><td>22</td><td>34</td></tr><tr><td>3000+</td><td>22</td><td>34</td></tr>
</table>
<b>Vacuum Advance</b>
<table border="1">
<tr><td>Vacuum</td><td>Extra Timing</td></tr><tr><td>0</td><td>0</td></tr><tr><td>1</td><td>0</td></tr><tr><td>2</td><td>0</td></tr><tr><td>3</td><td>0</td></tr><tr><td>4</td><td>0</td></tr><tr><td>5</td><td>0</td></tr><tr><td>6</td><td>0</td></tr><tr><td>7</td><td>0</td></tr><tr><td>8</td><td>0</td></tr><tr><td>9</td><td>1</td></tr><tr><td>10</td><td>5</td></tr><tr><td>11</td><td>7</td></tr><tr><td>12</td><td>11</td></tr><tr><td>13+</td><td>14</td></tr>
</table>
So, when I'm driving down the interstate at 65mph, my RPMs are 2150. I'm usually pulling around 10hg of vacuum. 2150 = 30* and 10hg = 5* for 35* of total timing.
Last edited by AbandonedBronco; 03-02-2015 at 07:24 PM. Reason: Changed table to have two columns for timing. One for the mechanical, and one for the total.
#2
So I assume the mechanical advance table also includes the 12* initial advance, and the 10 hg. signal you are measuring is the distributor hose vacuum, be it ported signal or direct manifold vacuum signal.
Is 'valve lift' lobe lift?
I would be curious to know if the secondaries on your 4V have started to open at 65 mph Road Load? With 10" vacuum I'm guessing no.
Is 'valve lift' lobe lift?
I would be curious to know if the secondaries on your 4V have started to open at 65 mph Road Load? With 10" vacuum I'm guessing no.
#3
Yes on the mechanical advance including base timing (and I added a note).
Hrmm...
Yes, that's the number I gave them for valve lift, since that's what I saw when I looked up the specs. Lobe lift isn't the same as valve lift though, is it? If the lobe is 0.249" and the rockers are a 1.6 ratio, that'd put the valves at .398" (.249 * 1.6).
Yikes, I'll write them and ask them how much difference that would make.
Hrmm...
Yes, that's the number I gave them for valve lift, since that's what I saw when I looked up the specs. Lobe lift isn't the same as valve lift though, is it? If the lobe is 0.249" and the rockers are a 1.6 ratio, that'd put the valves at .398" (.249 * 1.6).
Yikes, I'll write them and ask them how much difference that would make.
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#10
I wonder if that would have normally been taken into account if you filled in your specs while ordering one and put "EFI" instead of "4BBL".
#12
#14
Doesn't mean you couldn't swap it out for a DUI if you were so inclined.
The dropdown menu does say "Fuel Injection". I know I've read builds where people use the MegaSquirt for the fuel injection but still have a vacuum controlled distributor.
Either way, my only point was if one did have the EFI head and wanted to take it into account, that was about the only thing in their questionnaire that remotely had to do with it. Otherwise, there wasn't anything that would be answered differently.
The dropdown menu does say "Fuel Injection". I know I've read builds where people use the MegaSquirt for the fuel injection but still have a vacuum controlled distributor.
Either way, my only point was if one did have the EFI head and wanted to take it into account, that was about the only thing in their questionnaire that remotely had to do with it. Otherwise, there wasn't anything that would be answered differently.
#15
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