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Discussion Starter · #1 ·
I've been doing a bunch of tuning on my car with a wideband oxygen sensor and MAP sensor. This weekend I installed a throttle position sensor on the my Holley 650 double pumper. I was doing a bench trial to make sure it was wired correctly and adjusted right so I decided to finally get to the bottom of the accelerator pump cams and see what does what.

I put a dial indicator on the lever arm on the cam side and recorded each cam in each screw position vs throttle position voltage. I converted that to percentage so it would mean something to everyone but me. I can post pics of the setup later.

Here's the test setup details:
-carb model 4777 650 cfm double pumper
-I installed the cams with the small notch towards the main body.
-If there is just a single number in the name then the screw went through that hole in the linkage and was screwed into that hole on the cam.
-If there were two numbers (ex. 2 into 1) then that means the hole in the cam (2 in this case) was screwed into the hole on the linkage (1 in this case).

Here's what I found:
http://forums.vintage-mustang.com/files/attachments/1194960610-HolleyAccelPumpCams4777.jpg
 

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WOW You must have been really bored this weekend.

I have an old Holley tuning book that has some slope diagrams of the pump cams.

Nice job.
 

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Discussion Starter · #3 ·
I did that all last night. I just installed a real garage heater so it was fun to test that at the same time!

I've looked in Holley books and haven't found any of those plots. Do you mind checking out what the title of your book is? I wouldn't mind comparing.
 

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Great info!

I once made a graph of the numbers in my Holley book. Don't know if I still have the file, but I guess it's still on my PC somewhere.
 

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Discussion Starter · #6 ·
Cool, thanks for looking that up guys. I'll try and track that book down.

It might have been a ton of time to measure all of the curves, but I'll tell you what, I nailed the change the first time. Up until now I've been spiking lean on tip-in. I changed right to Blue 2 and that's gone. Now it dips slightly rich on tip-in in situations like you're cruising and just want to add a couple mph.

I'm recording RPM, MAP, Throttle position, wideband, and from those I can write a small function to show pump cam lift on the primaries and secondaries as well as when the power valve is open. It speaks volumes about how the car is running and what I should change.

Here's a screenshot from my data log last night.
http://forums.vintage-mustang.com/files/attachments/1195053512-data_log.jpg

It looks like once the secondary cam is finished the car goes a bit lean. I may need to increase the secondary jet size to fix this. Also slowing down the secondary cam opening profile might fix the rich dip in the AFR curve after 8977.2 ft.

This data log also explains why the car goes rich after I'm WOT and then let off the throttle. The Power Valve is hanging open for a split second.

Cool stuff.
 

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In my book the green and the pink have more lift than the blue. Looking at your chart, it shows the blue #2 as having the most. I am not sure why the numbers are different. If in fact the green and pink have more lift, it should help the lean spot before the mains get flowing. Decreasing the main air bleed size should get the mains flowing sooner too. That is something I wanted to try with mine, but I will soon be going in a different direction.
 

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Discussion Starter · #9 ·
Brian, thanks for that info on the curves in the book. At this point I think I have to go by what my parts measured to on my exact setup. Whenever something looked funny I re-measured a couple points to be sure the curve I was collecting was correct. Going to the Blue 2 really got rid of a LOT of lean spikes and the driveability stumble on tip-in. I just added the TPS sensor when I made the cam change so it's hard to show a good comparison. I do have a LCD readout of the wideband in the car (near the radio location) and I can see that I never go leaner than 1.0 on tip-in. It does drop rich now instead of going lean to 1.2 Lambda.

Also, I wish I could change the air bleeds, but mine are not threaded. I might go to that next year with a different main body, but right now I'm not quite ready to get out a drill.

The MAP sensor is a GM early 90's V6 1-bar unit originally made by BOSCH. I got that at the local auto parts store under a generic name. It's much cheaper there than at Summit for the same parts. I've found the response time to be a bit slow to big throttle stops. On slow changes it's a nice looking curve, but then when you jump on the throttle it turns into a linear curve as the motor goes up and down. It was cheap though, around $30.

The TPS is not an automotive TPS. It's an industrial angular position sensor that I came across. It threads into the pass side of the primary throttle shaft. Then I made a bracket to hold the main body in one position. That bolts on in place of the choke hardware.

I have two 5V references on my car. One is on the wideband controller which can also log additional sensors. I don't use that for logging, it just powers the wideband sensor. The wideband controller also has a linear wideband output that I can put into my data logger.

The data logger (DL1) is mostly a lat/long accelerometer and GPS logger but it can take in 8 additional sensors, RPM and four frequency inputs (typically wheel speeds which I don't have). The DL1 has it's own 5V source and ground to power the sensors.

I've got some pictures that I'll post soon of the TPS and cam measuring setup I used.

Wideband: http://www.zeitronix.com/Products/zt2/zt2.htm
Data Logger: http://www.race-technology.com/dl1_8_936.html
 

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Discussion Starter · #10 ·
I should mention that it would be possible to do much of this tuning with just the Zeitronix wideband logger. You don't even really need the LCD readout.

I use the DL1 for this because I had it for different reasons. This year was a pretty big one for my wife and I with regards to going to the Solo Nationals and trying to eek out that last little bit. [blatant proud husband] She won her first National championship in A-Stock Ladies!!! [/blatant proud husband]

The Zeitronix can't do extra 'math functions' like the DL1 can to plot the accel pump cam lift. Those are purely calculated off the measured throttle position. The DL1 just makes it easier because of the software's power and because I just have to hit the button to log it to a flash card. With the Zeitronix you have to have a laptop in the car to record. They have a PDA adpater, but I haven't found a way to get the files off the PDA to look at them on the computer.
 

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Discussion Starter · #12 ·
The piano wire is a good idea. First I just want to measure what my air bleed sizes are.

I just came across the Innovative Forum a couple days ago. I'm sure I'll blow quite a few hours this winter reading on there!

Here is the TPS:
The bracket holds that rod which is tightened to the main body of the sensor to hold it still. The sensor output voltage is very stable.
http://forums.vintage-mustang.com/files/attachments/1195062338-TPS_-_small.JPG

Here is my dial indicator setup:
http://forums.vintage-mustang.com/files/attachments/1195062413-Accel_Cam_Dial_Ind.JPG
 
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