Interesting datalogs from last week
08-18-2004, 07:32 PM
#1
Melting Slicks
Thread Starter
Interesting datalogs from last week
A little background-
I swapped a super ram for a single plane EFI intake. SR ran 12.19 at 112 and the SP ran a 12.20 at 111. I am still using the "219" cam.
I shifted the old setup at 5400 and now I am shifting at 5800-6000.
I noticed something very odd in the datalogs concerning upper rpms since I started rapping it out a little more. The rpms tend to flutter a little at about 5700. Meaning that the r's steadily rise as they should......5200-5300-5400 ect. But when it gets above 5700, things get ugly. 5700-5800-5400-5600-5900-5700. Now, I have experienced valve float on race motors before, but have never had access to the data as I do with my 90. I have always felt other motors float before. What other causes could it be? If the ecm was yanking a small amount of timing, that shouldn't cause it right?? How bad would a clutch have to slip to cause this? I am starting to have clutch slip between 2nd and 3rd and 3rd to 4th, but the clutch sticks off the line.
Anybody experience this? Any input?
I swapped a super ram for a single plane EFI intake. SR ran 12.19 at 112 and the SP ran a 12.20 at 111. I am still using the "219" cam.
I shifted the old setup at 5400 and now I am shifting at 5800-6000.
I noticed something very odd in the datalogs concerning upper rpms since I started rapping it out a little more. The rpms tend to flutter a little at about 5700. Meaning that the r's steadily rise as they should......5200-5300-5400 ect. But when it gets above 5700, things get ugly. 5700-5800-5400-5600-5900-5700. Now, I have experienced valve float on race motors before, but have never had access to the data as I do with my 90. I have always felt other motors float before. What other causes could it be? If the ecm was yanking a small amount of timing, that shouldn't cause it right?? How bad would a clutch have to slip to cause this? I am starting to have clutch slip between 2nd and 3rd and 3rd to 4th, but the clutch sticks off the line.
Anybody experience this? Any input?
08-18-2004, 07:40 PM
#2
Le Mans Master
Hey good to see you are sorting things out. Amazing that the two intakes performed almost the same. What were your short time with both? Are you using a vic jr or a super? My results were similar comparing the two intakes.
How frequently does the data logger sample? It seems odd that the rpms would change that dramatically between samples without you feeling it. Maybe your ignition system is whacking out about 5700. Also have you tried shifting it below 5700? I was suprised that lower shift points didn't hurt the SP that much. I've shifted from 5600 to 6400 and dont see much of a difference, however something is killing my top end...haven't figured it out yet.
How frequently does the data logger sample? It seems odd that the rpms would change that dramatically between samples without you feeling it. Maybe your ignition system is whacking out about 5700. Also have you tried shifting it below 5700? I was suprised that lower shift points didn't hurt the SP that much. I've shifted from 5600 to 6400 and dont see much of a difference, however something is killing my top end...haven't figured it out yet.
08-18-2004, 08:53 PM
#4
Melting Slicks
Thread Starter
Ralph- with the super ram I pulled 1.88's and with the single plane I'm pulling 1.84's. But this isn't a fair comparison, as I only ran the super ram setup once on ET streets whereas I have 6 or 7 passes under my belt with the single plane on ET streets. I can now finish the 1/4 in 3rd at 6300 at 111mph (6m with 3.33 and 26" tire) I gain no ET or MPH shifting into 4th.....nor do I lose any ET or MPH. What amazes me is that I gained 2 mph in the 1000' with the SP....it traps 102 :shocked: Probably due to the 1000 rpm increase in powerband.
Now, back to the problem on hand. I don't recall how often datamaster samples. But, what bugs me it that it only does it in the upper rpms. I have the plugs gapped at 45, good wires, hypertech coil, and aftermarket module. I make peak hp at 6k......do you think the clutch could be chattering
Now, back to the problem on hand. I don't recall how often datamaster samples. But, what bugs me it that it only does it in the upper rpms. I have the plugs gapped at 45, good wires, hypertech coil, and aftermarket module. I make peak hp at 6k......do you think the clutch could be chattering