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Discussion Starter #1
thoughts on this graph... i have been having issues with this car losing power at a couple spots before about 1.4 into the run and yesterday it did this... thought it was a nitrous on/off issue, but now i do not...

driveshaft maintains, engine rpm goes thru the roof, g-meter falls off hard and convertor slip goes nutty..


jay

 

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Discussion Starter #3 (Edited)
Its not..lol. The owner said its been in there a while.. Theres deffinetly something wrong there and i've never seen a graph with the issues it had before and whats in this graph, so i figured i'd throw it up for others to see and learn from... Like i said above, till this graph, i thought it was an issue with power coming in and out, but now its pretty clear that is not the issue..
 

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I might not understand what I see in that screen shot, the scaling or something, but something doesn’t look right about the “Converter Slip”. I think the Engine RPM would be more erratic vs. Driveshaft RPM which is relatively normal, except for what looks like wheel spin at about .5 second, and with that, the wheel spin should have been accompanied by a corresponding drop in acceleration but that stays relatively constant during the driveshaft speed jump. I think some channels are incorrectly named, the names are mixed or there is EMF interference or something.

If you guys would like a better way to exchange data logs than a screen shot, you can attach your data log files in this website JMarkaudio and some of us have started for carb and engine tuning here http://racingfuelsystems.wonko3.myfunforum.org/index.php?sid=19cf3662a9436792ed43881748537bed

On this website, unlike YB, you can attach your data log files in a post so others who have the Racepak (or whatever data system) software can open the file in their computer and use the full software power and functions to expand or manipulate the file to get the most information out of it.

If you are inclined to do this, you will undoubtedly get more informed and technically accurate responses.

We don’t currently have a section devoted to nitrous but you can start a thread in the “Data Logging” section and attach your logs in it.

If it becomes obvious we need a specific nitrous section it is easy to do and we will do it.
 

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Discussion Starter #7
I might not understand what I see in that screen shot, the scaling or something, but something doesn’t look right about the “Converter Slip”. I think the Engine RPM would be more erratic vs. Driveshaft RPM which is relatively normal, except for what looks like wheel spin at about .5 second, and with that, the wheel spin should have been accompanied by a corresponding drop in acceleration but that stays relatively constant during the driveshaft speed jump. I think some channels are incorrectly named, the names are mixed or there is EMF interference or something.

If you guys would like a better way to exchange data logs than a screen shot, you can attach your data log files in this website JMarkaudio and some of us have started for carb and engine tuning here http://racingfuelsystems.wonko3.myfunforum.org/index.php?sid=19cf3662a9436792ed43881748537bed

On this website, unlike YB, you can attach your data log files in a post so others who have the Racepak (or whatever data system) software can open the file in their computer and use the full software power and functions to expand or manipulate the file to get the most information out of it.

If you are inclined to do this, you will undoubtedly get more informed and technically accurate responses.

We don’t currently have a section devoted to nitrous but you can start a thread in the “Data Logging” section and attach your logs in it.

If it becomes obvious we need a specific nitrous section it is easy to do and we will do it.
Channels are named correctly.

No emf interference.. What you see at .4-5 or there abouts is the tire starting its run when the progressive ramped all in, its on 28" slicks..I have old graphs on this same car where the driveshaft runs up just like that and then it rolls over and proceeded to gain rpm, so its not spinning there.. Plus we were running on a track that was on kill for promods.. With the power this car makes, i could throw everything at it and it would not spin on that track.


This car has been 60fting in the bottom .20's and should be in the high teens.. That pass above, it went 1.41..


If all things were well, that driveshaft would have made a much harder run then it did..

Basically whats happening is something in the line of parts behind the engine started slipping severly.. This car nomally would'nt even shift into 2nd gear till after 2 seconds out.. On this graph it went for it at about 1.2...

Jay
 

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So, you’re saying in the time from .3 to .5 second where the DS speed doubles and then falls back a third, the tire is not spinning and grabbing? How does the DS speed go up without the Engine RPM also going up? If the trans or converter were slipping and grabbing the engine RPM would be more erratic, unless, are you are using a ton of smoothing..???... If the tire is slipping the Acc. G would ordinarily show a dip at the same time. Somebody school me, I don’t get it.
 

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Discussion Starter #10 (Edited)
So, you’re saying in the time from .3 to .5 second where the DS speed doubles and then falls back a third, the tire is not spinning and grabbing? How does the DS speed go up without the Engine RPM also going up? If the trans or converter were slipping and grabbing the engine RPM would be more erratic, unless, are you are using a ton of smoothing..???... If the tire is slipping the Acc. G would ordinarily show a dip at the same time. Somebody school me, I don’t get it.
The problem here is your getting caught up strictly in that drivshaft jump and its not the issue...

If that spot your locked in on was tire spin, the g-meter would have went to shit there, but it didn't fall off till the driveshaft rpm dropped back down.....g meter dropped, engine rpm went UP, convertor slip went UP... Something the trans or convertor took a shit.. Hence the engine rpm going on a run and nothing else going with it but the convertor slip number..

Jay
 

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Jay have you made a full clean pass in this car yet? Maybe compare the graph to a better pass may help pin point what the problem COULD be.
 

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^^^ What he said.
 

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The problem here is your getting caught up strictly in that drivshaft jump and its not the issue...

If that spot your locked in on was tire spin, the g-meter would have went to shit there, but it didn't fall off till the driveshaft rpm dropped back down.....g meter dropped, engine rpm went UP, convertor slip went UP... Something the trans or convertor took a shit.. Hence the engine rpm going on a run and nothing else going with it but the convertor slip number..

Jay
You are repeating what I said in my first post.

I might not understand what I see in that screen shot, the scaling or something, but something doesn’t look right about the “Converter Slip”. I think the Engine RPM would be more erratic vs. Driveshaft RPM which is relatively normal, except for what looks like wheel spin at about .5 second, and with that, the wheel spin should have been accompanied by a corresponding drop in acceleration but that stays relatively constant during the driveshaft speed jump. I think some channels are incorrectly named, the names are mixed or there is EMF interference or something.

If you guys would like a better way to exchange data logs than a screen shot, you can attach your data log files in this website JMarkaudio and some of us have started for carb and engine tuning here http://racingfuelsystems.wonko3.myfunforum.org/index.php?sid=19cf3662a9436792ed43881748537bed

On this website, unlike YB, you can attach your data log files in a post so others who have the Racepak (or whatever data system) software can open the file in their computer and use the full software power and functions to expand or manipulate the file to get the most information out of it.

If you are inclined to do this, you will undoubtedly get more informed and technically accurate responses.

We don’t currently have a section devoted to nitrous but you can start a thread in the “Data Logging” section and attach your logs in it.

If it becomes obvious we need a specific nitrous section it is easy to do and we will do it.


Is there an explanation for this, because unless there is, doesn't it cast doubt on the rest of the information’s accuracy? If the trans or converter is slipping the engine RPM and acceleration g should be oscillating in sync with the converter slip. Something doesn’t make sense. It’s like the scaling of the converter slip is amplified and there is a ton of smoothing on Accel G, and even that is the case it doesn’t quite make sense. The scaling and smoothing of individual channels is unknown with just a screen shot to look at, whereas if a person can open the log file with the Racepak program that is easier to figure out.
 

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Discussion Starter #14
Jay have you made a full clean pass in this car yet? Maybe compare the graph to a better pass may help pin point what the problem COULD be.

its on the owners laptop, so no i do not have a "good" graph here, right now...

but regardless, first thing lane at ptc said when he saw the graph is something in the tranny took a shit, be it the pump, band, ect.. something left the building;) the owner said its been in the car 5 yrs, and never been checked:rolleyes:


like i said above the cars 60 ft fell off 2 tenths, my pop was standing on the starting line, it did not spin the tire.

jay
 

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Looks like you may low on tranny fluid, sucks air on launch and rpm soars, every thing unloads. The car settles down.
Like the transmission needs ‘secondary jet extensions’ so to say.
What about the possibility of the stator "cavitating" and momentarily loosing fluid pressure...........seen it before on a certain brand converters with a particular stator.

Monte
I can see that, but there should be RPM irregularities to go with it. I’ve done some boat driving that involved a cavitating propeller and you don’t get the kind of cavitation you refer to without the RPM flare. There must be so much smoothing on this data it hides it or it isn’t there in the first place.
 

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In my situation we had a stock trans pan, due to the crossmember, we could not see the rpm jump on the racepak, but it showed on the msd view? We ran an extra quart, and the problem went away. If this is a three speed chances are it shifted and you cant see it, with electric shifter it happens so fast, if its on an rpm switch. Go to the msd graph and take a look. Does this graph have the smoothing on? Knock it to 0 and look again.
 

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You are repeating what I said in my first post.





Is there an explanation for this, because unless there is, doesn't it cast doubt on the rest of the information’s accuracy? If the trans or converter is slipping the engine RPM and acceleration g should be oscillating in sync with the converter slip. Something doesn’t make sense. It’s like the scaling of the converter slip is amplified and there is a ton of smoothing on Accel G, and even that is the case it doesn’t quite make sense. The scaling and smoothing of individual channels is unknown with just a screen shot to look at, whereas if a person can open the log file with the Racepak program that is easier to figure out.
The accel g is smoothed big time in the screenshot above. The G and the DS rpm correspond to each other.

Jay, dont smooth the Accel G that much! haha
 

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Discussion Starter #20
The accel g is smoothed big time in the screenshot above. The G and the DS rpm correspond to each other.

Jay, dont smooth the Accel G that much! haha
Sample rate on the g-meter was bumped up slightly in the configuration..lol.. But only it and the voltage were bumped up, nothing else.. And i didn't smooth anything on that graph before taking that screen shot:p





Jay
 
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