Gone High Tech!

Ishiftem

Ishiftem

Well Known Member
Supporting Member 2
Added a data logger. Engine rpm, driveshaft rpm, input shaft rpm, g meter, and two o2 sensors. This should be cool. Also put a programmable digit 6 ignition. Hoping to wring out that last bit and reduce some frustration.
 

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1964SuperStocker

1964SuperStocker

Well Known Member
Supporting Member 3
Ishiftem said:
Tried it out today. Confirmed some things and discovered new things. This is going to be addictive.
Click to expand...
Be careful and don't chase your tail. Information can be addictive. Here I am up at 1:45am looking up pistons for my 454 because the jet boat needs more for no reason. LOL! So many to choose from on a boat I'll get out maybe 10 times a year for a few hours for fun. LOL.
 
63 dream'n

63 dream'n

Well Seasoned Member
Supporting Member 4
I don’t mean to ask you to be a translator..... but between your data logic and Brian’s ......what are the big drops (blue) coming between the peak and valley..........I’m assuming ( yes I know what they say about assuming )at the shift points........
Thanks in advance sincerely Petey ......!!!!

Sorry looked a little closer it’s engine RPM...... so why does the RPM drop so low between your shift points
 
Ishiftem

Ishiftem

Well Known Member
Supporting Member 2
Russ is correct. The green is engine rpm, blue is input shaft rpm, and orange is driveshaft rpm. Russ is also correct that this is a clutch assisted gear box. Even though I don't use the clutch to shift, the gear box still goes through neutral as it shifts gears. That is why those spikes are there. What is there to learn. Any separation between the lines for the engine rpm and input rpm indicates clutch slippage. Wherever the lines lay on top of each other indicates the clutch is locked up. We want some amount of clutch slippage on the gear change and launch. Some slippage at the launch will not shock the tire loose and also keeps the engine accelerating instead of bogging. Same on the gear change. Having some slippage also saves parts big time. I lost at Tri State last year because I had tightened the clutch up. Having the clutch tighter generally makes the car slower but a little more consistent for bracket racing. I had mine too tight and when I shifted to fourth the shock cleaned the splines out of the disc. Driveshaft rpm tells you if you are spinning the tires. Even small bumps in the track will show up as spikes in the driveshaft speed. Driveshaft speed can also be a tool used to tell you which adjustments to make on the launch. Lets say you know that your best 60 foot times are when the driveshaft speed is 800 rpm at .25 seconds into the run and 1300 rpm at .50 second.(I'm just throwing out numbers). So you make a pass and your 60 foot is slower. By looking at driveshaft speed, you can see if it spun too hard (higher driveshaft speed) or didn't spin enough (lower driveshaft speed). You can then use that info to help determine what adjustments to make whether they be launch rpm, clutch, tire psi, shocks, etc. Looking at my graph, you can see that the launch needs help.The steady green line to the left is engine rpm on the rev limiter. When it starts to dip and the orange line (driveshaft rpm) shoots up is the launch. The drive shaft rpm shoots up to 1300 rpm and hangs there for .33 seconds. That is too high and the instant manner in which it got there shows the tire broke loose hard. The driveshaft rpm thn starts to climb slightly showing that it starts to unload the tire further. You can see this in how at the same time the blue line (input shaft rpm) goes up and almost touches the green line (engine rpm). This is because as the tire breaks loose more there is less load on the clutch and it starts to lock up. Next is a dip in the drive shaft speed. That is when the tire starts to hook up. You can also see the input shaft rpm drop as the clutch starts to slip again due to the extra load. After that the drive shaft rpm makes a steady climb except the spikes at the shift points. So it is breaking the tire loose and a steady rate till .33 sec into the run, unloads the tire between .33 and .60 secs into the run, and then starts to bite again. Make sense Petey?
 
1964SuperStocker

1964SuperStocker

Well Known Member
Supporting Member 3
Ishiftem said:
Russ is correct. The green is engine rpm, blue is input shaft rpm, and orange is driveshaft rpm. Russ is also correct that this is a clutch assisted gear box. Even though I don't use the clutch to shift, the gear box still goes through neutral as it shifts gears. That is why those spikes are there. What is there to learn. Any separation between the lines for the engine rpm and input rpm indicates clutch slippage. Wherever the lines lay on top of each other indicates the clutch is locked up. We want some amount of clutch slippage on the gear change and launch. Some slippage at the launch will not shock the tire loose and also keeps the engine accelerating instead of bogging. Same on the gear change. Having some slippage also saves parts big time. I lost at Tri State last year because I had tightened the clutch up. Having the clutch tighter generally makes the car slower but a little more consistent for bracket racing. I had mine too tight and when I shifted to fourth the shock cleaned the splines out of the disc. Driveshaft rpm tells you if you are spinning the tires. Even small bumps in the track will show up as spikes in the driveshaft speed. Driveshaft speed can also be a tool used to tell you which adjustments to make on the launch. Lets say you know that your best 60 foot times are when the driveshaft speed is 800 rpm at .25 seconds into the run and 1300 rpm at .50 second.(I'm just throwing out numbers). So you make a pass and your 60 foot is slower. By looking at driveshaft speed, you can see if it spun too hard (higher driveshaft speed) or didn't spin enough (lower driveshaft speed). You can then use that info to help determine what adjustments to make whether they be launch rpm, clutch, tire psi, shocks, etc. Looking at my graph, you can see that the launch needs help.The steady green line to the left is engine rpm on the rev limiter. When it starts to dip and the orange line (driveshaft rpm) shoots up is the launch. The drive shaft rpm shoots up to 1300 rpm and hangs there for .33 seconds. That is too high and the instant manner in which it got there shows the tire broke loose hard. The driveshaft rpm thn starts to climb slightly showing that it starts to unload the tire further. You can see this in how at the same time the blue line (input shaft rpm) goes up and almost touches the green line (engine rpm). This is because as the tire breaks loose more there is less load on the clutch and it starts to lock up. Next is a dip in the drive shaft speed. That is when the tire starts to hook up. You can also see the input shaft rpm drop as the clutch starts to slip again due to the extra load. After that the drive shaft rpm makes a steady climb except the spikes at the shift points. So it is breaking the tire loose and a steady rate till .33 sec into the run, unloads the tire between .33 and .60 secs into the run, and then starts to bite again. Make sense Petey?
Click to expand...
All of that was pretty exciting to read but my mind wants more.
 
63 dream'n

63 dream'n

Well Seasoned Member
Supporting Member 4
Ishiftem said:
You asked!
Click to expand...
.
Just a little bit of sarcasm on Petey’s part.......No I do enjoy learning new things from people as knowledgeable as yourself ......:even though I know I will probably never have a 1/4 mile car at that level.....or just finished...... it’s still nice to know how people professionally tune a race car.....: I was genuinely interested .......Thanks for the lesson professor......I’m listening
 
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