Converter help?

I have been looking at my data log for the last 2 runs looking for things hurting my 60ft. I noticed that when the truck launches, the rpm jumps to around 5200 and stays flat for 1.2ish seconds before starting to climb. At the same time, the drive shaft rpm spikes, drops a couple hundred, climbs, drops then climbs at a steady rate. I know there is a little wheel spin at launch which is what I think I am seeing in the graph, but I am curious about the engine rpm staying flat for a second before climbing. Does this look normal? My launch rpm is 4500 and the converter stall was set at 5000.

This data tells me that your weight and traction equals engine power at 5200 rpm for that time between .2 to .8 seconds. If its hooked up to the track in that time period less weight and or more power will give it a rise upwards and improve the 60ft.
However, more than likely you got some tire spin between .2 and .8 seconds. The driveshaft speed is flat because its equaling the engine power at launch.

Are you looking to dead hook or do you want instantaneous wheel speed?

Dave De wrote:This data tells me that your weight and traction equals engine power at 5200 rpm for that time between .2 to .8 seconds. If its hooked up to the track in that time period less weight and or more power will give it a rise upwards and improve the 60ft.
However, more than likely you got some tire spin between .2 and .8 seconds. The driveshaft speed is flat because its equaling the engine power at launch.

Are you looking to dead hook or do you want instantaneous wheel speed?

The truck always has had a little tire spin at launch, but back with I ran an 8 inch converter with a 5500 stall, I launched at 4800 and the truck would do 1.43-1.46 60ft and Et at 6.66 and 99-101 mph. With the new converter, I launch at 4500 and get a 1.6 60ft, 6.71 ET and 103mph. I will add Jay @ Broader set the converter up for nitrous (not using yet) and to run both 1/8 and 1/4 mi. I have already taken 100ish pounds out of it and will be taking another 75-100 out of the truck and hopefully 50-75 out of me over the winter.
Between dead hooking or wheel speed, I think wheel speed is easier on parts then dead hooking. I am also wondering if shock adjustment might help as well.

Alan

The first dip in the curve indicates a suspension load cycle at .1 seconds, probably common and nothing that can be done about it. Then from 2/10ths to 7/10ths there is a happy progressive climb that parallels the rest of the curve. Then another dip from 7/10ths to +8/10ths. I dont think you want any dips in that curve where you should shoot for a horizontal line at worst case. Think about that, the drive shaft is slowing down thru the run between 7/10ths and 8.5/10ths.
Maybe a shock setting change to spread the hit out would help. Your converter flash shows 4,800 rpm so maybe drop your 2 step down to 4,000 rpm. This will hit the converter harder.
Awesome to have data.

Idk much about the data but the way you describe the rpm staying the same for 1.2 sounds a lot like a tight nitrous converter. So it lost 60ft but picked up mph and once you spray it I bet it really wakes up

Dave De wrote:The first dip in the curve indicates a suspension load cycle at .1 seconds, probably common and nothing that can be done about it. Then from 2/10ths to 7/10ths there is a happy progressive climb that parallels the rest of the curve. Then another dip from 7/10ths to +8/10ths. I dont think you want any dips in that curve where you should shoot for a horizontal line at worst case. Think about that, the drive shaft is slowing down thru the run between 7/10ths and 8.5/10ths.
Maybe a shock setting change to spread the hit out would help. Your converter flash shows 4,800 rpm so maybe drop your 2 step down to 4,000 rpm. This will hit the converter harder.
Awesome to have data.

You are correct, I am geeking out with the data. Basically I am trying to understand what the data is telling me. I will try dropping the 2 step down to 4,000 and see what that does. On the shocks, I have been running the settings Viking recommend, but I think I am going to soften the compression and soften the rebound on the rear and stiffen the compression on the front to maximize weight transfer.

droppedf100 wrote:Idk much about the data but the way you describe the rpm staying the same for 1.2 sounds a lot like a tight nitrous converter. So it lost 60ft but picked up mph and once you spray it I bet it really wakes up

Jay said it would gain stall with nitrous. I am slowly acquiring all the accessories needed for nitrous, and plan to order the NX assassin kit in November assuming nothing else goes wrong.

Sounds good. I have an Induxtion solutions kit on my truck. Is your truck efi? What are you using to datalog?

droppedf100 wrote:Sounds good. I have an Induxtion solutions kit on my truck. Is your truck efi? What are you using to datalog?

Sorry just saw this. I am looking at Induction solutions as well. My truck is running a Rons terminator MFI setup. For Datalogging, I installed an RPM Performance system. Recording Engine Rpm, Driveshaft RPM, Oil pressure and temp, Trans temp, all 8 EGT's, water temp and engine vacuum. I am eventually going to expand the system to include shock/suspension travel.

HorsinAround wrote:

droppedf100 wrote:Sounds good. I have an Induxtion solutions kit on my truck. Is your truck efi? What are you using to datalog?

Sorry just saw this. I am looking at Induction solutions as well. My truck is running a Rons terminator MFI setup. For Datalogging, I installed an RPM Performance system. Recording Engine Rpm, Driveshaft RPM, Oil pressure and temp, Trans temp, all 8 EGT's, water temp and engine vacuum. I am eventually going to expand the system to include shock/suspension travel.

Very cool. I’ve been thinking about a system to log stuff. Right now i just have a 6al-2 programmable on a nitrous bbf and a turbo carb sbf so some data would sure be nice. Then my slower truck has MS3 which can log any sensor I hook up to it

So far I am happy with the RPM logger and the data is great. It comes with a basic log book that you can do for each recorded run, but I'd really like a way to export/link to a tool like crew chief pro or the like so you can can record weather, etc and be searchable.

Alan

An old man told me this trick for setting rebound on your rear shocks. With the car on level ground. Push down real hard on the back of the car and watch it. It should rise up slowly. The time it takes to rebound to full up when checked with a stopwatch should be about 70-80% into the run. Its a good starting point. As for the compression we just did it by feel. And it worked great for my car first time off the trailer. Car runs 5.50. I think we set the shocks for about 4-4.5 sec.