|DRR Top Comp|
If it stalled "5800 ish" gasoline on the mountain and stalls 6000 today at sea level, it might be making 75 hp more tops, off the mountain on methanol.
Do you talk or in this case type just to hear yourself!?
"The yellow arrow at the end of the run is another telltale sign of a spragless torque converter in play, dip in rpm spiking up slightly when you step off."
For your information which you would have picked up on if you read Greg's post about this graph, is that the converter was a B&M 20608 8" converter with a sprag!!!!!!!!!!!!!!!!!!!!!!
Ya killin me Smalls!
OK back to the one graph posted on a run where the track was not good!
Around .200 seconds or so is where the converter starts to grab the motor but it appears from this one graph that the track could not hold the tires so rpm continues to climb up with no real turning point on the graph to indicate a stall rpm. About 1 second is where it shifted into high at 7300 which further upsets the tires and just before 2 seconds the tires start to hook and just after 2 seconds you see the high gear stall rpm which is around 6300.
A converter is nothing more than a load indicator. Load comes from the power of the motor trying to accelerate the car. A 4.10 gear will load the converter harder than a 4.30 gear and therefore stall rpms will be effected just as tires breaking loose which will reduce the load applied and therefore effect the stall rpm. So based on the fact that the track was not good and that the motor tune is not correct yet we just have an idea of what the stall of this converter is and until the tune is addressed along with better track conditions there is no real need to beat this to death.
Next is the motor and car combo. He has a 665 cid motor injected on alky! That's mega torque times 2. Now add a 300 shot of NOS.... Getting this car to launch smoothly off the line boils down to one think, torque management! And at this time he may need to adjust the converter it is far from the only thing this combo will need to work,,, no converter alone will fix this! In addition to the converter, launch rpm, timing, where the NOS turns on AND a Wheelie bar will be required! A fast hardtail dragster can not get off the line without a good wheelie bar. This is how wheel speed is controlled which is the most important tuning piece of information required... preventing wheelies is just a secondary deal.
From the run slips...
Run 1 is missing a ton of MPH at the 1/4, probably a good ten MPH - tune up issues or??
Run 2, picked up about 5 mph with just one degree of timing taken out... I'd back that up and take out more to see.
Next time testing, I'd first lower the launch to 4000 - 4200 and hopefully that along with a better track allows repeatable runs to work on the motor tune up and get that sorted out first then take a look at some good data and make any changes based on better info. If things go really well, maybe try a 150 shot.
Also get that wheelie bar on and make sure you have enough adjustments, you will likely be surprised at how low it will need to be. And like I mentioned before, get a data logger on the car, even just a basic system like the base racepack sportsman deal with be very helpful.
|DRR Top Comp|
The telltale of a spragless is before the shift with the red being spragless. Just check'n ya out. B&M 20608? I thought that was the biggest secret in bracket racing LoL.
The yellow is a sprag converter, which of the two arrows left or right is stall, while I have your ear Top38?
Ok, got the car unloaded and put away for now. Still need to order new nozzle jets and a couple of more main pills. Also figured out an issue I was having with my ignition...
As I stated, I started up the car, warmed it up, and did a stall test on the converter. It flashed to 6600 rpm on the brake. The run graph it recorded when I did that showed the rpm while on the brake, then flashing almost immediately to stall rpm....Keep in mind, I'm still working on the tune up and it's not there yet, it wants more fuel and I have yet to play with the timing....so I'm guessing that my converter isn't too far off as is....I think once I make some more tuning changes it will be much closer. I also think lowering the launch rpm will help settle the car more as well...
Taking little bites...making progress....and going faster!
No worry, 70's-80's right around the corner.You'll get it.
I hope so!
I just came here to say TOP38 has given great practical advice for your combo Mark. He’s had fast dragsters for a long time and he knows how to get them down the track. I agree with his recommendations and you should consider trying them.
We're talking....just sent him some more info about my stuff he wanted to see.
I think I would agree with every one of those statements. You may even clean up the launch with the extra power that comes with the tune up being better.
Foxtrot Juliet Bravo
I found a couple of other issues with the car that I'm going to address before I go out again. Figured out the recording issue with my Grid, and the issue with seeing the o2 modules and boost retard module...I use that one to log crankcase vacuum...
Not sure how or when, but the boost retard module shorted out and took out the can bus bar as well, and only the one o2 module was working...so gonna have to add those to the list...ugh.....
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