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Discussion Starter #1
Last night was our first time out with the racepak and need some help reading my data and more importantly what and where I need to go with it. Has to be something I'm
missing because the car just isnt running like it should. I got a big block nitrous car on a single fogger with a 275 tire. Heres the increments,

60ft. 1.259
330 3.380
660 5.161
mph 138.27

rpm's
Launch 3400
shift 7400
drops to 6378
finish 6649

Engine is a 588 with a 44 nitrous jet and the tune up is clean and "should" be making power. I use a progressive on the nitrous all in at 1.30. I also ramp timing out to keep it from falling on its face at the hit. Car weighs 3270 and has a 1.69 glide with a 3.70 rear gear.

Just me looking and thinking, I think the converter flashes too much off the line. Its not a steady smooth curve like some of the fast radial guys post. Also when it goes to high it's like the car is on cruise. It only gains 300 rpm but people say it doesn't matter as long as the car is still accelerating on the g meter. So what do
you guys think? My back half split is a 1.78 and I seem to be stuck there. When the car ran 30's and 40's it had a 1.79 back half.

Converter slip is about 10% at the finish and the shift.

I'm sure there's a bunch of stuff I missed. Please let me know if you need anymore info.

 

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Wow. That RPM graph is very similar to mine in the 69 Camaro. Coinicidentally we have the same 1st gear & rear gear. My gearing is no where near correct, but I am running a tractor tire, & you are running a small tire. To me, & understand I am not a small tire guru, you need any or all of 3 things to go faster...more power (n20), more gearing, looser converter. The flat line after launch, the struggling to accelerate, the big shift drop, & the struggle to accelerate after the shift, are all signs of a combo that is far from optimal. Hope it works out for you, & good luck. You have a lot left, & that is the good news...
 

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big dip when the converter grabs the motor .. send this ( graph) to your converter guy then he can make the right changes !
 

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I'll bet you a $1 that dip is your system going lean while progressing. Ask me how I know .... lol

Do you have a wideban?
 

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Discussion Starter #5
My AFR wouldn't work last night. I'm buying a racepak one tomorrow. Fofo I want to put more power in it but I really feel it should be running way better with the 44 jet and I'm trying to line it out before I go to my bigger jets. The way the converter flashes up I feel a big jet would make it flash higher, lock up, then send the tires up in smoke because I let the engine get such a run at it. I could be way off base though. I'm here to get help and any and all is welcome. Thanks guys
 

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It's a lean spike for sure, fighting the same issue right now. If you trust your carb builder give him a call and explain where it goes lean and usually you can make some adjustments there to help clean it up. Also, independent control of the fuel and Nitrous solenoids is vital on 1 big system. An NLR, Launcher and a couple other boxes have the ability to add fuel in that spot.
 

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Get the Racepak one on it. My system (and more then a few other guys I race with) would go lean about .2 or .3 into the run and it would dip just like that. I bought an NLR controller so I could control fuel/nitrous solenoids separately.
 

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Im gonna guess right there and the shape isn't a lean issue-
My guess is its gonna be lean the whole time it's on the progressive unless you've messed with the fuel map.
 

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Just asking, without an A/F system, how do you guys know it is going lean? I do not think, like most are quick to conclude, that it needs more n20 (power). The characteristics of the RPMs after the shift is what leads me to believe that it more a question of the Gearing or Converter, vs. more n20. Yes, it might be the tune, but hard to say from available data. What do the plugs look like on a full clean 1/8 run? Carb jetting, N20 & Fuel Jetting, Timing, Fuel Pressure, Fuel Octane, Plugs? What was the air like, i.e. DA & GOW? Good luck. You will get it figured out.
 

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Also, show us the Pan Vac graph, as that will be a reasonable means of seeing if in fact it is going Lean, i.e. detonation. Thanks.
 

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Also, show us the Pan Vac graph, as that will be a reasonable means of seeing if in fact it is going Lean, i.e. detonation. Thanks.

Not always true


Have hurt ours 2x this year with no indication of anything wrong by looking at pan vac.
Pan vac looked perfect until it gave up the ghost
And the nose dived straight to 0


The only way we could watch it was by a leak down



I'm not saying don't watch it, I just want to share an experience. Sometimes you have to use all of your tools.
 

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Eric, excellent point. A leakdown may be in order for the OP. Yes, A/F & Pan Vac are just data points, for diagnostic purposes. Plug reading for us is the "ole reliable"...or let me say "accurate" plug reading, on a fresh set of plugs.
 

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Just asking, without an A/F system, how do you guys know it is going lean? I do not think, like most are quick to conclude, that it needs more n20 (power). The characteristics of the RPMs after the shift is what leads me to believe that it more a question of the Gearing or Converter, vs. more n20. Yes, it might be the tune, but hard to say from available data. What do the plugs look like on a full clean 1/8 run? Carb jetting, N20 & Fuel Jetting, Timing, Fuel Pressure, Fuel Octane, Plugs? What was the air like, i.e. DA & GOW? Good luck. You will get it figured out.
FOFO,u wouldn't understand unless you run a progressive control,you can check the plugs all you want running out the back,but click it off 1.5 seconds in the run then tell me what u got!happen to me plugs look fat pull fuel slow down!I probably would of burnt it up 10x if I ramped my timing instead of dopping it on the hit!
 

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Eric, excellent point. A leakdown may be in order for the OP. Yes, A/F & Pan Vac are just data points, for diagnostic purposes. Plug reading for us is the "ole reliable"...or let me say "accurate" plug reading, on a fresh set of plugs.
I've even had plugs lie-

I think it's really important to look at the WHOLE picture all of the time.

I had two holes show no signs detonation, and the hole go to 50% leak and pump terrible.
 

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Not always true


Have hurt ours 2x this year with no indication of anything wrong by looking at pan vac.
Pan vac looked perfect until it gave up the ghost
And the nose dived straight to 0


The only way we could watch it was by a leak down



I'm not saying don't watch it, I just want to share an experience. Sometimes you have to use all of your tools.
Its a science!have to be really careful!
 

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And I'm talking destroyed bad in 4 hits....


100 ft
330
660 and went a [email protected]
And then burnt up in 300ft....

All with an impeccable vacuum and a plug that had no signs of detonation....
 

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If it was converter grabbing and pulling the motor backwards the g's wouldn't crash like that, also can see the driveshaft take off as soon as it clears up. If the converter "grabbed" there as most assume the engine/DS ratio would tighten up which isn't the case. The motors going backwards because it's starving for fuel. A rich motor will make torque early but a lean motor will not accelerate unless there is enough fuel to do so. Just my .02
 

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Discussion Starter #19
I honestly think the engine is in good shape fofo. On the 7531 it just keeps pulling vacuum the whole run. No spikes, dips, or anything odd. Plugs look great. Got a 44n-28f at 6.5lbs of pressure. 17 degrees of timing, conventional heads. They're not bone white but clean. I took a couple to Monte Smith a couple weeks ago and he said they looked good, just didn't have any heat in them. I put .7 degrees in it last night and it went 139, so it wants more timing.

The carb is a pro systems that was rich enough to drown a mule. With the advice of Jmarkaudio, we converted it to a 2 circuit. I have plug pics of the old carb if anyone would like to see.

I have the Daytona sensor style progressive controller and I do progress both the nitrous and fuel with each other. Never really thought about it being lean and killing power. Great info guys. Hope there's a bunch of people that can learn from this thread, I certainly am
 

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And I'm talking destroyed bad in 4 hits....


100 ft
330
660 and went a [email protected]
And then burnt up in 300ft....

All with an impeccable vacuum and a plug that had no signs of detonation....
sucks im a believer!i can see it on the plugs!heat and oil pull a degree early plugs clean up!
 
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