[455-4+1]

There is a sharp rise in the driveshaft RPM at the point as well indicating possibly some slip, then recovery, funny thing is, fuel pressure spikes at exactly the same time.. If the engine RPM spiked without the driveshaft RPM following suit i would think Trans or converter, but they spike together........
Which came first, the chicken or the egg ?

If the fuel system is operating correctly, the pressure should be alot more stable REGARDLESS of RPM, G's and run time down the track, unless it cant keep up for some reason (bad grounds, pickup issue, low voltage to pump - not system voltage)

At the starting line the demand on the reg / pump should be at its least as there are 2x full bowls (hopefully)
Yet this is where the "reserve" in the bypass system is at its least as shown by the massive pressure drop when the G's are at their greatest.

As you go down the track and Acc G;'s decrease, you fuel system starts to catch up. It really should be the opposite if the system is working fine, but your engine demands too much of the system.

Unless your Demon is a Circle or Oval track series, it shouldn't have come with a rear PV, so that eliminates a variable after the N&S.
Have used 850 MD before (annular) but never need to go to 50cc pump.
It did have a slight lean stumble off idle, but restricting the IFR slightly to get more turns out on the idle screws tidied that up with out the need for more Acc pump fuel.
Given you are leaving at 3k or so (foot brake on part throttle or Brake ?) I doubt the Acc pump is causing too much concern depending on what throttle opening it takes to get there ?

[johnta1]

I would try a different fuel regulator or reroute.
I used something like the 2309 Mallory one (I think number was that)





It basically lets all the fuel from pum to carb, then regulated back to tank to get your pressure needed.



A pdf of a regulator (couldn't find mine this will give you an idea)


Mallory Regulator


This way you know there is no restriction from pump to carb.





Your regulator it would be rerouted so that the main inlet hose would be switched with the return line back to tank basically.

[Skip Fix]

Foot brake. Yes I noticed to spike in driveshaft rpm also-like tires spun then hooked at the top of second?

Rear metering does not have a PV and has jet extensions. When the carb was on my old roller 455 in the Trans Am with this same convertor it had 30cc pumps front and rear-, but lots of folks say add the 50 up front so I did before I swapped carb on.And often had even better 60 fts than we has so fat. Just took off a Demon with larger venturis and it had 50cc front and rear.

"As you go down the track and Acc G;'s decrease, you fuel system starts to catch up. It really should be the opposite if the system is working fine, but your engine demands too much of the system." I agree and how my previous fuel delivery problems were. Wish the datalogger had gotten the other run to look at fuel, one run I forgot to trigger it, still not used to all the new stuff in this new car.

[Scott65]

Skip, can your datalogger be automatically triggered? Maybe rpm>1000, or a power on relay grounded by a temp sensor or such? Something where you don't have to remember to manually turn it on? On the potential fuel issue, i always start by flow testing the pump free flow. Had this issue a while back with a brand new pump.

[Skip Fix]

It can off any 12 V trigger but since I don't use a trans brake. Line lok maybe but then it may start in burnout and run out of time. Guess I need a switch on the outside and crew to turn it on for me

I think looking a fuel is a good thing to rule out. I'll try and pull up a log from a previous outing run-but slower run and look at fuel also to see if it was doing weird things at launch or new with the looser convertor.

I do appreciate all the input guys.

[Scott65]

Is the time of the log fixed? How long does it run? I'm unfamiliar with anything but the one I use. On the laptop mine will go indefinitely, on the SD card it runs for 10 minute cycles, or key on to key off.

[Skip Fix]

No it is fixed.