New test and tune
 

So last night Baytown had a 20-30 car track rental. It cooled off from 90 to high 70s DA was about 1650-1700.
Changes to the car were swapping the true 850 Demon in that had been on the old roller motor 455 in the 78 TA that went 10.90s and 1.52 60 fts in it and it weighed 3750 vs the 3595 the Camaro weighs. I had a larger venturi 4150 on it and since the 60s and 1/8 have just seemed off felt maybe the carb was a little lazy.A dded a vacuum pump so not getting oil out the breathes fixed header leak that melted down starter battery cable last outing. Last outing was first one with the 5000 convertor from the 455 TA to try and help 60s. It did from 1.7s to 1.6s. But still not where it should be. So some good improvements but 2 steps forward and one back with new issues. This car is "snake bit"!

Previous best was a 10.80 and best mph 127. First run was with air cleaner as all previous runs. Second run tried a burnout with the line lock and still feels like they do not spin well but my brake pressure gauges only show pressure on fronts. So something in the brake system or tranny. But when I just buzz the tires out of the water and shift it everything seems good,And it actually did spin for the first time and finally a 60 in the 1.5s. Buddy said front came up quick then dropped and unloaded rear so probably need to adjust front shock settings. Actaully shifted late at 7000 1-2, but did a weird deal at 6500 in second pulling hard quit pulling as hard blipped quickly to 7000, shift the 3rd and pulled hard again. Tranny was a little low on fluid even though I've check it numerous times since the convertor swap. So tranny 2nd gear issue, ignition. Heck tach going out, sometimes just blipping the throttle to 3000 the shift light set at 6500 comes on.

Last run just buzzed tires on the burnout. Spun a gain. Made sure I shifted at 6500 and hardly had a noticeable blip in top of second. I had forgotten to turn on the electric fans for that run so maybe they were pulling too much juice for the DUI HEI that 2nd run? Buddy said it sounded good and he did not hear a miss. Going to download the data logger later today.

But finally much better 60ft times and mph going the right way. Just never had a car with so many issues.

And everyone was socially distancing until about the time I was going to leave when a guy on a brand new Honda 450 Enduro(paper plates still) lost it and he and bike were sliding on the pavement in front of my truck! He did not have his helmet strap fastened so it popped off and he face planted and was out for a minute or so. So I had to pick the bike off him while others slowly rolled him over supporting his neck until EMTs looked him over. He kind of blew them off and just wanted to go home nearby. Not sure if alcohol was a factor or the 450 has too much power and he goosed it and hit some gravel in the pits.

Crazy! That is racing
Sometimes good other right back on the trailer!
Nice job helping the guy Skip

Hard to believe a 14x4 air cleaner made that much difference!

Yep, straightens the air out

Glad to see you are making progress Skip and hopefully having some fun.

Nice improvements, from 10.80 to 10.35..awesome! The MPH is enough to get you into the 9s once you get the 60' down.

Skip, have you tried a Dominator on it?

Nice job ! I think you will be needing to get the 9.99 and under license. Have a physical in your future.

Scott we did on the dyno with the 2" taper adapter and no difference but that was before Jeff reworked it, so may be in the future. Should have the hood clearance. Even with the 3" cowl the Victor is close to the hood. Had to use the 2" L-88 drop base to fit an air cleaner.

So here is the data logs. Only one run got picked up. Starter after I staged came over and asked if I wanted a standard or pro tree and I had already triggered it. Then one run I forgot to. You can see a"double hump" in the 2-3 engine and smaller at the driveshaft and a little in the Gs on the second copy where I blew it up and put it in the upper screen.

Battery did stay 13.5 whole run so probably that was not an issue. Fuel pressure was only 4. I have two gauges and they are 2lbs difference the lower reads the same as the logger so I bumped them up until it is 7lbs.

The wildest thing I saw racing was a full tube chassis Late Vette body diesel! He was trying to set some new record. When it did a burn out is was so violent with bottom end TQ you would have thought it would rip up the pavement!

Vacuum pump pulled about 1.5 oz(45 ml) since installation and these 3 runs.

Look at your 1st gear fuel ratio's. You are going way lean at the launch. Doesn't level out until 2nd gear. This could be why the car is so soft down low. Almost looks like to pump is not keeping up with the G's at launch, then catches back up when everything gets rolling.

I could not see a spin where driveshaft goes up more than engine but buddy felt it was .

I'll double check wide band on original I think I clicked it off for these screen shots. Looked like 11s to mid 12s.

The second picture appears to have the wide band data. Hard to be exactly sure as the picture is small and not so clear.

Yea I'll check the main graph. I can add or delete the info on the graph. The lower part is hard to see. The Gs when they were down low almost looked like a straight line.

Here is wide band over engine rpm, driveshaft below and fuel pressure bottom of graph. There is some fluctuation of wide band mid 1st

The bumps in 02 seem to correspond to the bumps in fuel pressure.
Looks like something may be up with pump or regulator from that.
Is it a bypass or a dead head, bypass pressure log should nearly be flat / smooth regardless of rpm or engine demand if operating correctly
Some numbers on the o2 scale would be handy, can you do a screen dump with just o2 graph showing scale and expand a bit vertically so we can see what's going on.

I'll try that. Bypass regulator, and you can see manual gauge needle bouncing a little. When using the logger real time it is bouncing maybe 1/2 lb.

Impressive Skip!

SO you tranny gurus would any tranny issue in 2nd do a little quick slip only at the top of second? Alhough the driveshaft rpm seems to mirror the same blip.

Based on your initial post of how it "quit pulling then started pulling again" along with the engine and driveshaft rpm mirroring each other, are you sure you don't need a couple clicks tighter on the rear shock compression? Maybe you have a little tire slip at the gear change?

It did it right before the gear change.

Baytown is having some small track rentals if you want to get your car out before the summer heat.

I'll PM you for some details later if that's ok.
And right before ethe gear change, then recovering, begs fuel delivery questions...

What it does is it acts like you pushed the clutch in on a stick car for a split second-good solid pull, not falling off, then rpm blasts up like a lot less load on the engine, then loads again on its own then I shifted. Fuel PSI stayed pretty flat on recorder.

TA had fuel issues starting with just a cam change on the original 180 hp motor, so I know how that feels. And as HP increased kept having new fuel issues.

Have you ensured there is enough valve spring pressure? Maybe not enough pressure to control the valves at high rpm. I never really experienced a distinctly noticable "falling off" but when I checked my springs they were under pressure. Switched them and saw almost 3 mph gain.

Scott I will check them, I have an on head checker. But the weird deal I definitely buzzed it 7000 in first and there was no issue on the run it was the worse. So I would expect soft springs to do it consistently at the same rpm , but I could be wrong. And when it did the weird eal it buzzed to 7K real fast and no "shooting ducks".

If the blue trace at the bottom is fuel (showing max of about 4 or 5 lb) it looks like its bouncing 2lb in 1st gear!.
Is you gauge liquid filled?.
Believe the transducer on the logger over a gauge anytime.
Get the AFR trace trough and we can look, i have spent hundreds of hours looking thousands of data logger 02 and EGT traces.
Normally my recommendation is to look at a min of 3x traces at any one time, ie rpm, acc, 02, and figure out what's going on, but when dealing with screenshot we need to nail down what's actually happening with your 02 with some readable data and scale reference.
As well as confirming data on fuel pressure.
Do you have jet extensions and a PV in the rear bowl?

I never experienced and shoot ducks either. And it felt like it was pulling strong to 6700 ( where I would shift) that may not be your issue as you are picking up 27 mph in the back half. but i would check.

Will do Scott, just looking for input like yours to try and nail it down. I'm a step higher in level with this one so new potential issues.

3rd is buzzing pretty good and not laying down so I can be sure the mph is accurate. Still not used to mph lights stopping at the actual finish line!

Probably multiple issues.

I'll blow up the O2 and fuel graph when I get home from work.

Here is engine rpm(red) fuel(purple) and wideband(green) Scale is too right but hard to see. Basically wide band 12.0 is th eline on the graph running through wide band. Fuel scal 5.0 is the top of the graph and 4.0 is running through the fuel. That is transducer pressure gauge on the regulator is showing 2 psi higher. I have since reset that to 6.5 on the transducer.

I also fattened lines up.

Numbers at right are fuel psi? Whats the setpoint of your regulator? I'd want that to stay a lot steadier all the way through the run...

Yes numbers on right are fuel PSI.I had it set at 7 with one of the mechanical gauges,but on the other gauge and transducer are only 5 so during the run looks like running 3.5-4.5. I have since bumped that up 2 lbs.

OK, there is lots going on here.......

Again..........., are any of your fuel pressure gauges (especially the odd one out) liquid filled, if so DO NOT trust them, they are subject to creep and temperature fluctuations.
Do you have jet extension in the rear and a rear power valve
What is the size of your return line Vs your feed line
What brand / make / model is your bypass reg

Data traces (if I am reading values correctly)
Note: Do you have ANY smoothing applied to the traces, if not things may not be as bad as they look, and with some smoothing can make things easier to read and evaluate

Fuel
The fluctuations in general are a concern, I will try and post a few screenshots of a bypass reg in next post. Some of these fluctuations are 2lb from peak to trough, from 5 down to less than 3. A bypass should see very little across a wide RPM range. Its dropping 2lb on the launch and then getting as low as 2.5lb shortly there after. This is not ggod. The fluctuations seem worse earlier on in the run where the Acc G's are highest, this points to to small of a supply line, bad pickup location in tank, blocked filter or something on the supply side of the pump (give us full details of the system)
Also what is the distance from the reg to the carb inlets, on a bypass this needs to be mounted as close as possible to the N&S in the carb. on the inner fencer or firewall is no good. Straight off the fuel log is best.

O2
Funnily enough, although a little rough, follows / mimics the fuel pressure delivery curve so the delivery or pressure (volume / fuel head height in bowl) is definitely affecting this. So looking like an idle of around 13.5, dropping to just under 12 as RPM climbs. (what is your procedure at this time between -1.50 and zero seconds, ie where is throttle, convertor etc.
At zero (brake / trans release ?) RPM looks like it flashes to just under 5k pretty quickly, then hooks in and climbs to around 6800 by 2.25 seconds into the run (1-2 shift) During this you have a pretty ragged RPM trace (maybe a bit of tyre slip) but massivly varying fuel pressure and resultant o2 (as fat as 11 and as lean as 14.5 at WOT !!!!!. This does not make for a happy engine. Looks like this could be a combination of fuel delivery issues to the bowl, and G related issues after that (also possibly spillover from the front bowl via the vent tube ?).

RPM
See notes above in o2 section for first gear
In the top of 2nd gear there is a definite "Blip" in RPM about 5 seconds just before the change, does you TPS show you are still at 100% WOT at this point ?.
Funnily enough it coincides with a richening of the o2 at this point as well.

I think you really need to sort out your fuel delivery system to be able to maintain constant pressure throughout the run, and then look at your fuel management once its in the carb. Until then, what else is going on is a real crap shoot at best :)

Pic attached shows a BG return style reg mounted directly off the fuel log for instant response, Carb sees full flow of pump if needed (220 in this case) prior to the reg. With this setup the is virtually no difference in pressure to the N&S from idle to WOT and back again

No smoothing in log. Also not sure if logger gauge has any dampner. Did not look quite as choppy until I enlarged the scale. Neither mechanical gauge are fluid filled both are in engine compartment on on fuel line and one T'd off regulator. Regulator is mounted right in front of carb feed line off head/vacuum pump bracket, maybe a 6" section of line to carb from regulator.

No TPS sensor on carb.

Also I have teflon lines no rubber except the actual carb line. Buddy said he read where hard lines.teflon do not dampen pulses like any rubber so wil get more bilps esp if no dampening on logger.

That's why i mentioned smoothing in the traces. Your fuel lines may not dampen "pulses" as well as others might, but the extremes are there. (as well as a constant average drop of around 2lb during the run). Enlarging the scale does not change the data, only allows you to see the numbers. The traces are formed from data points that did occur and they are generally not extrapolated to any large degree.
You also have a massive range of o2 readings, From 11 to 14.5 at WOT in first gear alone. This is not blips in the trace caused by having a rigid fuel line.
You mention reg mounted off the front of the head, does the fuel line enter at the rear, go to the bowls via a log or similar, then to the reg and then back to the tank?. Some pics of your setup would really help in any diagnosis.
Just curious as to why the carb setup and fuel system / tank / pick up / return set up are a secret if you are trying to solve these issues?

No secrets, thought I said what it is sorry. There are pictures of it in the vacuum pump thread, as well as tank shots a few years ago I posted here and engine shots on the build so no secrets. And I can gladly post new ones if you want to see the actual setup. never been bashful about any of my setups .
Entire system-sumped factory style tank about ten 1/2" holes drilled into sump from tank so a little baffle action. 1/2" bung into a Robbmc filter before the Mallory 250 pump. Wired on a relay Into a System one 8-10" filter, Then to the RobbMc bypass regulator on passenger side head and a T off the pressure port of it for a gauge. Enters on side of regulator then goes out other side to carb.That line has a 45 to straight 6" section to fuel line Aeroquip T that was a mechanical gauge port and a 90 fitting into the rear bowl. -10 return line back to top passenger side of tank 1/2 bung. -8 feed from tank to regulator and -10 return are both PTFE "teflon" lines.-8 Aeropquip, -10 Fragola since Aero has no -10. Return is out the bottom of the regulator.
http://forums.maxperformanceinc.com/...ht=vacuum+pump

What micron is the filter before the pump? And is the sump the low point of the tank? I used 5 ~ 2" holes in the floor of the tank to feed/fill the sump on mine, as that's what the directions recommended.

OK, thanks for the info, had not read the other thread, nor did I go searching

Here's a few quick observation from the Reg manufacturers install sheet

Return Line Backpressure: Even when the recommended return line size is used, it is important to check the backpressure in the return line. Once the pump and regulator are installed and all the lines are connected, check the backpressure in this manner:
~Remove the jam nut and pressure adjustment set screw.
~With the engine off (not running) turn on the electric fuel pump. Let the pump run until the lines are full of fuel.
~With the pump still running, check the fuel pressure gauge. It should read no more than 3 psi (less is better).
~If the gauge reads more than 3 psi, the restriction in the return line is too high.
~If the restriction is too high, reduce the restriction with larger lines, fewer sharp bends, etc.

This is definitely worth checking, by the looks of it you may have a short 90 (or 130 ?) out of the reg for the return line, a quick check will show if back pressure is an issue (even though you have a -10 return)

Regulator Mounting: The regulator should be mounted within three feet of the carburetor. In general, closer is better, however mounting the regulator directly to the engine is NOT highly recommended due to the vibrations and high temperatures. As the regulator heats up the fuel pressure will drop slightly (usually about ½ psi). If the regulator is mounted directly to the engine, the extra heat may lower the pressure 1 psi or more.

Cant see it being a real issue, but it is mentioned on their sheet. Stranger things have happened :)

Are you running a good relay for the pump, and has everything been checked out there, wiring etc. Possibly check the grounds, some of the pressure issues look G related (more variation in lower gears) and bad grounds are easily affected by this.

I must say I personally prefer the BG style of bypass setup, where the carbs get the full flow of the pump FIRST, then any residual is sent back to the tank via they bypass reg. Very forgiving, quick to react and nothing has to go "through" a reg, to get to the carb as in this case, less plumbing as well.
This way the fuel doesn't have to make its way "past" the large brass ? bypass plunger to get to the carb (pic of bypass plunger attached) Assume yours is similar to that pictured below from install sheet ?

And carb setup ? :)

Here are some of the sump and then regulator carb. Demon 850 4150, 50cc acel pump in front.. Pre pump 100 micron then the system 1 is a 30 micron about under the passenger seat. Yes a 90 to return. As hard as fitting a -10 return line when I laid a -12 up did not seem realistic and I know lots of guys using -8 fine. But restriction could be possible so I'll check. Robb sent me a method to today also.

I can see the return after the carb is ideal and I know lots of circle track set uop that way but keeping fuel line on the other side of frame rail for NHRA in the bellhousing area get tight in a full body car. Regulator mount has some flex although I'm sure some vibration. My TA has dead headed regulotor bolted on the waterpump and alot of street some autocross and high 10 runs and seems to do OK over the 20 years it's been plumbed. But something to look at. Mounting a regulator on the firewall just did not seem good to me, too ling a line to the carb. No fenderwells there to use either.

So I will look at fuel but the rapid rpm increase in second still is a mystery to me.

Here is a slightly larger fatter line engine,driveshaft, g graph

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 ?

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


http://forums.maxperformanceinc.com/...1&d=1588938822


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.



:)

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.

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.

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.

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.

No it is fixed.