[Skip Fix]

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.

[Scott65]

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

[Skip Fix]

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.

[Scott Stoneburg]

Originally Posted by Skip Fix

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.

[Skip Fix]

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".

[455-4+1]

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?

[Scott Stoneburg]

Originally Posted by Skip Fix

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".

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.

[Skip Fix]

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.

[Skip Fix]

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.

[Scott65]

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...

[Skip Fix]

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.

[455-4+1]

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

[Skip Fix]

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.

[Skip Fix]

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.

[455-4+1]

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?

[Skip Fix]

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

[Scott65]

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.

[455-4+1]

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 ?

[Skip Fix]

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.

[Skip Fix]

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