Drag Week 2012 - Project GIRTST 71 Mustang (get it right the second time)

[TheSilverBuick]

Damn, Jim its hot today. Took it on a test drive in the 92 KPA air and made a few adjustments fuel table adjustments. I jsut pleased it didn't melt down in the 108 temps.

When I've rolled through Vegas at 115*F+ degrees, I've always said the car doesn't seem to notice it, but I'm dying while behind the wheel.

[CDMBill]

Had lunch with Joe Haber (Joes66Fury) today here in Tucson. I'm picking up a few gallon's of 100 unleaded form Don's Hot Rod Shop later for the track tomorrow. I worked as a gopher at the beginning of Don's when it was inside Leo's Auto Supply back in 1972. Man that was a long time ago. Supposed to be 108 again tomorrow, good thing the racing is at night. I will be meeting Jim Forbes (Squirrel) at the track too.

[squirrel]

I first went to Don's in 1977, not long after I got my driver license. They had the new shop by then. See you tomorrow

[CDMBill]

We had a blast at Tucson's Southwestern International Raceway last night. We had great weather, really, but 6200-6000 DA over the evening which started at 100* as we arrived at the track but was down to 90* by first lap and mid 80*'s by 11 PM.

Tricky night for traction as they were alternating between Tnt with drag rcae tire cars and an import event with FWD and streeet tires.

This was the first time out with the Hoosier 315/60's and between the the DA and effective change in gear the car felt lazy. Had to moderate the launch to get it moving with a best 60ft of 1.56 and most well into the 1.60's vs. 1.40's in good conditions.

Still learning how to tune the MS3X Mega Squirt especially the launch fueling (TPS Accel Pump) but we'll get there.

I also uncorked it for the first time in years and picked up about .2 average but only 1.5 MPH. It wanted quite a bit more fuel but we ran out of time. Had most of my wife's family out at the track and showed my nephew how to drag race in his Chevy PU. Pretty cool.

I grew up racing at the old Tucson Dragway and this night brought back a lot of memories. His 6.0 vortec crew cab truck is faster than my first old Mustang.

[squirrel]

I sure had fun, thanks also for letting me know about lunch at the Hot Rods in Vail place.

That sure is an impressive mustang! It just GOES....

And the high tech stuff is really neat, especially the very thorough datalogs.

[CDMBill]

In the classic case of be careful what you ask for, the MegaSquirt based MS3X from Matt Cramer's DIYautotune.com, and Phil Tobin's software Tuner Studio and MegaLog Viewer means I can capture and log a ton of interesting inputs.

Data logging on the MS3X is much easier than having to have a laptop in the car as it records up to 16 channels of data (32 with a CANbus) on a little SD card like you'd use in a digital camera. After a run you pop it into the laptop and see what you actually did, and what the various systems on the car did.

The MS3X has a much greater variety of options and control interfaces. One of those is the accel enrichment. Much like the accelerator pump(s) on a Holley carb, you can manage how much fuel, how fast, and when. Unlike a carb, you can vary the fuel pump shot based on rate of acceleration; meaning did I mash the pedal like a drag strip launch or ease into into it llike a corner exit on freeway on ramp.

First up the datalogs showed a huge lean spike on the initial stab of the gas, meaning my first setting was trying to drive the car out of the gate without enough pump shot which made it lazy and caused a lean pop.

So like changing to a bigger squirter on a Holley I increased the volume of the shot and the speed of increase like putting a bigger accel pump cam on the throttle arm in the first hole.

This helped a little as the lean pop was gone, but the next logs would show it wasn't enough.

More troubling was the fuel pressure. One of the benefits of the EFI system is the ability to add a huge variety of inputs. I already had a little electric Auto Meter Pro Comp fuel gauge in the EFI range of 0-60. That allowed us to tap into it's 0-5v output. The guage and the input into the EMS showed the same 43-44 PSI the sytem is set for in regular driving and the burn out. But, under full throttle at the SIR 1/4 mile the very even 43.5 PSI average decended into a 10 PSI wide squiggle between 41 and a low of 21 PSI!

Down track a couple of runs had brief lean areas but no appearant detonation according to plug readings. Never the less this inconsistent fuel delivery makes the planned fuel tank sump upgrade way more of a priority. I also have to look at any restrictions in the inlet side of the A-1000 pump which includes the shut off valve I added last year when I was planning to swap between the big tank and the 5 gallon cell.

[squirrel]

Data is good.....

[CDMBill]

Having the sense to interpret and apply it on the fly is better...

Not quite there yet.

[CDMBill]

This is a repeat of my post in the EFI section, but I'm losing my mind on this one.

That said we got runner up at the NMCA True Street last weekend so how bad is it? Mid 1.5x 60 fts due to having to power brake it to get out of the 1.6x's it does due to the lower RPM launch stumble. Used to go low 1.4x's on the old tune when I didn't know about the fuel pressure issue.

Now the repeat:

So between the last time I updated this and now we went to Pomona for the NMCA race and saw some fuel pressure anomolies once I was able to datalog the 0-5v output from the AutoMeter electric gauges sensor.

The top four traces show RPM (white), staged at about 2900 then when the throttle is mashed (green) the RPM rises, the AFR's (yellow and red) briefly jump and then level out except for a small bump at the shift.

The next are a repeat of RPM (red) Pulsewidth (tan) coolant temp (yellow) and battery voltage (green) Of note at the hit pulsewidth rises and gets wiggly as the along with the RPM trace as the converter engages at around 5700.

The thrid four are Manifold Absolute Pressure MAP (purple) which jumps from around 60 KPA staged to 96 with all eight barrels open; Mnaifold Air Temp MAT which gradually falls as cooleer air enters the fornt facing scoop down track (ambient was around 100*) and Cankcase KPA which rises form 12 to 49.

Last is the Spark Advance (yellow) which is a flat 26 form 5500 to peak, two MPH traces front tire (white) and rear (red) and the star of our show the the fule pressure trace (green) which falls away form the staged rail pressure of 44 to the crazy squiggle that floats down to a range of 25-38 until the run ends and then it sanps back to 44 (not shown as this snap shot only show first and part of second gear)

Before this when we saw the fuel pressure trace from prior testing in Tucson I had re routed the inlet plumping to eliminate a .5" valve and a slightly kinked line, lowered the filter and pump assembly to assure gravity feed, replaced the A1000 Marine spec pump with a new standard A1000, and rewired the fuel pressure sensor to ensure it was on the clean power and grounds as the other sensors. Nothing changed in the fuel pressure trace. The cars performance responded to fuel table changes in MPH, and launch RPM for ET as there has been a persistent stumble on the launch as I try to get the accel tables working as well as they had with the EMS-Pro MS1 tune. Power braking helped get around the stumble but the 60 ft. times weren't great as it killed the chassis reaction.

Ideas, thoughts? No carb swaps please.

[CDMBill]

The full pass log;

[dieselgeek]

The fuel pressure bothers me. I'm logging a number of other cars and do not see anything like that. Did we try a new regulator yet? Maybe the regulator is getting a bouncing vacuum signal causing it to cycle frequently?

Re: stumble, not sure if I got a recent copy of a datalog via email while I was on the salt, can you resend it? Tip in stumble should be not too hard to eliminate. Did you try launching on the limiter at all? it's nice in that you never have to worry about accel pump shot being "perfect"

[squirrel]

The squiggles in MAP dont' seem to correspond to the squiggles in fuel pressure.

Weird....

[dieselgeek]

The squiggles in MAP dont' seem to correspond to the squiggles in fuel pressure.

Weird....

Yep, but that would only bother me if I knew for sure that they were sampling from the exact same port, hose, etc. I can't remember how he had his regulator plumbed.

[squirrel]

There's a lot more variation in fuel pressure than there is in manifold pressure.

I wonder if a datalog of the voltage at the pump would help? would need a couple resistors to drop the voltage to below 5v

[dieselgeek]

On Sicilio's landracing car, we had a similar view but on the oil pressure logging.

I had the sampling rate cranked way up, 100+ samples per second, we finally figured out that we were watching the actual pressure pulses of the Aviaid external oil pump, but you could see them at idle and also at WOT.

Between pulses we were getting as low as 25psi at WOT, it was triggering my warning light on the dash that the driver watches. After talking with Aviaid, they said this was normal - so I just "smoothed" the data using the "Lag Factoring" option in Megasquirt to keep our light from flickering. But something about Bill's deal still concerns me. Pump cavitating? regulator flaky? not sure but, that graph scares me a bit. If the injector nozzles are seeing that much differences in pressure, then fuel delivery won't be consistent.

But the car makes good MPH and isn't burning up plugs or pistons... this one's weird for sure.