ThePass

iTrader: (3)

Interesting. I've spoken with some others who have ran bare aluminum tanks and some have seen a lot of "corrosion" build up if it sits for an extended period of time.

Leafy

iTrader: (1)

Thats interesting. I've tried to start a car with an external wally pump after it sat with E85 in it over a winter and it wouldnt start and the pump sounded funny. Pull the pump, look in the inlet, like magic the impeller has been replaced with white death.

ThePass

iTrader: (3)

Fuel surge/swirl tank report: it works a treat.

Tested on Sunday, ran the car round and round till it read completely empty in the main tank, got another half lap out of it and then it started to sputter and came to a stop a few turns later. Towed back to the pits, pulled the top fitting from the surge tank and ran a dipstick down it to see how low we ran it. There was only about 3/4" of fuel left in the bottom of the surge tank. That's like, 1/20th of a gallon. Yep, it's working.

With the fuel starvation issue out of the way, I'm able to peel back a layer and find the next issue that was buried a bit deeper. It seems I have a communication issue between the ECU and throttle body, which ALSO sends the ECU into limp mode, just like the fuel starvation. This helps everything make a lot more sense because at GTA Finals we were scratching our heads because sometimes it would go into limp mode under one set of circumstances that we were sure was fuel level related, and then other times it would go into limp mode under circumstances that couldn't possibly be fuel level related. With one out of the way, it was a lot easier to find the second. In the morning it would go straight into limp mode upon startup or after a short bit of driving, then after a good ol' code clear and tug on connectors and wires by hand, it started working. Ryan Helmuth, another LFX Miata head, was at the track the same day and when I had the issue narrowed down to ECU, TB, or wiring, he very awesomely offered to loan me his throttle body for a session to see if that made a difference. I ran a session with his TB, then a session with mine, both successfully, so I feel we've crossed that off the list and I think it's down to the wiring and factory connector. I need to try to find that factory connector in fresh form so I can run new wires from the ECU with proper strain relief, heat protection, etc. and pin a fresh connector at the TB, then go test again.

gooflophaze

As much as I hate soldering in an automotive applications and making sure you have a good solid proper crimp.. we had the same fault and I ended up hunched under the steering wheel tinning pins on the pedal. Hasn't gone into limp mode since.

ThePass

iTrader: (3)

Looks like the throttle body connector is this one. Placed an order, can confirm once it arrives:
Ford/Mazda 6 Way with keyway for DBW Throttle Body Connector Plug Kit

Working on finding the correct female pins for the E39 ECU connector. I have an email out to EFI Connection.

gooflophaze

TE 1326030-8 edit: that's the large pin.

Molex 33467-0005/23 for the small pins.

https://www.molex.com/mx_upload/fami...UserManual.pdf
https://www.molex.com/molex/products...P_HOUSINGS.xml

ThePass

iTrader: (3)

That's a killer resource for the connector, thanks.

Molex MX64 female pins:

18-20ga https://www.eficonnection.com/home/p...-18ga-terminal
22ga https://www.eficonnection.com/home/p...-22ga-terminal

ThePass

iTrader: (3)

Naturally, Hyper gets the best Christmas present.

Jerico 4 speed dog box with Roltek shifter. Built with road race ratios, input shaft, tail housing, shifter location, etc. all to my specification.



Been saving for this for the better part of a year, since I had the trans failure at COTA in February. Credit goes to Emilio for bringing up this idea when I mentioned a sequential was out of reach. When I looked deeper I realized this could tick all the boxes I need: lightweight, shifts fast, reliable/durable, and can hold any power I throw at it. I can build a flywheel to take a common clutch so I’m no longer at the mercy of just a couple obscure options.

Going to use a Tilton aluminum bellhousing and make an adapter plate. Custom flywheel for a Tilton 7.25” twin and custom carbon fiber driveshaft are both already in the works.

Already pulled apart the spare MV7:



Got the bellhousing to a CMM thanks to local LFX gear head and CNC extraordinaire Chip, and blueprinted the LFX bellhousing pattern:



I’ve just finished up drawings for the adapter plate, sending those to CNC after the holiday.

Much excite.

Captain Crunch approved:

Chilicharger665

iTrader: (2)

I absolutely love this project. If it isn't part of your secret sauce, can you explain how you choose your gear ratios when you only have 4 forward gears? I saw a comment on FB that 4th is direct drive, so I am curious at your logic on how to space the lower gears.

Arca_ex

iTrader: (2)

Always a solid option those boxes. I would also maybe consider going with a Quartermaster 5.5" clutch. Save a little more weight and save some money vs. Tilton, and since you'll likely be doing clutchless upshifting, will reduce shock load on the drivetrain and you'll likely notice no difference. The moment of intertia for one of those nearly 50% less than 7.5" clutches if I recall correctly. Their twin disk can hold up to 600ft/lbs of torque. Triple disk is rated to 900.

curly

iTrader: (25)

Race cars never have to stop unless somethings wrong, so first is usually pretty tall, use that in the slow corners. 4th can be an over drive and is usually only for the end of long straights, 3rd is usually short straights and/or to get to 4th. I'll bet Ryan has a small collection of final drives and and maybe 1st/2nd ratios before too long. They're fairly easy to tear down and re-gear according to my co-worker who does that for TA2 cars. That way you can re-gear according to what track you're at.

Edit: think of a Miata 6-speed, at my local track it is a 4-speed, just 3rd, 4th, 5th, and 6th once you're out of the pits.

Ryan, we just one of these in a 95 cobra enduro car, supposedly good for 800+hp, even novice drivers loved it. It was a little sketch on the dyno when I tuned it, little too much pressure at the end of a run and suddenly you're in 3rd at 10,000rpm.

emilio700

iTrader: (3)

Yup. With an AZ6 on a road course any any power level, it's 4-5-6 being used. 3rd becomes your low gear for hairpins. 2nd is for the paddock. 1st for loading onto trailer.
With a broad enough powerband, you only need 4 gears. The LFX breathes really well down low, the Rotrex, up top. My guesstimate is that Ryan is making 75-80% of peak torque at half of his redline. That redline is low in an LFX. So the effective powerband is fantastically wide. This obviates the need for a close ratio box. On our cars, we have a standard final drive for most courses then one taller ratio for tracks like ACS or theoretically, COTA.

1st gear on Ryans combo will probably be good for 45mph, 4th for about 165...if I had to guess.

ThePass

iTrader: (3)

I labored over gearing spreadsheets for quite a while. The one thing you can't change is that 4th is 1:1, and for most Miatas that would be a problem (too short). However, I'm on a 3.42 Getrag rear end, with alternate Getrag 3.23 and 3.73 options. That helps.

The road race ratio approach, when you only have 4 gears to work with and assuming no standing starts, is to gear 1st to be usable at relevant track speeds. I went back and forth over making 1st short for use just for pits/trailer loading/etc. which would make it 3 usable gears on track, or say "to hell with putting around in the pits easily" and make all 4 gears exactly what I want at speed. I watched a bunch of on-boards with Trans Am cars and realized they all go with the latter approach; they are using 1st in every slow section of the track. They also run a 5.5" clutch... But they get towed around the pits with a hopped up golf cart... and I need to be able to run the car without a support crew pushing me around. I was at a crossroads. So I went long with 1st gear, but with a clutch that I think I can get around solo on. I looked at data from the tracks I am aiming at with this car, min speed in the slowest corner and how long I'd want that first gear to go before a change up, and picked 1st gear based on that. With enough power, frankly, that low gear goes by so fast I wanted to stretch it out so that it wasn't just instant wheel spin. So 1st gear goes to ~ 75mph. That's going to make getting around the pits at 10 mph tricky. For that reason I chose to do the Tilton cerametallic 7.25" because that can be slipped a bit and should make it juuuust possible to give it a footfull of revs and slip the clutch to get going around the pits... much more so than a metallic 5.5" at least. Keep in mind the factory clutch/flywheel are 52 lbs. The custom flywheel and 7.25" twin should come in well under 20 lbs. MOI is another story, and the 5.5" always wins there, but we'll be scalloping material out of the flywheel beyond the friction surface to reduce that as much as possible - quite similar to the Supermiata FW for their 7.25" twin, actually.

The result of the gearing choice is that whereas with the Camaro trans I only had 3 relevant gears (1st and 2nd too short for anything, 3rd gear in slowest sections and top of 5th in fastest sections with 6th a useless overdrive with too far of a drop), now I will have 4 relevant gears, with a better spread between each than I had before. So I cut the weight of 2 gears and yet ended up with a closer ratio transmission.

LukeG

How big is the trans compared to the MV7? Looks substantially smaller.

emilio700

iTrader: (3)

A trick I learned when driving a 4 spd stock car geared for 185mph was to just do a quick burst clutch slip to get the car rolling in the paddock then coast. Idle in first gear was 25-30mph, too fast for the paddock. To get it rolling, just a burst of revs, a touch of wheel spin then clutch in and coast.
Once rolling it was easier to just pop the clutch for an instant then coast for a while. Nasty but it was the only way I could get from the garage to the track without stalling, smoking the clutch or both.

curly

iTrader: (25)

Giant burnouts are usually a necessity. Shoot.

griff

Curious if you found that your injector duty cycle dropped with the new pump in the surge tank. I was able to get roughly 30% more duty cycle from the stock injectors and HPFP when I went to a DW 350 pump and 1000 series regulator set to 75psi on the low side.

Supe

I gotta say, it's fun reading about the same things that I was considering when picking my T101a/clutch combo. I ended up sacrificing first, but on the basis that I do standing starts at the hillclimbs, where modulating the launch can make a huge difference on overall time. Granted, I am also working with between 700-800HP and less grip than a Trans Am car, so I have a little more wiggle room with three gears. I am also accustomed to having to do three point turns and navigating tight paddocks for our TT sessions, so I went with a custom 10" twin disc with a friction material picked by Black Magic (Cale Aaronson) to allow me to do that without burning it up. I still only use the winch for trailer loading now, though. I had so many problems trying to stuff all that **** in an off the shelf bellhousing, though, that I really envy you and the small diameter clutch guys. If I ever do it again, I will go with the small diameter clutch setup and a bellhousing set up for reverse mount starter, just for parts availability and ease of fitment. I already had to have a custom flywheel made when changing motors due to crank bolt patterns and balance.

4sfed5

Cough NC cough

ThePass

iTrader: (3)

Some fancy new rear hubs just arrived. For those who noticed that we took one of the GWR NCs to Superlap Battle USA in February, waiting on these hubs and a couple other custom parts is the reason Hyper didn't make it.

But we have them now! Onward!