Our fuel cell is a JAZ 22 gallon. We run about 8-9 gallons per hour so that gives a few gallon safety margin. We fill through a tube mounted in the drive rear quarter window and have 1.5" ATL fuel delineator vent valve that gives us a 5 gallon dump in 15-20 seconds. To isolate the driver compartment we used a sheet of poly carbonate mounted with a combination of metal flashing and fire resistant bonding.

 

If you get a chance sometime could you post a picture of your fuel cell installation. That is kind of what I was thinking of, but would be nice to see how it all fits together.

 

The only picture I have at the moment is from when we were taking things apart to add the vent. I'll take some current photos in the next couple days.

 

Thanks man! I can kind of see where you are going with that. no rush on more pics, but it would be helpful too whenever you get a chance.

Do you run with Lucky Dog at all? I was up in Portland for a Lucky Dog race in July 2019 and loved it.

Carl

 

That’s basically the same way I installed my Champ legal 16-gallon Jaz cell. Here you can see how I built a box with a hinged lid to contain all of the fuel parts, its nice to be able to flip the lid open and have easy access to everything. ignore the ugly plumbing in this picture, you can see in the next shot I was able to clean it up a lot when I installed my Hydramat and Holley pump and regulator.


Having the fuel inlet in the quarter window area makes it really convenient to fuel. I put a lot of work into getting a good vent system to make sure you can fill the car quickly.

2 hints about going this route.

One you should put the filler on the passenger side, it keeps the fueling away from the driver changes. Also, on most but not all tracks it puts the fuel port on the pit wall side which means you don’t have to carry the jugs as far, but being away from the driver change is really the big thing. If I was in charge, I would make it requirement that all fuel fillers are on the passenger side.

Two, if I was doing it again, I would skip putting Lexan in the quarter windows. I would weld in some thin steel, clean it up and paint it to match the body color. The fuel is hard on the Lexan, it gets cloudy and cracks pretty quickly, after replacing the Lexan twice I ended up relacing half of the window with aluminum. With a driver strapped in wearing a HANS it is not like the quarter windows are of any use anyway. I think it would look good too.

 

Scott, looks like your thread has turned into the generic first gen road racing thread. I will go start my own build thread, and stop spamming yours, especially since I am about to do the unthinkable and install a piston engine.

 

Heresy you say....lol
Yea....didn't mean to highjack this awesome thread...but it is keeping it alive...

Carl:
We run exclusively Lucky Dog ...and some autocross however we don't always do the Portland events. It's our home track and we've all done so many laps there that if we have to drop and event for funding reasons it's the first to go.
We chose to put the filler on the driver side so that we aren't dumping fuel over the hot exhaust. Our tracks in the PNW have pits that put us on both sides of the car so being closer to the pit wasn't a factor.

 

No worries guys. Like to see what you guys are working on

 

So here are some shot of the mid pipe and one of the bends in the mid pipe for my exhaust. It is 304 stainless straights and bends with 409 stainless slip joints. I painted welds with high temp paint because they will eventually rust. You can see the section I have to replace if you enlarge the photo of the mid pipe.

 

This showed up this week. New 3" aluminum drive shaft from Coleman Racing with 1350 u-joints. Its lighter than the steel ones I have been having so many issues with and I wont have to use conversion u-joints which DO NOT WORK. I was able to get a rule change in SCCA STU to allow for aluminum drive shafts so I wont have to disguise this thing with black paint!

 

We used a few slip joints but most was butt-welding. We used a flux paste on the inside instead of back purging but all TIG welded with an "affordable" TIG welder.

 

Also replaced the 3rd and 4th gear Dog Rings in my transmission with turns out is a Hightower and not a Jerico. Apparently when Hightower builds their transmissions they use a Jerico case and main shaft but the gears, sliders and dog rings are unique. Once we figured this out, getting parts from Hightower was easy peasy.

 

Wow...that's sharp. Do you think the issues you've been having are related shocks from being able to quick shift with that awesome gearbox? We've been running the same driveshaft since we started in 2011 and only just started having having a vibration last year...play in ujoints and knocked a weight off. I think we have a similar engine set up to you. We think we're about 200hp....but it was half that before last year with our first engine...we used to go through transmissions like underwear but a few years ago we got one that was marked "race transmission" with sharpie when we bought an old IT-7 chassis and it's been working great since. We also run a stock clutch assembly. I'm just wondering if broken drivetrain components are in our future... I'm assuming that Coleman driveshaft wasn't cheap...I know they make great stuff...most of the front end on My Chevelle is from them...

 

I think the vibration issues I have had are caused by the conversion u-joints I have been using. The conversion u-joints adapts the 1310 u-joint on the 2" drive shaft to the 1350 u-joints on the slip yoke and the rear flange. The drive shaft failure I had in 2019 was a combination of this vibration and the amount of back lash in the drive train. Some of that is inherit in the transmission and some of it was coming from the slip yoke I was using. It was designed to have a certain amount of slop to help with tire spin in NASCAR race cars. The shaft may have also had a defect in the materials used. Either way it twisted in the middle and broke on the 3rd to 4th up shift. The amount of damage it did to the underside of the car was impressive.

I was running the conversion u-joints so that I could use a 1350 Mark Williams slip yoke that is designed for the roller bearing tail shaft bushing in my transmission. I could not find a forged steel 1310 slip yoke with the right dimensions.

I considered a 3" steel drive shaft but that adds so much weight. The aluminum drive shaft addresses all of the issues and is proven solution - Charlie Clark has one in his RX7 behind a Jerico. I have also picked up a tighter fitting Mark Williams slip yoke. The Coleman drive shaft was around $400.

RX7s have a harmonic in the drive line that is hard to get rid of. In my car it has always happened from at around 100MPH. Once I get past that speed the harmonics stop if there are no other issues.

With the stock gear box, keeping a fresh tail shaft bushing is key to making vibrations less of an issue. Pinion angle also mattered I had the best luck with 0 degree pinion angle at ride height. Probably the biggest difference came when I bought a new drive shaft from Mazda. I still have it if you are interested, shoot me a PM.

I think running a stock style clutch is key to keeping a stock RX7 transmission alive. The 5.5" clutch I am using has no slip and really is not designed to be used all the time. Up shifts without using the clutch are much smoother with the Jerico.

 

That's far less expensive for the Colman drive shaft then I'd have guessed. Our vibration was right at around 100mph as well. We'll see how the one I'm having redone works, if it sucks I'll be interested in the one you have. For our car I'm glad to know your issues seem to be related to your specific combination...sucks for you though...

 

Scott,

Do you think that shaft could work with slip yoke to fit a tail housing? I am still saving my pennies for a dog-box but need a new shaft now.

 

Which one?

 

Current set up is a FB case with miata gears. Been using a stock drive shaft. Going to be replacing the bushing and rear seal so would be a good time for a new drive shaft.

 

Hopefully these help. Sorry it took so long...

 

Thanks for the pics. They are definitely helpful. The lexan bulkhead is interesting. I assume visibility is OK out the back?

Thanks again,

Carl

 

Yea, rear visibility is just fine. The only challenge is at times the top of the cell reflects on it...but that's usually only after we've cleaned everything real well...lol

 

Here's an update from......drum roll......an actual race.

First the good news is that I have two finishes in an SCCA Majors race weekend and my car is still able to move under its own power. Something I haven't been able to report in a while. So no broken drive shafts and or suspension components. In fact I have a drive shaft to use moving forward and the car handled really well. The driver needs work.....a lot of work. On occasion I didn't suck completely but the rust is pretty crusty.

There are issues I have to look into, however and should know more once I unload the car. First I need to drain the transmission and look for excessive trash. I am hoping the sound I was hearing is not a bearing going south. I was hearing in when coasting (it was rainy) and it sounded like race brake pad squeal. I don't think I heard it when I accelerating.

I was also seeing very high oil temps in some pretty cool weather that I need to investigate - 230-240 if I ran the car hard. Water was 165-180. I am going to start by testing the mechanical gauge (boil some water and use my tire pyrometer to validate temp) and see what it says. I have gauges, even good gauges, read high in the past. The car wasn't running like it was hot because it was getting down the main straight just fine. So we will see.

If none of the issues are serious, my next race will be in St Louis over the Father's Day weekend. I need one more Majors finish to qualify for the RunOffs and after that I will run 2 Regional Race weekends to finish up with qualifications. But I don't want to count chickens....still in eggs....and all that.

 

Congratulations on the event!! Driving back onto the trailer is always a nice feeling. In my experience noise when coasting tends to be ring&pinion but squealing doesn't sound right for that. I'd be amazed if you actually had high oil temps with two coolers, it must be a gauge issue. We're still having intermittent cooling system issues...


However, our last time out a couple weeks ago we achieved this:

 

Awesome!

 

Oil cooler - engine oil temp postmortem
Tested the gauge using a tire pyrometer (probe type) and some hot water. Determined that the temp gauge is likely not the issue.
Next I pulled apart the coolers and verified several things:

• The coolers are dual pass - there is a baffle between the in and out ports on the coolers
  • These coolers are the no-name ebay OE knock-off coolers that sell for $75-100
• The top cooler was not full of oil
• The bottom cooler was full of oil

The conclusion we reached is that oil was not being distributed evenly between the coolers. The oil coming out of the engine was likely going to the hotter of the two coolers because was the path of least resistance because hotter oil has less viscosity. So once one of the two cooler started performing poorly, that is where most of the oil went.

This phenomenon was confirmed by a friend that has experience with multi-radiator/multi-oil cooling systems on gas-turbine generators. Flow balancing was a constant issue and eventually had to be computer controlled to make it work.

I believe this problem came about because where I am currently splitting the oil lines coming out of the engine. In my latest setup, I am dividing the oil between the two coolers at the input to the top cooler. I went to this design to simplify plumbing. In the past, I had a tee fitting at the engine that split the oil immediately so the viscosity of the oil was a constant. However, this arrangement meant running two separate lines to the coolers.

Currently I am investigating a single cooler solution using an aftermarket cooler from several different companies. The benefits would be an easier installation and use of a cooler from a recognizable source that use known cooler construction. Cost wise, the cooler will be more expensive but plumbing costs will be lower. I'll follow up with the choice I make.


How the two coolers are arranged. Bottom cooler was doing all of the work

The single input line connected to the parrallel plumbing spliter