Good deal, keep us posted. I wouldn't think it's was 7", wow.
Good deal, keep us posted. I wouldn't think it's was 7", wow.
lhintze wrote: Good deal, keep us posted. I wouldn't think it's was 7", wow.
That's what she said!
It's true. Extreme applications where you're going to see lots of combined forward and lateral acceleration (left turns especially) will need a bit of planning to prevent fuel starvation issues on anything below a half tank. On fast tracks like Road Atlanta, XP-5 hasn't had any issues as long as we keep 5+ gallons in the tank. The XXXocet's testing is extreme, as their tighter track means they're in 2nd gear coming out of corners rather than 3rd or 4th at Road Atlanta. With good rubber, these V8 cars are capable of sustained longitudinal accelerations exceeding 1.2g in 2nd and in some cases 3rd gear. That's the same as tilting your fuel tank back 50°.
The position of the Miata fuel pickup installed in an Exocet is nearly identical to that of a fuel cell.
Anti-slosh foam, internal trap sumps, or external sumps are all measures to reduce fuel starvation. Most fast (<7 lbs/hp) race cars have a low pressure pump from the cell into a smaller external sump (2-to-3 liters). This sump also usually gets the return flow from the pressure regulator. As a reminder, these cars are beyond fast and are firmly sitting in the "stupid/unnecessarily fast" bracket. XP-5 with a driver is 3.6 lbs/hp, the XXXocet is 3.8. That's a better power/weight than a top-trim Radical SR8 LM, the highest-boost RS200 racecars, an healthily over the current crop of hypercars such as the P1, 918, and LaFerrari.
Theoretically, installing the Miata tank backwards would help under acceleration.
icaneat50eggs wrote: Papa I've been doing research on the rotrex for my miata, do you have a build thread anywhere? Was it a kit?
I don't have a build thread but can offer some advice.
I used a Kraftwerks kit which I was mostly pleased with. I had the car up and running exactly 1 week from receiving the kit using only what was included in the kit.
The piggy back fuel controller is crap, it always ran massively rich so never made the full 190BHP+ advertised.
The included recirc / blow off valve is plastic crap that does not hold boost. I replaced mine with a quality item and there was a noticeable improvement in throttle response and a seat of the pants increase in power.
Other than that I really like what a Rotrex does. Throttle response is fantastic and the build of power and torque is lovely to control. It is a cliched response but it is like driving a fast responding 2L rather than a forced induction 1.8L. I think it is going to suit the Exocet brilliantly.
Transferring the kit to an Exocet is not without its challenges. My only choice of location for mounting the intercooler means that it is unlikely I will be able to use any of the supplied piping and I also need to package in the oil cooler for the supercharger.
I will be fixing the fueling issue with a proper standalone ECU (just my laziness and budget prevented me doing it before). I have got a TDR crank overlay which will up the boost quite a bit to.
Keith Tanner wrote: You'll need just as much fan at slow speeds as you would on a Miata, I would think. We did find that the turbo XP2 cooled much better on track than a similar Miata, probably due to the complete lack of pressure buildup in the engine bay. So at speed, I'd expect a lot less fan to be required.
Thank you for the response.
Did you find that the car over cools on track or when moving on the road? Are you running a different thermostat to combat this?
XP-3/4 had/has a thermostat. Standard Miata thermostat, roundabouts 192°F. Over-cooling shouldn't be a problem with a functional thermostat.
XP-2 was actually a budget-build naturally-aspirated UK-chassis car, the green car Exomotive sent Keith was XP-3. XP-4 has XP-3's FM2 turbo guts now.
There's no such thing as overcooling if you have a thermostat.
We fixed the fuel starvation on the XXXocet. First step was to relocate the fuel return so it hoses into what remains of the sump - with the stock in-tank FPR removed, the previous return was just dumping from fairly high up. This was something I learned on an endurance racing car that could deal with the long left turns 1 and 2 at Thunderhill with 0.25 gallons on board.
Secondly, we increased the height of the internal baffles in the tank by riveting in a three sided box. Back in testing, with 1-2 gallons in the tank it was just fine. Before we were getting starvation behavior with a nearly full tank. We didn't try less than the 1-2 gallon level.
Before, we were seeing fuel pressures drop mid-corner on a steady throttle. It might have been enough to stumble a four-cylinder - but the fact that our engine takes a massive gulp of fuel on tip-in exaggerated the problem.
FYI, we built a fuel cell car a while back with Hoosiers and a 525 hp LS3. No problems with pressure drop, the pickup was in a small box that has hinged flaps to encourage fuel to get in but not out and the return plumbed into the box.
Any special reason why people run on such low fuel? I have always run my events on a full tank to avoid any semblance of this kind of issue.
Weight.
not as if the tank holds a huge amount of fuel. 30 pounds of weight behind the back tires is well worth the traction tradeoff.
It's not always practical or conenient to fill up between sessions at a track day, nor is there lots of space in an Exocet to tote big fuel cans to the track.
Exactly. Having to run high fuel levels is a workaround for a problem. Better to fix the problem. On the enduro car, we needed the ability to stretch out a stint sometimes, and there was no point in carrying fuel we couldn't use.
On the XXXocet, it was manifesting itself with a surprisingly full tank so something had to be done.
BTW, this tank orientation was shared with the Catfish until the most recent frames. They're still not at full Miata angles, but the rear mounts are now about 2" higher than the fronts so it's a start.
Don't let me steal the thunder from Keith, but here's a repost from FM's Facebook page:
All happy, ready for delivery! It'll be at the Mitty this weekend.
Looking good! My June/July delivery date is getting closer, and the suspense is killing me
I purchased wheels recently for my Exocet, Braid Fullrace Maxlight available through Paul at Braid USA. These are flowcast 15x8, 0 offset wheels from a company with a strong competition heritage. I was interested in something durable for use on track and these fit the bill. My set are on order to arrive in 4-6 weeks in titanium grey. I'll get full specs and detailed pics when they arrive but wanted to let you know that there are high performance options for wheels for the Exocet.
I keep hearing " I would daily drive my Exocet...." I actually did 160 miles in traffic as a daily this week including 7AM to 8AM bumper to bumper grid lock. Sunglasses and short windshield. What I learned is everyone loves it, no matter how E36 M3ty your work day is your in a great mood by the time you get home and medium sized rocks at 70 mph hurt. Just thought I would share.
wawazat wrote: I purchased wheels recently for my Exocet, Braid Fullrace Maxlight available through Paul at Braid USA. These are flowcast 15x8, 0 offset wheels from a company with a strong competition heritage.
16.5 lbs? $300 each? Dang!
linuxd00d wrote:wawazat wrote: I purchased wheels recently for my Exocet, Braid Fullrace Maxlight available through Paul at Braid USA. These are flowcast 15x8, 0 offset wheels from a company with a strong competition heritage.16.5 lbs? $300 each? Dang!
That was also my reaction after looking them up. 2-3 times as much and 2lbs heavier than the actual weight of holeshots.
The Holeshots are flow formed as well. But hey, to each their own!
What are these "Holeshots" you speak of?
teamilluminata wrote: What are these "Holeshots" you speak of?
Traklite wheels, the ones that Exomotive sells on their site.
These are Holshots. Exomotive is a distributer.
I see. I thought as much.
Exomotive are currently adding the BRAID wheels to their site. They said they needed something to offer their customers who wanted a higher quality option. The BRAIDs are a proper competition wheel that is probably stiffer and stronger than the Tracklite but consequently more expensive. Sometimes (most) you get what you pay for. www.braidusa.com
What's the scoop on carbon bodywork and cost? Saw the Instagram post
Dietcoke wrote: What's the scoop on carbon bodywork and cost? Saw the Instagram post
$2400 upgrade on top of kit price from facebook post.
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