After taking the car out with my brother to the 5 mile loop at Thunderhill Eastnd and hitting a fuel cut, I was confident that the car was hitting limp mode due to oil temps getting too high. It happened on the main straight, which now that I recall was right after a sharp right hander, hold that thought for later. The oil gauge was up at 245F, basically pointing straight up, and the power cut for several seconds, while I had roaring track junkies fast approaching behind me. I stick my hand out to point them by and try to figure out what's going on.
So I drive out to ButtonWillow to meet up with a friend. I wasn't planning on driving the car on track due to this "oil cooler issue", but since they didn't allow me to ride passenger with him on his first session, I figured I might as well get to experience the course a bit, even if I'm not pushing it. Alhamdulillah during my chill laps the car did fine, but of course, as soon as I started pushing it, I started hitting the fuel cut. When I glanced over at the oil temp gauge, to my surprise the oil temps were still quite low, as low as 180F - 200F. I normally autocross at oil temps of 220F without issue, so what could possibly be going on? I had no clue, until I woke up this morning with an Aha! moment. I recalled that I filled up the tank shortly after leaving the track on the way home, adding around 15 gallons. Which means I was at less than a quarter tank by the time I got to the Kettleman City gas station just a few miles out from the track.
sleeping brain was buffering and loading that memory to output it to me upon waking up, subhanAllah.
On my second and last session of the day, I immediately hit that fuel cut after the first right hander on my second lap and pulled off to the side, as the engine shut off completely and the power didn't kick back on after some time as it had in the past. I checked the battery terminals again to be sure it wasn't that again, I started the engine and it fired right up, alhamdulillah. What in the world? Oil temp must have been at 190F this time. I finished that lap and ended my session early, keeping it very light as I had to drive several hours back home. So it's not the battery, it's not the oil temp, what could it be?
On that last session, there were around 4 dots lit up on the fuel gauge, corresponding to about a quarter tank. I didn't connect this at the time to the fuel cut. But this morning, I don't know where it came from, I didn't even dream about this, but as soon as I got out of bed my mind was flooded with thoughts of fuel starvation. The sensation felt strangely familiar, and I had some flashbacks of that harsh power cutoff happening in the S2K. You're feeling all these G's gripping, pulling hard through a turn and then out of nowhere, the power is just gone, it's like a kick in the opposite direcion of travel. Perhaps my
So I pull up the googles, and type in '370z low fuel cut', and found a plethora of threads matching 370z and fuel starvation show up. It looks like some folks back in 2012 were experiencing this problem and worked on solving it back then, all the way through developing a packaged solution for the issue!
What's the issue? Commonly occuring on hard right hand 'sweepers', 370z's face fuel starvation due to the fuel pump and pickup being located on the right side of the fuel tank. Simply, the fuel sloshes to the left, the fuel pump on the right dries up, and bam, fuel cut! Although there happens to be a cool mechanism already in place which regularly moves fuel from the left side of the tank to the right side, the rate is too slow to counteract this issue on a hard right turn in a track scenario.
The fix? This guy phunk on the 370z forums developed a custom solution using a special version of a Walbro 255 pump, https://cj-motorsports.com/products/cjm-road-race-pump-370z. The secondary pump is installed on the left side of the fuel tank, and is fed by the OEM fuel pump. This secondary pump stays holds a reservoir of fuel so it always has fuel on hand to send directly to the engine. Any excess fuel is constantly returned back to the OEM fuel pump to prevent it from running dry. It's a very elegant solution to the fuel starvatino issue in the 370Z.
However, at $1k and with my current track day frequency, I'll be sure to simply top off the fuel for now. A full tank should get me through a full 20 minute session while remaining well above 3/4 tank which seems to be the danger zone for fuel starvation. This "RRP" does, however allow the fuel level to get as low as having the low fuel warning light on, while still avoiding starvation. Sounds awesome for long sessions, actual races, and also for reducing the amount of fuel weight carried in the car. Given the Z34's behemoth 19 gallon fuel tank, keeping the fuel level at FULL instead of 1/4 tank means carrying an additional 90 lbs of weight! But keeping the passenger seat empty might accomplish the same thing :).
I found another solution for the same problem made by a company called Radium engineering. It looks to be a very similar setup, but it's a bit cheaper ($750 vs. $1k) and they have really nice diagrams about how the system works: http://www.radiumauto.com/Fuel-Hanger-Surge-Tank-Nissan-370Z-P1730.aspx like this one:
Here are the forum links for the "Fuel Starvation Control Project" by user 'phunk' aka 'CJ Motorsports'
http://www.the370z.com/track-autocross-drifting-dragstrip/54724-fuel-starvation-control-product.html
So where do I stand after all this? The answer to the question, can I track my 370Z is still unknown?
Do I need an oil cooler for a full 20-minute hard-driving track session? Yes.
Do I need an oil cooler for 1 or 2 hot laps in a longer session? Maybe.
Do I need a full tank of gas and nothing less than 3/4 tank of gas whenver right hand turns are involved? Definitely.
I know these aren't huge issues, alhamdulillah, but they are hindrances in actually racing and driving fast. Coming from the effortless experiences of driving a Miata and S2000 on the track, it's surprising to have these issues in a mostly stock sports car. I'm used to the simple recipe of: put good brakes and tires on car. Put gas in car. Drive car fast; Car can be driven typically be driven harder than the driver skill allows. That recipe has not translated so well to the Z quite yet. I have yet to explore my skill limits on the car on track, as I discover and resolve these tricky power-cut issues. First I thought it was oil, then it was legit a loose battery connection due to the lack of a proper battery tiedown (while running an Optima battery upgrade, now resolved), and now it's fuel. Maintaining oil temps will still very likely be a big part of the overall trackability of the car, but at least with a full tank of gas I expect to get in at least a handful of laps on a mild weather day without any issues whatsoever. That's the next goal inshaAllah.
On the other hand, it's worth mentioning that I have been able to confidently drive the car hard during autocross, alhamdulillah. Perhaps it's due to many left handers, the lack of long sweepers, the many quick transitions that happen, or the simple fact that I may have even shown up with more gas since the events tend to be closer, but I have thankfully been able to drive the car hard with confidence on a typical autox course. With the exception of the SpeedSF autox, where some serious tail sliding was involved, leading me to discover the loosening battery connections, the car has pleasantly surprised me every single time during autox. It has SO MUCH MO POWA BABAY than the S2K I was autox'ing before. It has ALL the Low End Torque I sought, for days, compared to the F22C frequently falling out of its VTEC range on a tight corner. The RE71R's at these sizes provide phenomenal grip and they transition very smoothly into slip on the course mA. Really, I've had a blast at every autoX with this car. Given that low-end torque + good handling were what sparked me to switch from the S2K to the 370Z, the car has delivered superbly in that regard aH. It's also way more comfortable to drive out long distances to track events (although the suspension could be dialed in a bit more to avoid rubbing). Heated seats switched on during the long drive home? Yes please.
One thing I noticed about J's RSX however, was that aside from the incredible grip the car had, the chassis felt very balanced and tight. From the passenger seat, I could hardly feel any body roll, and in fact I could hardly keep myself planted in the seat. I tightly gripped both the oh sh*t handle with my right hand and the seat bolster with my left, just to stay in place while the car shoved me from side to side with it's ridiculous grip on 255 AZENIS RT615K's on all 4 corners. The 2-way adjustable coilovers felt very stiff but not too bouncy and I'm sure those Polyurethane motor mounts helped. But overall the handling, road feedback, and sharp steering reminded me of the S2K, whereas the 370Z did feel a bit numb in comparison. It's probably all that extra weight, which makes for a smoother ride on the road, but really reduces the driving feel on the track.
At the end of the day it's all about the fun you're having, and with the Z, I've had the most fun putting down banging autocross times alhamdulillah and doing some mean tail slides in the process! :).
So what I see for the Z is more of the same. More autocross fun, and I'll give a mild weather, full-tank track day a shot soon as well iA.
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