^ yeah and I still have no brakes :(

Wait...its track season all year here.

there are many cars with u shaped gas tanks, how do they get away from the problem? i have never seen the oe pump pickup point, is there anyway to change or extend it

^I've tried looking through the service manual, but it appears the fuel pump just sits in the tank and picks up the fuel directly. I'm amazed there isn't a hose from the pump that snakes around the tank bottom.

If one could hook up a hose to the pump inlet, a series of float ball-valves in a rigid tube along the bottom would solve the problem. Think of a long horizontal PVC pipe (but PVC may not be fuel system appropriate) with holes in the top. At each hole would be a floating ball in a small 'cage'. If the fuel level has the pipe submerged, all the balls would float and the entire pipe would be used for fuel pickup. If you turn hard with a low fuel level, any exposed ball-valves would close and seal (ball would seat in the pipe without the fuel for buoyancy) and the pipe would use any open ball valves (portions submerged in fuel) for inflow.

Chris, makes sense... look these guys up and ask for my bud Tony Lisa PATENT IT! - The Law Offices of Steven G. Lisa, Ltd. - Patent Procurement, Enforcement, Licensing & Litigation

they do IP for racing applications... quick before someone takes your idea! :tup:

Thanks. I sent them an email. Who knows if my idea even works though. Yet another project to undertake during a vacation!

I'd happily take no credit or financial gain for the idea if someone was able to make it work. And maybe provide a finished product for me too... :)

I had a little time today. It looks to me the problem lies in the design of the fuel tank. Since the fuel tank is U shape and the fuel pump is on the right side, it makes sense that we get cut out on hard right hander as all the fuel jumps to the left side. I don't know if Nissan installed a baffle plate inside the tank. If they did, they have a hole drilled too big or too low and therefore allow the fuel to leak to the left side. The simple fix would be to drill additional holes that are smaller at a higher location and put a one way fuel check valve in the stock location. If they didn't have one in, it wouldn't surprise me if they come up with a new gas tank design in the 2011 cars. Cars like RX-7 had done the same thing in the past during the mid-year upgrade.

http://www.courtesyparts.com/images/z34/z34_172-1.gif

This issue is very...interesting.

I've been tracking my RSX-S consistently for 3 years now at the Autobahn (IL), Gingerman (MI), and will be at Road America (WI) this summer. I raced it with just an intake, struts & shocks at first. Then I got sways & braces. Finally I got SS lines, pads, and 550F brake fluids.

Even before the brake modifications, I never had my brake pedal go down to the floor or anything like other drivers. I also never had fuel starvation issues I believe. Sure, I ran out of gas quick, but I went WOT a lot (esp with only an NA 2.0).

From what I've been gathering, the Z not only needs an oil cooler, but now also has gas starvation issues? I plan on getting a Z down the road and tracking it, so this is not good news...

I would also upgrade the brake fluid tho and from the sound of it start with Stillen sways (and eventually get KWv3s)

200HP vs 300HP, big difference

I have been tracking my Z34 since new (May 2009) and hav not had fuel starvation. The circuit that is hardest on the car is Philip Island where T1 is a lift-dab and turn-in at 210kph followed by 5 seconds WOT to the brakingpoint for T2 - and even with the tank at <50% full have never had the engine stumble. T3 is flat in 5th to the left - same deal.

T7 (Lukey Heights) is a firm brake, downshift to 4th and hold near peak revs in a rising left-hander that crests and fall away from you .. again, no fuel-related stumble (but I have spun as the suspension goes lght and unloads which is "interesting").

The corner coming onto the straight is WOT in 5th turning to the left and again, I have never had a fuel-realted stumble.

My Z34 is RHD (as we drive on the correct side of the road in Oz - a bit unusual but we like it) but I am sure that this is not material.

It is true that I usually drive at track days on the top half of the tank, but I have certainly run the tank down to 30% full with fuel starvation.

Is the filler nozzle still on the RH side in the Oz spec cars?

Phillip Island is mostly left handers so with the fuel pickup on the right those aren't a problem. T1 might not give you problems as the radius isn't super tight hence the duration isn't that long. You need to be fully loaded turning right at close to 1G for a few seconds to experience the problem. The higher the G load the quicker it happens. With slicks on I can only get down about 2 dots before I'll start having issues on some tracks.

Agree, at the limit T1 at Philips should produce fuel starvation... do you have a way to measure lateral G-loading? also, are you simply coasting from t1 to t2?

other than that, the only two right handers are essentially hairpins, neither of which should cause fuel starvation... do they have any clockwise sessions there? then you'd really get to experience all the fun you've been missing... haha

http://www.phillipislandcircuit.com....circuitmap.jpg

T1 in a Z34 is just a lift, turn in and back to WOT. I have data logging from my race car which shows 1.3G lateral (this car runs 290/625R16 Dunlop SS12 slicks) and a guess for the Zed with Dunlop Direzza's whould be around 65% of what the race car sees - so it will be close to 1G, but wouldn;t be over it.

The fuel pickup is in the same spot, so maybe I'm just lucky with the circuits I run on here.

Not applicable for the topic

The turn is too short, you need a continue radius

Some thoughts on the clutch pedal issue. I don't know if this has been resolved or not but the clutch pedal sticking to the floor was a common problem on certain types of muscle car clutches in the 60's. These clutches would essentially go "over center" when fully released and the G forces generated within the clutch at high revs pinned the clutch in the released position. One solution was to install a travel limiter to prevent the over center condition. Unfortunately such a simple solution doesn't seem to apply in this case.

Since my Z is an A7 I can't confirm my theory but I'll put it out for discussion anyway. Many clutch systems have an assist spring on the clutch pedal assembly, if the Z has such a spring we may have a possible answer to the mystery. The assist spring assembly is typically laid out to push the pedal to the floor in the second half of its travel and lift the pedal off the floor in the first half of travel. In this environment if the clutch fluid were to boil the pedal would stick to the floor when depressed. So addressing the overheating clutch fluid might solve the problem.

i had one experience with fuel starvation this summer. it was at shannonville motor sports park. It was near my 3rd 20 min session. It was between turns 2 and 3. The 2 turns are usually taken together as a single turn at a speed of about 70 or 80 km/h in second gear at about 60 or 70% throttle. Fuel was about quarter of a tank, so 4 dots. As I was between the 2 turns, I lost all drive to the wheels and the engine went down to idle. The car coasted to a stop on the short straight right after turn 3 and the engine just wouldn't rev past idle. I thought it was limp mode but my oil temp was ok. Also limp mode cuts rpm at 5000. Tried shuffling through the gears but the car still wouldn't rev past idle. A couple of cars went right past me at high speed and I was in full panic mode. Eventually after a few seconds I managed to creep onto the grass at the side of the track. After a few seconds of pumping the throttle the engine finally came back to life. Fuel gauge was showing only 2 dots.

Then on that same lap at the hairpin (turn 10) I also experienced the same thing. This is a slow high-g hairpin taken in 2nd gear at 40-50 km/k and exits into a very long straight, so you floor the throttle as soon as you exit. At the exit of the hairpin I floored the throttle and experienced no acceleration for about 3-4 seconds before the car finally responded again. I pulled into the pits after this lap, and slowly after a few minutes the fuel gauge went back up from 2 to 4 dots again. I let the car cool down and then went home.

Here is the track map:

http://www.trackpedia.com/mediawiki/...ville_full.gif

looks like a fun track! even CCW, you'd get fuel starvation through 6-5 etc... i think you're going to have to carry 3/4 or more of a tank from now on at that track

I have found out today that fuel starvation isn't a problem at Road Atlanta while it's raining heavily.

hahaha!!!

but the slick surfaces exaggerate handling weakness and I think I am in serious need of some more front downforce. The front was really light, causing me to slip and slide quite a bit. It didn't feel so bad to me or the instructor in the car, even though he could tell I was driving on the edge, but two other instructors told him we were sliding all over the place. I couldn't keep up with the modern Bimmers and Audis, but I was slightly faster than the two C6s.

functional splitter/canards? or a big fat lump of metal bolted to the front :p

some clarification... front was losing traction at low speeds, high speeds, or both? during hard transitions or high-g but lower-rate transitions? during braking or stable front-rear load?

Time to buy a second wing and mount it on the hood. Who cares if our cars aren't FWD? It just looks cool.

On a more serious note, could the front tires have been hydroplaning? How much tread do you have left up there?

http://forums.pelicanparts.com/uploa...1248450156.jpg

plenty of tread,Yoko AD-08s. Mostly coming out of turns going uphill, low speeds on wet track while accelerating. Fronts would lose grip first, then the whole car would slip a bit. Just seems odd that I couldn't corner as fast as a 330i.

I've never experienced this problem in the dry, I think that if I pushed it harder on the dry than I do, it would happen there too, its just the wet track amplified everything.

process of elimination...

sounds like not a tire issue... can't remember what width you run front and rear... I'm running a square setup, so obviously I get more relative front traction than most setups... assuming yours are not overly staggered and that your front tires were in as good condition as the rears... if so, we can rule out the tires themselves... that is, unless you have something weird going on with tire pressures

didn't occur during braking, so those are out

we can rule out the rear diff

so that leaves setup or driver

on driver... this is a low speed (mechanical grip) corner... you're an experienced driver, so I'm sure you're all over this, but have you tried different ways of entering and exiting that corner? wet tracks = slower in, later apex, more gradual acceleration... and of course when you accelerate you will be transferring weight off the fronts and onto the rears, which brings me to setup

on setup... thing #1 is to disconnect the sway bars in *hard* rain... an old racer trick someone shared with me that tends to alleviate a lot of the twitchiness in the chassis on a wet track...

also, can't remember which coilovers you have... how much adjustability do you have? what are the spring rates you are running front and rear? if you are having this issue of understeer in dry weather as well (you said it was amplified in rain), especially on an uphill exit (where the front *should* have LOADS of traction), then you might think about going up 2K in rear spring rate and before then even try adding some compression (bound) stiffness the rear dampers... and/or maybe take out a few clicks of compression stiffness in front... I always have to remind myself, one change at a time :)

finally, post up your caster/camber/toe settings on front and rear, if you like and we can comment on those and how they might be playing in... only if that's helpful

others more knowledgeable than me can expand on what might be going on with your setup... also, read these

Effect of Suspension Changes - trackHQ.com - Track Day HPDE W2W Club Racing Time Attack Motorsport Forum
Front anti-roll bar stiffness and understeer? - Corner-Carvers Forums

And final question... please tell us what your tire temps are if you are collecting those (inner, middle, outer) and if there are any obvious wear patterns on the front tires

Tires are 255/295 when I run streets. I thought about the rear sway, but today is gonna dry up. I'm running tein monoflex, but I'm unsure of the rates. Have all shocks set at middle of adjustment range

if you need a quick fix for today...

-2 psi from front tires ***
+2 clicks of compression rear suspension
-2 clicks of compression front suspension

Make sure you have EXACTLY the same suspension settings left and right... count the clicks with precision

Personally, I think you're not running enough front tire... Try using 275/295 next time... or 275/305

If the track is dry, you could also try adding in 1 stop of firmness to rear sway, if you're not there already

*** PSI needs to be evaluated based upon pyrometer readings front and rear... see if you can borrow one from someone at the track and take readings immediately after a session - then come back here and post

I would agree with Travis's analysis, you have a very larger stagger at 40mm and that differential is going to be amplified in the wet as you find the limit of traction much sooner.

In the wet I run the shocks well towards the soft side. I think you'll find that in the wet that the stock suspension setup is pretty good and you should try and emulate it as close as possible to enhance feel. The extra bit of body roll is actually very useful in the wet in that it enhances weight transfer and traction.

Well, it was too wet this morning to run at all. I did just two laps but there was water flowing everywhere. Track is dry now, so 3 good sessions this afternoon. These are my street tires, normally I'm square too

You need to get a GoPro HD, Mike. I want some videos.

I have one, just need to use it some time!!!! :D bought it a year ago, but never got around to playing with it.

As for my issues, the last 3 sessions were dry and the car went back to performing the way it normally does and it was a thoroughly enjoyable afternoon. I wasn't getting passed nearly as much as I was in the wet. I think I only had to let two cars by actually.

The AD08s are probably not as good as you want it to be in the rain.

poor track conditions are an opportune moment to diagnose setup... if you found problems in the wet, and if you can solve them there, I suspect you will benefit in the dry with better times and a more stable car... I went through something like this over the last few months while doing track days with a broken ABS system... opened my eyes big time to pad selection and setup (corner balance, front/rear compression, etc)... and now that I have gotten it dialed in to work without ABS everything is that much better now that ABS is back working

very true, but hopefully, I won't have the wet to work with for a while. its so much more fun dry!

Cossie, the AD-08s are definitely better than my R1s in the rain. I could get rain spec tires, but I'm not that serious. I'm actually thinking of getting AD-8s for my track wheels next. They are a little more than the R1s, but they will last three times as long and get me within a second or two. I don't do time trials, so it really doesn't matter when it comes down to it.

And actually they perform so close to an R compound, its fun to tell people I am on street tires when we talk in the paddocks

Get RA1s if you can, awesome tire in rain and they last for the life of the tire. They are quicker than your AD08, about a second or so.