Arrrrex-8

So today I took the RX8 to an autoX for the first time. I have an issue that I think is one of two things.

I downshifted to 1st at a turn around and stayed in first threw the next few gates, before braking for a very hard left, tighter than a 90 degree turn. I was on the rev limiter for a few seconds before braking. After braking and making the turn I got back on the accelerator, but there was no power. I backed off and tried again, I did this a few times before the power came back. It felt like I was pushing the throttle peddle down but the throttle plate wasn't opening.

I'm thinking either I got fuel starvation and the ECU wouldn't open the throttle plate up until fuel pressure had built back up. Or I some how activated some kind of a limp mode or safe mode, if such a thing exists on our cars, by being on the rev limiter so long. I had two tick marks over a 1/4 tank of fuel, after talking to some other people it sounded like fuel starvation. This is my first throttle by wire car so I'm not used to how it reacts to that, and the people I talked to with other cars with throttle by wire said it sounded like what fuel starvation feels like on their cars. But some one else said they had heard about an RX8 at a prosolo that was banging the limiter at the start line and when they went to take off the car wouldn't go, they made it sound like the same thing I experienced.

Any one know which it is? How much fuel do you guys autoX with?

dannobre

iTrader: (3)

There is no fuel pressure sensor...so there is no way for the ECU to know the pressure.

The left turn high load fuel starvation thing is often a poor pump...that's where you should start. The pump is less than $150....

The other fixes wouldn't be allowed in Autocross class rules.....

There is a limp mode....but unlikely.......

altiain

iTrader: (3)

Sounds like a fuel pump issue. We would typically run the car down to the point where the fuel light came on without starvation while autocrossing, although it seems to need a minimum of a 1/4 tank for sustained left hand sweepers on a road course.

Arrrrex-8

I was just guessing based off of what it felt like. So what is going on then? This feels different than fuel starvation in any other car I've had.

Arrrrex-8

I'll order a new pump.

Can this happen at any fuel level? Is there a fuel level I'm safe at until I get a new pump?

WTBRotary!

iTrader: (6)

im not positive but i remember watching a racing video with racers from Mazda racing a RX-8 and they were saying something about the pressure gets kinda low below 1/4 of a tank, im not positive but thats what i was reading in the subtitles...

swoope

iTrader: (5)

it all depends on lots of factors.

how many miles on the car? what fuel level does it happen at.

have you ever premixed? this has been a bigger issue on track, but correct on the left hand turn..

depending on the fuel pump condition i have had it happen at 3/4 tank, and 1/4 tank..

beers

WTBRotary!

iTrader: (6)

Swoope for another save lol... i dont suppose you can anwser if my anwser was correct or if you know anything about the 8's fuel pressure getting a tad low after 1/4 tank eh?

swoope

iTrader: (5)

if you have never premixed. i would not run below 1/4 tank for anything performance oriented.. below 1/4 tank i can get missfires in a straight line..

there is a slosh factor, in the left handers. if you have a strong pump and a clean sock, should not be a problem.

but i would keep the tank above 1/2 tank and see what it does.

so how many miles. premix or not?

this is stuff we are learning about.. search frankin pump.

beers

peterlemonjello

FWIW, it could be the fuel pump resistor. This part can fail once it gets too hot.

https://www.rx8club.com/showthread.p...+pump+resistor

SilverSurfer

No white smoke coming out of the exhaust, I assume?

KAtC10

I get fuel starvation on hard left handers under 1/4 tank at track.

Razz1

If you had DSC and TC off then its fuel pump.

If you left those on then you hit limp mode.

olddragger

iTrader: (3)

Sounds like fuel starvation. only easy cure is to replace the pump assembly. if you only autocross then it may be a long time before you have a problem again---depends on a lot of factors. if you source one--get the 09 pump assembly---its a denso pump! before 09 it wasnt.
OD

swoope

iTrader: (5)

been there replaced that.. unless you have a turbo sitting near that area or just below. not the likely issue..


beers

olddragger

iTrader: (3)

na --not resistor---it wouldnt be so sudden and recover so quick.
Basically it is a weak oem pump that when stressed by dirty socks/filters, low fuel etc etc--- it gives out. Once symptoms start--it only gets worst.
OD

RK

iTrader: (1)

He should clean the sock first. If it's dirty as hell then it's probably the culprit. If after a cleaning it still causes problems then replace the pump.

Someone (Stealth?) just put a DIY up for cleaning the sock...

Here ---> https://www.rx8club.com/showthread.p...highlight=sock

If it's the regular old fuel starvation issue from big turns then the biggest thing is just to be smoother. If you jerk the car on a turn it'll slosh more. Smoother turning keeps you from getting dry on one side.

EricMeyer

Any Fuel level----YES.


Safe fuel level? As much as you can run.

We've removed these fuel tanks a zillion times to inspect and clean them. Here's the deal, the pickup point for the fuel is on the bottom of the fuel pump on the left side of the car (behind the driver's seat). There is a TINY little screen for debris about as big as a dime. It can become plugged, clogged partially or fully. Fuel pumps by nature are no "pullers", they are "pushers".

If you keep pushing this car at higher rpm's, the motor will starve for fuel and go lean. These engines do not like going lean at WOT. Trust me on this. We have blown several motors using the stock fuel pump with the driver keeping his foot in it.

One of the best things you can do if you ask me is to add a fuel pressure gauge and to log the data. I tell all the Koni RX8 guys to do this. Same for the Lamda Sensor. You have to look at it and therefore you have to RECORD it. This isn't an idiot light that comes on that says "oooh, fuel pressure has dropped". Smart people will look at WHERE and HOW MUCH it drops----this way you know where on the track it is occuring and to what degree. We have experienced this in left-handers, right-handers and even on straights. It depends of where the fuel is in the tank. Sensors are the best insurance for operating your car/engine in a road course environment. The more you add grip and suspenion to your car, the higher the probability that fuel starvation can occur.

As we modified our suspension and added the spec Grand-Am Hoosier grip, much, much heavier spring rate, aggressive bars, etc, the more we experienced fuel starvation and ultimately the car starting going lean and the motors went South. Boom. Again, these Koni cars are built to maximize grip and operate in conditions where you try to use every last drop of fuel before you need to pit for fuel.

Summary: The better road course (can't speak about Auto-X) driver you are and the more your car's suspension has the capacity to go faster, the more likely you are to experience fuel starvation. Logging fuel pressure and A/F will tell you if you are getting this problem much earlier than if you are just waiting for obvious symptoms to occur.

Happy Rotoring

dannobre

iTrader: (3)

Where is this screen? Under the sock inlet?

olddragger

iTrader: (3)

eric is talking about the little sock wwe have.
He is a generious man to inform us of their expensive findings. And he is absoulutely right.
Our pump is not a solid pump(hope the 09 denso is better) and with a poor placement and design for high performance driving.
I have data logged fuel starvation times on my car at Roebling road (i didnt have fuel pressure but my a/f's,tps and load told the story) on a FULL tank of gas--believe it or not.
There are little things you can do as we have spoke about those, but I HOPE the 09 pump will help us.
OD

I8U

iTrader: (1)

Looks like my fuel pump maybe on it's way out. On my last long road trip, I noticed when I drove the car until the low fuel light came on it would just shut off completely. Not cool when looking for a gas station on the interstate cruising 70mph, it did it 2 times on when the fuel level dropped to an 1/8 of a tank. I have since been in an accident and the car is being worked on in TX but I do not have the money right now to buy a new pump and I still have to drive it back to NC once repairs are complete.

Denny or Eric, any advice on my fuel pump issue? I was gonna pull it when I was back in TX but had some trouble pulling off the pump ring. I was gonna clean the sock, actually I was gonna removed the sock all together but whatever. Help?

dannobre

iTrader: (3)

Save yourself the grief and get a new pump

I8U

iTrader: (1)

I was leaning that way, thanks for the input Dan.

EricMeyer

Concur

While your at it, pump out your tank and clean the gook out of it. You would not believe the little crap that ends up in your tank. Sometimes I think the fuel tank elves sneak in our shop at night and put junk in there.

When we ran the stock fuel assembly, we would always carry a spare fuel pump. Don't forget the o-ring. There is a special tool to remove the big white screw on ring that holds the fuel pump in place. You can use a screw driver and a hammer but the tool is the ticket. Tool p/n is in the service manual.

I8U

iTrader: (1)

Believe me Eric, I know all about bringing extra pumps to the track. Remember who I crewed for last year. Looks like I'll be cleaning out the tank once I get it back to from TX. I guess on the drive back I'll just have to keep atleast a 1/4 tank of fuel just so the pump won't have to work as hard.

Eric, any word yet on VIR this month?