The Roadster NA Journey Begins

[Magpie]

No

The fuel level was fine in all the runs and there is no correlation between G forces and dips. I may check for correlation between TPS and pressure dips.

Swapping out the pump/sock/filter on the weekend. Will also change the dash programming to trigger a warning for low fuel pressure to monitor it for the moment.

Have also thought about installing a fuel cell in the boot, especially if the area of where the spare tyre goes is removed... Would also require a change in the exhaust direction, but as suggested by The American it could utilise some of the space occupied by the current fuel tank and be given a side exhaust. This would lower the center of gravity and move some weight towards the rear of the car.

Time to experiment on the shell again.

[Trackphotos]

Just make sure the exhaust exits right, sound monitors at Lakeside and Mt cotton are on driver's left ;)

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[MattR]

Or put one of those spinny mufflers just at the end of the exhaust manifold......

I hear they quieten down exhaust noise pretty well......

[Magpie]

Waiting for the OFFICAL WTAC rules to be released, but believe that the OEM fuel tank must remain AND in its OEM position. Also having a 20ltr 'surge' tank in the boot is also not possible....

So no changes to be done, may still consider bringing the exhaust straight back (with appropriate noise control).

Did have a good look at the fuel pressure and made some custom pages to see the engine's health at a glance.

Car Health by Eipeip, on Flickr

[MattR]

If the pressure drop is caused by surge, and you already haven't, it would be very well worth your while putting a surge pot in, 2 litres is more than big enough. Also if you haven't already done so, get appropriate E85 compatible foam and throw that in the tank, it will also control surge in the tank and it is a good safety measure, ask me how I know.......

[Magpie]

Not sure if surge, however good suggestions. Agree on the foam, you are the second person to suggest it...

[Magpie]

Summer and shed should not be used together!

Changed the pump and filter out. Could not get a new filter sock in time so had to reuse the old one. Pump has been in the car for almost 3 years, filter was changed about 18 months ago. Getting the injectors cleaned next week. This will give a new baseline for the fuel system, if it still has the loss of pressure will have to start looking at other areas.

Been awhile since the hatch has been removed
DSCN4011 by Eipeip, on Flickr

Area cleaned up, hoses marked and clamped.
DSCN4012 by Eipeip, on Flickr

Old pump
DSCN4018 by Eipeip, on Flickr

Sock, a bit 'dirty'
DSCN4020 by Eipeip, on Flickr

New pump ready to go back in
DSCN4023 by Eipeip, on Flickr

Sock a bit cleaner
DSCN4024 by Eipeip, on Flickr

DSCN4025 by Eipeip, on Flickr

Inside the tank. a bit of 'crap'
DSCN4030 by Eipeip, on Flickr

Reason why the sock needs to be in a certain orientation
DSCN4031 by Eipeip, on Flickr

From the old filter
DSCN4034 by Eipeip, on Flickr

[Magpie]

What a hot weekend, stop working in the shed when could not find where I had placed tools not 5 mins later. Shed recorded almost 46° most of the day. BOM has Amberley at 42.3° at 1430 and 39.8° at 1200

Only got half the work planned done...

1. Remove injectors - done. However dropping a spacer added to the job duration
2. Do wheel measurements to find a 15x8 rim that fits the NB8B. Yes 6UL's fit and the Advanti Racing from MX5Parts fit, but looking at BC Racing ones - Done.
3. Investigate rubbing passenger side front. Done, need to lengthen shock length after 18/02 track day
4. Install 'normal' muffler as QR does not have noise restrictions - done
5. Fix up splitter level - not done
6. Done a general inspection underneath and around the car prior to next track day - not done

However did do some unplanned jobs:

1. Removed vacuum lines as booster no longer installed. Need to order some bungs to blank off the holes.
2. Installed vacuum line into air box for future testing purposes. This line was previously used to monitor brake booster vacuum.

The offending spacer. Tess and I spent almost 30 mins looking for it, was just about to take the splitter and undertray off and spotted it.
DSCN4046 by Eipeip, on Flickr

DSCN4042 by Eipeip, on Flickr

It is made of aluminium so could not use a magnet to fish it out
DSCN4047 by Eipeip, on Flickr

But a nifty little hook worked. I would not make a surgeon
DSCN4049 by Eipeip, on Flickr

Injectors removed, vacuum lines still installed. These were a 'pain' to remove due to restricted space.
DSCN4051 by Eipeip, on Flickr

Ended up taking the throttle bracket off to get to the last of the vacuum lines
DSCN4050 by Eipeip, on Flickr

Out and ready for cleaning
DSCN4052 by Eipeip, on Flickr

All covered waiting...
DSCN4053 by Eipeip, on Flickr

Inside passenger wheel well, more than likely rubbing caused by alignment (negative camber). Will reset damper length next weekend
DSCN4054 by Eipeip, on Flickr

DSCN4055 by Eipeip, on Flickr

[Magpie]

A little more data analysis, shows that as injector duty cycle increased, the fuel pressure dropped off. This would suggest that the pump was not capable of suppling the required pressure at the higher duty cycle or the fuel pressure regulator is failing.

Inj DC by Eipeip, on Flickr

The joys of data analysis. At 20 psi fuel pressure and 71% duty cycle there was never going to be sufficient fuel.

[Magpie]

Had a look back at 2016, and it would appear that the 'issue' started just before WTAC. Only change was the car's tune was tweaked...

A check of other tunes shows that the fuel pressure type has always been MAP reference, despite the fact that it is not hooked up to the MAP. Whilst it should be set as constant the fact that it has remained at this setting is irrelevant. Will check with the tuner if this should be put to constant.

FP 2016 by Eipeip, on Flickr

Setting the engine protection to 'stop' any future instances
PS1000_Engine_Protection by Eipeip, on Flickr

[Trackphotos]

Interesting that it's gone so long undetected. Long as it's ok for Saturday ;)

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[Magpie]

To be honest I was not looking for it, there was not an obvious loss of power like there was at Lakeside. With hindsight it could explain why on average, I did my best times early and very rarely at the end of a day in the later half of last year. Now I have made it something to keep an eye on.

Should be OK for Saturday, however going to pull the data after each session to review it just in case.

[MattR]

Wow, 20psi seems low for an injected car, I was more used to 60psi with the standard 280zx injectors on my old bus.

I would be looking at upgrading the fuel pump and running a return line if not already, plus a surge tank setup.

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[Magpie]

MattR it is a return system, with a constant pressure, that is fuel pressure regulator is not a rising rate one. The Walbro 255 is more than enough to supply both the required fuel and pressure.

The car has always been setup at around 40 PSI of fuel pressure, this matches the injectors. The injectors are ID725's and the duty cycle never exceeds about 72% so there is no need to increase the fuel pressure.

Thoughts

1. set the fuel pressure to a base of 45psi. This matches the PS1000 setting for base fuel pressure. This can be done by adjusting the regulator with the pump running but the car off.
2. attach a hose to the FPR and blank it off. This will ensure it remains at a constant pressure and not be affected by any change in pressure.
3. have a spare FPR on Saturday just in case
4. surge tank? Maybe an overkill, unless can install one that also takes a Walbro 255 pump(s) as it saves on spares. This may solve the problem if the in tank pump starts to fail, however will not know about a pending failure until it happens...
5. set a dash warning and enable engine protection that includes fuel pressure. This removes the drivers decision to ignore issue...
6. happy to consider other thoughts/suggestions

[MattR]

For a surge system, I would use a low pressure high volume lift pump to the surge tank then the high pressure pump from the surge tank to engine. Filter between main tank and surge tank, plus filter between surge tank and high pressure pump.

For the return line there are two schools of thought, return to main tank to let the fuel cool down, or to surge tank. Also run return line from surge to main tank.

Another advantage is you can run a lot less fuel. As an example the old zed without surge tank, but a one litre truck fuel filter to act as surge tank I needed to run a minimum of 25 litres of fuel, even on a hill climb, with the surge pot, could run 5 litres for a hill climb with no surge at all.


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