HSV MX5

Angreal · Post by **Angreal** » Wed Oct 03, 2012 8:53 pm

Completely understandable. it was just testing to make sure it was safe right? ,;)

Donovan · Post by **Donovan** » Wed Oct 03, 2012 9:00 pm

Correct. All the major car manufacturers road test their cars before rolling them into production for sale, I was just doing my own bit of testing.

Maybe I can put Test Driver on my CV now.

WideOpenThrottle · Post by **WideOpenThrottle** » Thu Oct 04, 2012 8:30 am

Is 2low2c a certifier or just did whats required for the cert as i have mine booked in with Neil Fraser today at one.

Donovan · Post by **Donovan** » Thu Oct 04, 2012 8:36 am

He just did the work that Neil Frazer pointed out that needed to be done. Neil thought that the steering rack needed to be shimmed to raise the height of it to sort out the bump steer, but 2LOW2C read somewhere that the V8 Roadsters front subframe is based around the NB, so once we put the NB hubs on the car we were all sweet.

Saved me a shed load of $$$ doing that.

WideOpenThrottle · Post by **WideOpenThrottle** » Thu Oct 04, 2012 8:56 am

So was your bump steer caused by any particular mod?

Doh! you must have a different rack eh!

Donovan · Post by **Donovan** » Fri Oct 19, 2012 11:02 am

WideOpenThrottle wrote:So was your bump steer caused by any particular mod?

Doh! you must have a different rack eh!

The bumpsteer was caused at the V8 roadster subframe is all made around the NB measurements, so really need NB hubs to go with it, otherwise your bumbsteer is all out, like it was on mine.

Donovan · Post by **Donovan** » Fri Oct 19, 2012 11:07 am

New springs turned up from 949 Racing, Green is 12kg for the front, black is 8kg for the rears.

don't understand the custom charges, got a 2nd hand set of sport brakes, booster, BMC from a wreckers in the states, all up cost about the same as the springs, and have got pinged GST and all their other bit's and pieces on those. Springs didn't get charged anything???

Donovan · Post by **Donovan** » Wed Oct 24, 2012 9:26 pm

In my hunt to figure out where the fuel fumes are coming into the cabin, I setup the hoist in my barn for the hardtop (only had it sitting around for about a year or more).

Fiddly the first time I went to use it, but I imagine it'll get easier as I figure it all out, and get it lined up a bit better.

Bit freaky working in around the cabin with the hardtop floating over my head, hoping that the thing is going to hold up.

Donovan · Post by **Donovan** » Wed Oct 24, 2012 9:38 pm

So with the hardtop swinging over my head, pulled off top over the fuel pump trying to locate where the fumes are coming from.

Any how, discover this. I figure the 3rd pipe is the breather line for the fuel tank, that now goes no where and is blocked off.

Not sure this is contributing to the problem or not, but if the breather line is blocked, then what is stopping the tank from sucking itself in as the V8 drinks itself silly

na6*dori · Post by **na6*dori** » Thu Oct 25, 2012 7:36 pm

whats it blocked with? could be like the gearbox breathers by the looks

Angreal · Post by **Angreal** » Thu Oct 25, 2012 8:39 pm

It does look like it's venting from the photo. There's lots of dust and then a clear cone extending away from the hose which might indicate it's releasing vapours.

I'm no CSI, but that's how I interpret that photo

dynofiend · Post by **dynofiend** » Fri Oct 26, 2012 1:24 pm

It would be unlikely that Mazda would go to the effort of adding a union and pipe to the tank, only to block it off again. This could very well be the breather. I can already see a send and return line on the pump so it cant really be anything else.

Contrary to belief your tank will probably be under positive pressure with the breather blocked, especially once the car is warm. This might be why you are getting the fumes. With the tank being overpressurised, the vapours might be finding their own way out of the tank and into the cabin.

I would consider replacing the breather, venting the hose down to under the car but ensuring that you use a gravity dependant non return valve (usually a ballbearing in a box arrangement) in case the car rolls. If the valve isnt there, then if the car rolls, fuel can leak out of the breather.

Hope that helps!

Euen · Post by **Euen** » Sat Oct 27, 2012 2:31 pm

As far as I am aware, that round flange that is mounted to the tank contains the gravity non-return valve.

Donovan · Post by **Donovan** » Mon Oct 29, 2012 10:21 am

No, there is another valve, as the pipe out of the tank goes into a one way valve, and then into a line which normally runs to the charcol canister. I have pulled the valve off the NB wreck that I have got, and put it on, and then got a length of hose and have run that under the car and out halfway along at the moment.

I think it has made a difference, but I can't say for sure, because since we actually had a fine weekend, I pulled the hardtop off the car and enjoyed a bit of sun.

I still have fumes in the boot, but not sure whether that is from residual that has soaked into the carpet or not, so going to have to try and air it out.

My other concern is, whether a seal around the pipes for the tank has maybe loosen up with the pressure trying to escape out, and maybe I should look at pulling the pipes off and putting some sort of sealant around them?

WideOpenThrottle · Post by **WideOpenThrottle** » Mon Oct 29, 2012 11:41 am

Some info for you Donovan...may be of help?

On the last pic '7' is the two way check vavle while '8' is the roll-over valve.

WideOpenThrottle · Post by **WideOpenThrottle** » Mon Oct 29, 2012 11:51 am

I think it would pay to re-install the two-way check vavle if its not there?

Donovan · Post by **Donovan** » Mon Oct 29, 2012 4:58 pm

WideOpenThrottle wrote:I think it would pay to re-install the two-way check valve if its not there?

It's number 7, the two way check valve that I shoved in there Friday night, that I pulled out of the NB, but now I am wondering whether it is going to do that much. One of the images you sent thru for the two way valve said to test you need to put vacuum on at either end. Since one end isn't going anywhere other than under the car, there is never going to be vacuum on the point B side in the image. Or does it just mean that it is going to get to a higher pressure in the tank before it starts to vent itself.

When I took the bung out of the pipe that was there, it was hissing away venting until I shoved the valve in, and then it stopped. When I open up the fuel cap, it vents for a good 5 or 6 secs, is that normal, or should it just be a short fizzz.

WideOpenThrottle · Post by **WideOpenThrottle** » Mon Oct 29, 2012 5:17 pm

From memory all the cars i have ever owned made a noise when i opened the petrol cap.They all definately suck in air when opened,so to be honest none of this really makes sense as you would think that these valves/breathers etc would maintain the same pressure in the tank to what was outside rather than to be always in negative pressure.
Like i have said before,mine does not have the charcoal cannister but still retains as far as i know the two vavles and i never smell petrol at anytime!
Unlike when my fuel lines werent connected to the fuel rail while i was still rebuilding.
So you may still have minor pressure leak or your garage is like an oven???
As an aside..you got your cert plate off Neil yet?..still waiting to hear about mine.

Donovan · Post by **Donovan** » Mon Oct 29, 2012 8:47 pm

It wasn't so much the noise when opening up the petrol cap, just the length it went on for seemed longer than normal. Guess I just need to pay more attention to it the next time I go to fill up.

No, haven't got the plate yet, have to drop around and pick it up from him. Drop him a text or email and ask him if he has it, that's what I did in the end.

dynofiend · Post by **dynofiend** » Tue Oct 30, 2012 7:50 pm

Nah guys your getting the system's purpose mixed up. So sealed fuel systems are a 'relatively' new invention. Their purpose is pretty much solely to reduce the emission of Hydrocarbons (HCs) into the atmosphere from evaporating fuel. The 'breather' tube allows vapours (which are created as fuel simply warms slightly, from either atmospheric temp or the effect of the exhaust and transmission) to travel forward, usually through a gravity valve (and in this case a one way valve). They are then allowed into the inlet manifold and harmlessly burnt off. There is often a solenoid to allow this movement of vapour into the manifold, so the system is only active when the engine is running. The action of this solenoid can, and often does, create a slight vacuum in the fuel system, hence the hiss when you open the filler cap. When the solenoid is closed, the vapours can still escape, but this time escape through the charcoal cannister which neutralises some or most of the HCs. In either state of operation, the fuel tank is never under higher than atmospheric pressure.

When you block off the breather tube, you will nearly always create a high pressure in the fuel tank, as the vapours have nowhere to go. This will still result in a hiss when you take off the fuel filler cap, but this time of air and vapour escaping. Under pressure, there is, as you have found, a good chance that the vapour finds its own way out, and into the cabin.

Note with a blocked breather you may also create a vacuum in the tank if alot of fuel is being used, so you might occasionally still get an 'inward' hiss taking off the fuel filler.

Either way, the best bet is not to remove the breather system. The second best bet, if you have to remove it, is to vent it to the outside of the car, taking care to incorporate the gravity cut off valve. In this state the one way valve would probably be optional.

WOT your car will just have the breather venting to atmosphere which (although not ideal) is still fine. It will also, as you point out, tend to create a vacuum in the tank, again that's fine.

Donovans car has a blocked breather which can and is creating high pressure in the tank, which is bad.

Note that sometimes this fluctuation in high/low pressure in cars that have blocked breathers, can affect fuelling of the car. I would have thought the FPR would have fixed this, but apparently not!

Hope this helps!

WideOpenThrottle · Post by **WideOpenThrottle** » Tue Oct 30, 2012 7:58 pm

That makes sense to have a fuel tank under slight negative pressure as this would also lesson the potential for fire/explosion as the outside air is always trying to get in rather than fuel/fuel vapour trying to get out?

Donovan · Post by **Donovan** » Wed Oct 31, 2012 8:51 am

When you say the one way valve would be optional, are you talking about item 7 in the image, so basically just hooking the hose up to the exit on the top of the tank and running the line out of the car?

dynofiend · Post by **dynofiend** » Wed Oct 31, 2012 8:10 pm

Donovan wrote:When you say the one way valve would be optional, are you talking about item 7 in the image, so basically just hooking the hose up to the exit on the top of the tank and running the line out of the car?

Yup, providing that item 7 is the oneway valve of course. Ive no idea if it is!

Donovan · Post by **Donovan** » Wed Oct 31, 2012 8:42 pm

Suppose I can give that a go, might make for a smelly garage

dynofiend · Post by **dynofiend** » Wed Oct 31, 2012 9:19 pm

Yeah it will a little, although with or without the valve youre getting the same effect.

Theres always the option of salvaging a charcoal filter from another 5 and just using that in conjunction with your breather tube.

For what it's worth, my 5 doesnt have a charcoal filter and just an open breather, and I dont get any fumes in my garage, or in the car for that matter.

HSV MX5

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