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Gbs Baffled Tank & Fuel Surge


brumster
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Question - is anyone else using a GBS baffled/race tank here?

 

Bit of background : when I bought my kit 2nd hand there was no fuel tank included. I went up to GBS and was chatting with Keith as were going round picking out the various parts I needed to complete the car, and on the fuel tank discussion he suggested their new baffled tank, aimed at race use, as it wouldn't give me problems with fuel surge. Now I am very savvy with fuel surge myself, having dealt with it in another car via the swirl pot route, so the idea of having a baffled tank was great... it's a road car primarily, and the whole concept of fitting two fuel pumps and a swirl pot is a ridiculous amount of faffage for a car that, if the bits were just designed properly in the first place, shouldn't be necessary (yes, my Exmo made perfectly fine without one, just with some forethought to fuel tank modification).

 

So 4 years down the line the car is complete, I go for a drive, and noticed that even on over half a tank of fuel, gentle turning round a roundabout is causing fuel starvation. Brim the tank; problem goes away.

 

To be quite honest, I am properly annoyed about it. The car is now fully built up under the illusion everything was "done proper" but maybe that just shows naivity on my part for assuming the tank was baffled rather than actually checking it before fitting it. Either way, to swap the tank now is going to be a right bloody ballache and involve ripping the back of the car off, which I'm not really all enthused to do at all. At the end of the day I'm referencing a conversation in person with someone 4 years ago and can't really prove one way or another what was said.

 

Am I right in thinking there is no such thing as a baffled race fuel tank from GBS and, for whatever reason (let's call it a misunderstanding for now) I just have a standard tank with no attempt at baffling off the fuel pickup? If there is such a thing as a baffled tank, how would you spot it (now that's got me thinking, presumably you'd see some weld marks on the side of the tank where the internal baffling was attached, and I kick myself because I'm not sure I recall seeing any of these on the tank, although I didn't look particularly closely)....?

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I got a custom one made up after the faff of dealing with the GBS standard tank and MX5 sender unit always leaking. It was baffled and you can clearly see the HAZ from welding. Also the length of the aluminium you can clearly see some ribbing over the unit. And it definitely felt more study than the GBS standard tank.

I'd be having GBS fit the new tank FOC but really wouldn't feel comfortable about their workmanship in doing so.....Double check your invoice to see what was stated on that and compare to their "standard" tank.

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I dug the invoice out and (bearing in mind it's 2013) it's itemised as "Fuel Tank Sport Zero 27lts" and roughly in line with price on Kitspares. Seems suspiciously in line with the current supplied fuel tanks which means either (i) they never did a race/baffled tank anyway or (ii) I paid for and received a standard tank? Or (iii) they adopted the baffled tank as the standard one at some point, and they only list that tank now anyway.

 

or maybe their idea of "baffling" is a different concept to mine, and they welded some little flange somewhere in there and said "right, there you go, baffled! sell it!"....?!

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I wonder if there's some tank sponge that could be inserted into just the left hand side of the tank, where the pickup is, without interfering with the right-hand side where the swing-style fuel sender is?

Other option is to swap the fuel sender for a vertical-style enclosed type, then I can fill the tank with tank foam cubes.

 

Actually that latter idea is probably the simplest, prettiest and easiest, thinking about it....

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So there’s no swirl pot in the tank? Is the fuel pick up a hard pipe that just dips down in to the tank. In this case can you add a long length of flexible nylon pipe on to the end of the tube so that it bends around and sits against the bottom of the tank. I did this on my fuel pickup before I was running injection so that the maximum amount of fuel could be drawn out of the tank. I added a small mesh filter on the end just to make sure no debris got picked up.

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So there’s no swirl pot in the tank? Is the fuel pick up a hard pipe that just dips down in to the tank. In this case can you add a long length of flexible nylon pipe on to the end of the tube so that it bends around and sits against the bottom of the tank. I did this on my fuel pickup before I was running injection so that the maximum amount of fuel could be drawn out of the tank. I added a small mesh filter on the end just to make sure no debris got picked up.

 

Unfortunately the take-off is on the front lower edge of the tank, on the left hand side. I suspect it's just a straight join in to the tank (assumption was with some sort of baffling around the outlet but clearly that's the bit up for debate)....

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It doesn’t seem feasible that with half a tank of fuel, an outlet on the front corner would become exposed to air. Where is the return fuel fed back in to the tank – anywhere near the outlet?

 

It's on the same side, but directly above, at the top of the tank. I wouldn't say "near", really, it's like 200mm above it.

 

I'm fairly sure it's fuel starvation because when it happens, my SPA dash raises an alert/alarm warning and shows me the fuel pressure (which drops quickly from it's normal 42psi)....!

Edited by brumster
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There only seems to be one type of fuel tank on the Kit Spares website, and it has this description:

 

'Complete with six hole boss baffled and swagged inlet'

 

...which is not clear if it means the whole tank or not.

 

The option of a baffled tank was never mentioned when I bought my bits in 2015....you could retrofit the swirl pot and pumps? If you do, get the swirl pot of eBay - I paid £30 for mine rather than the £90 GBS charge...

 

BTW, you said this happens when going round a roundabout? The fuel pickups are on the left-hand side of the tank (looking from the rear of the car) so going round a roundabout should push all the fuel up against that side of the tank and you shouldn't have a problem, no? Left turns would be a problem as all the fuel will slosh over to the right side of the tank, away from the pickups (or have I got my physics wrong?).

Edited by nelmo
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Thanks Nelmo, that's interesting and useful info. I agree, "six hole boss baffled and swaged inlet" can be read many ways, I figured it meant :

- six hole boss (for sender)

- baffled (the tank)

- swaged inlet (for the fuel filler neck)

 

As to what else "baffled" could refer to, well.... I'm baffled myself! I was thinking/hoping that the lack of 2 tank models on their website implied that they had standardised on the baffled tank across the range (not a bad idea)....

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Ooo blimey, I wouldn't have thought so? It's rather suspiciously only happening on the exit of roundabouts and left-handers. The inlet and outlet are a fair distance apart, the height of the tank, which I think is ~200mm. And it's not happening on full power on the rolling road, or in a straight line, etc. which if it was just the fuel falling out of the return directly above the outlet, and that causing aeration in the tank, I'd have thought it dissipated pretty quickly or otherwise the time it takes for that to build up in the fuel pulled from the tank would take a little longer than is happening here. I mean, it's pretty easy to reproduce, and I honestly mean it when I say I'm just driving at normal, entirely moderate and appropriate road speeds! It's not like I'm railing it round in order for it to happen :) honest guv!

 

GBS have got back to me, I need to speak to them this avo....

 

My thoughts at the moment are :

- Get a vertical sender

- Make a 5-hole to 6-hole adapter plate to mount it

- Fill the tank with sponge

Edited by brumster
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I remember from when I was doing all my kit bits, GBS had a "Standard" tank and "Sport" tank where the difference seemed to be a sender boss and baffles on the "sport".

I shall double check from my *bleep*ised standard tank currently in my garden scrap pile but I am very very confident of it not being baffled (which tbf was expected hence my swirl pot set up)

Foam would be my option and force the sizeable cubes down the filler neck. Although I'm sure that method was disagreed with at some point......?

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Foam would be my option and force the sizeable cubes down the filler neck. Although I'm sure that method was disagreed with at some point......?

 

I would agree with you. There's a time and a place for a swirl pot and all the associated extra piping and fuel pumps but this isn't it.

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