surge tanks?

sclay115 · Post by **sclay115** » Sun Nov 27, 2005 9:43 am

i'm looking to convert my triple weber'd 240z to an injected motor...and i've seen diagrams online using the stock fuel tank with a low pressure pump that loads up a small aluminum tank that then has a high pressure pump that moves fuel to the rail, and then the return line that sends fuel back to the tank, but not the gas tank, the surge tank. but here is a diagram of what i'm talking about, as i'm sure it's confusing, me trying to explain it...but is this a viable option for a conversion? or should i just get new fittings on my tank brazed on, or get a cell...or what do you think...?

http://www.sdsefi.com/techsurge.htm

steve

elansprint · Post by **elansprint** » Sun Nov 27, 2005 12:08 pm

Steve if the car is injected from new there is usually a swirl pot incorporated in the fuel tank to stop fuel surge & loss of fuel under hard cornering. I would suggest you plumb as per diagram & fit a swirl pot & hp pump engine end. See the following for swirl pot.

www.nfauto.co.uk

Ian

sclay115 · Post by **sclay115** » Sun Nov 27, 2005 2:50 pm

so that's a pretty good setup then? it just looks a little 'out there' for me, and i thought it was just some thrown together design, but i was reading up on the Z car forum, and a user has the same setup running an RB26DETT with it, so i'm pretty sure it can handle my comparitively light fuel load....but thanks for the info.

steve

sclay115 · Post by **sclay115** » Sun Nov 27, 2005 2:57 pm

oh and GREAT website! that is some awesome stuff on there, all the little things you never think about when building a car....too bad they are in the UK, nice to see international shipping though...anyone know of a place like that in the states?

steve

elansprint · Post by **elansprint** » Mon Nov 28, 2005 10:09 am

Steve this saves having to get at the tank & underside etc & the 240Z pump should easily keep the swirl pot topped up. If you looked at the website i am in build with the ferrari P4 on there & am using this set up for the cosworth turbo engine

Ian

Matt Cramer · Post by **Matt Cramer** » Mon Nov 28, 2005 10:17 am

Would the fuel tank and high pressure pumps from an injected 280Z fit in your 240Z?

I don't have the option of using a baffled tank for my Dart, at least not without spending a lot of money. I also didn't have many tools to build my own surge tank. So I'm using a trick that I learned on this forum. Here's a website about using a spin-on filter for a surge tank.

jayroc · Post by **jayroc** » Mon Dec 05, 2005 11:59 pm

I have a surge tank on my previously carbed 84 rx7.
The regulator returns to the surge tank, but the surge tank also has a return line going back to the tank. It works well for me.

sperry · Post by **sperry** » Wed Aug 09, 2006 7:43 am

I made my surge tank out of a small oxygen bottle and just tapped and sealed the fittings and never saw a drop of gas!
you could use a propane bottle from autozone or something but make sure you fill it up with water before you pop the saftey valve out
total project cost wil be 10 bucks for bottle and fittings

renns · Post by **renns** » Wed Aug 09, 2006 8:04 am

I'm running a surge tank in my '79 rx-7, but I wouldn't go that route if I had to start over. The system complexity, number of hoses, connections, second pump, etc. is needlessly complex.

What I would do if I were starting over, is to modify my existing fuel tank to accomodate a conventional in-tank pump. Others have done this by cutting out the mounting flange from a tank at the wreckers, and having it welded to the top of the existing tank. This allows dropping a standard fuel pump assembly down into the tank. A small slosh pot is added inside the tank to surround the pickup to prevent starvation when cornering at 1/4 tank. Now you've got an 'oem' type installation, with a simple supply and return line to plumb up to the engine. Boy, just talking about it makes me want to go out and mod my tank...

Did the 280z's use an in-tank pump? If so, you might look at swapping in a tank from that model. BTW, love the 240's. I owned three of them years ago. They biodegraded very quickly in the Canadian climate, but were lots of fun till the frame rails let go!

Roger.

jonfx4com · Post by **jonfx4com** » Wed Aug 09, 2006 2:45 pm

I tried a facet gold top low pressure fuel pump to fill a surge tank before the HP fuel pump and it was a hopeless case. The flow rate of the HP pump was way higher than the LP pump and the surge tank was empty within seconds of the HP pump running up. Result was a dead HP pump. You need to look at the flow rating of the LP pump and compare it with the flow rate of the HP pump when its holding 43PSI. The calculation is surprising, you will need a hell of a LP pump to keep up with the HP unit. I suggest you mod the tank and fit an in tank unit, it will save you lots a grief later in my experience.

If you look here
http://www.fuelsystem.co.uk/new_page_8.htm

you will see that my HP pump holds 3 BAR at around 3 litres a minute but a facet competition LP fuel pump can only pump 35 Gals / Hour which is 2.6 Litres / Minute. Result is an empty swirl pot!
I suppose if you find a BIG LP pump it can be made to work but then your paying money to bodge the job when less money will do it right.

Jon

Jon

renns · Post by **renns** » Wed Aug 09, 2006 2:49 pm

jonfx4com wrote:I tried a facet gold top low pressure fuel pump to fill a surge tank before the HP fuel pump and it was a hopeless case. The flow rate of the HP pump was way higher than the LP pump and the surge tank was empty within seconds of the HP pump running up. Result was a dead HP pump.

Jon,

How was your return connected? If your return line from the regulator also goes back to the surge tank, then the low pressure pump only needs to provide the fuel consumed by the engine. Any fuel not consumed is returned for the efi pump to send through again.

Roger.

jonfx4com · Post by **jonfx4com** » Wed Aug 09, 2006 2:51 pm

And before anyone tells me that in

http://www.sdsefi.com/techsurge.htm

the fuel bleeding out of the fuel pressure reg is going back into the swirl pot- forget it! After 5 mins in traffic the recirculating fuel gets so hot it starts vaporizing in the lines, its a bad solution which I fell for when I saw a similar drawing on another website. I suppose you could add a fuel cooler but then you're buying 2 fuel pumps a swirl pot and a fuel cooler to save you doing it right!

Jon

renns · Post by **renns** » Wed Aug 09, 2006 2:57 pm

jonfx4com wrote:And before anyone tells me that...

Too late!

I've recently installed a fuel pressure transducer on the pressure line, and will be datalogging fuel pressure during my runs at higher boost levels. This will hopefully allow me to spot any fuel system inadequacies before damage is done.

I'll agree with you though, as I said earlier, converting the fuel tank to a modern efi-type setup would certainly be my preferred route if I were to start over again. I doubt it's any more work than fab'ing and installing a surge tank.

jonfx4com · Post by **jonfx4com** » Wed Aug 09, 2006 2:57 pm

Hi Roger,

yes that was how I killed my first HP pump, they don't like pumpimg scalding hot fuel and vapour much, in fact they quickly refuse to do it anymore! I dont doubt that there are folks out there getting away with it but I could not recomend it to someone setting up a new system after already costing myself a small fortune trying the "shortcut methods".

Jon

simonbos · Post by **simonbos** » Wed Aug 09, 2006 7:20 pm

I killed a couple of pumps as well trying to get the surge tank to work. Eventually I just cut a hole in the top of my fuel tank and used a Honda Civic in-tank pump with a custom top plate (I needed it to be rectangular).

Cheers,
Simon

cosmo1stgen · Post by **cosmo1stgen** » Wed Aug 09, 2006 7:34 pm

I also have a surge tank in my 85 previously carbed RX-7 (seems to be a few 1st gen rotor heads in this thread

). When I first got the car running I didnt have one and the car would buck and surge like crazy 1st trip around the block. Only took a week before I decided to put one in and I used the same info off of sds website. Im running a large carter pump to fill the surge tank and have the return from the regulator going back to the surge tank. The carter pump is kinda loud for me though but its been going for 4 years and I drive the car every day so I havent touched it. Now im thinking about doing what a buddy of mine did and switch to a bosch volvo FI pump to fill the surge tank much quiter.

PSIG · Post by **PSIG** » Wed Aug 09, 2006 10:25 pm

jonfx4com wrote:And before anyone tells me that in ...

There are inconsistencies in your setup to get multiple symptoms like you are describing. Surge and header tank systems were developed to solve problems like these - not create them. The troubles you describe indicate it was not set up following the sdsefi (or other proven system) diagram.

I am not promoting surge and header tanks over any other delivery system. There are many benefits to them, but they must be done correctly, such as when they are used in the racing and aviation fields. They are not a "shortcut" when properly applied.

David

eliotmansfield · Post by **eliotmansfield** » Thu Aug 10, 2006 1:38 am

Renns, what sensor did you use for the fuel pressure monitoring? - has some cheap honeywell sensors come back out?

To see how the professionals deal with surge tanks, here's the insides of a Subaru WRC surge tank. It has two bosch 044 motosport pumps and a couple of delco lift pumps

http://homepages.nildram.co.uk/~eliotmez/liftpump1.jpg
http://homepages.nildram.co.uk/~eliotmez/liftpump2.jpg
http://homepages.nildram.co.uk/~eliotmez/liftpump3.jpg

mitsuko · Post by **mitsuko** » Thu Aug 10, 2006 1:56 am

Speaking of surge tanks .

I've never been able to source the electrical isolated
connector to feed 12V to the pump inside .
I had to machine it myself .

Pat

eliotmansfield · Post by **eliotmansfield** » Thu Aug 10, 2006 3:46 am

Here's the connector:
http://www.deutsch.co.uk/corporate/defa ... er_ftc.asp

or go to root of site, product search, enter nothing, press search, scroll down to autosport range.