Fuel tank mod

[ForcedFirebird]

I'm not sure why, but most of the FL and SE spece30 guys have still had starvation issues with hydramat and/or dual fuel pumps. The silver bullet quite simply is a surge tank and a resilient lift pump inside the stock fuel tank.

It was ALL of us e30 guys lol, not just SE, or even Spec (we have it in Champcar). Typically long right handers, like T1 & 16 at SIR, T1 and t12 at RA etc.

We had the same issue when we were campaigning the e36.

[Digitalwave]

I'm not sure why, but most of the FL and SE spece30 guys have still had starvation issues with hydramat and/or dual fuel pumps. The silver bullet quite simply is a surge tank and a resilient lift pump inside the stock fuel tank.

[ForcedFirebird]

Interesting you all are having trouble. I have run the 2 pumps in-tank for literally 60,000 race miles and haven't had any issues. Even before the hydramat was a thing, I could pull all but about a quart of fuel out of the tank. With the hydramat, you get it all - it will leave maybe half a cup before it shuts off.

I use OE replacement fuel pumps by bosch or siemens in the original hangers on both sides, now with hydramat as well.

I, and several others have had the driver side pump fail from being dry. In fact, had a renter in one of the cars who left the pump switch on when both sides of the saddle were empty (he was being towed in for another issue), and I had to replace BOTH in tank pumps before we could go back to racing.

[redneckvtek]

Interesting you all are having trouble. I have run the 2 pumps in-tank for literally 60,000 race miles and haven't had any issues. Even before the hydramat was a thing, I could pull all but about a quart of fuel out of the tank. With the hydramat, you get it all - it will leave maybe half a cup before it shuts off.

I use OE replacement fuel pumps by bosch or siemens in the original hangers on both sides, now with hydramat as well.

[ForcedFirebird]

"How do you know?" Lol.

The return from the surge tank... I presume that has an internal extension that feeds from the top so it draws the air out first? Also, it T's in with the return from the fuel rail before returning to main tank? Where's the filter now?

Filter is in the engine bay, just before the fuel rail.

No internal extension. The surge tank is very simple, it's a "surge tank" lol. Just a tank with 4 spigots/barbs.

Fuel travel like this (this is all your connections):

In tank lift pump>surge tank> external fuel pump>fuel filter>fuel rail>surge tank (from fuel rail regulator)>main tank.

All this does is store the fuel that's returning from the engine, before sending it back to the main tank, making it available immediately.

I'll repeat that the engine does NOT use as much fuel as it returns. Even at full throttle, full load, there's a LOT of fuel still leaving the rail.

So, to capitalize on this, by lifting the fuel from the main tank to the surge tank (swirl pot), while also returning the discarded fuel from the fuel rail, that surge tank will never go empty, unless the main tank is empty.

No air is trapped since the return line in the main tank is open to atmosphere. The surge tank doesn't hold any "pressure" since the return from the surge is the same return to the main tank, all the fuel rail pressure is held between the external pump and fuel rail.

...and yes, to test it, I ran it until the red light came on, pushed two more laps and was dead in the water. Completely dry. There's a sticker on the cluster says "RED Light = EMPTY". If we come in when the red light comes on, we can fit three 5 gal jugs in a 16.6gal late model tank. With the 180whp engine we would go 1hr 45min, with the backup junkyard m20 we can make right to 2hr.

[hoveringuy]

Found a pic of the last e36 I did. The pump and surge tank are strapped together, and strapped to the stock filter mount, the e30 is done very similar. The three connections on bottom are stock supply and return, the one that loops goes to the bottom of the inline pump. Top of the pump goes to the fuel rail, fuel rail return goes to the top of the surge tank. That surge tank never empties, and you have to be careful using these, you get NO warning that you are about to run out. The car will just instantly shut off and you'll have to wait to be towed in. Don't need to ask me how I know lol.

"How do you know?" Lol.

That's a nice setup. As a reformed helicopter pilot I absolutely hate any extra fuel lines in the cabin I don't need. I once had a 1" line burst during hot refueling. I literally had JP-5 in my high voltage switching box, it looked like a fish bowl, I shit you negatively.

The return from the surge tank... I presume that has an internal extension that feeds from the top so it draws the air out first? Also, it T's in with the return from the fuel rail before returning to main tank? Where's the filter now?

Also, for everyone's amusement, here's a very recent weekend chasing a 944 Turbo. I apexed a tad early and overshot the curbing, didn't think too much of it, except by re-entering so shallow both of my inner wheel barrels impacted the FIA edge and bent them.

https://youtu.be/1-XoYNPuJC0

[ForcedFirebird]

Found a pic of the last e36 I did. The pump and surge tank are strapped together, and strapped to the stock filter mount, the e30 is done very similar. The three connections on bottom are stock supply and return, the one that loops goes to the bottom of the inline pump. Top of the pump goes to the fuel rail, fuel rail return goes to the top of the surge tank. That surge tank never empties, and you have to be careful using these, you get NO warning that you are about to run out. The car will just instantly shut off and you'll have to wait to be towed in. Don't need to ask me how I know lol.

[ForcedFirebird]

Surge tank or a fuel cell with a built in surge tank is really the only viable option to fix the issue once and for all.

If you move to a surge tank you should consider changing the in-tank lift pump to a low pressure lift pump that is OK with being starved, less you burn up the intake pump. I chose the DWMicro pump for that purpose.

I agree 100%. We went through all these "fixes" in this thread in the enduro cars, and ultimately the one that worked the best is a small surge tank and just a single stock in tank pump, and an external inline pump between the surge and engine. The surge tank only needs to be about .5l, since the surge tank itself won't starve, even if the in tank pump aerates, due to the fact that the engine returns more than it uses at the fuel rail.

A 3" piece of aluminum tube with caps welded on the ends works perfect and can go under the car, near the filter location in e30's (mentioned at the beginning of the thread). This also makes easy access to all 4 connections needed. I've made a bunch of them. On e36's I put then inside the driver frame rail, at the front of the hard lines, next to the steering shaft.

[Digitalwave]

Surge tank or a fuel cell with a built in surge tank is really the only viable option to fix the issue once and for all.

If you move to a surge tank you should consider changing the in-tank lift pump to a low pressure lift pump that is OK with being starved, less you burn up the intake pump. I chose the DWMicro pump for that purpose.

[hoveringuy]

Another update... This setup works great until it doesn't. My second pump failed, probably because it ran dry.
I was running two high pressure pumps in parallel, looks like that's not a solution because I underestimated how much it would be running dry.

I'll be doing surge tank.

[hoveringuy]

Update: I was finally able to put some track mileage on this setup and it works. Got down to around 5 gallons with zero issues. I have a button on my console that activates the second pump, that button is only active if the main pump is already on so both pumps will shut down if the engine stops turning for safety. I would normally get issues with less than about 9 gallons remaining, and I have confidence this would work fine all he way down to a gallon or two remaining.

The only issue I've had with this setup is that if I activate the second pump in normal freeway cruising with less than 1/2 tank it will effectively move all the fuel to the right (just like the jet pump) and the pump will run itself dry.

[hoveringuy]

Can you explain your sender isolation issue? The OEM fitment of that sender on the passenger side requires no heat shrink, fiber or nylon washers?

I only run the passenger side sender and use the early "eta" fuel gauge to compensate.

Using an early gauge and one sender is one solution.

The stock dual-sender solution on the late model tanks is electrically isolated on the driver side because the two senders are connected in series and letting the driver side sender be grounded would short the signal path. The element in the sender is electrically bonded to the metal flange.

I don't know if this a "better" solution or not.

[ForcedFirebird]

The in-tank swirl pot is a decent rig, but if fuel capacity is an issue like endurance racing, then you are using up precious space. Throughout the years we have had all kinds of variations for starvation and we eventually settled on an external tank (.5l) in the spare tire well that uses an external pump to the engine, and a single stock pump in the tank. The dual pump system works great for heat races, but we found when in a long endurance race, the pumps would seem to burn out prematurely and often. We gathered that the pumps were getting hot when running low on fuel.

The dual pump setup will make your fuel gauge malfunction. The early tanks (and 318) have a single sender, so the fuel gauge needs to be swapped out for one with correct resistance - otherwise the car will read 1/2 when full and empty when empty. The 318 pump hanger already has a return in it (late model 325 return is in the bottom of the tank near the filter).

[redneckvtek]

Can you explain your sender isolation issue? The OEM fitment of that sender on the passenger side requires no heat shrink, fiber or nylon washers?

I only run the passenger side sender and use the early "eta" fuel gauge to compensate.

[hoveringuy]

Here's my final interpretation of the requirement. It's a Walbro GSS430 pump and a Holley 3x8 Hydromat sock. I have the level sender insulated from the body by enlarging the inlet with a die grinder by a few mm and up-sizing the O-ring a bit. The studs have heat shrink over them, plus a fiber washer on the bottom and nylon on top. Resistance between the sender and the tank is 1 megaohm.

I'll very likely have this pump on a separate switch for "track mode".