Surge tank for early model e30

[s50joe]

I posted this to the r3v Facebook and was asked to post it here to preserve it, so here it is!

I've been trying to figure out a surge tank setup for my early model e30. I didn't want something that went in the trunk because I still drive to the track (i.e. I use the trunk) and I didn't want to have to create a firewall between the trunk and cabin.

I saw a post about putting the 034 Motorsports FP34 surge tank in the stock fuel pump location. Wasn't really able to find many pictures though, so I'm adding mine. Note that you must have the early-model smaller gas tank for this to work. It takes advantage of some of the mounting points already on the car.

This can be accomplished with access to home depot and no special tools. 1.5 inch aluminum bar with a bit of a bend put in it. Then I used a dremel to cut two slits in the aluminum and I cut a slit in the lower factory mount point. Clamps go through the slits, and a piece of 1/4in rubber in between the clamp and surge tank to hopefully cut down on vibration and harmonics. Car won't be possible to start for at least another month or two (engine rebuild) so I won't find out for a bit. The surge tank is definitely oriented a bit towards the front of the car (relative to the bottom support point which is the strongest one) so hopefully it all holds up! Fitment is very tight but it does all fit.

The way I connected this:
-In tank fuel pump goes towards rear of car.
-Fuel pump output is towards rear of car and goes up and cover to the hard line along the frame.
-Fuel return line from engine connects towards the front of the car on one of the lower holes.
-Fuel return to gas tank uses the top-most connector on the surge tank to make sure no air gets trapped in top.

I used a reducer to go from the 12mm fuel line coming from the in-tank pump to the 8mm nipple on the surge tank. The reducer is a little above the surge tank.

I bent some of the fuel hard lines a little so that the rubber hoses routed easier.

Fuel filter was relocated to the front of the car using the fuel filter mount that was used on super early model e30's (I think 318's had them). Hopefully it's not a nightmare to change, I think it'll be okay.

[s50joe]

Here's the fuel filter

[s50joe]

Update: Was at the track this past weekend. I drove my car down to the gas light coming on twice. Never had any fuel starvation.

Edit: Worth noting that the Bosch 044 provided way too much fuel. My fuel pressure was at 60psi when I turned the car on. I ended up using a NOS solid state relay (https://www.holley.com/products/nitr...parts/15620NOS) and a PWM output on my LinkECU. I have it set to 60% duty cycle at 100hz. I originally had it set to 200hz but the SSR would overheat and shut off no matter what duty cycle (even 90% duty cycle would do this). Somewhat weird since it is rated 40amps and up to 1000hz cycle rate. It's been totally stable at 100hz so far though (survived a 2 hour drive to/from the track plus being at the track all day). I am tempted to buy another one to replace this with in case it dies at some point though...

I didn't want to put a higher flow fuel pressure regulator on the car since that's just more aftermarket parts to deal with and a general annoyance to mount. Also was ideal to be able to turn down the flow rate of the fuel pump so I'm hopefully not superheating the fuel.. This pump delivers over 2x the fuel my engine needs. I couldn't find a lower flow fuel pump in this same form factor.

[Panici]

Interesting solution.

Without a heatsink, I would be shocked if that NOS SSR is rated for continuous duty @ 40A.
Perhaps they intended it only for short hits of nitrous with plenty of time to cool down in between?

If you can't get a smaller capacity fuel pump, I would use an aftermarket FPR personally.

[Northern]

Could be FPR flow issue, clogged return line, or maybe just restriction by the return eductor (if Earlies have those?)

[s50joe]

I have no interest in running an aftermarket FPR, just more BS to deal with. The SSR is working fine at 100hz and it will keep fuel pump heat down. Return line isn’t clogged, I found other people on Bimmerforums noting the Bosch 044 overpowers the stock FPR too.