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What is the fuel capacity on a 1987 325is? This is the old style tank with two fuel pumps. I’m trying to do some mileage calculations for the enduro, and I know there are some enduro experts here.
I know it differs on all tracks, but what is the general fuel usage of a SE30 being driven hard? I will be running the enduro at Sebring, long, flat and fast. Is the car likely to run 1.5 hours without gas? That’s where I will need it to be.
Thanks again.
-Scott
I think the small tanks are 14 gallon or so. I will have to ask Pappy about the fuel burn. He has it in lbs/lap at Mid-Ohio or lbs/minute.
Edit: Just called him and he said 0.8 lbs per minute on average. OR, we expect to burn 35 lbs for a 45 minute race. This counts the warm up lap and cool down lap and all the rest are hot, non FCY laps. The two don’t add up to exactly the same but are close.
odds are it won’t run at all without gas 
early tank is 55L (14.5 gal) but it all depends on how low your car can go without fuel starvation. some can run on vapors, some start to cut out at half a tank. my guess is you’ll burn about 7.5 gal/hr at sebring.
During the enduro days Fred and I would do 3hr races with one refueling in our early model. But a 3hr race is really a 2:45 once out lap, cool down lap and 5min refuel are accounted for.
A genuine 90min stint would have required an additional gallon of gas beyond our ~82min stints. That would have been cutting it close. Might be do-able. I’d estimate we had ~1gal still in the tank when we came in.
An 87 should have a 55L tank. Starting with 9/87 production a 63L tank was used. Visible clues as to the tank are the presence of a cross-over tube on the bottom of the tank and only the hole in the top of the tank on the right hand side for the 55L tank.
Based on a year’s worth of experience in NASA 3-hour enduros, how long you can drive a Spec E30 before having to pit for fuel are a function of the driver and track. If the conditions are such that the car will be at WOT and above 4500 most of the time fuel consumption might be as high as 4-4.5lb every five minutes. But more likely, at enduro speeds, it will be about 3.5-4lb every five minutes. That translates to a range of 10 to 12 gallons in 90 minutes.
If the fuel system is operating properly you should be able to get 90 minutes of run time out of the 55L tank before starvation in right hand corners becomes a serious problem. That means a tank that is squeaky clean (preferably cleaned and sealed) with new OE pumps. At 90 minutes the tank will still have about 5-6 gallons in it.
My experience is that the 63L tank, in the stock configuration starves sooner and worse. That kind of makes sense given how the system works. Unlike the 55L tank the later system relies on a siphon to lift fuel from the left side of the tank, which in turn relies on returning fuel from the engine bay. Starve the pump (on the right side) and there is little to no flow to operate the siphon, thus a snowball effect.
A surge tank would help, but the best fix I’ve found is to use a 63L tank with a low pressure transfer pump on the left side and a late model 318is high pressure pump on the right side. The transfer pump lifts fuel from that side and drops it into the pickup cup where the high pressure pump is. I have essentially that system on the 38 and can run it down to 3 gallons (~115 minutes) before mild starvation occurs.
You can, with either tank. puff the tank with compressed air and get another half gallon or so of capacity.
Scott,
I’ve been talking with Van Epps on this topic lately and he has me using 8 to 9 Gal/hr and says running on a single fuel pump tank is about an hour of drive time on track. With the dual fuel pumps, you can get 12 gals of racing so figure 75-90 mins with 90 mins being tops.
Hmm. Its going to be close. We are going to fill it to the top and run 1.5 hour stints. I’ll let you all know how it goes. I have the two fuel pumps and a crossover tube on the bottom, so its a 14.5 gallon tank. When the enduro is done, I’ll post any thoughts and findings for others.
IE sells an accumulator for the early tank. I don’t know much about it. I don’t think its spec legal and I haven’t done more than glance over the enduro rules. I think it mounts in line near the external pump. Says it’s sold out but I would give them a call.
http://www.iemotorsport.com/bmw/E30-fuel-intake/e30fuelacc.html
[quote=“turbo329is” post=62386]IE sells an accumulator for the early tank. I don’t know much about it. I don’t think its spec legal and I haven’t done more than glance over the enduro rules. I think it mounts in line near the external pump. Says it’s sold out but I would give them a call.
http://www.iemotorsport.com/bmw/E30-fuel-intake/e30fuelacc.html[/quote]
I have been told this is the way to go for the early tank for enduro’s. I know someone who is running this exact setup and says its the only way to run more than an hour on an early setup if you want to run more than an hour.
Good luck Scott - let us know how you do with it!
We race Lemons Endurance events and our E30 325is give us an easy 2 hours. We have the IE accumulator fitted too which helps starvation of the in tank pump on long rights. The OEM tank 63L is a pain in the ass to fill too…fuel always wants to back up the fill tube because fo the slow fill across the saddle and stupidly small vent from that side!
I’ve not experienced any difficulty with or difference between fueling the 55L or 63L tanks. There is way more room across the top of the saddle than the diameter of the fill pipe, so I can’t see where that would be a problem. However, if the tank ventilation system is compromised that will cause problems (with either tank) when fueling.
A PO of my current car made some “creative” mods to the tank’s vent system and expansion tank (the tank had been removed). I did have problems with gas spillage on a full tank in left hand corners and problems fueling until I found the problem and took the system back to stock configuration.