Scottie-GNZ Posted June 19, 2007 Share Posted June 19, 2007 I run a single Walbro in-tank and need to step up to something that flows more. Simple option is dual in-tank Walbros but plumbing them on the FC hangar is a royal PITA. Another option, though not as good as the dual Walbro, is to replace the Walbro with a single Bosch 044 which should give me another ~25+% flow. I read that if the Bosch is used as an inline and fed by the in-tank Walbro, it will help increase the flow of the Bosch. Can someone please explain how that is possible. Logic says that if the Walbro is feeding the Bosch and the Walbro flows less, that limits the flow of the Bosch. Guess I am wrong but want to understand why. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted June 19, 2007 Share Posted June 19, 2007 What you heard is incorrect regarding series pump applications. In series the head rating is added for the two pumps, but the flow remains the same as the smallest pump. So, it will pump the same flow but at a higher pressure, which is some advantage but not that much since in HP applications regarding fuel, mass flow rate = HP, so we need more flow to get more HP. In paralell, the flows of the two pumps are added at a specific head value. So, it flows twice the flow at the same pressure, voila', that is = more HP! Quote Link to comment Share on other sites More sharing options...
Careless Posted June 19, 2007 Share Posted June 19, 2007 I run a single Walbro in-tank and need to step up to something that flows more. Simple option is dual in-tank Walbros but plumbing them on the FC hangar is a royal PITA. Another option, though not as good as the dual Walbro, is to replace the Walbro with a single Bosch 044 which should give me another ~25+% flow. I read that if the Bosch is used as an inline and fed by the in-tank Walbro, it will help increase the flow of the Bosch. Can someone please explain how that is possible. Logic says that if the Walbro is feeding the Bosch and the Walbro flows less, that limits the flow of the Bosch. Guess I am wrong but want to understand why. if the Walbro feeds the Bosch pump the fuel at a positive pressure rather than the Bosch creating negative pressure to suck fuel, it would get fuel faster and have less strain, allowing it to pump more. atleast thats what I've always thought. if you cook a meal for a kid, they'll eat a lot more than if they had to cook it for themselves. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted June 19, 2007 Author Share Posted June 19, 2007 http://www.rx7store.net/product_p/bosch044.htm See the last sentence of the description. Quote Link to comment Share on other sites More sharing options...
Guest TeamNissan Posted June 19, 2007 Share Posted June 19, 2007 They are trying to lie to you Scottie lol. Seriously though fuel pumps, well mainly all pumps just like liquid or gas pipes etc... are always limited by the smallest diameter or lowest flow, only pressure is gained. Quote Link to comment Share on other sites More sharing options...
TimZ Posted June 20, 2007 Share Posted June 20, 2007 What you heard is incorrect regarding series pump applications. In series the head rating is added for the two pumps, but the flow remains the same as the smallest pump. So, it will pump the same flow but at a higher pressure, which is some advantage but not that much since in HP applications regarding fuel, mass flow rate = HP, so we need more flow to get more HP. In paralell, the flows of the two pumps are added at a specific head value. So, it flows twice the flow at the same pressure, voila', that is = more HP! I agree with this, with a couple of caveats... In the series application, the first pump will be able to flow more than "normal", since it will be pumping into the inlet of the second pump, probably with a negative relative pressure. How much this helps the flow depends on the pump, but it can make a pretty big difference. Check the manufacturer's data (I know flow charts are available for the Walbro) and compare flow at 45psi vs. flow at 0 psi. Also, the second pump's flow chart will (I think - 95% sure ) be shifted upwards by however much the first pump has increased its inlet pressure. On the parallel application this is true, provided neither pump has an internal pressure bypass that comes into play (like the stock NA Datsun EFI pumps, for instance) Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted June 21, 2007 Author Share Posted June 21, 2007 Thanks for the feedback guys. Working on dual Walbros. PITA but I love a new challenge. BTW, if anyone could use a Kenne-Bell Boost-A-Pump, lemme know before I throw it up on e-Bay. It will increase the voltage to the pump by 50% up to to a max of 17.5V. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.