Waldi Posted October 3, 2017 Report Share Posted October 3, 2017 (edited) Hello, I would appreciate your hints / solutions on the following: I want to increase my fuel tank outlet diameter to reduce pressure losses to the Bosch pump. Current outlet inner diameter is 6.5 mm. I contacted Revington, and they informed me they do not sell a bigger nipple/fitting because in rheir experience it is not needed for the Bosch pump. I realize their experience is much (much) more than mine, but being a subborn engineer, I feel that fitting a bigger process diameter feed line to the pump is better, especially because I intend to install a good (and big) fuel filter in this line, not just a "pre-filter", and this will be a restriction. An increase in available inlet pressure will also increase the allowable fuel temperature before cavitation occurs. Has anyone bought or made such a fitting? A sketch would be great. I think an increase to 8.5 or even 9 mm should be possible. Off course, the seat for the olive in the original tank fitting has to be drilled out, otherwise the benefit is nil. Regards, Waldi Additional info: My Bosch 996 pump has an inlet ferrule of 12 mm OD and almost 9 mm ID. Edited October 3, 2017 by Waldi Quote Link to post Share on other sites
John L Posted October 3, 2017 Report Share Posted October 3, 2017 Malcolm Jones does them, give him a call http://prestigeinjection.net/ John Quote Link to post Share on other sites
brian -r Posted October 3, 2017 Report Share Posted October 3, 2017 Hi Waldi I bought one from Malcolm Jones at Prestige injection last year,machined from solid brass and well made. I think it cost around £20 . Brian Quote Link to post Share on other sites
Steves_TR6 Posted October 3, 2017 Report Share Posted October 3, 2017 Hi Waldi I bought one from Malcolm Jones at Prestige injection last year,machined from solid brass and well made. I think it cost around £20 . Brian Interesting. I’m about to renew filter and some old pipes on my 1990’s bosch setup. Does Malcolm’s new fitting just screw in, or is there more to it? Steve Quote Link to post Share on other sites
snowric Posted October 3, 2017 Report Share Posted October 3, 2017 Mine just screwed in. Snowy Quote Link to post Share on other sites
Waldi Posted October 4, 2017 Author Report Share Posted October 4, 2017 (edited) Thank you all.I did send Prestige an e-mail, twice, they did not respond, apparently busy or not interested.I have ordered a ferrule 1/2" bsp to 12 mm on the www, see what that looks like. It will arrive in one or 2 weeks, will report back here.Regards,Waldi Edit: 1/2"BSP is not the correct thread size! Edited October 5, 2017 by Waldi Quote Link to post Share on other sites
Richard71 Posted October 4, 2017 Report Share Posted October 4, 2017 Malcolm at prestige never seems to respond to emails, well, not in my experience anyway, try calling on the number given on his website instead. Richard. Quote Link to post Share on other sites
brian -r Posted October 4, 2017 Report Share Posted October 4, 2017 Mine just screwed in also. Have found it more succesful to phone Malcolm than e-mail cheers Brian Quote Link to post Share on other sites
Waldi Posted October 4, 2017 Author Report Share Posted October 4, 2017 I called him too, he indicated he was busy and would reply but he never responded. It's ok, I make mistakes too (others say????). I know Prestige are highly respected. Postage for a single small item from UK to Holland makes it unattractive. I will see what the internet buy looks like; The ferrule I ordered was 6.50 USD incl. Shipping. Regards, Waldi Quote Link to post Share on other sites
Steves_TR6 Posted October 4, 2017 Report Share Posted October 4, 2017 I’ll be interested to learn how that works out Waldi. Is the tank rhread 1/2 bsp? Sounds too big to me? Steve Quote Link to post Share on other sites
Guest ntc Posted October 4, 2017 Report Share Posted October 4, 2017 (edited) It was never needed imho,save your money. Edited October 4, 2017 by ntc Quote Link to post Share on other sites
Nick Jones Posted October 4, 2017 Report Share Posted October 4, 2017 It was never needed imho,save your money. Obviously not as no PI car has ever suffered pump cavitation.......... oh, wait a moment...... IMO 1/4" is small even for a carb equipped car of 120ish bhp, where the pump is supplying more or less to demand. On PI cars the pump always pumps a surplus, so the flows through the lines are higher. And the excess work done warms the fuel. This doesn't matter on the pump discharge side (where they run 5/16" pipe from the factory oddly enough) as there is plenty of pressure to push it through and stop the fuel from vapourising. Not so on the suction side where you've only one atmosphere of pressure plus a little static head. Bosch pumps run more flow again than the Lucas pump and Bosch themselves usually use at least 10mm inlet sizes to the pump - says it all really. The undersized tank outlet is just one of the factors that has caused "pump" problems with PI cars for decades and is worth correcting IMO. Nick Quote Link to post Share on other sites
Waldi Posted October 5, 2017 Author Report Share Posted October 5, 2017 Ill be interested to learn how that works out Waldi. Is the tank rhread 1/2 bsp? Sounds too big to me? Steve Steve, Thanks, think I had a senior moment with the size: I tried a 1/2" UNF bolt in the tank outlet, it fitted. But since UNF does not have the correct thread angle, I then ordered BSP, also.......1/2". Bit confusing for a metric guy like me, so it looks like I made a mistake and ordered the wrong ferrule????. I will double check and see if other ferrules are available. Will keep you posted off course. Regards, Waldi Quote Link to post Share on other sites
Waldi Posted October 5, 2017 Author Report Share Posted October 5, 2017 Nick, I agree. The small tank outlet is certainly contributing to the cavitation issue, that is plain physics. Even with a standard Lucas pump. My daily drivers never needed a bag of frozen peas. You can argue that factors like poor maintenance etc. are causing the overheating, and those may contribute too, but a fact is the system is not very tolerant to changing conditions. Regards, Waldi Quote Link to post Share on other sites
Waldi Posted October 5, 2017 Author Report Share Posted October 5, 2017 Update: I looked into the correct thread size for the tank outlet. It is certainly not 1/2"BSP and also not 1/4"BSP (which has 19 TPI), although this comes close. Neil Revington's site indicates it is 1/2"UNF x 20. My Original brass nut's outer thread measures 12.7 mm OD and screws nice in a new 1/2"UNF standard nut, so this practiclly confirms it. I cannot find much 1/2"-20 UNF hose nippels on the web, so will have one machined here locally. I wil keep you posted. Regards, Waldi Quote Link to post Share on other sites
Steves_TR6 Posted October 5, 2017 Report Share Posted October 5, 2017 Thanks for the update Waldi My car runs perfectly with the standard tank outlet, its tuned to ‘more than 170hp’ so Neil is right that a larget outlet isnt necessary ...... but hell that needn’t stop us! I have led illumination, remote central locking, nice stereo with sub woofer, dont ‘need’ any of those either :-) I do think the Bosch 996 pump will benefit from a less obstructed feed, i’m presently running with a Sytec disposable pre-filter which has 8mm inlet and outlet, but the Bosch has a 12mm inlet so this has to be constraining flow at full chat. My rubber hoses are looking a little tired so going to replace those and the filter, ideally with 10 or 12 mm all the way to the Bosch pump. Hence i’ll be interested in the 1/2 unf outlet for the tank of we can find/make one. Steve Quote Link to post Share on other sites
barkerwilliams Posted October 5, 2017 Report Share Posted October 5, 2017 Waldi, To improve fuel flow and ease any restriction on the pump ensure all pipework from the tank to the pump has smooth bends with as large as possible bend radius and ensure the pipe used does not collapse on the bends. I found on my cars that stainless braided pipes seemed to have a soft inner core for the actual pipe and this would collapse easily on bends and restrict the flow. The thick walled Gates Barricade hoses resist collapsing. After the pump the fuel is at higher pressure and it is not so much of an issue. Alan Quote Link to post Share on other sites
Waldi Posted October 5, 2017 Author Report Share Posted October 5, 2017 Thanks Alan, That is my plan. Interesting that the tank outlet is UNF threaded as opposed to BSP, but maybe this is normal for a British car. does anyone know where this originates from? Regards, Waldi Quote Link to post Share on other sites
Steves_TR6 Posted October 5, 2017 Report Share Posted October 5, 2017 Is this what we are looking for : https://www.ebay.co.uk/i/281825041010 Quote Link to post Share on other sites
Waldi Posted October 5, 2017 Author Report Share Posted October 5, 2017 Hi Steve, Very good, it is for a 10 mm hose, so ID will probably around 8 mm. I have not found a hose tail yet for a 12 mm hose wirh 1/2" UNF male thread, that would be the ultimate (same as Bosch pump inlet). Regards, Waldi Quote Link to post Share on other sites
Steves_TR6 Posted October 6, 2017 Report Share Posted October 6, 2017 I could not find a 12mm either Waldi. What’s the id of the standard outlet i wonder? Flow would be proportional to the square of the diameter i think, so any increase is beneficial. Steve Quote Link to post Share on other sites
Waldi Posted October 6, 2017 Author Report Share Posted October 6, 2017 (edited) Hi Steve, The original tank outlet pipe measured 6.5 mm ID. A 10 mm ferrule may give 7 or maybe max. 8 mm ID. I guess the minimum wall thickness should be 1 mm or slightly more. I have asked Bosch-NL for a filter recommendation, in this case bigger is probably better. Could not find pressure drop curves on the www for their filters, so have asked if these are available. Expect an answer next week. Regards, Waldi Edited October 6, 2017 by Waldi Quote Link to post Share on other sites
TriumphV8 Posted October 6, 2017 Report Share Posted October 6, 2017 (edited) I found it very easy to increase. My USA CC from 1969 has a plugged outlet at the other side of the tank. Hole was already drilled in the trunk same way as for the fuel line. Its for removing the fuel from the car, maybe for shipping. I simply removed that 5/8 UNF plug, cutted in a M16x1,5 thread and used a double banyo bolt with 12mm outlet for the hose. Double banyo is needed because a spacer must be made for the first banyo otherwise the banyo would interfear with the trunk hole. Fuel resistance must be expected from any filter, so the bigger tank outlet might not be sufficient...... https://www.tecparts.com/hydraulik-und-kraftstoff/hydraulik/hydraulikschlauch-armaturen/hohlschrauben-metrischzoellig/hohlschraube-hsm-metrisch-hochdruck-p351853/hohlschraube-hsm-m-16-x-15-hochdruck-63731/?gclid=EAIaIQobChMIkYLktP7b1gIVS40bCh2efwLUEAQYAiABEgIrYfD_BwE Edited October 6, 2017 by TriumphV8 Quote Link to post Share on other sites
Waldi Posted October 6, 2017 Author Report Share Posted October 6, 2017 Hallo Andreas, Thanks for the hint. I considered that too, but the other (bigger) outlet has no swirl pot inside the thank, something Revington pointed me too. It is certainly bigger and up to the task. I looked at the Bosch filters 0450.905.xxx. Rimmers sell the 0450.905.005, also intended as a suction filter, but it is a bit small and a bigger one is 0450.905.066, which is 2.5 times bigger in volume and has M14x1.5 and M14x1.25 threaded connections. I have not found the filtration grade of both, once I know I can order. Regards, Waldi Quote Link to post Share on other sites
TriumphV8 Posted October 7, 2017 Report Share Posted October 7, 2017 I have that in use for four years now, no trouble. Honestly I feed a catchtank in the trunk to avoid all those problems. You will notice trouble by the pump making noise when air gets in. That might happen before tank is low under hard cornering. If you recognize noise there is still time to think about more improvement. Quote Link to post Share on other sites
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