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MG MGB GT V8 Factory Originals Technical - EFI fuel supply, cheapest best approach(Ithink)
I'm going to post this as a separate thread for those still setting up, cause I've spent heaps of time and money messing around with fuel supply and I needn't have.
The definitive answer to EFI fuel supply (for me) is
No swirl pot required, just a very late sender ($50), which has a fuel uptake line in it, which connects to a large cheap filter (Kmart $18) , which connects to a feeder roller vane pump, which connects to a high pressure rollervane pump. This connects to the fuel rail and thence back to the old pick up point on the tank.
The feeder pump is a peirsburge model, cost about $100 Australian. This is a small high volume rollervane pump able to keep up with the larger high pressure Bosh pump ($150) but more able to draw petrol, The Bosh high pressure fuel pump can deliver high pressure but draws petrol very poorly. The feeder pump can pull through a filter up to about half a meter above the tank without becoming noisy (I've tried this). However I would not place it much higher than the top of the tank (ie the boot) as I expect much higher fuel vapor pressure regulations in the future.
I will post part numbers should there be an interest expressed.
These pumps can be heard when the motor is off but very definitely not when the motor is running, unless you press your ear to the side of the car. Not something you are going to do voluntarily at any reasonable road speed ;)
I have located both pumps and filter in a small box behind the rear wheel up under the boot. There is no reason why they could not be in the boot should you desire.
I think this is better than most other approaches because both pumps draw through a fine filter and are protected, Both pumps (and filter) can be easily got at for replacement should the need arise. I carry a spare bosh pump so should the 'in use' one fail I'm not stuck in the middle of no where. Should the feeder fail then I can rely on the main (albeit noisy) pump to get me to a replacement/home. All bases covered.
Even with less than 7 litres of fuel in the tank, I have never noticed the need for a antisurge baffle, or swirl pot. Something to do with the adjacent location of the pick up and return line and the shape of the tank. A number of others have commented that they also have not noticed the absence of the swirl pot. If anyone would like to confirm or deny this with personal experience this would be of value. However should the need for a swirl pot be perceived, no money has been wasted as you still need a feederpump and return line to set this up.
The overriding factor in setting all this up is that petrol has a high vapor pressure (not the least because of the butane in the blend) which will increase as it is warmed up (around 100Kpa @ 38 degC). You cannot have a closed loop in the supply or pressure will build in that loop and cut off supply one way or another, or simply become very noisy because the pump is pumping gas, not liquid.
You need a pressure release. I.e. a line back to the tank.
|Good call Peter. I used the early style tank with the late style sender and all went well. The idea of using the big fuel filter and dual pumps assures you won't tank your expensive pump by letting it run dry. When I ran my original setup (early tank/late sender) I ran that baby down to almost empty w/o surging problems. |
The only problem I had was the float on the late sender interfered with the built in fuel pickup line. The built in line prevented the float from moving all the way up with a full tank of gas. This was solved by popping out the float and moving it over so it mounted towards the front of the car as opposed to mounting with the majority of the float towards the rear of the car. (If you look at the sender you'll know what I mean) That pretty much solved my problems.
Swirl pots are good but not necessary if you design your fuel system correctly.
|My system is similar, but can use pretty much any puller/carb style pump, then then the bosch inline. Complete cost for the filter assembly was around $40-50, then whatever cost for our coice of carb pump. It may very well be easier to find these type of things up here in the US, but I know NOTHING about the Australian/New Zealand Car industry, so sorry if I make improper assumptions.|
I am actually using the cheap replacement pump that my car came with when I bought it with the 4cyl motor, so the stock SU may very well work, that or one of the easily available Purolatore little box pumps for $25 at Schucks, Napa, Autozone. Plus when the time comes filter replacements are no harder than a oil filter, screw off the filter, screw on a new one, though given the size of thse filters it may be a decade before they are full of enough debris to need replacement.
SO far it has been able to feed my 5.0L EFI mustang motor on WOT bursts with no problem, I even ran her down to about 1-2 gallons in the tank and did not see stuttering as the filter probably holds1/2 a gallon.
|Justin, had forgotten about the float interference, good of you to mention it, I did exactly the same as you.|
That's not a bad set up Larry, and might very well be just the thing for those who haven't yet bought a rollervane fuel feeder pump and are thinking of taking a chance with the old carby pump.
However that remote fuel accumulator isn't available here as far as I know. I did look around for just that at one stage recently but when I could not find this I settled on the less elaborate set up as outlined above. This is very easy and quick to set up by the way just some lengths of fuelline required and a few hose clamps (plus pumps , sender and filter). Took about an hour tops, just cut and push together.
Ironic really cause I've tried just about every permutation and combination you can imagine. Carby pump into high-pressure pump closed loop (runs until vapor pressure builds up) . High pressure rollervane Pump next to batterybox behind driver(noisy) Pump without filter next to battery box (less noisy for a day or two and then clogged with debris!). Pump next to battery box with high flow filter (still noisy/vapor bubbles) Elaborate T sections to promote venturi suction (noisy). Feeder pump into elaborate T section set up (noisy because of elaborate T section return line). I even had a swirl pot put into the tank at one stage, which made no difference as I found out when I destroyed the expensive swirl pot tank (long story) and had to replace it with a standard one at short notice. As Porsche used to like to say "simple is best".
|I had a feeling that was the case. My system is much the same concept, just taken a little farther. The big difference is in the vent line out of the filter that "T's" into the return line. My biggest concern with a fuel system is/was a way to get AIR out of the system once the carby style pump pulled it from the tank (for whatever reason) and pushed it into the lines. The T handles that issue |
I cannot say a STOCK MG pump will definitely cover it for me, I have some cheap aftermarket replacement pump that came with my car, but it is not some fancy Holley 1000gph pump, it is just a litte thing that only put out about 6psi tops, but flows decent gallons as required for a stock mg.
|It's not so much air as butane, or just the light ends. Depending on the local regulations petrol will start to distill over at 27 degree sometimes.Also the petrol blend can commonly have 10% or more butane in it. Put your petrol under suction or heat and you get cavitation in the high pressure pump I guess.|
For those still setting up;
The feeder pump is made by Pierburg in germany and is called an Auto-suction vane cell pump. stock no. 12001. it can deliver 0.5 bar when used as a primary pump. It cost $95 Australian (apply exchange rate to get an idea what it might cost localy) and for the people in Melbourne can be got from Petro-ject 03 98737006.
The main high pressure pump is a Bosh one pt no 0580464070 and cost $140.
|I'm sorry, but all above seems complicated to me, not simple. I had Glenn Towery put a swirl pot in a stock MG fuel tank & add a 3/8" feed. I realize I could have used an earlier tank with a feed & used a late sender to provide a return inlet to make things even simpler.|
I am using a Bosh pump from a Volvo 240 Turbo. This pump is out of tank & will suck as well as push, so I am using only 1 pump- simpler than 2. I chose to use the complete Volvo setup including the large filter- simple- but a very large filter coulds have been used in place of the swirl pot. I did install a primary filter between the fuel tank & fuel pump.
So the simplest sysem would be an early 70's fuel tank, Volvo pump, late model MG sender including the fuel outlet changed to return inlet to tank, and a large filter between pump & FI system as a swirl pot.
The only concern would be if supplying a large displacement engine such as Larry's, would the original fuel line (and supply outlet from the tank)allow for enough fuel flow at wide open throttle. This would certainly be adequate for a 4.0 or 4.2 Rover engine.
|YEs I am using a Early model tank with LAte sender also. The pick-up line in the tank seems to be fairly large so that is my pick-up. I then ran nice new 3/8 tube all the way to the front. I will have to look into that Volvo pump, sounds like a nice simpel solution.|
|I'm using a Volvo pump also. Plus I have a pump from a 3ltr Nissan, mounted along side the Volvo pump. They're plumbed in parallel via "Y" connectors. Apparently,it's important to keep any pre-used pumps "wet" with fuel.In the event of a failure ,I just have to swap the electrical connection over.I did think of using a switch to do this, but that is something else to go wrong.I would have used another Volvo pump, but the Nissan one was available at the time. It's just another option.|
|Peter. I did discuss the second pump with Roger Parker some year's back and he was adamant that so long the pump contained fuel, a second pump to the Bosch unit was unnecessary. The provisos he made were firstly that a swirl pot should be included internally or externally and second, that the pump should be as low as the bottom of the tank.|
I have a stainless tank so my pot is external - it consists of the larger of the two filters fitted on the RV8/SDI - and seems to work (about 40K miles).
If the side of the battery box is a bit crowded - its worth bearing in mind that Landrover changed the big filter on all its 3.9s and later - to a smaller unit which will fit in the engine compartment.
On the question of fuel evaporation - the science is incontrovertible but the problem must also exist on the carb systems - in the OE SU system it was partly dealt with by condensation in the final filter (which always contains a fuel gas bubble) but the secret was the SU fuel pump which will simply not pump air - the same goes for the RV8s bosch unit.
From this longwinded explanation you can see why I took out the OE pump BUT I should also explain why I am planning to put it back ! This system will maintain suction down to the last 2 or 3 litres or until the swirl pot is empty - after that the suction would be lost - an SU pump on the other hand will go on adding in drips and drops to the swirl pot as and when it can get suction.
For those with a long memory - a regular problem with the early fuel injection systems was airlocks caused by loss of suction - I reckon, the primary LP pump should reduce the incidence - but always bearing in mind that in 40 years, MGBs have let me down three times - always that bl*sted pump.
If that helps
Didn't know about the Volvo pump. Good old Volvos, first the brakes and now the pumps. Next time I get stuck behind one going incredibly slowly in the very fast lane I will think fewer unkind thoughts. Useful information for sure. Should my feeder pump ever fail, Volvo it is. Depending on cost of course but as Barry says something to look into. Have you (or Barry) Got a part/model no?, it would be nice to ovoid the Volvo dealer (and his substantial mark up) and go direct to a distributor like Petro-ject. I found there was something like a 47% mark up with the bosh part.
I quite agree with the theory about air locks caused by surge but there seems to be something about MGB tanks that defies the theory. Just a happy chance I guess.
I did originally, and expensively, set up an internal swirl pot, prior to accidentaly destroying it (half inch pipes the works)), much as Roger Williams set up however found the pump to be quite audible when cruising along at low speed. The proposed increase in allowed fuel vapor pressure regulation will not help this I am thinking.
By OE pump do you mean the dreaded SU?.You are a brave man if so. Personally I have had some very bad times because of the SU pump and its sometimes bizarre and dangerous choices of stopping locations.
|I still don't understand why a second pump is needed, my Bosch pump (Ex Rover SD1 Vitesse) is mounted hard against the front of the tank at outlet level, with the filter in the engine bay (A la Vitesse again), and I've never had any fuel feed problems since I did this set-up.|
There is a certain amount of pump noise audible before the engine fires up......but I have a resistor in the circuit (again a Vitesse mod) which make the pump inaudible., The Bosch pump in my Golf Gti is noisier, I can just about hear it at tickover. Is pump noise a serious issue ? All the Bosch pumped cars I've had have been reliable in that respect.......and as far as I'm aware the Vitesses did not have any pump problems, I did burn out one pump on a Mk1 Gti when it suffered the notorious fuel filler pipe collapse , and rust and road crud entered the tank, but that's to be expected.
|Peter - Jim was good enough to look up the number on his which I believe translates to Bosch 0580 254 909 or 0580 254 949. I am not sure how it differs from the RV8 pump.|
Michael - re the vitess filter in the engine bay - if this is the big filter - the mod kit for the smaller filter is still around.
|Well the Inline bosch pumps we get over here that can support a decent sized V8 have just about NO ability to pull fuel from the tank. I had mine mouunted in the stock pump location and after about 5 minutes of driving she would just fall apart. IT could have been any number of things from air bubbles in the fuel, the pick-up being uncovered for a brief second, or somewhat of a vaccum forming in the tank. These pumps are just that weak at pulling.|
WE are not alone in this issue, I got most of my info and ideas from classic bronco (1966-76) folks that have gone EFI on thier 4x4 rigs. They ran into the same issues, although more drasitically due to the 4x4 action.
The set-up is not very complex or expensive, but is very reliable and also makes filter changes a no harder than a basic oil filter. unscrew, replace, done. I do think that a stock SU pump could probably be enough for bigger motor, but I do not have one to check that with. I might see if one of the locals has a working SU laying around I can test with. I also added in a relay to the system, so that both fuel pumps run off of it, and will probably hook that into the Fuel pump circuit of my EFI system as well.
|For my fuel injected 302, I've bought a new tank and I'm modifying it to accept the in-tank pump from the same car (mustang) that the engine came from. Using a chisel, I cut the mounting flange from the mustang tank and also took the swirl pot out of the mustang tank. It's a simple matter of cutting a section out of the top of the new tank, spot-welding the swirl pot to the bottom of the tank, welding the mustang flange in to the correct spot, and finally welding up the top of the mg tank. The two most difficult parts are shortening the fuel pump bracket to the correct depth for the mg tank and welding a pocket into the boot/trunk floor of the car to make room for the lines coming out of the top of the tank. If you have decent welding skills you can do this, and there is no danger as long as you use a NEW tank. I always worry about one electric fuel pump crapping out on me, let alone two.|
|Roger, thanks for the info', I'll give Petroject a call next week and check their price, and if they carry the item.|
Michael, I believe you are using a different back axle and handbrake arrangement (Rover?). If it wasn't for that pesky handbrake cable there would be oodles of room for filters and pumps at "bottom of the tank level". I've thought of rebolting/rotating the backing plates on the wheels and rotating the cable up and forward, but the "road worthy" people are quite unreasonable about that. Given the number of rear disk conversions and axle swaps about the place I can't see their difficulty, but significantly, they can!
I suspect Larry might be right about the different pumps. Either that or we are back to the local regulations about fuel vapor pressure being different. Here FVI is around 115 KPa and RVP works out about 100 approx.' (this time of the year)
Ryan- Keep in mind that you are still relying on an electric pump, one that is very hard to get to by the side of the road i.e. tow home situation. If it is "in tank" it is also less protected from debris than one outside the tank with a big filter. Most in tank pumps rely on a simple nylon filter. I had an external high flow nylon filter on one of my many pump arrangements and it was remarkable how much debris accumulated in it, from a supposedly new and clean tank. In fact I did once try to run without a filter and didn't last too long. Having said that though ,there are vaste numbers of intank EFI set ups about the place.
If the Volvo item is as good as it appears this might save you alot of trouble, however I suppose like most of us V8 coversion types, you're going to do it your way!
I'm always getting you two Rogers mixed up, my appologies. It's a strange chance that produced two MGB V8 conversion experts at the same time and virtualy the same place.
|We don't have any vapor reg like that that I know of. So yes could just be regulations. Take a look at a Holley Comander 950 EFI kit, that looks like the same pump I use (They are all bosch inlines).|
This is a great discussion guys, lots of info and ideas, I LIKE IT!! There was little to no discussion about it a year ago when I went thru my issues.
|Peter,the Nissan pump I'm using right now came out of a VL Commodore. Another option for you. Barrie E|
Thanks for the suggestion but I thought Commodores used a combination feeder pump and sender arrangement (that goes into the tank obviously) as well as the larger pump. I know little about Holdens so perhaps this was for the older models. I noticed it in a Holden manual recently (was next to the filters in Kmart)It was one of the deciding factors in adopting a feeder arrangement. i.e. if GM thought it necessary, then they had a good reason.
In fact the much smaller feeder pump could go through the MG sender aperture if necessary. Fiddley though.
I would be interested to hear how Michael adapted the Rover handbrake arrangement to the MG because it's clear whatever he's got keeps well clear of the tank. And any trouble he had with the Red Tape brigade.
|Peter- Is your rig bug free so far? Sure sounds cheaper, simpler and effective to me. What nuances our we missing? What about frothing or low fuel?|
|Peter, VL Commodores used Nissan 3ltr engines. because in '86 Aus. went ULP & GMs 6 cyl engines couldn't cope ,so they used Nissan engines until about '88 when the Buick engine was/is used. The Nissan pumps are very similar to the ones used in Volvos. I think they're Bosch made under license. Further to Roger's info on part #s. The difference in the pumps is the electrical connections. 909 uses push-on type & 949 has screw on type. I thought the Nissan option might be a bit cheaper, knowing how a part is priced by the type of car it's used on. Barrie E|
Interested to know where have you got your pump located? Battery box or boot. Bottom of tank etc.
Vem, not a whisper of any problems so far and I use the car on a daily basis. Have clocked up about 15000 miles in the last year and a half. I've been using almost this arrangment for about a year and exactly this for a month or so. By almost, I mean unnecessaraly complicated variations of the high pressure pump being fed by the high volume pump which were variously unsatisfactory for reasons outline above.
The other day I was braking heavly on a hill (downhill) and for just about half a second I though I heard the feeder pump strain. However there was no hint of the engine stalling and it might have been my imagination. I refilled a short time later and put in 34 litres so the tank must have been near empty. I don't use my car for racing so those anticipating throwing their cars around a track with a nearly empty tank could conceivably have a problem. However if they do then they have not wasted any money since they can then add an external swirl pot to the set up very easily. You still need a feeder pump and a return line to the tank with one of these and an external swirl pot is probably a bit better than an internal one for these high G activities.
Yes I'm using a cut down Rover SD1 Vitesse axle, but it seems very similar the MGB one I took out.
I will try to take a couple of digital photos for you. I don't know if I still have your E mail address.
I'm using an MGB handbrake rod & cable, running across the rear of the axle, like the B, it's above the pump, as the pump is on a long 'L' shaped bracket welded to the boot floor, so that the pump sits pressed up against the right hand front corner of the tank, at tank bottom level with a very short pipe run. Gravity feed has been more than adequate.
I originally fitted it on the front of the battery box, with a pipe over the wheel arch, but it just did not have enough suck when the weather was warm, it let me down a couple of times in France so it had to move.
|That would be good Michael|
I spoke to David at Petroject and got some figures.
The 0580 464070 Bosch that I'm using pumps 130 litres an hour and delivers it at 3 barr.
The 0580 254909 & screw out let varient 0580 254949 pumps 148 litres/hr and delivers it at 5 barr.
The Feeder pump 12001 delivers 0.5 barr, however there was no data on pumping rate, which is frustrating.
In others words the 254909 is a more powerful pump and conceivably draws better that the 070 (they sell them here at $180 by the way). If those using it could tell us where they've located it this would help. Are there any being used sucessfully at 'top of the tank' level drawing through a filter. What are the appetures on that filter if so ie is the volvo application that Jim mentions a large appeture fine filter, this would be just the ticket if so.
David said that even volvo (one some of their models) used an in tank, through the sender, feederpump, much as GM does. Then went on to say that "Id probably be allright with just a 909". A bit speculative I thought.
The question that has been raised is can the feeder keep up with the higher volume pump?. That is if the 909 be unable to draw through a fine filter in the summer, at "top of the tank" level.In other words, in the boot. We need imput from Jim or Barry on this one.
The informtion sheet the feeder came with showed one inline application just as I've set up and implied universal use, so it's probably a safe bet. Since fuel vapour pressure regulations are on the rise I am probably going to stick with the feeder for now. However if I were just setting up I probably would give it a try without a feeder first, then if necessary go and buy one., nothing to lose by giving it a go!
Referring to your last posting. There is no doubt the Bosch pumps will work without a feeder so long as they are primed.
However I have been looking at the MG manual for the 3.9 where the techspecs say the 0580 464 070 pump delivers 4.1 Bar to the rail but with the lucas regulator only 2.5 Bar is required at the injectors.
The point is this; if the the recommended pump is working at reduced efficiency because it is also sucking as well as blowing - the pump may not be powerful enough for the job UNLESS there is a pumped feed.
The 909 and 949 pumps would appear to have a better margin - perhaps an essential change to accompany a variable fuel pressure regulator - and for bigger engines.
3 Pics sent, hope they make sense.
Your post reminded me, I changed the Bosch pump for an uprated one (Rimmer part no AUU1649ALT) and also changed the resistor for an uprated one (Rimmer part no DRC3017HP).
I had a rising rate regulator on the original flap-valve system, when I upgraded to hot-wire, I replaced it with a fixed regulator, but have since put the rising rate one back on, probably not necessary with hot-wire as I have Lambda sensors anyway.
|Peter, my setup is as follows.I have a surge tank made by "Redline" mounted in the boot. It's about 6" wide,4" deep & 10" high.It's mounted on the ledge that runs across the front of the boot alongside the bulkhead. This is fed by a small Repco LP pump mounted on the bulkhead alongside the surge tank.The inj pump(s) are mounted where the RH battery box was & fed by gravity via a 1/2" filter,from the surge tank.There's another filter in the engine bay,mounted on the front of the heater box.The return line from the fuel rail is fed to the surge tank which is vented to the fuel tank.The fuel lines are all 5/16" & 1/2" copper pipe.The surge tank & LP pump are boxed in for safety & appearance.The LP pump is a tad noisy at idle despite being well insulated.HTHs Barrie E|
|I must say all your contributions are very usefull. I'll certainly be filing this thread for future reference. Many thanks|
|Thanks for the top tips everyone. Having weighed up the options, I too am going to use a fuel filter in lieu of a swirl pot. It's less work and also puts a filter ahead of the high pressure pump which must be a good idea. The screw-on canister filter (as used by Larry) seems a good idea and offers the advantange of a built-in mounting bracket. For those not in the USA, sourcing a screw-on canister type petrol filter may be a problem. This week I found a suitable assembly (carrier/bracket and filter) at a local chandlers @ £29.99. The brand is Quicksiver, made by Mercury for marine use (in fact it's a water separating filter). It's not as big as the Bronco filter used by Larry, but I believe it will do the job (will require a small internal extension pipe to the output port as discribed in Larry's solution).|
|The screw in filter mounting is nothing more than a standard remote oil filter mount, available from lots of sources in the UK.|
|Yes Tony has it right, it is your normal old remote oil filter base as made here in the US by TD Performance.|
This thread was discussed between 19/09/2004 and 02/10/2004
This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.