adam73bgt
Club Retro Rides Member
Posts: 4,869
Club RR Member Number: 58
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Feb 11, 2013 16:51:25 GMT
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Hi all, As part of my ongoing research into fitting a more modern engine to my MGB ive recently been thinking about the plumbing in of electrics and fuel and suchlike. The engine id ideally like to use is the Rover T series (naturally aspirated) engine, now I could just keep the fuel injection system from this and all would be well. But that would require me to change most of the fuel system components which I'm not overly fond of doing. So what i want to know really is what are modern engines like on carbs, i mean they're still engines at the end of the day so theres no reason why it shouldnt work, but what differences am i likely to see with MPG and power compared to an injection fed engine, if any at all? I know bike carbs are fairly well trodden path to carb'ing an engine these days but i was thinking i might be able to keep the twin SU carb setup from my existing engine? i believe the principle of operation is the same and it might make people double take when they see SU carbs next to a big 16v head ;D plus i would be able to keep my exsisting fuel pump/lines etc. even if i had to change the carb for something a bit bigger Oh and obviously there would be the small issue of having to make an intake manifold.... Hmm that turned into a bit of an essay... but yeah if anyone has any experience with this or knows of somewhere specific that i should ask then many thanks!
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Feb 11, 2013 17:05:20 GMT
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given that most of the fuel system components are nearly all bolted to the engine, it wont be much work if the engine fits, You'll need to add a fuel return presumably, and an inline high pressure pump, and a fuel pump feed wire and a suitable earth point.
IMO it would be sacrilege to fit carbs! main reason of fitting a more modern is the injection systems and the characteristics these bring.
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Seth
South East
MorrisOxford TriumphMirald HillmanMinx BorgwardIsabellaCombi
Posts: 15,516
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Feb 11, 2013 17:14:24 GMT
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Step right this way... I rebuilt this pair of HS6s before bolting them to the side of the Mazda MX5 engine in our Herald. Tuning them consisted of doing what I could at home following the guide in an excellent book by Des Hammill and then a rolling road session to get the top end under load sorted. They've been on there for three years now and I've not had to touch them at all until recently when a needle valve started playing up. Power on the rolling road was at least what a standard 1.6 MX5 lump would have made if not a bit more. Fuel economy would I imagine be slightly better on injection but I think we are getting much the same as a standard MX5 (The Herald is a bit lighter). I did put quite light springs in the carbs though (before the needles were played with) to aid performance. With heavier springs you would possibly get slightly better economy though with slower throttle response. Making the manifold is obviously the tricky bit. I am fortunate that I had the facilities to make all the bits from ally and then had them welded together. Don't forget that depending on the engine, you will probably also have to do some sort of ignition system. I used Megajolt.
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Follow your dreams or you might as well be a vegetable.
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adam73bgt
Club Retro Rides Member
Posts: 4,869
Club RR Member Number: 58
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Feb 11, 2013 17:39:38 GMT
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I wasn't sure if the tank would have to be modified at all because of the high pressure fuel flow? I'd just go with whatever turned out to be cheaper I think, unless one method has particularly huge advantages over the other Also i think i just prefer the simplicity of carbs especially SU's ;D I rebuilt this pair of HS6s before bolting them to the side of the Mazda MX5 engine in our Herald. Tuning them consisted of doing what I could at home following the guide in an excellent book by Des Hammill and then a rolling road session to get the top end under load sorted. They've been on there for three years now and I've not had to touch them at all until recently when a needle valve started playing up. Power on the rolling road was at least what a standard 1.6 MX5 lump would have made if not a bit more. Fuel economy would I imagine be slightly better on injection but I think we are getting much the same as a standard MX5 (The Herald is a bit lighter). I did put quite light springs in the carbs though (before the needles were played with) to aid performance. With heavier springs you would possibly get slightly better economy though with slower throttle response. Making the manifold is obviously the tricky bit. I am fortunate that I had the facilities to make all the bits from ally and then had them welded together. Don't forget that depending on the engine, you will probably also have to do some sort of ignition system. I used Megajolt. Ah I remember seeing that picture the other day, its partly what made me think that SU's could work on a modern engine While I accept that fuel injection has advantages in cold starting etc. I'd be worried if something went wrong and i ended up with a big repair bill.. Part of the reason I got a B was to have a pretty simple car I could work on myself so if I had a modern engine with all sorts of sensors and things on it, id be missing the point slightly Yeah I'd have to run a megajolt system or similar through a wasted spark ignition system i think as the standard T series distributor would foul the heater box To be honest as long as the overall economy is better than the B series I'd be happy A book I've got seems to claim that SU's can be theoretically better than injection as they're analogue?.. sounded a bit like the LP's vs. CD's debate to me
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adam73bgt
Club Retro Rides Member
Posts: 4,869
Club RR Member Number: 58
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Feb 11, 2013 17:41:32 GMT
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Also is that a vacuum advance on the MX5 but going to a coil pack? how does that work?
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Seth
South East
MorrisOxford TriumphMirald HillmanMinx BorgwardIsabellaCombi
Posts: 15,516
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Feb 11, 2013 18:13:55 GMT
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Also is that a vacuum advance on the MX5 but going to a coil pack? how does that work? That's just me being daft to fool people. The coilpack is mounted on a Lucas Dizzy body to look a bit like a distributor. Vac advance feed from the carb needed plugging anyway so I just decided to run it to the now redundant vac advance unit. As you say, SU carbs are simple but they do their job very effectively. The economy you achieve will partly depend on what size carb(s) you go for and how it is set up, which depends on what you want out of it. You ought to be able to get mid 30s mpg out of a standard B without much difficulty.
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Follow your dreams or you might as well be a vegetable.
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Feb 11, 2013 18:16:26 GMT
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I find fuel injection far simpler than the magikery of carbs!
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adam73bgt
Club Retro Rides Member
Posts: 4,869
Club RR Member Number: 58
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Feb 11, 2013 18:54:45 GMT
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I find fuel injection far simpler than the magikery of carbs! haha! from what ive read, people seem to be quite divided on what they prefer, i don't like electric stuff too much really (i blame my electronics module at uni) though the ability to tune up a car using a laptop and some wires does seem quite attractive when you're fiddling about with screws and springs and needles and getting covered in oil and curse word from carbs ;D That's just me being daft to fool people. The coilpack is mounted on a Lucas Dizzy body to look a bit like a distributor. Vac advance feed from the carb needed plugging anyway so I just decided to run it to the now redundant vac advance unit. As you say, SU carbs are simple but they do their job very effectively. The economy you achieve will partly depend on what size carb(s) you go for and how it is set up, which depends on what you want out of it. You ought to be able to get mid 30s mpg out of a standard B without much difficulty. ha! i thought it didnt quite make sense mm for the 2.0 t16 engine id probably go for hs6's as the hs4's from the B might be a little on the small side yeah i think i once got 34mpg on a motorway run using some mathematics and the questionably accurate fuel gauge... but since i don't do huge miles at the moment, 30+ mpg is fine for me if I'm taking it easy though if i had a 140 odd bhp engine in a B I'm not sure how much id be taking it easy...
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B-8-D
Posted a lot
down to one car!!
Posts: 4,038
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Feb 11, 2013 20:07:28 GMT
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su's would work fine or maybe a pair of bike carbs if you don't want or need 4 thats what I'm doing on my wifes viva soon with a nodiz ignition system.. ive done back to back testing on bike carbs/nodiz to throttle boddys and stand alone management on a few identical engines now on the dyno and can confirm a well set up set of bike carbs can produce almost identical power and torque curves to each other maybe a bit better throttle responce from some carbs. and economy i would say a neglegable difference. si
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Feb 11, 2013 20:34:49 GMT
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Click picture for more
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adam73bgt
Club Retro Rides Member
Posts: 4,869
Club RR Member Number: 58
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Feb 11, 2013 21:15:21 GMT
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Bike carbs are a potential option but i don't know much about them really, i suppose there would be a power gain from having each cylinder individually fed by a carb? mmm webers do sound nice and look quite cool.... Argh! the more i see videos of that P6 and read that website, the more i just want to buy some parts and get tinkering! ;D
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Rich
Club Retro Rides Member
Posts: 6,256
Club RR Member Number: 160
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Feb 11, 2013 22:52:39 GMT
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If you want to run the original engine management, I have the ECU pin-out and wiring diagram for the 20M4/20T4, its quite a simple one!
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adam73bgt
Club Retro Rides Member
Posts: 4,869
Club RR Member Number: 58
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Feb 11, 2013 23:27:39 GMT
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If you want to run the original engine management, I have the ECU pin-out and wiring diagram for the 20M4/20T4, its quite a simple one! That would be interesting to have a gander at if the standard ignition could be made to run without the injection system connected then i could definitely be interested in going down that route ;D
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Rich
Club Retro Rides Member
Posts: 6,256
Club RR Member Number: 160
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If you want to run the original engine management, I have the ECU pin-out and wiring diagram for the 20M4/20T4, its quite a simple one! That would be interesting to have a gander at if the standard ignition could be made to run without the injection system connected then I could definitely be interested in going down that route ;D It's all via one loom and ecu, so in truth an early T is less effort to install complete than get manifolds made for carbs as the injection/ignition system seems simple enough. Will post a copy of the diagram tonight/today.. Currently on my phone. Damn technology
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Rich
Club Retro Rides Member
Posts: 6,256
Club RR Member Number: 160
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I need to piece together a bigger copy but its pretty simple as shown in this slightly more rubbish picture.. weather or not it can run ok minus the injectors is yet to be seen but i'd just put the lot in myself if you are going down that route. Attachments:
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Feb 12, 2013 10:26:26 GMT
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I'm also considering a T series for my MGB, I spent a lot of money on a new 1860cc engine 2 years ago fitted with all the best of gear and was pretty disappointed by it, wish I gone for a t series at the time (would have been cheaper!) one thing that swayed me towards retaining the b series is the character of the engine, always felt a modern fuel injected engine in a MGB kind of defeats the point, its an old car and should therefore feel and perform like an old car...
Subsequently if I ever do get round to fitting a T I plan to run it on carbs, Ive already got HS6's on the B but would probably prefer twin webers, I had a shot in a Cateram a while back with an XE with webers, it of course sounded amazing but more importantly in my opinion the power delivery was stereotypical of a car of that era.
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72 MGB GT 88 Daimler Double Six 89 Rover Mini 91 Nissan Figaro 95 Lotus Esprit S4S 18 Discovery
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sowen
Club Retro Rides Member
Posts: 2,245
Club RR Member Number: 24
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Feb 12, 2013 11:14:08 GMT
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I worked through my upgrades in stages on the Rover P6, starting with the original 8v 2ltr, with twin hs8's, then fitted twin hif44's with Montego turbo needles. I didn't notice any significant difference in this, so the original hs8's must have been pretty well set-up to start with. I then swapped the engines, and retained the hif44's as they were set-up on the 8v engine. The M/T series was again 10:1 CR, so no change there, and it was running the turbo log exhaust manifold so pretty restrictive compared to the standard original 4-2-1 tubular manifold. The main differences were the extra cam and 16valves, and Megajolt ignition. This gave an instant increase in performance over the original engine, all tuned by eye, ear and experience. I would like to have done a rolling road comparison but impatience stopped that ;D Sticking the turbo on has just transformed it further, driveability is fine, starts pretty much turn of the key first time everytime, with no flat spots. I have no idea over fuel consumption, the turbo wasn't fitted for economy My suggestion would be to look at fitting a pair of hif44's to the B-series, and Megajolt or similar, see what happens with that. Then if/when you are ready they will swap over and you know they work straight away.
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adam73bgt
Club Retro Rides Member
Posts: 4,869
Club RR Member Number: 58
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Feb 12, 2013 11:29:11 GMT
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I need to piece together a bigger copy but its pretty simple as shown in this slightly more rubbish picture.. weather or not it can run ok minus the injectors is yet to be seen but i'd just put the lot in myself if you are going down that route. Thanks for that! though I'm not 100% clued up on what I'm looking at there it does appear quite simple to me.. or at least more simple than i was expecting ;D I'm also considering a T series for my MGB, I spent a lot of money on a new 1860cc engine 2 years ago fitted with all the best of gear and was pretty disappointed by it, wish I gone for a t series at the time (would have been cheaper!) one thing that swayed me towards retaining the b series is the character of the engine, always felt a modern fuel injected engine in a MGB kind of defeats the point, its an old car and should therefore feel and perform like an old car... Subsequently if I ever do get round to fitting a T I plan to run it on carbs, Ive already got HS6's on the B but would probably prefer twin webers, I had a shot in a Cateram a while back with an XE with webers, it of course sounded amazing but more importantly in my opinion the power delivery was stereotypical of a car of that era. Yeah ive been a bit torn between tuning the B and fitting an M/T, but i think for the work and expense involved the M/T engines provide a much more reliable way of producing the power. Though when I'm driving about i do like the old world charm of the B series chugging away especially since its learnt a new trick of idling at about 500 rpm sometimes which sounds kind of cool... I worked through my upgrades in stages on the Rover P6, starting with the original 8v 2ltr, with twin hs8's, then fitted twin hif44's with Montego turbo needles. I didn't notice any significant difference in this, so the original hs8's must have been pretty well set-up to start with. I then swapped the engines, and retained the hif44's as they were set-up on the 8v engine. The M/T series was again 10:1 CR, so no change there, and it was running the turbo log exhaust manifold so pretty restrictive compared to the standard original 4-2-1 tubular manifold. The main differences were the extra cam and 16valves, and Megajolt ignition. This gave an instant increase in performance over the original engine, all tuned by eye, ear and experience. I would like to have done a rolling road comparison but impatience stopped that ;D Sticking the turbo on has just transformed it further, driveability is fine, starts pretty much turn of the key first time everytime, with no flat spots. I have no idea over fuel consumption, the turbo wasn't fitted for economy My suggestion would be to look at fitting a pair of hif44's to the B-series, and Megajolt or similar, see what happens with that. Then if/when you are ready they will swap over and you know they work straight away. Hmm thats a different way of looking at it, though from what ive read when i was looking at tuning the B series, the HS6/HIF44 carbs are a little big for a standard engine, especially since mine is the 8:1 low compression model. I suppose i could use the B to test the carbs if i refurbed a pair of HS6/HIF44's however
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Feb 12, 2013 18:57:57 GMT
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If you want to run the original engine management, I have the ECU pin-out and wiring diagram for the 20M4/20T4, its quite a simple one! That would be interesting to have a gander at if the standard ignition could be made to run without the injection system connected then I could definitely be interested in going down that route ;D The trouble with that route is that running an ECU controlled ignition system requires all the same sensors that a full injection system does, the ignition and fuel maps run off the same variables. So all you'd be able to remove would be the feeds to the injectors, which doesn't really simplify things much, then adding the carbs is the MUCH more complicated option than just connecting the injectors that you already have everything to run. I know someone who ran a k-series loom stripped back to 'all it needs for the ignition' with bike carbs. He melted 2 or 3 engines before selling the conversion to a mate who put a new loom and full injection system back on it. He'd removed a little too much (Admittedly you have to get it VERY wrong to manage this, and I think one of the engines was killed by over-revving, not melting.) Personally I'd probably put it in with the full injection system. Purely for the practicality of it on a cold winters day, and because I'd have said converting the B's fuel system to run the injection would be easier than converting the engine to run carbs (return line, swirl pot, pump, done), but I guess it all just depends how period correct you want it to be, I completely understand the appeal of the carbs.
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Last Edit: Feb 12, 2013 19:00:29 GMT by RobinJI
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adam73bgt
Club Retro Rides Member
Posts: 4,869
Club RR Member Number: 58
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Aye those are good points, i suppose that means that if i was serious about having a 'simple' ignition system and carbs id then have to look into a megajolt or similar system, which would most likely cost more than converting the B to injection. I do kind of miss the novelty of being able to just jump in a car, turn the key and drive off without having to worry about chokes and warming up etc. so perhaps i should just face my fears and get involved in some electrickery.. I'm not too bothered about it being too period correct, I'm not quite trying to recreate the 'what if' scenario of a twin cam B as a spiritual successor to the twin cam MGA It would appear that the power and economy are likely to be similar which ever way i go, which is good to know it will most likely boil down to which is cheaper/easier to do Annoying thing is, even if i stuck with injection, the stock intake manifold points at/through the heater box so that would have to be modified, unless i somehow find a rare land rover discovery mpi intake manifold... but then who said engine swaps were easy! haha
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