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Hi all,
Something I've been wondering recently...
...when you see older cars that have been converted to mappable fuel injection via MegaSquirt, OMEX, Emerald Ecus etc, they all seem to go the route of Individual Throttle bodies. (based on what I've not seen, not saying this is always the case!)
However, what about using just one TB as per many modern cars come out of the factory?
My understanding of it is that using ITBs will give you better throttle response. However, with just one throttle body, it could make producing a manifold easier.
I'm thinking:
Tap the original carb manifold for the injectors and make an adapter to mate a suitable thottle body to it where the carb normally sits.
Admittedly, this might not give you all the benefits of an ITB setup, but you would still get the benefits of mapped fuel injection, such as smoother power/torque delivery over the entire rev range, improved fuel efficiency etc. (I realise that fuel injection doesn't necessarily mean more peak power/torque)
When I think car stuff in my head I always apply it to imps, because that's what I know. And when I think of ITBs, I can't help but think that there are few available that would be sufficiently small for a standard imp. Even small cc bike items would need considerable downsizing to get from the throttle diametre to the diametre of the inlet port.
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Oh Wait....
I think I've made a boo boo haven't I....
When you have a single throttle body, it is mounted before the plenum isn't it?
In that case, if you were to use the original manifold, you would have to fabricate and mount a plenum to the original manifold and then mount the throttle body to that?
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v8ian
Posted a lot
Posts: 3,832
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Why not use a 40s sidedraft manifold with injector bungs welded in, then you can use a ratty old pair of scrap webbers as TBs
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Atmo V8 Power . No slicks , No gas + No bits missing . Doing it in style.
Austin A35van, very different------- but still doing it in style, going to be a funmoble
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If you happen to own a traditional American V8 then you can buy aftermarket EFI kits just like you describe. There are even ones which are designed to look exactly like a single carburettor setup.
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1941 Wolseley Not Rod - 1956 Humber Hawk - 1957 Daimler Conquest - 1966 Buick LeSabre - 1968 Plymouth Sport Fury - 1968 Ford Galaxie - 1969 Ford Country Squire - 1969 Mercury Marquis - 1970 Morris Minor - 1970 Buick Skylark - 1970 Ford Galaxie - 1971 Ford Galaxie - 1976 Continental Mark IV - 1976 Ford Capri - 1994 Ford Fiesta
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I think the point is that it can be done in an OE kind of way, but if your going to all the trouble of doing it why not got the whole hog? most people do it for performance reasons, hence one choke per cylinder.
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Volvo back as my main squeeze, more boost and some interior goodies on the way.
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If you happen to own a traditional American V8 then you can buy aftermarket EFI kits just like you describe. There are even ones which are designed to look exactly like a single carburettor setup. what like this one  ;D  full multi point efi setup with 1000cfm 4 barrel throttle body sits on the manifold that is based around the edelbrock victor carburetor manifold though on this particular one has different footprint to a normal Holley type 4 barrel |
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Last Edit: Feb 4, 2011 20:24:06 GMT by Deleted
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Single tb's are cheaper, hence why volume manufacturers use them.
Plenums and single TB's don't work well with big cams either.
BMW K100 tb's are small enough for an Imp....
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Koos
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Cheers for the replies guys.
It's not specific application I'm really curious about. I'm more just wondering if there is still any point in doing it with a single throttle body
Any idea what size they are mdh?
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It is easier and cheaper to use a single throttle body with megasquirt. I think what you might be seeng is the large amount of people sitching to megasquirt so that they CAN run ITB's.
Yes there is a good point to doing it with one throttle body. It provides excellent results that way. In fact I have never seen an ITB system on standalone that was as driveable as a single TB system.
Dialing in the acceleration enrichments is far easier with one throttle. Makes for a simple transition to boost as well.
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There is a very huge database of Throttle Body Inj junkyard adaptation and reprogramming generic GM 4,6, and 8 cyl ECU's to run them on any engine. The GM programming codes were cracked more than 15 years ago. The ECUs are just about free at the JY's. And GM used bolt patterns which it adapted to trad carb baseplates in many cases during the 80's transition phase from carbs to TBI. You can DIY all this, or pay somebody.
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 Team Blitz Ford Capri parts worldwide: Restoration, Road, or Race. Used, Repro, and NOS, ranging from scabby to perfect. Itching your Capri jones since 1979! Buy, sell, trade. www.teamblitz.com blitz@teamblitz.com |
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I will shortly be swapping from ITB's to a single Lancia delta TB and a large plenum on my imp, it will allow me to get the injectors right next to the head pointing at the back of the valve. I am an ECU calibration engineer by day, and I can tell you that getting the injector closer to the valve will make tuning the vehicle orders of magnitude easier. The further back the injector is the less responsive the engine will be to changes in throttle position, as there is a larger port area to wet with fuel during transitions. And single TB / Plenum setups do work rather well with big cams, ask the S1600 boys -  220bhp from a 1600 requires BIG cams! |
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Last Edit: Feb 5, 2011 8:41:35 GMT by Blown_Imp
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Cheer guys.
James.... that's interesting. I thought Malcolm always said that you should put the injectors as far away as possible to help with atomisation?
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It does help with atomisation and ultimate power, but it is a bit pointless if the engine boggs down when the throttle is pressed.
The issue is that if the injectors are further outboard there is a larger port area, when the throttle is closed the fuel on the walls is pulled off and used, the walls go dry. As soon as the throttle is re-opened any fuel injected wether that be accel enrichment or just the normal pulse will go to wetting the walls rather then into the cylinder. The result of this is that engine will either go very lean then spot on, or if you tune out the lean bit (that causes hesitation) it will then go very rich (which causes the engine to bog down)
Ideally you need two sets of injectors used in a semi sequential set up, where the outboard injectors do most of the fuelling and the second set ideally in the head pointing at the valves does accel enrichment and initial transient fuelling. Complicated.
At the end of the day, outboard injectors are worth a couple of hp even when the rest of the engine is optimised. Reducing the cars weight it worth more than that every day of the week, and that combined with the responsiveness issue, I say don't bother!
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Kai
Part of things
Posts: 276
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Why not get a set of DCNF or DCOE throttle bodies? Fit on the same manifold as carbs, and no need for a plenum  |
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Why not unplumb the original carb and use it as the throttle body? |
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Kai
Part of things
Posts: 276
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There's the 'bodge' way, and theres the proper way. Either do it properly, or it's not worth doing, imo. If you want to do EFi, it's not all that difficult. I imagine a pair of 40's on a 998cc Imp engine would be okay - if paired with a decent cam, and supporting exhaust mods. Bike throttle bodies would work fine as well - as they're designed for engines from 750cc to 1200cc anyway - assuming you're using something like megasquirt, you simply map the system for smaller injectors |
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I'm mixed up by your post. You extoll virtues of the ITB's and the downsides of a single TB, and yet it's your plan to install a single TB? How will a single TB allow you to get multiple injectors right next to the head anyway? I'm totally lost, unless my terms are upsidedown with yours or keyboard dyslexia has struck! Norm I will shortly be swapping from ITB's to a single Lancia delta TB and a large plenum on my imp, it will allow me to get the injectors right next to the head pointing at the back of the valve. I am an ECU calibration engineer by day, and I can tell you that getting the injector closer to the valve will make tuning the vehicle orders of magnitude easier. The further back the injector is the less responsive the engine will be to changes in throttle position, as there is a larger port area to wet with fuel during transitions. |
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Team Blitz Ford Capri parts worldwide: Restoration, Road, or Race. Used, Repro, and NOS, ranging from scabby to perfect. Itching your Capri jones since 1979! Buy, sell, trade. www.teamblitz.com blitz@teamblitz.com |
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I'm mixed up by your post. You extoll virtues of the ITB's and the downsides of a single TB, and yet it's your plan to install a single TB? How will a single TB allow you to get multiple injectors right next to the head anyway? I'm totally lost, unless my terms are upsidedown with yours or keyboard dyslexia has struck! Norm Norm, TB != TBI. What you're talking about is a Throttle Body Injector system, where there is an injector built into the throttle body, which often bolts onto a carb manifold. This is often known as single-point injection. What BlownImp is suggesting is a single throttle body (with no injector in it), with a plenum-type manifold and an injector in each runner - known as multipoint injection. This is used on most OEM injection systems now. I think the reason that he's going to a single throttle body is that most individual throttle bodies (motorcycle ones anyway) have the injectors in the body, so contribute to a larger wetted surface in the manifold, due to the distance between the injectors and the valve. |
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Exactly! Here is a multi point 8 injector system -  The TB goes on the square flange |
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That S1600 engine only used a single t/b due to regs, if it didn't have to use single it would b on 4. regarding injectors further away, have a second set, i.e 8 on a 4 cylinder engine, so best of both worlds - one set in the manifold pointing at the valves for small openings/low engine speed, and the second set in the throttle bodies or even externally pointing down the trumpet  I sort of did what you are thinking of with your IMP, with my 1.9 205 gti, yes it was originally injection, BUT, stone age clockwork Bosch Jetronic, flap type AFM, throttle switch and a Vacuum advance Dizzy. I sourced a Bosch Motronic MP3.1 ECU from a Citroen ZX 1.9i Volcane (essentially the same engine as the 205) which is a coilpack + MAP sensor, proper throttle pot. Vastly improved manners, improved MPG, nicer torque curve, also mappable Afraid I can't help specifically with the IMP application though, but do get where you're coming from |
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;D
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