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twodoorgaz

Series MS Manifold - about time I had one made

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Right. I'd been avoiding going MS for a long time, but I just can't get away from how practical it will be.

On my last build I had the carb and distributor built for me (Dizzy Doctor and Carb Exchange) and still had problems with them - the same cost should cover the MS install on this build.

I'm a simple lad, so before I start getting into the nitty gritty of electronics, I thought I'd start with something I understand - the manifold. The engine is a 17H 2.5 petrol (dressed-up as a 2.25 5MB) and I have a spare intake manifold, so I thought I'd start by getting that modified to take the hardware.

Here's the pics of my existing manifolds:

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IMG_6683.JPG

IMG_6682.JPG

Edited by twodoorgaz

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Now, my understanding is that I need the intake manifold to be changed to carry a fuel rail with 4x injector pots and to have a number of additional ports added for sensors etc - plus I need to get a throttle body attached to the top.

 

My other love is Jeeps, and the venerable old AMC 2.5 petrol engine is a favourite of mine - this was used from 1984 to 2002 (84-88 CJ-7 and Cherokee XJ, 87-2002 in YJ and TJ wranglers and the XJ Cherokee). The old engine has a lot of similarities to our LR engine, having been designed for a truck in the first instance (rather than pinched from a car).

 

From 84-86 it had a single barrel carb (105hp/132 lbft), from 86-91 it had TBI (117hp/135lbft) and from 92-02 it had MPI (130hp/149lbft).

 

The intake manifold actually looks quite similar to a LR setup and once my manifold is altered, the TB should sit nicely where the carb would have been.

 

My intention is to have my manifold modified to take all the jeep components (fuel rail, sensors, injectors, etc) as these seem entirely appropriate for the application and parts availability is superb. Attached is a photo of a jeep intake.

 

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Edited by twodoorgaz

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I'm just looking for a suitable jeep manifold at the moment, but when I have it I'll post pics so we can compare side by side and make a bit of a plan. Any feedback at this stage would be most welcome.

Does anyone have any recommendations for firms that could do the mods to the manifold for me (manufacture fuel rail, weld in injector bungs and MAP sensor recess, etc) ? (I can't ally-weld)

 

A couple of basic questions if I may:

I'm working on the assumption that fuel injection replaces the carb by delivering exactly the right amount of air and fuel needed by the engine at any point regardless of environmental conditions.

Q: But does it actually increase peak power and torque? If so, does anyone fancy hazarding a guess as to what it would do to an otherwise standard  17H engine? (83BHP@4000rpm / 133lbft@2000rpm - approx 24MPG in an 88" SIIA)

Q: from others who have done MS installs, any idea what sort of efficiency improvements I might see?

Q: Also, am I right in thinking that a MS install would not add any additional stresses or strains to the engine?

Q: Finally - I'm also assuming that the intake would not see any great stress and so welding the aluminium casting wouldn't cause any risk of failure - sound sensible?

 

I do have a second thread running about forced induction on this engine - which may or may no be practical, but if it is it would still necessitate the MS install.

Edited by twodoorgaz

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Why not go TBI?  Much simpler.  Just a simple adapter to the current manifold.

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Thank you - happy to do so, but is it a lot more work in moving to multi-port?

 

From my perspective, I'd just be putting my 2.5 petrol manifold in a box with the jeep donor and sending it off to be modified. It would come back with all four bungs welded in, a bung for the manifold temperature sensor and an alteration to the top to change from the two-barrel Webber setup to a single port for the throttle body. Yes, costly, but not much effort.

 

The parts should all be generic bosch, with the exception of the throttle body itself - chosen as it seems to be a nice match to the 2.5 LR engine, its designed for a 4x4 and in terms of size and shape its not a million miles away from the carb it replaces.

 

But... if installing and setting up MS to cope with the multi-port injection is really more hassle then I would gladly take your advice if I could identify a suitable downdraft throttle body to move to TBI.

 

(as you an see I'm still learning here)

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TBI or multipoint , MS won't care, it is just a few more wires.

I always fancied using a diesel series manifold, I think it could be made to work quite easily...

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If memory serves all the kit you need to DIY it is readily available - there's aluminium extrusion in the right shape to make injector rails, and a special drill bit that cuts a perfect injector seat into it. Then you just thread the ends for the fuel fittings, bolt it down, and bob's your mother's brother.

As Bowie says though, SPI/TBI is more than good enough and there's plenty of small TBI units that mount in a very similar way to a carb on lots of small euroboxes, might be an easier prospect to start with. If you decide MPI is the way to go later you just swap the TBI for 4 injectors and tell MS the new flow rates. You're just swinging the injector wires across and maybe joining 4 into 2. MS has 2 banks, but it's not critical, you can fire "batch"  (all at once) or alternating A/B to smooth out fuel pressure but on a 2 or 4 injector 4-banger it's unlikely to notice. Even sequential systems fire banked/batch at high RPM as there's no time to do otherwise and no real benefit off idle.

As for the MAT/IAT sensor, it's not critical - mine was floating free in the engine bay for years, others mount them in the snorkel / airbox. Coolant sensor (CLT) you can adapt to fit wherever there's a handy hole. Vacuum you've already got for the dizzy, just check it's true manifold vacuum as some engines have other vac sources (near the throttle place for example) that don't read right.

Lambda sensor you don't need, if you wanna just tune it seat-of-pants like a carb & dizzy just don't bother fitting one. However, they are cheap, easy to fit, and give a degree of feedback as well as helping economy.

A few links, I haven't checked details:

http://www.emeraldm3d.com/aluminium-fuel-rail-diy-kit.html

http://www.rossmachineracing.com/injectortool.html

http://www.binderplanet.com/forums/index.php?threads/mpfi-drilling-an-aluminum-ihonly-manifold.102078/

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