BOA or BOB

[waynes world]

Now this will be the most complicated bit for me on my build, i will be gettign a sierra 4x4 2.9i for the donor but fitting a 24v cossie v6 engine, now its the electrics bit i need to get to know about the engine, as in which will the easiest to fit in the BOA or BOB engine, i will find a scarpper and remove all i need form it to fit in my roadster, so if anyone can give a list of what i need, upto now i know i need the usual loom, ECU, but is there a censor on the ignition side to the ECU i need to remove?

I know its a bit off before i need the engine but to plan ahead and gather as much info is best i think, and time to gte my head around it all:eek:


cheers


wolly:D

[HandyAndy]

I think forum member "TwinTurbo" will be a big help on this request, his knowledge of Sierra,s is amazing ;)

cheers
andy

[waynes world]

I will wait to see if he spots this thread, if not i will PM him.


Oh yes and i will be going with BOB:D :D

[Cyberbeej]

The BOA engine is easier on the wiring side compared to the BOB engine.
All depends on whether your keeping the loom/ecu etc plus the BOB is standard with the auto box and will require a hybrid gearbox or a rare V6 type 9 for manual.

Probably better with the BOA and it comes with a Manual box usually, Plus if fitted with the BOB cams it makes more power over standard too.

I'm not the expert on this as my BOB is being fitted Microsquirt so i wasn't to bothered with the wiring dilema.

Just wrote all that and now think that its probably no help at all.......

[Davey]

As I understand it the main differences between BOA and BOB are mechanical being different profile cams and a duplex chain instead of simplex. Both BOA and BOB were all fitted with slush boxes as standard and as far as I'm aware were only fitted in Granada/Scorpio models. BOA fitted with BOB cams gives more power than stock BOA but not more than BOB. BOA gives 195 BHP at 5500RPM in stock trim. Electrically there is little difference between them.

As for gearboxes I would say go for a MT75 hybrid, the type 9 is reputedly good for 200 BHP but has a nasty habit of releasing its internals above this figure, with just a sheet of 1.2 mm ali between the box and your legs would you really risk it? MT75 hybrid needs to be made up from a V6 XR4X4 box and a 2 litre box, essentially fitting the internals of the 2 litre box into the V6 front casing, I know I've done it (although I'm about two years late with writing it up:( ).

D.

[twinturbo]

No Standard Production V6 Granada/Scorpio MK3 had a manual box (with the exception of the 4x4) although a small number of special orders were done for the Granada, but nobody knows if there was ever a Scorpio manual special order (those that have delved into the programming of the ECU via FDS or WDS have found an option to switch to manual mode.)

Hybrid boxes must be made in one of two ways.

1) 2.5 TD box from scorpio using the XR4x4 front case.
2) 2.0 Box but removing the mainshaft and replacing it with the XR4x4 one and front case.


BOA vs BOB.

BOA is the simpler engine using a single long timing chain, and one tensioner. It has a fixed inlet system that is fairly restrictive. The big weakness is failure of the chain tensioner blade which will result in the chain jumping and wrecking the engine. Replacement blades and nylon covers are available.

Wiring is fairly straight forward, you must retain the Lambda sensors for correct running (one per side) and you will not need CATS for the IVA. the emissions gubbnings can be junked (although some report better economy with them on) .

There are two types of loom, early cars had a single fusebox and this has an easy couple of plugs to hook up the engine loom. Later cars were built like the scorpio with twin fuseboxes and this is not as easy as you need to make up relay holders and join a number of wires that were part of the fusebox.

Using BOB cams (with correct 95 wahsers) and Vauxhall V6 injectors will give a bit of extra power/torque.



BOB. It's more compact in size although a smidgen taller, it uses one chain per bank with a tensioner per bank. It's more complex but there are less reports of problems.

Using the original wiring requires the use of a lot of original loom to retain the PATS anti-theaft system (some say they can get round it but no details). The alternative is to use BOA loom and ECU although an RPM switch will be needed to work the VIS valve which is important for good smooth performance. The loom in the engine valley suffer from insulation breakdown so should be checked.

Againg you will need to retain the Lambdas and now the CATS as well. Original scorpios have 4 Lambda sensors but the rear pair are just for monitoring and won't cause a problem if removed.




TT

[twinturbo]

P.S.

Water Pumps for BOB's are like Rocking Horse...... Don't belive a motor factor if they say they have one it's almost 100% going to be a BOA or 12V.

Thermostats for the BOB cost a fortune £80+ last time I looked.

BOA cam covers have integral gaskets and are not available separately. Mike at boost Performance has remade these along with other items.



Type9 V6 boxes

Given the weight of the roadster they should last OK, A set of new front needles and main input bearing would be a wise move though.


Spigot Bearing.

A spigot bearing must be fitted to the end of the crank to take the nose of the gearbox input shaft,



TT

[waynes world]

Thanks guys, great info there, i will very likely need help to wire the engine up, i will be getting the complete engine with ECU and loom and as much of the exhaust as possible to modify aswell as lambers. There doesnt seem to be much difference realy then, well not that you could tell in a roadster, so i think i will see what the difference is in the service parts and availability.

On the gear box front, as i am going 4x4 i am getting a post 1995 sierra 2.9i 4x4 and as this has the MT75 i can swap the standard 2.9i sierra for the Granada 24v cossie.........so no need for the hybrid:D


thanks for info


cheers

wolly:)

Edited to say, i could be wrong about the gear box???

[twinturbo]

On the gear box front, as i am going 4x4 i am getting a post 1995 sierra 2.9i 4x4 and as this has the MT75 i can swap the standard 2.9i sierra for the Granada 24v cossie.........so no need for the hybrid:D




So your planning a 4x4 Roadster???

There were no sierras after 1992 (except late registrations)

V6 MT75 4x4 came in in 1988/89 and is fine on a BOA/BOB.

TT

[waynes world]

Hi TT, yes planning 4X4 roadster.

Just realised what i said, i meant a post 1995 Scorpio for the BOB, and a 2.9i 4x4 sierra for the MT75 and running gear.


Cheers

Wolly:D

[Davey]

Why not just go with the 2.9i out of the Sierra though? It'll be plenty powerful enough to propel a lightweight car although I really do think you're going to have major problems doing the 4X4 thing.

D.

[mark100]

my father in law as sat in his garden a xr4x4 with a boa conversion in it from my old fsoc club days im trying to get him to it let go you know the old saying ill get that back on the road soon and he wont and a few 2.9 12v,s if you need anything im hopefully cleaning the garden out (to make room for a full blown garage workshop i might let him use :p ) this weekend or next