Hello fellow DII owners. So it's a simple question with a maybe not so simple answer but here goes. What can be done, within reasonable means, to get more power out of our motors? In my mind, a full exhaust and intake would have been sufficient and within reasonable means but then our MAF would mess up having a custom intake, and I heard that an exhaust system is near meaningless with out lifters and cams(Can someone elaborate on this?) and a port and polish on the block. Are the things I've stated true? I can feel a beast under the hood, it just needs something to unchain it...looking at stock headers even makes me feel like I'm choking. So lets talk about it please. Whats been done and proven to work and not work? If our MAF if so sensitive, any aftermarket beefed up versions? Thanks for any and all input thrown in here, I think this could be an informative thread.

Best,
-Ashtray

 

The 4.0 can be built up to a 5.2, but that means a complete rebuild.
The Rover 4.0 is to Europe what the Chevy 350 is to the US.
What they mean by cam and lifters is to change the length of time the intake and exhaust valves are open to let in more air/let out more exhaust.
But to do it properly you also need to change the stroke (how far they move)of the pistons.
Basically, without a full rebuild and a ECU re-program you cant do anything.

 

So it's rebuild the motor, or nothing at all....grim this is looking. I was hoping at least an exhaust system from the headers back would be something.

 

No. These motors don't have a chance. They sound powerful, but as you can tell, are not. Some even report backpressure and o2 sensor problems with headers and an exhaust.

 

Well that blows. LOL! haha. How much, roughly, does a rebuild with lifters and cams and changing the stroke and reprogramming the ECU run these days? I'd really LOVE the extra power...speaking of which, how much would a rebuild net? Also, in the calculation, you can include labor because I'm sure I would not be able to change the stroke of a motor on my own.

 

What the hell is wrong with Europe then? a chevy 350 can take anything you give it with no problems. It can be modified six ways from Sunday and still turn.

I'm guessing it's the electronics that limit the 4.0's mod-ability. No doubt the engine is stout and would benefit from intake, exhaust, port, polish, etc.; sounds like the brain needs an update as well.

 

Uhhh nah, it's just an old, poor, inefficient engine design.

 

Put in a M series BMW engine. That solves it.



The 4.0 is at best frail.
The 4.6 even worse.

You add even any additional heat from your mods and you'll ruin the engine.

 

Built for bouncing in the back country, and towing your 426 HEMI Dart to the track.

See The Wedge Shop - Fast. British. Reliable , and if you Google you'll find many examples of these engine modded in a variety of ways. Even older articles where guys were removing the carbs and adding the Lucas fuel injection. Most of us are just happy to have it crank and run without overheating.

Then there is always nitrous, but results will be short lived (along with the engine).

 

Yep... these are an aftermarket dead end as far as the motor goes... you want some more pick up, lose some weight in the tire area, and gear the diffs up. Otherwise you are looking at huge expense for very little gain, with an even less reliable system. Clean up the intake real well, make sure your cooling system is top notch, keep air in the tires proper, clean out all the junk, get rid of the rear tire spare, make sure the airfilter, plugs, coils, o2's are serviced well, check for exhuast leaks, and all you hope for is a better then average runnin power. You wont be anywhere near advertised power after a decade anywho hahaha. ditch the d1/2 and save up for the nevew models that have alot more power for the factory, youll probably spend less than a quarter of what it would take to get a disco up to that level.

your limited by your emissions laws on what you can do with the exhuast. some states limit any aftermarket changes other then a catback exhuast, and even then you might have noise regulations or equipment certification issues. other then that, some states require that hiflow cat weld ins or replacement catless ypipes might be illegal from the get go, require that a certified state emissions exhuast shop do the work (which they wont because they will only replace it with factory cats) or perhaps you are lucky and dont have any of those requirements. it will also be a pain in the *** to find a shop evne willing to custom fit tubes on these things... especially if you have secondary air. and even if they delete it, youll have to have someone program that out of the ecu, which i dont even know can be done. i dont even know of any 3rd party programmers for the lr computers?? or live with the code for the removed system, and then have to deal with all that again when you go to sell it.

you could get a "port and polish" job but this isnt grand tourismo. youll have to find someone whos willing to do it, and id give you credit if you can even FIND someone whos ever done it before in the country. youll have to pull the heads and send them out to get rebuilt and machined... but the factory throttlebody will be the restriction there anyway, and no one makes aftermarket larger diameter ones. but even after that (I'm guessing $2500+ range cheap, $4500 decent job not including rebuild part costs) youll see maybe a half dozen or more wheel hp increase. to get more, youll also need bigger injectors, and a custom ground cam to match the bench flow marks of the heads (if the guy who does the job even has a bench flow meter to begin with). AND, i dont know of anyone who supplies aftermarket fuel injectors for discos to begin with. THEN after that, youll have to find someone who can reprogram the ecu to know what to do with the new cam and fuel injectors, or it will just run rich as hell, destroy your o2's, wear out the upper cylinders and contaminate your oil so bad youll be runnign worse then stock faster then it takes the computer to try to compensate.

in reality, if you are dead set on this and have money to burn, it certainly can be done.

if you dont have the money and cant find the garages and people to do it for ya, youre stuck doing just a strip job to find some extra horsies, such as removing the a/c system for weight, and having a bypass pully installed in the compressors place, that might net some very small gain, but then you lose the a/c, is it worth it? i'm guessing less then 5hp to the motor, which will be negligible to the wheels since its turning a fulltime active 4x4 system in a truck that weighs the same as a ww1 armour personell carrier.

engine swap is a possiblity, its been done a few times before... but the cost is nearly the same, the complications are 4x greater, diagnosing problems in the future becomes a **** shoot and most garages wont be willing to look at it, and if the engine is just slightly more powerfull, you also then have to prepar the transmission, transfer case, drive axles and drive shafts too! easily doubling the cost right there. $10k+ easy estimate... and for what exactly?

only real way to get these "faster" are to swap the diff gear ratio (loosing top end speed for a mechnical gain in torque to spin up quicker), getting lighter rubber on your wheels (and get aluminum wheels if you have steel currently) so they can also accelerate quicker, but then you sacrifice offroad ability (hard light rubber tradeoff means less traction, certainly compared to an allterrain or mud/offroad dedicated tread) and also sacrifices in reliability - steel wheels are much more cabable of taking hits from rocks/curbs (front and side mind you) to clear obstacles, or whack things on the trail.

hope this all helps! i wont even get into remote mount turbo/supercharger, because the cost will be nearly the same, and headgasket changes will become as routine as fuel fill ups... plus your still stuck trying to figure out the injector change and programming... and if you remote mount it, you lose ALL wading/offroad capability, and you might as well just go buy a civic r type. or strip out the interior of the disco, retro fit it into the interior of a diesel suburban and crank the **** out the high pressure pump for less then you spent on the disco in the frist place