Lucky Breathes Easy

Hello Simon,

From information that Harvey provided, inside the 't' piece which fitted over the inlet of the air canister, there was a flap which directed air depending upon temperature either from the exhaust manifold on the driver's side or from an air duct aimed towards the front of the engine bay. So yes indeed, all of this would certainly have compromised air flow into the engine.

As Chris rightly pointed out, everything that you do to an engine which has an effect on either air coming into or exhaust coming out of will affect a change in the air / fuel ratio. For the Rover V8 of any capacity, the maximum power and torque at any given rpm requires the air / fuel ratio to be the ideal 12.5 : 1. When I had my Rover with its original 3.5 run on the dyno, the air / fuel ratio ranged from 13.8 : 1 down to 12.5 : 1 right at the end of the run at around 5500 rpm for one tiny moment. For most of the run it was above 13.0 : 1. The air filters were foam of essentially the same surface area as the OEM papers, and the exhaust down pipes were single skin as opposed to double skin where they joined beneath the engine, so flow was a little better. The needles were the original BBG, and as could be seen the engine was running less than ideal in terms of the air / fuel ratio for delivering maximum power.

My 4.6 had its new exhaust system, air system, ignition system all suited to the specifics of the engine which runs a high torque custom ground camshaft designed to improve the performance of a Range Rover, and being an automatic the right outcome for my P6B. Once the needles were polished and the testing completed on the rolling road, the air / fuel ratio ranged from a high of 12.8 : 1 quickly improving to 12.5 : 1 + or - 0.1 for most of the test.

These figures are of course for acceleration, maximum power and torque delivery. When cruising at light throttle settings on the open road or down an express way, the air / fuel ratio is much leaner which is as expected. It just goes to show what a truly wonderful piece of engineering the SU carburettors really are.

I hope that this has been some help to you Simon.
All the best,

Ron.
 
testrider said:
If you raise the back of the bonnet then you will get rid of a lot of heat but it will also be sucked into you heater box too.

It might be better if you could keep the back edge of the bonnet sealed and maybe louvre the panel either side of the heater box so that it could exhaust away from the fresh air intake.

I've always wondered why there wasn't a cold air intake kit for the carbs though, I'm sure the engine would run much better if there was one.


I definitely agree that the engine would way better if it had a cold air intake. It provides cooler air, which contains more oxygen and transforms into a stronger explosion in the combustion chamber. Thus, more horsepower and torque is achieved. :)
 
lakwandaphillips said:
testrider said:
If you raise the back of the bonnet then you will get rid of a lot of heat but it will also be sucked into you heater box too.

It might be better if you could keep the back edge of the bonnet sealed and maybe louvre the panel either side of the heater box so that it could exhaust away from the fresh air intake.

I've always wondered why there wasn't a cold air intake kit for the carbs though, I'm sure the engine would run much better if there was one.


I definitely agree that the engine would way better if it had a cold air intake. It provides cooler air, which contains more oxygen and transforms into a stronger explosion in the combustion chamber. Thus, more horsepower and torque is achieved. :)

Hmmm or big scoops that taper down in a way that enables a ram jet effect (helpful at supersonic speeds :LOL: ) or if if you plan on interstellar journeys :roll:

Graeme
 
A bit like this perhaps? Or, here's one I did earlier. The louvres can't go any further back because of the bonnet structure. They are positioned as far as possible to be over the exhaust manifolds. This bonnet is now waiting to go onto Lucky after a coat of paint. The idea was copied from the P7 factory prototypes which had this arrangement. Also used by a lad in NZ.









Chris
 

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Chris; did you press the louvres as a DIY? Interested in how this was done


oldsite.p6club.com/improvingthep6.doc

Believe the Kiwi car is pictured in this P6Club posting; sorry I don't now how to copy the picture from the Word .doc...I've exchanged emails with the owner, who lives in Northland, with the idea of finding what engineering shop did the P6 louvres; but he couldn't help as he didn't actually get this work done

Asking around it looks less of a drama to louvre aluminum than steel, should result in improvements to under-hood cooling
Thought of getting a bunch of smaller louvres pressed to skirt around the bonnet bracing issue, like this:

louvres1.jpg



GW
 
The Blue car never ran for long enough to make an informed judgement on the performance of the louvres. They were pressed directly into the bonnet by a firm near Derby. The difficulty is that you need a fly press big enough to take the whole bonnet and they are pretty rare in the UK. You finish up in the hands of the veteran/vintage specialist restorers, which can be expensive!

Chris
 
You're right, just what was available at the time. In fact Lucky has one of each! Not an issue as they are hidden away inside the airbox.

Chris
 
Sorry to butt in, but are you sure that these cheapo aftermarket filters are actually an improvement ? Do they flow more air, and if they do, do they filter properly ?

I know they're expensive but I'd rather have a proper K&N / Pipercross, something like that.

I'm starting to go off cheap stuff, had a few things recently that have just proven to be cheap rubbish, rather than just cheap :(
 
Well I took a very carefull look at them, and I'd be inclined to describe K&N's as the cheapo ones by comparison. In the first place, I've never trusted oiled filters (which K&N are) ever since I first started in engineering and saw some of the abortions around on big plant after a couple of years in service. Secondly, the increase of surface area of filter medium for the air to pass through is so dramatic that you'd have to have an extraordinarily incompetent filter medium for there not to be an improvement. So for my money they win all round over K&N's. Plus the conical filter type as a breed impose far less dramatic changes of direction on the airflow than the ones installed by Rover.

Chris
 
Hi Chris,

My Rover seems to be a good test bed for a whole range of things dating back to the mid 1980s. My original engine ran with oil soaked foam filters from 1987 till 2007, covering a distance of 140,000 Miles over that period. I never saw anything that gave me concerns in terms of their filtration ability. Prior to that for the first 13 years and 63,000 Miles, OEM paper filters were used. My 4.6 runs with K & N filters, and after the first 40,000 Miles I removed them for a good inspection. No dust was found inside the carburettor throats or within the air canister on the engine side. Given that dust is a far greater problem in Australia than in the U.K or for that matter in the vast majority of countries around the World, I was more than pleased.

I have read articles where they bag oil soaked filters, but from my own experience over 24 years from using them and 186,500 Miles (300,000km) to date, no such problem has ever been found.

Ron.
 
Hi Ron

It wasn't the ability of the filter to prevent muck entering the engine I was criticising. Rather, its ability to let air enter! In my experience, oiled filters can block the pores far too readily to the detriment of engine settings and even sometimes the ability to run at all! I was always taught that oiled filters were invented by accountants who didn't like paying for new ones, whereas non oiled filters were designed by engineers who understood the need for air!

Chris
 
As far as oil soaked filters are concerned, I think you guys are being a bit hard on them for not being free flowing.

The helicopters I work on use oiled inlet barrier filters and they are a great filter medium that flow enough to keep a 770kw turbine fed with clean air. They do need to be maintained correctly and that includes oiling them properly.
 
The overall implication being that the power increase chris has seen more likely came from the increase in snout diameter on the filter housing rather than the change in filter itself?

Rich
 
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