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RPI custom air intake - views/comments sought

3888 Views 20 Replies 15 Participants Last post by  big-t
Anyone have a view, comment or any experience of this mod. I have a 1998 with 5.0 litre stage III engine (but not on gas).

http://cgi.ebay.co.uk/LPG-Gems-V8-P38-R ... 2304dfc55d

Thanks Andy

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An overpriced shiny K+N filterhousing, nothing more.
Waste of money. Even if it added 10 hp (which it won't) you'd never notice it.

by encasing the filter within the stainless tube it will restrict air intake as opposed to a cone filter without the tube?

Stick with the standard airbox
I'd expect better from RPI, the item looks attrocious, look at the weld :shock:
my Grandma can weld better than that and she has been dead 20 years!

Like others, thats a shocking piece of tat for RPI to put their name to!
Thats just the kind of c-ap I'd expect from RPI...... :roll:
All bling, no sing. I wouldn't touch it with a 20 foot pole.
A $300 18 inch section of pipe, does that include a bridge?
Thanks everyone for your (erudite!) comments - next question: would an engine like mine benefit from a cone filter installation or not. I'm not really scraping around for horsepower but if the engine will breath easier I'd do it. If so, what would people suggest - K & N, ITG (Maxogen barrel type - got that from the JE Engineering website). I have the K & N in the standard box and am aware of the polarised views about that.

Thanks very much.



The current airbox arrangement takes it's air form between the inner
and outer wing, so is relatively cool. Fitting a cone filter (of whatever make)
will mean it's drawing in warm enginebay air.
Any 'performance gains' will be negligeable and not noticeable by your 'buttdyno'.

I had the cone fitted to my p38, i started looking into it when my LPG system started to play up.
In the end i reverted back to the std air box which i found to be much better.

I did not find any difference in performance.

Once changed back i replaced the LPG system with a sequential system keeping the air box and have never looked back.
i was told by someone on here that the air box is used for modded engines far in excess of the 4.6 std.
That being the case it's able to suck more air than you need. (and keep the air cool)
Typically, factory air boxes are very well designed and meet the needs of the vehicle. I have found that aftermarket cone style filters or intake systems rarely add anything more than sound. You could always go with a high flow filter such as K&N and drop it into the stock air box.
Just to be picky, that pic (from the RPI catalogue) on the ebay auction, shows the airfilter fitted to the downstream side of the MAF! That's a fairly significant error.. :)
Thanks everyone for the replies - I think I shall stick with the original set up.

I've spent four years tinkering with mine getting it to the best condition I can I guess I just have to start accepting that maybe there is nothing more to do - except perhaps that Thomas 327 compressor, a recarpet would be nice, leather trim on the glovebox and door handles like on the Autobiography models, black supercharged wheelecaps and what was that MAR repclacement device on a recent thread .............



Ok, BTDT with the K&N filter.

Not only is this "LPG Gems V8 P38 Range Rover K&N ultimate intake system" a heap of crap, it is an EXPENSIVE heap of crap. The ONLY good bit is the K&N filter and I SERIOUSLY doubt that the housing in which it is fitted will improve anything - not even the appearance. Don't waste your money on that! The K&N filter is another story (again :) )

In MY personal experience, the K&N filter "DOES" improve the breathing and performance AND horsepower of the RR. The K&N subject has "been done to death" many times before in other posts on this and other forums. There are many fore and probably just as many against the K&N filter.

My RR HP was boosted by 5hp and the engine did breath much better, YMMV :)

See my post here ...


Personally I WOULD recommend the K&N (standing by for objections etc), but to each his (her) own. When my air filter is due for replacement I will be fitting a K&N filter BUT I will use the original RR housing.

I think it is worth the expense to test it for yourself. You may completely disregard mine and others' comments and judge the K&N for yourself. You are the best judge for YOUR needs.
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RPi do not even own any sort of bench or wheel Dyno, so you may want to take any sort of Bhp claims with a pinch of salt.....
Not sure that one is for the P38 but it looks pretty enough.

Thanks for your comments Peter. I have had a K & N for a while now, perhaps 3 years. I installed it along with some other mods including upgraded camshaft and Adams chips (this was before my high spec rebuild to 5.0 l) and there was a definite improvement but doubtless that was due to the cam shaft at least in part.

The only issue I have is that I consistently have the fault 'P1179 AMFR correction at its max negative value (driving cylce C)'. I have it cleared and it always comes back. Most recently, I have cleaned the MAF with some MAF cleaner (spraying it inside across the wire mesh whilst giving the engine a good rev - crikey hope that's right). But it's back again. Also, I didn't notice any differnce once I'd cleaned the MAF - may be it just wasn't dirty.

It has been suggsted to me that it is a consequence of the Adams chips? I just wonder if it is related to the K & N filter and whether or not there is a long term damage potential. In fact, what does the fault mean? I haven't got round to clearing the fault and putting in a standard filter and seeing what happens, which is I suppose the next step.


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As someone that has actually done the dyno testing I know first hand that it's al a load of bull plop. I'll stick with paper and not risk MAF faults or bother with oiling an overpriced piece of piece of foam in chicken wire.

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