Can I pick some GEMS brains ?

[JaapRoskam]

I have owned a 1996 P38 GEMS since 2013. Drove it until 2016 , then had a bad a tractor accident and put the car to rest in our dry (central NSW) paddock until recent (early 2022).
In all those years I let the engine run every few months - drove it on our 400 ha property a little and that was it. All electrics and EAS etc still work 100%.
In 2014 replaced the heads after a head gasket failure , was so lucky to buy a slightly skimmed and ported 3.9 set of heads, put helicoils in the head bolt threads and then that tractor got me. 28 fractures at age 62 is not wise. But I came out as good as possible.

Fast Forwards January 2022 >> I have driven a Nissan Patrol Safari since 2016 but the Range Rover bug bit me again >> Started at first go , rough but easy going. >> But the petrol smell out of the exhaust -- ouch !! >> I made a plan : start withy easy affordable improvements , if an improvement would not hold I would stop and sell the car.
1: reconditioned injectors - Bought 8 reconditioned Bosch 4 hole injectors from a fabulous USA seller. >> Great improvement - engine sounded less rough , less fuel smell.
2: new fuel pump - the one in the tank was already an aftermarket one installed by previous owner before 2013 and I had the idea it worked not as designed. >> Minor improvement but ... peace of mind.
3: adjustable fuel pressure regulator from RPi V8 in the UK - they advised to set it at about 38 Psi >> Incredible improvement - engine runs very smooth , near zero petrol smell from exhaust.
4: In the process replaced the MAF and TPS as the first one was a bit damaged and the second one measured a dead spot when tested with an Ohms meter.
5: New spark plugs (set the proper gap width) ALL the spark plugs stay now beautiful light creamy in color, new ignition leads , cleaned all earthing contacts in the engine bay (don't overlook the ones UNDER the fusebox) , added a few critical earth wires (like from alternator chassis direct to battery instead via vehicle body), gave the radiator a big clean on the outside (amazing how dirty).
6: Test pressurised the cooling system to test for leaks - that test kit is worth its cost in pure gold: I discovered 4 micro leaks - all an easy fix instead of one : the front cover gasket weeps some coolant 'tears'.

The engine now starts as if turning on a light. Rums very smooth and cool and 'clean'.
BUT:
Lacks torque , I knew from the 2013 head job that the Camshaft was not perfect , but at that time did not recognise it as important enough to change....
Next job ?
A Camshaft and the lot of other parts that go with it.
A standard camshaft or a piper torque Camshaft ? (I intend to tow a caravan).
If that is a serious improvement perhaps even a Mark Adams Tornado chip.
QUESTIONS:

Anyone with experiences with a higher torque (piper) camshaft - or is a standard OEM camshaft just as good for my 'old fart' use and occasional caravan towing ?
Any experiences with the Tornado chip ?
What minimum cylinder compression pressure is still acceptable ?

Any suggestions ?
What I can do to improve the engine without going overboard money wise ?

THANKS !!

[old dirt bikes]

Hi Mate,
I bought a 1995 Range Rover HSE 4.6 Gems and drove it for about 18 years and had very little trouble with it. About 5 years back I bought another one cheap and let it sit in the back yard for a while to mature a bit. I pulled the engine to fix the oil leaks. So that turned into a 5lt with top hat liners, forged pistons, aftermarket cam, tornado computer etc, etc. So if you are going to change the cam I would recommend an after market one, and a computer upgrade will work wonders. I drove about 600 odd klm on the weekend and towed a tandem car trailer. I didn't really know it was there on the way down. We put a big milling machine on the trailer and covered it with a big tarp as there was rain around. The tarp turned into a big sail. So about 2.5 ton all up in tow and the Range Rover performed really well. average speed about 90kph with an average fuel consumption of 16.1 lt per 100 k. , for the round trip.
Regards,
Alan

[JaapRoskam]

Hi Alan

That sounds great. I guess my caravan tows a bit lighter - it is a streamlined Phoenix with big 17 inch wheels on an ALKO torsion suspension. Empty weight about 2 tonne.

Your Camshaft / Tornado combo seems the way to go. At the moment I'm not brave enough to do the pistons as well. But on the other hand .... its tempting to do it your way with an old donor vehicle in the yard.

What sort of money would I be looking at to have the pistons etc. done your way ?

Cheers:
J.

[PhilipA]

Really the LAST thing you should change is the camshaft. (except to replace it with a new one as it is most likely worn out. The biggest problem with RV8s)
A GEMS cam would be very much like a 3.9 14CUX cam, and they are a good compromise for torque and power.
Low down torque is really a function of the engines being retarded to reduce Nox.
I gained about 30% torque under 3000RPM by a dyno tune and Unichip which gave much more advance at lower revs.( with a 14CUX)
You would need a reflash on a GEMS and I doin't know who could do that.
Maybe talk to Graeme Cooper who has done quite a few Dyno tunes.

Regards PhilipA

[JaapRoskam]

Hi Philip
Interesting you suggest NOT to change the camshaft.
With all the web talk / advertising for a higher torque / faster / more economical camshaft one can get a bit confused at the very least. Mine is definitely worn and needs replacement - the lobes are golden brown etc. - I do not intend to tow the caravan for to long - or very far - just an occasional trip to the coast (500 km ) . Living remote I mainly use the Rangie as a long distance shopping trolley.
What makes you advice to stick with the standard Camshaft?

Thanks
Jacob


Really the LAST thing you should change is the camshaft. (except to replace it with a new one as it is most likely worn out. The biggest problem with RV8s)
A GEMS cam would be very much like a 3.9 14CUX cam, and they are a good compromise for torque and power.
Low down torque is really a function of the engines being retarded to reduce Nox.
I gained about 30% torque under 3000RPM by a dyno tune and Unichip which gave much more advance at lower revs.( with a 14CUX)
You would need a reflash on a GEMS and I doin't know who could do that.
Maybe talk to Graeme Cooper who has done quite a few Dyno tunes.

Regards PhilipA

[PhilipA]

What makes you advice to stick with the standard Camshaft?

Over the years on this forum many people have changed camshafts and there have been numerous discussions.
Even what are advertised as "high torque" camshafts are often more radical than a stock cam.

Remember that many dyno hours go into a cam design. the 3.9 cam is the same as a 3.5 cam but advanced 5degrees to give better torque.

You would have to know quite a bit about cam duration and timing to be able to select the right cam, and I did a lot of research when I changed my worn cams, only to find that the Australian cams offered were "high torque " only in the context of Versus "High rev " lumpy as fitted to say a MGB V8 or Rover SD1.

The problem becomes and has been documented here is that without a stock type cam, there is no torque for hill climbing and you are forever changing down in a heavy vehicle like a RRC or 38A.

If you persist with an aftermarket cam, I suggest that you go to someone like Piper in the UK, as all the OZ ones I looked at had more overlap hence lower "torque" potential than the stock cam.

Remember that as a rule aftermarket cams have little research and dyno time but the maker selects from a set of "stock" grinds ie 23:60 60:23
Regards PhilipA

[JaapRoskam]

Hi Philip , that sounds very sensible to me - 'camshaft sense' .
I was leaning towards the same thought:
"A big engine manufacturer would not waste money on its multi million dollar engine design only to put in a poor performing camshaft."
Ofcourse they have to accommodate the common user in the common country with a common choice of petrol on common type of roads - but only extreme use like racing or hefty 4WD etc. might warrant an extreme camshaft.
So I think I safe myself the trouble of finding a holy grail stick and go for a nice OEM camshaft from Graeme Cooper - they have supplied me over the years with only quality parts. That way the car will not get confused either ;-)

Thanks again !!

J.



Over the years on this forum many people have changed camshafts and there have been numerous discussions.
Even what are advertised as "high torque" camshafts are often more radical than a stock cam.

Remember that many dyno hours go into a cam design. the 3.9 cam is the same as a 3.5 cam but advanced 5degrees to give better torque.

You would have to know quite a bit about cam duration and timing to be able to select the right cam, and I did a lot of research when I changed my worn cams, only to find that the Australian cams offered were "high torque " only in the context of Versus "High rev " lumpy as fitted to say a MGB V8 or Rover SD1.

The problem becomes and has been documented here is that without a stock type cam, there is no torque for hill climbing and you are forever changing down in a heavy vehicle like a RRC or 38A.

If you persist with an aftermarket cam, I suggest that you go to someone like Piper in the UK, as all the OZ ones I looked at had more overlap hence lower "torque" potential than the stock cam.

Remember that as a rule aftermarket cams have little research and dyno time but the maker selects from a set of "stock" grinds ie 23:60 60:23
Regards PhilipA

[prelude]

I have a piper 285 cam, a tornado chip and a stage 3 tune from RPI (ie, ported and polished etc.) and I can tell you that it has quite a bit of grunt but at higher RPM. It's funny to pull away from those new fangled eco boxes at lights in a big cloud of unburned fuel, though I am getting to old for this according to the missus. Bugger. Anyway I reckon that this cam was worth it since we all know (and have experienced) that a heavy P38 (towing or just laden) with the 4-speed ZF wants to shift down... A LOT. Since in third gear at speed you go up in RPM's "significantly" you are slap bang in the power band. I may have overdone it with my setup because in third it pulls that damn well you have to lift a bit and the auto wants to go back to 4th, you end up giving it some more, it shifts back down to third etc. :) So I work the gear lever a lot in mountainous terrain. What I am trying to say is: more low end torque IS nice but the auto box prevents you from properly using it imho except when pulling away.

Anyway, the only real downside is that my rangie now sounds more like an american muscle car than a P38, the V8 runs a lot less smooth and because of the cam overlap I think? I have trouble getting my car MOT passed (emissions) when idle. I trick the system since I can have a high idle as long as it stays below 1000rpm according to local law so I pull the tensioner a bit to get 'er up to 900rpm and she passes no problem.

Would I do this again? not sure. My fuel consumption has gone up but then again, I have done so much to the car at one go that it is hard to say whether that was the engine work or all the weight / bigger wheels. In any case, I wonder if there is a lockup kit for the ZF box, I know wholesale automatics sell (or sold) a compushift kit from ashcroft but I am not sure if that is enough... I digress...

Good to see you fixing her up though! My heart still lies with these old beauty's

Cheers,
-P

[PhilipA]

Just to amplify my comments, you would be much better spending money on a Thor manifold which has about 1 metre between the ports and throttle body and has tuned length runners to increse torque at say 2000RPM , which is where you need it. You lose 10% over 3000 or so.
I ended up with 50% more torque at 2000RPM for a loss of 10% over 3000rpm which is very much worth it.
I syill have the comparative dyno sheet .
178384


Regards PhilipA

[JaapRoskam]

What you describe is pretty close to what a RR specialist told me.
He has serviced LR & RR for well over 35 years and said this:
"Range Rover users can be divided in two groups: new and used buyers. Very few new buyers will ever experience a worn camshaft - just the car performs a tad less after a few years and they trade for a new one. Then a used buyer drives if for a while , decides he needs a new CamShaft .... they go more often as not for a magic one and the vehicle performance jumps up from sluggish to 'like new' ... he thinks. And the used buyer is very happy - after all they never experienced the V8 performing like new and think the magic CamShaft is the actual miracle.
But in our 35++ years of experience we learned the hard way that sticking to only OEM parts is still the best and on the long run the most affordable way to go: no short lived after market parts , no expensive magic parts , not money wasting magic re-chipping etc. Just stick to a meticulous maintenance schedule and keep on driving until all plastic bits of your P38 are al over Australia mate !!"

[JaapRoskam]

That sounds like a cool project : GEMS with bananas.
How complicated is it to do I wonder ?
How did you go with the TPS and other sensors ?
How did the ECU work it out - did it require re-chipping ?


Just to amplify my comments, you would be much better spending money on a Thor manifold which has about 1 metre between the ports and throttle body and has tuned length runners to increse torque at say 2000RPM , which is where you need it. You lose 10% over 3000 or so.
I ended up with 50% more torque at 2000RPM for a loss of 10% over 3000rpm which is very much worth it.
I syill have the comparative dyno sheet .
178384


Regards PhilipA

[PhilipA]

How did you go with the TPS and other sensors ?
How did the ECU work it out - did it require re-chipping ?

I used the 14CUX TPS as a TPS is only a varaible resistor from 0-5V. Only because the TPS that came with the Thor didn't seem to work.
I had a Unichip which provided the advance curve and any fuelling differences.
I also added O2 sensors which handled the mixture at part throttle.
The Gems should be easier to do as it has 02 sensors .
The hardest part was arranging a kickdown cable as the old 4HP22 was kickdown controlled, whereas a Gems is electronic.
You have to reroute the the plumbing on the stepper motor but that is just hardware.
I had to modify the fuel rail a little but AFAIR it was just a matter of redrilling the holes. You have to use an early 3.9 fuel rail with the FPR on the RH back as the later ones do not fit with the Thor manifold.
Regards PhilipA