Does 98 Octane petrol improve performance of 4.2 petrol GQ

[LandRoverGhost]

I , I come from a V8 Range Rover 4.6 L engine. Now own a beautiful Nissan patrol GQ with the 4.2 Petrol. In my Rangy running 98 Octane Petrol ( V-power , Ultimate, etc. etc. ) made a definite difference in performance. Has anyone similar experiences with the 4.2 L. ... or not ;-) ??

[billyj]

will make stuff all difference unless you advance the timing to get the most out of it.

[LandRoverGhost]

That makes sense !!! So use to that Computer Controlled Rangie - I totally forgot about timing advance etc. - have to learn it all over again ;-)

[garett]

my old laser went from 300km a tank on e10 to 500 km a tank on 98 with a msd 6al, coil, and timing and carby tune. it also hauled a$$. traction became the biggest problem

[MudRunnerTD]

Yeah my old XR6 ute loved the 98. After a tank or so it would return 50 to 100kms better per tank with better performance the whole time.

[LandRoverGhost]

Thanks - so 'just' using 98 is not enough - so much is clear - tuning it to 98 is the only way !

[FNQGU]

makes some things run hotter too. No idea about a big old Nissan 4.2 though.

[Arfa Brayne]

This one is an old furfy.
I also do a bit on a lawn contractors forum, and there is the anecdotal theory that 98 premium will make the mowers go harder too. (rubbish)
The only reason to have a high octane fuel is to cope with higher compression ratios.
If you have a compression ratio of 10:1 or higher, igniting the fuel the same BTDC as a 8:1 engine will burn the fuel faster and increase cylinder pressure enough to make the charge detonate (pinging). TO avoid pinging the timing has to be retarded in high compression engines that are trying to run standard unleaded fuel.
If you have a compression ratio of 8.5:1 (tb42), running 98 premium means the fuel will burn slower - effectively retarding the timing and making the engine run hotter with less efficiency. Modern engines that set ignition timing based on knock sensors will run almost identical to running the engine on 91 unleaded. However the ignition timing will spark further before TDC which can rob an engine of power.

If you really want to test the theory, run your engine on LPG - it has an octane equivalent of 110. = Runs hot with less power.
Increase the compression to around 11:1 and run LPG = better fuel economy, more power and cooler running.
Run 11:1 compression with wet injection LPG and you'll get better power and fuel consumption than the same engine fuelled with petrol.

May as well try feed a bulldog rib eye fillet steak to make it run like a greyhound.

[LandRoverGhost]

This one is an old furfy.
I also do a bit on a lawn contractors forum, and there is the anecdotal theory that 98 premium will make the mowers go harder too. (rubbish)
The only reason to have a high octane fuel is to cope with higher compression ratios.
If you have a compression ratio of 10:1 or higher, igniting the fuel the same BTDC as a 8:1 engine will burn the fuel faster and increase cylinder pressure enough to make the charge detonate (pinging). TO avoid pinging the timing has to be retarded in high compression engines that are trying to run standard unleaded fuel.
If you have a compression ratio of 8.5:1 (tb42), running 98 premium means the fuel will burn slower - effectively retarding the timing and making the engine run hotter with less efficiency. Modern engines that set ignition timing based on knock sensors will run almost identical to running the engine on 91 unleaded. However the ignition timing will spark further before TDC which can rob an engine of power.

If you really want to test the theory, run your engine on LPG - it has an octane equivalent of 110. = Runs hot with less power.
Increase the compression to around 11:1 and run LPG = better fuel economy, more power and cooler running.
Run 11:1 compression with wet injection LPG and you'll get better power and fuel consumption than the same engine fuelled with petrol.

May as well try feed a bulldog rib eye fillet steak to make it run like a greyhound.

Tanks for the detailed and very sensible reply. I did actually increase the compression ratio on my old Range Rover P38 - hence better running on 98. But sort of suspected what you explain so well for my TB42 , it runs already extremely well on LPG though. Not sure if previous owner worked on compression.

[Bigcol]

if yours is a TB42 with Gas conversion LandRoverGhost

some of what Arfa has said is possible

just remember, your petrol will normally be set at about 8*BTDC - and if your Gas has been set up correctly, you should be closer to 16*BTDC

it will depend on who tuned it, and how they tuned it
for Petrol / Gas economy (so you use both fuels)
for Petrol (because they dont know how to tune a car with Gas - and they ARE out there)
for Gas Economy
for Gas Power
for Gas Performance

if it has been setup for Gas - using 98 petrol will be a waste of time & money


sounds like the previous owner has it set for Gas Power

[Bigcol]

Arfa,
only small concern I have with your post

run your engine on LPG - it has an octane equivalent of 110. = Runs hot with less power.

mine NEVER overheated on Gas - because it was tuned for Gas Performance
TB42 petrol - 93Kw
TB42 Gas Performance - 96Kw

was a far far better machine on Gas than on Petrol I can assure you

[Arfa Brayne]

Yeah Bigcol ......Seems like a lot of the Patrols run better on gas than petrol. The 2 I've owned seem to run smoother. The previous TB42 had way less power on gas, but the new TB42E with impco gas seems to go great - don't know what it runs like on petrol yet, the pump is on my bench at the moment, it would idle sweet but just backfire and cough if you tried to drive it on petrol.
I wasn't saying the Troll would overheat if you ran it on gas - just that engines running gas generally run hotter than running petrol.

[dom14]

my old laser went from 300km a tank on e10 to 500 km a tank on 98 with a msd 6al, coil, and timing and carby tune. it also hauled a$$. traction became the biggest problem

That's a 66% improvement in fuel efficiency, and not to mention the significant power increase.
I remember you advising me on MSD 6AL ignition unit.
It's "dual curve" unit?!

http://www.ebay.com.au/itm/MSD-6AL-IGNITION-CONTROL-MSD6425-/252400690745?_trksid=p2141725.m3641.l6368

[Bigcol]

Yeah Bigcol ......Seems like a lot of the Patrols run better on gas than petrol. The 2 I've owned seem to run smoother. The previous TB42 had way less power on gas, but the new TB42E with impco gas seems to go great - don't know what it runs like on petrol yet, the pump is on my bench at the moment, it would idle sweet but just backfire and cough if you tried to drive it on petrol.
I wasn't saying the Troll would overheat if you ran it on gas - just that engines running gas generally run hotter than running petrol.

I turfed the standard fuel pump and put in an electric one
as soon as you flicked from Gas to petrol, the pump started to pump

mine was a 1989TB42 carby
I had a Sprint Gas mixer on the top of the carby
electronic ignition
extended rotor
silicone plug leads
and lots of other goodies
was tuned for Gas performance, as it would only go into Petrol once a week

but I could switch from Gas to Petrol or Petrol to Gas on the move - alot of people seem to have trouble switching from one fuel to another

[Bigcol]

I wasn't saying the Troll would overheat if you ran it on gas - just that engines running gas generally run hotter than running petrol.

again, on the contrary, it used to run about 8* less on Gas than Petrol

usually sat on about 85* on long runs in Gas
and about 92-95* on petrol

but as I said, it all depends on how its tuned, and who tunes them

[Arfa Brayne]

That surprises me Col- very interesting.
My first Troll was an 89 Auto TB42 , I don't remember what gas system was fitted but it had a venturi on top of the carby fed by twin vapor hoses. Also ran an electric shuttle pump when the original mechanical pump went- maninly because Nissan wanted over $300 for a new one and a Faucet pump was only $40
Fitted HEI ignition , extended rotor, 4x prong plugs to deal with problems of engine "kicking" sporadically, ended up being resistance/dry joint in the main power feed wire near the fusible link beside the battery.
Also made up an overide to use the auto box like a manual with a H pattern shifter and TC lockup. Went really well, but had considerably more power on petrol no matter how it was tuned. I think the lack of power came form tha gas converter not being big enough capacity for the 4.2 , but really only ever used the petrol as a backup for when the gas tank went dry.

[Bigcol]

just found this - sorry Arfa



That surprises me Col- very interesting.
My first Troll was an 89 Auto TB42 , I don't remember what gas system was fitted but it had a venturi on top of the carby fed by twin vapor hoses. Also ran an electric shuttle pump when the original mechanical pump went- maninly because Nissan wanted over $300 for a new one and a Faucet pump was only $40


sounds like the old "ring" for the gas - sat on top of the carby, under the air filter -
similar to this
68764

the Sprint Gas type looks like this
68763


I think the lack of power came form tha gas converter not being big enough capacity for the 4.2

interesting that you say that
I had an MQ/MK with the L28 6cylinder motor - it was constantly starving for Gas under loads, until I put in a bigger convertor
and when I brought my GQ - I told my Mech to up-grade the convertor - as a TB42 is a B I G engine (compared to the Ford 4.0L & Commodore 3.8) - which he did, and I never had any more problems with it
I also think the mixer on the Carby has a lot to do with how well they run

some of the problems I encounted with trying to get the Gas tuned can only be answered by the fact the Mechanic did not know as much as he thought

went to one "Gas Specialist" to get a tune up, (no petrol in the car at all) come back later - the Bill has $10 for petrol on it - what for....? so we could tune it............ ummmm your a Gas Mech - its a Gas car I want it tuned for Gas - oh, but most people dont notice...... well I did, and as far as I am concerned I am not paying ANY of the bill, as you did nothing that I wanted done

went to another "Gas Specialist", parked it under his sign out the front
come back 4 hours later -
Cars ready - no its not, its not been moved, - yes it has, - no it has not, - yes it has - why do you say nothing has been done - well, I do have the keys in my pocket - because I forgot to leave them, and its still locked and parked where I left it.........

[Arfa Brayne]

Hmmm - "Gas Specialist"....... yeah, Col

"A self proclaimed Expert is someone who hasn't learnt enough to realize how little they know"

Or as my dear Mum always says " X is an unknown quantity, and SPURT is a drip under pressure"

[threedogs]

Bigcol I ran that new generator mixer on my 650 4 barrel powered chev troopy
Trouble was it only feed gas to the back two barrels , we farted around with and
ended up getting fuel to all 4 barrels, Blew away most 4x4s and was a sheep in
wolfs clothing, I also found having the open air filter a pain in the butt with water
crossing and dust. I have my mates at the airport make a sheild for the front to
protect the air filter from muck, worked a treat.In the end I brought an early Holden
air filter

[graderman0]

Bigcol I ran that new generator mixer on my 650 4 barrel powered chev troopy
Trouble was it only feed gas to the back two barrels , we farted around with and
ended up getting fuel to all 4 barrels, Blew away most 4x4s and was a sheep in
wolfs clothing, I also found having the open air filter a pain in the butt with water
crossing and dust. I have my mates at the airport make a sheild for the front to
protect the air filter from muck, worked a treat.In the end I brought an early Holden
air filter

I have just got a 4.2 gq and went to cape york.was pulling a trailer and was using 3 kls per litre.Are they usualy this thirsty?

[Clunk]

I have just got a 4.2 gq and went to cape york.was pulling a trailer and was using 3 kls per litre.Are they usualy this thirsty?
One word....... yep

[Bigcol]

I have just got a 4.2 gq and went to cape york.was pulling a trailer and was using 3 kls per litre.Are they usualy this thirsty?


X2 what Clunky said...........
sounds like something is not quite right - just guessing mind you

[Bigcol]

Bigcol I ran that new generator mixer on my 650 4 barrel powered chev troopy
Trouble was it only feed gas to the back two barrels , we farted around with and
ended up getting fuel to all 4 barrels, Blew away most 4x4s and was a sheep in
wolfs clothing, I also found having the open air filter a pain in the butt with water
crossing and dust. I have my mates at the airport make a sheild for the front to
protect the air filter from muck, worked a treat.In the end I brought an early Holden
air filter

yeah that pee'd me off as well.......... with the air filter......... no way of making it water proof or dust proof without stuffing it power advantages

[kevin07]

yeh I ran mine on 14 to 15 advance ran perfect fix up a bit of chain stretch as well