D22 Petrol Power performance prob

[gonguana]

Hi guys,
I have a Nissan Navara 9/2005 petrol/gas. When I purchased this truck a few years ago the gas was already fitted. On the compliance plate it stats 2006 for the fit.

The question I was hoping to put forward is maybe 2 fold. Firstly when I am in 5th gear and doing 110 kmh on the freeway it is fine until I start to hit a bit of a hill. Then I can watch the speedo drop down to about 90 – 80 kmh. The foot is flat to the floor and it sounds like the throttle is fully open as i can hear a brrrrrrr sound if it trying to suck air in. Also I might point out that this is when the truck is empty and running on premium fuel. Gas is worse obviously. This unit is naturally aspirated.

I am traveling 130km and using over one quarter of a tank of fuel. Am i just trying to expect to much from the truck. If i drop back to fourth gear and plant my foot the truck picks up speed very slowly and will evntually make it back to the 110kmh speed but be doing over 3,500 rpm.

Q,So, Could the lack of power be simply due to valve wear and I need to get the head serviced and valves ground?
Q, If the above is true, Could the gas conversion have caused this? It’s got 130,000 on te clock.

Also would I be better getting rid of the gas conversion and having the truck re-tuned?

Thanks in advance guys for all your suggestions.

 

[Old.Tony]

Welcome to the forum.

If I'm right, you're using around the 14-15LPHK which is quite respectable for a petrol ute of this size. The D40 from 2008/2009 (petrol) uses 15-17LPHK so you're not doing badly at all. The diesels are markedly better - 10-12LPHK for the same kind of trip (unloaded highway).

Travelling at 110km/h will make it use more fuel. I don't know where the peak torque is reached by your engine, but that's the point where you want the RPM to be, regardless of what speed you're doing (it might be similar to our diesels, around the 95km/h mark). If you tried driving at THAT speed (yes, people will overtake you) and see how your fuel consumption goes you might find it lowering more.

It's very difficult to gauge whether or not the "bit of a hill" is steep enough to do that to most of our vehicles. I've had my D40 go up "a bit of a hill" at 125km/h with a 1.8T van behind it and it just cruised straight up and over. I think it's better for someone with a similar vehicle (but in say a diesel) do the same hill and see how the thing behaves.

You will find that variations in fuel quality, spark plug condition, HT lead condition, points condition etc all play a role in performance. The amount of gunk in the intake manifold could be astounding by now - you might find some improvement by using some injector cleaner, but also inspecting the inner part of the manifold paying particular attention to where the crankcase ventilation enters.

I don't know that I'd immediately pull the heads apart and start popping valves. I'd look at the manifold and other bits and pieces first and then try the harder stuff later. If you're not seeing bubbles in your radiator and no sign of milkiness in your engine oil, your head gasket is probably ok. If you're not blowing blue smoke your valve guides are probably good. If you do a compression test of the engine you can check the condition of the valve seats.

 

[180degrees]

Its probably just the VG33e being to underpowered for that type of car *shrugs*

I had one in an old auto pathfinder and it was shit (the lack of power, the car was alright offroad I guess), so glad to get rid of that thing though.

 

[gonguana]

Hi Guys,
Thank you all so much for the fast responses.
Old.Tony that is an awesome reply. The bit of a hill I was imagining was about a 10% grade over a long distance “I’m Talking about the F3 now I see your in Newcastle, Ourimba Hill and the same up Mt White”. Guys are flying past me and I just seemed to get bogged down with a power loss. Look, all lower gears are good and I don’t need to try, to hit 4000 revs easily in those gears. Very snappy in 1st and second. I think I’ll take your guys advise and get a compression test and the truck tuned. Old.Tony, am I right to be thinking that “HT lead condition” is Spark plug leads. I am not a mechanic so I suppose I need to ask. Is there anything that can be done to this type of setup to give not so much any more speed but pulling power to hold the speed if I was carrying a few 100kg?

I don’t think this problem is getting any worse but in saying that I think in Australia we have a dramatic variance in the quality of fuel that is claimed to be either “unleaded or premium” I do notice a difference with premium from different vendors and I do notice a difference in putting premium or unleaded in the truck. What would you guys suggest?

Also just to cap off.
“If you're not seeing bubbles in your radiator and no sign of milkiness in your engine oil, your head gasket is probably ok”. No milk, no colored smoke, no blue smoke, Although if I run on gas for say a local trip 60kmph and then start the truck the again maybe an hour later I sometimes get a puff of white smoke out the exhaust. This is only on gas and only when it fist starts. Is this a problem?

Thanks lads I really appreciate all your suggestions.

 

[Old.Tony]

I don't think the puff of white smoke after using gas would be a problem.

So, we're talking the Mooney Mooney bridge climb ... I wouldn't sweat about that. Even near new, my Navara wouldn't take that or the Ourimbah hills in top gear without slowing down significantly.

HT leads are spark plug (High Tension) leads.

Pulling power - torque - comes from a combination of things.

1) Fuel. Diesel does it better but petrol still has it. Turbochargers do help.

2) Engine capacity. The more cubes, the more pubes. Ask Krankin, he'll confirm that.

3) Gear selection. The whole reason why 4WDs have a 4LO is not so that we can go slowly, it's so that we have so much torque we can out-pull a whole classroom full of schoolboys.

So, I don't think you actually have a problem. This isn't a V8 supercar and sure as eggs mine doesn't have a Ferrari logo anywhere. Mine - although appreciably heavier than yours at about 2500Kg empty - does the exact same thing.

Just go out and enjoy it!

 

[Dave]

The VG series with the SOHC heads dont breath to well standard.

You could always to the exhaust to open her up.

 

[gonguana]

Thanks Guys

Thanks Guys for your replies.

I have booked in for a service and tune of the Gas system.
We will see if there is any improvement. I'll post back any findings.

 

[scottybobcat]

The v6 wouldn't pull the skin off a rice pudding. If you want to spend some money on it do the exhaust, put a torqueier cam in it and supercharge it.