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Discussion Starter · #1 ·
I recently changed my dead 2003 zd30 over to td42t and reused my 3.0L gear box.

My revs were 3000 at 100km/h, I also have a gu ute 2002 with the same motor and it only does about 2250 rpm at 100. So I swapped my diff ratios from 4.3 to 3.9 and dropped my revs to about 2500rpm at 100, this is with 33"s on as well.

Today I had turbo hi flowed by a reputable mob in Toowoomba and they said they couldn't get boost to come on as much as it usually did "might be the timing ".

Is it possible that the timing could lead to the boost not coming on soon or strong enough?
It doesn't get to 10psi until about 3000rpm and is only about 5 or 6 psi between 2200 to 2700 revs, they said they normally get around 11 to 12 psi after hi flowing turbo.

Just wanted to see what someone with more experience thought before taking it to have timing checked(again as only a month ago I had it checked as it was running rough).
Cheers
 

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Master Coalroller
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When your timing is closer to TDC or near standard, the heat produced by the igniting fuel will exit the exhaust valve at a higher temp to give an earlier RPM boost and higher overall EGT. However this is at the expense of higher RPM flow and power, as you can only burn a certain amount of fuel within this time.
When your timing is more advanced you can enrich the fuel pump as there is more ignition time to burn it, and at higher RPM this gives more power. But this is at the expense of satisfactory EGT at the lower RPM, causing lower power and boost at lower RPM.
Cheers
 

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Master Coalroller
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Personally I would be looking at:
Fuel delivery, are you seeing at least some black smoke in the daytime? Does it need to be richer? You need to see some black smoke for evidence of an adequate fuel load to heat the turbo. EGTs need to be above 300C for good power.
Timing, are you getting high RPM power? I'd there grey smoke in the lower revs? Grey smoke is unburnt diesel and wasted fuel. Timing too advanced.
Inlet manifold, do you have a standard inlet manifold, as these do suffer lower than required flow.
I had a BJ73 with a 3B that I turboed, but it had such a tiny inlet manifold that held enough flow for one cylinder. The boost gauge would flutter like mad. It wouldn't provide low end boost until I put a home made hiclone in it. The hiclone provided the extra flow and the boost gauge stabilised.
Goodluck
 

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Discussion Starter · #4 · (Edited)
Thanks for your replies, I can get a bit I power in higher revs (especially in lower gears). The guys doing the high flow had it on dyno and checked fuel delivery and it is ok. EGT's get up to 400 degrees up the hills, it just seems that the boost comes on too late. I have a gu ute with same motor and has it hi flowed and goes a treat.
Maybe it is the timing, there doesn't seem to be much if any smoke at all. The guys had black smoke coming out and backed the fuel off.
I just wanted a few ideas to see if the timing maybe the issue before I pay someone to look at it.
Cheers
Ps it is just standard manifold.
 

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Discussion Starter · #6 ·
I had an auto electrical place do the job and he converted tacho, it says i am idling at about 750 revs and doesn't rev much past 4000 so it seems right.

I also wondered if I geared down too much (3.9) but it still revs 2500 rpm at 100 which is more than my standard 4.2 ute.
Even if it was too taller gears the turbo should still be coming onto to power earlier than about 2900 ?

These injector pumps are vacuum controlled is this right? Is it possible something might be affecting vacuum and then pump not delivering enough fuel in higher revs maybe?
 

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Master Coalroller
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4000? Are you sure you don't have an RD28 hehe.
You should idle at 600-650 and I'm sure you don't go much past 3500, well I don't when I'm driving the cheeky lil sisters Mav.
I think you may be onto something here bobby4wd.
 

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Master Coalroller
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Td42s red line at 4600.

Sent from AutoGuide.com Free App
Ahh well he may be in the right place with his RPM.
Would you go and work that high often though if turboed? I've only driven NA 4.2 and can't remember where the redline is, but only gone to 3600.
My V8 is max 3600 but I don't go past 3200, and that's a short stroke engine too.
 

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Discussion Starter · #10 ·
My rpm figures were just from memory I will check for sure once I am home. I never really go past three thousand because there is no point really. Even at three it is screaming I am just using it as an example as in 5th gear that is when the boost properly starts which is much too late .
 

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Discussion Starter · #11 ·
I forgot to mention that the motor I put in was rebuilt, the fuel system injectors and pump were all removed, cleaned and checked. Is it possible that when the motor was reassembled that they may have stuffed up the cam timing??? Would this be able to cause this problem.
 

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Master Coalroller
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Boost starting at 3000 is too late, there won't be a cam timing issue as you would have different symptoms.
Maybe you should book a compression test to validate your rebuilt engine performance and then look at EGTs as this heat production is what drives a turbo.
EGT and pump timing is the key. If you lack heat you won't produce boost.
 

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Discussion Starter · #14 ·
A compression test would be worth it, my EGT's are getting up to mid 450 degrees up a hill.
 

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Master Coalroller
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Mine isn't a 4.2 but if the EGT drops below 200C when wheeling around the burbs, there's no boost down low. I returned my timing back to near standard and now even when I'm driving softly I can just keep 200C.
Cruising highway 6 PSI 300C at 1780 RPM at 100kmh in 5th.
 

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Well, first question, was it boosting fine before the turbo work?
If yes, then that kind of nails it down. Did I read right they had it on the dyno and pulled fuel out because it was smokey? Was it making boost before they pulled the fuel out?
Sounds to me to be a bit of a boost control, or wastegate issue that has just been fobbed off as someone else's concern.
 

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I have a 2003 td42t. When it had the stock HT18 turbo (with bleed valve on waste gate signal hose) it made 10 psi by about 2200 rpm. What smoke are you seeing ,and when?

Your boost is far later than standard.

As BAMBILL asked "was it this bad before they "HI FLOWED" it?
 

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Discussion Starter · #18 · (Edited)
Thanks for your replies, it was running very sluggish before "they" got to it with similar amount of boost. There was no smoke before or after dyno tune, I merely asked if there was a fuel supply issue and the fella said there was plenty of fuel available as he had smoke coming out then backed it off.

Before "hi flowing" turbo I had about 65rwkw and now have 105rwkw, it just doesn't get the power and boost till higher revs. I have had the same thing done on my ute with exactly the same motor and it pushes 116rwkw but just does it at way lower revs.

In lower gears it's ok as you change fairly quick and get to higher revs quicker it's just in 4th a little bit and fifth you notice it the most, don't know if that make sense. The guys doing it have done a few of my mates cars and are really good as far as I know and it's all they do is turbos nothing else.
 
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