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NISSAN PATROL Y61 3.0 Di (ZD30) 09/2000
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Hi Guys, you know how I like graphs.
This is a typical example of a PATROL which is running high Psi and getting LITTLE AIRFLOW ( vanes closed far too long )
So you can run high boost but still get little airflow.

This Patrol is auto, and I am helping his owner getting power back.
AIRFLOW and reduced EMP is all what matters.

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This is typical of a turbo (and a Patrol) which is (are) totally mi-used.
MAF vs RPM dot plot in red is self-explanatory, so is MAP (psi) vs MAF. What a disaster :
Lots of boost ( and far too much for a stock turbo by the way) and ridiculous airflow ( = HIGH EMP !!).

His Patrol is more recent than mine, so Nissan data scan provides boost vs time in Psi, hence an easy task to graph all this out. MAF and MAP data are 'raw data', not integrated like what I do with my acquisition system, hence the variance of data, a bit noisy down low when idle ( between 1.5V and 2.2V).
 

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NISSAN PATROL Y61 3.0 Di (ZD30) 09/2000
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That guy called me as he was getting big 'turbo surges' when changing gear or releasing the throttle, as explained by @OldMav. He now knows why, and what to do.
 

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NISSAN PATROL Y61 3.0 Di (ZD30) 09/2000
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This is my own real-time MAP (in bar - sorry ) vs MAF sensor voltage (in volts) for my stock turbo (RPM color coded blue 750RPM red 3500 RPM) . and the optimum vanes opening curve for my own patrol configuration ( 3" stainless steel exhaust - wider IC - no EGR ). Standard inlet - no remap. My MAF is electronically controlled to avoid limp modes. Max boost 18 psi.

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That guy called me as he was getting big 'turbo surges' when changing gear or releasing the throttle, as explained by @OldMav. He now knows why, and what to do.
You say he's running to much boost but it only appears to be a bit over 14 psi? Correct?
Those graphs , are they 1st gear thru to 4th? Could you do a graph for 3rd gear only from say 1200 rpm to 4000 rpm so others could have a base line to compare to.
Enjoy your posts, keep it up.
 

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I don/t have enough eyes to watch everything at once so i'm not sure if peak boost or peak rpm , not during spool thou.
Jeez mate, you must hit full boost really late if you're unsure if it's peak boost or max RPM at the time of reading. Most guys normally have at least 1500-2000rpm difference between the two and if your doing fourth gear pulls to get your readings that's normally enough time to glance down at peak boost then again at max RPM. If your doing it in lower gears though it can all happen really fast and hard to get accurate readings.
 

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NISSAN PATROL Y61 3.0 Di (ZD30) 09/2000
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You say he's running to much boost but it only appears to be a bit over 14 psi? Correct?
Those graphs , are they 1st gear thru to 4th? Could you do a graph for 3rd gear only from say 1200 rpm to 4000 rpm so others could have a base line to compare to.
Enjoy your posts, keep it up.
You are bloody right. I did a terrible mistake when analysing his data, since NDSI provides absolute boost,and not relative. He is low in boost. MY APOLOGIES TO ALL.
In fact, the guy was running a non-Nissan MAF on his stock inlet, so it is impossible to compare. What is certain though, is that, if his non-Nissan MAF Voltage is lower that what a Nissan MAF would deliver, he gets less diesel injected and lss power. All the opposite.

My colored graph provides gear 1 to 4th on a manual T. upper points are under load.
 

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Jeez mate, you must hit full boost really late if you're unsure if it's peak boost or max RPM at the time of reading. Most guys normally have at least 1500-2000rpm difference between the two and if your doing fourth gear pulls to get your readings that's normally enough time to glance down at peak boost then again at max RPM. If your doing it in lower gears though it can all happen really fast and hard to get accurate readings.
I do most of my pulls in 3rd.
The emp gauge was lying in the passenger side foot well next to my ecutalk display and AFR gauge, my boost gauge is near my left knee and my EGT gauge is at the top of my instrument cluster. I like to look where i'm driving also. The video i took of the emp gauge and ecutalk didn't work out so i'll try get a better one.
0-100 is about 12 secs so it's not slow to boost.
 

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NISSAN PATROL Y61 3.0 Di (ZD30) 09/2000
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The difficulty with IMP and EMP gauges, is that not only they give an 'average' over time (usually a few hundred ms), but for the four cylinders.
In fact, when you acquire MAF fast enough (ECU TALK under-samples and get one sample every xxx ms), you can even see the strokes ! Same happens with MAP. you get an 'average'. When you 'average' 200 or 300ms, the peak is always lower than reality. I do integrate 50ms for my data acquisition (but I get one sample every ms).
I'll acquire new data in 3rd from 1200 to 3500 RPM on my Patrol when I have time.

@Kiwi_dingo, getting the peak boost a bit later is not an issue if you have managed to maximize your airflow at a lower Revs with less boost by opening the vanes sooner.
 

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I do most of my pulls in 3rd.
The emp gauge was lying in the passenger side foot well next to my ecutalk display and AFR gauge, my boost gauge is near my left knee and my EGT gauge is at the top of my instrument cluster. I like to look where i'm driving also. The video i took of the emp gauge and ecutalk didn't work out so i'll try get a better one.
0-100 is about 12 secs so it's not slow to boost.
Yeah that explains the difficulty then, that would be so hard to read it all by yourself while still focusing on the road. I often do fifth gear pulls when doing back to back testing just to get it all to slow done a bit to give me more time to take note of all the gauges.
 

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@Kiwi_dingo, getting the peak boost a bit later is not an issue if you have managed to maximize your airflow at a lower Revs with less boost by opening the vanes sooner.
Yes I know mate, I was only referring to the comment about not knowing if it was at peak boost or peak RPM. I've never had an issue in not noticing when I'm at peak RPM as I don't go any faster no matter how hard my foots pushing on the pedal :LOL:
 

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Hi @Navowner ,
here below is a graph from data I had in 3rd gear. However, probably 1/2 throttle, and not a fully flat road. Not easy to find where I live. But it will give you a first idea.
I added some RPM data on the excel graph. MAP in mbar or bar relative ( left scale MAP in mbar absolute - MAF in mVolts ). I will have to find a place to record a specific run to provide you with 1200 - 3500 in 3rd.

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You can only compare this date with a Nissan original MAF, plugged into its stock housing.
Any variation in diameter at that level will alter the MAF value, making the comparison impossible.
0-100km/h GPS in 12s is quite good compared to the 15s of the stock Patrol.
 

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and this is the same curve superimposed on my own 'turbo MAP'. Extrapolation is quite easy on both sides.

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How'd you go with all this @geeyoutoo, did you carry out more testing with that gauge you were hooking up? Curious to see your readings. I've just done all this testing again with another new turbo I put on my car and I'm still finding it very interesting in regards to what effect EMP has on spool and power/torque dropping off in higher rpm. I wanted to try it with another tubo as well but I don't think me using "I wanted to recorded my EMP:IMP" as a good reason for being out and about on the roads right now :LOL:
 

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GUII ZD30DI Wgn
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How'd you go with all this @geeyoutoo, did you carry out more testing with that gauge you were hooking up? Curious to see your readings. I've just done all this testing again with another new turbo I put on my car and I'm still finding it very interesting in regards to what effect EMP has on spool and power/torque dropping off in higher rpm. I wanted to try it with another tubo as well but I don't think me using "I wanted to recorded my EMP:IMP" as a good reason for being out and about on the roads right now :LOL:
I bought a new Glycerin filled gauge and have enough silicone hose to bring it up through the bonnet scoop and into the cabin, so I will be doing some further testing shortly.
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I bought a new Glycerin filled gauge and have enough silicone hose to bring it up through the bonnet scoop and into the cabin, so I will be doing some further testing shortly.
View attachment 517854
Have you had a chance to do much testing with this setup yet? I drove off with my gauge and fittings sitting on the bulbar the other week after switching it out to measure EGT and consequently they weren't still there once I had remembered and pulled over to check 🤦‍♂️
 

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Have you had a chance to do much testing with this setup yet? I drove off with my gauge and fittings sitting on the bulbar the other week after switching it out to measure EGT and consequently they weren't still there once I had remembered and pulled over to check 🤦‍♂️
Wow, sad, did that a few weeks ago with a spanner!!!!!!!!!!!!!!!!!!! No haven't gotten around to it yet, had a lot going on.
 

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EMP.
What is it?
Exhaust Manifold Pressure.
Why is it important?
It becomes relevant when we measure it against inlet manifold pressure. IMP : EMP ratio.
IE- the psi in the exhaust manifold to the psi in the inlet manifold.
Ideally we want a lower pressure in the exhaust manifold compared to the inlet manifold.
But why?
A couple of reasons.
1st, heat build up.
2nd, cylinder fill.
I'll concentrate on the td42 with a gated turbo, but the theory is relevant across all turbo charged engines.
If you have more psi in the exhaust than the inlet manifold, you have a situation coined by Banks called 'choke'. It's where the exhaust heat builds in the exhaust manifold and is held there because of a restriction.
This has a negative effect on the cooling system around the exhaust ports
2nd Cylinder fill.
Another phrase coined by Banks 'poor man's EGR'.
What does this mean?
Simply, if you have more psi in the exhaust manifold than the inlet manifold you are unable to remove the entirety of the exhaust gases from the previous combustion cycle.
Exhaust scavenging is severely diminished, polluting the fresh inlet charge with a percentage of the last combustion episode.
So it defeats the purpose of wizz bang valve cutting procedures, head porting and other performance mods.
What causes poor IMP:EMP ratio.
Most commonly is poor turbo choice.
An under sized exhaust housing restricts the flow. A restrictive intercooler won't help matters along with a restrictive exhaust system.
When you upsize the turbo to pump more air, the exhaust side also needs attention to make sure the increase in air can flow without restriction.

Another phrase Banks coined ' the boost guage is dead.
Why is this relevant?
Well put simply psi measured by a boost guage doesn't tell the whole story.
Let's compare a mitsubishi 16L turbo with a Garrett 3071. If they both make 15psi on the guage the Garrett will move considerable more air for the same pressure.
This is the misconception most make with a bigger turbo when saying it doesn't spool quick enough.
Yes the pressure might be less but the volume will be more.
Hence the boost guage is dead.
The bigger turbo also has the benefit of moving more air with less heat produced in the turbo air thus improving intercooler efficiency.
 

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Crystal clear explanations for those who would still have doubts... THANK YOU ! ! !

Boost is not a mesure of 'power', has never been, and never will be. It is a pressure.
ex : You can build up high pressure in an air-tank, and have NO flow of air at all.

High EMP vs IMP is your worst enemy. Opening turbo vanes as boost builds-up is your friend against EMP.
MAF voltage is the one to maximize at all times (air volume/ air quantity) . Not boost ( pressure).
More MAF voltage for the same or even less boost is what you should be aiming at when modifying your turbo control.
 
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