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After reading the earlier posts I looked under my Y61 GU 4.2TDi and saw no panel underneath. So I used a rubber sheet and went from the bottom of the radiator back to close to the steering linkage across the width of the chassis rails. Angled it down to below the centre of the diff. I also put a louvre into the bonnet scoop as pictured.
Automotive lighting Motor vehicle Rectangle Road surface Wood

I saw some difference in economy and was able cruise at 90 kph instead of 80 kph for same fuel and importantly felt significant increase in power. I am always fully loaded at 3.4 tonne gvm and have struggled to keep speed up hills. Now I can keep in the same gear and hold my speed much better. As for temperatures I only have the standard gauge and it never moved/moves so nothing noticed here. I live in Victoria and travel in the cooler months so not travelling in over 30 degrees weather.
So more power, same/better economy and a bonus of protecting the bottom radiator hose.
Thanks for the posts - makes a difference
 

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2005 TD42Ti ute
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Discussion Starter · #122 · (Edited)
Yes so this could be a bit of an example to all about the front vs top mount debate.

Also for everyone to consider the differences between something can can store a bunch of heat and something that actively cools the charge air a lot better.

Getting more airflow over any OEM style intercooler results in usually exactly that. They can be quite effective when given the correct airflow.

Big heavy cores like CC can work better when the airflow is no good but will suffer the effects heat soak for longer as there is more thermal mass.

Of course if you CC or larger TMIC and also get good airflow you will be better off again, How the air flows inside the intercooler can however be argued but that is besides the point of what I am investigating.

I theorise that the air movement at the rear of the engine bay can be somewhat dead given the air from the stack is supposed to leave the engine bay underneath/behind the front diff area.

Getting a good well flowing TMIC in can sort of make use of this otherwise dead airflow area and in some cases assist with the bay drafting characteristics.

Just going too much/big on this area with airflow while leaving the pressure behind the stack also high can actually cause issues with coolant temp.

This is why bonnet scoops to "cool the motor" like with no intercooler underneath them are rubbish.

The reality for 95% of peoples fully sick jacked up braced and custom setups is that this doesn't really work like it is memt to with TMIC. That's my opinion after playing with a few different setups now.

Fuel economy gains could be attributed to higher cruise afr, clutch fan disengaging more more a given job, more dense intake charge and lower boostpressure as when you cool air you are always going to see a slight pressure drop even in a non static environment.

I think some people easily confuse this with a restriction in the intercooler core but from my observations simply intercooling the charge air to any degree usually results in a drop in boost
pressure at the intake manifold To some extent.

I don't think this translates into a drop in EMP but buy have not yet done any testing to establish this.

The needle on the dash of 4.2 GU really doesn't move a lot until it needs to.

These gauges are more then fine for all your monitoring needs asides from the fact that having an audible alarm is handy for those who watch the road and not the dash.

Either way, with better airflow you likely have much more up the sleeve and it's a nice feeling.
 

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Discussion Starter · #123 ·
little bit more anecdotal ramblings of a fool.

Arrived in Toowoomba today, its wet, soggy, cold, windy and sad here ATM. some interesting observations worth discussing from the last 900 ish kms are:

Rain, does it help or hurt. from my findings with on road testing, rain can actually make your car run hotter by a few degrees (IF YOUR AERO IS GREAT)

i am currently theorising that this is due to the wet coil effect (as i will name it for the sake of this comment)

So some years ago i was working on a split system A/C on cooling mode, and after wetting the condenser i observed some interesting pressures, pressure was observed to drop with waterflow over the coil but then to increase after the water flow had stopped, and increased past what a normal pressure would have been given all other variables. so after arguing with a bunch of peers i left it alone, however it became clear in time that if you wish to water cool a heat exchanger externally you need to keep the water flow high as once the coil is water logged the airflow and subsequent heat load removal ability suffers due to the water in the coil absorbing only as much heat as it can, but impeding airflow.

Hypothesis: this can translate to our cars potentially.

So my reporting's of today are of a max pyro of 760 and top hose ECT of about 89C - not holding back at all. (holding 100kph up some long climbs with quite a bit of load on the motor)

Stat bypasses: are they are a good idea or not. (i currently have one and im not really a fan)

They can most defiantly hurt, my car is struggling to achieve stat temp (currently 82C stat) WITHOUT running the heater what so ever. In "cold" conditions it can be quite hard to achieve stat temp So if im cruising at 100kph in 5th and pyro is around 400/450C in the manifold, i am struggling to keep my current 82C running temp. i am often running on 80/81C

There is many reasons we shouldn't run our diesels below about 82c, THAT BEING SAID there is a couple of reasons why one may opt for a stat bypass.

In failing an internal/external bypass being of adequate size to satisfy a pumps NPSHr, a stat bypass can serve to help reduce a high pressure behind the stat produced by a proper water pump and to also keep the pump fed.

If you are living in a tropical/hot area, this wont affect warm up time enough to be an issue.

This can help keep a more consistent pressure in the head which may not be as important as the resulting flow that is also function of this, in a proper bypass system.

In a cold area, this most certainly makes quite the difference.

this however relates in just about zero effect to upper operating temperature. This relates to control of ECT.
 

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Thankyou to Mike and all for inputting so much on here, some great info. I thought I’d share my findings in my own quest for a more effective cooling system.
2006 gu wagon Td42ti, 2” lift 285 MTs.
600x300x76 fmic,
Genuine Nissan winchbar, lowmount, no spotties.

Manometer readings;
196pa - behind grill infront of FMIC.
156pa - behind FMIC/infront of condenser.
136pa- behind condenser/infront of Rad.
60pa - next to Cylinder 3-4 @ headgasket height, driver side.

Have fabricated my own air dam, sealed as much as possible even side/edges and lower edge is centre of diff height. I will repeat all above tests, and probably add a 50mm strip of rubber to bottom edge.

Following that, I will also remove AC thermo fan and power steering cooler (in between FMIC and condenser) and see how it affects my readings.
I also have a UFI fan and hub on the way as my fan has signs of fatigue at base of each blade. Keen to see if this changes engine bay flow too.

Cheers,
James
 

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Discussion Starter · #126 ·
Thankyou to all for inputting so much on here, some great info. I thought I’d share my findings in my own quest for a more effective cooling system.
2006 gu wagon Td42ti, 2” lift 285 MTs.
600x300x76 fmic,
Genuine Nissan winchbar, lowmount, no spotties.

Manometer readings;
196pa - behind grill infront of FMIC.
156pa - behind FMIC/infront of condenser.
136pa- behind condenser/infront of Rad.
60pa - next to Cylinder 3-4 @ headgasket height, driver side.

Have fabricated my own air dam, sealed as much as possible even side/edges and lower edge is centre of diff height. I will repeat all above tests, and probably add a 50mm strip of rubber to bottom edge.

Following that, I will also remove AC thermo fan and power steering cooler (in between FMIC and condenser) and see how it affects my readings.
I also have a UFI fan and hub on the way as my fan has signs of fatigue at base of each blade. Keen to see if this changes engine bay flow too.

Cheers,
James
Thanks for sharing James.

Good to see someone is using some numbers to help guide them. It takes a little bit of thinking to make use of numbers but they are helpful once you can use them to see what's going on.

The numbers you describe is what we call our static pressure losses across the stack, of course as air encounters each exchanger in series we see a drop off in pressure.

If you can make this engine bay reading of 60pa greater - when the intention is to increase high pressure or "high side" mods, you can presume more air is flowing.
Examples of this would be removing spotties, fitting a more powerful fan, guide strips and bits of foam etc.

If you make this 60pa slightly less when doing "low side" mods or allowing the air to leave the bay unobstructed - you can also presume more air is flowing.
Examples of this would be your air dam, my inner guard mod, bonnet vents, my custom wheel well covers (at the back which facilitate air leaving easily over the top of the chassis here)

By the looks of the 3 bolts underneath - you have a skinny tall radiator?
If this is the case, i found on mine the splitter/diverter piece to help force air in here (at the bottom for the "free air section") to be quite the complement to the air dam itself. I get some pretty epic cold hose numbers at cruise (temp split)

my temp split can be up to 40 degrees at times of light load and at cruise. Just thought I'd suggest looking at that as well if your wanting to enhance it further.
 

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Thanks Mike.
Good way of looking at it in regard to using that static value and how our mods affect it,
Yes mate tall skinny Rad. My air dam bolts to Nissan bar, then those 3 m8s straight into the series IV lower Rad support/chassis member which hangs quite low, then about 100mm past the back of Rad is where my kick down of the air dam is. Benefit of this is it protects the lower Rad hose too!
Looking at your pics on page 2, your winchbar sits the winch a fair bit higher than my Genuine Nissan winchbar, so if you see my attached pic you’ll see I don’t quite have the free air gap that your truck has.
Unfortunately. Otherwise I would be all over that.
That’s kindve why when I made this airdam late last year I didn’t see any other choice than what I’ve done. Maybe collectively this thread will show me a better way to do it!

Due to my one piece air dam design starting at bottom lip of winchbar, I have also blocked of the curved sides of this lower chassis member, since Rad is a fair bit narrow than chassis rails. This seals to the top side of my airdam, and then foam/gorilla taped Rad to lower member in an attempt to seal Rad as much as possible.
 

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