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TD42 GQ
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Is this the thread we're talking about?
 

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Well when we did pump devolpment, our pump produced bubbles. Tightening the clearance improved pump performance and reduced bubbles. It was only with a impeller modification that cured the bubbles.
At a guess your impeller probably has longer vanes with lower vane tip speed. Cavitation is caused by net positive suction head available, being less than net positive suction head required at the impeller. In a closed system this still applies.
 

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GQ Ute 1990 Silvertop
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At a guess your impeller probably has longer vanes with lower vane tip speed. Cavitation is caused by net positive suction head available, being less than net positive suction head required at the impeller. In a closed system this still applies.
Interesting tech from the books on the subject but not in this case its more about holding the water in the vanes or blades so it doesn't escape lowering the potential pressure and recirculating the same water for each scroll pass.causing cavitation in a closed system. Contain the water in the blades with a top or bottom for a closed impeller system then your cavatation is reduced with the required net suction head creating flow volumes required for this engine which is the critical issue here.
 

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nissan patrol
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I had a strict criteria for the pump.
First and foremost it must be a straight bolt on to any unmodified td42 timing cover.
Then we used genuine Nissan pumps and improved on the original design.

Firstly we made pressure with the pump.
Flow was also increased.
Cavitation was still evident as the pump didn't respond to the normal changes that remove cavitation in other pumps.
We then modded the impeller again and the cavitation issue was solved.

Then came the vacuum issue.
This required a change in the cooling system to remove vacuum created.

This is currently in test everyday for probably the last 4 months.

Pump operation looks good, but testing shows high EMP in the exhaust manifold and is causing heat retention issues.
I have a new turbo to try to reduce the EMP and also bump up power output.
 

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Pump operation looks good, but testing shows high EMP in the exhaust manifold and is causing heat retention issues.
I have a new turbo to try to reduce the EMP and also bump up power output.
Interested to hear if you found there was a specific point where EMP started causing heat issues. How high is your EMP:IMP ratio and at what ratio did it start having an effect on coolant temps?

What turbo was that with and what are you planning to swap it out with?
Not trying to stir chit about turbo choices just really curious about EMP and coolant temp relationship
 

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nissan patrol
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EMP ratio is close to 2:1.

I think from memory there was about 10psi in the inlet and 17-18 at the exhaust. And it only got worse as boost increased.

The 'pump guy' has seen on other engines the same scenario.
EMP at other the 1:1 is a restriction in exhaust and holds back the heat affecting the exhaust ports.
It's like the engine is constipated and can not effectively get rid of its waste.
This puts extreme pressure on the cooling system around the exhaust port water galleries.
Localised boiling occurs, and the rest you know about.
Other side effects of high EMP is not being able to evacuate the spent gasses from the cylinder before adding a clean charge.
Gale Banks is quoted as saying this is the poor man's EGR.
Trying to burn the same charge twice.
High EMP has a negative impact on the cooling system, power, economy and emissions.


The turbo chosen for replacement is a Garrett.
Not the usual suspect, but something a little bigger than what's considered the norm.
 

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Yeah I'm aware of all that I just figured with all the specific testing and amount of data you gather you'd have found a specific EMP: IMP ratio that the cooling system could no longer cope with. Plenty of guys out there running around 1.4:1 ratio with zero cooling issues so was just asking what ratio yours got to with all the cooling upgrades before it overwhelmed your upgraded system.
 

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nissan patrol
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Yeah I'm aware of all that I just figured with all the specific testing and amount of data you gather you'd have found a specific EMP: IMP ratio that the cooling system could no longer cope with. Plenty of guys out there running around 1.4:1 ratio with zero cooling issues so was just asking what ratio yours got to with all the cooling upgrades before it overwhelmed your upgraded system.
I doubt 1:4 would have 'zero' issues.
It's more like what people are prepared to put up with.
 

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Just wondering how our pumps create pressure when they are designed as a flow pump? Wouldn't changing the impeller design mean that you are creating a restriction, therfore creating more pressure? Are these pumps not just designed to move fluid rather than create pressure?

Just a dumb plumber looking at it from a hydraulic perspective.
 

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I'll be honest I'm not sure what Mr Nissan was thinking when he designed the water pump for the td42. At its best in standard form the water pump is barely a circulatory pump. It's suffers badly from cavitation and flow is easily stopped.
A couple of things among others that don't bode well for a efficient cooling system. This is why we have chosen to modify the standard water pump to bring the cooling system up to scratch.
 

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For what you are trying to achieve, no cavitation at the pump, mean that you are giving away flow to achieve this? Are you measuring flow on what you are doing compared to the original pump impeller, or even the upgraded JPC pump impeller?
 

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For what you are trying to achieve, no cavitation at the pump, mean that you are giving away flow to achieve this? Are you measuring flow on what you are doing compared to the original pump impeller, or even the upgraded JPC pump impeller?

Pressure and flow are increased from the standard pump.
Speaking to JPC, he was unable to give any specifications regarding their pump. He admitted that he had not tested it for pressure, flow or cavitation but merely stated that it's design is an improvement over stock.

Armed with this knowledge I wasn't going to outlay $500 + for an unproven product and then have to go through the testing process.
 

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Just for records,
TD42ti, cracked top rad tank, has run ~ 100K km, so not too bad, went to Radiator guy and ordered identical Adrad radiator complete, Alloy/plastic ~ $450
Next day he fitted a Fenix version, not happy I agree to trial run. drove 15km, mild conditions under load, temps to straight to 98 deg, and rising (normally sits on 78-85)
Went back, replaced with Adrad, inspection sees larger ID cores and more of them,
Test drive all normal,75-78, summary Fenix are not up to the job.
Adrad still runs hotter than Nissan std version rad. It will get up to 100+ in summer under load
 

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TD42 GQ
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Just for records,
TD42ti, cracked top rad tank, has run ~ 100K km, so not too bad, went to Radiator guy and ordered identical Adrad radiator complete, Alloy/plastic ~ $450
Next day he fitted a Fenix version, not happy I agree to trial run. drove 15km, mild conditions under load, temps to straight to 98 deg, and rising (normally sits on 78-85)
Went back, replaced with Adrad, inspection sees larger ID cores and more of them,
Test drive all normal,75-78, summary Fenix are not up to the job.
Adrad still runs hotter than Nissan std version rad. It will get up to 100+ in summer under load
I tried a cheap Ebay copper/brass (bad), then a re-cored genuine (not much better), finally a Koyorad alloy/plastic which is acceptable. The genuine copper/brass GQ rad was still the best, but after 28 years it just corroded away...
 

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After 18 mths of kettle issues, a new qikazz fan thru radiator, dt97a and finally cracked head I have done the following and have won.
After cracking head and replacing with new genuine I replaced everything in cooling system with new genuine. Fitted td42t fan and hub, original thermo, original radiator cap and td42gu radiator. I have a 93 blacktop, 16 mamba, original 10mm fuel pump, top mount hpd.
After reading all of these I kept coming back to forming a negative air pressure behind radiator. After checking my vehicle it was obvisious the negative pressure was forming just below bullbar and in front of radiator causing a big percentage of air to not flow thru radiator but under truck. Air will take the path of least resistance.
Got some rubber matting and blocked it off as in pic. Now negative pressure forms behind radiator low under the block causing alot more air to flow thru radiator. Temps are alot more stable and on 35 plus days will not go over 105c with aircon on pushing up hill in 5th at 110 on motorway. Previously would go berserk.
Also need to understand these motors operate safely from 76c (thermo open) to 118c.
Also with the negative pressure now situated under the block, its pulling alo tg more heat out which makes the gearbox alot cooler can feel it in stick and tunnel. View attachment 514129
Mate when you mention engine temps, are these engine coolant temps or block temps?
 

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nissan
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I'll be honest I'm not sure what Mr Nissan was thinking when he designed the water pump for the td42. At its best in standard form the water pump is barely a circulatory pump. It's suffers badly from cavitation and flow is easily stopped.
A couple of things among others that don't bode well for a efficient cooling system. This is why we have chosen to modify the standard water pump to bring the cooling system up to scratch.
How you going with your pump, any updates?
 

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nissan
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Just for records,
TD42ti, cracked top rad tank, has run ~ 100K km, so not too bad, went to Radiator guy and ordered identical Adrad radiator complete, Alloy/plastic ~ $450
Next day he fitted a Fenix version, not happy I agree to trial run. drove 15km, mild conditions under load, temps to straight to 98 deg, and rising (normally sits on 78-85)
Went back, replaced with Adrad, inspection sees larger ID cores and more of them,
Test drive all normal,75-78, summary Fenix are not up to the job.
Adrad still runs hotter than Nissan std version rad. It will get up to 100+ in summer under load
Good information to have, how is it manufactures can just wing it with their designs?
 
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