Cooling System And Power

[Scooby]

Guys;

in the past I've known of many NA cars, particularly early worked cast iron V8s, that have gained economy, power and driveability by changing to a hi flow design water pump and a de-aeration tank. all of this is designed to produce more uniform and effective cooling in the block front to rear by removing air trapped in the water jacket. i've experienced a big difference myself in a big block chrysler and although the car ran at the same measured temp as before (and never ran hot in the first place) it ran much better. i wouldn't believe it if i hadn't witnessed it myself.

the n1 water pump for the RB26 has a plate behind the impeller and different shape fins, both of which were a characteristic of the hi flow pumps that i saw used previously. the japs are well known for over engineering cooling systems but the V8s didn't have an engine temp prob either, so i wondered if maybe there was a power gain to be had by using the N1, however slight.

Regards

[Warpspeed]

You only really need a high flow waterpump for slow idling in bumper to bumper traffic with the airconditioning going in mid summer, or maybe for towing.

At any reasonable operating Rpm the water flow will be controlled by the engine thermostat. What the waterpump does do at high power outputs is pressurise the cylinder head. By having 30psi to 50psi water pressure in the head, it greatly increases the boiling point of the water around the combustion chamber and exhaust ports at high power output. It prevents steam bubbles from forming.

What you require on a high power engine is not a high flow waterpump, but a pump that will generate very high pressures at high Rpm without cavitating. A pressure gauge connected to the cylinder head before the thermostat will tell the story. If pressure peaks at mid engine Rpm, then falls off of near redline, something needs to be done about the waterpump. Slowing it down may help, or different shaped fins, like the N1 pump has.

Going to a bigger pump, or speeding up the stock pump is exactly the wrong thing to do.

We all know what happens when you spill water on a red hot barbecue plate. It spits and balls of water run off the hot plate. Now picture a turbo engine on a dyno flat out at full load, with glowing bright red hot exhaust manifold. Think about the exhaust ports and combustion chamber deep inside the head. If there was little or no water pressure, steam bubbles would rapidly form and push all the water out through the radiator cap. The head would then over heat to destruction in seconds.

So think more about pressure than flow. If it needs more flow, the thermostat will always quickly open up and give it the flow it needs. The waterpump that generates the highest measured pressure without cavitation is the one to use on a high power performance engine.

[RB30-POWER]

A glcol based coolant would also help. Most are these days anyway.

[GTR32]

You only really need a high flow waterpump for slow idling in bumper to bumper traffic with the airconditioning going in mid summer' date=' or maybe for towing.

[i']A high flow pump is effective in traffic situation as many pumps just stall the water and cavitate at idle rpm. I've seen high flow/pressure water pumps assist in these circumstances but also at high and low engine speed/load. I've also witnessed a test rig where a perspex backing plate was applied to the back of a pump powered by an electric motor. At idle up to 1500 rpm no water movement. 2500 water moves, 3500 cavitation etc. [/i]

At any reasonable operating Rpm the water flow will be controlled by the engine thermostat.

The thermostat doesn't care about rpm. I've driven cars that were more responsive even when stone cold after being fitted with more efficient pumps.

What the waterpump does do at high power outputs is pressurise the cylinder head. By having 30psi to 50psi water pressure in the head, it greatly increases the boiling point of the water around the combustion chamber and exhaust ports at high power output. It prevents steam bubbles from forming.

Agreed

What you require on a high power engine is not a high flow waterpump, but a pump that will generate very high pressures at high Rpm without cavitating. A pressure gauge connected to the cylinder head before the thermostat will tell the story. If pressure peaks at mid engine Rpm, then falls off of near redline, something needs to be done about the waterpump. Slowing it down may help, or different shaped fins, like the N1 pump has.

presumably if the flow of water in increased, through the same size jacket, the pressure will increase ie more water in the same space at one time. and an efficient pump will generate pressure at all rpms without cavitating, clearly in proportion to the rpms

Going to a bigger pump, or speeding up the stock pump is exactly the wrong thing to do.

i don't think the size or speed of the pump is the question, it's the efficiency. i agree that greater water speed is not always the best answer, prob the worst in most cases, but we're not talking about overheating issues here, rather increasing the pressure in order to eliminate the formation of bubbles as you pointed out.

We all know what happens when you spill water on a red hot barbecue plate. It spits and balls of water run off the hot plate. Now picture a turbo engine on a dyno flat out at full load, with glowing bright red hot exhaust manifold. Think about the exhaust ports and combustion chamber deep inside the head. If there was little or no water pressure, steam bubbles would rapidly form and push all the water out through the radiator cap. The head would then over heat to destruction in seconds.

Agreed. The reason that air in the system is bad is not being questioned as I think it's understood.

So think more about pressure than flow. If it needs more flow, the thermostat will always quickly open up and give it the flow it needs. The waterpump that generates the highest measured pressure without cavitation is the one to use on a high power performance engine.

Agreed

I think what Scooby is getting at here that we know the GTR (and Jap cars in general) don't overheat but this could be for many reasons other than pump design (which I understand to be quite good in most Jap cars). However, I sense the question relates to whether a high pressure pump could reduce what little cavitation there is in the RB26 and yield some power results.

[mjfawke]

At any reasonable operating Rpm the water flow will be controlled by the engine thermostat. What the waterpump does do at high power outputs is pressurise the cylinder head. By having 30psi to 50psi water pressure in the head, it greatly increases the boiling point of the water around the combustion chamber and exhaust ports at high power output. It prevents steam bubbles from forming.

But not necessarily on the RB engine. It seems to lack a water outlet restrictor on the motor, and the pressure cap on the radiator will limit pressure on that path to ~ 15psi. So - I don't think this is an engine design which relies on block pressurisation. Modern designs tend to use high water flow instead of high pressure.

Which is bad, because the pump looks like cr*p, and I'm sure it cavitates badly. The only saving point is that the area around the pump is cast iron and won't corrode away like the 'L' series engines did.

Does anyone know where to get an EcoTech pump for the RB engine? They are based in Melb, but not on the web. They do cavitation-free impeller replacements...

[GTR32]

Which is bad, because the pump looks like cr*p, and I'm sure it cavitates badly.  

Does anyone know where to get an EcoTech pump for the RB engine? They are based in Melb, but not on the web. They do cavitation-free impeller replacements...

I agree the pump looks like a dog and I'd put money on it cavitating. Hence my and Scooby's posts.

Can't help with the Ecotech but have you tried 1223 for a number?

[mjfawke]

I agree the pump looks like a dog and I'd put money on it cavitating. Hence my and Scooby's posts.  

Can't help with the Ecotech but have you tried 1223 for a number?

I've looked everywhere. John Bennet (Bennett?) is the guy, heaps of articles in car mags etc. etc., but obviously likes his privacy.

Anyway - Steve from Speed Technology used a JB modified pump in Sinisha Banjac's RB27 240Z, so I might start looking in that direction. My engine temp goes out of control every time the air temp goes over 30. Water temp hits 85-90c, which appears to be O.K., but it would be nice to hold it on the thermostat. Everything else has checked out, so it looks like the pump will have to come off next. The pump has never been changed, and the prev owner of the engine didn't use coolant. Took a fair while to get the rust out

[GTR32]

I should've put two and two together and come up with John Bennett. It did cross my mind that it would be him but I didn't think he'd still be around the traps. I first knew him when he was starting this work in Melbourne in around 1993-4 through a CNC machine place called MD McAliece and Co, you might find him under that name in Airport West. It was his test rig I saw the pumps on, and it was his swirl pot/deaerator and thermostat relocation kit (to bottom hose) I put on a BB Chrysler.

He is an amazing guy and some of the testing he's done on things like cylinder charge distribution in V8 manifolds is incredibly interesting. He'd put perspex panels in the sides of cut away aftermarket manifolds so he could see what was happening inside and to cut a long story short it was tragic. He designed his own manifold to overcome these limitations on a SB Chevy and to say the result was impressive was an understatement. Another horror story was the temperature difference between the front and rear of the block - frightening.

Unfortunately he suffered from a bit of the nutty professor syndrome and after 18 months of being promised a pump for the BB Chrylser I pretty much gave up.

But he's your guy for water pumps alright.

If you speak to him say that Mark the Army guy from Karratha (as I was then) says hi, he might remember. A google search under some V8 related topics might yield a location, he was well known for fixing cars like a Holden 1 tonner with a 454 Chevy that was overheating despite having two huge radiators and 4 thermo fans. JB stripped all that out, stuck a swirl pot and one of his pumps on it and the problem went away. The owner thought JB was god.

Not sure he'll help you lower the temp of the engine as such, his theory was that the hotter the better within reason as this promoted thermal efficiency and atomisation etc (not so much of a problem with fuel inj of course). The key was apparently to make it possible for the engine to run happily at quite a high temp without boiling by stopping steam pockets from forming in the jacket through the use of a good pump.

Cheers

[JCMarshall_Law]

Just as a side note, it seems nissan has more than doubled the price of the R33 N1 GTR pumps in the past few weeks.

last week (27-1-05) I had my car sent for the 100k service and was planning on getting the N1 pump installed as I was told (by Gavin woods Autotech in Queensland) that they were ~$160 (standard was $95). I was called a couple of hours later and they said since they last ordered one of those pumps, the price had more than doubled, something like $350 now. So already facing a $1300 bill, I had to go for the standard pump, bummer.

[mjfawke]

Whoo hoo! I found the phone number! And it matches the business mentioned above.

Md Mc Aliece & Co P/L 23 Webb Road AIRPORT WEST 3042 (03) 9338-5311 (03) 9335-3421

I found the phone number in a story on their LPG bus engine conversion in "Performance Buildups" from 1999, and found it listed for the business above. Which is strange, because in the article they say that Eco Trans is Johns company.

I'll call them on Monday.

[Scooby]

Let us know how you go Michael.

[mjfawke]

Hmmmmm. The phone just rings out...

[mjfawke]

I rang Steve Newing @ Speed Technology.

The pumps were a custom job, and with a head gasket mod supposedly fixed all of the detonation problems. And yes - the RB block does build pressure inside the head - must have restricted outlets.

When they did their previous batch, the replacement impeller cost around $330 on top of the price of the pump. The design is similar to the $800 NISMO pump (not the N1). Steve is going to work on a price and email me back. If we can find EcoTrans, I guess we can get some competition going here

[RPMGTR]

You will find that the pump is not at fault........we use std GTR or N1 pumps in all the street/circuit cars from 250 up to 500kw @ wheels with no probs at all.........They never get hot in traffic, can do 10 ten laps in 30degC at the track and the water stays at 85degC (even with 500kw).......best look at your radiator/airflow management instead...

[mjfawke]

Just because the stock style pressed impellers work "O.K." doesn't mean they can't be improved on. The L series pumps used cast impellers with shaped vanes, and they still cavitate like crazy under high RPM. I would have thought the RB was a sorted design, but most of race motors seem to be running de-aeration tanks... The N1 pump being 'low flow' also indicates a cavitation problem with the stock pump. So - it's good insurance... but a bit expensive.

In my case, everything is fine until the rad has to work hard, then all of a sudden it takes a 10 degree jump in water temp. It also pump about a litre of water into the catch tank, even though the water temp only hits around 85c to 90c, so I'm thinking cavitation... and the pump is original, and wasn't run with coolant for a period of time.

[mjfawke]

I tried to get in contact with John Bennet again. Phone rings out, second number is not valid.

[Scooby]

You will find that the pump is not at fault........we use std GTR or N1 pumps in all the street/circuit cars from 250 up to 500kw @ wheels with no probs at all.........They never get hot in traffic, can do 10 ten laps in 30degC at the track and the water stays at 85degC  (even with 500kw).......best look at your radiator/airflow management instead...

Hi RPM, just to clarify (and with due respect to Michael's comments) what I've been referring to here is not an overheating issue. While some cars I've observed with these pumps were cured of overheating, not all overheated in the first place. But in all cases economy, driveability and power improved because of deaeration in tyhe jacket and no cavitation at the pump. My car actually ran warmer with the pump on but it was nearly impossible to get the thing to boil, even when we tried to drive the temp up.

Micheal from memory the rengineered fill point is because of something being moved in the engine bay rather than inadequacy of the original one.

Cheers

[Sydneykid]

An interesting thread this one, my 20 cents worth.

The N1 water pump is not designed to stop cavitation, it is designed to slow dow nthe movment of water at high rpm. The race teams found that with the standard pump the water moved so fast around the engine that it didn't absorb the heat. So they came up with a "cut back" style of water pump that slowed the water movement down. This is good for a circuit race car that has sustained high rpm, but not so good for a road that sees lots of low rpm. I would never put an N1 pump in a car that sees any road work.

In extreme cases (over 9,500 rpm) I have seen slight cavitation with the standard pump, but never any with the N1 pump. We run head and block water temps and a water systems pressure sensor all plugged into the Pi data logger, so I can see it easily from the logs.

Air in the cooling system is mostly caused by not bleeding all of the air out when you fill it up with coolant. The main issue occurs where you have the radiator cap lower than the highest point of water in the engine. It is hard to get all of the air out, that's why RB20/25's have a bleed hole on the top of the inlet manifold. It is the highest point, so you can let the air out and close it off when you get 100% coolant.

Swirl pots are used to remove this air from the coolant when it is not possible to ensure zero air is trapped. They separate the coolant from the air by a controlled swirling action in the pot. Plus the pot itself is usually mounted as the highest point in the cooling system, so the air naturally gravitates there. The swirl pot also helps when you have a boiling event which separates the oxygen from the hydrogen so tha tinstead of coolant and water you have coolant and gas. The boiling event can be localised (hot spot) or general (engine overheat).

I have never seen air get into the cooling system due to cavitation, cavitation is simply the water pump "spinning it's wheels and going nowhere".

Hope that helps:cheers:

[rev210]

easy way to fix cavitation is to run a reduction pulley on the water pump, it has the same drawbacks as the N1 pump from a traffic driving point of view, costs less to make a custom one than an N1 pump and the pulley is easy to change (4 bolts) if you want to switch them over for road use again (15min job) * assumes you have an electric thermo fan replacing the stock clutch fan.

[Scooby]

An interesting thread this one, my 20 cents worth.

The N1 water pump is not designed to stop cavitation, it is designed to slow dow nthe movment of water at high rpm.  The race teams found that with the standard pump the water moved so fast around the engine that it didn't absorb the heat.  So they came up with a "cut back" style of water pump that slowed the water movement down.  This is good for a circuit race car that has sustained high rpm, but not so good for a road that sees lots of low rpm.  I would never put an N1 pump in a car that sees any road work.

In extreme cases (over 9,500 rpm) I have seen slight cavitation with the standard pump, but never any with the N1 pump.  We run head and block water temps and a water systems pressure sensor all plugged into the Pi data logger, so I can see it easily from the logs.

Air in the cooling system is mostly caused by not bleeding all of the air out when you fill it up with coolant.  The main issue occurs where you have the radiator cap lower than the highest point of water in the engine.  It is hard to get all of the air out, that's why RB20/25's have a bleed hole on the top of the inlet manifold.  It is the highest point, so you can let the air out and close it off when you get 100% coolant.

Swirl pots are used to remove this air from the coolant when it is not possible to ensure zero air is trapped.  They separate the coolant from the air by a controlled swirling action in the pot.  Plus the pot itself is usually mounted as the highest point in the cooling system, so the air naturally gravitates there.  The swirl pot also helps when you have a boiling event which separates the oxygen from the hydrogen so tha tinstead of coolant and water you have coolant and gas.   The boiling event can be localised (hot spot) or general (engine overheat).

I have never seen air get into the cooling system due to cavitation, cavitation is simply the water pump "spinning it's wheels and going nowhere".

Hope that helps:cheers:

Thanks SK, was hoping you'd join this thread. Very interesting about the N1 pump on road cars. From your comments can we safely say that:

the standard pump doesn't cavitate unless rpm >9500 and therefore doesn't really need improvement in a road car

the bleed hole on the RB26 is sufficient to get all of the air out or at least enough for the remaining air to have a negligible impact and therefore a swirl pot is not required in a road car

Regards