Cyl No. 6 Lean Out - Theory Vs Practical

[Scooby]

This thread has definately brought out some good reading.

Back to the Lean Out issue.

Because No. 6 cylinder is so far from the cooling system pump, We have fitted some extra plumbing into the cooling system to remove the steam out of the engine. Has enybody done the same to thier RB engine?

Yes

Guys; sharing is good can you post some pics please and a description of what you did? I've long held an interest in cooling systems and elimination of temp differential in blocks - this is an often overlooked area because it's not 'visible'. If only the horrors of some cooling systems were more widely known...interestingly I see the previous edition of HPI has a Jun 2.7 on the cover built by CRD that has a 3 take off points for the cooling system in the head. Now that's what Im talking about. Some say it's only good for big kw engines but I'm not convinced, I experimented with a simple de aeration tank and some other minor mods on a 440 ci Chrysler and the difference was amazing.

Regards

[R31Nismoid]

These workshops that are doing cooling mods with stock plenums must have NFI if its the plenum itself...

Am i reading that point of view correctly?

[Turbine]

I have got a pic of the setup on our engine that I'll post shortly.

I guess its all about balance and with the goal in mind being the ideal charge air temp ACROSS all cylinders.

If you have No.1 cylinder head temp is running cooler than No.6 cylinder head temp, it must have an effect on the density/velocity of the air that travells across the chamber.

It's my way of thinking that you should have your charge air temp TO the cylinders at the same temp as the water that exits the cylinder head, about 60 - 80*C. May sound strange to some but the air changes its speed with temperature changes. Also at this temp the air is still reasonably dense, if you go below 60 it moves too slow, if you go above it looses density.

In a low HP engine it's not a real problem but for an engine developing 300 od HP per litre, if its not right you loose an engine.

Doing this also reduces the stress of developing horsepower, the engine is more relaxed or more dynamically balanced.

Anyway enough crap from me.

Later.

[MattSR]

Last time I posted these pics it was greeted with a touch of cynicism.. perhaps in the context of this discussion it will make more sense to people now..

[R31Nismoid]

Last time I posted these pics it was greeted with a touch of cynicism.. perhaps in the context of this discussion it will make more sense to people now..

I've seen that style of setup on many many RB motors of good power.

[Fitzpatrick Speed Works]

Thats half way there that is what the japs refere to as the gt head cooling kit, basically there is a water chanber that catches the water that circulates around the inlet manifold, there is water around this to help cold start and emmsions control on cold start. This is the highest point of the gtr cooling system and you will see a bleed valve fitted from the factory for this. The chmaber collect at three points the in the example provided they have simply removed the catch chamber and made pickup point that direct the water straight into a catch can this stops air buble ie steam whic is hoter than water building up and causing uneven cooling of the head. I would also loose the chamber on the underside of the plenum that runs forward and lets the water out of the head at the front of the head where the radiator hose connects. Lose this chamber and tap 3 dash 12 fitting in hear that go straight into you radiator in conjunction with the header tank and you will have a bloody good system!!

[Sydneykid]

Thats half way there that is what the japs refere to as the gt head cooling kit, basically there is a water chanber that catches the water that circulates around the inlet manifold, there is water around this to help cold start and emmsions control on cold start. This is the highest point of the gtr cooling system and you will see a bleed valve fitted from the factory for this. The chmaber collect at three points the in the example provided they have simply removed the catch chamber and made pickup point that direct the water straight into a catch can this stops air buble ie steam whic is hoter than water building up and causing uneven cooling of the head. I would also loose the chamber on the underside of the plenum that runs forward and lets the water out of the head at the front of the head where the radiator hose connects. Lose this chamber and tap 3 dash 12 fitting in hear that go straight into you radiator in conjunction with the header tank and you will have a bloody good system!!

Almost as good as the standard one.

cheers

[Fitzpatrick Speed Works]

haha! Nothing like really!!

Your directing the water straight out of the head into the radiator not allowing it to gather and wait around the bottom of the head till water ahead of it is moved. plus this way increases volume and cooling effeciency as the lines can be kept away from the engine again staying cooler!! The standard sytem is ok but it has its limits and drawback the main one it was designed with cold starts and emissions in mind as well as effiecency. As we are all building race cars (haha) we can get rid of 2 parts of the equation and concentrate on the most important thing cooling of the engine in particular common rb or straight 6 problems of the back of the head heating up air bubbles in the cooling system!

Cheers

[discopotato03]

I guess theres pros and cons for doing it that way though it would possibly be simpler to retain the std manifold (water collector wise) and run some small bore lines to a header tank at the highest point to prevent buildup of steam pockets . Manufacturers go to a bit of trouble to make cooling systems work because if they don't the business fails .

I agree that having inlet manifolds water heated helps with emissions ( and warm up , and cruise comsumption , and iceing) particularly at small openings but you can get around this to a degree with cooler thermostats if performance is the no 1 priority .

Gary may have asked before but did the GMS cars use all std inlet manifold bits coolant wise ?

Cheers A .

[Sydneykid]

I guess theres pros and cons for doing it that way though it would possibly be simpler to retain the std manifold (water collector wise) and run some small bore lines to a header tank at the highest point to prevent buildup of steam pockets . Manufacturers go to a bit of trouble to make cooling systems work because if they don't the business fails .

I agree that having inlet manifolds water heated helps with emissions ( and warm up , and cruise comsumption , and iceing) particularly at small openings but you can get around this to a degree with cooler thermostats if performance is the no 1 priority .

Gary may have asked before but did the GMS cars use all std inlet manifold bits coolant wise ?

Cheers A .

Hi A, no the Gibson cars had the radiator lowered so that the ambient air inlet and the air filters for the turbos could go above the radiator. Since the radiator was lower, the filler on the header tank was no longer the high point, so it wouldn't collect the air. So they had a aluminium collector mounted up near the brake master cylinders, as it is the high point in the engine bay. It had 3 small hoses so the air could travel up to it, hence eliminating the chance of any trapped air bubbles.

I have posted pictures in the Group A Skylines thread.

cheers

[discopotato03]

Searched , can't find that thread . Link ?

[Scooby]

Manufacturers go to a bit of trouble to make cooling systems work because if they don't the business fails .

Cheers A .

Yes but there's 'work' and 'work'. Does it work when it doesn't puke coolant everywhere in summer and the temp gauge looks good - oem consideration - or does it work when apart from that the front to rear block temp distribution is even and this means all cyl can run on greatest efficiency with no hot spots?

In my BB Chry with cooling mods the temp went up but remained rock solid in all ambient temps under all conditions. Hotter but more constant engine temp with less chance of internal boiling meant greater efficiency, more economy, more driveability and power. I'm not tryng to compare the Chry and the car it was in - recipe for boiling for a lot of reasons - with the RB26 as the GTR even has, heaven forbid, a proper cooling system bleeder stock.

Most of us would agree that a large temp difference between 1 and 6 in an RB26 would not be a good thing, and we'd also agree that a difference must exist. But does anyone know what it is - circumstance dependant of course? Hands down SK. I'm trying to find out if anyone else knows, to see how prevalent the knowledge is of something that we see every time we look under the bonnet but never really see if you know what I mean.

Regards

OK SK, how much is it?

Edited June 21, 2006 by Scooby

[ISL33P]

these photos can be seen in more detail on "JUN" r32 gtr canberra car in hpi issue no 67 pg 50 onwards

[Sydneykid]

Searched , can't find that thread . Link ?

http://www.skylinesaustralia.com/forums/in...21344&hl=Gibson

Try searching Sydneykid and Gibson

Cheers

[Sydneykid]

Yes but there's 'work' and 'work'. Does it work when it doesn't puke coolant everywhere in summer and the temp gauge looks good - oem consideration - or does it work when apart from that the front to rear block temp distribution is even and this means all cyl can run on greatest efficiency with no hot spots?

In my BB Chry with cooling mods the temp went up but remained rock solid in all ambient temps under all conditions. Hotter but more constant engine temp with less chance of internal boiling meant greater efficiency, more economy, more driveability and power. I'm not tryng to compare the Chry and the car it was in - recipe for boiling for a lot of reasons - with the RB26 as the GTR even has, heaven forbid, a proper cooling system bleeder stock.

Most of us would agree that a large temp difference between 1 and 6 in an RB26 would not be a good thing, and we'd also agree that a difference must exist. But does anyone know what it is - circumstance dependant of course? Hands down SK. I'm trying to find out if anyone else knows, to see how prevalent the knowledge is of something that we see every time we look under the bonnet but never really see if you know what I mean.

Regards

OK SK, how much is it?

The issue here is the drag racing guys don't really care, the run is too short for it to be an issue. If they have huge power, they concrete or expoxy fill the block, which changes the fluid flow dramatically.

Only the ciruit racing guys really experience temperature differential over time. We don't go much over 650 bhp as the additional lag at that power level makes the car slower. Hence we don't see large temperature differences, it is only on the engine dyno that I have been able to measure it with any accuracy. One day I will stick a temp probe under each spark plug washer (like we do on the karts) and measure it during a race. But it honestly, so far has not been an issue for us, so it's not high on the priority list.

cheers

[Turbine]

You're kind of right with the drag race engine, but this subject on the No. 6 lean out interested me enough to setup the engine/trans in our race car to be capable of running longer before a run than usual.

1 reason so as not to get burnt down on the start line and second reason was to keep all the temperatures up and stable for the run down the strip.

Back to that water setup, I cant post the photo from our web site so I'll explain it a little.

TurboX has used a Diesel fuel filter housing turned upside down with the drain vent to the top placed near the brake booster (filter removed). All the small water hoses for the intake manifold stay in the stock position but are 'T'd off to the housing where the steam is released.

You can check it out at Turboclub.com just look up for the Skyline GTS4 RB20DET mods.

It's a great idea of His, but such a pain in the neck to fit hoses to with that modified intake plenum.

Cheers.

[kiwi32]

If fuel pressure is a factor why not turn the fuel rail around so that the inlet is at the front and the pressure reg is at the back? if the leaning out issue is tranfered to the front cylinder you then know that fuel pressure is a factor.

just a thought

[ISL33P]

sydneykid - any luck with egt logs or fuel maps or clarification of your comments ?

[R33S2]

Just to clarify the fuel rail pressure drop, in hydrualics if you have 2 cylinders on the same line the furthermost will rise first and the closest will extend last, to get even pressure on both you use a regulator block to split it evenly. If you put a Y piece in the results vary but is a more even rise but for accuracy is useless.

Just to put a different spin on it, you guys explained it well but even I got a bit lost there LOl.

[Scooby]

The issue here is the drag racing guys don't really care, the run is too short for it to be an issue. If they have huge power, they concrete or expoxy fill the block, which changes the fluid flow dramatically.

Only the ciruit racing guys really experience temperature differential over time. We don't go much over 650 bhp as the additional lag at that power level makes the car slower. Hence we don't see large temperature differences, it is only on the engine dyno that I have been able to measure it with any accuracy. One day I will stick a temp probe under each spark plug washer (like we do on the karts) and measure it during a race. But it honestly, so far has not been an issue for us, so it's not high on the priority list.

cheers

I guess temp is not the only determinant of pocket boiling in a pressurised system, the presence of air plays a major - if not the major - part also. Even if there is a relatively consistent temp front to rear, cavitation caused by the pump, or insufficent bleeding will produce air in the system so eventually the water will boil where the air is - for example it will even boil where the engine 'seen' temp is coolest if there is air in the system at that point. So consistent front to rear temp would be great, as long as we can make sure that the air is out.

Cheers

Edited June 25, 2006 by Scooby