rivmasta

hey all,

newbie here asking a question on behalf of a mate.

He's installed an 3.3 import engine into an offroad racecar and is having an overheating prob.

Fine on tight and twisty, fine on the dyno, overheats when on long straights at high RPM.

He's already put in a bigger aluminium radiator and ducted it. changed thermostat, checked tune up high to make sure its not leaning out, changed water pump etc. all the normal stuff you might think of. Not being a scooby guru though he's running out of ideas.

Was hoping that someone here might be able to say "oh right he's got x wrong with it! common problem" and he'll go on to win a big race and name me as his saviour in his acceptance speech.

Basically I want to cash in on your knowledge! haha!

seriously, any help appreciated.

Spyder550

Where is the engine mounted in the off-road racer?

rivmasta

rear engined driving an audi transaxle.

jaytc2003

iTrader: (1)

airlock in the cooling system?

incorrect ignition timing

The Zohan

OK, what is high speed in this vehicle?


Where is the rad mounted, is it getting enough airflow at high speed, could it be being effected by aerodymnamics and the air not getting onto the airscoop/intake, please post picture(s) of the vehicle.

Have you got a leccy fan (or two) fitted, is this themostatically controlled or manually, might want to put in a manual switch to override.

Spyder550

What is the routing for the coolant circuit like, I previously had some copper plumbing pipe in my mid engined project when it was alfa sud powered. Have ripped it all out as I need to put bigger bore in, but evidently the 90 degree bands I had in the circuit did not help.
Also have you tried Aussieveedubbers - Home there is a Subaru swap section on it

doppelganger

have the 2 heater pipes been linked ?
try running with no stat see what effect that has.
90% bends arnt really a prob if they are swept bends as opposed to knuckle.

rivmasta

Cheers guys,

Will chase the guy up for pics, but heres a description.

Engine is mounted low, radiator is mounted right behind the driver/navigators heads in the centre of the vehicle. Example below is my own car, but the subi powered one is similar, except his is mounted a bit higher up, and is an aluminium aftermarket radiator.



Timing - was checked on the dyno I believe with no ill effects
Air lock in water system - checked I believe
High speed is from 160 to 200km/h and can be held flat out for ages
2 fans fitted both controlled by motec
dont know about routing for cooling circuit - but I think he's had a look as to which hose goes where, also dont know about heater hoses. will throw it at him.

Will get back to you! cheers!

JOR166

G,day,
I am the owner of the above vehicle.
We can positively say the engine is not overheating due to the cooling system. The problem definitely relates to the engine specific!
Firstly, the car has run a toyota V8 engine for 3 years with the existing cooling system no probs...but I have now upgraded to a bigger radiator and electric waterpump (includes original), due to this engines problems. I have tried thermosat, no thermostat, and modified thermostats, extra ducting...goes on and on.
My conclusion is that all subarus must run hot on the right side of the block (looking at front of engine) as the coolant cannot freely escape out the crossover pipe (is that why the 3ltr H6 engine has two top hose outlets?).
All external hoses (ie heater hoses etc) have been blocked and not used. I have heard the heater is the bypass, but as I dont use thermostat, it should'nt matter.
No air locks exist!
I thought of waterpump cavitation, so fitted an electric pump in line.
99.9% sure headgaskets are o.k.
Temp sensors located in O.E. position and are accurate.
Engine is NOT leaning out or timing issues.
I have run an extra waterpipe from r.h. crossover bend (near temp sensors) to the top radiator hose to try and cool this corner. Is this a mod anyones heard of?
I have heard if headgaskets fail in 4 & 6 cyl scoobs that it is always the #4 or #6 cylinders, is this an issue?
The engine runs up to about 115 deg C, after travelling about 70km at high speed approx 180kph and at the rev limit of 7700rpm.
Also, does anyone know what these motors can reliably rev to?
Any help would be greatly appreciated...thanks to rivmaster for finding this site

500

Sounds like the water pump is circulating the water too fast and it's not letting the cooling system take the heat out of the engine. try a bigger pulley on the water pump

doppelganger

could the same be achieved by running a thermostat all be it a colder opening one ??

500

Nope, a colder thermostat will just change the temp at which the rad circuit opens, once the system is open, it is open and temps will continue to rise. a longer rad may help. as the water spends more time in the rad.

If you read the post, he has run without any thermostat and still encountered the problem

doppelganger

ive read the posts but was just looking at all options really ,well if it isnt air locked then it would point to a cooling design fault wouldnt it?
and in respect to the water crossover manifold would some thing like this help
i know its not the right engine but i do know on the wrc cars its seen as a week spot in the cooling.

Lateral Performance

iTrader: (20)

What oil temps are you getting ? are you using an oil cooler ?

IIRC, the SVX engine has a 6500rpm limit, and you're running it up to 7700rpm, WAY above it's normal operating parameters, and not just for a few seconds, or minutes, but for 70km, in hot ambients, and reduced air flow to cool the engine !

I'm not aware of any issues with the Subaru water system, and Prodrive don't replace the water cross pipe because of poor flow.

I can't remember the water flow path, but I wonder if it would be better to join the heater pipes, instead of blanking them ?

What water temps do you get driving under more normal driving conditions ?


Mark.

doppelganger

i was only going on what i was told but i am curious now as to why they do it?

JOR166

Thanks for your help fellas.
I used to believe in water flowing too fast, but have since discovered that in racing conditions, faster the flow the better. But even so, I have fitted a bigger radiator and tried running thermostats with no improvements!
That crossover pipe is exactly what I had in mind, do you know why this engine has had it modified? Could it be the reasons I'm suggesting?
I am not running reduced air flow (compared to a sedan), and probably have a more efficient system. Maybe I should lower the rpm's, but I will lose too much top speed, and gearing up would mean the engine may not have the power required. Our races actually run between 300 + 500km, with many high speed sections, and also many slow speed sections...it's very hard on machinery, including engines! So normal operating temps are hard to suggest. I dont run an oil cooler or oil temp guage.
I think the wrc crossover pipe design has a lot of merit, but no-one so far (exept doppleganger) has been able to confirm this theory...I thought my problem mat have been common, but I guess not!
BTW, I dont believe hooking up the heater pipes to be an advantage...I have studied the water paths and it would only transfer hot coolant between the l.h. crossover corner back to the thermostat housing. (not getting rid of the hot coolant, just circulating it)
Thanks again everyone

doppelganger

i will find out about the crossover pipe but cant til mon-tues.if sooner ill post

Lateral Performance

iTrader: (20)

I would definitely monitor the oil temps, and the pressure. You're running your engines hard, and far longer than we do, even on track.

We need to run oil coolers on the bigger power 4 cylinder engines, because oil temps can rocket (120C +), and it's possible part of your problem is very high oil temps, causing the water temps to run high too.


Mark.

JOR166

I am racing this weekend, will let you know how the engine goes.
Only a short event 1x 40KM race, 3 x 20km races, 1 x 100km race.
Hopefully this will be enough to give me an indication of how some of the mods are going!

doppelganger

after a convo with a mate who works on wrc cars here is a bit of convo.>
after finding out you have no data logger
you could buy 6 10 quid volt meters with temp probes. stick the probes where you want them. go out blast round and set a vidio camera looking at them... thats a loging system and i bet you will find the problem
i say .> something

he says.>
but it would work.. all you need to do is find where the heat ISNT going
i say.>
so why do your works cars have a modded water cross over pipe
he says.>

better flow, we used to get horrendous localised det at hot spots on the heads. by shifting loads more water over the engine it stopped a hell of a lot of our big problems. it also allows us to run more boost. That probably is whats wrong with his in all honesty. it just isnt pumping enought water over the engine at high speeds. an auxilary electric pump would sort it.

rivmasta

cheers guys,

jones - you running an elec pump this weekend?

JOR166

Thanks again doppleganger...you are a great help. I am becoming a forum convert, saves a lot of phone calls!
This weekend I am running an electric waterpump in conjunction with the (new) original waterpump.
I have also run an extra 5/8 hose from the r.h. bend of the crossover pipe to the top hose outlet. I have drilled extra holes in the crossover pipe for my temp sensor so I can reposition sender unit over the weekend to different locations.
Your WRC mate pretty much confirms what I suspected, please thank him for his info

JOR166

Car ran good, motor still overheats. Another competitor has also fitted the same engine and overheated his also!
At total loss now. Will rebuild engine to be sure, build a new crossover pipe, and redyno etc., does anyone know of cheap alternative pistons to increase capacity to 3.5ltr.
Also, what do people think of where to pick up the temperature...should we measure the cool side of the radiator, or the hottest part of the engine? As a high performing engine, the coolant will get hotter at the outlet, but the bigger radiator will cool it for the inlet.

JOR166

We now have 5 engines overheating in different race cars...so its not just me or my cooling system!
Desperately need help....hate to say it, but I think subaru have really stuffed up with these engines!

500

Have you monitored the Oil temps? As Mark has said, do you run an oil cooler?

May be worth investing in one and see how it goes.