Had my 25000km old since reco heads in the shop the other day to get a skim. They had rippled, warped or buckled a little and never overheated by the temp gauge anyway. The head gaskets had both leaked water to combustion chamber. The head gasket ring around the pot left a ring mark on the head which my machine shop guy was curious about.
I got a lecture about turbo boost pressures creating combustion temps that are hard on the alloy heads and that for best results and longevity I would be better off with cast iron heads. Of course I have made this worse by using gas as the motive power. There is not a lot of structural support in the head to keep it straight under the conditions and cast iron would resist the heat expansion and quenching shrinking going on.
Not to give up, water injection has been suggested, so gonna research as best I can the old Zoom Julian Edgar system using a chicken shed fogger jet and pump, while the US exchange rate is kind to us. The bits he sourced were US made. When I quoted the part numbers and prduct name some ten years ago a local irrigation place could get them. Armed with some numbers to find i will try the US myself via the web.
EA82T head gasket woes
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discopotato03
- Senior Member
- Posts: 2134
- Joined: Sun Mar 18, 2007 9:29 am
- Location: Sydney
There are a few unfortunate facts lost to many in the turbocharging world .
First is that its extra airflow rather than elevated inlet manifold pressure that is the power adder . If you could get the same amount of air into your cylinders at low pressures you'd make as much power as you do with higher manifold pressure .
The second is that boost pressure is a measure of resistance to airflow into an engine . If there was less resistance (restrictions) in the inlet system you can move the same volume of air at lower pressure .
The third is that elevated exhaust manifold pressure and temperature is the devil and often responsible for more engine damage than elevated boost air pressure .
Exhaust gas is always going to be at a higher temperature than post turbo inlet air even without an intercooler . If you have poorly designed or undersized exhaust manifolding and a small prehistoric turbocharger turning up the boost does horrible things to exhaust gas temperature and pressure . The pressure alone can be 3 to 4 times what inlet manifold pressure is and who knows at what searing temperatures .
The fourth is that elevated exhaust gas pressure , AKA turbine inlet pressure - TIP , creates massive reversion conditions in the head in the valves overlap phase . The result is charge (inlet air) pollution and preheating and a recipe for detonation .
The fifth is that turbo engines generate more heat and things have to be done to reject this extra heat from the water/oil/optionally inlet air .
Really the EA82T is a dinosaur end of story . Ultra low CR/woeful exhaust manifold/small low tech bush bearing turbocharger/agricultural engine management .
If you want one to work acceptably you need a fresh engine to start with .
If you want higher power than factory you have to make it breathe as well as possible meaning better manifolds and if possible cams .
The designer obviously speced the exhaust manifold and turbo to be small so that the engine would spin it up at lowish revs to make some boost fed torque . The low CR means not a lot of off boost torque and advanced ignition timing used to make the best of what little there is .
The early (3 plug ECU system) has a distributor with a vac/pressure signalled actuator plumbed into the throttlebody to work off "ported vacuum" .
This is where the feed is a drilling in the TB just on the upstream side of the throttle plate meaning almost no signal at idle/lots at small throttle openings/very little at wider throttle openings and until the turbo makes positive manifold pressure .
When you take some of the restrictions out of the inlet and exhaust systems the engine can take more ignition advance but the system doesn't give it .
Retarded ignition timing is another cause of elevated EGT as is lean mixtures .
And lastly gas , it wants to burn at higher temperatures than ULP and it seems to be a dryer burn than ULP so harder on the valves pistons and in fact the head/s chambers and structure . Avoidable heat is the enemy and gas will always be a compromise and not a performance driven one .
Ideally if I had to run gas I'd be going to extra trouble to keep fluid temps in check and making sure it never ever ran lean .
High mileage L's already have cooling issues so their radiators need to be good and ways found to drag plenty of air through the core and the engine bay . Really EA82's are not a tolerant engine heat wise and thats as they come from the factory .
Personally I am biased against gas because it tends to "use up" major engine components and fixing them is ultimately more costly than the difference in fuels .
A .
First is that its extra airflow rather than elevated inlet manifold pressure that is the power adder . If you could get the same amount of air into your cylinders at low pressures you'd make as much power as you do with higher manifold pressure .
The second is that boost pressure is a measure of resistance to airflow into an engine . If there was less resistance (restrictions) in the inlet system you can move the same volume of air at lower pressure .
The third is that elevated exhaust manifold pressure and temperature is the devil and often responsible for more engine damage than elevated boost air pressure .
Exhaust gas is always going to be at a higher temperature than post turbo inlet air even without an intercooler . If you have poorly designed or undersized exhaust manifolding and a small prehistoric turbocharger turning up the boost does horrible things to exhaust gas temperature and pressure . The pressure alone can be 3 to 4 times what inlet manifold pressure is and who knows at what searing temperatures .
The fourth is that elevated exhaust gas pressure , AKA turbine inlet pressure - TIP , creates massive reversion conditions in the head in the valves overlap phase . The result is charge (inlet air) pollution and preheating and a recipe for detonation .
The fifth is that turbo engines generate more heat and things have to be done to reject this extra heat from the water/oil/optionally inlet air .
Really the EA82T is a dinosaur end of story . Ultra low CR/woeful exhaust manifold/small low tech bush bearing turbocharger/agricultural engine management .
If you want one to work acceptably you need a fresh engine to start with .
If you want higher power than factory you have to make it breathe as well as possible meaning better manifolds and if possible cams .
The designer obviously speced the exhaust manifold and turbo to be small so that the engine would spin it up at lowish revs to make some boost fed torque . The low CR means not a lot of off boost torque and advanced ignition timing used to make the best of what little there is .
The early (3 plug ECU system) has a distributor with a vac/pressure signalled actuator plumbed into the throttlebody to work off "ported vacuum" .
This is where the feed is a drilling in the TB just on the upstream side of the throttle plate meaning almost no signal at idle/lots at small throttle openings/very little at wider throttle openings and until the turbo makes positive manifold pressure .
When you take some of the restrictions out of the inlet and exhaust systems the engine can take more ignition advance but the system doesn't give it .
Retarded ignition timing is another cause of elevated EGT as is lean mixtures .
And lastly gas , it wants to burn at higher temperatures than ULP and it seems to be a dryer burn than ULP so harder on the valves pistons and in fact the head/s chambers and structure . Avoidable heat is the enemy and gas will always be a compromise and not a performance driven one .
Ideally if I had to run gas I'd be going to extra trouble to keep fluid temps in check and making sure it never ever ran lean .
High mileage L's already have cooling issues so their radiators need to be good and ways found to drag plenty of air through the core and the engine bay . Really EA82's are not a tolerant engine heat wise and thats as they come from the factory .
Personally I am biased against gas because it tends to "use up" major engine components and fixing them is ultimately more costly than the difference in fuels .
A .
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steptoe
- Master Member
- Posts: 11582
- Joined: Thu Oct 06, 2005 10:00 am
- Location: 14 miles outside Gotham City
Good read again as usual Adrian. I see you and agree. Just keeping all things as cool as possible must help but even a cold engine is likely to still have high combustion temps which can cause damage. I am sure that this time the genuine head gaskets will get a retorque after initial warm up without loosen off before. For the first 23000 km I had the no more than 1/4 temp gauge, so will be giving everything another shot. And I can afford to lessen the rich boost mix a little as the richer the mix the hotter it gets with LPG. The redline wetter water stuff sounds interesting too
Just ordered an expresso water pump as per autospeed set up for water injection attempt.
One day I may just stop this dreaming, fiddling and tinkering
Just ordered an expresso water pump as per autospeed set up for water injection attempt.
One day I may just stop this dreaming, fiddling and tinkering
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T'subaru
- Junior Member
- Posts: 733
- Joined: Mon Oct 13, 2008 9:13 am
- Location: T'sunami Coast, Wa. ( usa )
To be honest I didnt bother to retorque my heads as my efforts were all about getting thru the winter and needing it to run asap. Poor excuse but its all i got. Just waiting for a doner car to come up reasonable, no luck yet as ej20t parts cars are pretty rare here. So im driving it easy hoping it holds together and wondering why I dont buy a new subaru and relax..oh yeah, money and the ridiculous amount of miles I put on my cars.
Cheers
Cheers
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discopotato03
- Senior Member
- Posts: 2134
- Joined: Sun Mar 18, 2007 9:29 am
- Location: Sydney
Well you do get a "cold gun" effect with a really cold engine because everything that see's fire absorbs heat ie the piston crowns valve faces and chamber surfaces .
It would be expensive to do but ceramic thermal barrier coatings insulate these things from combustion heat and help keep the heat where it belongs - in the burning gasses .
I had my piston crowns done mainly to make up for the EA82T's lack of piston oil squirters . My engine builder had the exhaust valve faces done because a lot of heat is conducted up their stems and into the head castings via the valve guides . Had I known at the time I'd have had the inlets done as well to try to keep a bit of charge air heat out when they're open .
By keeping things cool I mean to get some longevity into the heads/gaskets/engine cases and cylinders . It can be as simple as running those oversized 76C thermostats .
I don't get the sluggedly cold running because my oil is a synthetic four stroke race bike oil and quite fluid at lowish ambient temps . It makes you're typical mineral 20W50 look like honey but at $16.20/L and thats out of a 44 into my containers it's not for everyone .
A while back one of the fellers at Skylines Australia did a thread on water injection and I'll see if I can find the link .
Cheers A .
It would be expensive to do but ceramic thermal barrier coatings insulate these things from combustion heat and help keep the heat where it belongs - in the burning gasses .
I had my piston crowns done mainly to make up for the EA82T's lack of piston oil squirters . My engine builder had the exhaust valve faces done because a lot of heat is conducted up their stems and into the head castings via the valve guides . Had I known at the time I'd have had the inlets done as well to try to keep a bit of charge air heat out when they're open .
By keeping things cool I mean to get some longevity into the heads/gaskets/engine cases and cylinders . It can be as simple as running those oversized 76C thermostats .
I don't get the sluggedly cold running because my oil is a synthetic four stroke race bike oil and quite fluid at lowish ambient temps . It makes you're typical mineral 20W50 look like honey but at $16.20/L and thats out of a 44 into my containers it's not for everyone .
A while back one of the fellers at Skylines Australia did a thread on water injection and I'll see if I can find the link .
Cheers A .
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discopotato03
- Senior Member
- Posts: 2134
- Joined: Sun Mar 18, 2007 9:29 am
- Location: Sydney
Here it is , start at about post no 33 and have a read .
http://www.skylinesaustralia.com/forums ... tion&st=20
Cheers A .
http://www.skylinesaustralia.com/forums ... tion&st=20
Cheers A .