What could the problem be? - Page 3

mkiiisupra · 07-08-2008, 11:57 PM

Quote:

Originally Posted by Busted Knuckles

Sidewinder, you can survive for a bit if you switch to 20W/50 oil, and use a bottle of STP with every change. This bumped my idle pressure to 10-15 psi, and has been holding there for a year. I'm planning on an engine rebuild. It will probably happen this winter or next spring.

Please dont do this.... Putting thicker oil in your car is not the answer....

please read the oil link in my signature Busted Knuckles before you advise someone else....

mkiiisupra · 07-09-2008, 01:54 AM

The Following is from jdub over at supramania. Knows alot about oils

A 20W-50 will increase oil pressure and keep the bearings from touching the crank journal/rod end - False
A thicker oil will increase oil pressure in the 7M, but only to a point. The design of the 7M has the oil relief valve set at 63-71 psi...over this oil is simply routed back to the pan. More importantly, the oil cooler valve on the stock filter head operates at 40 psi and you have a controlled "leak" from the oil squirters on a turbo motor. Pressure is resistance to flow...a 20W-50's increase in pressure means that it does not flow as well through the bearings or to the top of the motor. Considering a 20W-50 oil is 3-4 times thicker cold than a 5W-30, it's significant. This means a couple of things:
- On a cold start, you will have restricted oil flow where you need it the most.
- The oil relief valve will cut the flow further by opening at the higher pressure and dumping oil back into the pan.
- It will take longer for the oil to get to the cam shafts...the small diameter hole in the middle does not facilitate flowing high viscosity oil. Since the oil flows from front to rear on the cam shafts, it is going to take the #6 cylinder valves the longest to get the oil flow needed.
- The oil squirters spray pattern on the cylinder walls will degrade with a high viscosity oil...especially cold. It's simple...higher viscosity, lower velocity.
Oil pressure has little to do with the way an open bearing (like rod & main bearings) works. Like I said, these bearings depend on hydrodynamic lubrication to function...saying increased pressure will improve this is a very basic misunderstanding of how the bearings really work. The ONLY time I could see using a 20W-50 from a bearing standpoint is if you've built the motor for it by opening up the bearing clearances to get the flow...you will see some very experienced engine builders do this, mostly on race cars that get re-built every season anyway.

Busted Knuckles · 07-09-2008, 03:41 AM

mkiiisupra, I beg to differ on a few points.

Point 1: 20W50 is a recommended oil for the 7M-GE and 7M-GTE for ambient temperatures above 40 deg F, according to the owner's manual. So, the oil journals, including the cam journals, are sufficient for this viscosity. I live in Atlanta, and we only see temps below 40 for a couple of weeks in the dead of winter.

Point 2: Oil is pushed through the engine by pressure. The higher the pressure, the more oil is being delivered to all parts of the engine, especially to the top of the cylinder head. At idle pressures of 5 psi, less oil makes it to the cams, and more is running through the main bearings due to widened clearances due to wear. A heavier oil will push less through the mains, and force more towards the cams, as monitored by increased oil pressure.

Point 3: Since 20W50 is a recommended oil, you do not have problems within the oil delivery journals of 'choke points' where the oil delivery hole prevents the oil pressure from being delivered. Thus, the oil pressure is the same at the cam bearings as it is at the main bearings.

Point 4: Bearings get most of their protection from film thickness. Higher viscosity oils provide higher film thicknesses than lighter oils. Pure and simple. And as the bearings wear, and clearances widen, that film thickness may prevent a bearing from getting smoked.

I've read link after link from sites like Bob Is The Oil Guy and discussions that link to studies, like Technical Journal: R&D Review of Toyota CRDL

that specifically links light viscosity oils to increased wear in piston rings over higher weight oil specifically because of the lighter oil running off the cylinder walls faster. They also show increased wear in connecting rod bearings, cam bearings, and main journals.

mkiiisupra · 07-09-2008, 04:53 AM

Quote:

Originally Posted by Busted Knuckles

mkiiisupra, I beg to differ on a few points.

Point 1: 20W50 is a recommended oil for the 7M-GE and 7M-GTE for ambient temperatures above 40 deg F, according to the owner's manual. So, the oil journals, including the cam journals, are sufficient for this viscosity. I live in Atlanta, and we only see temps below 40 for a couple of weeks in the dead of winter.

Again the following from jdub over at supramania.

Note that 20W-50 is listed for a 10 to 100+ F temp range...so is a 15W-40 and 20W-40. On the 2nd line a 10W-30, 10W-40, and 10W-50 are listed for 0 to 100+ F temps...a wider temperature range. Also, if you look at the verbiage at the top, the manual shows API grades SF, SF/CC, and SG...all are obsolete API grades...you cannot even buy these oils anymore. The current API grades are SL and SM...these oils represent a quantum leap in formulation improvements over the oils available when the Supra manual was published. Modern oil's at SAE viscosity 0W-20, 5W-20, 0W-30 and 5W-30 easily cover the temp ranges (especially in cold climates) most of us operate the motor at...oils have simply improved that much over the last 20 years. Bottom line: Take the Supra manual oil chart with a grain of salt.

The manual recommends it - False
See above. The manual does not specifically recommend a 20W-50...it's just one of the oils listed that are "approved". It also recommends a 10W-30...an oil that covers a wider temp range. Completely ignores that API SF and SG grades are obsolete.

mkiiisupra · 07-09-2008, 05:04 AM

In addition you do not need oil additives if you buy good oil in the first place...

The supra is a low oil pressure vehicle and you can only increase that so much at a certain point (mentioned above) it kicks the oil back into the pan allowin less to flow into the engine.

Pressure is resistance to flow...a 20W-50's increase in pressure means that it does not flow as well through the bearings or to the top of the motor.

If you would take a moment and read through Motor Oil I think you will have a better understanding

Canuckrz · 07-10-2008, 04:28 AM

Ok then after all the arguing back and fourth is said and done what is the correct oil to use for summer driving? I looked through the maintenance receipts the previous owner had and he was running 5w30.

mkiiisupra · 07-10-2008, 05:13 AM

5w30 or 0w30 would be a good bet.

German castrol 0w30 is good oil can usally be found at autozone

There was no arguement... Just dont like to see people give out innacurate information

But if you yourself had taken the time to read above you would of had a good idea of what oil to use and not have to have it handed to you

Canuckrz · 07-10-2008, 05:24 AM

My dad seems to think that it isn't the rings but a seal in the turbo which is leaking oil and burning it? What do you guys think?

I figure I'm gonna hand it over to Toyota for a day sometime and find out for sure whats going on. No sense buying another turbo or having to do a rebuild if it isn't necessary eh?

mkiiisupra · 07-10-2008, 06:57 AM

Toyota probably wont be much help they dont know anything about turbos and can only tell you to replace it. Need to find a specialty shop in your area that has done work on this car before otherwise you wont get very far

Canuckrz · 07-10-2008, 12:25 PM

So they wouldn't be able to even pinpoint the problem if it is with the turbo? The only turbo shop around my place is two hours away.

07-09-2008, 01:54 AM	#22
mkiiisupra Lexus & 550's Join Date: Sep 2007 Location: Las Vegas, NV Posts: 570 Blog Entries: 1	The Following is from jdub over at supramania. Knows alot about oils A 20W-50 will increase oil pressure and keep the bearings from touching the crank journal/rod end - False A thicker oil will increase oil pressure in the 7M, but only to a point. The design of the 7M has the oil relief valve set at 63-71 psi...over this oil is simply routed back to the pan. More importantly, the oil cooler valve on the stock filter head operates at 40 psi and you have a controlled "leak" from the oil squirters on a turbo motor. Pressure is resistance to flow...a 20W-50's increase in pressure means that it does not flow as well through the bearings or to the top of the motor. Considering a 20W-50 oil is 3-4 times thicker cold than a 5W-30, it's significant. This means a couple of things: - On a cold start, you will have restricted oil flow where you need it the most. - The oil relief valve will cut the flow further by opening at the higher pressure and dumping oil back into the pan. - It will take longer for the oil to get to the cam shafts...the small diameter hole in the middle does not facilitate flowing high viscosity oil. Since the oil flows from front to rear on the cam shafts, it is going to take the #6 cylinder valves the longest to get the oil flow needed. - The oil squirters spray pattern on the cylinder walls will degrade with a high viscosity oil...especially cold. It's simple...higher viscosity, lower velocity. Oil pressure has little to do with the way an open bearing (like rod & main bearings) works. Like I said, these bearings depend on hydrodynamic lubrication to function...saying increased pressure will improve this is a very basic misunderstanding of how the bearings really work. The ONLY time I could see using a 20W-50 from a bearing standpoint is if you've built the motor for it by opening up the bearing clearances to get the flow...you will see some very experienced engine builders do this, mostly on race cars that get re-built every season anyway. __________________ 1990 Toyota Supra Turbo A/T ------------------------------------------------ Questions about oil? take a look http://www.supramania.com/aehaas/

07-09-2008, 05:04 AM	#25
mkiiisupra Lexus & 550's Join Date: Sep 2007 Location: Las Vegas, NV Posts: 570 Blog Entries: 1	In addition you do not need oil additives if you buy good oil in the first place... The supra is a low oil pressure vehicle and you can only increase that so much at a certain point (mentioned above) it kicks the oil back into the pan allowin less to flow into the engine. Pressure is resistance to flow...a 20W-50's increase in pressure means that it does not flow as well through the bearings or to the top of the motor. If you would take a moment and read through Motor Oil I think you will have a better understanding __________________ 1990 Toyota Supra Turbo A/T ------------------------------------------------ Questions about oil? take a look http://www.supramania.com/aehaas/

07-10-2008, 05:13 AM	#27
mkiiisupra Lexus & 550's Join Date: Sep 2007 Location: Las Vegas, NV Posts: 570 Blog Entries: 1	5w30 or 0w30 would be a good bet. German castrol 0w30 is good oil can usally be found at autozone There was no arguement... Just dont like to see people give out innacurate information But if you yourself had taken the time to read above you would of had a good idea of what oil to use and not have to have it handed to you __________________ 1990 Toyota Supra Turbo A/T ------------------------------------------------ Questions about oil? take a look http://www.supramania.com/aehaas/

07-10-2008, 06:57 AM	#29
mkiiisupra Lexus & 550's Join Date: Sep 2007 Location: Las Vegas, NV Posts: 570 Blog Entries: 1	Toyota probably wont be much help they dont know anything about turbos and can only tell you to replace it. Need to find a specialty shop in your area that has done work on this car before otherwise you wont get very far __________________ 1990 Toyota Supra Turbo A/T ------------------------------------------------ Questions about oil? take a look http://www.supramania.com/aehaas/

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
ABS Problem?	rasclaat_98	MKIII Supra	6	12-13-2010 09:53 PM
speed sensor problem	nadircicek	Non-Generation Specific Questions	8	10-09-2009 05:58 PM
found the problem	brs86supra	MKIII Supra	0	05-02-2006 03:42 PM
Boost Problem, I Guess	nonstop213	MKIII Supra	0	02-23-2006 07:32 PM
tsp problem for na t supra	jdlee123	MKIV Supra	0	09-02-2005 06:01 PM

07-09-2008, 03:41 AM	#23
Busted Knuckles 12psi boost Join Date: Dec 2007 Location: Atlanta Posts: 300	mkiiisupra, I beg to differ on a few points. Point 1: 20W50 is a recommended oil for the 7M-GE and 7M-GTE for ambient temperatures above 40 deg F, according to the owner's manual. So, the oil journals, including the cam journals, are sufficient for this viscosity. I live in Atlanta, and we only see temps below 40 for a couple of weeks in the dead of winter. Point 2: Oil is pushed through the engine by pressure. The higher the pressure, the more oil is being delivered to all parts of the engine, especially to the top of the cylinder head. At idle pressures of 5 psi, less oil makes it to the cams, and more is running through the main bearings due to widened clearances due to wear. A heavier oil will push less through the mains, and force more towards the cams, as monitored by increased oil pressure. Point 3: Since 20W50 is a recommended oil, you do not have problems within the oil delivery journals of 'choke points' where the oil delivery hole prevents the oil pressure from being delivered. Thus, the oil pressure is the same at the cam bearings as it is at the main bearings. Point 4: Bearings get most of their protection from film thickness. Higher viscosity oils provide higher film thicknesses than lighter oils. Pure and simple. And as the bearings wear, and clearances widen, that film thickness may prevent a bearing from getting smoked. I've read link after link from sites like Bob Is The Oil Guy and discussions that link to studies, like Technical Journal: R&D Review of Toyota CRDL that specifically links light viscosity oils to increased wear in piston rings over higher weight oil specifically because of the lighter oil running off the cylinder walls faster. They also show increased wear in connecting rod bearings, cam bearings, and main journals.

07-10-2008, 04:28 AM	#26
Canuckrz Stock Join Date: Jul 2008 Location: Canada, NS Posts: 28	Ok then after all the arguing back and fourth is said and done what is the correct oil to use for summer driving? I looked through the maintenance receipts the previous owner had and he was running 5w30.

07-10-2008, 05:24 AM	#28
Canuckrz Stock Join Date: Jul 2008 Location: Canada, NS Posts: 28	My dad seems to think that it isn't the rings but a seal in the turbo which is leaking oil and burning it? What do you guys think? I figure I'm gonna hand it over to Toyota for a day sometime and find out for sure whats going on. No sense buying another turbo or having to do a rebuild if it isn't necessary eh?

07-10-2008, 12:25 PM	#30
Canuckrz Stock Join Date: Jul 2008 Location: Canada, NS Posts: 28	So they wouldn't be able to even pinpoint the problem if it is with the turbo? The only turbo shop around my place is two hours away.