270deg oil temps w/Redline..should I worry?

[Dick in Falls Church]

Mike-
According to the Redline info, there is zero buildup of hard deposits in three hours at 500 degrees F.

So, if you believe them, why even worry?

 

[unDummy]

Get a real temp gauge. I don't trust stickers even though they claim to be accurate.
It might also be a good time for an oil cooler since the engine is modded.

 

[metroplex]

Keep an eye on your cylinder head temperatures.

My Vic has a CHT reading that I check via an OBD-II scan tool. The CHT is usually a few degrees above the coolant temperature and that's what I go by.

If the heads are way too hot - that can cause problems. But if the oil is hot because of how it "cools" down the engine, then its ok so long as the head isn't extremely hot.

 

[JohnBrowning]

You are developing almost twice the output power at the wheels as in stock trim. You are raceing along at high speeds and high rpm settings. Your oil looks better after 5000 miles of this then most LS1 do in stock trim! I would not sweat it!!! I do not see any thing that looks like lubrication problem at all. I surely could not recomend a non-botique oil that i think would do a bettter job. If you wanted to you could play around with different weights like 10W40, 10W30 15W40.......

Other then nitration and oxidation all looks well. You might ask Molakule if LC would help with those numbers?

 

[sprintman]

As much as I like Motul and use it I'm not sure 300V would be better than Redline. Still 300V is great value for money and has earned it's reputation in racing worldwide over many years. Amsoil 20W50 racing would be another I'd use in your hi-temp application.

 

[MolaKule]

I'm with unDummy on this one. Get a set of real guages and sensors or an IR thermometer. If you use an IR thermometer, always point at the same spots for consistency.

IMO, The oil analysis doesn't show stressed oil. The base polyol esters in Redline don't usually show any stressing until you get to around 500 F, and even then, the antioxidants should suppress any further oxidation. This is why "one" of their antioxidants is moly at 600 ppm.

[ September 17, 2003, 07:22 PM: Message edited by: MolaKule ]

 

[Tyrolkid]

Thanks for all the responses, guys

I was leaning towards not changing anything, and you guys confirmed my decision. Rock on.

 

[sprintman]

Mate your RL 5W40 report convinced me way back that it's 'the go'. Impressive report.

 

[theguru]

The Redline report is great. I would definately stick with it.

 

[jason07-1zzfe]

I wouldn't worry and it is ~7cSt at 280F so you are fine. Actually that vis is for the 40wt race oil (15w40) so the 5w40 is probably a little thinner

I believe from Molakule's summary of an SAE bearing film thickness study it was around 4cSt where you get into the danger zone...but then they probably weren't loading the bearings as much as you are?

Heck you get your analysis from Terry...if he is not worried...you have no reason to be either!

[ September 17, 2003, 12:12 PM: Message edited by: Jason Troxell ]

 

[Scooter]

As stated above, the Redline is a god choice for high temp applications. You might consider upgrading your existing oil cooler. Check out this kit...
http://www.dieselgeek.com/oilcooler.htm

 

[Ken2]

Hot oil has two concerns---deterioration to the oil and thinner viscosity. Also, you're really cooking gaskets and seals.

About every 20°F rise is the same as using one viscosity grade lighter oil. 30 wt. @ 200°F is about the same viscosity as 40 wt. @ 220°F.

With the temperatures you're running, I'd get accurate readings, install a cooler, and if still hot, use a 50 wt. oil.


Ken

 

[SHOZ]

My Taurus SHO has a water/oil Hx that the filter mounts to. At one time I had the incoming water going through an ATX finned cooler then to the Hx. This not only helped out the coolant temp but the oil temp too. I have since gone to a 170F t-stat and removed the cooler.

 

[harrydog]

quote:

---

Originally posted by Ferrari:

quote:

---

Originally posted by harrydog:
I don't think you will find an oil better suited to your circumstances than Redline. I'd be using their 10w40 though.

---

Motul 300V is a racing oil, better than Redline in high-temp, high-stress situations.

---

I don't think so. High temp/high stress situations is where Redline excells. It was designed for those applications. I wouldn't hesitate to use Motul 300V (if it were more readily available here) but I wouldn't say that it's "better than Redline in high-temp, high-stress situations."
I notice that the flashpoint for Motul 300V is 431 deg. F and Redline 10w40 is 495 deg. F.

 

[userfriendly]

Tyrolkid;
What is the RPM of the peak HP? Would the crank HP be about 260 or 2.36 HP/CID?
The reason I'm wondering is because to make 28LBS of boost on a typical turbo street set-up, the exhaust pressure is very likely higher than the boost pressure.
In your case the exhaust back pressure could well be over 35 PSI.
With a sofisticated race set-up, it is possible to get the boost above the exhaust pressure, but even then, not at every RPM.
Your intake manifold pressure is reaching 28 PSI, but is your cylinder pressure and intake manifold pressure equalizing before the intake valve is closing?
Perhaps a little more cam, especially on the intake side, and a little less boost might drop your engine and oil temperatures.
Whadayathink?

 

[Al]

Those numbers agree pretty well with an SAE Technical Paper(2001-01-1073) which indicated oil sump temperatures of 287 F for an 8 cyl V-8 engine at WOT @ 4000 rpm.

It would seem reasonable to use a 40 wt. here bc the viscosity would be around 6.5 cSt vs 5 cSt for a 30 wt oil.

 

[Tyrolkid]

quote:

---

Originally posted by userfriendly:
Tyrolkid;
What is the RPM of the peak HP? Would the crank HP be about 260 or 2.36 HP/CID?

---

Excellent post, Userfriendly!

I know it's

but I'll answer anyways

Peak HP is about 5k rpm. Crank HP would approx. be 260 as you stated.

quote:

---

The reason I'm wondering is because to make 28LBS of boost on a typical turbo street set-up, the exhaust pressure is very likely higher than the boost pressure.

---

It makes 28psi from about 3200-4500rpm, at which point it tapers to about 16lbs at 6500. The turbo is a tiny Ko4, designed for quick spool. The exhaust pressure is probably huge, as the exhaust housing is tiny.

quote:

---

In your case the exhaust back pressure could well be over 35 PSI.
With a sofisticated race set-up, it is possible to get the boost above the exhaust pressure, but even then, not at every RPM.
Your intake manifold pressure is reaching 28 PSI, but is your cylinder pressure and intake manifold pressure equalizing before the intake valve is closing?

---

Ding ding ding, we have a winner! The answer to this question will potentially unlock a lot of power from the VW/Audi 1.8T. These motors require insane amounts of boost to make good power. It has been theorized that it has to do with the cam timing/lift/duration.

quote:

---

Perhaps a little more cam, especially on the intake side, and a little less boost might drop your engine and oil temperatures.
Whadayathink?

---

As 1.8T tuning is still in it's infancy, this is a great idea. I'm actually leaning towards adjustable cam gears as opposed to cams at first. I'd love to give it more intake duration, but finding cam specs are very difficult. As of yet, no one makes an adjustable cam gear for the car(I'm working on one myself). Unfortunately due to the design of the head, I will not be able to adjust the intake and exhaust cams individually...any ideas if simply adjusting cam timing will help

-Mike P

 

[userfriendly]

Al, You seem to know quite a bit about engine oils. Is 287F not a little high for conventional engine oils especially ones with VI improver in them?
I thought that after 250F dino oils go all to heck in a hand bag in a hurry.

Tyrolkid; do you believe this statment?
On a turbo engine you can move the cam(s) around, which means advancing and retarding them in relation to the crank, and change their lobe seperation with out making much difference to the performance (HP) of the engine as long as the
cam(s) are under-sized. (or small like stock ones)

Next question, and I know that this is off-topic, but so what, its relevant,(just like the Jerry Springer show).
If you increase the intake duration of the camshaft with no other phasing changes, you will open the intake valve sooner and close the intake valve later.
If the intake valve begins to open BTDC and before the exhaust valve is closed, as intake valves often do, the exhaust back pressure is 35 PSI, and the intake pressure is 28 PSI, in which direction will the exhaust gasses flow?

260 HP at 5000 rpm is how much torque?
If you could make that much torque at 6500 rpm, how much HP would the engine be producing?
338? Now were getting 3HP per cid
TBC...

[ September 26, 2003, 07:17 AM: Message edited by: userfriendly ]

 

[theguru]

Tyrolkid,

Some discussion here is abt you exhaust pressure etc. whilst you haven't metioned the exhaust system as such, is it standard or have you upgraded it? With a turbo it is important to have as big an exhaust as you can so as to lower the pressure on the exhaust side. My sons car has a 3" system from the the turbo back, including a modified dump-pipe to stop the mixing of turbo/ exhaust gases. When you increase your boost the pressure in the exhasut will not only limit your performance but will also cause the backpressure to overheat exhaust valves etc. This will burn out the valves and crack the exhaust manifold. Already his mainfold glows under high boost. He is running 1.3bar pressure (standard is abt .5bar)on the standard intercooler (pretty small). It has been suggested that extractors are required to fix this problem. Water temperature only rises to 82C from normal of 79C, so water temp is not a great indicator of what's happening.

 

[userfriendly]

Guru;
Your gonna hafta' translate those barometer readings for us North Americans. One bar=14.7 PSI?
Ok, got it.
What do you think of the following?
Until the boost pressure is reduced, the exhaust pressure between the engine and the turbo will likely remain high reguardless of the size of the exhaust tubing and efficiency of the mufflers if so equipped, after the turbo. Reducing the outlet side back pressure may do little to reduce the inlet side exhaust pressure, but will help the efficiency of the turbo.
I'm making this up as I go along.
What about this one?
Popular press "turbo" camshafts generally have less exhaust duration than intake duration.
Even the little ones.
It may be stated by some experts, that the late exhaust valve opening point helps eliminate turbo lag and spool up the turbo faster than conventional exhaust valve timing.
The explanation or at least the one that I have heard, is that in addition to the exhaust pressure blow-down, the exhaust gasses are also pushed out of the cylinder by the piston increasing the exhaust pressuer in the process. (so much for free boost)
Can anyone comment on that theory?
I would think that "free boost" meaning non-parasitic to HP, would come from allowing the exhaust blow down to drive the turbo, then only having the piston push up against an exhaust pressure that is only sightly higher than the intake boost pressure.
Would very high exhaust pressure on the inlet side of the turbo put additional stress on the turbo's thrust bearings?