oil weight selection based on track use.

[supraguru05]

This might seem like a basic question however there is some pretty sad stuff going on here.

alright i have a pretty serious track mk3. it has dual oil coolers running in parallel with a remote spin on filter and a thermostat. i have a rebuilt engine with a new toyota oil pump shimmed. with the oil hot (220-250 DEGF) The oil pressure on straight aways is around 40 while running german castrol.

heres the problem. last event i decided i would look down at my oil pressure gauge in the turns just to see. well i saw the oil pressure drop in the center of the corner to 20 psi and then it recovers in the straights. the pan has two added wings for additional capacity and has orifice style baffles (not trap doors). obviously the root of my problem is the pan which i will fix this winter. i have two weekends left.

Now what i am wondering is what i can do to try to minimize the danger of the low pressure on the bearings. i am not getting a accusump sorry no money or time right now as the races are in a week and then in a month. i am wondering if i can play with the oil weights to make the oil that actually get to the bearings be more effective at handling the loads. i know in rod knock threads you say not to run the higher weight oils. but i think in my case a 40 hot weight oil might give me that little extra help versus the thinner 30 weight.

also the engine is getting rebuilt this winter anyway so i am just basically trying to limp it through these next two races.

 

[jdub]

First of all, you need to do some research on how open hydrodynamic bearings work. I happen to have an article on bearing failures:
http://www.stockcarracing.com/techarticles/1590_engine_bearing_analysis/index.html

What is happening to you is the oil is being sloshed away from the pick-up in the sustained turns. About the only things that is going to prevent that is a Grp A oil pan (designed by Toyota for the track) and/or an accumulator. Sorry, but that's the answer.

Increasing oil viscosity will make little difference...the flow through the bearings is reduced in your case due to sustained "G" in the turns. Increased viscosity will help for a few seconds due to a thicker oil boundary layer, but not long enough to prevent a pressure drop. The reduced flow will cause a decreased oil film thickness and the bearing will touch the journal surface. The high oil temps are not helping.

What you will likely experience is wiping. How severe is going to depend on RPM in the turns during the reduced flow. You'll see it when you pull the motor apart

However, based on your oil temps and since this is a race car, I would look at using Red Line 5W-40. It's the highest ops temp viscosity for the Red Line 40W multigrades. Plus, it's an ester base...it can easily handle the sustained high temps you experience without degrading.

Just to make it clear to those that might read this and think I'm recommending a 40W (because if it's for race, it must be better...right), there is no need to run a 40W in street car with no engine problems.

Since you seem to have your mind made up on the Accusump (that is the solution), I hope you motor lasts 2 more races.

 

[Poodles]

Sounds like he's trying for a quick fix for the rest of the season. As such maybe running more oil?

 

[jdub]

An additional quart just might help

 

[IJ.]

Accumulator

 

[supraguru05]

thanks everyone. Yes i recognize the root problem and the solutions but as of right now i am right on budget and cannot go the extra cost for the accumulater until this winter when my budget resets. damn those budgets lol.

I am going to switch to the higher weight in hopes that for the 1-2 seconds the pressure is down it will give me some head room against wiping.

like i said just trying to limp through the last two races. the engine has some rings sealing issues so i am going to build a whole new motor anyway.

again jdub thanks for the help. youve helped me quite a bit from the start of my cooler system to little things like this.

i however cannot run the redline since i have a small sponsorship by lucas (30%) off so i will be running their oil. thanks .

in the winter i plan on adding trap doors, switching to a inline filter or a canton spin on with a billet mount (the permacool casts i am running now suck) and running a accusump. I also plan on dropping one of the two coolers as they are to much weight up front.

thanks again

 

[IJ.]

An extra Qt or 2 for now then SG!

 

[Feffman]

An Accumsump (http://www.accusump.com/) will likely prove helpful whether you re-design/upgrade the oil pan or not. Helps keep the pressure constant with a piston type pressure back up canister.

As for the oil weight, I just read an article in Race Tech magazine (UK publication) about oil weights. The race engineers from several F1 teams all pretty much noted the same thing. If the oil is running at around 212 degrees Farenheit (about 100 degress Celcius), your oil weight is spot on.

Feff

 

[jdub]

Considering that petro engineers design all oils to viscosity spec at 100 deg C, it's no big surprise

 

[berniek]

If the major concern is oil starvation due to acceleration, you might want to move the oil pickup back to the rear kickup in the pan. I did exactly that. PM me if you want details.

BernieK

thanks everyone. Yes i recognize the root problem and the solutions but as of right now i am right on budget and cannot go the extra cost for the accumulater until this winter when my budget resets. damn those budgets lol.

I am going to switch to the higher weight in hopes that for the 1-2 seconds the pressure is down it will give me some head room against wiping.

like i said just trying to limp through the last two races. the engine has some rings sealing issues so i am going to build a whole new motor anyway.

again jdub thanks for the help. youve helped me quite a bit from the start of my cooler system to little things like this.

i however cannot run the redline since i have a small sponsorship by lucas (30%) off so i will be running their oil. thanks .

in the winter i plan on adding trap doors, switching to a inline filter or a canton spin on with a billet mount (the permacool casts i am running now suck) and running a accusump. I also plan on dropping one of the two coolers as they are to much weight up front.

thanks again

 

[jdub]

Berniek - Based on his 1st post, I think it's due to high G turns on the track.

 

[supraguru05]

well made it through the weekend so far so good. switched to castrol 5w-40 as i didnt have time to get my amsoil order in. pressures still dropped in the turns but they only went to around 25 psi. now my main issue is the blow by which is getting really bad. after talking with some other racers they said it might not be the rings that spinning the engines at 5000+ rpms for 20 minutes creates tons of windage no matter what you do. i am looking at some options to help this, but i think i just will have to get a giant catch can. thats not really a topic for this section just thought i would mention it.

I am switching to amsoil signature series 0w-30, not running one of their filters tho ill stick to purolater.

 

[jdub]

That oil is probably the best Amsoil makes. A heads up, when I gave it a try there was a significant increase in valve train noise.

 

[supraguru05]

That oil is probably the best Amsoil makes. A heads up, when I gave it a try there was a significant increase in valve train noise.

thanks for the heads up i would probably think something was wrong and spend time adjusting the valves and end up wasting time.