Here's what my engine temps look like at 55 and 80 MPH. I've begun to add engine temps for ambient temperatures in the upper 90s, low 100s (F) now that it's started to get hot around here. You can pretty much ignore the part of the curve that falls below 45 F ambient on all of the 55 MPH curves since I don't have any data in that region for now (have to wait until winter).

UPDATE 070921: Added data for 5W-20 oil in addition to the 5W-30 and 20W-50 oils in the first plot, and affect on coolant temperatures in the second plot. Unfortunately (for this project), the weather started cooling off so I don't have enough temp data in the +110F region for the 5W-20 oil. I suspect that its curve would cross over the 5W-30 curve somewhere above 210F (near the cross-over point of the 5W-30 and 20W-50 curves). But until I get that data, this is speculation. Also, I'm still gathering data for ambient temperatures below 50F for 5W-20 oil --- so ignore the upturn in its curve (and the upturn in the 20W-50 curve for that matter) below 60F for now. I may have to separate the curves into another graph --- the data points really make these plots busy LOL.

Recording Conditions:

* Vehicle at speed for 10 mins or more.
* Level road
* Wind speed below 27 mph
* Relative Humidity 20 or below
* Engine oil always kept near full mark
* Tire Pressures at 35 psi cold
* RB A/C and oil cooler screens
* Stock NA engine

Cowardly Disclaimer:

* Don't know the accuracy of the Nordskog Digital Street series gauges
* Ambient temperature read from the OEM center console LED display ---
don't know how accurate that is either
* Wind speed is a guesstimation --- I live in the desert, so if you see
the creosote bushes bending in the wind, it's probably below 27 mph.
If you see the creosote bushes bending in the wind AND you're getting
sand-blasted AND you have to dodge tumbleweeds the size of your car,
it's above 27 mph.
* And finally, the behavior of my engine may not be representative of the
NA RENESIS engine. Any similarity between my RENESIS and other
RENESISes, whether fictitious or real, is purely coincidental --- so there.



Engine Oil Temps:
Oil Temps at 80 MPH for 5W-20, 5W-30, and 20W-50 viscosity oils. Extrapolating the curves in the higher ambient temp region, the more viscous oil will run a little cooler. You'll probably benefit using a higher viscosity oil if your driving conditions constanly keeps your oil temperature above approximately 210 F.





Affect of Oil Vicosity on Coolant Temperture:
Using 5W-20 or 5W-30 viscosity oils affect the engine coolant temperature identically (taking into account the gauge error). Seems to be some benefit (lower coolant temperatures) using a higher viscosity oil at the higher ambient temperatures (or higher loading conditions).





Engine Oil Temps:
Oil temperatures at constant velocities of 55 and 80 MPH





Engine Coolant Temps:
Engine coolant temperature plot at 55 and 80 MPH





Engine Temps at 80 MPH:
Engine oil and coolant temperature plot at constant velocity of 80 MPH





Engine Temps at 55 MPH:
Engine oil and coolant temperature plot at 55 MPH

 

Interesting post, I'm putting in oil temp, water temp and oil gauges in the immediate future to keep an eye on my temps.

 

I can see why the RX-8 has 2 oil coolers. That oil temp max is about 20 degrees higher than my RX-7 runs. To be fair, however, I installed gauges in the RX-7 over the Winter and have not stressed the engine yet in hot weather. The factory manual for the RX-8 essentially specs the oil temp at 100 degrees (C) [212 degrees (F)], so you're well within spec.

 

There are some aftermarket oil coolers for this car. but I wonder how do they fit (is it perfect fit?) and how does it perform? (compare to stock)

Dunno, never heard of anyone that has an aftermarket one.

 

Yeah, but wait til the heat of summer rolls around ... it hasn't hit 100+ F here yet Extrapolating the oil temp curve, 100F ambient will give me around 210F oil temp at 80 MPH

 

What do the colored diamonds represent?

 

good post man--I have done a good bit of looking at engine temps over the past year or so. on the track and on the street. Biggest thing for me was switching from 5/20 oil to 5/30 because with the 20wgt the engine could not mantain factory recommended oil pressures. AND on the track i now run a 10/40. All synthetic---they DO run cooler.
The 2nd thing that became apparent was the lack of good airflow through the radiator and the oil coolers. Get the fan turned on and your steet coolant temps will never see 200 (within reason of course!) Oil temps--thats another story.
Oil needs to be at the 180-190 mark. Even though there is a lot of discussion concerning oil temps (many people on the track in the 8 and other type cars will go over 250F) I dont like to go over 230F even with syn in.
Therre are a lot of things that you can do to help with temps. If you are running screens BE SURE that the screens are actually touching the coolers---if they are not --then the airflow will be restricted. I dont run them anymore.
One you probably havent heard about---i recently cut the rotor symbol out of my front air dam--just added a support where it used to be---I cant prove it--but I swear my temp gauge runs about 5 degrees cooler now during in town--non congested driving. I really think it blocks more air movement--or causes some type of turbulance --i dont know--but during certain times the car is a LITTLE cooler. People will probably roll their eyes about this. Dont care i like the way it looks also.
keep up the good monitoring---add oil pressures and rpm observed during those times
olddragger

 

The blue diamonds are the coolant data, the yellow crosses are the oil temp data.
The curves are just Bezier curve-fits to better visualize the data. I updated the plot ... should be a little clearer.

Edit: least-squares fit now

 

Yeah, I read that post of yours ... quite an interesting mod. You're probably right in that you're getting a little better cooling since you've decreased the frontal area of that support --- I think

 

Going off topic, but how do the Nordskog gauges look in the dash? Do you have any pics?

 

The pics are buried in the Racing Beat Gauge Pod Update thread ... https://www.rx8club.com/showpost.php...&postcount=186

 

Results look pretty close to mine.

For some reason my car seems most peppy at 200 oil and 200 h2o. Could be just me though.

 

Added a little data for 55 MPH and also added plots for engine oil temps at 55 MPH and 80 MPH; also engine coolant temps at those same speeds. Updates are in the first post of this thread. I'm constantly gathering data, so stay tuned

 

I added some engine temps for ambient temperatures in the high 90s, low 100s (F) --- the plots in the first post reflect the changes. More to come ...

 

very nice. dont know how i just found it..

i would love to see the same tests without the rb screens...

food for thought..


beers

 

wow - how did I miss this .....
Well done - very interesting .

 

it would be really cool if vacumn readings were added also. I wonder????
This summer I plan on installing a oem header heat shield (not wrapping it), installing a heat shield on the intake and wrapping the airbox. I have the revi and cai. I also wonder if the coils could be mounted on the airbox. Possibily relocate the battery(have you seen how the bottom of the air box and the battery box blocks the airflow from the fans?).
Sorry for the thread hyjack--really good info man--keep it coming
olddragger

 

You are going to incur the wrath of the "experts"---what you say can't happen!
(of course ,like you I know it does)

 

very cool info! I've been thinking about this a lot recently since I forsee plenty of 100+ degree days here while sitting in traffic on the fwy.

 

it looks like your thermostat is working ok, not much else to glean from that data

I never realized that the front bumper rotary symbol had a direct affect on thermostat operation, imagine that ...

 

Very interesting graphs. I like to see two more things at some point.................The oil temp difference with the RB screens and the H2O temps with the Mazsports cooling fan mod since I just installed it this evening.

 

Yes, I agree ... it's always good to have information like that.

Thanks heaps elf!

 

good point,,

i would be happy to lend my mazsport cooling mod if you what to test elf. the greater good..

beers

 

do you think the RB screens could be blocking some airflow?

 

there have been a couple of ideas on this.. i have a set of hymee screens i have not put on yet..

beers