Track Time Limited due to High CHT

[DrZed]

Which Setrab oil cooler do you have on the car currently?

Whelp… got my gauges in… still at drawing board…

Ran pittrace. ~80f and sunny. Running 305mm heat cycled RS4s and short shifting at 6500. Things would stabilize after about 10 minutes…

Cht 225
Ect 210
Oil 250

Pushing any harder would take temps even higher. That last 500rpm REALLY generates some heat.

Guess I’ll box in the radiator seven more than I have, customize the fan shroud, and start looking at even bigger oil coolers!

Another interesting data point is CHT to ect delta would range from 5-25F.

Matt, maybe you mentioned this elsewhere. How do you know specifically your oil temp, or are you estimating from the colour gradients?

Sponsored

 

[NeverSatisfied]

Matt, maybe you mentioned this elsewhere. How do you know specifically your oil temp, or are you estimating from the colour gradients?

I'm running aftermarket gauges now for ECT, Oil Temp and Oil pressure.

 

[Scootsmcgreggor]

I have a 6 series 25 row. And I have it 1/8” spaced off the condenser. I used it because I had it leftover from a turbo Miata.

Looking at Pegasus's site, the chart recommends a 40 row 6 series for the 450-550hp range. Guess I'm undersized currently.

And Ford Performance says that is way undersized still. They spec'd the FP350S with the 960. The hit to the wallet hurt, but I'm very glad I went with the 948. I can still hit 260*F even with a fully ducted 948 (and radiator). If you've gotta do it again anyways I'd seriously consider doing a 948.

 

[Ewheels]

I'm really thinking about making some rear ducting of sorts.
I've seen one guy do it on an S550, he moved the coolant overflow to the battery location and then the battery to the trunk. Still would have to deal with the intake tube but I'm hoping some rear ducting is better than none.

 

[NeverSatisfied]

And Ford Performance says that is way undersized still. They spec'd the FP350S with the 960. The hit to the wallet hurt, but I'm very glad I went with the 948. I can still hit 260*F even with a fully ducted 948 (and radiator). If you've gotta do it again anyways I'd seriously consider doing a 948.

Good to know.... Guess I'll take the nose off for the 27th time and see what I can fit in there.

 

[67Fast_V]

Worked on the track temp issues this weekend also. I went with the Watson racing radiator closeout duct work and race louvers in the hood. The Watson piece is real nice and should work great, only complaint I would have is they are really no instructions other than several cad images of it assembled. It was difficult to figure out the best order of operations. I ended up fully assembling it out of the car and installed it in one piece attached to the radiator, to do this means taking a lot of the front end apart. Bumper cover, headlights, upper support that hood bumper and top of radiator, and the radiator with fan shroud. I looked at just building the piece in the car and I believe it could have been done with just pulling the bumper cover, but I could not convince myself that I was not going to have some unforeseen issue.

It will be a few weeks till I can test this on track, but I am hopeful that it will do the trick

Looks interesting. Thanks for sharing. Questions: How are you going to seal the front or fwd region of the panels against the nose/bumper cover? Is the engine inlet (rubber boot on driver's side) isolated from the rest of the supply cavity .ie. has its own dedicated supply? How did you seal that? And are you able to seal the top radiator cover opening where the plastic OEM cover goes over? Thanks.

 

[67Fast_V]

Interested to see what you think about the kit. I did an art project today as well to see if it helps

Nice carving and fab. That should help for sure. Give you ~5 degs F or so.

Thoughts on your other post from the Pitt race experience...

Those temps are not bad. 250F oil is great. 225 CHT and 215F ECT are good too. The question would be ... if you went for the last 500 rpm and ran as hard as possible, where do you think you would land for temps? My goal is <235F CHT and <275F oil.

Also, curious where did you install the ECT sensor? Looks like it matches the delta the OEM has calculated (15F measured delta for you vs. 13-14 calc delta by the OEM) at high heat load condition. You mentioned at one point this delta was 25F, what condition was that? Thanks.

 

[67Fast_V]

I'm really thinking about making some rear ducting of sorts.
I've seen one guy do it on an S550, he moved the coolant overflow to the battery location and then the battery to the trunk. Still would have to deal with the intake tube but I'm hoping some rear ducting is better than none.

Hi Ewheels - I think your best bet would be to add the side hood louvers, giving yourself more exit area. That's your biggest gainer. Although there is some blockage as the air moves around all the engine bay obstacles to get out, it's not much. Just my two cents and the results of various calculations on the system. I'm sure you don't want to pull the hood and start cutting again, so I get it.

Background: Since it appears that you have a mostly wide open grille (please correct me if I'm wrong), the engine bay exit area is super important. Also if you gut the fan shroud like Forum member Never did, then that will help you as well. However radiator perimeter sealing will have a secondary influence for you. Still help, but not nearly like w/ a stock grille.

Also I really like the looks of your car. Sharp color and contrast... I like it much better than my red.

 

[NeverSatisfied]

Nice carving and fab. That should help for sure. Give you ~5 degs F or so.

Thoughts on your other post from the Pitt race experience...

Those temps are not bad. 250F oil is great. 225 CHT and 215F ECT are good too. The question would be ... if you went for the last 500 rpm and ran as hard as possible, where do you think you would land for temps? My goal is <235F CHT and <275F oil.

Also, curious where did you install the ECT sensor? Looks like it matches the delta the OEM has calculated (15F measured delta for you vs. 13-14 calc delta by the OEM) at high heat load condition. You mentioned at one point this delta was 25F, what condition was that? Thanks.

I'm on the fence on how much higher I want to push the temps. 235F CHT seems to be the magic number where if you linger at that temp it clicks the calculated oil temp to "warm" and starts to pull timing until you get CHT below 235.

I probably should have just beat on it as hard as I could for science with the aux gauges to see what happens. I got concerned when I started seeing 210 ECT not really knowing where the "safe zone" is.

There's a 3/4" npt plug in the block by the driver's side engine mount that is easily accessed. I managed to do a quick change of that plug to a reducer with the sensor installed and only spilled a small amount of coolant in the process.

 

[67Fast_V]

I'm on the fence on how much higher I want to push the temps. 235F CHT seems to be the magic number where if you linger at that temp it clicks the calculated oil temp to "warm" and starts to pull timing until you get CHT below 235.

I probably should have just beat on it as hard as I could for science with the aux gauges to see what happens. I got concerned when I started seeing 210 ECT not really knowing where the "safe zone" is.

There's a 3/4" npt plug in the block by the driver's side engine mount that is easily accessed. I managed to do a quick change of that plug to a reducer with the sensor installed and only spilled a small amount of coolant in the process.

Thanks , I will check out that location. Definitely going to get solid reliable measurement at that location. From your data, it appears that the OEM calc for ECT is reasonable ... and taking a leap, maybe their oil temp calc is also reasonable.

The <235F CHT target came from my previous experience. All engines are different, but my reference is my previous car '17 C7Z M7 Z07 package. Ran ECT 223F-227F consistently for 20-30 min HPDE sessions. FL hot ambient conditions. Only used 3rd gear and up cus using 2nd caused 235-245F ECT's. GM measures ECT at engine exit, upstream of the thermostat. Alumimum block and heads. Same/similar as the coyote. So mid block ave temp was likely 215F ish. So adding 15 degs to get CHT eqv at 230F. Figured <235F CHT would be a reasonable goal.

Also note that my C7Z oils temps where in the 272-278F range. Totally normal and within Mobil 1 syn capability. GM oil recommendations for track use was 15W-50.

There is no question that lower temps are better, but no free lunches here. Everything has a cost. Hate that .

 

[nbjeeptj]

On the Watson setup questions, the air intake gets supply from the section on the drivers side, all the air that enters thru the grill has to go either in the intake or thru the radiator. The seal on top of the radiator seals it to the plastic cap. The seal that comes with the kit is a real nice automotive style seal that seams to do a good job. The sides and the bottom of the Watson also get that same seal. The way it works in the grill side is unclear what they wanted me to do since ther were no instructions but the passenger side vertical piece and the rounded top piece got more of that same seal. The bottom piece is rounded and fits in so tight that the seal would not fit. And the drivers side is sealed on the other side of the air intake by the factory piece.
The square section on the passenger side that has all the air funneled into it, looks to be set up with mounting holes, that look like it for a setrab oil cooler to just bolt straight in. I have emailed Watson to see if that is true can they give me the model number they designed this for. There are also holes with supplied grommets for oil lines to go out kinda under the air intake, which would put them close to the factory water lines for the oil cooler. If I can figure out the right oil cooler my plan is to get a 2014 bottom radiator hose without the oil cooler lines on it and delete the factory water to oil cooler and just have the big air to oil cooler in that square on the passenger side. As this comes together I will report back what I find.

 

[67Fast_V]

Gotcha. Thanks for the clarification and the extra pics. I'll be curious how they intend to seal the vertical panels against the back side of the grill. It has a crazy shape to it.

Just one other thing. The crash bar is a leak source. Look at it closely. Leaks air through the holes and out the ends, so you might want to think about capping the ends. It's 4-5 in^2 from memory. Also the rubber boot for the engine air inlet doesn't seal well around the grille assembly receptacle. Take a look at that as well. Big gaps around perimeter. And also notice the boot corner ear (right side of your pic, upper left corner of the boot) is folded over. When you re-install the bumper/grille cover assembly, you want to make sure that boot corner ear is straighten and goes over the receptacle attached to the back side of the grille. Hard to explain.

Just take a look and you will figure it out. FYI ... I took several pieces of blue tape to hold it back (straighten it), and then reached in on the back side to remove the tape after the grille assembly was installed. And then I borescoped to make sure it was positioned/sealed properly.

The left side boot has same issue (folded over corner, at least mine did), but not sure if the Watson kit eliminates that or what. As I mention in previous post, there are a lot of sneaky leaks in this system. So take a close look and you will see them.

 

[nbjeeptj]

Are you talking about the boot in this picture? If so wander if I can position it by pulling air box and reaching in there. Probably going for one track day before I pull bumper cover again to put in oil cooler.

 

[Scootsmcgreggor]

Also I’m not sure that sealing a boxed radiator to the bumper is very critical since the primary purpose of ducting is to straighten out the airflow through the rad, which 6+” of ducting will do anyways. Sealing to the rad and oil coolers yes, to the bumper no.

 

[67Fast_V]

Are you talking about the boot in this picture? If so wander if I can position it by pulling air box and reaching in there. Probably going for one track day before I pull bumper cover again to put in oil cooler.

Yes, that's the boot. You can't reach that corner of the boot with your hand (at least I couldn't) but you might be able to stick a hook in there and pull it up after the grill is installed. Haven't tried it that way. As mentioned, I just used the tape w/ the edge of the tape located where I could grab it to remove.

@Scoot, sealing is the key. That's the benefit. Get as much of the air that comes through the grill to actually go through the radiator and not by-pass it. So if there is an opening somewhere in the system (whether it's the bumper holes, an open seal, a gap, etc.), the flow will go through that opening and less through the radiator.

A quick illustration. Say you have no leaks and have 10 lbm/s (pps) of air that comes through the grille. You will have 10 pps go through the radiator. Now If you have a leak the same size as the radiator effective area, then the flow through the grill will be say 12 pps (yes, draws more air through the grille) but only 6 pps goes through the radiator and 6 pps through the leak. That would be a 40% reduction in radiator flow. These are just reference numbers, not actual. Hope this helps.

You might ask ... how do I know this. Well I have a airflow model that calculates the flow distribution within this system. So looking at leaks, fan shroud mods, hood vents/louvers, etc., I can estimate improvements (changes in radiator flow) with reasonable accuracy. Now the benefit in heat transfer is much more challenging, although I do have a heat transfer model as well. But the track data/experience is the real key. All calc's need to be proven out on the track. The physics and conditions are just too complicated for me to calculate CHT accurately.

Now why did I create such a model(s)??? Read the 1st post. I was totally clueless and shocked after my 1st track event with this car. Overheated in ~3 mins. So I started asking questions to the Forum and got some education thanks to all the Forum members. And since that 1st post, took some time to get my pencil, caliper, and calculator out to add to the learning process. Cheers

Sponsored