IRS, sure gets hot

[9746Cobra]

Melted my Maximum Motorsports urethane (Prothane?) differential bushings at Daytona.

Had some extra clunk on tip in, found play at the melted bushings. MM offered to replace them when I sent these back, but instead I installed an extra washer on each side to take up the new space. Worked fine.

I had the diff oil (motorcraft 75w-140 full synth) at the proper level, but some still got forced out from the axle seals and vent tube. Not much, but some. I cleaned it up and no more has leaked out. It was just caused by the heat and pressure.

I know of another Cobra that lost lots of fluid at Sebring. I know this is nothing new, but I thought you guys buying/making diff coolers need them because you were hard core OT'ers. And maybe you are, but even one OT event involving high speeds in an IRS Cobra requires top quality diff oil, alluminum bushings that won't melt, and preferably, a diff cooler.

Just thought I'd post my experiences.
9746C

 

[Venomous01]

I read up a lot about how hot the IRS can get when open tracking, specifically the differential so I did a few things to combat it:

1. Had the Maximum Motorsports Rear Differential Cooler kit installed/Had Billetflow make me a custom IRS brace to have the best of both worlds.
2. DEI Thermal wrapped the exhaust.
3. Painted the exhaust with black thermal paint from DEI

I have yet to install my oil temp gauge to see where my diff temps are put plan on having it installed soon.

 

[BlackBolt9]

3. Painted the exhaust with black thermal paint from DEI

Just curious but how will BLACK paint help REDUCE heat?:dw:

 

[Venomous01]

Just curious but how will BLACK paint help REDUCE heat?:dw:

According to DEI it's a thermal coating that insolates the heat. The coating goes on the outside of the wrap and on the piping if you like, to help reduce the dissapating heat generated by the exhaust.

As you know a main factor in a hot IRS is due to the fact that the exhaust runs beneath the IRS. Heat rises and cooks the IRS, bushing, differential and sometimes if your lucky the rear seats as some unfortunate members have found out and posted (not me).

 

[ac427cobra]

A Cobra IRS will get hot when driven on track. How hot? It depends on how hard you're driving the car and what kind of gears you have. The lower the gear (bigger number) the more heat will be generated. The higher the speeds and the higher the ambient temps, the hotter it will run!

People have asked me why I don't offer a Delrin front diff bushing to reduce the noise the aluminum makes and it's for this exact reason I only make aluminum and will not make a Delrin.

Unless you're a novice to intermediate driver running short sessions in cool temps with stock gears, you really do need a diff cooler.

FWIW

:thumbsup::coolman::beer:

 

[BlackStripes]

I think it depends on how much your rear tires grab...

I change ALL my fluids once a year and my exhaust is like 3 feet from the diff

So far no problems.... i really think it 1000 times before adding weight in my car.

 

[Cobra-R]

The diff cooler on my 00R is triggered to come on at about 220 degrees. Less than 45 minutes on the interstate triggers the pump to kick on.

Tried to get by cheap on my stock hp 01 cobra and cooked the diff at Hallett the first weekend out.

Brian

 

[BlackBolt9]

According to DEI it's a thermal coating that insolates the heat. The coating goes on the outside of the wrap and on the piping if you like, to help reduce the dissapating heat generated by the exhaust.

As you know a main factor in a hot IRS is due to the fact that the exhaust runs beneath the IRS. Heat rises and cooks the IRS, bushing, differential and sometimes if your lucky the rear seats as some unfortunate members have found out and posted (not me).

I don't like the sound of it either way. Black absorbs heat. If the coating, regardless of color, resists the transfer of heat (i.e. keeping heat outside by not letting it through) then how will the heat created by the gears (friction, etc.) escape through the case and into the atmosphere? The case is made of aluminum not only for weight but to allow heat to escape from the diff. IMO this coating is negating that effect and you are simply making up for it with the diff cooler. The exhaust heat may not be getting in which I suppose makes it easier on your diff cooler but I can't believe it is really doing much since the cooler is sized to work with out that coating.

I guess the real question is what creates more heat in the diff, exhaust temp or mechanical heat generation? (internal vs. external heat sources)

 

[Lumpydogs]

I cooked my stock front diff bushings :fm: They were so bad that I literally had a 1/4" space between the bushing material and the diff surface. The diff was clunking something fierce every shift :bash: So, I replaced the cooked bushings with aluminum this winter. Can't wait to test drive in spring

p.s. running 4.10 gears on IRS cobra. Drive line clunking got bad after second event and continued to get worse each event after that.

 

[Venomous01]

I don't like the sound of it either way. Black absorbs heat. If the coating, regardless of color, resists the transfer of heat (i.e. keeping heat outside by not letting it through) then how will the heat created by the gears (friction, etc.) escape through the case and into the atmosphere? The case is made of aluminum not only for weight but to allow heat to escape from the diff. IMO this coating is negating that effect and you are simply making up for it with the diff cooler. The exhaust heat may not be getting in which I suppose makes it easier on your diff cooler but I can't believe it is really doing much since the cooler is sized to work with out that coating.

I guess the real question is what creates more heat in the diff, exhaust temp or mechanical heat generation? (internal vs. external heat sources)

The differential wasn't painted black, the exhaust was. DEI says with this wrap and coating less heat is dissepated out of the exhaust and less heat is allowed in.

I will say this from experience... before the coating and wrap the diff cooler would go on sooner and stay on longer. After the wrap and coating the cooler doesn't go on as much and only goes on for a short period of time before the temp is brought back down to an optimal level.

Essentially I think the diff cooler works MUCH better now. I'm very happy with the products performance. When I get the differential oil temop gauge installed I'll have even more insight into those temps, but right now I am pleased with the diff cooler, coating and wrap. All great components to reducing IRS/Differential temps.

:beer:

 

[Venomous01]

I guess the real question is what creates more heat in the diff, exhaust temp or mechanical heat generation? (internal vs. external heat sources)

The answer is both.

The diff creates it's own heat for a number of reasons internally... (gear ratio, friction, less volume then a solid to dissepate the heat).

On top of that the exhaust being routed underneath the exhaust doesn't help. The pipes get hot and if your exhaust doesn't have enough clearance from the diff it can essentially cook your diff like a pan on a stove.

The two combined can lead to excessive diff oil temps. So in my case the diff cooler addresses the internal heat and the wrap and coating addresses the exhaust heat.

 

[BlackBolt9]

The differential wasn't painted black, the exhaust was. DEI says with this wrap and coating less heat is dissepated out of the exhaust and less heat is allowed in.

I will say this from experience... before the coating and wrap the diff cooler would go on sooner and stay on longer. After the wrap and coating the cooler doesn't go on as much and only goes on for a short period of time before the temp is brought back down to an optimal level.

Essentially I think the diff cooler works MUCH better now. I'm very happy with the products performance. When I get the differential oil temop gauge installed I'll have even more insight into those temps, but right now I am pleased with the diff cooler, coating and wrap. All great components to reducing IRS/Differential temps.

:beer:

Got ya, I got it mixed in my head somehow (not sure how since you have it written clear as day:dw. I see where coating the exhaust will help:thumbsup:

The only thing I have heard and it was being discussed about headers not exhaust pipe (not sure it makes a difference) was that the wrap/coating can often cause premature corrosion due to their ability to absorb moisture and hold it against the metal. And chemical reactions occur quicker at elevated temperatures as well. Not saying you will have that problem since I don't know anything about their products but it might be something to keep an eye on.

The answer is both.

The diff creates it's own heat for a number of reasons internally... (gear ratio, friction, less volume then a solid to dissepate the heat).

On top of that the exhaust being routed underneath the exhaust doesn't help. The pipes get hot and if your exhaust doesn't have enough clearance from the diff it can essentially cook your diff like a pan on a stove.

The two combined can lead to excessive diff oil temps. So in my case the diff cooler addresses the internal heat and the wrap and coating addresses the exhaust heat.

I realize its both, I was more wondering which one creates the majority of heat or if they have pretty equal stakes in the final temp.

 

[Venomous01]

Got ya, I got it mixed in my head somehow (not sure how since you have it written clear as day:dw. I see where coating the exhaust will help:thumbsup:

The only thing I have heard and it was being discussed about headers not exhaust pipe (not sure it makes a difference) was that the wrap/coating can often cause premature corrosion due to their ability to absorb moisture and hold it against the metal. And chemical reactions occur quicker at elevated temperatures as well. Not saying you will have that problem since I don't know anything about their products but it might be something to keep an eye on.

You make an interesting point which I have heard stated in the past. However if installed properly and sealed with the coating DEI provides they state that should not occur. However your point is valid and i will be sure to monitor it as time passes. The car isn't driven all that much so that may slow down any process that may potentially occur.

Go side exhaust!! :beer:

I realize its both, I was more wondering which one creates the majority of heat or if they have pretty equal stakes in the final temp.

I'd say the diff itself is the primary heat generator, the factors that surround it however make it difficult for the diff oil temps to return back to a suitable level though.

 

[99COBRA2881]

Best ceramic coating there is. www.hpcoatings.com I still have to send my MAC LTs off but I'm waiting as I may send my new custom built Side Exhaust along to be coated as well.

 

[Sintore]

I am going to be running passenger side exits right before the rear tire to combat the heat problem.
For those of you thinking about going with aluminum bushing, I say it's best upgrade to plant the rear end. Also gives the back end a surefooted, solid feel. And sets the pinion angle to proper location.
-John

 

[9746Cobra]

SVT's solution was as we all know with the R, a diff cooler and side exaust. I don't know what bushings they used.

9746C

 

[9746Cobra]

I wonder what the difference would be just running the side exhaust without a cooler?

Maybe a metal bracket with a thin metal finned plate attached to it under the pumpkin to act as a heat sink?

9746C

 

[ac427cobra]

SVT's solution was as we all know with the R, a diff cooler and side exaust. I don't know what bushings they used.

9746C

2000 R did not come with a diff cooler.

The IRS bushings in the 2000 R were a harder durometer than std. Cobras.

I wonder what the difference would be just running the side exhaust without a cooler?

Maybe a metal bracket with a thin metal finned plate attached to it under the pumpkin to act as a heat sink?

9746C

IMHO any car that has MMFLSFC's will have a difficult time at best putting in a side exhaust.

FWIW
:thumbsup::coolman::beer:

 

[9746Cobra]

I looked into the side exhaust but it isn't going to happen with my maximum motorsports full length subframe connectors.

Oh well it was worth looking into.

Edited to add: Shouda waited for you to post! Might have saved me some searching.

 

[9746Cobra]

Okay so it wasn't standard on the R's it was an option?

9746C