Under Bonnet Heat Concerns

[mitsiboyblue]

Hi guys, you've brought something to light for me in one of your other posts with engine and under bonnet heat concerns ...

I've been reading all your posts about cooling fans and duty cycles Is this a common concern/issue i need to be worried about.

With all my mods and under bonnet heat problems i had last time. I've even bought a 36mm hole cutter and some rubber edging to make 5-6 holes in the bonnet along rear top edge (bulkhead area) just to get the heat out!

I burnt and shrivelled up some cable tidy along the top of the bulkhead and all through it didnt damage the wires too much it raised my concerns.
I've even tried bonnet hinge spacers to raise the bonnet up from the bulk seal but because of the bonnet and wing shape when opening and closing this is not possible to do.
Does anyone have some ideas?

Dave O

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[Nick Mann]

I thought some people had spaced the bonnet up?

Vents is the obvious thing.
Some have removed some or all of the rubber seal at the rear edge of the bonnet. The plastic trim round the wiper motor/arms will rattle if you remove it all.
I personally believe that the engine undertray helps the air move through the rear of the engine bay to keep the temps down a little better by the rear turbo.

[mitsiboyblue]

I thought some people had spaced the bonnet up?

Vents is the obvious thing.
Some have removed some or all of the rubber seal at the rear edge of the bonnet. The plastic trim round the wiper motor/arms will rattle if you remove it all.
I personally believe that the engine undertray helps the air move through the rear of the engine bay to keep the temps down a little better by the rear turbo.

I have never had any under tray fitted on mine but im guessing it would help.
I bought a 25mm bonnet hinge spacer kit from the bay but it was just not possible to open or close without catching the bonnet corners.


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[94000 Miles]

I've been considering getting one of these oval ducts to poke down through my undertray into the front flowing cool air.

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Then getting the bendy round ducting connnected to the above to direct it across the rear turbo or where ever it my be needed. The bendy stuff is adjustable.

s-l1600.jpg

Also has enyone thought about Turbo blankets to keep the heat from straying...

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[Amonlym]

My car has undertray and the rear gets hot enough to boil screenwash and has blistered the thermal insulation on the bulkhead, getting my idle speed down helped massively (950-1000 down to 600-650).

[mitsiboyblue]

My car has undertray and the rear gets hot enough to boil screenwash and has blistered the thermal insulation on the bulkhead, getting my idle speed down helped massively (950-1000 down to 600-650).

I can see this is quite a common problem when you start to play with the engines performance.
Wrapping the turbo .... wouldnt this then increase charge temperatures? something else we are trying to avoid.

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[Nick Mann]

Blistered thermal protection on the bulkhead is normal. In fact, I don't think I have ever seen a VR4 without blisters there!

[mitsiboyblue]

Blistered thermal protection on the bulkhead is normal. In fact, I don't think I have ever seen a VR4 without blisters there!

Just worried that when i really start to hurt the engine on a track day because this will definitely be happening, i dont want to be a victim of under bonnet fire or failed electrics.
I'm a firm believer that listening to and actioning on other peoples experiences could save me a whole lot of heartache through ignorance.
What do you think about additional cooling fan on switch so when im racing hard i just switch it on permanent and of when returning to the pit.



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[94000 Miles]

Just for information purposes, I took some temperature readings last August 2017 after a spirited drive with an infrared thermometer which isn't hugely accurate but gives an idea of what's what under the bonnet, all in Degrees Celsius.

Radiator Top Hose - 73

Cylinder Head Front bank ( not rocker cover ) - 73

Cylinder Head Back bank ( not rocker cover ) - 73

Rear Turbo - 240

Front Turbo - 206

Plenum - 58

Oil Filter - 86

Alternator - 78

Front Exhaust Manifold - 188

Also wonder what the Australians have to say on this subject with their elevated temperature climate.

[mitsiboyblue]

Just for information purposes, I took some temperature readings last August 2017 after a spirited drive with an infrared thermometer which isn't hugely accurate but gives an idea of what's what under the bonnet, all in Degrees Celsius.

Radiator Top Hose - 73

Cylinder Head Front bank ( not rocker cover ) - 73

Cylinder Head Back bank ( not rocker cover ) - 73

Rear Turbo - 240

Front Turbo - 206

Plenum - 58

Oil Filter - 86

Alternator - 78

Front Exhaust Manifold - 188

Also wonder what the Australians have to say on this subject with their elevated temperature climate.

Thankyou for that information..... priceless! so now i can see from those figures where the most heat is accumulating, its just like having a thermal imaging camera Brilliant!



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[TAR]

You need to be careful with making mods for cooling especially if you are thinking about vents or raising the bonnet. Mitsubishi will have spent a considerable amount of time in a wind tunnel ensuring enough air flows for cooling whilst moving (you only need the fans when stationary or a very low speed).
Cutting vents or raising the rear edge of the bonnet may well alter these characteristics and cause less efficient flow.
This is all down to low and high pressure areas generated by things like the undertray, radiator positioning, front wing and bonnet shape.

Be careful you don't make it worse.

I'm sure this has been discussed on here before, maybe worth a search.

[mitsiboyblue]

You need to be careful with making mods for cooling especially if you are thinking about vents or raising the bonnet. Mitsubishi will have spent a considerable amount of time in a wind tunnel ensuring enough air flows for cooling whilst moving (you only need the fans when stationary or a very low speed).
Cutting vents or raising the rear edge of the bonnet may well alter these characteristics and cause less efficient flow.
This is all down to low and high pressure areas generated by things like the undertray, radiator positioning, front wing and bonnet shape.

Be careful you don't make it worse.

I'm sure this has been discussed on here before, maybe worth a search.

Yes i hear you, and really do appreciate every comment, my concerns are that ive already burnt and shivelled cable insulations, tidies and zip ties along the bull head through 'Spirited Driving' and worry about the further mods (Hibyid turbos) ive done that will definitely affect the running temperatures under the bonnet. I have no under trays and never had. maybe this is a contributing factor to issues i have?


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[Oblivion]

I added a vented hood and thicker alloy radiator without much effect but buy far the biggest change I saw came from adding an oil cooler and relocating the oil filter away from the downpipe. This dropped both the oil and water temp by about 20deg on the highway.
I'd like to cool the rear turbo / plenum area more but still thinking whether forcing air in or out is going to have a better effect (currently leaning towards air going out).

[mitsiboyblue]

I added a vented hood and thicker alloy radiator without much effect but buy far the biggest change I saw came from adding an oil cooler and relocating the oil filter away from the downpipe. This dropped both the oil and water temp by about 20deg on the highway.
I'd like to cool the rear turbo / plenum area more but still thinking whether forcing air in or out is going to have a better effect (currently leaning towards air going out).

Yes, did you read my first post that I'm tempted to cut 5 or 6 round holes at the rear of the bonnet above the turbo to get that heat out! The installation of a oil cooler and re-location of the filter now is infront of the gearbox well away from the heat of the front exhaust.... this is one thing i have already done, although ive yet to find out its benifits as the VR4 is still not quite ready for the road.
Im still running with the stock radiator for now..... as i have read that changing out to alloy doesnt really make dramatic temperature changes due to ECU Duty cycling at fan speed controller and air flow obstructions caused by larger modified intercoolers (which i also have) but in the prevention of coolant leaks its a no brainer not to go alloy.
Have been toying with the idea to add an electric fan to the oil cooler for additional cooling if i see too high oil temps on track days,
Dave O



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[Nick Mann]

Glad you have done the oil cooler. It is on my list too, I'm even more certain after Aaron has posted that it is a very good idea for track days.

A fan on the oil cooler is probably a good idea, but why not stick it on a temperature switch?

[mitsiboyblue]

Glad you have done the oil cooler. It is on my list too, I'm even more certain after Aaron has posted that it is a very good idea for track days.

A fan on the oil cooler is probably a good idea, but why not stick it on a temperature switch?

Thats an even better idea! Because really.... who has time going round the track to watch everything else, i think automatically controlled is far better. Need to find temperature switch now.
Any ideas of ideal operating temperature? as really im not sure.

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[Nick Mann]

Nope, sorry, not something I have researched!

[Oblivion]

Yes, did you read my first post that I'm tempted to cut 5 or 6 round holes at the rear of the bonnet above the turbo to get that heat out! The installation of a oil cooler and re-location of the filter now is infront of the gearbox well away from the heat of the front exhaust.... this is one thing i have already done, although ive yet to find out its benifits as the VR4 is still not quite ready for the road.
Im still running with the stock radiator for now..... as i have read that changing out to alloy doesnt really make dramatic temperature changes due to ECU Duty cycling at fan speed controller and air flow obstructions caused by larger modified intercoolers (which i also have) but in the prevention of coolant leaks its a no brainer not to go alloy.
Have been toying with the idea to add an electric fan to the oil cooler for additional cooling if i see too high oil temps on track days,
Dave O



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Yeah I saw that! I also saw your post in another thread how your oil cooler is set up, mine is quite similar.
I'm not sure how effective a fan would be, I'd think there should be enough air flow when traveling at speed on a track. Another thing I've wanted to do for a while is build a shroud from around the oil cooler to the duct in the bumper- which should force more air through the cooler (instead of some of it going around it) and increase efficiency. Should oil temps still be too high then I'd try adding another oil cooler on the other side, more oil capacity and double the cooling? Haha

[mitsiboyblue]

Yeah I saw that! I also saw your post in another thread how your oil cooler is set up, mine is quite similar.
I'm not sure how effective a fan would be, I'd think there should be enough air flow when traveling at speed on a track. Another thing I've wanted to do for a while is build a shroud from around the oil cooler to the duct in the bumper- which should force more air through the cooler (instead of some of it going around it) and increase efficiency. Should oil temps still be too high then I'd try adding another oil cooler on the other side, more oil capacity and double the cooling? Haha

You know, doubling up on the oil coolers sounds like the answer as ive seen other cars with two in the past and wondered why. I will try a track day and during pit stops record some data with my lazer temperature gauge.
Maybe these excessive under bonnet heat problems i experienced last time was due to really hot days at that time anyway.
And yes i agree with you maybe adding the electric fan would only add benifits at slow speeds and idle conditions other than that it could be just an obstruction.
The ducting you mentioned would serve better, i dont know..... these things are all experimental thats why we all have these discussions bouncing ideas .
Dave O

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[Oblivion]

Do Evo's just have the one oil cooler from factory? Or what do Evo owners do do address any heat issues? Might be relevant I guess.
I was surprised when I found out our cars didnt have one, but I guess they werent made with any intentions to go racing