Engine cover leave it on or leave it off??

E

evo188

Member
Location
Secaucus, NJ
Hey,

I have notice the engine of the FX45 pretty hot, since we had the 4 days of almost 100 plus degrees it even more hot.

Would taking the cover off create better air flow in the engine to cool it off or let the heat escape faster ?

Any suggestion 45er's out there.
 
I'm running with the cover off for about a year.. I can't say I feel any additional power but I believe it helps out the plenum cool off especially when it gets heat soaked.
 
evo188 said:
Hey,

I have notice the engine of the FX45 pretty hot, since we had the 4 days of almost 100 plus degrees it even more hot.

Would taking the cover off create better air flow in the engine to cool it off or let the heat escape faster ?

Any suggestion 45er's out there.
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I am naive and think that if it made a material difference, Nissan engineers would have not put on an engine cover on. If it was that easy to increase HP, increase MPG, or increase longevity of the engine by keeping it cooler, I would hope Nissan executives would have opted for that over aesthetics.
 
Chedman13 said:
I am naive and think that if it made a material difference, Nissan engineers would have not put on an engine cover on. If it was that easy to increase HP, increase MPG, or increase longevity of the engine by keeping it cooler, I would hope Nissan executives would have opted for that over aesthetics.
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Nissan engineers/executives didn't bother increasing the height of the plenum to allow better air to the front 3 cylinders just because there was a strut bar on the 350z. If Nissan engineers were all that good, we wouldn't have plenum spacers as the best mod around.. Do you know any other brand that even know about plenum spacers?

I'm not trying to discuss the effectiveness of leaving the cover off here but the logic above is faulty. It applies in some cases and it doesn't in some. It's obvious that Nissan would LIKE to leave the cover on because
1) It looks better. Not everybody would pay 40K for an FX and get an ugly engine.
2) It's much expensive for Nissan to come up with a beautifully shaped plenum than a plastic one

Finally, using simple logic, you can see that the engine cover WILL trap some heat under it. Try putting a plastic cover over your heatsink (metal cpu cooler you see inside) and you'll see how quickly the heat on your CPU will rise.

It might not be a 20 hp gain or anything close to that but it will help on heat soak and it will help keep your plenum cooler thus better performance.. Significant? Don't know but better than with a cover.. We're spending over $500 for an exhaust mod that wouldn't give you 10 hp in most cases. Taking the cover off for 3-5 hp for free is logical for me.
 
I can see your point of the quick rising temprature, once the engine is up to normal operating temps, I dont see it robbing us of much if any power. My buisness has to with Insulation etc and I can tell you that plastic like that is no good at insulating. Now your hood liner would be a better insulator if anything. my 2c.
I've left mine on, I like how it looks compared to the sand molded aluminum... If I ever run a polished crawford plenum, now that's another story.
 
EgeFx said:
Nissan engineers/executives didn't bother increasing the height of the plenum to allow better air to the front 3 cylinders just because there was a strut bar on the 350z. If Nissan engineers were all that good, we wouldn't have plenum spacers as the best mod around.. Do you know any other brand that even know about plenum spacers?

I'm not trying to discuss the effectiveness of leaving the cover off here but the logic above is faulty. It applies in some cases and it doesn't in some. It's obvious that Nissan would LIKE to leave the cover on because
1) It looks better. Not everybody would pay 40K for an FX and get an ugly engine.
2) It's much expensive for Nissan to come up with a beautifully shaped plenum than a plastic one

Finally, using simple logic, you can see that the engine cover WILL trap some heat under it. Try putting a plastic cover over your heatsink (metal cpu cooler you see inside) and you'll see how quickly the heat on your CPU will rise.

It might not be a 20 hp gain or anything close to that but it will help on heat soak and it will help keep your plenum cooler thus better performance.. Significant? Don't know but better than with a cover.. We're spending over $500 for an exhaust mod that wouldn't give you 10 hp in most cases. Taking the cover off for 3-5 hp for free is logical for me.
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I understand your analogy, but you can't really compare the delta of a CPU by coming a heat sink with a engine covered by a engine cover.

Logically, the delta on a CPU can be larger due to the lower running temperature of a CPU. When you're at a running engine temperature in 200 degrees F (I have no idea what it is, but you get the idea), and have a huge hood with insulation as well, I can't see a huge delta from having the cover on/off.

If someone can prove a 3-5 hp gain from removing the engine cover, I'm happy to take the dunce cap and will bow down to you (which I think is possible but highly unlikely). I'm guessing this will take a standing dyno with a huge fan to simulate wind so the extra potential cooling affect of removing the engine cover will/will not show.

I'm also the wrong person to talk about this as I bought an exhaust and intake for sound purposes being priority.

And yes, I have faith in Nissan Engineers. They must create an engine to fit a variety of models, so some excepts do need to be made.

Don't take this personal, I'm just stimulating conversation.
 
Chedman13 said:
Don't take this personal, I'm just stimulating conversation.
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no problem :smile: Keemo's post is informative on this and I believe he has a point. The cover has space under/around it where air can come in and prevent any increase on the temps when there's air flow around it.. However, my main point was that if you take off the cover, it'll help you out on heat soak. When you drive your car for a while and go park for a while you'll experience heat soak the next time you drive your car. An open aluminum plenum would cool much faster than one that prevents good air flow and covered 100% by a plastic cover. The cover doesn't insulate the plenum, of course, but it prevents proper air flow around it.

Instead of a dyno run, you can measure the temps on the plenum with an infrared temp gauge. Again, it might not be significant and you might not feel it but I think it'll be helpful..

Btw, delta we're talking is the temp difference right? I believe a CPU cooler would have a larger relative delta because it would have fins to help it cool more and faster. Maybe soldering aluminum fins would help (and uglify) the plenum, huh? :tongue:

As for the Nissan engineers... They did a great job on the VQ engine and they are obviously much more experienced than any one of us here.. But everybody have flaws and priorities right? That's why we have mods.. One's flaw or priority might not fit you thus you have a chance to improve something on the same product you have.. You like the cover on because it looks good, I prefer to get a Z cover and paint it and it'll look good enough for me and will help me out on my priorities.. :smile:
 
EgeFx said:
no problem :smile: Keemo's post is informative on this and I believe he has a point. The cover has space under/around it where air can come in and prevent any increase on the temps when there's air flow around it.. However, my main point was that if you take off the cover, it'll help you out on heat soak. When you drive your car for a while and go park for a while you'll experience heat soak the next time you drive your car.
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OK. I can't resist throwing my two cents in. I leave my cover on mostly to protect all the stuff that's underneath it. From what? I'm not really sure but I feel better having it there. If I ever make that trip to Englishtown I'll probably do the runs with it off.

I have a carbon fiber cover I've been meaning to install. The purpose of that one will be mostly aesthetic. Regarding the heat soak question I've sort of taken a pragmatic approach.

Motordyne's isothermal system was designed specifically to reduce heat soak to the plenum. If I search hard enough I know there were measurements taken. It does this by insulating the lower collector from the heads (there's an insulating lower gasket and their spacer is insulating as well ) and cooling the air intake temperature either by cutting out the coolant circulation around the throttle body or insulating the throttle body from the coolant.


Admittedly I'm a Motordyne fan. But my point is this. If you're worried about heat soak affecting performance - and this is a reasonable thing to worry about - why not tackle the area where you're likely to get the biggest gains first? Since the heads are the hottest part of the engine, at least to me, it seems like how to insulate the intake and collector area from that heat should be mission one.

The conversation about upper plenum heat dissipation with the engine cover on or off is a fun one. I just wonder, from a pragmatic standpoint, whether it has any true practical merit and we'd be better off considering insulation from the engine block.

Anyway, just my two cents.
 
Ive been toying with the idea of putting mine back on but id have to get it painted first so it looks nice.

with the engine cover on/off you probably wont even know the difference.
 
Rob,

It's true that MD spacer insulates it to a point but I have the stock lower plenum, not the MREV2. I don't remember any part except the thin inner gasket isolating lower plenum from heads. The second thing is that this thing gets hot even with the hot air coming from below. Think about how hot your hood gets when you drive your car for a while and it's not even in contact with almost any part of the engine.

Anyhow, this is just a small thing.. Probably not even worth discussing it this much :smile:
 
Keemo said:
I'd love to see that for some reason. :laugh: Or go futher with a liquid cooled plenum.
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Well one thing for sure: it would cool down much faster with fins but for obvious reasons (fins breaking, moving around like shrapnels) it's not logical to do..
 
Hi Ege,

You're right it's a small thing. But I have a spare 30 minutes and this is a fun topic to consider. Sort of like mental bubble gum if you know what I mean.

Here's a link to the lower gasket I referred to. It's $35 and sits between the lower collector and whatever the thing it sits on is called.... :laugh: Gotta admit, it would be a lot of work to go that deep in the engine just to install an insulating gasket......

http://www.motordyneengineering.com/images/AramidGasket.JPG

What I'm considering in your reply earlier is what's hotter and where are you likely to get the biggest benefit? Heat soak from the heads to the plenum or the ability to cool it once it's hot. There are two dynamics at work here simultaneously.
 
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ha, since you put it that way rob I'll throw my 3 cents in to chew on:tongue:

if you were racing, in between rounds it is very beneficial to force cool the intake even, by packing it down in ice. hardest part is doing this without water puddling or dripping down, if your dripping when your up your kicked out.

this may or may not add a 10th or so, it may even be a measurable difference & since racing is all about measurements it's significant enough to consider the issue of heat soak, but if your driving to work, then stopping at the gym, driving home, driving to the mall or shopping, & yeah, once in a while punching it wide open throttle on a highway entrance or something then realistically the difference is so slight & unmeasurable & insignificant that it doesn't even matter all that much one way or the other really.

I guess if your the type that really pushes her hard & even measures with a g tech or something then yeah, you'd probably not want to run the cover.

my cover is off, I'm going to polish a crawford & run no cover or a very minimal custom harness cover.
 
On Track days.....

I pop the hood open in between rounds to let some of the heat escape.
Usually theres about an hour in between rounds. Does it help? Dunno....cant really say either way.

I've seen guys using ice and dry ice.....
 
"DaveO tested the charge temp w and w/o the cover and consistently found an improvement with cover off...over 10degress

Manufacutures do for looks not performance\

testing done on a 35 not a 45 although big gains for both"

This was sent to me by a friend of mine. I'll let him chime in/introduce himself if he chooses to :smile:.
 
Just wondering. Does anybody really think the plenum would cool faster with the engine cover on? :hmmmm2: If I ever race sure it goes off.

Since my other hobby is BBQing I'd like to thank this thread. It's given me yet another reason to go out an buy that infrared surface heat measuring thermometer I've had my eye on. Maybe if we ever have that 0 to 60 day out in Long Island I can use it to settle this once and for all. [My money's still on the insulation yielding the bigger benefit.]

Or if not at least I get a new toy out of the deal :biggrin:.
 
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The cover on or off makes no difference. If you're at the track and pop your hood, yes, it will retain more heat. If you're driving around, no, it will not retain any more heat. Mind you I have a 1/2" MD Iso-thermal spacer kit, complete with the Aramid™ gasket that was spoken of earlier, and I even had the copper throttle body insulator with insulated liquid gasket. After I received it and installed it, I wanted to test out how much it reduced heat soak on the plenum...

Before installation, if I ran hard for a good 15 minutes in the middle of summer, the plenum would literally be too hot to touch for more than a couple seconds. After installation, the plenum was just plain hot, or uncomfortable, if you will.

I also did a similar test with the spacer on and the cover on, then when I took off the cover to feel, it felt the same... uncomfortably hot.

You don't have a rush of air flowing over the engine. If you did, you'd see a rush of air blowing water clear up your windshield when it's raining out, like a blower at an automatic car wash for the drying phase. The cooling effect on top of the motor is not enough to warrant taking off the engine cover for performance sake.

Now ambient losses through the hood via radiative heat is another story altogether. Like someone also said earlier, if you really want to stop insulating the top of the motor, the hood liner is what you should be thinking about.

Oh, forgot to mention... there's another major heat source to the plenum that I don't think has been mentioned... at the neck where it joins the throttle body, there's very hot coolant flowing through heating it up... which is why the copper MD kit removes the coolant flow from direct contact with the plenum and throttle body.
 
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