HarvesterUT

iTrader: (10)

After I do a mod, I usually like to post about my experience and give my opinion on it to help out fellow Z enthusiasts who might be contemplating the mod.

Product: MD Iso-Thermal Aramid gasket w/ Copper Throttlebody Heater
Install Time: 3 hours from tools out to tools up
Pace: moderate with no breaks
Difficulty: easy

As usual, Motordyne packaged everything well and it shipped with all needed parts. I already had a 1/4" spacer installed so I was at least familiar with getting that far in the steps.

To my surprise, I received TWO aramid plenum gaskets with a note from MD basically saying, "here are 2 gaskets since most 350z owners report they can fit 2 gaskets and still have crearance". SO i figure SWEET i get twice the cooling properties!

The install was fairly easy. You need to completely remove the upper plenum from the car which requires 2 wire clips to be removed from the throttlebody area as well as 2 very hard to reach/see hoses on the underside of the throttlebody. They are a PAIN to get back on!

I easily fit 2 gaskets and had no issues with them. I coated them with a thing layer of motor oil before installing to ensure a snug fit.

The copper throttlebody heater was also very easy once I got the TB off the car and on the ground. The instructions don't say this, but when you re-install the TB you need to connect the old hoses on the the new copper heater pipes, not back on to their old location on the stock upper plenum.

I took the Z out for a spirited 30 min drive that would normally cause the plenum to get very hot. When I got home, I popped the hood and guess what? The plenum was almost COLD to the touch! My strut bar was a little more warm than the penum was! I could put my hand ANYWHERE on the plenum and it wasnt hot AT ALL.

I imagine the benefit of this mod is to allow for a colder/denser air flow into the engine, so I assume it's doing it's job since the plenum is now luke warm instead of boiling hot.

Overall I give this product a 9/10.

Z ya!

gringott

iTrader: (17)

Quick question - making some assumptions (heat rises)

The engine gets hot in operation.
Heat rises.
If it doesn't rise through the manifold, where does it go?
Does the cooling system get more efficent?
Does the oil temp go up?
Does the water temp go up?
The heat has to go somewhere.
So where does it go?

HarvesterUT

iTrader: (10)

IIRC, Hydrazine (motordyne) one replied to a question like this. his reply was the plenum doesnt do a good job of cooling the engine off anyways. apparently the engine fans and coolant do a much better job than the surface area of the plenum.

he said something like the plenum is a small % of the cooling capacity of the engine, and keeping it cool doesnt do much to the engine.

maybe he'll chime in if he see's this.....

gringott

iTrader: (17)

My question is not to be a sceptic, or a smartazz, but wondering what does happen to the heat, and how a thermal barrier can stop heat from rising.

Hydrazine

iTrader: (53)

Hi Gringott,

Check out this link. KP essentially asked the same question and my answer is in post #6.

https://my350z.com/forum/intake-exhaust/142359-motordyne-iso-thermal-plenum-spacers.html

The thermal barrier doesn't stop convective heat (or hot air) from rising. It reduces the conductive heat transfer between two heavy aluminum parts.

Its a heat barrier at the interface between the lower intake manifold and the lower plenum.

The link above gives a full description of everything and answers just about every Q imaginable.

Tony

gringott

iTrader: (17)

Read it. Must have missed it before. Thanks.

Acree

iTrader: (29)

harvester, thats awesome news. im tempted to buy the thermal kit with the stock plenum. i will be in austin sometime next month to visit a buddy at ut. wanna meet up?

HarvesterUT

iTrader: (10)

Acree,

sure sounds good.....let me know when you'll be here and we can meet up somewhere and maybe grab a bite and you can see the mod.....well you cant really "see" it.....I will out of town Nov 10th-13th and another as-yet-unknown weekend. The weeks are better for me...but PM me

another thing.....i strongly suggest that if you plan on getting the Iso-Thermal gasket you might as well get a plenum spacer as well.....since you do all the install steps anyways. might as well get another 10hp for no more effort.

Harv

yeperra

iTrader: (1)

I installed an insulated thermocouple to the top of the plenum and measured the temp. This should measure only the temp of the aluminum and not the heat under the hood. After driving about 30 miles on the freeway at 75mph in 6th gear the top only reached 117 deg F. This was the max and average was around 110 deg F. The outside air temp was 75 deg F. I wasn't totally sold on the insulator kit. Can you report any numbers as to how much lower the temps are?

Thanks

Hydrazine

iTrader: (53)

Veperra,

Did you get any pre installation temps on your plenum?

When I did mine, I measured a 30-60 F drop. OCG35 measured a 36-81 F drop with an average of ~50'F.

yeperra

iTrader: (1)

These are pre numbers. I have not purchashed the spacer yet. I was hoping to get somebody to give me post numbers. 50 deg F drop is impressive. That would mean the plenum is at the same temp as the outside air? I'm not sure that can happen with just a thermal spacer.

Zquicksilver

iTrader: (5)

Here's an interesting question, I think...

I understand that these AREO-SPACE materials reduce heat transfer from one material to another, but unlike spacers or air mods which physically increase the movement and volume of air, does reducing the temps of the plenum by 30% or more really make a difference in performance? I guess to make it even simpler, does mixing cool air in a cooler cavity for fractions of a second greatly improve anything? IMO, it's the same as a metal or plastic intake tube, only becuase that slightly cooler cavity is being refreshed with new cool air every split second.

Maybe you can enlighten me?

Zquicksilver

Hydrazine

iTrader: (53)

Hi Yeperra,

You are absolutely right. It will never get the plenum temperature below the air intake temperature.

When I did my own testing, I measured a wide variation in stock plenum temperatures and it greatly depends on how you drive.

So to try to hold that variable constant, I drove down the same stretch of highway for about ~20 minutes with cruise control set to 70MPH and with ambient air temperatures at about ~85'F. I did this 4 times to get an average. And the numbers were fairly consistant as long as you drive the exact same way every time.

I then installed the Iso Thermal and drove down the same stretch of freeway for the same length of time at 70 MPH and with only slightly higher ambent air temperatures. And did this 4 times. With Iso Thermal installed, plenum temperatures were 30-60 degrees lower than the stock configuration.

And I had 5 thermocouples placed all over the plenum for both pre/post testing. The 30-60 degree variation comes from some places on the plenum being cooler than others. If I said it droped plenum temperatures 30 or 60 degrees, it would be true but it would only be half the story. So I report the whole range for a good bounding of what to expect.

yeperra

iTrader: (1)

Hydrazine,

Thanks for the reply. I only applied 1 type K to the top of the plenum so I didn't get as much info as yourself. I'll look at picking up the insulator kit. Do you have any numbers or have you done any of the calculations on the hp gain per deg? I think the MINI guys had a chart for lowering the intake temp form the supercharger and related it to hp gains.

Thanks for the response.

yeperra

Hydrazine

iTrader: (53)

The additive effect of the Iso Thermal will be very subtle. In fact, it is best to simply say they do not add HP. But it will help to retain the power you have as the engine bay becomes heat soaked. Air density is proportional to its temperature and HP is proportional to air density.

So by blocking heat from getting into the air, you increase (or maintain) your HP.

And as far as the heat transfer rate is concerned, it is much higher in the lower plenum due to the turbulent nature of pulsed flow and small runner passages. I don't even want to speculate on how to calculate it.

There is a reasonable way to get a good rough order of magnitude of the effect though....

When I stoped the car and shut off the engine I measured plenum temperature Vs time. I found that with the stock configuration plenum, temperature would rise ~8 degrees per minute for the first 3 minutes.

That was only with the heat flux through the manifold causing the rise in temperature. (ie not including hot coolant flow)

Iso Thermal installed temperature rose ~4 degrees per minute for the first 3 minutes. So we know the Aramid gasket alone cut the heat flux in half. Now I don't know what the heat flux of the TB hot coolant flow is but lets assume its approximatly equal to the the heat flux of the lower intake manifold.

So if the engine coolant was still flowing, the total heat flux would approximatly double and we would see about an increase in plenum temperature at about 16'F/minute. This leads us to a ROM on the total heat flux.

The plenum assembly weighs ~12 lbs.
The aluminum it is made of has a heat capasity of 900 J(Kg*K)

Multiply the specific heat by the plenum mass and its change in temperature and you know the specific heat flux rate.

When you see the lower manifold heat flux rate get cut in half from the gasket, and we know the heat flux from the shut off CCV is Zero. So the heat flux is ~1/4 of what it originaly was.

Now for the effect on the air flowing through a running engine....

Lets assume the engine consumes approximatly 300 CFM/minute (21.6 lbm/minute) at the typical average spirited running condition.
We know that air was absorbing the same amount of heat that was being transfered into the plenum. We know this because plenum temperature shoots up when the car is shut off.

The VQ air consumption rate is ~21 lbs/minute at spirited driving.
Air has a heat capasity of 1000 J(Kg*K) at constant pressure.

When you take the plenums known heat flux (or its reduction reduction in heat flux with Iso Thermal installed) and multiply it by the air heat capasity you can calculate a reduction in air temperature by about 8'F.

8'F... This is a rough approximation but it doesnt sound unreasonable.

So what does this mean for HP?.... Take the ratio of air density to find out.

Assume the air is at 98'F by the time it gets inside the plenum. Its density is 0.0712 lb/CF. If you reduce the air temperature by 8 degrees, the air density is 0.0722 lb/CF.

1/((0.0722 lb/CF)/(0.0712 lb/CF))= 1.4% increase in air density.

Multiply 1.4% by ~280 HP
=~3.9 HP

Do I think it makes 3.9 HP?.... Probably not. My guess is it may be good for about half that. But then again, do you think heat soak can drain away 3.9 HP? It probably does a lot more than that.

So without putting it on a dyno this is a somewhat reasonable approximation of what Iso Thermal is worth. ~2 HP and less ping associated with elevated air temperatures.

Directly dynoing it would be extremely difficult without a real dyno lab. Dynos are usually done with an open hood along with many other non-real world test conditions. And most dynos don't have 2 HP resolution anyways.

If there are any errors in this estimation, its because I don't have the time to make a research project out of it.

I hope I answered your question.

Zquicksilver

iTrader: (5)

Hydrazine,

Thank you for the informative response, very thorough in your reasoning

I was thinking as technically off the top of my head, imagining, theorizing, and coming to that conclusion which you have so eloquently formulized above. I commend your efforts to bring efficiency to the VQ motor, even when minimal.

Zquicksilver

Tortuga

iTrader: (6)

I installed 5/16" spacer and Iso thermal gasket. I actually used the 2 gaskets that the kit came with and the top of my plenum is still quite hot. I had no problems with install, no leaks. Plenum spacer mod is awesome but I don't seem to be getting the cooling benefits of the plenum that others are getting. Any suggestions?

lightner22

iTrader: (1)

MIne isn't that cool either. I'd imagine it's much cooler than it was stock, but its still hot to the touch after driving.

HarvesterUT

iTrader: (10)

i find that it depends on the situation. the aramid gasket will not prevent the plenum from getting hot, but it will slow it down.

i was driving one day all along the freeway, and when i got home i popped the hood and my plenum was relatively cool. i dont know how/why, but after an hour of 75mph+ driving my plenum wasnt super hot

Beeker

iTrader: (5)

The thermal gaskets and throttle body heater only help when the car is moving. They help to prevent heat transfering from the engine to the plenum. When the car is not moving they can't prevent heatsoak from setting in. Especially once the car has been shut off. If you open the hood when you first get back from a ride you will see the plenum is cool to the touch. Without the thermal mod it would be hot.