So, Stylemon got me thinking, with the VMIC installed I am considering buying a vented hood to help with temps. But honestly I don't like many of the hoods I have seen. I don't need carbon fiber and would prefer it to look as clean as possible, not wild street racer styled.

Has anyone made their own vented hood? What about starting with a steel NA hood and cutting and fiber glassing in a vent? Adding a prefabbed vent or vents to stock TII hood?

What are your ideas? What type or style vent would be the best to use? I am in no rush and would be very pleased if I could make my own vented hood instead of dropping +$600 on a hood.

Maybe something like these:

 

that is a awsome idea id love to see that. maybe you could try finding some steel vents and weld them in

 

I have a buddy who's TII has the same setup but doesn't use a vented hood. He says he has no problems with temps. Maybe a design like his would be better suited as to not be rice like.

 

Maybe something more like this:



I mean you could pretty much do anything but I am curious what would be best for temps and airflow. One big vent or two small ones? I know there are some pretty smart guys on here that are way more familiar with the physics of this, please feel free to leave some ideas or suggestions.

 

Freeman, what do you mean a design like his?
This my setup right now:

 

https://www.rx7club.com/showthread.p...II+intercooler

Checkout post #21. I really like the setup on that TII.

 

The duct inlet for the heat exchanger should be roughly 1/4 the cross-sectional area of the core. If your car is intended for low-speed high-boost operation, such as a drift car or burnout contest car, then you may want to move up to a 1/3 ratio. A high-speed track car, such as a NASCAR or F1, would probably work better with something closer to a 1/6 ratio. The outlet should be about 15-20% bigger than the inlet. Ideally, the outlet would have a flap that you can adjust to let more air escape, but that may not be practical for your situation. If you take the height of the heat exchanger core, the inlet and outlet are supposed to be at least this distance away from the core, but once again this may not be practical so just do the best you can. Each heat exchanger (intercooler, radiator, oil cooler, etc.) should have its own duct if possible.

The best type of outlet is one without restrictions like louvers or grating. However, once again, this may not be practical for your situation.

If you want to get fancy, you could duct the outlet air into an elaborate microblowing system. OK, maybe that is a little beyond the RX-7 realm, but it would be pretty neat anyway, hehehe.
http://www.grc.nasa.gov/WWW/RT/RT199.../5850hwang.htm

One of your local hot rod shops can probably put the louvers directly into your hood, or if you are a cheap bastard with lots of time on your hands you can try it yourself.
http://www.streetrodderweb.com/tech/...all/index.html

 

Hey Evil, THAT is some great info! Thanks for sharing.

NJGreenBudd, I was thinking of trying to duplicate the Panspeed hood, almost exactly. In my opinion, all those louvers complicate the design of the car... and look weird.

Notice they put a small vent over the turbine.. Great Idea!!

 

buy a vent you like, measure, cut, rivet. done and done

top


bottom

credit to dcwfc3s nbdt

 

where did you get the vent

 

not my car, its a uras style vent from jspec.com but the theory applys to whatever style vent

http://jspec.com/typenvent.html

you buy; align,trace,cut,drill,rivet/fiberglass.

*its alot easier with an aluminum hood like above^^ and you gain the weight savings versus a steel hood

 

its actually best to start with a glass hood if using a glass vent, a glass vent will bond much better to a glass hood, steel or aluminum fiberglassed will shrink and shift as it ages. You will definitly get a line and perhaps a crack along the line where they meet.

you can obviously find a CF style hood and paint it, or buy a plain glass TII or NA hood and modify from there. Just be warned- doing bodywork on a very visable and flat area such as a hood is not for the faint of heart, if you are picky about your car and how it looks you may want to convince a friend who does it for a living to give you a hand.

Or just rivet it on and live with it.

 

I think I'll start with a cheap NA hood and go from there. I'm confident enough in my limited body work skills to give it a go, otherwise I might end up having a local shop give me a hand top get it just right. I'm thinking something similar to the Panspeed hood, one major vent over the VMIC and maybe a tiny one over the turbo like that, looks pretty good to me.

Thanks for all the input guys. I'll certainly post along as it happens.

 

for my tastes a riveted on scoop with some carefully applied seam sealer or bonding adhesive would look 100% better then wavy bodywork.

trust me- bodywork on a very visable part of a vehicle such as a hood that is subject to extreme temps from both the engine and the sun is not easy, its not what it looks like when your done, but rather what it will look like a year or so later after it cycles.

 

Yeah I think a prefabbed vent carefully installed should look pretty good, I wouldn't try to make the whole thing from FG, at least not yet.

Here are some pics I had showing some of the different styled hoods, maybe we can get some ideas from these and blend them into one new hood.



















Maybe something like this:

 

Consider this vent, it is like an STi vent turned backwards, so it vents. This is a cut, then drill and rivet deal.



It is 18 X 10, and is pictured with the rear edge down.

Carbontrix.com offers this. I think this would look much nicer than those large angular vents, and with proper ducting should work well.

Vince

 

thats what my car would look like with the panspeed style hood!! Sweet!

 

I really like that man, good find for sure. That and an NA hood could be great.

Do you think it could work on a modified TII hood? Like close in the stock scoop and add this more towards the front? Wonder if if would look too busy....

 

So I have found my solution to the vented hood dilemma. My first step is to log some temps with the VMIC and stock hood and then install the new vented hood and log some data to compare. I will post some pics of the hood and results in a few days, I think most people will like the results.

 

Can't wait to see how it turns out.

 

i will!

 

In order to get any meaningful results, you will need to log 3 different temperatures at the same time: outside air temp, compressor outlet (intercooler inlet) air temp, and intercooler outlet (throttle body inlet) air temp.

If you are driving the car, you will also need to log the vehicle speed. Technically, you are supposed to log the airflow rate through the heat exchanger core, but I think that vehicle speed would suffice for an internet forum. If the car is stationary, then you just need to make sure that any external cooling fans are positioned and operating in a similar manner during each test, and you really wouldn't need to log any airflow information because you could consider that factor a constant.

 

Why not log the air pressure differential between the front and rear of the v-mount? Do this before and after you make any changes.

What you are really trying to attain is improved airflow. That will come from increased pressure differential.

All the hoped temp differentials are really a result of improvement of the airflow. If you focus on the temps, you introduce a lot of variables making the analysis much more complex than it really needs to be.

focus on the actual airflow improvements, not the result of those improvements. The results will come if your focus on airflow.

Use an ebay manometer, OR you can build your own. You probably need something that will have resolution in the 0.1" H20.

 

It doesn't work like that. While there may be a slight difference in pressure, the primary factor in a vented hood vs. non-vented hood would be temperature. The expected result would be an increase in density as indicated by a drop in temperature, not a rise in pressure. While the physics behind all of this is fairly complicated, I think the best way to explain it is to give the example that no matter how much ice you pack around an NA engine's intake system, you will still see no significant boost in pressure, although you will definitely see a drop in temperature and resulting increase in density which would be indicated on a dyno run.

Besides, the wastegate is set at a given pressure, so the indicated peak pressure would not change regardless of the thermal efficiency, and a mechanically-actuated wastegate would skew the results even worse.

However, you do make a good point that measuring the pressure differential would make the test more accurate, and it is not such a bad idea to check to see how well the entire system is working while you are at it.

FYI the pressure advantage of a horizontal-mounted intercooler comes from the straight pipes running out of the end tanks which eliminates the two usual 90 degree pipe bends. I would estimate that this is good for nearly 1/2 psi in most RX-7 applications.

 

I just figured I would see if this setup makes for cooler intake charge compared to stock TMIC, then compare VMIC w/ stock hood to VMIC w/ vented hood. I think the difference in temps will indicate whether or not it's more effective, might not be the most complex analysis but it will tell me what I need to know. Assuming all other variables are constant minus the change of intercooler or hood that is.

I'll let you know when get the results.