observable engine temp change with vented hoods?
 

I'm thinking of getting an open hood like knightsport or mazdaspeed. I have a greddy smic and like the idea of helping airflow through that plus and more importantly I want the engine to cool down.

So can anyone tell me if they have observed any significant improvements???

Thanks!

no thoughts?? :(

my guess would be that it's more help for when you shut down, or maybe in traffic, but if you're driving freeway speeds it's not going to make a difference.

it really depends on the hood. I've heard from people wiht the scoot hood that it makes a noticeable difference. Some even have probems where they can't get their cars to get out of warm-up mode etc.

wow

So just warm up the car with the stock hood on then switch it when it's warmed up. ;)

I agree with the the theory that when the car is moving, not much benefit. Are you looking more an for engine temp decrease or engine bay temp decrease?

I heard that the vent hood helps. But I still wonder myself if it's true and how much could it helps

Well - if everyone agrees that the engine and the engine bay temps would be improved without a hood then one should be able to say that temps would also improve if a certain percent of the hood was vented.

I'm just wondering if anyone has any direct experience...

thanks!

I have no real numerical way of showing you how it might help, but i do know, that when you get to a stop light or moving very slowly in texas summers, i can SEE the heat waves billowing out of the hood. Thats enough proof for me. But wouldnt a vented hood improve engine and engine bay temps even better when the car is moving? There is a lot of ambient space inside the bay all the times, and when the car is movin, there it will stay unless it has some sort of negative pressure to flow the air out, creating more cooling... Does that make any sense?:confused: Haha anyways, Brentis if you need one, hit me up!

Huy

Huy - you are my guy for a knightsports replica... :) Preferably I want one whic has a good latch structure where I don't need hood pins.

I agree, vacuum increases in the front/middle of the hood as speed increases. This is caused from the redirection of air as it hits the nose, as speed increases the vacuum does as well. Further it gives an escape path for the trapped air in the engine. when released it also allows improved flow through the radiator and IC.

Mine definitely helps on the track - about 10 degrees cooler under hot conditions.

Can't see any difference on the street, but I run cool there anyway, and nearly always have the fans on.

It should help keep over all temperatures down but it won't help you if your car is over heating. Upgrade your Radiator and oil cooling system first. I saw a huge decrease in temperatures when i did that.

I noticed a big change. I have a Scoot Hood.

I posted this awhile back but to recap basically I was running right after my rebuild Water Temps 100+ and Oil temps 115 or so (it was a hot Florida summer but still..). That was with the new Fluidyne radiator

If I remember right, it progressed like this as I modded:

Datalogit used to turn fans temps on at full at 85 degress and replaced an apparently faulty relay, added Water Wetter. Water Temps stayed under 100 typically 95, Oil Temps about 110.

CWC Dual oil coolers (my single cooler was so badly stoned the fins were pathetic) . Oil Temps dropped to I think about 85.

A month or so later I changed to the MB Feed Version 1 style bumper, put on oil cooler ducts, and put on the Scoot hood when I had the car repainted. That's where I am now:

Oil Temps 60-80, and Water Temps rarely if ever budge over 86-87 typically 85 or lower.

I even posted a message back then if it was dangerous to have too low oil temps....that's a net drop of 40+ C degrees in 6 months even considering it's no longer summer.

Also, I have an autometer F H20 Gauge and then the PowerFC in Celsisu. They confirm each other. I also have a Delfi Oil Temperature gauge which is how I'm getting those.

David

Just to add to my previous message, obviously the bigger front with the ducting probably had more affect on the oil temps than my hood.

I would definitley recommend oil cooler and radiator upgrades first but I think you'd see a noticeable if less radical improvement with the hood on top of it.

Of course it lowers temperatures
 

The same effect of ram air or corbra jet (early mustages) prove this out. Now you want the scoop further back fromthe radiator as it will draw air in from the scoop and 'entrain' air coming out of the radiator and it will drop out around the transmission and udner the car. THe other effect is it will draw more in for a 'cold air' intake as well.

I say do it, any little amount of cooling air helps.

The stock hood is really good for keeping the engine insulated during warm-up. Vented hoods are great for if you live in a warm climate or if its a summer switch out thing. Assuming you keep your car garaged if you live somewhere cold enough to have warm-up problems with the vented hood, one of the easiest solutions is to drape a towell or two over the vents while its warming up. Heat rises....this will slow it down and help to recirculate it within the bay while the beast wakes up. If your hood does not have insulation lining and no perimeter seal, then it will also decrease the insulation ability and increase the cooling ability of the hood. As far as the cooling effect vented hoods have on cars.... it does make a big difference, especially if you have upgraded your radiator and/or intercooler.

The best cooling mod you can do is put a 99 front bar on the car. Mazda had an SAE paper saying that they saw >100% improvement in cooling efficiency in the rad and closer to 150% imporvement for the oil coolers.

The same cannot be said for vented hoods since nobody has done the research. But since the stock rad is so choked of airflow (particularly on the series 6 and 7)that it would have to have a decent effect. Not to mention the reduction of heatsoak and the benefit that would have for the lifetime of the hoses etc in there.

PWR calculated that their 72mm core radiator had a whopping 5% improvement over their 42mm core on an FD. Having a front mount only magnifies the problem by throttling airflow even more.

-pete

GotoRX7, what type of hood do you have?

A lot of times when you change to an aftermarket front end with a bigger opening, a vented hood will help aerodynamics as well. with a bigger frotn end, the front of the car actually lifts up a little because of all the air going into the front. After I switched to a FEED Type 2, I can actually see the hood pushing up if I go for speeds over 80mph! With a vented hood, the excess air in the engine bay will be able to exit better and get out and that's enough reason to do it right there

Hey Pete, Where can I get more info on this 99 front bar.

I think he means the 99 spec bumper.

Thanks guys. I appreciate the input.

I do indeed like the 99 spec front, but from a cost perspective the hood seems to provide more bang for the buck.

Does anyone have any cost effective ways to add another oil cooler? From what I've seen they are pretty proud of the aftermarkets.

if you want to do a rice mod... :D u can put a couple of washer to the bolt of the hood... this will lift up the end of the hood near the wipers... and leav a small gap to let hot air out... ;)

dont know how much temperature drop you will get but its so rice that it is cool... hehehe

I had a knightsport hood on my car and it made no difference when I took it off plus it was a bit heavier than the stock aluminum hood :). Better ducting and a mazda speed front bumper will make a dramatic difference. My car is currenctly having a larger oil cooler and some duct work installed because of heat issues with my front mount ic. Mitch Piper said the only good alternative was a better bumper but I just don't care to spend excess of 1k on one. He is going to install a bigger single oil cooler, cut a larger hole, and fabricate a better duct. He is also cutting the center section/mouth opening larger and reducting that for the radiator. I am hoping these two changes will keep my temps at or below 92c during lapping events. If it does not work I will try two large oil coolers and a mazda speed bumper and if that doesn't work I'll just give up on the front mount :)

WOW these are some good insights! and i'm interested in investing in one in the near future! and yeah i've talked my to friend who has a civic, a while back and he says it makes a huuuuuuge difference on the cooling down process, but he didn't mention anything about cooling while driving! I guess it does make somewhat of a differece though!

Pete-

Since I've got a 99 spec bumber on the way, would you happen to know where I can get a copy of the SAE report? Not only would I like to read it, but it might make the $2,000 expense a little easier to swallow, knowing that I am "doing the right thing".

Thanks!

Ron

are you referring to this?

"The third-generation RX-7 had come off Mazda's rigorous development test programs on the bench and on the demanding Global Road Circuit section of the Miyoshi Proving Ground with flying colors. Yet, there was one arduous test left undone. When the car was taken to a race track near Tokyo known for its tight turns requiring short bursts of speed followed by fierce deceleration, the pride of Mazda's rotary rocket team quickly cooked its powerplant when pushed to the limit. Subsequent investigation revealed that air temperature at the entry area had risen as high as 50 C (122 F). Fresh air for the engine's consumption was taken from the single intake that also fed to the air-to-air intercooler. On wide-open driving, air flow reversed its course from the intercooler and went straight into the engine's intake. The intercooler was acting as an inter-heater! In the updated RX-7 with a designed fascia, fresh air is taken through a separate, dedicated duct guided by a newly installed air-guide. Air temperature at the engine's intake entry area has been halved to about 25 C ( 77 F), which adds about 7 kW (10bhp) to the output.
The front-end's opening areas have also been increased by factors of 2.1 for the radiator opening, 1.8 for the intercooler duct, 1.8 for the oil cooler, and 1.6 for the front brake cooling duct intake over the previous RX-7. The radiator's core depth has been increased to 27 mm (1.1 in.) from the previous one's 25 mm (1 in.). The 209 kW (280 bhp) engine had its fin-pitch changed from 1.1 mm (0.04 in.) to 1.3 mm (0.05 in.). Twin cooling fans' blades have also been increased, one from five to seven blades and the other four to five blades, while the high-speed electric motors' consumption has been changed from 160W to 120W."

http://robrobinette.com/sae_article.htm

Negative sir! this actually creates a low pressure zone which sucks air back under the hood from the back (thre are videos on the net showing this on a FD) and this would slowdown the amount of air comming thru the radiator (well supposedly...) causing your engine to heat up. Use airsheilds! the only way to cool down your engine a noticible amount is to get more air thru the radiator and not around the engine block!

I have been running at least one year without the rear hood seal and I havent seen any temp changes with or without the seal in place.I know for sure that in traffic I do see heat waves coming out from under the hood gap so I think it cant hurt. I would think you would need to be going really fast to restrict flow into the radiator.

It is a copy of (I think) the Knight Hood??

There are pics on my website (in my sig).

i have seen no difference when running but the temperature drops at idle at a light, which i had never seen with the stock hood.

i have a mazdaspeed replica

I knew I read it somewhere. From "Press Information - Rotary Engine 1999" Subsection 13b-REW:

This file is getting around the net as rotary_e.pdf

-pete

-stupid question;

What about rain water getting into the engine area when stopped in traffic, or in a parking lot on a rainy day. Does water not hurt the engine assuming that all the wiring is sealed correctly?

Doesn't seem to be a problem when washing the car - although I do try to minimize pushing water into the vents. And if you think about it, there is usually quite a lot of water splashing around the engine bay when you are driving in heavy rain anyway?

I can't beleive there are somany opinions on this?

the engine is designed to be running at the same temp. ie termastat.

opening the hood is like opening your house door on a cold day....hello people, do you feel colder by the door when it is open, or closed?

of course it will help cooling!!!!

man oh man, people with 1000's of posts, do you like seeing your writings on the net??? or are u disability or something?

My Knighsports hood and the decision
process I went though and notes on my installation
http://www.negative-camber.org/crispyrx7/hood.htm
Regards,
Crispy

Awesome Crispy! - thanks!

Great write-up and awesome work done on the hood Crispy! The only thing that I don't understand is that with the rain guards in place, it doesn't look like the hood vents very well. Am I missing something here? Is there a certain amount of space between the hood and the guard that lets air though? Or do you just remove the guards when you go to the track?

That's the biggest crock of shiet i've ever heard of.

How many people here, who don't think vented hoods work, actually worthwhile aftermarket temp gauges?

itRx7,
Rainguards are for "winter" use only. They are removed for track use and during the summer.
I Also run a Mazdacomp radiator, full ducting, water wetter and in the summer a drilled T-stat.
In the winter with the hood and drilled T'stat
during highway driving I couldn't even get enough heat into the motor to get the car out of warmup mode, i.e., less than 75degC indicated by the PFC. So in the winter I pop the vent covers back in and switch back to an undrilled T'stat.
FWIW
Crispy

My Mazdaspeed knocked 37 degrees off my intake temps

Anybody have more pictures/purchase info on the Odula or Stout hoods?

Seen a couple of pictures, and those look to be one of the least overboard hoods I've seen.

Tried google, but can't find either of their home pages.

Nobody else noticed in that article it mentioned bigger radiator fans with more fins?

http://www.odula.com Hopefully be ordering my Odula hood soon. :)

I have the hood by Atihun, a Mazdaspeed look-alike I believe, and although I have no way to measure exact degrees my '93 definitely ran cooler. The one thing that surprised me and was a great bonus was the temp in the passenger cabin was noticeably cooler. In the summer it doesn't get so heat soaked and is definitely cooler. By the way, whenever I park my car in a protected place (my garage, secure at work) I raise the hood to let out the hot air, unless it's raining. At home I even have a fan that is plugged into a Radio Shack switched outlet with a RF remote control. When I pull in my driveway I click the garage opener, then I click the radio shack remote and the fan comes on. I pop the hood and pull in my spot and turn all off. The turbo timer runs for a minute. Meanwhile I'm raising the hood. In the winter I don't want to leave the door open so I don't run the fan, just raise the hood.

The Atihun / Mazdaspeed design is great.

Thanks for the good word! We still sell the Mazdaspeed Replica hoods.

I live in Southern California, so it gets warm here. When I drive with our vented hood, my intake temperatures are lower as well as my engine temperatures. The differences are noted by the numbers on my PowerFC.

Also what is nice, is that if I sit in traffic, the temps don't go as high, and they decrease much faster once moving again.

When I get a datalogit, I will setup a test and record all results for those that do not believe.

You can find more information on the hoods here:

www.atihun.com

Thanks,

did mazdaspeed hoods ever come in CF or were the Cf ones only replicas (note: I dont care if it was or not and it should not matter if it was made well, just wanted to know for my own info)

thanks

SCOOT HOOD COOLED ME DOWN 12 DEGREES