School me on engine lids... [Archive] - Toyota MR2 Message Board

School me on engine lids... [Archive] - Toyota MR2 Message Board Toyota MR2 Message Board > Toyota MR2 Generations > MK 2 MR2 - SW20 > MK2 Body Kits and Exterior Modifications > School me on engine lids... PDA

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koji12-02-2009, 10:38 AMI'm reasonably new around here but I'm getting ready for an exterior makeover project and could use some help. The goals will be to lighten some of the body panels by replacing them with fiberglass bits (which I'll be making). The front hood and the rear trunk are pretty easy conceptually - it's the trunk lid I need to know more about.

I'm eventually going to be swapping in a 3SGTE so keep that in mind.

Here are my questions:

1. I see that the Turbo models have raised veins on the trunk - is this for airflow/to fit fans?

2. Which way do the fans blow? Are they pushing air out or sucking it in? I have a guess but I'd like to be sure.

3. The big lids that I see with huge openings towards the rear of the car - why do people use these? (apart from looks) Is it just to allow the fans to evacuate/suck in more air or is there some other benefit?

Thanks!
Koji Tagg6712-02-2009, 11:46 AMNot sure about all your questions, but looks like the Turbo engine lids on the MK2 do have fans, and they blow the air from the engine out through the top of the lid. The 2nd photo is of a SC MK1 Lid and it does not have a fan, but notice that the Air intake is just below the hood vent, which may indicate that the air is drawn in vice out? Anyone else like to comment on the photos please do so.
Hope this helps.

Tagg Sh0ty12-02-2009, 12:19 PMThere was never a SC MKII. The fans blow air out the lid, and the air source comes from the bottom of the engine bay (notice how it isn't sealed?) to keep ambient tempurature down. If you want to increase airflow, the fans would help a little, and possibly some sort of flap designed to bring air up through the car would as well. I'm not sure about the raised slats being used to house the fans, but you'd be fine using a non raised engine cover if you're just concerned about engine heat. The slats are a good way to identify a turbo car though, and it's nice to be recognized for it if you're into that kind of thing.

Personally, I think the NA cover looks better, and I plan to stick with it after my engine swap (hopefully a 2GR or 1MZ, but I'll settle for a 3VZ). If you're making composites, have you thought about carbon fiber? It's lighter than fiberglass and you can always paint it if you don't like the look. koji12-02-2009, 12:43 PMI've made things with CF before but I don't have a vaccume baging setup big enough to do an engine lid. Thanks for the info. brianbooth12-02-2009, 01:12 PMI'm pretty sure that the engine lids didn't come with a stock fan built into them. Some folks like to add them but it's not necessary. Or at least that's what the temp gauge on my car tells me :) Sh0ty's right about the air flow - it goes from bottom to top, at least when you're stopped. When you're moving air flow isn't a problem. CJMR2T12-02-2009, 01:34 PM1) thats a good question. There were no fans factory installed. What makes it even more interesting / confusing is that if you look closely at a factory turbo lid, you'll notice that the slats / openings are opposite from left vs. right. IIRC withough going out and looking at my car, the left side openings face forward and the right side face rearward.

2) If you install fans, they need to blow outward. as a side note, the notch back design is kinda a bad idea for a mid / rear engine car. For that matter its bad for any car from a aero standpoint.. The area in the notch (engine lid area) is actually a pretty stagnent when it comes to airflow.

3) The aftermarket lids that you are refering to are really nothing more the astecitics I have never seen any proof of them being benificial. About the only real benifit would be that they are probably the best at keeping water out.. If you really want to build something that would be benificial in more then one way, (something I've been wanting to do too) is build a clear luvered panel the closes the notch back area (C piller to C piller, roof to trunk) thus making it a slant back. This would help the Aero of the car pretty significantly and the better aero over the engine / rear of the car would help pull air through the engine bay... A perfect examply of this is the Ferrari F40 (probably one of the best road going race cars ever built)... Sh0ty12-02-2009, 07:07 PMWell, in a car without the fan, then there isn't any airflow, but when moving, air does from from the bottom up, partly because of the negative pressure due to the notch back design. Medusa12-02-2009, 10:36 PMI plan on teaching myself to work with fiberglass and making a louvred cover like CJMR2T is talking about. I think it will look a lot better and help the aero noticeably. koji12-02-2009, 11:48 PMAre you guys thinking of somethign like an old skool RX-7 or something similar when you're talking about louverd sections? Are there any online examples of this? Medusa12-04-2009, 01:39 AMhttp://carpron.com/multisite/d/4527-2/toyota_mr2_white_1b.jpg CJMR2T12-04-2009, 07:11 AMhttp://carpron.com/multisite/d/4527-2/toyota_mr2_white_1b.jpg

Yep, that is a perfect example of what I was talking about....

Yes there is airflow out of the engine bay while at speed, but the whole notch back thing is bad for aero as it creates lift. With the notch back, you are creating a turbulent area of low pressure over the engine lid and trunk area. With a slant back, you pretty much eliminate the turbulance and eliminate the low pressure for the most part thus helping to eliminate lift on the back of the car while at speed. It wont really do anything for adding aerodynamic downforce as its not going to create a high pressure area on the back of the car but it will reduce lift (a high rise wing is still needed to add aerodynamic downforce as whats in the picture).

Having smooth air flowing over the luvers with pull a nice vacuum (think siphon) in the engine bay. Add in the small amount of high pressure comming in from the side vents and there should be a noticable more amount of airflow though the engine bay.

Even if the airflow is not really increased, its not going to be reduced and you still gain the advantage of the Aero over the car, thus better high speed stability and handling.... David01-24-2010, 09:41 PMKind of a slight revival, but I think you guys might be interest in these pics.

http://i7.photobucket.com/albums/y281/David1000/2008%20Spring%20Fling/HPIM1164.jpg

http://i7.photobucket.com/albums/y281/David1000/2008%20Spring%20Fling/HPIM1165.jpg

http://i7.photobucket.com/albums/y281/David1000/2009%20Spring%20Fling/HPIM1938.jpg

http://i7.photobucket.com/albums/y281/David1000/2009%20Spring%20Fling/HPIM1939.jpg mr301-24-2010, 11:21 PMWhere do I order? MRH01-25-2010, 12:33 AMWhere do I order?

gotta make ur own to my knowledge....sucks I know...

-H koji01-25-2010, 02:01 AMThat's a quality job regardless. Those fasteners are beautifully functional. You can get the right sheets to make something like that but all the machining of the vents you'd have to have done professionally at somewhere like Tap Plastics unless you've got a good router table.

After combing through the aero pages here and re-reading Tune To Win I'm thinking I'll do something like too and just skip the lid fabrication. It makes a whole lot of sense and cuts down on the size of the wing you need to use. PETC01-25-2010, 02:59 AMKind of a slight revival, but I think you guys might be interest in these pics.

http://i7.photobucket.com/albums/y281/David1000/2008%20Spring%20Fling/HPIM1164.jpg

http://i7.photobucket.com/albums/y281/David1000/2008%20Spring%20Fling/HPIM1165.jpg

http://i7.photobucket.com/albums/y281/David1000/2009%20Spring%20Fling/HPIM1938.jpg

http://i7.photobucket.com/albums/y281/David1000/2009%20Spring%20Fling/HPIM1939.jpg

That engine lid catches on fire... I've seen pictures! David01-25-2010, 08:54 PMIt was manufactured by a company, but they quit production because the plexi-glass melted, then caught fire on the hot pieces beneath. 328FTW01-26-2010, 12:59 AMIt was manufactured by a company, but they quit production because the plexi-glass melted, then caught fire on the hot pieces beneath.

Wow helpful. canadam01-26-2010, 01:17 AMWow helpful.


It was AskSport, if I recall correctly.
Sent from my iPhone using Tapatalk z Ice Dragon z01-26-2010, 01:23 AMWow helpful.

Extremely MANDALAY01-26-2010, 04:58 AMIve got a side project going on with my Rotrex SC build.
Needless to say think 360 convertible :) eckoman_pdx01-26-2010, 05:39 AMOne big difference between the Turbo and NA lids, besides the raised vents, it the OEM Turbo lid is fiberglass, and the OEM NA lid is metal.

No MKII came with stock lid fans. KO Racing sells engine lid shrouds with fans. As was said, mount the fans so the air blows out of the engine bay.

KO Racing Engine Lid Fan Shroud (http://koracing.net/viewproduct.php?folder=82&product=233)

As for the aftermarket lids with the opening towards the car rear, you are likely referring to the Phoenix Power style lids. I'd say the reason most people get them is aesthetics, but they should help keep some water out, especially with fans in the lid. It would exac the fans to the back of the car, and water wouldn't fan straight, so it may help keep some water out in the rain. Depending on the Phoenix Power lid you get, the middle bar may make it so the fans in a fan shroud have to be moved a little to the outside. I know KO Racing can custom do one though.

If you are wanting to loose weight and go with fiberglass pieces, I'd stick with an aftermarket lid or an OEM turbo lid, and then get an aftermarket fan shroud. David01-26-2010, 06:04 AMWow helpful.

Indeed. Que 328's next insane project. 328FTW01-26-2010, 06:21 AMIndeed. Que 328's next insane project.

Lol twin turbo 3vzfe mkI with top mounts. But details details:D


I wouldn't mind a back like that on my racecar being spurred on by trying to outrun a flaming ball of plastic could be a revolutionary concept. Bak@EMSPowered01-26-2010, 11:40 AMIf you're looking for maximum cooling capability an engine lid fan shroud is the way to go. Our new re-designed lighter weight aluminum engine lid shrouds are on sale: Dual 11 Engine Lid Fan Shroud (MKII) (http://www.emspowered.com/storefront/index.php?main_page=product_info&cPath=61_62_64_113&products_id=305) Archidamus-R01-28-2010, 08:32 PMIdunno why the plex melted, but I'm guessing it wasn't your average stock/semi-stock anything that melted it . . . Also, maybe Lexan would be better?

And isn't there a VENT fuse slot in the rear fuse box? Mine's empty since it's a 5S . . . CJMR2T01-28-2010, 10:45 PMIdunno why the plex melted, but I'm guessing it wasn't your average stock/semi-stock anything that melted it . . . Also, maybe Lexan would be better?

And isn't there a VENT fuse slot in the rear fuse box? Mine's empty since it's a 5S . . .

Yeah, I have a feeling that fire started else where and thats what melted the P-Glass.... P-Glass dosnt even start to get soft until about 200*f and doesnt melt till about 270*F... Lexan would be a bit better but its not much better as its melting point is about 300*F.... Hell, the F40 and F50 Ferrari's used p-glass (well the F40's had P-glass where as the F50's were Lexan) and neither have ever had melting issues...

The VENT fuse "circuit" is only used on the turbo cars.. Its for the IC (intercooler) fan circuit... Archidamus-R01-28-2010, 10:51 PMAhha, ok. I figured it was a turbo thing, but I know I've seen 2s with fans on the lids (guess they were aftermarket). Thanks for clearing that up. :) CJMR2T01-28-2010, 10:54 PMYeah, any MR2's that you have ever seen with lid fans have been aftermarket / custom installs.. They never came with lid fans from the factory... Archidamus-R01-28-2010, 10:58 PMSo, anyone think a stock MZ could breathe/chill enough under a lid like that plexi one without the vents? koji01-29-2010, 11:22 AMSo, anyone think a stock MZ could breathe/chill enough under a lid like that plexi one without the vents?

Interested in this as well since that's basically what I'm going to be doing. STLMR2na01-29-2010, 11:31 AMits gotta have the vents koji01-29-2010, 12:39 PMClearly.

The issue is do the vents need to also have a fan. I think if it's designed correctly the answer is no but you have to consider that air coming in has to get out somehow. STLMR2na01-29-2010, 12:47 PMthey don't have to have a fan but it would be a good idea Archidamus-R01-29-2010, 01:42 PMIs it? I'm unconvinced. I'm not sure what Koji has planned, but my goal right now is just a plain, unmolested VVT-i 1MZ. It looks like MR2 radiators are a bit on the runty side, but Camrys seem to cool just fine without any exotic voids in the sheetmetal (or plastic, in the theoretical context of this discussion). The vents in the engine cover are mostly covered by what look like channels to deflect rainwater onto the more watertight areas of the engine. Even the turbo model engine cover seems to have fewer open holes than the powerhungry might expect. Perhaps a few, relatively small vents or holes near the bottom might be sufficient to evacuate heat from the engine bay . . .

As far as fans, the turbo models didn't appear to have them, at least not from the factory. How much heat your engine needs to dissipate is obviously a function of how much heat it generates. I'm just speculating at this point, but I'd guess that unless you're running exceptionally high boost, fans are just bragging rights. STLMR2na01-29-2010, 01:55 PMno
here is how the 2 works

air comes into the engine bay at the bottom of the engine bay and the sidevents and exits through the lid, so fans that help air exit through the lid help the process and help keep it cooler

so they do serve a purpose and not just bragging rights Archidamus-R01-29-2010, 02:31 PMOk, I wrote a giant response, but let's call a truce. I can get a big piece of plex for pretty cheap. I'll just throw it on the waterjet and try it out. If the car gets too hot, I'll pull the thing off, limp home, and waterjet some holes in it. CJMR2T01-29-2010, 03:56 PMYeah, I would venture to say that it doesn't absolutely need vents or fans but they (at least vents) would be a really good idea....

I will add some food for thought here though. The vents do play a roll in high speed aerodynamics. So they aid in two areas (cooling and aero)...

As STLMR2na pointed out, air comes from under the car up through the engine bay and vents out the top.. Obviously this is giving you cooling (no arguments there).. This is also helping to reduce high speed lift in the rear of the car. The top rear of the car is a low pressure zone. The notch back as per stock causes excessive turbulance but is still a low pressure area... If too much air gets under the car (as most stock and even lowered cars have), lift is increased cause of the greater pressure differential between the underside and the low pressure area above the engine bay and trunk.

Having a vented lid allow for a better balance of the differential thus reducing lift. With the adding of the panel (what we've been talking about here), the turbulance in the rear is reduced thus eliminating some of the drag and it accelerates the air flow off the rear thus pulling more flow though the engine bay in attempt to balance the pressure differential...

Now the accelerated air across the top / back of the car does cause a pressure drop (meaning no downforce) but it aids in reducing pressure under the car thus reducing lift...

Aero of a car can be a pain staking task because the basic design of a car lends itself to lift and its almost impossible to eliminate lift and gain positive downforce... Designers attempt to reduce lift as much as possible in the basic design of the car and add spoilers to further reduce lift.. To actually achieve positive downforce, wings are needed. Fact that a car has a longer true lenght on the top makes it nearly impossible to generate positive downforce cause air on flowing over the top will always be faster (thus lower pressure) then the air flowing under the car..

Back to the vents in the lid, siphoning effects are at work here. The fast moving air above the car will siphon air from under the car thus accelerating it and therefore reducing its pressure, making the pressure differential closer to zero. The closer we get to zero differential, the less lift we have.... PseudoKirby02-05-2010, 06:40 PMso did it heat up? what happened?! Yozuki Ri02-05-2010, 09:33 PMSo, would a Phoenix Power lid+Fan Assembly+Bomex spoiler create more downforce or more lift? STLMR2na02-05-2010, 11:06 PMfan and spoiler would both create more downforce, would screw you over to hydroplane in the front end though Powered by vBulletin® Version 4.2.5 Copyright © 2026 vBulletin Solutions Inc. All rights reserved.