Deck Lid Stand-off -- which is better, Top or Bottom

[Jason Foster]

  Nice belt Harold.....

[neil68]

Something to note, I have a late model decklid with 4 rows of vents across. If you have a early car with no vents you might have suction from the bottom where in my car air flows in the vents and out the bottom.

Very good point, Glenn.  You're probably fine with those extra lid vents, whereas I have the solid '68 lid, hence my concern about airflow at certain speeds...

[carlito421]

I think I'll made this one







<a href="http://www.youtube.com/v/fZRGqGDQtpI" target="_blank">http://www.youtube.com/v/fZRGqGDQtpI</a>

[Georg/DFL]

I think this is one (if not THE) most discussed question regarding better cooling for an aircooled engine of all time! 

When I asked that question like 20 years ago the first time, everybody told me to use stand offs at the top. That should bring cold air in the engine compartment. Poping it off at the bottom allows heat from the exhaust going into the compartment. But then other people tell you the story the other way round.

In my opinion there are to many "should" and "would" and "might" in there. No one really knows what the air around a Beetle does! We will not know it before someone is bringing a car into a wind channel. And then you have to check different lids: convertible lids, solid lids, bla bla bla.

Only solution: Try it! Read the figures on your oil/cylinder head temp gauge and pop it where it is most effective. Everything else is GUESSING!

[BeetleBug]

Good one Georg, you have the German approach.

On my old 2221ccm NA engine I had a hard time getting any oil temperature at all, no matter what. Original dog house oil cooler. Open lid at the top. Closed the lid and I managed 70C on a hot day standing in a traffic jam on my way home after a race. As soon as I got going again it dropped to around 60C.

Where does the airflow stop following the roof shape of a beetle? And would it not be a good thing that the fan is sucking in fresh air no matter what?

What I do know now with a temp sensor in the engine department (placed at the top, behind the fan house) is that I have 50C inside the engine bay no matter what temperature it is outside. Opening the lid at the bottom does not change the temperature inside the bay at all. Remark: I`m running complete rubber seals and have the bay sealed close to stock style. I do NOT have my exhaust header running behind the engine like most of us and my turbo is sealed off with a very effective heat blanket.

[qubek]

Back in the days, we used to run these ... Eventually I just got tired of the look and having to use some implement to prop the decklid open.
The reason we used them was it was the most effective way to evacuate the heat (it rises you know ...) when the vehicle was stopped or parked to keep from vapor locking when taking off again, plain & simple.
TxT

Plain & simple? Still doesn't explain anything. I remember seeing that being done in the seventies and never understood why. If it were effective for something useful, VW's engineers would have most likely done something along those lines. Thankfully... a few people, including Gene Berg, decided to go a more functional route by standing off the bottom, slightly. Plus it's way easier on the eyes and actually serves a purpose.

Again, to each their own.

But VW engineers did not make a bottom stand off either. What they were doing was implementing more and more cooling vents in the lid.

I agree with Georg that until someone does extensive tests (wind tunnel included) it is hard to tell more than "I do it like that and it works (or at least seems to work)".

There were a simmilar discussions in Poland involving air-cooled Fiats. Proping the lid at the top used to be very popular, even though it was proven (or almost proven) to be counter-effective. But cooling in Fiat works in a different way then in a Bug and basing on this, I would say that top stand off in a Bug should work. But this is just my theory.

The problem is that my experiences are inconclusive. I suppose to many factors are involved to give a simple answer.
My girlfriends Bug (totally stock 1600 except from 2 dellortos) reacts well to proping the lid ad the bottom. The temperature drops noticeably. But this car has stock exhaust and decklid without vents (it used to be 1300). And for a 1600 with a dog-house cooling - it should have vents.

Same thing does not seems to work in my 1915cc. this engine generally works cool and does not seem to need any kind of stand offs. I used to have them at top and now I sometimes use tennis ball like Glen does but I cannot tell if it makes a difference at all.

Interesting thing is that while the 1600 (and stock engines I used previously) run hotter while driving fast and get colder while the car is stuck in traffic, my 1914 reacts in an opposite way. It is the hottest while standing still in heavy traffic. I have to drive really hard (race track, high speed highway sprint - a long one) to match this.

The conclusion - while there will be a lot of people defending the way they personally do things (obviously - this is a general low of internet forums ) the case may be a little bit  more complicated than it seems at a first glance.

[Cornpanzer]

I think a lot of people forget that there has to be air-flow to make a difference.  If you only provide a theoretical "exit" without and entry point, you will have no more air-flow.  Its just like your house.  If you open one window, not much happens.  Open a second window and you get air movement.

The factory started putting extra vents in the decklid as the engine size and fan size grew.  These vents supplied extra air to the fan which then exited out the bottom of the engine.

By popping the top of the decklid open, you provide a new source of air, but you really haven't provided an exit.  In my uneducated opinion most of the benefits come from the gap allowing heat to escape via radiation (perhaps convection is the better term??)

If you make an air inlet at the front of the engine compartment and pop the bottom, then you allow a movement of air across the engine.

Of course this is very unscientific, but the theory seems sound.   

[Jon]

Some say you can't even fit a 1600 in a 1200 car without getting vents in the lid. As there won't be enough air, I guess they think it will be making a vacuum or something? However on the convertibles VW got rid of 50!! louvers above the engine lid and replaced it with 10 slightly longer ones in the convertible lid.

[TexasTom]

Duh ...
Dude,
I think you may have a small problem with cognitive reasonoing ...
I suggest a brew ...
Take care,
TxT

HAHA!! Um... if you're joking, Tom, it's pretty funny. If you're not... even funnier. Welcome to the real world. There's a little thing called having our own respective opinions towards everything. I have zero problem(s) with cognitive reasoning (I think that's what you're trying to spell). At any rate, have a fantastic evening and if, in my travels, I decide to enjoy an ice cold barley pop... I shall hold it up in your honor.

FRED!
YES! ... kidding.
Sorry for the jumbled typing and ineffective editing.
What I was trying to say/describe was that we needed to do it ... On my '69 (no vents in the decklid) we had problems with vapor locking back in the early days. Probably running 10:1 back in the day when the gas was good. Also, later, carb clearance was an issue with the 48s and tall manifolds and there was NO WAY I was cutting the stacks! LOL
Also, some of our customers also experienced vapor locking and the stand-offs helped very much!
Truth be known, I also thought the look was pretty cool and still do on the right car ... Now, the classic look appeals to me more.
Either way, hope you enjoy the day.
TxT

[Fiatdude]

Well, I guess I'll be the testor on this one, but my experience probably won't mean much to most of you since I will not be using any of the sealing tin in the engine compartment, and I have a 2919 with siamese cylinders, and a turbo BLAH BLAH BLAH. But I do have head temp sensors installed (to make the EFI happy) and I will try both ways and see which way makes the engine the happiest or the coolest

[Peter Roberts]

Bottom standoffs do help the temp drop .

Top ones drop it even further .

I have a guy ( Ash ) , his 67 Bug , with a 9.5 to 1 comp , Engle 125 cam , 1914 cc IDA motor . With a standard ratio 1500 gearbox ( Rancho Pro-Street )

With a bottom standoff , a Type 2 rubber rear bumpstop , pushed over the lock latch , spacing the bottom of the decklid ( non vent type )  out 3 inches , the engine temp runs at 210 f , at constant 80 mph .

With Bugpack top standoffs fitted , runs at 180 f at same speed .

The car ran 14.6 with the bottom standoffs , 14.2 with the top standoffs , same driver and track .

With the top standoffs , you are not shutting the decklid across the No 2 and 4 cylinder carb stacks , interupting airflow to the IDA trumpets , which may go to explain the better performance . Plus Ash said it felt quicker with the top standoffs .

On top of this , go for a long drive , along freeway / motorway sections , and some dusty side roads . Then stop , open your decklid and wipe your clean finger around the inside of the carb trupet . You will find that your finger gets all black and grimy , from crap that the tyres and exhaust kick up , that has been sucked into the engine . Not such a problem if you run air filters , but with IDA's with stacks , all that crap went through your engine 

Try the same with top standoffs , and they stay pretty spotless . You do get some yellow fuel standoff moisture ( this is what the grit and dust sticks to ) , but it is pretty clean .

That's my observations and real world experiences .

And I have tried the same on other guys cars .

[TexasTom]

Real life results ... pretty cool
Excellent data.

The bump in power is pretty remarkable ... Assuming all else is the same, that's about a 10-11hp increase with 'unobstructed stacks'!
May be worth looking into ... 
TxT

[Jesse/DVK]

What about no decklid at the track?

I like the look of the bottom open more than at the top and it is easer here in the Netherlands with all the rain

[Peter Roberts]

Some of the increase in track et , may be down to the track conditions , Santa Pod varies in track prep , depending on what is running on a specific weekend .

Every single Bug that I have tried top standoffs on has run quicker et's , maybe a coincidence , but a strange one if so .

I'm more concerned about the dust going through the engine with bottom standoffs .

Oh , and i use phenoilc spacers on the carbs , to combat the vapour lock situation .

[volkskris]

there is already an underpressure at the bottom of the rear window, so air would be sucked out at the top too.

[glenn]

[Fiatdude]

that car needs a roof rack LOL  -- great picture Glenn -- what was speed in thst picture??

[Zündfunke]

...when the front is lowered the airstream reaches the decklid just right! 
So: Stand off at the top! 

[Zach Gomulka]

...when the front is lowered the airstream reaches the decklid just right! 
So: Stand off at the top! 

Took the words out of my mouth!

[TexasTom]

Love to see a view from the top to see the flow around to the rear window/decklid area .
Very cool photo!

[glenn]

that car needs a roof rack LOL  -- great picture Glenn -- what was speed in thst picture??

No idea... found it on Google.

[danny gabbard]

I think I'll made this one







[youtube]http://www.youtube.com/watch?v=fZRGqGDQtpI[/youtube]

Very cleaver, And you can adjust the gap that you want.

[Fiatdude]

Well -- During the mock up stage -- I moved the innercooler around several times and thought I had found the sweet spot where everything would fit --- missed it by this much -- the return intake pipe from the inner cooler hits when I tried to put the deck lid on in the stock position by about 1/2" -- So I guess I'm stuck with the 2" top stand-off until I decide to redo the piping

[SCOTTP]

I'm thinking with that fan housing and the rest of the missing tin, it isn't going to make any difference.

[pupjoint]

personal opinion

i hate the look of popping the top.

mine is popped at the bottom, stock engine though for now

[58vw]

i like the bottom look also...although mine is popped at top...pesky carbs and breatherbox in the way...

[H67bug]

Anyone got pics how these hinges look installed?
[/quote]

I am sure Hayden (H67) from the greenhearts either ran or has a pair.
[/quote]

Hi

Yep have them installed. Pics not required - it looks stock when they are closed and like it has stand off the rest of the time.

Takes 10 seconds to open the stand offs when swapping from one to the other. Fitting in the first place was tricky for mine.

I tend to run with the lid in stock mode unless it is hot. I have tried the bottom prop and it does not cool the engine like stand offs- about 15 celsius difference.

[Kaferdog]

So does this mean the Herrod Helper means has no effect..?......

[Fiatdude]

The guys on the salt have proved that they help a lot -- a stock bug gets up to almost 135 mph and things get real squirrely -- the record for a stock bug is 132 -- just adding a helper and they have gone over 150

[Zach Gomulka]

Maybe in HIGH speed situations they work, but on a street car all they do is raise the oil temps.