Cooling - Are these scoops any good?

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jstoezel
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Cooling - Are these scoops any good?

Post by jstoezel »

Hi,

I thought I had already seen a long thread about cooling in this forum, somehow I can't seem to find it anymore.

Last summer I ran what is pretty much a brand new engine, from a builder that has won the runoffs recently. The engine is very powerful, at least compared to the rest of the field here. I started by using Mobil 1 10W30, then switched to Mobil 1 15W50 after the first 2 races as the engine builder said the 15W50 contains chemicals supposed to protect these kind of old engines.

During the first 2 races we raced in the rain, with an ambient temperature of 15-20C (60F). The engine was reaching 220F after 10 laps, from what I understand this is perfect.
For the following races we had dry and hot weather, in the 25-30C (80F) range. My engine would consistently hit 260F after 10 laps, to the point where I had to short shift and lift on the straight.
We run at Gimli, a relatively short track, with 9 corners and a straight a bit longer than 1/4 mile. From the time I would start accelerating at the beginning of the straight, to end, I could see the engine temperature climb from 250 to 260F.

I run a lynx B, this is the type of cooling scoops that came with it

[ external image ]


I was told I need to add a fin inside the scoop so the front cylinders don't end up being starved from fresh air

[ external image ]
[ external image ]

This is my car
[ external image ]

Since this picture was taken, to improve cooling I have added a snorkel type scoop behind my head, and a duct going front the top of one of the head cooling scoops directly onto the oil cooler, I have replaced the 6 units cooler to an 8 units cooler (those found on the bus, this is the one).
The oil cooler is positioned vertically on top of the engine, interestingly the fins are oriented left/right, perpendicular to the crankshaft.

With these modifications I would hit 250F at the end of a 15 lap race on a hot day, and still had to short shift to stay there.

At the end of the summer I sent my engine for a rebuilt and apparently there was evident signs of overheating.


What would you recommend to lower the engine temperature?
Are these scoops any good?
Do they need to be modified as shown in the pictures?
Any other idea?

Thanks,
Jean
Jean-Sebastien Stoezel
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brian
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Re: Cooling - Are these scoops any good?

Post by brian »

The biggest problem with most scoops is that they fit poorly. Air, like most things in nature, will follow the path of least resistance. If your scoops are sloppy around the cases, the air will run off and not be forced to turn down into the cylinders and heads. I would suggest asking on the forum if anyone has scoops for sale. The original Lynx scoops are among the best. I also don't recommend enclosing the intake manifold in the scoop since it tends to heat the intake too much. You can start with the original VW cylinder sheet metal and build a scoop the enters from the top. If you have a scoop on the top of the body, you may want to direct it to the cooler and leave the head scoops to do 100% cylinder cooling.

Some recommend installing a larger oil cooler but that will only mask the real problem by reducing oil temps while the heads and cylinders are still too hot.

Assuming that the heads are running cool enough, I prefer my temps not to exceed 240 on a hot day. High temnperatures can be really challenging for our motors and temps above 270 will mean disaster for our aluminum main bearings. One final thought, but probably not an issue since you have professionally built engines, is ignition timing and fuel mixture.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
jstoezel
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Re: Cooling - Are these scoops any good?

Post by jstoezel »

Hi Brian:

Thank you for taking the time to provide a detailed answer.

It becomes clear to me that these scoops are not optimum, since they seat at 90 degrees with the cylinders. I can see what you mean when you say that only a certain amount of incoming airflow is redirected in between the cylinders and the heads.
Other people at the track run with similar scoops, excepts they make a 45 degree with the cylinders, like the ones on the blue car in this picture

[ external image ]

I am guessing that the scoops I currently have are not original Lynx scoops. What do original lynx scoop look like?

Does anybody have scoops for sale? Or even just the pieces that wrap around the cylinders and the heads?


brian wrote:The biggest problem with most scoops is that they fit poorly. Air, like most things in nature, will follow the path of least resistance. If your scoops are sloppy around the cases, the air will run off and not be forced to turn down into the cylinders and heads. I would suggest asking on the forum if anyone has scoops for sale. The original Lynx scoops are among the best. I also don't recommend enclosing the intake manifold in the scoop since it tends to heat the intake too much. You can start with the original VW cylinder sheet metal and build a scoop the enters from the top. If you have a scoop on the top of the body, you may want to direct it to the cooler and leave the head scoops to do 100% cylinder cooling.

Some recommend installing a larger oil cooler but that will only mask the real problem by reducing oil temps while the heads and cylinders are still too hot.

Assuming that the heads are running cool enough, I prefer my temps not to exceed 240 on a hot day. High temnperatures can be really challenging for our motors and temps above 270 will mean disaster for our aluminum main bearings. One final thought, but probably not an issue since you have professionally built engines, is ignition timing and fuel mixture.
Jean-Sebastien Stoezel
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billinstuart
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Re: Cooling - Are these scoops any good?

Post by billinstuart »

Don't discount the amount of oil cooling contributed by the CASE itself. Different chassis/bodies affect air flow around the case differently. Head temperature is important for performance, but may not be a huge factor in oil temperature.

Are you sure oil is going thru the cooler..have you stretched/modified the oil bypass spring?
jstoezel
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Re: Cooling - Are these scoops any good?

Post by jstoezel »

Well pretty much I treat the engine like a black box. It's sent to the shop in the winter to get rebuilt, and I use it thorough the summer. I do not modify anything in it, I did not even remove the plugs last summer.

So no, I haven't modified the oil bypass spring. I believe my engine builder would have mentioned if there was any issue with this. I was built from scratch last winter, so it's pretty much a 1 year old engine.

billinstuart wrote:Don't discount the amount of oil cooling contributed by the CASE itself. Different chassis/bodies affect air flow around the case differently. Head temperature is important for performance, but may not be a huge factor in oil temperature.

Are you sure oil is going thru the cooler..have you stretched/modified the oil bypass spring?
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brian
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Re: Cooling - Are these scoops any good?

Post by brian »

Since you have a good engine builder, don't worry about the side issues. Your car will run cool, as is, with efficient scoops. Concentrate on controlling the air flowing to the engine. Your scoops are copies of the Citation system used years ago and were originally angled upward to capture cleaner air. This design was later abandoned for more conventional square intakes. The Lynx style scoops are larger and have a radiused entry. A real key in helping a scoop do it''s job is to have a radiused leading edge. Even splitting some small tubing and glueing it to the leading edge will help clean up the air and reduce inversion.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
billinstuart
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Re: Cooling - Are these scoops any good?

Post by billinstuart »

Lotsa people don't understand the function of the front pressure spring on a VW case. Low oil pressure lets the piston cover the passage to the bearings, and forces all oil through the cooler. As the pressure increases (theoretically COLD engine) the direct passage to the bearings is exposed, essentially bypassing the cooler. In extreme case the piston exposes a 3rd hole that dumps oil to the crankcase to limit pressure.
CitationFV21
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Re: Cooling - Are these scoops any good?

Post by CitationFV21 »

Oops, my reply vanished!

First - are the scoops tilting in the picture - they might be lifting enough to allow air to leak out. My Citation has a brace that goes from scoop to scoop to keep this from happening.

Are you running the deflectors under the cylinders?

On my old Lynx, I put deflectors in front of the heads to create a low pressure area at the back of the engine to help pull the air through.

Which oil cooler are you running? Original Beetle or "dog house" cooler? Do you have a picture of the engine complete and installed?

ChrisZ
jstoezel
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Re: Cooling - Are these scoops any good?

Post by jstoezel »

The scoops are probably tilting in the picture. They fit around the cylinders loosely, and they're held in place using tie raps, around the intake manifold.
I realize that if they're not held in place firmly they may lift with speed, and it may explain why the engine is overheating at a higher rate in the straight.
I never thought of it more than that, the car came like that...


I'm not running any deflectors under the cylinders. Do you have any pictures of what these look like?

This is the oil cooler I currently use:
http://www.cip1.ca/ProductDetails.asp?P ... -117-021-B

This is an old picture of the car when I got it, with the old engine, when the small 6 unit oil cooler was installed. I don't have a recent picture of the engine bay, and the engine is about 600 miles away, still at the shop.

[ external image ]


CitationFV21 wrote:Oops, my reply vanished!

First - are the scoops tilting in the picture - they might be lifting enough to allow air to leak out. My Citation has a brace that goes from scoop to scoop to keep this from happening.

Are you running the deflectors under the cylinders?

On my old Lynx, I put deflectors in front of the heads to create a low pressure area at the back of the engine to help pull the air through.

Which oil cooler are you running? Original Beetle or "dog house" cooler? Do you have a picture of the engine complete and installed?

ChrisZ
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CitationFV21
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Re: Cooling - Are these scoops any good?

Post by CitationFV21 »

Here is a site that shows the air deflector (got to scroll down)

http://forums.dieselstation.com/lofiver ... 87-50.html (Dec 19 2008, 10:44 AM)

They are between the cylinders and the pushrod tubes

Also, it looks like the wires go in between the block and the scoop, this leaves a space for air to escape. I run them under the manifold. I also don't like how the scoops are held onto the manifold. This may allow then to shift

I think you will get more than enough air if you can seal all the leaks and the scoops don't move.

If not, see if someone has the Citation elephant ears you can borrow.

It looks like your oil cooler is okay, but you might not be getting enough air to it.

Here is someone who is using a NACA duct http://s789.photobucket.com/albums/yy17 ... c10044.jpg

But most of the time you just have to get some air flow under the deck.

Chris Z
billinstuart
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Re: Cooling - Are these scoops any good?

Post by billinstuart »

1) What cylinder head temperature do you run? I don't believe you have a head cooling problem.
2) That oil cooler should be more than adequate for any vee engine. With enough airflow around the case, you don't need an oil cooler.
3) Do you have a streamlining panel that covers the bottom of the engine?
jstoezel
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Re: Cooling - Are these scoops any good?

Post by jstoezel »

Hi ChrisZ:

Thanks for the detailed answer.

The air deflector are a bit counter intuitive to me. You plug the big opening in between the cylinders, and this creates a depression around the wiglets, at the rear of the plate. And this forces the airflow down from the scoops?

Ok I will work on getting the scoops to fit better and tighter.

Since the picture was taken I modified the rear bodywork on my car, with 2 openings behind the helmet, on each side. They look similar to this openings seen on the BRD. This didn't seem to help with cooling. I've also installed a snorkel on top of the carb, as I though it might help. Eventually I had a flexible hose connected to the oil cooler, and this seemed to allow running in the 240-250F on a 80s F day.

Where can you find these NACA ducts?
CitationFV21 wrote:Here is a site that shows the air deflector (got to scroll down)

http://forums.dieselstation.com/lofiver ... 87-50.html (Dec 19 2008, 10:44 AM)

They are between the cylinders and the pushrod tubes

Also, it looks like the wires go in between the block and the scoop, this leaves a space for air to escape. I run them under the manifold. I also don't like how the scoops are held onto the manifold. This may allow then to shift

I think you will get more than enough air if you can seal all the leaks and the scoops don't move.

If not, see if someone has the Citation elephant ears you can borrow.

It looks like your oil cooler is okay, but you might not be getting enough air to it.

Here is someone who is using a NACA duct http://s789.photobucket.com/albums/yy17 ... c10044.jpg

But most of the time you just have to get some air flow under the deck.

Chris Z
Jean-Sebastien Stoezel
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jstoezel
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Re: Cooling - Are these scoops any good?

Post by jstoezel »

billinstuart wrote:1) What cylinder head temperature do you run? I don't believe you have a head cooling problem.
I don't know I didn't have sensors last year. I bought sensors since then and I will be running them this summer.
billinstuart wrote:3) Do you have a streamlining panel that covers the bottom of the engine?
No. I'm glad I didn't have any of these last summer, as my engine was leaking a lot of oil from the poulie (even with minimum oil in). This would have collected so much oil... Over the winter my engine builder has installed a seal there, and also fixed the poulie, which was evidently wrongly modified, and was allowing oil to pass through.
Does a streamlining panel help with cooling?
One thing that is a bit different on my car, compared to the other ones that I've seen here: The engine is very close to the firewall, when I say close I mean there's less than 1/2" clearance between the poulie and the firewall (the firewall was intentionally indented to create this clearance by the way).
The firewall is very close to the engine, and my guess is there's not much air movement in between. I think all the heat is reflected back to the engine too. All the other lynx at the track have at least 1.5" clearance.
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Re: Cooling - Are these scoops any good?

Post by smsazzy »

The air deflectors I do not believe are needed either. (inside the scoop) They are needed under the cylinders.
As long as the backside of the scoops fits snuggle onto the heads of the engine.

If you think about how the scoops work, they essentially fill up with air and then the air stops. As more air is forced into the front of the scoop, positive pressure builds up. The air insode the scoops is then pushed out in the path of least resistance first, then through openings with less and less resistance until an equilibrium is found.

As long as enough air travels over the heads, you're fine.

The orientation of these scoops shouldn't be a problem. The 90 degree nature works just fine. Look at the Vortech. They are 90 degree oriented scoops and that is largely considered the best at head cooling.
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Re: Cooling - Are these scoops any good?

Post by tiagosantos »

My right side scoop is split and fits snug over both the head and the oil cooler.. Looking at your picture, I would think you need to find some way of forcing air through the oil cooler..
jstoezel
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Re: Cooling - Are these scoops any good?

Post by jstoezel »

These are the only pictures I could find, where there's a different angle on the cooling scoops. They were taken last summer. Note the extra piece of duct I was running on top of the right cooling scoop, to blow air directly onto the oil cooler. This helped going down to 250F.
These are not the best pictures, but that's all I have for now.

Note how the scoops only covers the top of the heads, no the sides... From previous discussion it sounds like air could escape on each side of the heads, since the scoops only covers the top of the heads. What do you think?

View from the rear
[ external image ]

View from the front
[ external image ]








smsazzy wrote:The air deflectors I do not believe are needed either. (inside the scoop) They are needed under the cylinders.
As long as the backside of the scoops fits snuggle onto the heads of the engine.

If you think about how the scoops work, they essentially fill up with air and then the air stops. As more air is forced into the front of the scoop, positive pressure builds up. The air insode the scoops is then pushed out in the path of least resistance first, then through openings with less and less resistance until an equilibrium is found.

As long as enough air travels over the heads, you're fine.

The orientation of these scoops shouldn't be a problem. The 90 degree nature works just fine. Look at the Vortech. They are 90 degree oriented scoops and that is largely considered the best at head cooling.
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Re: Cooling - Are these scoops any good?

Post by smsazzy »

Vortech scoops cover the top half of the head. As do the stock cooling tins. As long as air is going through the fins, it is cooling.

I would be more concerned with air going out the gaping hole where your manifold enters.
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Re: Cooling - Are these scoops any good?

Post by brian »

If you think a moment about where the majority of heat is generated, you'll realize that the head and cylinders are responsible for almost all of it. Keeping those components cool is critical. While oil plays a very important role, the VW engine is still an AIR COOLED engine. It appears that you will be concentrating on the scoops and that will get you the greatest results. Dyno studies have proven that heat temps over 350 f will reduce hp. Temps over 450 will spell disaster. Ducting to the oil cooler is another opportunity. The flex hoses from the hardware store, while a short term fix, do not carry air very far before loosing air speed due to drag inside the hose. If the top of the body has an opening, I'd try ducting from there to the oil cooler.

I see that your duct is very close and almost behind the trailing arms. The trailing arm could very well be deflecting air away from the scoop. The Lynx scoops, which were made for your chassis, were higher. The front exhaust pipe is shielded from air flow as well. Heat from this pipe can exchange through the push rod tubes and actually heat the oil while it returns to the cases. It that pipe is close to the push rod tubes an aluminum deflector could help. Speaking of deflectors, the cylinder deflectors I mentioned are designed to force air under the cylinder and provide cooling for the shielded bottom.

Regarding the bypass spring, I do not recommend modifying them. The next time you start the motor, touch the cooler occasionally to see how quickly it starts to warm up. If the cooler starts warming up quickly, the oil is flowing. With vee motor clearances, the chances of the oil bypassing is not very likely unless it freezing outside or there is a stuck piston. In which case the cooler won't warm up very quickly. VW put the bypass system in place to avoid popping the cooler with really cold, high pressure oil. Since I have a full flow oil system, I use the piston that allows oil to flow all the time.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
hardingfv32-1
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Re: Cooling - Are these scoops any good?

Post by hardingfv32-1 »

Oddly enough, adding a bell mouth to front of the scoops will really help flow quality with minimal drag increase.

You are going to have to do a little better than what you have to get better oil cooling. The quality of cooling you get is going to be proportional to the effort you make fabricating the proper pieces.

Brian
CitationFV21
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Re: Cooling - Are these scoops any good?

Post by CitationFV21 »

To clarify my remarks:

The cylinder deflectors that go under and between the cylinders are to deflect the air around the cylinder for even cooling.

The other deflector (if needed) is to keep air from ramming into the bottom of the cylinder and stalling the air flow:

http://pages.cthome.net/czracing/FV/cool0001.gif

If the front edge of your scoop is long enough (the side that covers the front of the cylinders by "B" in the drawing) then you should be fine.

Getting air to the cooler is good, as long as it has a place to go.

Pegasus has the NACA duct http://www.pegasusautoracing.com/produc ... oduct=3628 for example - maybe one of the FV suppliers has it also?

Smooth tube would be better than what you have to the cooler.

Keep plugging leaks. Think at speed what forces may move the scoops.

ChrisZ
CitationFV21
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Re: Cooling - Are these scoops any good?

Post by CitationFV21 »

Looks like this person has the same scoops and opened them up a bit:

http://www.flickr.com/photos/37647933@N ... /lightbox/

ChrisZ
billinstuart
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Re: Cooling - Are these scoops any good?

Post by billinstuart »

It is indeed important to cool the heads..much moreso than the jugs. Often too much air is dumped on the cylinders, and not forced through the head fin passages. If you have abnormally high head temperature, address that issue first.

Look at you heads closely. Are the passages filled with stones/rubber? Often flash from the mold blocks the passages..drill or grind this off. Block off air to the cylinders, and force more air through the heads.
jstoezel
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Re: Cooling - Are these scoops any good?

Post by jstoezel »

As a follow up to this issue, I am now using the original Lynx cooling scoops (the long ones, with the square opening) and I am running around 210F on an 80F day. And I don't even use the additional piece of vent duct to cool down the oil cooler.
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brian
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Re: Cooling - Are these scoops any good?

Post by brian »

Congrats Jean, kill the source of the heat at the heads like you did and you won't have to work so hard to cool the oil.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
jstoezel
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Re: Cooling - Are these scoops any good?

Post by jstoezel »

Hey thanks Brian!

We'll see how this works for tomorrow and Sunday's races (6 races total 2 practice and 1 qualifying session). Temperature is supposed to be around 32-35C (mid 90s F) with no wind.

An added motivation to get to the fresh air at the front.


Jean


brian wrote:Congrats Jean, kill the source of the heat at the heads like you did and you won't have to work so hard to cool the oil.
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