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AlteWagen
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Joined: February 23, 2007
Posts: 8713
Location: PNW
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 Posted: Sun Aug 23, 2009 12:42 am Post subject: FI oil cooler air slot |
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Just picked up a brazilia/puma and a FI dog house fan shrouds and noticed a difference in the oil cooler air diversion slot.
FI, fresh air, velocity ring
Brazilia/Puma fresh air
Thing shroud non fresh air (from gallery)
Industrial shroud, non fresh air, velocity ring (from gallery)
All are dog house style (puma with enclosed round port tube exit) off set aluminum cooler setup. Ive heard that FI cars run hotter engine temps so wondering if the smaller slot cooled the oil a bit less resulting in hotter operating temps. I believe regular fresh air dog house shrouds have the large slot like the puma and thing housings have.
The industrial shroud really made me wonder. It has in common the velocity ring and the small slot as well.
Is the small slot only for use with the velocity ring??
Do FI and industrial engines run hotter operating/oil temps?
Since the FI shrouds were the last in the line of progressive refinements for upright engine cooling, do the smaller slots and velocity rings cause cooler oil temps?? (Hotter running caused by another factor if true)
Has anyone seen a factory large slot with velocity ring setup??
I have a non fresh air puma shroud with remnants of what looks to be velocity ring spot welds and also has the large slot.
I originally bought the FI shroud for the ring and was going to put it on the brazilia low profile shroud. I am trying to maximize oil and head/cyl cooling and wonder whats considered the best factory setup.
I read the raby files on shroud cooling and understand factory is best for most applications. He also said he only did the tests with regular dog house shroud and said the thing shroud showed no significant improvement. He did not have the low profile brazilia/puma shroud available for testing at the time either. Not sure if his factory shroud had the large slot or small, velocity ring or not.
Since this means two later factory setups were not tested. Anyone running a FI or puma shroud and notice any advantages/disadvantages over regular dog house?? |
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scott s
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Joined: January 04, 2005
Posts: 1141
Location: Rock Hell, SC
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| Posted: Sun Aug 23, 2009 7:22 am Post subject: |
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I have some F.I. shrouds, a Thing shroud and a stock shroud. They all have slightly different air slots.
I don't think the shroud is what caused the F.I. engines to run hot. Rather, the F.I. engines ran hot b/c of emissions stuff and a lean a/f ratio or something...all done to meet new emissions standards. The venturi was a fix to lower the running temps.
I think any of these shrouds would work well if the engine is in a good state of tune.
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Jake Raby
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Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Sun Aug 23, 2009 9:48 am Post subject: |
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There are 3 different shrouds that are "stock" with different oil cooler partitioning..
Some have positive ducts, some have negative and then you have the 71 only Bus shroud that the majority of people don't know has its own ducting.
I tested all 3 and saw differences in the temperature of the #1 cylinder with each, those that cooled the oil best did so with a compromise of #1 CHT.
I studied fan shrouds for 5 years prior to beginning my practical application development..
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell" |
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AlteWagen
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Joined: February 23, 2007
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Location: PNW
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| Posted: Sun Aug 23, 2009 12:38 pm Post subject: |
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| Jake Raby wrote: |
There are 3 different shrouds that are "stock" with different oil cooler partitioning..
Some have positive ducts, some have negative and then you have the 71 only Bus shroud that the majority of people don't know has its own ducting.
I tested all 3 and saw differences in the temperature of the #1 cylinder with each, those that cooled the oil best did so with a compromise of #1 CHT.
I studied fan shrouds for 5 years prior to beginning my practical application development.. |
Jake thanks for replying, I know you are busy.
What is positive/negative referring to? Is it positive bay pressure like used in later busses?
Also did fresh air vs non fresh air cause any difference in temps? I would think non fresh air would direct more air to cooling the heads/cylinders.
Which seemed to be the best compromise, the hotter cylinder or the hotter oil? Are we talking a huge difference between cylinders or oil temps?
Any pics of the 71 bus shroud and ducting? Looks like another one year only part at the end of engineering refinement. Did it work any better than the rest? |
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AlteWagen
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Joined: February 23, 2007
Posts: 8713
Location: PNW
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| Posted: Mon Aug 24, 2009 3:20 pm Post subject: |
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Anyone??
I am looking for comparison data as well. If anyone has a pic of a 71 shroud I will look for one to buy and test.
Thanks |
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AlteWagen
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Joined: February 23, 2007
Posts: 8713
Location: PNW
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| Posted: Tue Aug 25, 2009 2:44 pm Post subject: |
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| scott s wrote: |
| I have some F.I. shrouds, a Thing shroud and a stock shroud. They all have slightly different air slots. |
What is the difference between the thing and regular DH air slot? Larger scoop? Longer slot? Are your FI shrouds the same as the pic above with the small peanut slot? |
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scott s
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Location: Rock Hell, SC
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| Posted: Tue Aug 25, 2009 3:33 pm Post subject: |
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This is the F.I. shroud:
This is the doghouse shroud. The Thing shroud is the same:
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scott s
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Location: Rock Hell, SC
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| Posted: Tue Aug 25, 2009 3:36 pm Post subject: |
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The last two engines I built, I used the F.I. ring on a doghouse shroud. The only reason I didn't use the F.I. shroud is because the hole for the throttle cable is offset. It was just easier to drill out the spot welds on the venturi ring and weld it on the doghouse shroud.
Both of those engines have over 9:1 CR and both cool well. One is a 190HP 2276 w/ IDA's, the other is my daily driver 2110.
The 2276 runs a T4 oil cooler, the 2110 runs a stock doghouse.
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AlteWagen
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Joined: February 23, 2007
Posts: 8713
Location: PNW
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| Posted: Tue Aug 25, 2009 5:18 pm Post subject: |
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| Is it just me or is the venturi off center? Mine looks like it is and the one in the pic is too. |
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JSMskater
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Joined: February 01, 2006
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Location: Murrieta California
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| Posted: Tue Aug 25, 2009 6:06 pm Post subject: |
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FI engines didn't run any hotter than their carb'd counterparts. it's a myth perpetuated by people who don't have a clue.
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71 Squareback-FI -- 73 Bay (subaru powered)
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scott s
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| Posted: Tue Aug 25, 2009 7:12 pm Post subject: |
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OK, guess I don't have a clue.
Instead of rolling your eyes, why don't you enlighten us all as to why they (VW) changed the ducting and added the venturi ring...as well as the extra vents in the decklid (and even a thermostatically controlled flap behind the license plate on some models)?
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JSMskater
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Location: Murrieta California
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| Posted: Tue Aug 25, 2009 7:55 pm Post subject: |
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| scott s wrote: |
OK, guess I don't have a clue.
Instead of rolling your eyes, why don't you enlighten us all as to why they (VW) changed the ducting and added the venturi ring...as well as the extra vents in the decklid (and even a thermostatically controlled flap behind the license plate on some models)? |
extra vents were added before FI, and were added as the progression of the engine evolved from small displacement to larger ones which necessitated a more free flowing source of cool air for the fan.
changing the ducting and the venturi ring is another story -- without documentation anything anyone says is just hearsay -- but I would surmise that they were changed as the product line continued and engineers continued to improve the system. Any number of reasons could have necessitated the change -- different gear ratios in the transmission, the better burn characteristics of the FI (causing it run TOO COOL if anything) and adjustments for certain markets (like CA) which necessitated for the first time items like EGR and catalytic converters. Changing fuel mixtures could also have played a part.
none of this has anything to do though with the blatantly ignorant and sweeping generalization that is constantly perpetuated by people who don't know any better: FI engines didn't run hotter by design than carb engines. They -- in general-- ran leaner mixtures but that's a consequence simply of better CONTROL over fuel delivery. This idea that "those damn FI engines run hot" is just stupid. They were never designed that way and at the time they were introduced simply flabbergasted most mechanics who'd never received training with electronic FI.
This is even MORE true of FI T3 engines -- I can't tell you how many people insist that they run hotter. they simply do not. You can ask dealer trained mechanics who worked there back in the day and they'll tell you the same thing.
Piss poor maintenance lead to a CONSUMER PERCEPTION and perpetuated MYTH that these engines ran hot.
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I make D-jet FI connectors |
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Bruce
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Joined: May 16, 2003
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Location: Left coast, Canada
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| Posted: Wed Aug 26, 2009 12:09 am Post subject: |
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| scott s wrote: |
This is the F.I. shroud:
This is the doghouse shroud. The Thing shroud is the same:
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There's another shroud. You've shown the short slot, long slot, and there's a long slot with the scoop.
And there's many more shrouds than just "3".
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AlteWagen
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| Posted: Wed Aug 26, 2009 12:32 am Post subject: |
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There is a larger scoop and slot than this?
I just read about 6 different versions of the puma, how many were there of the dog house?? Is that including industrial shrouds as well?? |
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scott s
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Location: Rock Hell, SC
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| Posted: Wed Aug 26, 2009 4:09 am Post subject: |
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I think we're beating this subject to death. Build your engine right, meaning the right cam/heads/carbs/exhaust combo, set the deck height correctly, and run the appropriate CR for your cam.
Run ALL the engine tin....every last piece...and take your time fitting it. No big air gaps. Trim it if you need to. Run some foam over the stock oil cooler for a tight fit.
Set your timing and jet your carbs correctly.
Now go drive.
ANY of the VW shrouds will work fine and I think you'd be splitting hairs as to which one's better, especially for a street car.
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CLKWRK
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Location: Toronto
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AlteWagen
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Location: PNW
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| Posted: Sun Aug 30, 2009 1:35 am Post subject: |
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Another question. Any engineers out there know if a venturi ring shroud draws more air than a regular DH?
I always thought the FAN draws the air and the RING speeds up and straightens the air entering the fan. |
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Bruce
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Joined: May 16, 2003
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Location: Left coast, Canada
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| Posted: Sun Aug 30, 2009 2:53 pm Post subject: |
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It is the fan that pulls the air in. However, at the inlet of every fan or every hole that air flows into, there is a restriction that's called the inlet restriction. By adding the venturi ring you will be reducing the inlet restriction. Therefore, the amount of air flow will increase.
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| overheard at the portland Swap Meet... wrote: |
| ..... a steering wheel made from a mastadon tusk..... |
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