Diffuser anyone?
- Thread starter MHNCO
- Start date
Mike
Lifetime Supporter
Larry is correct. It's more of an aesthetic appeal to me provided it does not produce any adverse side affects.
Doug, I plan on being there. What time do you need to get there to get a parking spot with some room around it to be able to climb of the thing? I went a couple years back in the Ford GT and didn't even pull in it was so packed. Does anyone ever head down later that afternoon to the Golden Supercruise?
Doug, I plan on being there. What time do you need to get there to get a parking spot with some room around it to be able to climb of the thing? I went a couple years back in the Ford GT and didn't even pull in it was so packed. Does anyone ever head down later that afternoon to the Golden Supercruise?
Seymour Snerd
Lifetime Supporter
Perhaps the diffuser design could include a small discrete mounting point for a little tiny camera.
Michael
coming back to your initial question like or dislike. Although i have thought a lot of building something similar for my car, i have to say no i won´t. Dislike it in every visual aspect. Completly destroying the classic lines of your otherwise very beautyful and racy car. Whatever the functional aspects are, i would bear with the original cars behaviour, after all you drive 60's racecar replica and part of that is the feel of it. The car will still be faster as most of your competition on a trackday.
TOM
coming back to your initial question like or dislike. Although i have thought a lot of building something similar for my car, i have to say no i won´t. Dislike it in every visual aspect. Completly destroying the classic lines of your otherwise very beautyful and racy car. Whatever the functional aspects are, i would bear with the original cars behaviour, after all you drive 60's racecar replica and part of that is the feel of it. The car will still be faster as most of your competition on a trackday.
TOM
Mike
Lifetime Supporter
No problem Tom. it's not for everybody. I will say when I first saw the mock up on there my reaction was identical to yours. After some tweaks when iteration one was completed, powdercoated black, and hung under the car, it grew on me fast. Given diffusers were not part of the GT40 program back in the day, it still has a period look and appeal to it in person. The car almost looks incomplete now without it on there. I am going to be working with Mark on iteration two with some slight tweaks on shape as well as the mounting system and hardware. Will post some pics later one when it's complete. I really do think that once you saw it in person, it would grow on you. It really does look that good. Since you have thought about trying one, mock one up and see what you think after looking at it for awhile. Thanks for you input either way.
Howard Jones
Supporter
A couple of things. The 3 holes completely ruin any aero advantage that might be possible by venting the low pressure that might be created within the tunnels. Also without a good laminar flow at the entrance of the diffuser there will not be any areo advantage. This requires a flat bottom from the leading edge of the diffuser inlet all the way forward to at least the opening required by the front wheels. Leaving the bottom of the car open negates any possibility of a diffuser working much at all if any.
Having said that I like the look. The angle of the diffuser floor (roof?) also look pretty close. Typically this angle is around 7-8 degrees at that ride height. The heat issue in a GT40 is mostly accounted for with the venting in the top of the rear bodywork. That's why the factory put them in 40 years ago. I wouldn't worry too much about that. Tape the bottom up with some cardboard and drive around.... slowly!!! and see if you have increased water temps.
For that kind of money I would pull a fiberglass mold off of them, remake in fiberglass and save the original for making others when/if it gets damaged .
Again, Nicely done, looks good.
Having said that I like the look. The angle of the diffuser floor (roof?) also look pretty close. Typically this angle is around 7-8 degrees at that ride height. The heat issue in a GT40 is mostly accounted for with the venting in the top of the rear bodywork. That's why the factory put them in 40 years ago. I wouldn't worry too much about that. Tape the bottom up with some cardboard and drive around.... slowly!!! and see if you have increased water temps.
For that kind of money I would pull a fiberglass mold off of them, remake in fiberglass and save the original for making others when/if it gets damaged .
Again, Nicely done, looks good.
Those in favor of sealing up the bottom of the engine compartment = 2.
Michael = 0!
I like Howard's idea of sealing up the hole under the engine with cardboard to see what effect that would have on engine compt heat, Mike. It'd only take a minute to slap a sheet of cardboard up there and afix it w/duct tape and away you'd go.
As I mentioned on the phone (and now H.J. has here as well), I'm not an engineer, but, simple logic says a hole in the car's belly is going to negate any aero 'bennies' your diffuser might provide. I know you're only going for looks, but, if by sealing that hole you could realize an actual gain in areo efficiency at the same time - why not do it? :shrug: ('Two birds with one stone, and all that...)
Mike
Lifetime Supporter
Good point Howard on the vent holes. That would allow atmosphere to fill in the channel once a velocity was reached that caused pressure to decrease. The underbelly of my 40 already has a belly pan. I would suppose you would need to entirely seal off the engine bay by extending the diffuser panel completely forward to the front of the engine bay to achieve true laminar flow. That said, with the oil pan being flush with the belly pan and mostly filling the bottom of the bay, I don't think flow is going to be disrupted much. I did stay at a Holiday Inn last night FYI. Thanks good stuff!
Mike
Lifetime Supporter
Well maybe but not neccessarily. The diffuser produces low pressure by accelerating the air flow through an expanding channel. The only affect the opening around the oil pan would be to produce some turbulence and thus disrupt the flow through the diffuser. I'll snap some pictures once I have the car on a lift but you will see the oil pan is flush with the belly pan and it does not seem as though the small gap around the pan is going to create a lot of turbulence.
Something noone has mentioned yet is FANS. Several of us have added some 5" fans at the head of the engine bay on either side of the engine. They suck air from the area just beside the fuel tanks(and wheel wells) and we are using them to keep air moving in the engine bay to preserve our rear clips just over the exhaust merge at the back of the engine. Some of us have a section of exhaust piping that is close to the fiberglass. Shields are not quite enough to keep this area from getting so hot it becomes pliable. Mine even blistered the paint. Summit carries the Derale 16505 and there are others fom Spal and the like. These can be switch or thermostat activated. They can be coupled with an off delay timer from Waytek that can be set for 30 seconds up to an hour or so to keep temps down in the bay after shut down.
Then there are coolers that can be added at the rear to keep the oil and trans cool as well. They can be sized to fit the vents at the rear beside the exhaust. And lest we forget, there are heat shields that can keep temps down in the trans from the radiant heat of the exhaust.
Micheal you might want to reconsider the location of your tag, as it blocks the outflow of air. I molded mine into the spoiler.
Bill
Then there are coolers that can be added at the rear to keep the oil and trans cool as well. They can be sized to fit the vents at the rear beside the exhaust. And lest we forget, there are heat shields that can keep temps down in the trans from the radiant heat of the exhaust.
Micheal you might want to reconsider the location of your tag, as it blocks the outflow of air. I molded mine into the spoiler.
Bill
Mike
Lifetime Supporter
Good info Bill. I have also thought about the heat after shut down baking the bonnet. On both my Ford GT and the 40 I always pop the hood after shutdown and let it cool down before lowering it back and putting the car away. I am going to put some heat reflective tape in that area you mention right above where the header tubes meet the collector.
The license plate mount is set back off the vent 6-8" so as to not block off airflow. I drove it in ~90 degree temps last weekend and detected no difference in coolant temps or engine oil temps. In traffic the radiator fans kick on and seem to be able to keep up well enough. So far I have had no overheating issues knock on wood. Olthoff did modify the dual nostril openings up front in a way that improves airflow quite a bit I would imagine.
The license plate mount is set back off the vent 6-8" so as to not block off airflow. I drove it in ~90 degree temps last weekend and detected no difference in coolant temps or engine oil temps. In traffic the radiator fans kick on and seem to be able to keep up well enough. So far I have had no overheating issues knock on wood. Olthoff did modify the dual nostril openings up front in a way that improves airflow quite a bit I would imagine.
Before you guys jump at the insulation wraps, you should read what Chuck, Frank Catt, and myself have written in response to heat related problems. First see if you have general problems. If so the wraps may do O K for you. But if you have specific problems you need to see what others have done to aleviate the problems. Chuck originally came up with a sloution.
http://www.gt40s.com/forum/gt40-build-logs/22083-chuck-ryans-rcr-build-34.html
Reat post 667 for his solution. Then read about the fans 672 and several after that one. Then here is his revision of the insulation, because it wasn't suficient.
http://www.gt40s.com/forum/gt40-build-logs/22083-chuck-ryans-rcr-build-38.html
Read post 743-748. Chuck is the consumate builder and came up with some great ideas. Some I have incorporated into my build.
Another thread on heat and related issues is found here with some interesting solutions.
http://www.gt40s.com/forum/gt40-tech-exterior-interior-ac-trim/37481-toxic-cabin.html
Bill
http://www.gt40s.com/forum/gt40-build-logs/22083-chuck-ryans-rcr-build-34.html
Reat post 667 for his solution. Then read about the fans 672 and several after that one. Then here is his revision of the insulation, because it wasn't suficient.
http://www.gt40s.com/forum/gt40-build-logs/22083-chuck-ryans-rcr-build-38.html
Read post 743-748. Chuck is the consumate builder and came up with some great ideas. Some I have incorporated into my build.
Another thread on heat and related issues is found here with some interesting solutions.
http://www.gt40s.com/forum/gt40-tech-exterior-interior-ac-trim/37481-toxic-cabin.html
Bill
Very true, the holes are for sure counter productive to the diffuser design, we decided that we would place some holes to add a little interest. I'm not a fan of that detail as it detracts from the "purpose built" look that Mike is going for. Not sure what you're thinking about that detail Mike, we didn't really discuss it.
Here's an underneath view.
