BritishV8 Forum

I'm starting this thread so as not to hijack Mark Rawlins thread on wing aerodynamics  http://forum.britishv8.org/read.php?2,33305

Bill Guzman posted about changes he was making in the front end primarily to reduce drag but also improve cooling efficiency. Hopefully, he will add pictures of what he is doing here. To start it off I'll show what I'm working on right now in that area and others will add their spin.

The big motivation for me wanting to improve cooling efficiency is to prevent detonation. I had already built the LT1 engine to run naturally aspirated and it has 10.9:1 compression so when I decided to add the supercharger I needed to do everything I could to keep coolant temperatures under control and have as cool an intake charge as possible. To that end I got the biggest aluminum radiator I could fit in (31" x 19" with 2 rows of 1" aluminum tubes) and fabricated a duct to bring cool air from the grille to the air filter. There will be baffleing that will route all air entering the front of the car to either go through the radiator or through the duct to the air filter. The fan is a 16.5" Ford taurus that is supposed to have 4,000 cfm airflow on high speed and it mounts in a shroud to draw air through the entire core. My grille is 11" wider than the stock MGB so there will be a lot of air entering the front. The lower valence will have an opening the width of the radiator core and that will also be ducted and sealed to the radiator core. The housing for the air filter will seal against the underside of the hood preventing any air from escaping into the engine compartment and there will be a baffle from  where the MAF mounts to the passenger side fender well that will also seal against the hood

The lower edge of the valence is the piece of 3/4" square tubing shown in the picture. From the lower edge of that square tubing back to the crossmember will be an undertray similar to the one shown. The bottom of the car is flat with nothing sticking down into the undercar airstream until you get to the rear suspension lower arms so undercar airflow should be relatively undisturbed.





The black section are rubber flaps cut from a Volvo shroud that will allow passage of air when the fan isn't running and will be sucked shut when the fan starts up so the fan will pull from the entire core.

Here are some additional pictures

I'm just curious; what strategies do you have in mind to scavenge out the air entering through the front in order to maintain a strong cooling flow?  I also assume   that the flat piece you intend to install on most of the undercarriage would be to stop air lift?  I always assumed that NASCAR engineered their race cars where a negative pressure exist between the track and the bottom of the car sort of creating a negative pressure (suction).  Very interesting and high tech tread you've opened........

When I get home I'll remove the radiator and take a picture through the lower engine compartment so you can see how much space there is for air to escape along side of the engine and into the wheel wells. With the smooth underbody there should be good air velocity under the car at the rear of the engine and forward part of the transmission to create a low pressure area for the air to flow into. I have a Magnehelic differential pressure gauge that I plan to do a lot of measurements with when I get the car together for shakedown prior to disassembly for paint.

Well, the pictures didn't turn out as well as I had hoped. In the first one you are looking out the passenger side wheel well and the red piece you see is the front of the passenger footwell. The center picture shows the space on the side of the engine between it and the trans tunnel, there will be a 2 1/2" exhaust pipe taking up a portion of that space on either side. The third picture is looking past the air duct to the air filter and out the drivers side wheel well. There ia actually a lot more exit area into the wheel wells than shows in the pictures and that is the preferred path for the radiator to exit rather than under the car. There should be no backpressure in the engine compartment at all but the differential pressure gauge will tell all when I get it running.

The last picture you posted Jim is perhaps the best way to lower drag, doing the same.

One place that I found that is like open chute is the battery box area, lots of turbulent air trapped under the car.

Yes will post pictures as I go on with the project. I am using a hood vent from a 1985 Firebird that were design to exhaust air, similar to a prop plane. Hard to get even new, not hard to make out of sheet metal.

Jim gone crazy, is that a SC I see on the pictures  WOW !!! You will go on record as  AFTERBURNER

Thats definately what you need to do Jim, seal off the air entering the rad and evacuate as much as you can from the back, easier said than done tho. Those vents that Bill has installed on his hood are pretty cool , since your car does not have to conform to any cockameemee rules you could get real creative, like venting the engine air out to the exterior where the attached air on the body surfaces would siphon the waste air out.
Dave

Those vents are hard to find.

I went I made a cardboard model of the vent. The vent can be made as big as you needed, it can be made in the hood or a separate piece of sheet metal and the bolted/glued to the hood. The originals have spring clips.

These pictures will give an idea as to how to make them. they are simple.

Once the sheet metal/plastic etc is cut it will be needed to add a strip of metal as seen in the picture.
Then small corner pieces for each side, then a middle piece, this is optional. A good looking screen can also be put in place.

This what the originals GM Trans Am hood vents look like

Jim, heres an idea for evacuating eng compartment air, I think you have the room to build the ductwork.
Dave

I'll keep on watching the progress; IMHO, radiator airflow is directly proportional with engine bay flow evacuation.........

I love the look and platform of the widdened MGB. It seems like such a more substantial car.

Some of your work is similar to some of the things I attacked on the Pantera. With the Pantera the air through the radiator went under the car. I ducted it all out of the hood. I tried not to make it look like a GT40 and I have a movable duct should I need more flow for say a track event:

http://www.rc-tech.net/pantera1/hood/hood.htm

The original air dam was fiberglass. I built one from aluminum but unlike the original, I closed off the bottom of the air dam like yours. Then I tied the bottom of the air dam into a belly pan:

http://www.rc-tech.net/pantera1/airdam/ad.htm

http://www.rc-tech.net/cars2/panttransam/bp/bp6.jpg

What the car is missing is the last section fomr the under the engine to the rear which should include a difuser. I don't know if it will ever happen but this much was done before the car was painted and before the car is on it's wheels.

Bill

I haven't ruled out hood vents yet but if I can get by without them I would like to preserve the (sort of) stock hood contour. It's just a thing with me, when the car was narrow and I put the Jetfire turbo Olds in it I did a large amount of work to the crossmember, suspension and steering to lower the engine enough to get it under the hood. When I see bulges and scoops to clear engine bits in a swap it says to me that the person did not engineer the job completely - sorry, just my personal opinion. When I can do the pressure measurements, if there is a large differential above and below the hood I may put some vents in similar to this. The testing will also show where on the hood they need to be. That's why I'm not painting it right away.



The battery box area will have a cover that extends the floor pan back to just before the suspension arms. On the drivers side it will cover the bottom of the water/methanol injection tank and on the passenger side the battery box. Not much I can do about the suspension arms. In the picture below imagine the floor pan attached to the very bottom of the tunnel and rocker boxes, the pinch weld will only be about 3/8" proud of the floor pan.

 

Right behind the rear end the fuel tank provides another flat surface even with the floor pan. It gets messy at the back.



Dave

It's funny you should do a drawing using that shot of the car because I have several that I have marked up with similar Corvette style vents. I don't think they look bad but they do change the look of the side of the car and one of the things I was after building this thing is to maintain as many of the identifyable MGB styling cues as I could even though there is not a stock panel on the car - most are not even close to being stock. Functionally, I'm not sure how much help the vents would be. The wheel wells are a low pressure area due to the high velocity are passing down the side of the body (or so the the generally accepted wisdom would say) so air will be drawn into the wheel well and out the wheel opening anyway. The duct would only shortcut the distance to the airstream by a couple inches unless I do surgery on the front corners of the foot wells. Again the pressure testing will tell me if it is worthwhile to do.

Gary

I have referenced your hood and valence fabrication a number of times while planning what I want to do. Nice work. With the engine in the front I couldn't do a full belly pan because of the heat but I've tried to keep the floor as flat as possible and on the same plane as the undertray at the front so as to disturb the air as little as possible under that and maintain high velocity/ low pressure.

Jim, I like the air flow meter test you plan in doing.  A well flowing mass of air intended for radiator heat transfer, in a perfect engineered plan, would also remove the engine bay's radiant heat.  If the engine bay becomes pressurized then, big radiators and cooling fans don't mean a thing.  Lots of MG owners rely on the large hole cut through the fender wells (headers) to maintain airflow and heat evacuation.

The re-birth and final days of the MGB-RV8 have, IMHO, an appealing hood bulge that suggest a standard of a high performance power plant.  I'm amazed at the amount of work you are dedicating to your plan/project; I remember the day that I first noticed your project and the first thing that came to my mind was "why did MG not think of that?"

My good friend Jim Stuart got me involved in the world of V-8 modified MG (it might have also been a curse, LOL) and he's always also wished that the car was a little wider.  I referred in fun to my MG project as the "Pocket Rocket" however, I also always wished that the MG has more body width.  You're living my dream and after you're done, I would really love to see it in person as I believe that you'll have built one of a kind that will cover most of grievances people express while trying to achieve a  high performance conversion with the standard body.  I tip my hat to you as I just would not have the consistent patience to deal with this kind of advance project, in fact, I'm having a hard time finalizing my Ford engine conversion, although, having Leukemia puts a damper in my energy level.

Reading the forum shows the different levels of taste in creations.  Some like it simple and clean while others like high tech modifications; it a great way to express or define anyone's talent and taste.  I'll keep on wishing and admiring some of these talents.......

Cheers,

Jacques

Jacques

Sorry to hear about the leukemia and wish you a speedy recovery. I plan to have the car completely finished for the 2014 British V8 meet in Colorado Springs, hope you can come.

I plan to do quite a bit of pressure testing when it is finally running. I want to map the differentials above and below the hood front to rear and side to side and see if vents would make any sense. If there is as little as 0.5 in of water pressure differential above and below the hood that would create 50 lbs of lift on the front of the car. I also want to measure pressure drop across the radiator and compare the engine compartment pressure to various exit points and possibly rearrange the exit flow. The original plan is to have the majority of air exit through the wheel wells with a lesser amount going down past the exhaust and exiting on the underside of the car. With the flat bottom on the car and nothing hanging down until you get to the rear suspension I anticipate there will be accelerated airflow and a reduced pressure vs the floor inside the cockpit. I truly hope I don't end up having to cut a bunch of vents and I can preserve the stock - ish look as much as possible.

Interesting stuff.  Jim, we have some similarities though our approaches differ markedly. Similar compression ratios, you at 10.9 and mine at 10.6 and both using boost. Interestingly enough we seem to be using a near identical sized radiator but of course I have an extra large economy sized hood vent around the blower so much of the aerodynamics is much different and we are going in different directions there. Fortunately experience on the Roadmaster project indicates that cooling the engine and the engine compartment should not be particularly challenging for either of us, though admittedly that car also has a rather large hood opening.

But this is an area which has not been adequately quantified. It seems to me that the MGB is radiator limited rather than airflow limited. The radiator frontal area is small and is really restrictive for even a small V8 as evidenced by everything we do to maximize cooling. We know all the tricks and use them and just that fact tells me that the radiator is too small to begin with. Both of us have remedied that problem. So a pressure differential across the radiator core is the next place to look. Since a smooth hoodline is important the only way to take advantage of lower pressure above the hood is by using some sort of hidden vent system, and with a smooth hood that is a tremendous challenge. So I think you are right to pursue the wheelwell and underbody areas. Your Volvo one way valves are a very good idea and makes me wonder if that concept might not apply elsewhere. How about a pop-up vent on the hood that blends into the hood surface? We know that a front hinged hood that is unlatched will rise several inches at speed, demonstrating a very significant pressure differential and airflow potential. If a mechanism could be designed that would lower a section of the hood skin as opposed to raising it as the differential builds the appearance would be essentially unaffected, although at this point I'm not sure that a passive design is possible. Might the idea be applicable to wheelwell airflow? Not needed perhaps but a thought and something you might be able to provide for in the design.

Jim

Jim, If by some circumstance, you do consider side vents, perhaps "Hemi Healey "/ late Gullwing) ? roverman.

Jim

I'm curious how the Roadmaster cooling system performs now that you have had the opportunity to drive it in traffic and at speed on the road. What thermostat is in the engine, what fans are you using and how are they actuated and at what temperature(s)?. I know I could look it up myself but there are sooo many pages in the build journal. Does it run at thermostat opening temp or at some figure higher than that? Does the temp climb in traffic or at high speed? Does high ambient affect the running temp?

I am using a 160* thermostat in the LT1 and a BMW dual sensing switch that turns on the low speed at 176* and the high speed at 190*. My fondest dream would be to never see the temp gauge reach 200* on a hot day in traffic. My Silverado goes up to 190* and never moves no matter what the load, speed or temperature is - I would love to have the MG behave the same way. I have a ways to go before I will have a chance to see how it works and what pressures look like around the car at speed. If the need is there I will definitely consider some innovative solutions - the data will tell.

BTW how much boost do you plan to run and what will the curve look like? Do you plan to run water/meth injection or any type of boost triggered retard?

Jim, this is the paper that got me thinking. You have been around aircraft so you know how it works.

http://www.datsuns.com/Tech/aerodynamics_and_cooling.htm

At the CAF where I work one day per week we have a P-51 which is water cool. The intake on the P-51 is allot smaller than the radiator.
It is shape like a funnel, small intake that ends to over the whole radiator. Air is rush and then slow down when it reaches the radiator core.
This makes less air to evacuate. Combine with a low pressure under the car it makes the perfect cooling.

1998 through 2000 Camaros have very small air intakes in the front, in fact on road racing this openings are used as engine intkaes most of the cooling is done with low pressure air from the bottom, same as Corvette.

Pontiac Trans Am had zero grill opening, all of the cooling was done from the low pressure side. Once the air is introduce in to the engine bay is at a very low speed, it not longer is turbulant rushing air from auto speed, thus easy to evacuate.

So many questions and such a little keyboard!

Cooling performance of the Roadmaster is quite sterling. I believe we used a 195 thermostat. The fan is a late model Camaro dual unit and I put the same one in my car. The controller is the remote bulb type and after Mike Moor and I routed the bulb inside the top radiator hose the combination became very effective, though before that it had a bit too much hysteresis. I found a Saab 2 stage switch that I used in Edith's TR7 that I like a lot. There should be a lot of detail in the Power Tour thread, but that big radiator really does the job.

I'm expecting boost to come in around 8 psi but on my last build I was expecting around 10 and got 16+ so there is no real way to know until it's running. I hope it won't be necessary to change the top pulley but much more than 10 and I think I may have to. But I have about a 40% increase in displacement with only a 20% increase in blower size so it may be fine. If I were a little better mathematician i could probably ballpark it pretty close. Don't know yet what the curve will look like either. On the last one it came in just off idle and built really fast. I'm not expecting that this time. For one thing the heads are bigger so there will be less restriction'and the cam is bigger too. For charge cooling I am running the air through a 2-3/4" thick X 8" X 13" liquid intercooler core. But less boost means less heat to take away. In an odd sort of way the restrictive heads of the 215 caused higher manifold pressure which made more heat which made the intercooler more effective, then the nozzle effect at the valve cooled the charge as it entered the cylinder. Although peak power mayhave been less the boost came in early and strong. This one will be different but how much is hard to say.

Jim

Jim, roots blowers create more heat, specially at low rpm. If a by pass valve could be install it would help on the cooling at low rpm.
Jim if you figure out to install a by pass on the root let me  know. I am not working on mine, but I will soon.

Jim S. has a centrifugal, centrifugal chargers do not create as much heat as the roots. Actually the centrifugal runs a bit cooler than the roots at lower rpm. The centrifugal will create heat in the upper rpm range when it is making max boost, but is also getting for fuel as needed and fuel cools and there is also alcohol spray available.
 Looking at Jim's S. Super Charge B ( Lic plate JSSCB) radiator and wide engine bay, I do not think he will have any cooling problems.

My old 1996 LT-4 Vette with a Vortech super charger never got hot and no mods were made to the cooling system. C-4 Vettes used low pressure air from under the car to cool the radiator. I drove from Flagstaff to Camarillo with outside temps of 109 degrees and the Vette got to 245 degrees max was 260 for quite a few miles. Kept my eyes on the gauge until it got back to normal 210 degrees.

Bill

I bought a book several years ago by Joseph Katz called Race Car Aerodynamics and he has a section in it called Internal Flow where he talks about cooling. The section is several pages long but here are a few of the high points.

Of several air exit strategies he showed the one that provided the best Cd was taking the entire radiator exhaust out through the hood similar to the GT40 Ford, the Cobra Daytona Coupe and Corvette  CSR race cars. The 2nd best was exiting the air out through the wheel wells and the worst was just dumping it into the engine compartment.

A smoothly expanding and leak free diffuser from the air intake opening to the core of the radiator will significantly increase the static pressure at the face of the radiator. The pressure drops like a rock after passing through the core so it essential to find a low pressure area to dump the air into to so pressure does not build behind the core and reduce flow. Fans help here since the pressure effect only comes with forward velocity and nothing is happening at rest.

It also discusses very small openings as found on aircraft and while they can make significant reductions in drag and high static pressure increases at the core they are optimized for a given speed. If you exceed the design speed, there is boundary layer separation for air passing over the body around the opening causing increased drag. If you are going slower than the design speed there is internal flow separation causing reduced cooling efficiency (probably not what you want in a street driven car).

So after reading that I may try something like the diagram below. The dashed lines are aluminum sheets that span the full width of the core and would be contained on the ends with vertical aluminum pieces creating two ducts into the radiator core. The increase in area from the front of the duct to the face of the core should provide some increase in static pressure at the core while the inlet area should be sufficient to satisfy the flow requirements over the full range of speeds of the car.



My sense is that designing for this effect in the radiator inlet is similar to what you find in exhaust tuning - you can have a lower increase in power over a broader rpm range or a higher increase but the engine then becomes very "peaky" over a narrow rpm band.

Jim B

Good news abot how well the Roadmaster cools. I have one of the Camaro dual fan setups and it fits the core perfectly but the air duct to the filter interfers with the drivers side fan and I can't use it. The Taurus fan pulls about the same amount of air as the two 12" fans in the Camaro unit so I should be OK.

The Vortech kit for the C4 Vette LT1/4 came with a pulley that gave about 8 psi boost (correct me if I'm wrong Bill) and the stock compression was 10.4:1 (10.8:1 for the LT4). My engine has higher compression due to decking the block to get a quench just under .040" but I also have a more agressive cam that will reduce boost somewhat, I'm guessing around 6-6.5 psi from what I have read. I should be ok on detonation with 12-15 gph of water/meth injection under boost.

Bill

I didn't know you had an LT4 Vette. Am I correct that the Vortech kit produced about 8 psi? Did you have any issues with detonation? Did you have to use water/meth injection?

I know that the C4's had issues with cooling at speed for the reasons you mentioned. How did it behave in traffic with the fan on? Were you running the stock thermostat and fan turn on settings?

Jim S., I used the standard MGB cowl vents ,(2) and had them sectioned shorter, on their length, to 12" oal. ?  They will go behind front wheel wells, as vents and still keep the MGB  look.  Cheers, roverman.