EFI University

[gsportcars]

Ok, so I am currently building an extension to my workshop to house a 2WD Maha LPS2000 dyno with digital software and control upgrade.
I have acquired a 27" axial flow 3 phase fan that I was originally going to use for vehicle cooling with a custom made cowling to direct airflow, This fan flows 12000cfm. I am constantly on the lookout for a large centrifugal fan with similar or more airflow to use for cooling and I may have found a suitable fan for the job.

My main concern is with extraction requirement.
I have attached a quick sketch of my workshop layout (excuse the primative 10 minute paint effort) from a birds eye view. The dyno will be in ground and positioned obviously to allow FWD and RWD cars. The cooling fan will be mobile on lockable castor wheels. The "old wall" is shown which is being knocked through for space for the dyno.

So, to get to the point, I have shown a rough idea of both dedicated exhaust extraction hoses with fans mounted on the wall, and positioning for 2 or 3 large extraction fans mounted in the rear wall designed to withdraw the exhaust gas within the room.

My question/s are....
Overall, what is more effective for exhaust extraction? The exhaust extraction hose or the large wall mounted fans?

Are there any concerns when using the large wall mounted fans with regards to the distance the vehicle is from the fans/wall? To explain... when testing a FWD car, the car will sit closer to the back wall than when testing a RWD car as the dyno is in a fixed postion. What effect does this have on the exhaust extraction if the car is too far away or too close to the fans?
Obviously exhaust extraction hoses can be positioned directly at the tail pipe for either setup.

If I where to opt for just the exhaust extraction hoses, would there be any adverse effects for the cooling fan because the rearward wall would be closed off? For eg; could the flow from the cooling fan be reduced or contaminated as it would have to flow through/around the vehicle and then return (I assume) along the outer walls/ceiling back towards the front of the vehicle and the rest of the workshop.

Of course I would like to install both types of extraction fans but budget dictates otherwise at the minute. Noise is somewhat of an issue too which is why I simply don't open the rearward wall.

Any tips or suggestions are welcome.
Thanks,
Gavin.




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[hexdmy]

I would do both, a room ventilator , and your extraction setup. You would have to move a tremendous amount of air to properly vent the exhaust without being directly at the tailpipe .

At the shop that I worked at previously we had three commercial kitchen ventilators in the shop, all with 7.5 hp three phase electric motors. One was dedicated to exhaust extraction with duct and hose setup that could be placed next to the exhaust pipes . The other two were just to get some air flow through the shop. These were big ventilators ( I don't remember the CFM) and we thought with the other two, we would have a considerable amount of air flow through the shop. In reality, it would take about five minuets to clear the air in the shop with all three fans running, this was in a 5500 square foot warehouse building. If I had to do it over again, I would have chosen fans that could move a lot more air, and possibly paid someone with experience ventilating workshops/factories to figure out exactly how much air flow would be required to keep the air at a healthy level.

[gsportcars]

Hexdmy,
The area that I primarily need to worry about is less than 300sq feet or 2500[/b]cubic[b] feet.
That is the volume of the extension that is being built on the current workshop. This is the area that will be the first to fill with exhaust gas (ie, where the rear of the car will be. It is not a massive space. I roughly calculated that I could exchange the air in this part of the room in less that 8-9seconds with two axial fans flowing around 10,000cfm each. Although I stand to be corrected on the math lol.

Would there be any concern for the fan motor on an axial fan if I used it for exhaust extraction with hoses and large cones at the tail pipe/s? I would guess all the additional fresh air being drawn in would be more than enough to keep temps down???


I have got my hands on a solution for vehicle cooling. I'm hoping it's going to be enough to do the job



The intake cowling is unbolted.

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And one for size reference


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[Warpspeed]

I would use three separate blowers.
Two movable, and one fixed, each has it's own special job to do.

A large axial shifts a lot of air, but will not have much pressure or velocity capability.
This would ideally be mounted into an outside wall to provide fresh air circulation though the workspace.

A twin entry drum type centrifugal would be best for radiator cooling because it can generate some very high air velocities over a small rectangular exit area that can then be moved right up to the front of the vehicle.
To get the velocity, a smaller blower driven fast will work much better than a much larger blower driven slowly, even if the CFMs are the same.
Blower exit velocity might be for example 60 Mph.

Exhaust extraction usually involves some fairly long large diameter flexible ducts that can be placed right at the exhaust pipe ends. These ducts will have some pressure drop, so again a drum type centrifugal blower will work better than an axial fan for this.

The exhaust extractor need not be all that large, actual total exhaust volume will be roughly 2.2 CFM per Hp.
If you can pull several times that volume from just behind the exhaust pipes with two large ducts, that is all you will need to collect all the exhaust.
The extra volume dilutes the exhaust gas and reduces it's high temperature, which may be an issue for the ducts.
High air velocity is not needed or desirable, so a larger drum type centrifugal driven slower will be more power efficient.

[gsportcars]

Thanks for the replies. That gives me something to think about. The large centrifugal fan is being used for cooling. The outlet is bigger than it should be as it must have been previously connected to a box section ducting system. I will be making a custom outlet cowling designed to keep the air speed up and direct it more effectively. I can also try different pulley sizes if needed if the air speed is too low. This fan will be speed controlled through the dyno software so it is not running flat out all the time either.

The goal now is to find a couple of smaller centrifugal fans to use for the exhaust extraction with hoses etc. So long as I can size these correctly (which shouldn't be a problem now after Warpspeeds reply ) I should have that end covered.

I already have the previously mentioned large axial fan which I can mount high in the rear wall to provide the general extra airflow through the dyno room/workshop.

I may start a dyno room build thread soon when some more progress is made.

[xenocron]

Exhaust extraction with the smaller hoses if hooked directly to the tail pipe(s) changes the VE of the motor (less back pressure if under vacuum or more if the hoses because a restriction)

I would avoid doing this if at all possible...


You can place a "cup" near each tail pipe, but how much bad exhaust will these actually be able to scoop up at a WOT pull making "X" amount of HP really...I dont know

My room has about 30k CFM of air flow through it (2 large 30" fans, 5 hp each), the air turns over once every 6-10 seconds and since the 2 fans are at the back of the room, pulling air through the front, there is a slight vacuum created in the room, but since the pressure at the inlet is the same as the exhaust then there is no variation in VE.

(2) of these
http://www.grainger.com/Grainger/wwg/search.shtml?searchQuery=7f847&op=search&Ntt=7f847&N=0&Ns=Availability_Sort%7C0&sort=DD&GlobalSearch=true&sst=subset

And a VFD
http://driveswarehouse.com/p-2134-x200-075lfu.aspx

Its a lot of money, but I promise you its so worth it...not only for exhaust extraction, but HEAT as well...which most of us forget about. Even if you move the air over and around the car, the heat stays in the room and builds up.
_________________
EFI University East Coast Instructor
www.xenocron.com
845-504-5340
Specializing in Honda/Acura Applications

[xenocron]

If you want professional help, these guys are top notch.

http://noisebarriers.com/
_________________
EFI University East Coast Instructor
www.xenocron.com
845-504-5340
Specializing in Honda/Acura Applications

[gsportcars]

I'm not intending on actually attaching the extraction hoses to the tailpipe/s for the very reason you mention. Instead I hope to have a couple of large cones to place directly at or over the tailpipe/s to catch the exhaust gas. These cones will of course collect fresh air at the same time. So long as I can oversize the exhaust extraction fans for the purpose, I should have this end covered.
I still then have a 12000cfm axial fan in the back wall to draw some fresh airflow through the whole room.
I will update as I make more progress.

[El Verdugo]

Great thread as I am also assembling my extraction set up and I have a similar situation as the OP.

Thanks for the info Xenocron, the fans and VFD are a bit baller for my budget at the moment, but going to try to find some used ones like the the one on the link you placed.
_________________
Alberto I Correa, Jr.
EFI 101 Graduate 7-16-05
AEM EMS factory trained
www.corrperformance.com

[Warpspeed]

If you are prepared to do the leg work, auctions and machinery graveyards are a good source of cheap air blowers.
These sometimes sit unloved and rusting out in long grass for years, and can often be bough for scrap value.
Sand blasting and paint, plus new bearings, and you are set to go.

[El Verdugo]

Thank you Warpspeed, got a local scrap guy doing the leg work for us as I traded him some scrap for some fans. The ones we need should be arriving this week.
Here is a picture of the shell he took from us the other day.


My apologies for thread jacking OP in advance.
_________________
Alberto I Correa, Jr.
EFI 101 Graduate 7-16-05
AEM EMS factory trained
www.corrperformance.com

[Warpspeed]

Second hand stuff is definitely the way to go.
Bought this for a future flow bench upgrade for $175.00.
Over 1,000 CFM flow at 120 inches of test pressure (with a 30Hp 3 phase motor).


And I spotted this for free while diving down the road.
It was poking out of a dumpster bin in front of a factory.
Only had to buy the wheels and the bicycle rubber handlebar grips plus grey spray paint, and weld up the frame.
I already had the 3HP three phase motor, pulleys and drive belt.
A really great home dyno cooling blower for the massive total financial outlay of $20.00 + the fun putting it all together.
Airflow 8,000 CFM, blocked pressure 0.25 inches, discharge velocity 60 KMH.
Not huge, but more than enough for what I am doing.

[El Verdugo]

Reviving this thread, where do you guys got or recommend for the actual hose(s) used to flow the exhaust out of the shop? I dont want to get a inferior material made of the hose and the heat generated from the exhaust cook the hose material over time.





So I have a back wall that needs the hose routed upward to a extraction fan with a hood on the roof of the shop.

Here are some pics of where we have the dyno at the moment.






Thanks in advance
_________________
Alberto I Correa, Jr.
EFI 101 Graduate 7-16-05
AEM EMS factory trained
www.corrperformance.com