5 blade fan

crummasel · 01-10-2013, 04:25 PM

Another obscure question:

Has anyone made experiences using the 5 blade fan on an - say - 2,4E-ish engine with the original early belt drive ratio on daily operation?

Application would be healthy, mildly tuned 2,4L in the range of 180..200HP in a not too warm climate area.

OK, a assume it kills the engine and is evil; usually i use 11 blades but what are experiences, if any?

Thanks,
Robert

pjh69911 · 01-10-2013, 04:45 PM

I've often thought it might help keep engine temperatures up in the cooler season, and drive the water condensate out of the oil. Have yet to try it, though.

Walt Fricke · 01-11-2013, 11:30 PM

Well, Porsche's experience was not good, though no doubt part of that was due to the thermal problems the anti-smog stuff caused the 2.7s.

And would it not make sense to use the drive ratio they did, assuming you want the cooling they thought was needed for the less powerful 2.7s? Unless this is a full out race motor where you are scrimping for that extra one horsepower?

You can find the CFM figures for the various stock configurations. I don't know if you could extrapolate from those for the 5 bladers down to what turning it at a slower percentage of the 5 blade speed would give you in CFM, for a comparison with what the 2.4S had as stock.

Is fan flow directly proportional to fan RPM, at least at some range of RPMs before cavitation and other stuff sets in? Or does the inertia of air molecules mean that there is a curve which tends toward flattening as blade speed increases? As the power to turn it increases (exponentially, I assume, like the car's body as its speed increases)?

crummasel · 01-12-2013, 06:31 PM

Quote:

Originally Posted by Walt Fricke

Is fan flow directly proportional to fan RPM, at least at some range of RPMs before cavitation and other stuff sets in? Or does the inertia of air molecules mean that there is a curve which tends toward flattening as blade speed increases? As the power to turn it increases (exponentially, I assume, like the car's body as its speed increases)?

I think that's exactly the point.
I do not know and i do not run a test laboratory.

Also i do not know if the related cfm curve flattens out and at what point.

Thats why i asked curiuosly if anyone has made some experiences.

Let us assume the application is a 2.4L @ mild 180..190 HP and the outer temperatures rarely exceed 30° (86F)

Usage is countryside, no traffic jams, crusing speed is ~ 120Km/h (95mph), transport speed is 150..240Km/h (95..125mph), vmax 255Km/h (160mph) (highway).

I do not have any experience with this one since i ever used the 11-blade, so where do you think could be the limit to use this one. There are no further obstacles (just SSI, no air pump, reactors etc.) which make life tough. 9,5:1 comp, 98 oct pump gas as standard. Belt ratio would be std. 2,4L (~1:1,3 if i remember well)

Walt Fricke · 01-12-2013, 07:00 PM

For what it might be worth, here is what I have copied from various sources:

Fans
Flat race fan 2000 liters per second (4237.36 CFM) at 7,000 engine RPM/ 13,800 fan RPM.
This cost 35 hp!

Stock fans run 1,100 to 1,500 liters per second (2118.88 to 3178.32 CFM) at about 5 hp

RPM Flow
Fastest ratio 1:1.8.
226mm x 11 blades 6,000 1380 lps - 2924.054 cfm
245mm x 5 blades 6,000 1265 lps - 2680.383 cfm
245mm x 11 blades
Mid ratio 1:1.68
226mm x 11 blades
245mm x 11 blades 6,000 1500 lps - 3178.32 cfm
Slowest ratio 1:1.3
226mm x 11 blades
245mm x 11 blades 6,100 1390 lps/2945 cfm

Flow @ 6,000 RPM
liters/sec cfm ratio diameter blades type
1100 2140 3.6
1210 2564 1.8 245 11 3.6tt
1265 2680 1.8 245 5 2.7 76-7
1380 2924 1.8 226 11
1390 2945 1.3 245 11 (6,100rpm)
1500 3178 1.68 245 11
Race engines from 906 to 962C: 1:1.3 pulley ratio. Fan dia. 226mm. 8 hole fan and pulley.

From 1968 through 1975 the fan is 11 blades, 245mm, with 1:1.3 drive. 1390 lps/2945 cfm @ 6,100 rpm. 8 hole fan and pulley.

72-3: fan ratio approx 1:1.3.

2.7 1976-7: 1:1.8. Fan dia. 245mm. 1265 lps/2680.383 cfm @ 6000 crank RPM. Small holes from here on out.

3.0 Turbo: 1:1.67. (probably same ratio and delivery as 3.3 turbo?) Fan dia. 245mm.

3.3 Turbo 1: 1.68 ratio. 1500 liters per second (3178.32cfm) at 6,000 crank RPM. Fan dia. 245mm.

SC 1978 and 1979 (cr 8.5/1 & 9.3) 1:1.81 1380 l/s (2924.054cfm) @ 6,000 crank rpm. Fan dia. 226mm
Engine 930/16/17 used 1:1.68 ratio. Fan dia.

SC (cr 8.6/1) 1:1.68 ratio. 1,500 l/s (3178.32cfm) @ 6000 crank rpm. Fan dia. 245mm. This combination was used until the 964s.

SC (cr 9.8/1) 1:1.68 ratio. 1,500 l/s (3178.32cfm) @ 6000 crank rpm. Fan dia.

964 1,010 lps/2140 cfm @6,100 rpm. New curved blade shape. (DIAMETER OF FAN?)

993 twin turbo: 245mm 11 blade fan, 1:1.8 pulley ratio, 1,210 lps/ 2563.845cfm @ 6,100 crank rpm. (why is this less effective than the old 226 fan at the same ratio?)

Ronnie's.930 · 09:49 PM

Quote:

Originally Posted by Walt Fricke

993 twin turbo: 245mm 11 blade fan, 1:1.8 pulley ratio, 1,210 lps/ 2563.845cfm @ 6,100 crank rpm. (why is this less effective than the old 226 fan at the same ratio?)

Isn't the lost efficency due to the curved blade design of the 993 fan (put in place to reduce noise at the cost of lost air volume)?

*edit* Back in January I made the "curved blade design" comment above and have since realized that the 993 TT uses the flat blade fan (the non turbo 993 uses the curved fan) - an error on my part.

Walt Fricke · 01-12-2013, 10:45 PM

I think you are right - it wiil remind me not to want a 993 TT fan just because it is a newer part.

By now, Crummasel (is that as in krumm Esel?) may be getting discouraged that no one seems to think what he is wondering about is worth wondering about, much less doing. In the mid-80s, everyone with a 5 bladed fan was eager to get rid of it for an 11 bladed fan.

neilca · 01-13-2013, 05:42 AM

For what it is worth, I ran a 5 blade fan on my stock 2.0 S configured engine (126 hp) in the race car. Standard pulley ratio. Reved it to 7500 rpm. Seemed to work fine.

crummasel · 01-13-2013, 07:19 AM

Quote:

Originally Posted by Walt Fricke

I think you are right - it wiil remind me not to want a 993 TT fan just because it is a newer part.

By now, Crummasel (is that as in krumm Esel?) may be getting discouraged that no one seems to think what he is wondering about is worth wondering about, much less doing. In the mid-80s, everyone with a 5 bladed fan was eager to get rid of it for an 11 bladed fan.

OK, thank you for the information

I will give it a try at least in wintertime and record some head temperatures to see where are the limitations.