Affect of underdrive pullies on an open track car? - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 16 Old 10-01-2009, 02:31 PM Thread Starter
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Affect of underdrive pullies on an open track car?

Guys, I recently hit Buttonwillow Raceway in 100* degree heat and experienced some minor overheating. The motor ran hotter than I wanted it to... granted this with a 150k motor, iron heads, brass 3-core radiator, a Mark 8 fan, and the stock temp gauge but I've always had good luck with my stock gauge. I do plan on bringing my infared gauge with me the next time I go to the track.

Does anyone know if under drive pullies will affect my pump output on a road course in some way or another?


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post #2 of 16 Old 10-01-2009, 03:01 PM
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Does anyone know if under drive pullies will affect my pump output on a road course in some way or another?
Yes.

OEM pumps are designed to work most efficiently at highway cruising RPMs -- somewhere between 1800 and 2500 RPMS in most modern cars.

On the track, you're running near the redline almost all the time (if you're not, you should be.) This is well above the pump's designed speed and almost all OEM pumps will cavitate. This results in less coolant actually being pumped and you get less cooling out of the system.

Race pumps are designed to be less cavitation-prone and will do a much better job at high RPMS.

You can help both OEM and race pumps by lowering the pump's speed with an undersized crank pulley and an oversized pump pulley. How much this helps depends on how badly the pump was cavitating.

So give it a shot. Pulleys can be an easy and cheap fix.


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post #3 of 16 Old 10-01-2009, 03:15 PM Thread Starter
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Yes.

OEM pumps are designed to work most efficiently at highway cruising RPMs -- somewhere between 1800 and 2500 RPMS in most modern cars.

On the track, you're running near the redline almost all the time (if you're not, you should be.) This is well above the pump's designed speed and almost all OEM pumps will cavitate. This results in less coolant actually being pumped and you get less cooling out of the system.

Race pumps are designed to be less cavitation-prone and will do a much better job at high RPMS.

You can help both OEM and race pumps by lowering the pump's speed with an undersized crank pulley and an oversized pump pulley. How much this helps depends on how badly the pump was cavitating.

So give it a shot. Pulleys can be an easy and cheap fix.
Interesting... I already have the March underdrive pulley set on the car, and the temp gauge was through the roof and I was certainly spending much of the time near the limiter. Way back wen before I did my first track event, my friend advised not to use the 93 Cobra water pump pulley as it was too small, and might lead to cavitation when used in conjunction with a smaller crank pulley. Maybe I am simply not getting enough coolant flow and a set of stock pullies would suit me better?

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post #4 of 16 Old 10-01-2009, 03:33 PM
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You probably straight-up need more radiator capacity. Going from a 3-core copper to a 2-core aluminum with larger cores dropped my coolant temps dramatically, and prior to that, I could rarely finish a session thanks to overheating. This is with a March underdrive crank and WP pulley, revving to 5800 max.

Last edited by MFE; 10-01-2009 at 03:36 PM.
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post #5 of 16 Old 10-01-2009, 03:56 PM
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You need to get a real gauge. The infrared thermometer will not give an accurate measurement of the core temperature of the engine. You need lots of water flow and lots of air flow to cool a 5.0 on the track. One thing I noticed about your car is the openings in the bumper are small. Pulleys are cheap and easy but don't rule out air flow.

I've been chasing an on track overheating problem for 3 months now. I replaced everything in the system, head gaskets, t-stat (now no t-stat as it's a track only car), new water pump, new alum radiator, verified the a/f mixture on a dyno, verified the gauge was accurate. None of this worked. I've now blocked off the air from flowing over or to the side of the radiator. In simulated track conditions it seems to have worked, but we will see this weekend. . .

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post #6 of 16 Old 10-01-2009, 06:04 PM
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Also consider a heat extractor hood, whether via buying a completed hood, adding louvers to an existing hood, or adding the 2010 hood vent to your hood.

Also, I thought underdrive pulley sets were a bad idea because they slowed down the water pump, thus decreasing the circulation speed of the water in the system. Am I in left field on that one?
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post #7 of 16 Old 10-01-2009, 06:54 PM
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As said above, get a real gauge asap.

I would not be racing my own cars without an aftermarket autometer gauge so you are confident about the temperature values. In addition consider the following in this order:

a.) Although the effects of the e-fan decrease the faster you go, are you sure its operating properly. I had some relay problems for a while that caused me temperature problems (wasn't entirely obvious at the time)

b.) Check Stat

c.) Aftermarket radiator

d.) Stock pullies

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post #8 of 16 Old 10-01-2009, 08:54 PM
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I ran into high temps at Buttonwillow/THill with the UD pullies. Going back to the stock water pump pulley with a shorter belt made a big difference. Putting the crank pulley back to stock later on didn't help much more. This was on my 4.6 4V though...

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post #9 of 16 Old 10-02-2009, 09:27 AM
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Quote:
Originally Posted by Coupe de Surf View Post
... t-stat (now no t-stat as it's a track only car)...

WRONG!
You need the fluid to stay in the engine long enough for it to absorb heat, and in radiator to release heat. Whipping cooling thru the system is actually WORSE.


If you calculate the right speed of pump, you can get the right underdrive pulleys to have it flow the proper rate for maximum performance.
I run underdrives, stock waterpump, 2 core aluminum radiator, completely sealed front airbox inf front of radiator, and NO FAN ( not electric, not mechanical, none). No heat issues with S-trim near 500rwhp motor.

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post #10 of 16 Old 10-02-2009, 09:57 AM
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I was heating up some this summer and I increased the size of the deflector on the bottom of the radiator support to 4" and so far this has brought my temps back down.


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post #11 of 16 Old 10-02-2009, 10:15 AM
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I've had all 3 pulley's(alt., water, crank) on my car since appx. 500 miles on the odo. I've also ran a healthy mix of Purple Ice/Watter Wetter in the OE radiator. Temp's have always stayed at the OE spot on the gauge. This on a car with 4.10 gears and the needle stays at the 4500rpm's and up position A-LOT.
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post #12 of 16 Old 10-02-2009, 10:38 AM
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Originally Posted by drudis View Post
WRONG!
You need the fluid to stay in the engine long enough for it to absorb heat, and in radiator to release heat. Whipping cooling thru the system is actually WORSE.
In my case it has helped. I'm sure you've seen this argued to high hell over at c-c.com. I talked to stewart components about it and they recommended not using one on a race car. I was skeptical but it has lowered my temps.

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post #13 of 16 Old 10-02-2009, 11:09 AM
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Quote:
Originally Posted by Luke87GT View Post
As said above, get a real gauge asap.

I would not be racing my own cars without an aftermarket autometer gauge so you are confident about the temperature values. In addition consider the following in this order:

a.) Although the effects of the e-fan decrease the faster you go, are you sure its operating properly. I had some relay problems for a while that caused me temperature problems (wasn't entirely obvious at the time)

b.) Check Stat

c.) Aftermarket radiator

d.) Stock pullies

at one point the relay went out and it boiled over got super hot.





where does a 5.0 get its air from? underneath or threw the vents in the front?


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post #14 of 16 Old 10-02-2009, 11:34 AM
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The slot in the grill and the slots under the bumper. And it should have the little airdam, at a minimum, in order to create the required pressure differential between the front and rear sides of the radiator.
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post #15 of 16 Old 10-02-2009, 02:16 PM Thread Starter
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The slot in the grill and the slots under the bumper. And it should have the little airdam, at a minimum, in order to create the required pressure differential between the front and rear sides of the radiator.
I still have the little stock airdam, my first step is to put my Griffin aluminum radiator in the car and run some Water Wetter and get back to the track. I don't know why my fan relay failed after years of trouble free service, maybe it got too hot? I had a spare which put me right back on the track for the next session luckily.

Seems the verdict is up in the air vis a vis pullies... I'm not taking the t-stat out of the car because this thing logs way more street miles than track miles, so a decent radiator and a real Autometer gauge will be my next steps.

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post #16 of 16 Old 10-03-2009, 04:34 AM
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Originally Posted by drudis View Post
WRONG!
You need the fluid to stay in the engine long enough for it to absorb heat, and in radiator to release heat. Whipping cooling thru the system is actually WORSE.
It's not often that I do this, but I'm going to have to disagree with Darius on this one. Maybe you can bring the tech Darius, but everything that I have read indicates that more coolant flow equals lower temps. Everytime I have done something to improve the flow of coolant through the engine, the temps went down.

A key to adding efficiency to a stock pump is to attach a round plate to the back of the impeller. This helps by eliminating water from spilling out between the back of the impeller and the back cover.




Not too tough to make a round plate and rivet it on to the blade. As far as I can tell, this is the key performance difference between a stock pump and a Stewart Stage I pump. (This excludes any improvement in longevity due to bearings or shaft size.) With this set up, I run a 4" crank pulley and a 4" WP pulley with no overheating issues. I still run a thermostat to aid in quicker warm up, but it is a high flow unit. With 550 NA horspower and Griffin 2 row radiator, I typically can maintain 200 to 210 water temps while pulling each gear to about 6400 rpm on long track sessions.

Another thing you can do that I have mentioned in other threads is to clean up the passages in the timing chain cover. The transitions are usually pretty rough and restricted. If yours has the directional inlets, gasket match them on the water pump side.

on edit:
Although the boiling point is lower, straight water can accept a larger amount of heat than water with antifreeze. If you can keep your temps below the pressurized boiling point of water, you will be better off without the coolant or any additives. Of course an anti corrosive/waterpump lubricant is a good idea. You can get that at your local parts store.

Also a 16 psi radiator cap raises the boiling point of water from 212 to about 226. If you use a 22 lb radiator cap, the boiling point goes up to nearly 239 degrees.

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Last edited by a79coupe; 10-03-2009 at 05:26 AM.
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