HOW TO DO AN ADVANCED SEARCH.

Mon Jul 08, 2013 3:56 pm by Admin


For the benefit of 944Hybrids users there are two search functions available for you to use.
The purpose of this sticky is to explain the "Advanced Search" function because it is much more powerful and is the best choice when researching information.

When you log on to the site a list of options is shown in a line at the top of the page. One option is labelled "Search", use this option (NOT the search box lower down on the right).

After you click on the upper search option, a drop down box appears. At the bottom of this box is a radio button marked "Advanced …

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Controlling the water temps on the track

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Controlling the water temps on the track

Post  docwyte on Sun Jun 17, 2012 12:31 pm

I'm having issues keeping the water temps under control on track. On the street they're rock solid at 190F. On the track it's not unusual for me to see 250F. I'm not really comfortable with that, I'd like to keep them around 220-230F.

Setup now is a fresh OEM 951 radiator, with ducting and under panel, factory turbo nose. I am running A/C, so I do have my condenser there, although I cleaned all the debris from it when I put in the radiator.

At this point I'm thinking about cutting a hole where the front license plate mounts, plus cutting a hole in the header panel to let more air in.

I have the double whammy of hot summer temps (mid 90's in ambient air temp) plus the thin air of altitude. I'm not sure what else I can do. Could I get a larger radiator to fit (Griffin, Wizard, Ron Davis?) and would it make a substantial difference?

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Radiator

Post  fliermike45 on Sun Jun 17, 2012 3:08 pm

From experience of three swaps, after the first I have not used a stock radiator.
I have a Griffin 1-26201-X in my 948 and at current FL temps is holding its own. But then my ride is not a track car.

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Re: Controlling the water temps on the track

Post  docwyte on Sun Jun 17, 2012 4:06 pm

You also have more open area in your front bumper than I do. Was the griffin a direct fit?

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Griffin

Post  fliermike45 on Sun Jun 17, 2012 4:40 pm

I would recommend you remove the sheet metal crossmember box from the front of the rad and use Eric's cross member brace. That will allow more air flow.
Here are pics of my modified radiator opening.












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Re: Controlling the water temps on the track

Post  Rich L. on Sun Jun 17, 2012 11:20 pm

Do you have a belly pan? You could also vent the hood. I got a pair of these but so far haven't needed to install them. I might when it gets warmer this summer.

http://www.928motorsports.com/parts/louvers.php

As I understand it, it's not really about adding air in front of the rad. But more about evacuating air from behind it.

Rich
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Re: Controlling the water temps on the track

Post  skywalker01 on Mon Jun 18, 2012 6:19 am

Rich L. wrote:Do you have a belly pan?
[...]
As I understand it, it's not really about adding air in front of the rad. But more about evacuating air from behind it.

Rich

I tried mounting the belly pan over the weekend. Going to need some fabrication work to get it to fit on early models. As for evacuating heat, I have a cowl (fucntional) and I'm still seeing temps at 220~230. Only time I see a drop is when I'm at a stop light.
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Re: Controlling the water temps on the track

Post  docwyte on Mon Jun 18, 2012 8:05 am

I do have a belly pan. No venting in the hood. I figured I needed to get more air in first.

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Re: Controlling the water temps on the track

Post  948 on Mon Jun 18, 2012 12:10 pm

Doc, do you have the heater nipples looped or deadheaded? I have read that deadheading can, in some cases, cause cavitation induced overheating.

Increasing the coolant flow will improve cooling efficiency; have you considered a mechanical pump with higher GPH and optimized pulley? Also a high flow thermostat? http://www.evanscooling.com/assets/ECS-LS1-Product-Info-web.pdf
Increasing cooling surface area will also improve cooling efficiency; you could add a secondary radiator or fit a bigger/thicker unit. A thicker all AL unit, one that "fits" in the OEM spot, will set you back about $700 - $800.....mine cracked after only 3 years of street driving Mad . I now have a secondary radiator where the inter-cooler used to be, which cost less than $150.
Lastly increasing airflow. You are already using the belly pan which helps create a low pressure area behind the radiator. You could open up the front or the back by way of adding hood louvers.....I would work first on the surface area and coolant flow.
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Re: Controlling the water temps on the track

Post  docwyte on Mon Jun 18, 2012 12:15 pm

Not sure about the heater stuff. Eric built the car, so it's however he hooked it up. My hvac (heat and A/C) works normally though.

Does the stock thermostat impede flow? I've heard of lower temperature thermostats, but not high flow ones...

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Re: Controlling the water temps on the track

Post  Rich L. on Mon Jun 18, 2012 12:20 pm

The trick in venting the hood is opening it up to a low pressure zone. Unfortunately, the base of the windshield is a high pressure zone, hence the HVAC intake being located there. The front half of the hood, basically ahead of the shock towers, is ideal for adding vents to evacuate air from the engine bay radiator and increase the pressure drop across the radiator core.

As posted before:

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Re: Controlling the water temps on the track

Post  docwyte on Mon Jun 18, 2012 12:21 pm

Hmmm, ok, so a naca duct or reverse louvers on either side there would help...

I think I'm going to drop the car at the body shop to have them open up the front license plate area, the header panel and maybe vent the hood too...

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Re: Controlling the water temps on the track

Post  Rich L. on Mon Jun 18, 2012 12:37 pm

Some other ideas: I'm sure the thermostat does affect coolant flow somewhat. I'm running a "low temp" one that opens at 160 but it doesn't advertise any reduced flow restriction. How old is your water pump? I read about plastic impellers vs metal ones but I'm not sure which I have with the "stock" pump. Also, is your overflow tank cap reasonably new? If old and leaking pressure it might be reducing cooling system effectiveness. I assume, being in CO, that you're running a distilled water / antifreeze mix.

Something I noticed was in filling the radiator. If I just filled through the overflow tank and then ran the engine, I'd get super high temps at the sender in the head. I bled the system by opening the steam vent which puffed out some air, then some bubbles and finally fluid. This finally cooled the head and I got good temps at the sender.

Anyway, good luck with the body mods.

Rich
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Re: Controlling the water temps on the track

Post  docwyte on Mon Jun 18, 2012 12:40 pm

Ohhh, I've just burped the system through the overflow tank. Where's the steam vent so I can burp it through there?

Water pump and thermostat are the same ones that came with the motor when I got it from the junkyard. Think I should replace them?

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Re: Controlling the water temps on the track

Post  Rich L. on Mon Jun 18, 2012 2:27 pm

That's the little metal tube that comes out from underneath the intake manifold at the front. It's just below and to the driver's side of the throttle body. Mine's super easy to get to because of the lack of the ps pump. Hope that helps.

Changing the pump is a big deal. But swapping in a new thermostat and radiator cap would be cheap and easy.

Rich


Last edited by Rich L. on Mon Jun 18, 2012 2:31 pm; edited 1 time in total (Reason for editing : missed 2nd question)
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Re: Controlling the water temps on the track

Post  docwyte on Mon Jun 18, 2012 2:58 pm

Don't think my cap is bad, but as you say, it's easy and cheap to replace, so I will. I'll bleed through the steam vent (you do this with the motor running?) and replace the cap and t stat and see what happens.

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Re: Controlling the water temps on the track

Post  acorad on Mon Jun 18, 2012 3:22 pm

fliermike45 wrote:From experience of three swaps, after the first I have not used a stock radiator.
I have a Griffin 1-26201-X in my 948 and at current FL temps is holding its own. But then my ride is not a track car.
That's a 16" tall rad. Do you have issues with scraping the bottom of the radiator when driving around town?


Last edited by acorad on Mon Jun 18, 2012 3:30 pm; edited 1 time in total
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Re: Controlling the water temps on the track

Post  Rich L. on Mon Jun 18, 2012 3:23 pm

I did it with the motor off and cold. Hope all that helps, Doc. Be nice to not have to cut up the body to get more airflow.

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Re: Controlling the water temps on the track

Post  docwyte on Mon Jun 18, 2012 3:25 pm

Rich, so you just pulled the hose off of it and waited for the coolant to start flowing before you put the hose back on?

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Re: Controlling the water temps on the track

Post  Rich L. on Mon Jun 18, 2012 6:59 pm

Yes, exactly. Only took a couple seconds.

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Re: Controlling the water temps on the track

Post  948 on Mon Jun 18, 2012 7:04 pm

docwyte wrote:Hmmm, ok, so a naca duct or reverse louvers on either side there would help...

I think I'm going to drop the car at the body shop to have them open up the front license plate area, the header panel and maybe vent the hood too...
Whoa, venting your header panel will only hurt the air flow through the radiator as it will cause an increase in pressure behind it. IIRC you have a 951; that means you used to have a 5 inch thick intercooler in the header panel which caused a restriction for the air flowing into the header and behind the radiator, not much air flow and therefore lower pressure behind the radiator. Now you don't have said restriction which will allow more air to flow into the the engine compartment and effectively reduce the amount of air flowing through the radiator. If it hasn't been done already, i would suggest that this area be closed off from the engine compartment.
I would block off the engine compartment, get a better pump, a high flow TS, add more radiator surface area, and then add louvres.
Check the link in my OP for a HF pump and ts..
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Re: Controlling the water temps on the track

Post  948 on Mon Jun 18, 2012 7:09 pm

I found it best to bleed the system with the car up on a single ramp, drivers side....as high as possible. Heater on. Reving the engine to ~2000 rpm for ~5 minutes. This will help push the air out of the system, once the ts has opened fully.
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Re: Controlling the water temps on the track

Post  acorad on Mon Jun 18, 2012 7:15 pm

docwyte wrote:Hmmm, ok, so a naca duct or reverse louvers on either side there would help...

I think I'm going to drop the car at the body shop to have them open up the front license plate area, the header panel and maybe vent the hood too...
Isn't there an optimal grill opening area/rad surface area proportion? Like 40/100, iirc?
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Re: Controlling the water temps on the track

Post  948 on Mon Jun 18, 2012 7:17 pm

docwyte wrote:Does the stock thermostat impede flow? I've heard of lower temperature thermostats, but not high flow ones...
The HF TS allows more flow than stock. More flow means more cooling. A lower temp TS won't do anything for an overheating engine, and in my experience some have a smaller open cross section than stock temp TS......which means less flow!
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Re: Controlling the water temps on the track

Post  948 on Mon Jun 18, 2012 7:26 pm

acorad wrote:Isn'ti there an optimal grill opening area/rad surface area proportion? Like 40/100, iirc?
Good question. I would assume that that is part of the equation. One would guess that pressure delta between front and rear of the rad would also play an important role.
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Re: Controlling the water temps on the track

Post  acorad on Mon Jun 18, 2012 7:41 pm

I've also read that some heated water from the block gets shunted through a bypass back through the engine instead of going through the rad, and that blocking the bypass will ensure all the heated water goes through the rad resulting in a cooler running engine...
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Re: Controlling the water temps on the track

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