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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948 hits the track for it's maiden spring voyage!

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948 hits the track for it's maiden spring voyage!

Post  docwyte on Sun Mar 20, 2011 9:23 pm

Got the car out on the track this weekend for the first time this season.

Over the winter I did a cam swap and retune (372.4rwhp, 360ft lbs), added an adjustable rear brake proportioning valve and tied up a bunch of loose ends.

Over all the track sessions went well. I was able to figure out what position the brake proportioning valve needed to go in, with a minimal amount of sphincter tightening moments! Brake oversteer is fun, M'kay? Not so much!

Motor ran really well and was consistent in power. I had to add some fluids (coolant and oil), but the coolant levels stabilized and I didn't need to add any more. I ran 8 sessions and added maybe 1.5 quarts of oil, so not too bad there.

I'm keeping an eye on the coolant level, I may have a leak somewhere, but it isn't evident. Nothing on the ground and no crustiness anywhere in the engine bay. We'll see...

Also keeping a close eye on oil and coolant temps. It wasn't a very hot weekend, around 70 degrees. My oil temps were around 230-240F, coolant temps pretty close to that. The American Iron (camaro/firebird) racers are telling me my oil temps are in range, but coolants temps are high.

I'm running the stock 951 radiator, I'm thinking that's the issue as it's probably 20+ years old. Are there "upgraded" larger radiators available that don't cost an arm and a leg?

If not, I'll just go with a new factory radiator, I'm sure that'll be much better than a 20 year old one! Ironically that's one of the few remaining parts on the car that I haven't changed yet...

Car pulled like a freight train! I was easily hitting redline in 4th gear on the back straight, showing 135 mph. More is there if I get a better launch onto the straight and I'm not such a wimp going into the braking zone.

I need to work on my corner speed and not hitting the brakes as hard. I was too timid in both those respects as I didn't have confidence in the brake bias early on and this is the track I'm least comfortable on. (High Plains Raceway)

Car sounds awesome! Big time V8 acceleration noises and pops and burbles on decel. Plus it shoots fire balls out the tailpipes! All the other racers in my group commented on it.

I turned a 2:08, I know I can do a 2:04 once I get it all together. All was well until I packed up and left the track.

That's when I noticed my check engine light was on. Motor was still running fine, so it's probably something stupid and I ignored it. Got home and stupidly decided to try to back my car with tire trailer up into my driveway.

This is something I usually never attempt to do as the trailer is so short it's hard to control and very easy to jack knife it. I usually pull up in front of my driveway, un hitch the trailer and push it into my garage.

Well, a moment of inattention was all it took as I was backing the trailer up and unbeknownst to me it'd jack knifed and I ended up backing my car up into the trailer!

Ended up denting the drivers third quarter panel, (below the fender character line luckily) as well as punching a hole in it! :banghead:

DAMN IT! All my fault too, so no one to blame.

Guess it's hitting the body shop now. Only bright spot is I can have them repaint the drivers front fender, as the clear coat is peeling on it and the color match is off courtesy of a repair done to it before I got the car. Depending on how much the repair costs I may go with 968 mirrors too, as I can just get the body shop to install them.

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Re: 948 hits the track for it's maiden spring voyage!

Post  laptop_geek on Sun Mar 20, 2011 10:02 pm

Glad to hear she is running well.

Sorry to hear about the damage, but would like to see your rig. Sounds interesting.
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Re: 948 hits the track for it's maiden spring voyage!

Post  xschop on Sun Mar 20, 2011 10:16 pm

Try a 160 deg. T-stat
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Re: 948 hits the track for it's maiden spring voyage!

Post  docwyte on Mon Mar 21, 2011 9:10 am

T stat won't make any difference. I'm exceeding the temp of the current t stat as it is, so it's wide open. Whether it opens at 160 or 170 won't help much when the temps are hitting 240...

I'm thinking radiator. Any thoughts Eric? Car runs stupid cold on the street, just hitting these temps on the track. When does the high speed fan kick in?

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Re: 948 hits the track for it's maiden spring voyage!

Post  Porch on Mon Mar 21, 2011 9:19 am

Make sure you have a clear path to the radiator. That includes the ducting that the factory put on there and the "bat wing". You probably have aftermarket for some of that (splitter?), but just make sure the air can't get out without going through the radiator. Some of the turbo stuff is designed to direct air through the intercooler, you might be able to re-engineer it to direct it into the radiator. For that matter, you might have the holes above the radiator open because of your air intake. Make sure you close those off like the factory did.

Your fan should not be running at speeds higher than 35, it will only slow the air down.

Aftermarket radiators are available (i'll let you search on that because i don't remember pn's off the top of my head). However, i think the 951 radiator is probably the best choice. Most of the aftermarket radiators have smaller surface areas than the 951 and take up more room (i.e. ground clearance). I have never had an issue with the 951 radiator, nor have many others.

Worst case you may be running too much timing.


Last edited by Porch on Mon Mar 21, 2011 9:24 am; edited 1 time in total
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Re: 948 hits the track for it's maiden spring voyage!

Post  xschop on Mon Mar 21, 2011 9:22 am

65% ethylene glycol
30% Water
5% Methanol
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Re: 948 hits the track for it's maiden spring voyage!

Post  Admin on Mon Mar 21, 2011 11:01 am

Sound to me like it's going lean on the top end, What is your timing and fuel pressure at the times it's getting that hot?

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Re: 948 hits the track for it's maiden spring voyage!

Post  948 on Mon Mar 21, 2011 11:21 am

What Porch said!....I found a measureable diff in temps with and without the bat-wing.

Use as much distilled water to antifreeze as you can get away with for your climate. As water % goes up, the specific heat capacity goes up. A 25%/75% antifreeze to water ratio has a 10% higher specific heat capacity than a 50%50% mix; the boiling point will only drop ~ 10 degrees F.
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Try to stay away from Methanol as it is famous for attacking aluminium....and you have quite a lot of aluminium in your cooling system.
IIRC Methanol was used in the early 1900's as antifreeze, it was replaced by EG.


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Re: 948 hits the track for it's maiden spring voyage!

Post  948 on Mon Mar 21, 2011 11:22 am

Also, any vids for us to feast on?
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Re: 948 hits the track for it's maiden spring voyage!

Post  948 on Mon Mar 21, 2011 11:30 am

docwyte wrote:T stat won't make any difference. I'm exceeding the temp of the current t stat as it is, so it's wide open. Whether it opens at 160 or 170 won't help much when the temps are hitting 240...

I'm thinking radiator. Any thoughts Eric? Car runs stupid cold on the street, just hitting these temps on the track. When does the high speed fan kick in?

Though I think you are on the right track in regards to resolving your problem....here is something else to consider. I found that, for the LTX, various t-stat's had differing open cross sectional areas. Ironically the stock Wahler t-stat had a 15% larger area than their "low temp" t-stat; they both opened axially the same amount. Question
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Re: 948 hits the track for it's maiden spring voyage!

Post  xschop on Mon Mar 21, 2011 11:53 am

Doc, in your situation, I would worry more about overboiling than a higher specific heat capacity. The methanol at 5% conc. is miscible in water and just breaks the surface tension so the coolant flows faster, only reason I suggested it. I've run that exact formula in water-cooled high compression bikes and the 5% methanol helped lowered the temps at constant high rpm.

Also I'll say it again, the Turbo and some NA radiator have stainless pull rods inside the channels. If you remove the passenger's side tank by un-crimping the aluminum side clamps carefully, you can remove the 20 years of crud and just leave the rods out. You can look inside the "IN" port on the driver's side of the radiator and see if yours has them or not....FYI
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Re: 948 hits the track for it's maiden spring voyage!

Post  948 on Mon Mar 21, 2011 4:31 pm

A 5% Meth to water ratio would have a boiling point of ~ 200 degrees F, compared to straight water at 212.
So before you even add the EG you may have reduced the boiling point by 12 degrees.....I don't know if that would translate when adding EG though.

I do agree that the Meth will work very well as a surfactant, which will help reduce the chance of nucleation in the hot spots; something I am sure you will find on a high comp race motor.
Redline sells this =>> [You must be registered and logged in to see this link.] Not sure what it is though….

Didn't know about the pull rods. I have an old rad, I will have to take it apart for a look, see how much area is being taken up.
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Re: 948 hits the track for it's maiden spring voyage!

Post  docwyte on Tue Mar 22, 2011 8:56 am

Not worth it to me to take the time to pull apart the old radiator, I can get a new one for $250 or so.

Think I'm going to replace the radiator, make sure the AC condenser isn't full of bugs, fill with an 80/20 water/coolant mix and add water wetter and see what happens...

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Re: 948 hits the track for it's maiden spring voyage!

Post  Porch on Tue Mar 22, 2011 9:19 am

Just throw money at it?

Okay, but, i hope it fixes your problems.
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Re: 948 hits the track for it's maiden spring voyage!

Post  docwyte on Tue Mar 22, 2011 9:29 am

That's one way of looking at it.

Another way is that my time is worth a whole lot more than $250. I'm not going to spend hours taking apart my current radiator to clean it out when a new one is relatively inexpensive.

There aren't many things in the cooling system. Levels are fine, t-stat is irrelevant in this scenario, outside temps are relatively low. Street temps are more than in line, it's only when I'm on track.

In talking with the Spec 944 and AI/CMC guys, all is pointing at the radiator. It's easy and cheap to replace, so I'm going to do it.

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Re: 948 hits the track for it's maiden spring voyage!

Post  944-LT1 on Tue Mar 22, 2011 9:58 am

I dont think youre gonna be happy with a new stock radiator. I know alot of people are using them and they say they are working fine (dont kill me Paul) but you currenty claim up around 370rwhp with an AC condensor in front of your stock radiator which means your application doesnt quite match those who are using the stock radiator.

What I would do in your shoes and in order....

1.) Since youre already set on removing the radiator and trashing it, go ahead and open it up and see if it shows any signs of causing your problems. Wont hurt to know. We are talking about a 22 year old radiator here.

2.) With the radiator out of the way, go ahead and check out your condenser. If its gummed up, back-flush it only at a downward angle. If any fins are bent (from bugs, rocks, etc) straighten them with a fin comb.

3.) A big thing is to make sure you have the fan shrouded. You want all the air possible to pass through the radiator not around it. Also, seal the areas in front of and around the radiator.

4.) Adjust your water:antifreeze ratio as discussed above.


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Re: 948 hits the track for it's maiden spring voyage!

Post  948 on Tue Mar 22, 2011 12:19 pm

Doc,
Do you have a WP with higher GPM? If not, make that change along with your new radiator. Flow is part of the equation in regards to cooling.

Michael, I think we are on the same page.... Cool

If all else fails then Doc could upgrade to a bigger radiator or add a second radiator like I did....
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Re: 948 hits the track for it's maiden spring voyage!

Post  xschop on Tue Mar 22, 2011 1:35 pm

948 wrote: Flow is part of the equation in regards to cooling...

Given a New 951 radiator with channel rods and a good used one without the rods, I'd choose the later, the flow is significant.
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Re: 948 hits the track for it's maiden spring voyage!

Post  Porch on Tue Mar 22, 2011 4:49 pm

^ But you don't want flow, you want heat dissipation. The radiator can only dissipate heat if the coolant is in it long enough for the heat to be drawn out of it. Considering the size of the radiators on our cars, i think it's a good guess that they flow plenty with the rods in there. After 20 years, maybe not, but that's why radiator places offer flushing services.
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Re: 948 hits the track for it's maiden spring voyage!

Post  Porch on Tue Mar 22, 2011 4:52 pm

docwyte wrote:That's one way of looking at it.

Another way is that my time is worth a whole lot more than $250. I'm not going to spend hours taking apart my current radiator to clean it out when a new one is relatively inexpensive.

If you just have $250 to blow, then it's not a bad guess...but you ignored several free fixes that might have as much of an impact and would take a lot less time than replacing a radiator. I'm not saying a radiator won't fix it, i just hope you realize that there's a possibility that it won't, and you'll have wasted not only your time but $250...
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Re: 948 hits the track for it's maiden spring voyage!

Post  eclou on Tue Mar 22, 2011 8:19 pm

depending on the venue, some tracks don't allow antifreeze in the radiators due to the uncanny ability for spilled antifreeze to cause spin-outs
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Re: 948 hits the track for it's maiden spring voyage!

Post  Arthropraxis on Tue Mar 22, 2011 8:43 pm

I have never been on a track that allows antifreeze. Always has to be straight water, they check it at tech prior to practice.
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Re: 948 hits the track for it's maiden spring voyage!

Post  948 on Tue Mar 22, 2011 10:43 pm

Porch wrote:^ But you don't want flow, you want heat dissipation. The radiator can only dissipate heat if the coolant is in it long enough for the heat to be drawn out of it
Sorry Porch, that is a common misconception. To a point, higher flow means more cooling. The rate of heat transfer is (flow rate x specific heat x temp diff) + (flow rate x latent heat diff).

The following is a very good cooling guide. The third page mentions flow rate. [You must be registered and logged in to see this link.]
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Re: 948 hits the track for it's maiden spring voyage!

Post  docwyte on Wed Mar 23, 2011 8:45 am

Most track groups allow street cars to run anti freeze, only the race cars have to run just water. I've never had to flush out my cooling system and only run water in any event over the last 15 years.

I understand what you're saying Porch, but I simply don't have the time to play around with this stuff, then go to the track and discover it didn't work. The temps are high enough in the car that I very much doubt that ducting, or air flow is the issue. It may be part of the problem, but isn't the genesis of it.

Plan is to replace the radiator, fill with more water than coolant and add water wetter and see what happens...

As far as I know I'm running the stock water pump.

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Re: 948 hits the track for it's maiden spring voyage!

Post  Porch on Wed Mar 23, 2011 7:24 pm

948 wrote:
Porch wrote:^ But you don't want flow, you want heat dissipation. The radiator can only dissipate heat if the coolant is in it long enough for the heat to be drawn out of it
Sorry Porch, that is a common misconception. To a point, higher flow means more cooling. The rate of heat transfer is (flow rate x specific heat x temp diff) + (flow rate x latent heat diff).

The following is a very good cooling guide. The third page mentions flow rate. [You must be registered and logged in to see this link.]
Fair enough, but clearly there is a balance to be had. The Porsche engineers put the rods in there for a reason, i wouldn't take apart a perfectly good radiator to remove them.
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