grants_968

I saw your 968 several times at HMR during build. Beautiful.

RolexNJ

Mike thanks for the update and good testing too. It sounds like at lower speeds the temps are rising, and the only way it fixes itself is through higher mph speeds or by creating the vents you said?

It is a beauty Grant. I have seen some of the products from HMR too, I just wish they would date their web site. It hasn't been updated since 2006 for both businesses.

Mike O

Its not just low speed. It is traffic jam type stop and go. Normal around town and around the neighboorhood is fine.

And thanks for the flattering comments. She's out in the garage blushing

ehall

That really doesn't sound much different than an average 951. If you rev the engine, you should see the temp drop. Actually if you kkeep the revs at about 1500 rpm it will stay under control. It's also worth re-bleeding the cooling system.

RolexNJ

You are very welcome for the compliment. Please keep this thread updated. And Mike, how about posting some nice shots of the car?


But E, why is this 'the norm?' Mike has a big HMR radiator, Im sure flushed his system, and the thermastat works properly. I am so confused as to why our cars do this. My old 3.0L did it that Lindsey built, and we used a brand new 968 water pump too. This just baffles me. I would think that with all the technology we have today, that something could be done to fix this.

SamGrant951

My car always used to that (temp gauge would rise in traffic or sitting at idle, but would come right back down with a rev or when back up to speed.) When the current motor went in I put in a lower temp thermostat along with all new coolant/heater hoses, new waterpump, fan switch, heater valve, bled the hell out of the coolant system multiple times and it doesnt do it all anymore. It can sit in traffic all day or be on the track mid-summer - temp needle never moves once it settles right above the first white line. Not speaking directly to 968s or your build but something doesnt seem right (at least speaking from 951 experience)... .02

ehall

Sam and rolex,

I believe that when the car sits at idle, the coolant doesn't run through the entire system or if it does, it's moving slowly. I think it goes through the heater core once it hits the proper temp of the thermostat. The rest of the time it doesn't travel through the entire system. I think that's why you see the temp drop by reving the engine, or maintaining revs. If it travels across less surface area, at a trickle, it won't transfer as much heat. Even Sam's car sees this happen, but to a lesser extent.
A big ***, super efficient radiator, like the HMR piece, still requires airflow across the cooling veins, in order to use it's real potential. I'd imagine it's a pretty effective radiator on the track.
I read all of this somewhere, perhaps Clarks or here, but It's been like five years, so I may be off a bit.

Mike O

You are right about track usage, Ehall. I had zero issues there. And I don't have any above 9 o'clock indications in normal driving. Its the traffic jam stop and go (crawl actually) that gets the needle up to 200F.

As far as bleeding the coolant system is concerned, I learned this lesson the first time I flushed a 968 coolant system 8 years ago. I do the first bleeds (at least 3 times) with the front wheels on ramps. Then I will bleed at least twice more after long drives just to make sure. So I'm confident that air in the coolant is not the problem. I did not try a 1500 idle so I'll give that a whirl if I get caught in this situation again.

Duke

I'm interested in your build sheet, please post when you get it back up

What turbo do you have?
Your tune seems pretty conservative, you should be able to get more power at 1 bar than 360 rwhp.
But on the other hand it looks like the run was ended at 6250 rpm, if the engine was run to 6700 rpm you would probably pick up at least 30 rwhp.

Mike O

Duke, thanks for your interest. When I have the build sheet back up I will post the link here. The turbo is a mystery turbo, the builder is one of those secretive types so you have to have his magic decoder ring to know the answer to that question. Yes, the tune is still pretty conservative. The 6200 cut-off is where I plan to limit the engine revs so I felt no need to go beyond than yet. Maybe next year...

ehall

Mike,
I just wanted to follow up. I've owned 2 951's. My current 951 if sitting at idle for a while, will get to the top white line and stay there for a short bit, then the second fan comes on, like clock work and it drops to the 9:00 position. You might start the car and let it idle in the garage (I'd open the garage door though cough...cough...thud! ) and watch the guage to see if your car does the same as mine. It should. If not, you may have an iffy thermostat or a fan relay that isn't quite right.

Mike O

You know, I may not have tripped the fan into high speed. I'll test it in the driveway when the weather gets more Florida like.