schubee

Wow, that is a coincidence. Maybe a long lost relative?

I didn't mean to hijack this thread but the last time I was at the 76 off La Paz was in November of last year. That was the first and last time I was there.

I'll keep you updated on my rebuild. I'm also interested in checking out your 993 drivetrain!

Regards

Cupcar

The 964's normal chip is programmed for 90 octane or better and should not ping if everything is working.

Having said that go to http://www.76.com/products/76racing.asp and scroll down to the mixing charts to mix octane of your choice up to 100

BTW the Cosby Oil site shown in a prior post as having Uniou 76 race gas in San Diego may not carry Union 76 100 octane unleaded any longer. The good news is that they have Sunoco Unleaded 100 available at their pumps now but you need to apply for a Cosby Oil race gas credit card to use the pump.

scotsman60

OK - Here's the update.


This weekend I went sailing and didn't work on the Porsche at all - beautiful weather, great sailing, lots of fun and no motors involved....

I also confirmed that the 76 station on La Paz and Cabot at the Lap Paz exit of the 5 freeway does sell 100 octane race gas. This is way more convenient for me even though you can only enter this gas station from Cabot and the exit causes the car to ground at the front....

I set about investigating my _perceived_ oil cooler fan problem this evening. Turns out that the oil cooler fan appears to be working correctly. I tried most of the diagnostics and tests provided on Randall's site (thanks Randall) and confirmed that the fan came on in slow speed when the oil temp at the cooler reached about 214. I measured the temp at the oil cooler using a thermocouple clamped to the hose coupling with a tie wrap.

I also checked the oil temp at the engine by attaching the thermocouple to the oil return line, close to where it exits the case. The results were surprising. The thermocouple measured 218 and the gauge was at the tick mark just below horizontal, 230 and the guage was above the tick mark but below horizontal - at this temp the oild cooler temp was measured as 198. The peak temp i measured at the engine was 258 degrees with the guage above horizontal but below the second tick mark.

The temps I'm measuring at the engine seem to be significantly higher than the temps indicated on Randalls site. Of course, I'm measuring the temp at a different location than the sender for the gauge (It's difficult to see how I'd get the thermocouple in there).

Should I expect the temps in the oil return pipe to be higher than the temps at the sensor on the top of the motor?

No matter what, I beleive that my detonation problem is being made worse by the higher temps that occur when the car is stuck in traffic so I have a two part plan.

1) Immediately disconnect the oil cooler thermistor and force the fan to work permanently at high speed.

2) Modify the behavior of the fan to force it to kick in at a lower temp (not quite sure which temp yet) and to kick in at high speed only. I'm thinking that this can be done by putting a resistor in paralell with the oile cooler thermistor to bring the total resistance down which should trigger the CCU earlier and then jumpering the low speed power supply pin and the high speed power supply pins on the blower relay. The goal is to keep the fan off during normal driving but get maximum cooling as soon as temp starts to rise when I get stuck in traffic.


More later,



Doug

JasonAndreas

Are there any air leaks at the rear blower motor connections? There are 3 connections, 1) almost directly above and to the left of the big cooling fan, 2) directly in front of the rear blower motor, and 3) right next to the left side motor mount. With the car running you should feel absolutely no air leaking out of the plastic ducting and I know for a fact your car will heat up a lot quicker if don't put all three pieces back on just perfect (I discovered this after my first DIY valve adjustment)

Randall G.

Hey Doug,

Besides modifying the relay, another way to get the fan to run in fast-speed instead of slow-speed is to replace the ballast resistor with a wire of adequate gauge. The ballast resistor being what causes the fan to run in slow-speed, lopping off about 4V from the 12V supply.

Of course, the ballast resistor is a PITA to get to.

Besides installing a resistor in parallel, another way of controlling the fan is to install a switch on the G-12 line. If you want fast-speed operation, flip the switch, which simulates disconnecting the oil cooler temperature sensor. Of course, this requires operator action, besides an "invasive" switch in the cabin.

Just more options.... Oh, and thanks for checking out the La Paz 76 station. Good to know it's there.

scotsman60

Jason,


There are no leaks as far as I can tell. I replaced one piece of the shroud about a year ago because it wa trashed but everything else looks in good shape.



Doug

scotsman60

Randall,


Any comments on the discrepancies in the oile temps I measured on the return lines?




Doug

Randall G.

Hey Doug,

Not sure what to make of your readings. But, it sounds like you're using a thermocouple to measure the outside surface of the line. If so, it seems possible that the line is being heated by adjacent engine components. Perhaps try taking some readings in the adjacent area, see what you get? On the other hand, the oil cooler is in a nice, cool location, with the lines unaffected (actually cooled) by nearby surfaces.

Or, is it possible that so much cooling occurs between the oil return lines and the oil cooler? Doesn't seem likely. I'm grabbing at straws here...

Anyway, if your thermostat is opening, the fan is running as it should, and the gauge reads normal, I don't think you have anything to worry about. If your engine has been rebuilt, you might have to worry about the tinware around the cylinders being installed correctly. I've also heard the tinware can rust out in areas where salt is used on the road.

Jeff Curtis

Good topic, as after thinking that I "cured" my pinging issues by changing out a BAD spark plug wire that was arcing on the lower valve cover...the pinging has returned in annoying fashion.

I had the car at an event mid-February with NO issues, it ran like a scalded dog, no audible pinging, pump gas.

I use 110octane (leaded) in my Toyota Sports Racer and will surely sink a few gallons of it into my 964 in the next few days to see if the pinging subsides - this is getting ANNOYING as I have NEVER had pinging issues since purchase!!

I have, however, put in a performance chip...but that was last April...and I've done probably 12 events with the 964 since installing the chip, races and all.

SOMETHING is degrading internally or a sensor is goofing out - is my best guess.

SO, just so you know you're not alone and I'm currently developing a plan to alleviate the engine from pinging - if I can't find the source of the problem...BYE BYE chip!

Dave R.

Doug,

you asked: I'd say yes.

Seems to me that the hot oil exiting the crankcase travels a long way before it gets to the temp sensor on top of the motor.

The oil temperature sensor that drives the oil temp gauge in the dash is located on the top of the motor (as you pointed out), and it is reportedly adjacent the oil pressure sensor. So I assume both sensors are tapping the same oil source, which has to be the output from the primary stage of the oil pump (oil going into the motor rather than coming out). Given that assumption:

When hot oil leaves the crankcase it travels through the oil return pipe (which is what, 4-6 feet long?) to the oil filter, then (when the oil thermostat is open) all the way out to the oil cooler in the front right corner of the car, through the oil cooler, all the way back to the thermostat under the oil tank at the right rear wheel, then a couple feet or so to the primary oil pump, and THEN near the exit of the primary oil pump gets its temperature taken before being squirted through the engine. The primary oil pump might heat the oil slightly, and the portion of the oil return line that runs next to the primary muffler might pick up some heat but everything else between the crankcase exit and the temp sensor location would seem to cool the oil.

Randall's question of whether the thermocouple reading at the oil return line location near the crankcase, accurately reflects temp of exiting oil is a good one... In any case the numbers you posted are very interesting.

This reminds me of Arjan's enginetray experiment.

scotsman60

Dave,


When I made my post about oil temps in the return tube I wasn't sure of the oil circuit plumbing. Now I see, as you also point out, that the oil temp sensor is on the inlet (cool) side of the engine. By that I mean that the oil hasn't passed through the engine when it's temperature is being measured which seems is non-intuitive to me...... I would have thought that the oil temp leaving the engine would be a better indication of engine temp since it's not affected by the inertia of the oil cooling system.

So now I have to think about the relative temperature measurements differently. I have been assuming that the temperatures measured by the guage would be close to the temps the seen at the oil cooler inlet however the entire heating and cooling process takes place between these two stations. I can now also appreciate the significant cooling that takes place as the oil travels from the return tube to the oil cooler up front - one data point from my measurements shows that oil temp drops from 230 as it exits the engine to 198 at the oil cooler which is significant and has to be a bigger temperature drop than occurs across the oil cooler.

No matter - the guage temp is what other peoples experience is based on - what's normal, what's abnormal etc. so this is still the indicator that I need to use for reference.


Sorry to ramble - just getting things sorted in my head.





Doug

Dave R.

Doug,

No problem, I respect folks who think things through and you raise good points.

You've got me thinking again about adding a cockpit switch to activate the oil cooler fan, and glad that I'm running a synthetic oil.

jonfkaminsky

I had a similar pinging problem last summer. Came from out of the blue and the car knocked like nobody's business. I have been running 92 octane for four years now, from the same Chevron station and never pinged until last summer. This went away as soon as winter kicked in. We get summer and winter fuel mixtures around here too, so hard to tell if its only ambient temperature related.

Oh- and I have been fighting a code 1134 Hall effect sensor error since that time as well. I'm pretty sure this is related, and this usually comes on after the car is warmed up and driving for awhile. sometimes I don't see it for a day or two- sometimes I see it everyday. I get weird temperatures as well- the car seems to run hotter than usual on cold days when formerally it would hardly get above the second line from the bottom.

Jon

Lorenfb

The 964 DME needs the Hall sensor in conjunction with knock sensors to affect
the timing when pinging occurs.

Laura

Showed this to boss man here, and he said the first thing he would check is the distributor belt. pinging and overheating are both symptoms of a faulty belt. May be time to have it replaced before you make too many other adjustments.]

Laura
Hergesheimer MotorSports