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RE: Turbo MAP & MAT interaction
Ahh - the intercooler. That may explain it. I'm afraid I haven't got a clue
how efficient it is, coz it's a bit of a black art to me. All I know is
there is 3 Litres of water+antifreeze in the intercooler system, and the
radiator for it is mounted infront of the air-con radiator (condenser)
right at the front of the car, so it looks like Lotus wanted to keep the
intercooler working well, at the expense of the air-con. I didn't expect it
to be very good, but what do I know !
Drive well -you bet. I'm off to a local race track next weekend to give it
a real thrashing - I just hope it doesn't rain. I'm hoping to do a couple
of 15 miniute / 5 lap sessions, logging ALDL data on my PC using Paul
Blackmoores' Carbytes as I go. But in the past my brake fluid has boiled
after just 3-4 laps, so I have had to leave early for a change of
underwear.
I don't have enough data yet for cold vs hot vs damp type comparisons,
because the weather has been fairly constant for the last few weeks - i.e
cold and damp. Today is the first hot day (22C scorcher) - but the car is
in pieces at the moment having various radiator/CC/Air Con leaks sorted out
ready for the track next weekend.
I have done some MAT sensor tests though. At Room temp (20C) it measured
about 2K5 ohms. Blow on it (body temp = 37C), and this drops to about 2K.
Hold it over a hot soldering iron (250C + ) and it drops to less than 500
ohms. And the cage containing the thermistor is plastic - not metal. Found
that out when the soldering iron accidentally touched it ! I've cleaned the
sensor up (tri-chloro-ethelyne), and as soon as the car's radiators are
back in I'll see if it's made any difference. I believe the sensor is/was
made by Delphi Automotive, and I have managed to find a similar component
on their website at
http://www.delphiauto.com/pdf/packardpdfs/airtemppps.pdf
Where did you get the info about air/fuel ratio stuff in my PROM ? I am
dissassembling the PROM contents at the moment, mainly to try and find out
what the bytes in the ALDL data stream are. Some things are obvious -
temperatures, pressures, speed, RPM etc, but others like turbo boost
solenoid duty cycle are prooving very elusive. But any help as to the
addresses and function of the various tables would be appreciated. Most of
them appear to be in the 0x8000-0x9000 area of the PROM.
Thanks once again for your help
Malcolm Robb, LC 0112G
-----Original Message-----
From: Scot Sealander [SMTP:Sealand@clarityconnect.com]
Sent: Saturday, April 08, 2000 12:09 AM
To: gmecm@diy-efi.org
Subject: Re: Turbo MAP & MAT interaction
Webmaster wrote:
> Thanks for the reply Scott.
You are welcome.
> But my basic question is still regarding the ALDL/Tech1 MAT(IAT)
> temperature reading. If I unplug the sensor's cable, the value goes to 00
> almost instantly.
That sounds right.
> If I short the sensor out, the value goes to 0xFF almost
> instantly. So, assuming my sensor is good, it looks to me that the TECH 1
> is displaying the raw A/D converter value coming from the sensor.
Sure looks that way!
> If this is the case, should the MAT reading be varying rapidly in
response to
> boost pressure, or only very very slowly in response to falls and rises
in the
> manifold metal temp ?
The temp rise will probably not follow the temp rise out of the turbo.
There
is an intercooler in between! The rate of rise and final temp of the
incoming
air will depend a great deal on the intercoolers ability to cool off the
turbo heated air. If it has a lot of capacity, you will not see a lot
of
temp rise. I must admit to having absolutely no previous knowledge of
your
car, but it sounds like a very "interesting" car. Must be fun to drive!
How does the air temp sensor respond to weather? Do the readings make
sense?
Does it read an elevated temp at hot starts? How did your manual temp
experiments with the bare sensor turn out?
Scot Sealander
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