Dealing with heat soak

[sebch]

Hi,
Yesterday I've experienced a bit to steady my CLT temp in local weather conditions. I wanted to do this this because my CLT temp only goes up to 65°C when driving, getting to the 82°C the thermostat is rated for only when in the traffic jams. 65°C is IMO not enough because then I have WE messing in when tuning, and well, I just don't like it!

So before I go for an electrical fan, I thought I might do as they do in africa when the weather is "cold" and their thermostat-less cars get too much cooled down: blind part of the radiator with cardboard.

I installed my cardboard, drove for a while at a nice 82-83°C CLT that was perfect and then bumped into a traffic jam where the CLT reached 95°C, with IAT going from a good 35-40°C to as high as 85°C. Then I stopped at a shop to get some beer and removed the cardboard. When trying to restart (CLT at 84°C and IAT at 76°C), no way I could convince her to start. My diagnosis: heat soak. Do you agree?

Now, as I had the laptop in the car, I tried to fiddle with the cranking PW and as heat soak is creating a lean situation, I tried to make the crank PW pretty high (as much as 4.0 and 15.0 ms). Still, there was no way.

So here's the question: when heat soaked, is it still possible to get the car started by altering crank PW (if yes by how much?) or is sitting in the car for an hour your only option? If altering the PW ithe way I did it can do the trick I'll have to look in non-MS issues, so I'd like to make sure before I go that way!

Sorry for the long post, I thought precision would help in this case! Cheers, Séb

[malloy1]

...correctly.

I found this explanation:

...you can tell if it's heat soak (in that it is ACTUALLY that temperature) or sensor/wiring/configuration error (in that it is NOT ACTUALLY that temperature) by letting the car sit overnight, and then, when you start it up cold in the morning, both the IAT and the CLT temp sensors should both read about the same temperature, ambient. You can even check the temps with the key-on, engine-off.

Where is your AIT sensor located?

Paul

BTW-Are you running MS in a Volvo 122?? I have a 122 with a B21F engine.

[keithmac]

Yeh, both my sensors read the same on a morning (check them with the stock ouside temp sensor as well).

You can do IAT correction in the Extra code, I believe it was put in to combat heatsoak issues but don`t know if it affects cranking pw`s at all?

[sebch]

Well, from what I read on the board, it indeed HAS sth to do with cranking pulses. Hence my surprise that changing this setting wouldn't do the trick.

My sensor and wiring are both up to snuff when I started the car 4 hours later I had both temp sensor displaying identical values that made sense with the outside air feel (still have no OEM sensor in this 40 YO car, though...), so my original question still stands!

My AIT sensor is located wher the cold start injector is located on the K-Jetted (and possibly D-Jetted) B20 engines if that ringsany bells: just after the throttle on the intake manifold. No way it can go elsewhere (eg. in the airfilter box) as there is only room for a cone shaped boxless filter.

The car is indeed a 122, originally a 1965 121 though. By now I should relabel it 124GT though, as the engine is from a 140 series. You can get some info in my success story, it's not too far down the volvo/saab list!

BTW, I'd love to get pics from your own 122 engine bay (and the rest). It's not impossible that I go the B2sth way sometime, so ÃŽ'm on the look for documentation regarding this, although I might want to stick to the B20 by overboring it to 2.1 or 2.3l, as I have a late B20, whose crank is OK for fitting B23/21 conrods and pistons. Here in Switzerland, a 130bhp B20 would still look stock enough in a 121 for the safety inspection provided I put a single carb on it, whereas a crossflow engine could well fail.

Thanks for your answer anyway, and the other's squirter's input is also welcome! Cheers, Séb

[mops]

i got the same problem in my BMW, which i'm working on.

this is that MS for every 10 degrees, it enleans across the board by 3%, so at 70*, it enleans about 12%, which is making engine very hard to run.

With few datalog I found out that cranking pulse will always get the engine to sputter, and then once ve table takes over it doesnt get enough fuel to start, because it's enleaned heaps.

here's what i do (works every time)

crank the engine - once it sputters - then you have to stab the throttle to activate accelenrich. stab must be particular... too fast and you will flood it, too little and it wont run... that will actually get the engine running... until IAT will start reading something more reasonable your car will be running lean... it might not idle by itself....

thats the teomprary solution.

the actual solution to the problem is to get better IAT sensor and put it in more siutable location, where heatsoak wont be such an issue.


hope that helps.

[Keithg]

And when coolant (MAT) related air density correction works properly,
you should be able to use this to help on heat soak start. I have mine
set up to work like that, though you need to make sure it is not
enabled when CLT is below warmup temp.

KeithG
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