Date: Sat, 8 Aug 1998 14:25:42 +0100 (WET DST)
From: Gary and Carol Henderson
Subject: Inlet manifold temperatures
Hi all, especially the world-famous Rienk!
At last we have had a cool Saturday, so I could check out manifold temperature on my Mk 1 Imp during cold-running. (This winter has been a failure so far - no snow on Mt Ruapehu & not very much in the South Island either.) Some people might remember me wondering out loud about this issue - in cold weather, the car has always started OK but fouled plugs (esp 1 & 4) & wanted to stall, until it had been stopped and left to stand 5 minutes or so.
I clamped two K-type thermocouples on the manifold, on the fore-&-aft pipe between branches 1-2 and 3-4 respectively. These went via the rear hatch to a cheap digital 2-channel readout unit inside the car. The 1-2 branches should be coolest, because of both the exhausts being offset towards #4 cylinder, plus cold water into block is at #1 end, so I have had an aluminium clamp setup to pick up a little more exhaust heat.
Started off at 8 degC air temperature; after driving along to the end of my street (about 500 m) the manifold temperature was DOWN to 5 degC! Then down the hill - about 2.5 km and 200m altitude - the 1-2 temp was 18 degC and the 3-4 temp was 16 degC. Gently along the motorway at 50 mph (engine still cold) to traffic lights at exit about 2 km on - temperatures 20 & 18 degC and motor needing throttle to keep running. Drove another 2 km on suburban streets at 50km/h to first destination - temp 29 & 27 degC. Stopped and left car about 20 minutes - before restart temperatures 38 degC, dropping after starting to 18 degC. Another 1 km drive (now with no tendency to stall) to next short stop (to order a couple of oil filters). Before restart, the temperatures were now 49 degC. A short drive about 300 m to traffic lights dropped temps to 20 & 18 degC. Lights green so back along motorway a bit quicker against a head wind - 22 & 20 degC at turnoff to our hill. The Maungaraki hill needs 90% throttle in 3rd gear most of the way for 2.5 km to hold the 50 km/h limit. The temperatures rose to only 27 & 25 degC before turning off onto our more-or-less level street. As I pulled up to reverse into my garage, they reached 40 & 38 degC respectively. Sorry about the drawn-out account, but I think the point needed to be confirmed over a fair range of driving.
I have read that optimum temperature is about 60 degC. The Sport models of course had water-heated manifolds so all of these problems should be unfamiliar to performance-oriented Impers!
What amazes me is that this obvious cause of poor cold-running, plug fouling and the resulting apparent failure of the original automatic choke seems to have been completely ignored by Rootes. Why didn't they have a manifold hot-spot, as always used on Minxes, Hunters, Avengers etc? Does somebody out there have any idea?
Cheers
GaryH
Date: Sat, 8 Aug 1998 22:05:12 +0100 (WET DST)
From: Nickcleak@aol.com
Subject: Re: Inlet manifold temperatures
That was a very interesting experiment ...
Don't forget the cooling effect of the carburettor though , it will cool the air quite a bit as it goes through the carb due to the evaporation effect as in refridgeration systems some times in humid conditions in the winter the fuel can even freeze and block the carb .
it would be interesting to see the air temp going INTO the carb i suspect it will be a lot hotter ! ie 20°C above ambient or so ... optimum is about 30°C as on modern cars , not for power of course but for good drivability and fuel emulsification from cold start ..
nick ...
PS I think Rienk has done similar experiments .. what were your results Rienk??
Date: Sat, 8 Aug 1998 22:53:03 +0100 (WET DST)
From: rienk steenhuis
Subject: Re: Inlet manifold temperatures
hi gary,
thanks for the welcome
is it possible that this problem never cropped up during testing? after all the apex book mentions that the test imps never got cold because of the time limits. another piece of book worm wisdom is to be found on page 11 of tim millingtons book where it says that on mark 2 models there is a provision for changing the inlet spout on the airfilter to a position just above the inletmanifold.
also your story prompts a few questions. do you still use all the shielding around the carburettor area. does your car have the high front suspension (more cool air underneath). did you try a different position for the airfilter inlet? is it possible or convenient to try the same experiment with a different position for the air inlet?
anyway the whole thing may have been a testing blind spot. they where aware of the possibility of overheating, so having problems with things being to cool may just not have occured to them.
minxes hunters and avengers all have front engines and lots of cool air entering the enginebay. an imp engine with all the shielding in place doesn't have any natural circulation around the carburettor and any heat that gets in there is more or less trapped. so perhaps they thought heat would built up quick enough. and i imagine all the testing was done with lower front suspension than the public got. (see above)
from your story it would seem that when you stop the heat soaks up in the inlet manifold and as soon as you start off the incoming air cools things quickly.
rienk... don't push me.... everyone will get an autograph....yes..yes after the show...boy i could get to like this being famous but it shure takes it out of you.... please don't push.....
Date: Sun, 9 Aug 1998 06:34:01 +0100 (WET DST)
From: Roger W.Swift
Subject: Re: Inlet manifold temperatures
Practical Motorist June '74 pages 33 to 34 has an article showing you how to cure this! Still took 10 years to get there even if it wasn't Rootes!!
Cheers Roger W. Swift
Date: Sun, 9 Aug 1998 10:55:04 +0100 (WET DST)
From: Gary and Carol Henderson
Subject: RE: Inlet manifold temperatures
Hi Nick
Good thought. My first interest was to see how different the 'plain' and 'modified' ends were.
Thanks
GaryH
Date: Sun, 9 Aug 1998 10:55:06 +0100 (WET DST)
From: Gary and Carol Henderson
Subject: RE: Inlet manifold temperatures
Hi Rienk
I used to run with the 'export' shields in place, but they are a *#%!!! nuisance and suburban NZ has 100% sealed roads.. No noticeable difference in real behaviour.
I have also fiddled the air-filter intake to a position quite close to the #4 exhaust in the past. Again, no noticeable difference in our climate. And we are a genuine high-pivot Mk 1.
The experiment certainly proves that stopping for a few minutes allows heat to soak back into the manifold; also that my simple added fin helps (if only very little - it was done very conservatively lest overheating should result - fat chance!). I think I'll make fatter ones for both ends of the manifold, as the added plumbing to water-heat the original manifold would make quite a dog's-breakfast of the engine room.
I also have the original Mk 1 radiator with heater-return stub to the bottom-tank - I realize that this slows warmup of coolant if using the heater, but I am willing to suffer a little for my car so usually leave the heater OFF for short runs.
Thanks for your interest.
Cheers
GaryH
Date: Sun, 9 Aug 1998 10:55:11 +0100 (WET DST)
From: Gary and Carol Henderson
Subject: RE: Inlet manifold temperatures
Hi Roger
Thanks for the reference. I don't have a PM archive here, so could you please describe in very broad terms, what their tactic was?
I guess that even replacing the cast-iron saddles of the long manifold bolts with aluminium ones would help.
Thanks again for your interest & info.
Cheers
GaryH
Date: Sun, 9 Aug 1998 12:10:34 +0100 (WET DST)
From: Roger W.Swift
Subject: Re: Inlet manifold temperatures
Hi,
Dead easy - A length of 1/2" copper tube strapped to the manifold, wrapped in reflective aluminium foil and held together with plastic padding! Then connected into the bypass hose just like the sport manifold
Incidentally, this was for improved fuel economy, not cold running.
Claims up to 16% improvement on short journeys - lower on longer runs.
Roger
Date: Sun, 9 Aug 1998 12:40:56 +0100 (WET DST)
From: Gary and Carol Henderson
Subject: RE: Inlet manifold temperatures
Hi again Roger
Thanks! I guess that plastic padding is what we call 'bog'....There are aluminium-loaded versions available which would up the thermal conductivity for even more effect.
On manual-choke cars, the problem would be camouflaged by simply making more use of choke than the correct situation would require. The auto-choke original settings gave crazy amounts of fast idle, especially when you have to start your journey with a 2.5 km medium-steep downhill run so would like a bit of engine-braking! (The car tends to gain a bit of speed down there in 3rd gear even when hot.)
Cheers
GaryH
Date: Sun, 9 Aug 1998 13:56:56 +0100 (WET DST)
From: rienk steenhuis
Subject: Re: Inlet manifold temperatures
>PS I think Rienk has done similar experiments .. what were your results
> Rienk?? >-----------------------------------------------------------------
well i did measure underbonnet temperatures but for different reasons. overheating, not coldweather driving. i don't think it has any connection with Gary H problem nor does it make very exciting reading. so be warned.
here is an excerpt from the impfiles.
franka's car had a tendency to run hot. so i needed to investigate. the car in question is a slightly tuned sunbeam stiletto. color moonstone metallic. numberplate 76-10-PN. it has been lowered approximately 2 inches all around. it has a 998cc engine. with a R17 camshaft and two 150CDS stromberg carburettors breathing through K&N airfilters.no airbox. no front spoiler. it has a serck-marston 4 row radiator and at the time a 82degrees celcius thermostat. also fitted are a thermostat for the oilcooler and a janspeed smallbore exhaust system coupled to, at that particular time, a whopping big homemade silencer.
needless to say things where tight in that little enginebay.
this means no metal shields between carbs and exhaust box. only just enough space to burn your fingers when trying to adjust the jets.
i fitted four diode type temperature sensors. the first between the oilcooler and the carburettor. the second on the inside of the enginelid just left of the numberplate. the third was fitted between the fan and the radiator measuring the temperature going into the aforementioned item and the last one connected to the stone guard and therefore strategycally positioned to measure the waste heat. these four sensors i then connected to a digital read-out device equiped with a four way switch to read the temperature of each sensor in turn. the whole system had been extensively tested and callibrated beforehand to be accurate to within two degrees celcius. the date for testing was set at the fifth day of august 1995 , 7 pm. the first day of our hollyday.
sounds like a bad detective novel doesn't it. go over it again and read it in a steady level voice. like dan akroyd in the dragnet spoof. anyway all the above isn't completely superfluous ,since airflow plays a major part in all this. so lets start bringing in some numbers.
1 =
2 =
3 =
4 =
t =
dt =
~ =
+ =sensor between oilcooler and carburettor
sensor behind numberplate
sensor in front of radiator
sensor behind radiator
car temperature gauge
temperature differential over the radiator
just past or just in front
well past
1 2 3 4 t dt remarks 27 22 26 27 0 1 stopped after 400 meters 25 23 27 25 0 - drive off 5min later 27 23 26 33 0 7 city driving 32 24 25 39 0~ 14 city driving 34 25 29 42 1/4 13 main road 90kmh 37 27 32 49 ~1/2 17 main road (prins Clausplein) 80kmh 42 32 34 52 1/2 18 main road (Delft) 80kmh 48 34 36 56 1/2 20 main road 80kmh 51 34 38 59 1/2+ 21 main road (terbergse plein) 100kmh 47 38 40 64 1/2+ 24 main road 90 kmh max.measured temp. 47 36 39 60 1/2+ 21 main road 80kmh
heater was on 1/2 all the time. outside temperature was 22 degC when we started all sensors showed 21 or 22 deg. we stopped at a gasstation and let the engine cool with the engine lid open for about 20 min.
end of journey
1 2 3 4 t dt remarks 31 25 36 51 0 15 driving off 38 29 34 51 0~ 17 90kmh 43 32 36 54 1/2 18 80kmh 44 32 37 58 1/2+ 21 90kmh 49 32 37 62 1/2+ 25 (stampersgat) 90kmh 45 31 37 59 1/2 22 80kmh 46 33 37 60 1/2 23 90kmh heater switched off 48 33 37 62 1/2 25 90kmh 41 29 37 63 1/2 26 90kmh 41 29 36 64 1/2+ 28 90kmh 39 27 35 63 1/2+ 28 95kmh 38 24 35 64 1/2+ 29 90kmh 36 25 33 54 ~1/2 21 80kmh heater on 1/2 44 29 33 54 1/2 21 90kmh 53 30 33 64 1/2 31 standing still at traffic lights
1 shows the rising heat from the exhaust (especially last entry).
1 =
2 =
3 =
4 =
t =
dt =
~ =
+ =sensor between oilcooler and carburettor
sensor behind numberplate
sensor in front of radiator
sensor behind radiator
car temperature gauge
temperature differential over the radiator
just past or just in front
well past
2 shows mainly the effect of the evening getting cooler as does 3.
4 shows the 10 deg difference when the heater is put on and the fact that it doesn't help when you're standing still. surprise. i also made a list of the horsepower i think is needed for a certain speed.
waste heat from cooling system and exhaust together is more or less double this figure or 38.8kw @120kmh enough to heat up a fair sized house in a cold winter. we did further testing during our stay in england. the only extra information from this was that everytime the car had to stop in traffic heat would soak upwards and then stay there. so every time we drove of it was with a slightly hotter engine. the maximum temperature (sensor 4) was 84deg C.this was in london traffic with the outside temperature at 34 deg. i can only guess the water but let me assure you that the gauge was well in the red bit. and we had the heater on which means we were too. this is one of the experiments that lead to the spreadsheets on franka's impsite. i also tried blanking the space between the radiator and the rear crossmember and opening the enginelid rallystyle. neither made a lot of difference. the first was worse at lower speeds and only 2 deg better at higher. the second made no difference at all. maybe because of the louvres. my conclusion is that the fan gets preheated air coming over the engine and not from the back through the louvres. (no shields remember). i have since made a smaller silencerbox but this still doesn't give enough room. i haven't done a similar experiment since. maybe someone else is willing to have a go?
80km
90km
100km
110km
120km8bhp
11bhp
15 bhp
20 bhp
26bhp=
=
=
=
=6kw
8.2kw
11.2kw
14.9kw
19.4kw
as i said before, i don't think it has a lot to do with your problem gary, except that it maybe explains why i asked you those questions. hope i haven't bored the socks of you, but you did ask nick
rienk
ps i once noticed that the temperature gauge dropped sharply past 140kmh does this mean that the airflow has a sudden change there?