Restrictor Plug

[Francesco 71]

How long is your commute? 15 Km, of which the first ~3 Km is stop signs and red lights, then a ~5 Km steady cruise, either highway or parallel service road (I go 65 on the service road) followed by 7 Km of surface streets.

Level road or undulating? Mostly level, with a very gradual climb and descent over the 5 Km segment, maybe 60 feet change.

Also what speed is heater fan at? (I run mine at intermediate untill I get 3 blobs) Intermediate.

Do you run with electric heater on or off? Off. I'll try it with the electric booster tomorrow.

Edited February 27, 2010 by SameGuy

[tolsen 630]

I will try to simoulate your commute in the morning. My gut feeling is that I will get same result as you. The restrictor plug does not generate heat. All it does is increase pressure differential over the thermostat to make it seal positively thereby less or no loss of valuable heat to radiator. The bonus is increased flow through heater matrix hence higher heat output.I did some simplified heat balance calculalations on the engine a few days ago. I only considered specific heat capacities of major parts and fluids. No allowance was made for heat loss by convection to air from engine surface:At half load, 0 C ambient temp, heater fan off, engine will get up to 80 C in 5 minutes. With heater fan on full blast engine will get to 80 C in 10 minutes. The warm up time will be halfed at full load. My calcs assume there is no leakage of warm coolant to radiator.Same calcs done at 1/3 load and engine does not reach operating temperature. Engine does not produce sufficient heat at lower speeds so impossible getting up to operating temperature.

Edited February 28, 2010 by tolsen

[Dang 0]

Going back to high school mechanics, so may well have this wrong, but.......I thought all thermostats allowed "some" coolant to flow through the rad, even when closed? If I recall, it's to prevent coolant shock. You start your car at -40c, so the coolant of course is at -40c. The engine starts to heat up. Once it's gets to the point where the thermostat opens, let's say 30c, you now have -40c coolant hitting your +30c engine. That's super hard on the metal, especially for aluminium. It's like pouring ice water over an overheated engine, which the old manuals warned you not to do as well as it could crack things.The idea of the letting some of the coolant flow through the rad was to slowly bring the temperature up on the coolant in the rad while still restricting most of the flow so the engine heats up faster. This help prevents the shock when the thermostat opens.Am I missing something?Thanks! Dang

Edited February 28, 2010 by Dang

[tolsen 630]

I have not experienced any coolant shock or sudden and rapid drop in engine temperature when thermostat opens.

The thermostat opens slowly - it does not work like a switch. There is still some minor flow of water through thermostat with restrictor plug fitted. See post 49 on Winter thermostat for 0.8 Cdi Engine.

What happens when thermostat starts to open is this: Hot coolant from thermostat flows to radiator. Cold coolant flows out of radiator but mixes with hot coolant returned from heater matrix thereby increasing temperature of coolant before entering V piece at coolant pump. At this point the coolant temperature is increased further because it is mixed with hot coolant from radiator bypass pipe.

Summary: Ice cold coolant from radiator is mixed twice with hot coolant before entering engine.

Having a system diagram in front of you will make it a lot easier to understand the workings of the cooling system.

Edited February 28, 2010 by tolsen

[tolsen 630]

My usual commute this morning (I won't detail what that entails, though I've done it here before). Same driving and weather conditions as yesterday (before the mod): bare and wet, 0 C, stiff head wind. I leave early enough that I don't have to deal with any traffic, and most of the lights are on timers, which I have memorized. I tried to drive the same as yesterday -- I always hit the same cruising speeds. Note that I do not rev very high on my short commute, and amble along at ~65 Km/h. Yesterday, I had the block heater plugged in inside the garage (ambient 9°C), and the coolant temperature started out at 22°. It still took 2.2 Km to light the first blob (40°), and it topped out at 56°. Heat from the vent was not very noticeable until about 45°C. Today I didn't have it plugged in. Leaving the garage (ambient 9°C), the coolant was up to 12° before the ScanGauge even lit up. 40° came at 1.5 Km, 60° at 4.2 Km, and it topped out at 74°C. I was somewhat surprised that it did not get up to 80. The heat output from the vent was noticeable about 30° and was hot verging on very hot by 60. I may have an airlock, but without the thermostat opening, I'm not sure; the coolant level is still at "MAX".Tomorrow I will take the car out on the highway for a test.

I did a test run under similar conditions to your 15 km commute:Ambient temperature and coolant temperature at start 4 Centigrade.Heater fan on intermediate speed. Electric heater switched on.Drove 3 km in urban area at 45 km/h max speed, then proceded along a level A road at 65 km/h in cruise mode until 3rd blob appeared.40 C after 2.8 km.60 C after 7.2 km.80 C after 17.5 km.The engine won't produce sufficient heat when going this slow, hence reason why engine does not get any quicker up to operating temperature.How did you get on when testing on the motorway? Edited February 28, 2010 by tolsen

[tolsen 630]

I suggest a standardized procedure to test the effectiveness of the restrictor plug:

A. Engine warm up.

Start from cold noting outside ambient temperature.

Run car to nearest open high way at slow speed with heater fan on full blast (ensures the engine stays cold).

Make sure 2nd blob is not indicating or park somewhere and let engine cool down until 2nd blob does no longer indicate before starting the test.

Switch heater fan to intermediate speed.

Heater lever to max and Cdi owners switch on electric heater.

Run along a level highway at constant speed of 50 mph (80.5 km/h) in 5th gear.

Note distance for 3rd blob to appear measured from appearance of 2nd blob.

B. Heater matrix air temperature.

Heater lever to max, electric heater switched off and fan to max speed.

Air to be drawn from outside - not recirculated.

Direct airflow to central grill.

Vehicle speed and gear same as specified in first test described in [A] above.

Measure air temperature out of central grill once engine is up to operating temperature with 3 blobs indicating and 5 minutes or more after switching fan to max speed.

It may be advisable to do above test a few times before and after fitting the plug.

Revised 1 March 2010. Reason: Initial procedure was unworkable. Added 5th gear.

Revised again 6 March 2010. Deleted time measurement. Added air temperature out of heater matrix.

Edited March 6, 2010 by tolsen

[Francesco 71]

The engine won't produce sufficient heat when going this slow, hence reason why engine does not get any quicker up to operating temperature.

How did you get on when testing on the motorway?

But it is impressive how the extra flow through the heater core gives a significant boost to the the cabin heater's output!

I did not have a chance for an extended romp on the motorway this afternoon (and icy roads at 3:45 am precluded any nonsense on the way to work), but I did blend into traffic at 110 Km/h for the 5 Km segment. With a tail-wind and frequent lifting due to traffic vagaries, the temperature quickly climbed to 77° before I had to slow for my exit. At the rate of climb I saw, it would have reached 80 just a few metres after my exit. Tomorrow I'll do a more thorough test.

[bilgladstone 13]

I am as motivated by the potential increase in fuel economy (greater engine efficiency) for us short-trippers as by the quicker cabin heat. Also interested in more efficient summer cooling as added bonus.

[Francesco 71]

I'm pretty sure it does help the engine get up to operating temperature quicker, but I am certain it enables my engine to get to a higher temperature on my particular commute. Whereas I never saw more than 60° on my morning drive with air temperatures at freezing, the last two days it go into the mid-70s -- almost operating temperature and definitely more efficient than mid-50s.

[tolsen 630]

Please try the revised standardized test procedure described in post 31 so we can get some data. The initial procedure turned out to be unworkable. 1st blob indicated miles before I made it to an open road and I had to let engine cool for nearly 30 minutes before I could set off. Just measuring the time and distance from 2nd to 3rd blob to indicate should be sufficient to verify the effectiveness of the restrictor plug.

It would be nice to get data from Smarts without the plug as well.

I did a test run this afternoon. Result:

Ambient temperature +4C. Speed 80 km/h along level dry open road. Negligible wind. Heater fan on intermediate speed. Heater lever to max and electric heater on.

Time and distance for 3rd blob to appear (measured from appearance of 2nd blob): 3 min 36 sec. 4.8 km.

Edited March 1, 2010 by tolsen

[Francesco 71]

I will try the revised test procedure in about 30 minutes. Most roads nearby are either 50 Km/h limit (traffic flows at between 60 and 70), or the 100 Km/h limit motorway (with traffic at 100 to 125). I know of a long-ish stretch of 50-limit service road that is not monitored by the police and I can safely (if not legally) go 80.

[tolsen 630]

I will try the revised test procedure in about 30 minutes. Most roads nearby are either 50 Km/h limit (traffic flows at between 60 and 70), or the 100 Km/h limit motorway (with traffic at 100 to 125). I know of a long-ish stretch of 50-limit service road that is not monitored by the police and I can safely (if not legally) go 80.

I did not think of such problems and restrictions. Perhaps we could change the suggested constant speed to suit Canadian conditions and highway regulations?

[Francesco 71]

Well, they vary by region. I'm in the suburbs of a major metropolis, while others may have rural highways right outside their front doors (usually 80 or 90 Km/h limits). The closest such highway I have is about 15 Km away.

[tolsen 630]

A second test run using standardized test procedure described in post 31:Ambient temperature -1C. Speed 80 km/h along level dry open road. Negligible wind. Heater fan on intermediate speed. Heater lever to max and electric heater on.Time and distance for 3rd blob to appear (measured from appearance of 2nd blob): 5 min 6 sec. 6.8 km. First test result was better but done at ambient temperature of +4C. Conditions otherwise the same but different road:Time and distance for 3rd blob to appear (measured from appearance of 2nd blob): 3 min 36 sec. 4.8 km.

[Pingu 0]

Tolsen - to ensure standardization, what gear are you using?

[tolsen 630]

Tolsen - to ensure standardization, what gear are you using?

Auto. It will be in top gear (6) since I'm riding along a level road.I wonder why there is such an increase in warm up time with only 5 C lower ambient temperature. Engine is only cooled by heater matrix and the higher coolant flow (with restrictor plug fitted) makes it possible to drain more heat out of engine. I will repeat these tests whilst running heater fan on low speed.

[Pingu 0]

My smart only shifts to 6th in auto at nearly 100 km/hr. At 80, it would be well under 2000 rpm. What rpm do you have at 80 km/hr?

[tolsen 630]

RPM at 80 km/h? Approx 1750 RPM I think. Please note that mine is a Cdi.

[Pingu 0]

Thanks. Yes, I realize this is CDI.

[tolsen 630]

Thanks. Yes, I realize this is CDI.

I shall change the standardized test procedure again and go for 5th gear. Is there anything else I have not considered?

[Francesco 71]

Well, traffic wasn't ideal on the stretch I used, so I ended up going to a little-used connector road (with AWFUL asphalt). I had to let the engine cool. Unfortunately, I had to slow once to a crawl for about 20 seconds to pass a stalled car, so my results here are probably not accurate. 5°C air temperature and no wind. Fan at intermediate, heat on full with the booster. Cruise set at 80 (GPS), and 5th gear except for dropping all the way to 1st and back up during the break (temperature dropped from 76 to 74 over those 20 seconds/200 metres). Overall, it took a 3:07 to reach 79°C, but an agonizing 1:13 more to go from 79 to 80° and the third blob to light. Distance covered was 5.3 Km.I will try this on the motorway during the wee hours of the morning on my way to work from Wednesday on, when there are very few cars and plenty of room for them to avoid me while I go 80. Weather is forecast to be dry and right around the freezing point for the next several mornings.

[Francesco 71]

Note that this "standardised" test is good for providing a wide base of empirical comparisons, especially if people can perform it a couple of times before and after installing the plug. But truth be told, my objective real-world observations of the engine temperatures (and the subjective difference in the amount of heat being blown into the cabin) along my regular route to work prove to me that this is a successful and worthwhile modification.

Edited March 1, 2010 by SameGuy

[tolsen 630]

Hi there,

I've done another test. Have compliled all standard tests carried out so far in below table. Please advise any errors.

All of mine were done in auto. Need to get that sorted soon since I ought to comply with my own test procedure.

Pancake flat roads around Banchory are as scarce as hen's teeth.

Profile of the section of the road that goes slightly uphill is like this:

The last 250 m is level and not as steep as shown. That part of the road is cut into the terrain and not picked up by the path profile feature in my electronic map software. Max height difference is 35 m.

I think we don't need to measure the time. Time can be calculated based on distance driven and speed.

Edited March 2, 2010 by tolsen

[Francesco 71]

I'll leave for work a half hour early tomorrow morning -- so, 3:20 am! -- and run at least one if not two tests, depending on how long coll-down takes. Yesterday 75 to <55° (second blob to go out) took ten minutes. I can repeat this same run several times over the next few working days (I work at the weekend).

[Francesco 71]

I am pleasantly amazed at how well this works!I just ran out to the shops for a minute. It is +3° and sunny right now, so I opened the roof to the roll-bar, put the fan on medium and heat on max (boost). By the time I left the neighbourhood and hit the main street (1.6 Km) the ScanGauge was at 40° and there was noticeable heat coming from the dash. A further 2 Km in stop-and-go to the shop and the open-top cabin was cozy warm as the coolant temperature climbed to 70!

Edited March 2, 2010 by SameGuy