Automatic Coolant Temp Hack for Better MPGs

So.... this will allow me to glide on short trips, say 3 miles or less, that's all this accomplishes? I am concidering it because my wifes daily commute to work is just under 3 miles. We average about 40mpg on her work trips, but the ICE seems on the entire time. It's warm here in so cal year round. 50 is about the lowest we see here in orange county most of the time.

 

its more for plug-in prius drivers

 

well thanks anyway guys :|

 

I think it's very dangerous to think of the modification in this way. It certainly doesn't reduce emissions--once the catalytic converter warms up to speed the vehicle hardly produces anything at all. The real danger is if this could have any impact on /startup/ emissions (EG: say someone accidentally left the system enabled before the engine was warm).

Rule of thumb on the Prius: Less engine running does NOT necessarily mean less emissions. You could do a 25 mile trip entirely on EV and blow your warmup sequence under load on the last mile and your emissions would be way off the charts in comparison to if you had warmed the vehicle up properly to begin with.

If you want to legally sell this as a modification (or in good faith encourage others to use it) here are a few things you'll probably need to do:

1) Prove that the vehicle will still meet SULEV emissions standards with the system engaged all the time (since it is driver based you have to assume the worst case scenario that the system is always left on--any testing facility will require this). This requires very expensive testing at a fancy-pants powertrain laboratory (Argonne, Idaho, etc). If the modification /does/ actually increase emissions well that jolly well defeats part of the point of a hybrid--and probably does make it illegal to sell and use (agreeing with Jimbo's argument).

2) Prove that the modification does not impair any vehicle safety features (EG: what happens when the real ICE temperature goes above your spoofed temperature? Does it fail over to the real temperature? Otherwise you could be in serious trouble if you unknowingly run out of coolant due to a leak--the stock Prius will safely cause the engine to stall and go to limp-mode if it gets too hot).

3) Prove that the modification does not cause long-term engine block degradation (IE: having it tested on a vehicle for 100,000+ miles and comparing the results with a control case).

I say this a lot, but I do mean it: These are incredibly fine tuned machines. Everything is done for a reason--however trivial it may seem to us. Tinkering with one thing can unknowingly cause significant repurcusions in other areas we didn't think about (eg: the butterfly in Europe causing a hurricane in central America--or whatever that saying is). Just because it seems harmless to us doesn't mean it is harmless.

Andrew

 

Hi TheForce,

First, I meant no hostility in my responses and I apologize if they came across that way. Sometimes I say things as a matter-of-fact and they come across a bit...blunt. My purpose in posting is for the benefit of the community at large and thus not everything I say is directed at you specifically. I hope you don't take anything I say personally as it was never intended to be so.

Anyway, let me respond to what you've just raised.

First and foremost--I have nothing against tinkering. You are quite right that most things are learned and better understood /by/ tinkering and so please, do tinker. My reason for including that last paragraph was not to discourage tinkering (we are all hobbyists here afterall), but rather to encourage...prudence.

You see just because something works once in a controlled experiment does not necessarily mean it is ready for large-scale implementation (I know you understand this, again I speak to the greater community). Let's ignore the fact for the moment that it may very well be illegal to use (and the liability on that is a whole other ball-game). From what I see of the modification you are proposing, it does look like you have tried to account for as many cases as you can think of (and I applaud that effort--not everyone thinks about safety).

But it's easy to make something work once, however it's very difficult to make something work reliably under all circumstances all the time (think intense vibration, -40C temperatures to 80C temperatures, etc etc). All it takes is one circumstance that wasn't planned for to cause a failure--and with an automobile a failure /could/ become catastrophic to some inexperienced driver who might purchase said modification and install it. I know safety wasn't exactly one of the issues I brought up earlier, but I think it complements the point I was trying to make.

Selling a modification implies some form of responsibility that can't be shrugged by a simple disclaimer...I think you have to have a legally binding document that has to be signed by the purchaser to waive liability for a product you sell--I don't believe simply saying you are not responsible is sufficient to hold up in court...though again, lawyers feel free to correct me.

Second, let's talk emissions. We both threw around the 24 mile trip with one cold start concept so let me explain a bit more what I meant by that. First, I still maintain that a 24 mile EV trip ended with 1 dirty cold start is significantly (emissions-wise) worse than starting the engine twice during the trip. This is because the first time you start the gasoline engine is where timing is most critical. If you exit EV mode under load (that is, you press the pedal too hard or if you run out of electric power or generally anything involving the pedal being pressed while moving at speed) you demand power from the gasoline engine before it can enter the warmup stage (known to many as S1). This is where there are huge spikes in emissions.

If on the other hand you allow the engine to warm up properly /and then/ go to EV mode for 24 odd miles and start the engine again--the system is still warmer than it otherwise would have been (it takes hours to fully cool the catalytic converter and ICE). Granted, the cat won't be /quite/ as efficient as it otherwise would be, but it's still certainly better than coming off of a cold start.

Nobody has to believe me or take my word for it--if anyone really wants to you can access Argonne National Lab's own testing data for the Hymotion system. They start the ICE at the beginning of the cycle and warm it up, then do the majority of the drive in EV with a few ICE starts throughout the drive. It's not exactly the 24 mile trip we were discussing but it's close enough to demonstrate my point. They still meet SULEV even with the multiple starts--and I know from previous testing data they have performed that a vehicle that exits EV under load will miserably flunk the emissions test by a significant margin (an under-load EV exit pushes the car well out of SULEV criteria). Granted, the UDDS cycle is somewhat of a joke-of-a-course because it really doesn't cover real-world driving, but it's close enough for relevance to this discussion (and it's what the emissions regulation people use to test vehicles).

I know you were referring to a long drive period where the catalytic converter and the engine would cool--but just compare the overall emissions information from the coldstart UDDS cycle with the warmstart UDDS cycle. A warm cat is still better than a cold cat.

Ironically you are better off (from an emissions perspective) starting the gasoline engine twice--once to warm it up and once when you run out of battery--than you would be just starting it when you run out of battery.

Basically you could say that emissions control is somewhat of a black art even today. Even small things can impact it.

I'm not trying to start an argument here or otherwise appear hostile. I respect your (TheForce)'s contributions to the Prius community at large and have nothing against you personally. I am simply saying the facts as I know them and trying to make sure others are aware of the dangers associated with this sort of modification. Anyone is more than welcome to disagree with me or my grammar...

Andrew

 

If this is keeping the engine from reaching normal operating temperature, it might lead to oil sludge formation.

I would be wary of this with this modification, and would consider more frequent oil changes if you do this a lot, otherwise, you might need to factor the cost of a new engine into your gas savings

Normal (high) oil temperature helps to "boil off" water and contaminants that might otherwise accumulate in the oil. Water vapor is a normal product of combustion, and some of it inevitably ends up in the crankcase where it can accumulate in the oil, and help to form sludge, if not "boiled away" by warmed-up operation.

 

Howdy,

I meant to include this in my last message but I forgot. The reason it's important to start the ICE every time is because you /might/ need the gasoline engine--say you need to get out of an intersection very quickly and you end up flooring it--if you had warmed up the engine first then you wouldn't be significantly increasing emissions (and possibly damaging your engine if the block is cold).

It's more of a preventative thing--since in order to get a vehicle certified you literally have to plan for every conceivable circumstance. Also the drive cycles used to test for emissions require more power than the EV mode can provide thus the car will fail miserably if it tries to do the whole thing in EV.

Now the official Gen2 PHEV Prius has twice the power (actually more than twice the power) of the OEM Gen2 Prius EV mode (just shy of 50 kW in EV mode). This means you can get pretty good acceleration without the need for the ICE and so I believe they are able to do the entire emissions certification test in EV...I don't know if they require the ICE to warm up before going to EV mode with the OEM PHEV.

GM is a different game because their engine doesnt move the car (not directly connected to the drive-train). That means they can warm it up at their leisure while the electric motor is driving the car. Obviously if the car starts with the battery depleted they will start the gasoline engine immediately so it can provide additional power once warm.

The real important thing to consider is worst-case scenario where you end up heavily accelerating on a cold cat / engine block. That's why Toyota tries to warm up the gasoline engine every time the car starts.

I hear you about the emissions thread--though I feel like people are getting tired of hearing my rants about emissions =P.

Andrew

 

If you want to get your engine temperature up as high as possible before startup, a circulation tank heater is the way to go. There is a coolant drain on the back of the block under the exhaust manifold that can be used as the low point with the high point being the heater core inlet on the side of the head. Theses units "percolate" your coolant efficiently and quickly up to a much higher temp than the block heater ever could for about the same money and install time.

I just installed one on my transaxle coolant lines and it works very well to get it up to temp. Next project will be one for the engine block.

This plus a spoof for that last few degrees would be optimal.

Good work on the auto spoof. Can that be adapted to a 2003? If so I may be interested in one.

 

Andrew:
Your statement about emissions is correct if you have no aprori knowledge of how the car will be driven. However, I know the length of my trip, and the typical driving cycle. I know that the trip can be made without the ICE ever running. If the ICE should start, I want to shut it off ASAP because a really don't need it for my trip. Therefore, having it run pollutes more then having it not run. If you do not know your drive cycle, then of course, on average Toyota may have optimized the design. As an engineer, I know from lots of experience, you usually can improve on designs, although you frequently run into diminishing returns.

 

Hi Vertex,

My point is you cannot account for all variables. Lets say you end up in an intersection and you /must/ get out of it quickly because you're about to be hit from behind. The electric motor simply cannot provide enough power to get you out thus you need to floor it. I know this may not be an every-day thing--but it's enough of a consideration to become a problem for this style of system. There /always/ exists the possibility that you will need the full power of the ICE (or heck, even just a few more kW than the electric motor is capable of providing).

A greater possibility still exists for you to accidentally push the pedal too hard and exit EV--or if your batteries are cold, it's extremely easy to exit OEM EV mode even if you are being careful.

If the ICE turns on--even for a second or two--under load using EV mode this is when the huge emission spike occurs. The only way to for sure prevent such a spike (from stock OEM EV mode that is) is to run the gasoline engine normally when the car turns on and then go to EV mode. No matter how quick the engine turns off the damage is already done at that point.

If warmed up properly, the Prius emits extremely low amounts of emissions--you would have to warm the car up properly between 8 and 12 times to equal the amount of emissions produced by one single "dirty" start.

This really isn't a design issue as the Prius wasn't originally designed to use EV mode continuously for long periods of time (unmodified of course). It only becomes a design issue when dealing with PHEV conversion systems. So far the only conversion company that I am aware of to overcome this hurdle is Plugin Conversion Corp (Plug-In Home) by using the Hybrid Energy Manager (Ewert Energy Systems) to warmup the engine prior to using it when transitioning from EV Mode.

Anyway, I've said my two cents and hopefully it's helpful to those who are interested in lowering overall emissions.

Andrew

 

In vertex's example, an accidental start event would most likely be exactly the same as starting your car any at other time like at the beginning of a trip. I don't see how this is a relevant argument against the coolant hack.

If you do this several times in a row, sure, but a one off incident is nothing compared to all the emissions you are saving by not running the engine at all.

You can never account for all variables. Let's say you start your Prius and pull out of your driveway and a truck is careening at you. You hit the gas to avoid it and voila, emissions spike and you don't even have a hack!

I still believe this hack, used properly, would reduce overall emissions.

If that's not good enough for you could use a circulation tank heater and pre heat the engine to operating temp before your trip. Debate over.

OK not quite. You would have to preheat the cat too. Radiant heat?

 

My point is that an accidental engine start is 8 to 12 times worse than a normal engine start--this is because under an accidental start the ICE is turning on under load versus turning on NOT under load when you first turn the car on (you'll notice that it heavily favors the electric motor soon after turning on--this is to lower emissions). Demanding power from the engine without letting it warm up first /significantly/ increases emissions.

True, you could just jump in your car and floor it and it'd be about the same (slightly less, but still in the same general ballpark). This is an issue that has been raised before and yes it is a valid one but you have to pick your battles. It's far more likely that you'll accidentally step on the pedal too hard and exit EV mode (think of how many times that has happened) than it is for you to be forced to floor the pedal seconds after turning the car on...

We can agree to disagree if you'd like (and as I said before you don't have to take my word for it), but the coolant hack will NOT reduce over-all emissions. Once the car is warmed up properly the car produces hardly any measured emissions (hence the Partial-Zero Emissions rating) thus any additional engine starts beyond the first are of little overall emissions consequence. It's all about that first start--that's where the vast majority of regulated emissions come from the Prius.

The real question for this thread is does the coolant hack impact the initial warmup procedure (if it did it could potentially increase overall emissions which would be classified as tampering with emission control systems). As mentioned before, you'd have to do actual emissions testing to determine that--and that ain't cheap.

Edit: Just read the last bit you said about heating the cat--Don't heat the cat unless you really /really/ know what you're doing. Abnormal heating on the catalytic converter can reduce overall lifespan and those ain't cheap to replace...There was some discussion awhile back about an electrically heated catalytic converter system but I think they ran into lifespan issues...Also, don't try insulating the catalytic converter--it'll cook to a crisp under load...

Andrew

 

I’ve been following this thread for a while, stewing on the engineering analysis. Absent any concrete data from real-world examples, and not willing to spend the money to get the necessary emissions monitoring equipment, the best I can do is an educated guess and create a nifty chart using excel. What follows is a mathematical demonstration that the temperature hack can actually reduce emissions for certain scenarios.

I created 3 scenarios and plotted emissions per minute and total emissions over time. The units of "emissions" is somewhat fictitious and arbitrary. I believe it’s still valid since the important part of the analysis is the shape, slope and relative values from one scenario to the next.

I assumed that the initial cold-engine emission rate starts at a nice round 100 "units", and after engine warmup, the emission rate is 20 "units" per minute while the engine is operating. I also assumed my own typical driving conditions, which is a San Diego climate with 100% city driving, averaging about 35 mph between stops. My commute is typically 15 minutes, occasionally shorter or longer.

The 3 scenarios:
(1) - engine runs continuously for the first 7 minutes. In a winter morning in San Diego, that's how long it would take to get the car up to stage 4 operational temperature. But you must keep the car moving, thus not permitting the engine to stop.

(2) - "normal operation". Engine runs continuously for 2 minutes (I find this to be the typical case due to many stops at the beginning of my route), then cycles on/off between stops. As I hit stage 4, normal engine cycling continues with intentional pulse and glide.

(3) - "tricked out temperature hack" - I can only guess that the engine will run for about 1 minute continuously, then be tricked into an early stage 4 condition.

See attached charts.
Key points to observe: In the "temperature hack" graph, there are more times early on when the engine isn't running, thus the overall reduction of total emissions, although the emissions rate may be higher at any given minute.

Conclusion:
The tricked-out temperature hack results in reduced emissions for any time during the analysis, but is most dramatic between 5 and 10 minutes of driving. No matter the scenario, the true engine temperature will reach normal stage 4 operation, it just takes a little longer with the temperature hack. Thus the slope of the curves (the rate of emissions) all approach the same value as time goes on.

 

So if I'm understanding your post correctly--these are just guesses that are not based on any solid evidence at all? I think your determination should be admired, but emissions is anything but clean cut--some refer to it as a black art for good reason.

There is much more to emissions than simply how long and often the engine is on. Emissions depend heavily on exactly when the engine is actually used and the actual temperature of said engine during these times. The vehicle goes through several purge phases at different intervals depending on actual engine temperature. Fooling the sensor could cause these cycles to occur prematurely--or worse, not occur at all.

There are literally dozens of factors that play in to overall vehicle emissions thus a graph like the one you were referring to is frankly impossible to create. We mustn't think of emissions purely in terms of gasoline burned or amount of engine run-time. While these may be factors, they do not tell the whole story.

Short of actual laboratory testing ("hand-held" devices won't cut it as they are not accurate enough) there is no way to verify that it is reducing emissions--and given that there are a lot more ways to unintentionally increase emissions (significantly I might add) than there are to decrease them, I would say the burden of proof would be on proving that it somehow can decrease emissions. That requires access to a federally accredited laboratory equipped with complete emissions analysis equipment ($$$$$).

I don't intend to dampen anyone's spirits, but there is a lot at stake here--we are after all deeply concerned about our environmental footprint.

Andrew

 

hmmmmmmmmmmmmmmmmmmmm let me see now .......