No more RICH EFI in the cold! (t-stat install)

[jcm3]

Is it possible that the heat from the engine is causing the thermostat to open at a coolant temperature lower than what is expected?

[tech24]

That would have saved me some money and thanks for posting because this can be used by others in place of what I have done. I would still have the same out come however.

[tech24]

Is it possible that the heat from the engine is causing the thermostat to open at a coolant temperature lower than what is expected?

Nope I watched it work with the clear hoses on it and it opens right at 170.

[grayracer513]

So with the clear hoses on it, what have you found out about the alleged flow into the radiators with the t'stat closed?

In most cooling systems, there will be a period during warm up during which the stat opens and closes several times until the temp of the entire mass of coolant is raised some. The isolated engine running in bypass will heat up, open the stat, pull cold water from the radiator, and close the stat again. This may happen a number of times before the temperature stabilizes. Also remember that the 450 will heat up at idle very quickly, so the first "bounce of the stat is likely to happen within a minute of start up, giving you an indication that there is circulation in the radiators when that isn't quite true exactly.

The true test is if, once underway, it stays above 160 and below 260, not how it acts in limited warm up situations.

Oh, and BTW, I can read deleted posts

[tech24]

So with the clear hoses on it, what have you found out about the alleged flow into the radiators with the t'stat closed?

In most cooling systems, there will be a period during warm up during which the stat opens and closes several times until the temp of the entire mass of coolant is raised some. The isolated engine running in bypass will heat up, open the stat, pull cold water from the radiator, and close the stat again. This may happen a number of times before the temperature stabilizes. Also remember that the 450 will heat up at idle very quickly, so the first "bounce of the stat is likely to happen within a minute of start up, giving you an indication that there is circulation in the radiators when that isn't quite true exactly.

The true test is if, once underway, it stays above 160 and below 260, not how it acts in limited warm up situations.

Oh, and BTW, I can read deleted posts

What I saw was in the small outlet hose of the RH radiator, t-stat closed and I bliped the throttle I could see coolant being drawn from the RH radiator ( a significant amount.) Then I blocked of the outlet hose to the LH radiator and blipped the throttle no flow ocurred. So my thinking was it was pushing through bypass into LH radiator and backward through the RH radiator down to w/p. I may be wrong on this. I agree with what you stated but after I was finished the install my coolant temp was stabilized at around 140 so I'm thinking just enough coolant was flowing backwards to cool the coolant ever so slightly. I'll try the check valve thing and recheck.

I know you can read deleted posts that why I put a reason for deleting it. I thought you meant to type "i'm thinking, don't bother me". I read before coffee

[tech24]

BTW I looked at a coolant flow diagram for an aprilla and the system doesn't work quite the same as this. It may be possible to use but it would be difficult to plumb.

[BlackT5]

Mount it upside down.

[tech24]

Mount it upside down.

I'm not sure it would work that way. It has 2 sources of coolant flowing to it instead of one. Hot coolant from radiators on one side. Bypass coolant on the small side and both sorces exit through the fitting sticking out the side and go to w/p. I'm not sure what the internals look like but it appears to operate differently. It may be usable and I hope there is a cheaper althernative because I don't know if anyone else will want to invest the money I have so far.

[SEOINAGE]

sounds like you would have to put a y in where you mounted yours, one goes to the tstat one goes straight to the radiator, then a tube from the radiator on the other inlet, then the outlet to the pump, i havent seent he diagram, so i dunno if that is how you meant it works, but off hand thats what i think of in my head when you mention it.

[tech24]

Heres the diagram at least I assume as I'm not familiar with aprilla bikes or street bikes for that matter. Feel free to come up with a way to use it. It hurts my brain at the moment. I'd like to recommend a t-stat install on the YZs once I get mine completely straightened out without it being so expensive. Also it may be possible to use a KTM 4t t-stat as well. I'm not sure when anymore of what I got will be available soon unless I can gain enough interest for at least 10 orders.

[grayracer513]

The Aprilla setup is a input side t-stat arrangement. You see this on some Euro cars, too, but very rarely in the States. Might work better that way, but the bypass is even more important.

[Polar_Bus]

Very interesting read ! I've wondered over the years why race MX engines do not come with a thermostat system. My thoughts were too risky for the tstat sticking closed, overheating the engine, and simply more plumbing = unnecessary added weight.

I did the same type of mod to my CR125 powered shifter kart. I did the mod for 2 reasons, first being a quick engine warmup. Second is to achieve a consistant coolant temp for easier jetting consistancies. I've had my bypass mod for about 3 years with excellent results. My engine runs at approx 125F (+/- 5F, and it's monitered with the coolant sensor exiting near the cylinder head). I used a Guhl bypass stat rated at 130F . Here's a pic of my kart's bypass thermostat system:

Here's a link to my Guhl stat:

http://www.guhlmotors.com/Thermostat.html

Edited January 6, 2011 by Polar_Bus

[tech24]

Yeah I looked at them, I wish they offered a 4t temp unit. I guess 4t karts aren't that popular or something. I assume its a weight thing as to why they aren't on the bikes. But efi bikes really need them IMO.

[Polar_Bus]

Sorry if this is a bit off topic to this specific thread, but this might help gain some more understanding. There is basically 2 types of EFI systems "open loop" and "closed loop"

The term open and closed loop are terms from the automotive industry. The terms apply to the condition of the EFI system. When you start the engine and it's cold that information is sent to the ECM and until the engine warms up (70C) the O2 sensors will be ignored for adjusting the fuel delivery.(Open Loop) Once the engine warms up to "the" temperature, the O2 sensor information will be used along with the information from the throttle Position sensor and the Mass Air Flow meter to determine how long the injectors should stay open.(Close Loop)

So to say a bike is Open loop if it doesn't have O2 sensors is not "technically" correct, however I think everyone gets the idea. On the Bikes that have O2 sensors they will run Open loop until warmed up then switch over to closed loop.

If a bike doesn't have an O2 sensor set up they run fuel maps that are set in the ECM to match the different conditions the bike could be in.

If the bike has O2 Senosrs, it has fuel maps for the open loop operation and then uses the variable information from the sensors to determine injector duration when in closed loop.

Do the EFI YZ's utilize an O2 sensor ?

[tech24]

Sorry if this is a bit off topic to this specific thread, but this might help gain some more understanding. There is basically 2 types of EFI systems "open loop" and "closed loop"

The term open and closed loop are terms from the automotive industry. The terms apply to the condition of the EFI system. When you start the engine and it's cold that information is sent to the ECM and until the engine warms up (70C) the O2 sensors will be ignored for adjusting the fuel delivery.(Open Loop) Once the engine warms up to "the" temperature, the O2 sensor information will be used along with the information from the throttle Position sensor and the Mass Air Flow meter to determine how long the injectors should stay open.(Close Loop)

So to say a bike is Open loop if it doesn't have O2 sensors is not "technically" correct, however I think everyone gets the idea. On the Bikes that have O2 sensors they will run Open loop until warmed up then switch over to closed loop.

If a bike doesn't have an O2 sensor set up they run fuel maps that are set in the ECM to match the different conditions the bike could be in.

If the bike has O2 Senosrs, it has fuel maps for the open loop operation and then uses the variable information from the sensors to determine injector duration when in closed loop.

Do the EFI YZ's utilize an O2 sensor ?

Only if you get a fuel controller with the capability like the power commander 5 with auto tune. Which I still feel would benefit from the addition of a thermostat. It uses ECT, TPS, and BARO. Which becomes a problem in extreme cold when ECT only reaches about 100 degrees and the ecu is dumping tons of fuel when its not necessarily needed.

[SEOINAGE]

Sorry if this is a bit off topic to this specific thread, but this might help gain some more understanding. There is basically 2 types of EFI systems "open loop" and "closed loop"

The term open and closed loop are terms from the automotive industry. The terms apply to the condition of the EFI system. When you start the engine and it's cold that information is sent to the ECM and until the engine warms up (70C) the O2 sensors will be ignored for adjusting the fuel delivery.(Open Loop) Once the engine warms up to "the" temperature, the O2 sensor information will be used along with the information from the throttle Position sensor and the Mass Air Flow meter to determine how long the injectors should stay open.(Close Loop)

So to say a bike is Open loop if it doesn't have O2 sensors is not "technically" correct, however I think everyone gets the idea. On the Bikes that have O2 sensors they will run Open loop until warmed up then switch over to closed loop.

If a bike doesn't have an O2 sensor set up they run fuel maps that are set in the ECM to match the different conditions the bike could be in.

If the bike has O2 Senosrs, it has fuel maps for the open loop operation and then uses the variable information from the sensors to determine injector duration when in closed loop.

Do the EFI YZ's utilize an O2 sensor ?

Are you implying that if the yz doesn't have an O2 sensor, which it doesn't that I'm aware of, that it wouldn't be dumping fuel at low temperatures?

[tech24]

Are you implying that if the yz doesn't have an O2 sensor, which it doesn't that I'm aware of, that it wouldn't be dumping fuel at low temperatures?

Correct there is no real time A/F ratio correction without the addition of an A/F ratio sensor and fuel controller which will be no big deal once my coolant temp is maintained around 160 to 180 degrees. Which will be in a day or two.

[eazrider]

Wouldn't it be much more economical to move to AZ...I've had my 2010 for over a year, and never noticed it running "cold" and too rich......

?

[tech24]

Wouldn't it be much more economical to move to AZ...I've had my 2010 for over a year, and never noticed it running "cold" and too rich......

But then I wouldn't have sloppy muddy clay with frozen ground under it which is so good for traction and never makes me crash ?

[grayracer513]

Do the EFI YZ's utilize an O2 sensor ?

No. And you should understand that O₂ sensors don't respond rapidly enough to be used under racing conditions anyway, and even closed loop systems go into the open loop mode under throttle loads heavier than a certain point, or at very high engine speeds.

Are you implying that if the yz doesn't have an O2 sensor, ... that it wouldn't be dumping fuel at low temperatures?

If I understand what you are asking, I think he's implying the opposite, but there are two flaws in the logic. The first is as I just mentioned; the system would not operate as a closed loop most of the time because of the loads on the engine, and the second is that most closed loop systems won't go into closed loop operation at low temperatures. That would leave the system to fall back on its base map, adjusting fuel delivery according to coolant and intake air temperature. It would run rich either way.