Suggestion: No VTEC when cold via ECT

speedengineer · Post by **speedengineer** » Wed Feb 11, 2009 12:32 pm

This is a suggestion for a future version of KManager:

I live in a cold climate and have a supercharged RSX. From cold startups it often takes ~5min of driving before the ECT even reaches 140 or 150 degrees. I like to drive the car easy until it is fully warmed up - which includes avoiding VTEC. However, most of us supercharged folk have VTEC set at 3000 (and the window can't be set above 102 kPa) which means the car is a pain the the rear to drive when cold.

So, is it possible for you to add in an option for minimum ECT temp for VTEC operation on either the VTEC tab or the Protection tab in KManager? It would be absolutely awesome if you could.

speedengineer · Post by **speedengineer** » Wed Feb 11, 2009 12:39 pm

One more thing:

If this addition isn't possible or likely, what if I put a switch in between the VTS output and the valve? My question here is does KManager wait for confirmation from the VTP sensor before switching to the VTEC fuel and ignition maps? If so, then maybe this would be an alternative method...(just not as convenient)

Thanks!

Post by **Hondata** » Thu Feb 12, 2009 8:45 am

What is the problem engaging VTEC when the engine is cold? It is never a good idea to put the engine under high load or high rpm when cold, since the bearing clearances & piston/wall are tight, but the valvetrain is not affected by the engine temperature.

speedengineer · Post by **speedengineer** » Fri Feb 13, 2009 7:43 pm

I am more worried about oil pressure. When it is 10 degrees out the oil is quite cold and viscous and then you take half of what pressure your getting away to operate the VTEC. I'm not sure what the oil path is inside of the K20, so it is entirely possible that this actually isn't a problem - I just cringe every time it happens.

Obviously you know a lot more about the software and hardware than I do, but I can't imagine that such a feature would be overly difficult to add in. It's just a suggestion, so take it as you will.

Thank you

drumnatural · Post by **drumnatural** » Sun Feb 15, 2009 7:26 pm

Why can't you just sit in the car a few mins longer and let it warm up before you drive?

cranny · Post by **cranny** » Sun Feb 15, 2009 10:17 pm

Hondata wrote:What is the problem engaging VTEC when the engine is cold? It is never a good idea to put the engine under high load or high rpm when cold, since the bearing clearances & piston/wall are tight, but the valvetrain is not affected by the engine temperature.

cold contracts , heat expands , lol. clearances are looser when cold than hot. once the engine has been running for say 2 minutes , the pistons have been well heated im sure. oil warms fast as well. just cause your coolant takes longer doesnt mean the engine isnt warmer than the coolant. you wont hurt it.

Post by **Hondata** » Mon Feb 16, 2009 8:39 am

Oil pressure is actually much higher in a cold engine that a hot engine.

A little knowledge is dangerous. When the engine is cold and you place it under high load the piston heats and expands much more quickly than the iron cylinder liner, surrounded by coolant.

cranny · Post by **cranny** » Mon Feb 16, 2009 10:13 am

im curious is all , how do you figure oil pressure is higher in cold engine than hot? besides the cold idle at 1500 rpm holding it high. im sure when the engines were designed/engineered , the different expansion rate of the piston and sleeve , if any , was taken into account. all it takes is a second of the piston/wall being too tight , such as a scenario as your talking about hondata , and the thrust surfaces of the piston would be permanently damaged.

of course its not a good practise , but you can start the car dead cold and beat on it right away for the life of the engine and it wouldnt hurt it. thats a fact. can anyone guess how long honda recommends to let the car warm up before driving? seconds , lol. they say its a waste of gas to let it idle till warm , and plus , it will warm quicker under load. thats service manual info.

also to mention , the ecu has it built in to not let vtec engage till a set temp. so if your drving the car cold , and vtec is engaging , that means its safe too wouldnt you say.

fonz600 · Post by **fonz600** » Mon Feb 16, 2009 11:47 am

cranny wrote:how do you figure oil pressure is higher in cold engine than hot?

Because of the viscosity of the oil when it is cold.

cranny · Post by **cranny** » Mon Feb 16, 2009 12:19 pm

you think something is easier to pump when its thicker? it doesnt matter. i think buddys questions are answered.

speedengineer · Post by **speedengineer** » Tue Feb 17, 2009 10:30 am

I believe most oil pumps are gear pumps (positive displacement). This means that flow rate is FIXED for a given pump speed (rpm) minus a little bit of leakage flow. The pump itself does not make pressure - it makes flow, the pressure results because of the resistance to flow of the oil. When the oil is COLD, it is much more viscous and has a much higher resistance to flow, which creates more pressure.

Problem is, 'resistance to flow; is also affected by geometry and size of the passageway. Not all passageways/orifices will have the same resistance, and while I haven't done the math on it, I feel like this would cause a more dramatic effect when the oil is cold and viscous - perhaps some engine components are more likely to experience lack of oil than others??? Just throwing that last part out there.

I know that before I upgraded to KPro, the stock Honda ECU would not allow VTEC to engage until the engine warmed up. They must have done this for a reason. Also, I don't always wait for my car to warm up completely; I don't always have this time and it wastes fuel.

speedengineer · Post by **speedengineer** » Tue Feb 17, 2009 10:33 am

Hondata, any word on this? Thanks

speedengineer wrote:One more thing:

If this addition isn't possible or likely, what if I put a switch in between the VTS output and the solenoid valve? My question here is does KManager wait for confirmation from the VTP sensor before switching to the VTEC fuel and ignition maps? If so, then maybe this would be an alternative method...(just not as convenient)

Thanks!

cranny · Post by **cranny** » Tue Feb 17, 2009 11:32 am

your Kpro should also hold off vtec till the engine is warm a bit. im not sure if there is a setting for this or not , i dont think so. i know you can disable ignition retard when cold.

Post by **Hondata** » Wed Feb 18, 2009 10:04 am

speedengineer wrote:Hondata, any word on this? Thanks

speedengineer wrote:One more thing:

If this addition isn't possible or likely, what if I put a switch in between the VTS output and the solenoid valve? My question here is does KManager wait for confirmation from the VTP sensor before switching to the VTEC fuel and ignition maps? If so, then maybe this would be an alternative method...(just not as convenient)

Thanks!

Read my first post. There is no reason to stop VTEC when the engine is cold.

speedengineer · Post by **speedengineer** » Fri Feb 20, 2009 7:14 pm

Read my first post. There is no reason to stop VTEC when the engine is cold.

Understood. I don't plan on doing anything about it, at least not now since it is getting warmer out anyway.

However, (and I apologize for being so pushy), I actually am curious. I would like to know simply because I like to know stuff like that. Can you sport me a yes or no?

Thanks for your patience and help.