My 1992 SC400 will break them loose and has way more power after cold soak when I first start of than when warmed. Does the engine operate in "open loop" when cold as it does at WOT?

Is there any way to keep the engine in "open loop" and could I benefit from that?

What is the best and most cost effective aftermarket ECU for a stock DD.

Thanks,

John

 

any engine is going to operate better at a lower temp. the only thing is when you first turn it on and mash on it, you arent letting the oil get to operating temp...

 

Yeah, you're destroying your engine like that..

Maybe your tires are also cold.... something to think about

 

This is just simply NOT true!

Engines are designed to operate best at an optimal temperature; too high or too low is NOT good. Once warmed up, engines will perform better with a cooler intake air charge, but that's a different issue than the temp of the engine itself.

 

emissions has a lot to do with closed loop. but if you disconnect your oxygen sensor your ecu wont be able to enter closed loop. disconnecting the maf may also work on some models.

 

https://www.clublexus.com/forums/per...mely-rich.html

You don't want to keep your car in open loop. It will wear it down faster and you mpg will suck some serious bawlz.

 

Sc,

Thank you very very much. While I don't have the ECU problem that you mention I can notice an increase in power when cold and for only a minute or so thereafter. You,and others, have confirmed the answer....open loop when cold.

The open loop condition is "normal" at cold start-up and at WOT anytime....evidently. The increase in cold power gives you an idea of what is in there if you aren't in lean burn EPA mode. As well, the open lop mix ration that is designed in is way rich at WOT so adding the piggy back unit will INCREASE MPG and power but only at WOT. Take that to the bank! It is rick cause Toy figured you must be one heck of a power condition and WOT with lean burn EPA will destroy the engine.

Now if I could get the cold open loop to run at the right mix....well, save your breath cause that is an aftermarket EMS/ECU. Now I am not a complete scoff law and I am happy with the EPA and the way my SC runs.....BUT. Some of those aftermarket ECU's have two modes....stock and POWER/MPG....and that interests me more than a little.

Thank you for your help and the really useful info. I live on a corner with a red light and a large blvd to turn into. Getting into traffic with a turn on red requires some gas pedal but I don't mean start and WOT for the tire burn. Only 1/3 pedal cause that all my SC really needs to launch and that after I drive maybe 50 yards. Being a sharp right turn the tires will howl under those conditions ONLY when cold. I don't have a problem I was just wondering if I was seeing the beni's of a brief period of open loop. Seems SC has confirmed that and I thank him again.

John

 

If you're on a budget, you can get a wideband for your air/fuel ratio and get an apexi safc. That way you can tune your WOT to whatever you want and it will always stay at those settings with the safc

 

i got a 94 sc400 wideband and apexi safc and its fun to drive around! i recommend it !!!!! then spray it