delayed engine shutoff for turbo

[teigan]

i've shopped the turbo timers available, and they just don't fill my requirements. the best solution is to build my own. mine will have a thermal sensor to know exactly when the motor can kip off. i'm now sourcing the thermistor, and need some info regarding the tempurature range a hot turbo/manifold can attain. i plan to shut down once the temp is under 500 F. should i wait longer? don't want to waste petrol without cause. thanks.

[rlearp]

I don't know if that will do it. I've put the pyrometer on my turbo while idling and the thing goes off scale (limit is somewhere around 500F). Sometimes in certain areas it is in the mid 400s, so, I suppose you need to place the sensor accurately for what you want.

Ron

[teigan]

the thermistors i'm looking at are for military conditions. they come in ranges upwards of 1600 F. they are only linear within their specific range, so i need to select the best fit. i plan to mount at an existing bolt. cheers.

[lotusguy]

teigan said:

i've shopped the turbo timers available, and they just don't fill my requirements. the best solution is to build my own. mine will have a thermal sensor to know exactly when the motor can kip off. i'm now sourcing the thermistor, and need some info regarding the tempurature range a hot turbo/manifold can attain. i plan to shut down once the temp is under 500 F. should i wait longer? don't want to waste petrol without cause. thanks.

Hi,

500°F should be about the right number. Figure about 650°F+ for the oil temp surrounding the turbine bearing while the engine is running.

With a hot shutdown, the oil flow ceases allowing the oil in the bearing housing to superheat upwards of 1,200°F. This literally coooks the oil allowing it to coke, that is shed solid carbon particles from the oil which are nearly as abrasive as sand. Introducing abrasives into the bearing chamber is bad form as you may imagine, significantly shortening the life of the bearing.

Another alternative to running the engine would be to install a pre-oiler system with a relayed timer which would continue to circulate oil through the bearing to prevent heat soak of the oil for several minutes after engine shut-down by carrying the heat away from the bearing. This would add the advantage of being able to pressurize the oil system prior to engine start-up yielding twice the benefit of a traditional Turbo-Timer.

I have a system layed out, already sourcing a 12V pump (which would attach to the subframe, with sufficient flow, pressure and operating temp range), to draw oil from a qwik-connect fitting on the sump plug through aeroquip hose and return it under pressure (35-45PSI) to the oil gallery via a 'T' fitting on the pressure gauge take-off with another qwik-connect fitting. It would also facilitate easier oil changing merely by disconnecting the top fitting and energizing the system.

Being electrically challenged I have never been able to work out the components/circuitry to produce the timer. If you wanna assist in completing the system, as it appears you do not suffer from the same defficiency, contact me offlist.
Happy Motoring! ...Jim'85TE



>> Edited by lotusguy on Sunday 31st October 02:18

[teigan]

your plan sounds the optimal. is there any potential for damage should the pump fail, or pressure lost? the timer switch circuit is easy; just a 555 IC driving a relay. more concerned about failsafes. see you off list i guess.

[dr.hess]

Yeah, the electrics would be easy with a 555 timer.
Why would you want to return the oil to the gallery? Why not just pump the oil through the oil inlet on the turbo and let it come out through the oil drain back to the sump? I don't even see how you could do otherwise.
Also, you know you can just buy an Accusump type system specifically for turbo's. Plumps right in the oil inlet line and you don't have to do anything. On shut down, it pushes a oil through the turbo until it is empty. Don't remember the exact cost, but I think they are around $200.

Dr.Hess