MAP Sensor Pics after 37K miles with GDE Eco Tune/EHM

Mountainman · **Posted:** Tue Mar 10, 2015 2:07 am

gmctd wrote:

Good start, Mountainman - and, just FYI:
- unless you're constantly running up to 60psi BOOST (and above), a turbocharged Diesel engine does not require a blow-off valve
- if, however, you suddenly back off the APP pedal and your BOOST gage shoots up and pegs out above 30psi, you should prolly contact Rancherman for some good advice on installation and use of a BOV, as he seems fairly knowledgeable about such matters

p.s. FYI: the li'l puffer doesn't need a 60psi BOOST gage - you'll be s-t-r-e-t-c-h-i-n-g the envelope to get to 30psi, and you'll appreciate the increased resolution of the 30psi gage at low BOOST levels
- word up, eh....................

10 4 Gmctd! Thanks again for all of the advice. I really enjoy how these turbo diesels make elevation not an issue :rockon:

gmctd · **Posted:** Tue Mar 10, 2015 10:59 am

As did the pilots flying the F-51 Mustangs, F-40 Warhawks, and F-38 Lightnings in WWII............................

Auberon · **Posted:** Tue Mar 10, 2015 11:26 pm

Glend did this (added a BOV - that is is) a good while ago. Have seen no reports on its longevity but how he did it (and he did it liaising with Keith at GDE).
It CAN be illegal to open your system in your area to atmosphere especially in such an easily heard method.
It was written up here and on AusJeep.
Illegal in many places. weeks101 made a good a sort out for this that is virtually undetectable to an unknowing eye.
I expect correction somewhere.
Comment about on road operation: please bear with me. It becomes relevant.
I find this motor she is quite happy and unstressed for most running conditions. Turbo is fairly predictable in behaviour.
As an example:
On some fairly constant longer hills (about a mile or so long) where the speed limits are 70 km/hr the TC cannot go into lock-up so there is still slip @ 2400 rpm - this holds 70 km/hr on this hill - presently stock TC - boost is well held to 15-18 psi boost (as the slope varies a bit of course). and boost just drops off with sudden throttle off - yes sometimes quickly but stays in the positive side of the gauge then drifts albeit quickly back to 0 until the throttle is operated again....no erratic jumping with an instant throttle off........and EGT immediately prior to turbo rarely gets too high either.

I do have gauges fitted and running GDE ECO tune for the present.
Same comments apply on some rather bigger mountain country with switch backs - no concerning gauge bounce with throttle on-off on switch-backs or hair-pins.
When driving like this EGT's are easily kept <700F.

I seriously can't see how anyone can feel happy driving one of these w/o at least these gauges fitted.
It is really surprising how long the idle is to get back to 200 deg C after these hills and arriving home.
How much does adequate idle time after getting the EGT up a bit that have to do with premature shut-down and carbon not clearing from the engine?
It will settle somewhere. Carbon likes Carbon.

Mountainman · **Posted:** Tue Mar 10, 2015 11:37 pm

Thanks for the boost report Auberon! I guess I'll quit worrying about the switchbacks, but get a boost gauge installed asap.
I don't know much about the EGT's and carbon, but I know Keith said to WOT it every now and then to keep the cat clean, if you drive like a Grandpa especially. I like to baby mine somewhat though, only going a little over 3000 rpm's occasionally. I'm deleting the muffler soon for a little more efficiency and lower EGT's

gmctd · **Posted:** Wed Mar 11, 2015 1:19 am

Good input, Auberon

Here's the facts that back up your input

BOV = B.O.V. = Blow-off valve

All infernal combustion engines are air pumps, modified to make power by ingesting and burning fuel
- being 4-stroke air compressors they pump their rated displacement every two revolutions at standard BARO pressure
- double BARO pressure with a turbocharger = double pumped volume
- 2.8L at BARO
- 5.6L at BARO + 15psi BOOST
- 8.4L at BARO + 30psi BOOST
- etc, add fuel to suit
- interpolation rounded off and smoothed for illustrative purposes (and ease of math)

The KJ 2.8L air pump puts out 2800cc's\2rev for 840L's or 840000cc's at 600rpm idle, 3920L's or 3920000cc's at 2800rpm, 5600L at 4000rpm
- 5600L @4000rpm = 298cfm un-BOOSTED
- for comparison, 3.79L or 3790cc's = 1gal
- because the Diesel engine does not have a throttle plate, with no resulting vacuum levels in the intake manifold, it will pump out the full
displacement at any rpm, idle to WOT
- this occurs whether the throttle is applied, with resultant fuel injection and combustion, or no applied throttle, as in deceleration
- this pumped volume is always exiting thru the exhaust system, which includes the turbocharger turbine, even with no throttle application
- meaning, that at road and hiway speeds there will always be pumped air volume which will spin the turbine, as long as the torque converter
is driving the crankshaft during deceleration
- Boost cannot spike upward, but will drop to a lower level, then slowly drift down as engine rpm and pumped volume decreases
- no BOV required
- normally, in Diesel racing applications, a BOV is required to limit maximum BOOST in event of over-revving, as in miss-shifted gear, broken drive-line, etc

The spark-infested gasoline-fueled engine with it's required throttle plate pumps only some portion of rated displacement dependent on throttle plate opening
- throttle plate closed at idle, ~24" intake vacuum = minimum pumped volume
- throttle plate wide open = pumps full displacement volume
- 2800rpm, ~14psi BOOST, back out of throttle, plate slams shut, BOOST, with no instantaneous path to dissipate, slams up against closed
throttle plate, so can spike briefly prior to dropping as intake vacuum completely reduces pumped volume thru the turbocharger turbine
- throttle plate closure creates the requirement for a BOV on gasoline-fueled engines running higher than factory BOOST levels
- it is necessary to prevent damaging\breaking the turbocharger compressor and turbine wheels and shaft
- BOV will also prevent over-BOOST at over-revving event

thermorex · **Posted:** Wed Mar 11, 2015 7:20 am

Mountainman wrote:

Thanks for the boost report Auberon! I guess I'll quit worrying about the switchbacks, but get a boost gauge installed asap.
I don't know much about the EGT's and carbon, but I know Keith said to WOT it every now and then to keep the cat clean, if you drive like a Grandpa especially. I like to baby mine somewhat though, only going a little over 3000 rpm's occasionally. I'm deleting the muffler soon for a little more efficiency and lower EGT's

Make sure you put an egt too, it's not that hard as you may think, and the benefits are huge, as auberon also said. You'll know exactly when is safe to turn off engine to protect the turbo, how hard you can accelerate under load, etc. I started a thread in tech section if you're looking for some ideas, but there are obviously more out there.

Mountainman · **Posted:** Sat Mar 14, 2015 3:00 am

Thanks Gmctd and Therm as always! I won't worry about the Bov any more. Therm- I read your walk through a while back on the EGT probe, it was very helpful. I am definitely interested in knowing when it's safe to shut it down!

:rockon:

MAP Sensor Pics after 37K miles with GDE Eco Tune/EHM

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