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Intake Manifold Temp on VMSpc

November 19, 2018, 05:06:41 pm

Most of the VMSpc systems I send out to folks measure Intake Manifold Temps.  These are typically just above to +20 degrees from ambient.  The turbo compresses air which increases temps and that air goes through the charge air cooler in front of the radiator and the air coming into the intake manifold is usually about +20 from ambient.

I talked to one VMSpc user (ISM11) this week whose coolant temps and transmission temps are where they should be but the Intake Manifold Temps were much higher than what I thought was typical. 

So I suggested getting the CAC and connections checked for leaks.  It is possible that the temperature sensor could be bad as well.

Any other suggestions?  Thanks.

This is another one of those things VMSpc helps with, operating parameters you don't see on the dash.

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Re: Intake Manifold Temp on VMSpc

Reply #1 – November 19, 2018, 05:12:05 pm

Dirty CAC, or sensor maybe.  Roger do you have a speed fan?

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Re: Intake Manifold Temp on VMSpc

Reply #2 – November 19, 2018, 05:17:57 pm

It is not my coach.  His coolant and transmission temperatures are consistent with what they should be so fans are operating as expected.  High intake manifold temps are after a reasonable warm up period and while driving.

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Re: Intake Manifold Temp on VMSpc

Reply #3 – November 19, 2018, 05:24:08 pm

If the sensor is bad or resistance in the wiring, I would expect temperature read out to be incorrect when the engine is cold/'before warm up as well as after the engine reaches operating temperature.  Is it?

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Re: Intake Manifold Temp on VMSpc

Reply #4 – November 19, 2018, 07:57:40 pm

A good hint Brett.  I will check.  I think the readings were OK.  I suspect a CAC leak somewhere. 

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Re: Intake Manifold Temp on VMSpc

Reply #5 – November 19, 2018, 08:33:03 pm

Will the VMSpc  read the intake manifold Temperature on a  Detroit 6V92 TA - 1994 vintage?  If so what PID should it view? 

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Re: Intake Manifold Temp on VMSpc

Reply #6 – November 19, 2018, 09:18:28 pm

It doesn't on mine 1993.

I was looking for an egt, too, but didn't find one.

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Re: Intake Manifold Temp on VMSpc

Reply #7 – November 19, 2018, 09:19:43 pm

The coach Roger is referring to is our 2005 which we have owned for the past 4 years.  Several months ago I took advantage of the ASUS Transformer Book/VMSpc package Roger offers.  My only regret is not having done it much sooner.  The simplicity when it comes to installing and the technical support provided makes for a very user friendly package.

As Roger mentioned the intake Mfold temp is running well above ambient +20 temp.  VMSpc is reporting consistently between 140 and 170 degrees.  Since installing the system I have driven in temperatures from 55 to 95 degrees.  When decelerating is the only time I see around 140 .  Depending upon ambient temp the Mfold  temp runs between 150 and 170 around 1400 RPM.  Because I waited so long to have VMSpc I don't know how long this has been going on.  With all the info I now have available tells me it was money well spent. 

I'm not absolutely sure what the Mfold temp is reading when I first start the engine.  I'll be going to the coach in the next couple of days to find out. 

Gary

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Re: Intake Manifold Temp on VMSpc

Reply #8 – November 19, 2018, 11:04:44 pm

Gary,
What is max boost (higher RPM, throttle on the floor)?

If, as suggest a CAC leak in involved, low boost and low power rather than high intake temperature would be the primary symptom.

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Re: Intake Manifold Temp on VMSpc

Reply #9 – November 20, 2018, 12:18:57 am

First I would check to make sure the CAC is not clogged with dirt. 
This could explain higher than normal temperatures.  But what's normal?

I'm not sure the 20+ ambient rule really applies here.  The new diesel models will have higher boost pressures with higher horsepower.  The higher boost means higher temperatures (exiting the turbo as high as 400 F).  The Charge Air Cooler (CAC) will be sized larger too but more variations should be expected in the temperature depending on how the engine cooling systems are set up by the OEM.  For example the combined radiator and CAC package can make for a condition where the CAC needs cooling but the fans are controlled by the engine water jacket temperature which might be lower than the set point for running the fans; thus giving you a higher inlet air temperature (although this is usually a temporary condition).  The newest engines will take both CAC and jacket water temperature in consideration for running the fans but in earlier years this was not always done.  From my understanding of the newest Cummins engines, the air inlet temperature sensor is primarily used to de-rate the engine in the event it exceeds a certain limit and thus prevents engine damage.  To know for sure one would need to look at the Cummins spec sheet for this particular engine build.  It should list a maximum inlet air temperature.  If the OEM does their job, a de-rate conditions should really only happen at extreme ambient heat conditions with a certain % of air blockage (due to dirt, etc.) on the CAC.  That % is determined by the OEM and really just means how much the CAC is oversized for that application. 
OK, probably too much detail: just make sure the CAC is clean!

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Re: Intake Manifold Temp on VMSpc

Reply #10 – November 20, 2018, 09:00:41 am

That is the reason that fan controller are LOW-HIGH, not ON-OFF.  Even at coolant temperatures that do not require a fan, the CAC does.

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Re: Intake Manifold Temp on VMSpc

Reply #11 – November 20, 2018, 09:35:48 am

Had coach that had off/low and high fan speeds. When I put VMSpc on it, realized intake manifold temps were running way to high. [Detroit Diesel recommends 30 degrees above ambient max] Temps were fine when engine cooling water temps turned fans on, but other times, especially before engine reached 180 f.+ water temps, intake temps were at 150 f.. It does take some hp to run fans even at low speed but as mentioned, engine might derate anyway, if ecm sees manifold temps too high. I did adjust fan controller so that it was on low all the time, and this solved the problem.

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Re: Intake Manifold Temp on VMSpc

Reply #12 – November 20, 2018, 05:02:57 pm

Here's an interesting data point.  When I started today, I was watching the Inlet manifold temp more than usual.  It started at about 130-140 and stayed there until the engine warmed up to about 170-180.  Then it dropped to 75-80.  Ambient temp was 55.

Is there a manifold heater that helps with cold starts?

Rich

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Re: Intake Manifold Temp on VMSpc

Reply #13 – November 20, 2018, 05:09:59 pm

Yes, you have an intake manifold heater.  But it should be off within a few minutes at most.  Probably able to tell by watching the dash voltmeter, as it draws a LOT of amps.

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Re: Intake Manifold Temp on VMSpc

Reply #14 – November 20, 2018, 06:15:59 pm

Rich, you should look to see if the fans are turning after you start and before you reach operating temp.  They should be blowing cool air on low speed until your coolant temps come up.  If they come on late, only when you are up to temp then they aren't helping cool the air through the charge air cooler.

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Re: Intake Manifold Temp on VMSpc

Reply #15 – November 20, 2018, 10:02:48 pm

When our dash displays "wait to start", our intake manifold electric grid heater is on. It goes off based on thermostat switch, and while it is on it looks like some diesel fuel is directly injected into intake manifold. Our intake heater control mechanism is on the back engine wall with some heavy cables. We don't know our intake temp, so can't comment on temps.

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Re: Intake Manifold Temp on VMSpc

Reply #16 – November 20, 2018, 10:37:40 pm

Just looked close at mine today on US70 west in NM, from 3000' to 7000'. At cruise 10-15 degrees above outside air. Hard pull 20-25 degrees +or- above outside air.

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