Reply
Visitor

Re: 3126 420HP Boost Pressure and EGT

Good morning,

 

I know this thread is very old, but I have a similar motor (new to me) and I want to install an EGT sensor.  Serial no. is 8NM03765.  Could you tell me which EGT sensor you used and where to get it?

 

Thanks,

Ben

Contributor

Re: 3126 420HP Boost Pressure and EGT

Hi everyone.

I´ve been going around these numbers to try to interpret them. Apart from the tendency to both increase with rpm, the manifold and stack temp have very little relation.

The stack temp has a minimum (703 F) at 2600 rpm but I don´t think it has any relation whatsoever with engine load and probably there must be other factors affecting this behavior(both my engines have similar behavior). On the other hand, the exhaust manifold temp is the one that really matters and it keeps rising with rpm.

How can I know, using the cat data, which rpm/mfld temp is the one to determine the cruise rpm for the 420 hp 3126 engine?

 

 

Marcos

Contributor

Re: 3126 420HP Boost Pressure and EGT

Hi SeaSalt. Nice to know that your gauges are working fine and showing you valuable info.

By the way where did you install the thermocouple? Just after the turbo there is a small plug where it can be installed it even though the thread is much smaller than the one that came with the thermocouple.

Contributor

Re: 3126 420HP Boost Pressure and EGT

I've now had my EGT and boost guages for a few months.  The charts above show the EGTs dip down around 2400 RPMs.  Both of my motors also follow that same curve.  

 

In the past, I've always run my motors at 2275-2325 RPM cruise.   Mostly, because I thought I was doing the motors a favor and loading them less.

 

Since having the EGT and Boost Guages installed, I now run my motors at 2350-2425 (2375 nominal) Cruise RPMs.  My new cruise RPM is more in line with what CAT specifies.   Also, now that I can 'See' that the motors are running cooler EGTs, I feel very comfortable running them there.   I also believe I that I am loading them less.

 

Any thoughts?

 

 

Contributor

Re: 3126 420HP Boost Pressure and EGT

thanks again Dave....

Super Contributor

Re: 3126 420HP Boost Pressure and EGT

 

ENGINE SPEED RPM

ENGINE POWER BHP

FUEL RATE GPH

INTAKE MFLD P IN-HG

EXH MFLD TEMP DEG F

EXH STACK TEMP DEG F

2,800

350

17.96

55.61

1,063.40

761

2,600

280

13.95

47.23

910.22

650.66

2,400

220

10.83

38.14

807.26

591.98

2,200

170

8.35

26.77

760.28

589.1

2,100

148

7.29

21.29

750.38

595.58

2,000

128

6.34

16.38

732.02

590.54

1,800

93

4.73

8.68

678.38

557.24

1,600

65

3.51

4.12

604.76

501.26

1,400

44

2.54

1.6

522.68

436.82

1,200

27

1.72

0.24

446

373.64

1,120

22

1.43

0.77

418.82

350.78

 

 

The 2300 RPM data for the 385HP engine is not available, similar to the 350HP data.

Boost and EGT are not really that helpful in determining most efficient RPM, as there are variables that affect both values.

Make sure the engine will achieve rated RPM + 1-3% (2830-2880 RPM) and cruise at 2400 RPM or less.

Contributor

Re: 3126 420HP Boost Pressure and EGT

FM....Smiley Very Happy

 

Acutally, I brut forced the numbers into an excel file, then I copied the data to the clipboard and then I pasted it here using the little icon on top of the reply box that offers to 'paste from word'

 

Dave:

 

Thanks for all the data....were you able to find the data at 2300 RPM for the 385HP motor?

 

Also, once again, on the 420HP motor, the same phenomon where the exh stack temps come down around 2400 RPM....that's quite odd.  Could it be that the motors are actually 'happier' up in that RPM range?

 

Anyway, here's the chart for the 420 HP motor.....Oh, and Dave, if it's not too much trouble, and since we are on the subject, can you post the numbers for the 350 HP motor.    I have a buddy with those motors and now he wants to put in a boost and pyro guage also.

 

Thanks again and we all appreciate your time.

 

 

Prop demand data for 420HP 3126            
RPM BHPFuel Rate GPH Intake Mfld P     In-HgExh Mfld Temp Deg F Exh Stack Temp Deg F
2,80042022.5668.851136.66782.24
2,70037719.5560.141065.20738.50
2,60033617.0451.351003.64703.76
2,50029915.0041.70980.24712.04
2,40026413.1632.43961.34721.94
2,30023311.5426.89932.90711.68
2,20020410.0621.91900.86698.72
2,1001778.8017.23884.66693.86
2,0001537.6313.36858.74677.66
1,9001326.6310.19827.24654.26
1,8001125.717.31784.22620.24
1,700944.895.15729.14577.22
1,600784.153.58671.36533.66
1,500653.492.55616.82491.18
1,400522.911.51559.94450.32
1,300422.400.92511.52409.46

 

 

 

Super Contributor

Re: 3126 420HP Boost Pressure and EGT

Well, that didn't work. Seasalt, how did you get the formatting correct?
Super Contributor

Re: 3126 420HP Boost Pressure and EGT

Here's the 420HP data. Let's see if I can get the formatting to stay this time. ENGINE SPEED RPM ENGINE POWER BHP FUEL RATE GPH INTAKE MFLD P IN-HG EXH MFLD TEMP DEG F EXH STACK TEMP DEG F 2,800 420 22.56 68.85 1,136.66 782.24 2,700 377 19.55 60.14 1,065.20 738.5 2,600 336 17.04 51.35 1,003.64 703.76 2,500 299 15 41.7 980.24 712.04 2,400 264 13.16 32.43 961.34 721.94 2,300 233 11.54 26.89 932.9 711.68 2,200 204 10.06 21.91 900.86 698.72 2,100 177 8.8 17.23 884.66 693.86 2,000 153 7.63 13.36 858.74 677.66 1,900 132 6.63 10.19 827.24 654.26 1,800 112 5.71 7.31 784.22 620.24 1,700 94 4.89 5.15 729.14 577.22 1,600 78 4.15 3.58 671.36 533.66 1,500 65 3.49 2.55 616.82 491.18 1,400 52 2.91 1.51 559.94 450.32 1,300 42 2.4 0.92 511.52 409.46
Contributor

Re: 3126 420HP Boost Pressure and EGT

Prop demand data for 385HP 3126            
RPM BHPFuel Rate GPH Intake Mfld P     In-HgExh Mfld Temp Deg F Exh Stack Temp Deg F
2,80038519.4759.971041.62703.58
2,60030814.9847.50913.10639.62
2,52028113.5841.90887.72636.62
2,40024211.7333.55863.78640.76
2,300     
2,2001879.1121.56840.38650.30
2,1001628.0016.73824.36647.60
2,0001407.0312.73806.18638.06
1,8001025.316.96738.50585.50
1,680834.414.62685.76541.04
1,600723.883.41645.44510.08
1,400482.770.92550.76433.58
1,200301.900.36454.10360.32
1,120251.610.47417.92331.70

 

 

Dave:

 

Thank you very much for the reply.   Hopefull this displays in a more user friendly readable format.   

 

I find it very interesting that the stack temps come down between 2200 and 2400 RPMs but the Exh Mfld temps continue to rise in the same RPM range.

 

Also, if possible, since I spend most of my cruise time in the 2300 RPM range, could you provide the numbers for that RPM range?

 

Thanks again in advance..