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2.7 Turbo 4 Fan Club


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32 minutes ago, customboss said:

PS saw 26.2 mpg @60 for 42 miles to Alamosa VA,   return 24.4 mpg @60 for 42 miles. 

 

Give it to my wife. She will cut that in half. 

😬

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Roush produced paper that even mentions our L3B.   Why this engine needs to be driven like a diesel. Focus on using that low RPM  HIGH TQ effect.  See attached PDF from EPA produced by ROUSH. 

 

Still digesting paper but thinking I MIGHT be safe on lower octane than 87 and still get performance and efficiency I want and burn clean.  

 

  • "Pressure drop across the intake valves: larger bore-to-stroke ratios enable increased valve sizes resulting in high curtain area (area of flow) resulting in low pressure drop across the valves and high volumetric efficiency. The volumetric efficiency of a low bore to stroke ratio engine decreases at high RPM resulting in torque and power that falls off earlier in the engine speed range. Manufacturers share engines across product lines to keep unit costs low and the “low RPM nature” of a low bore to stroke engine may be suitable for one vehicle but not for another. For example, the 2.7-liter 4-cylinder L3B engine is shared by the Chevy Silverado, a pickup truck, and the Cadillac CT4-V, a high-performance sedan. Having a very low bore-to-stroke ratio would make the engine unsuitable for a performance sedan. The same is true for the small-block engine architecture from GM that is shared by pickup trucks, SUVs, and the corvette."

EPA-HQ-OAR-2021-0208-0210_attachment_2.pdf

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Fuel mileage topics are always suspect. Just got home from my usual trip to the father in law. 2700 miles total at 29.9 mpg in a CRV a low it’s usually around 32 mpg. The difference wind and 74 mph instead of 72. For 2 days at 26 mpg windy as hell going east. Coming back 31.6 all at 74 mph. The only vehicles I pass are the few tractor trailers. Cops all over stopping no one. The rule used to be a 10 per cent cushion. I 95 is awful 80-85 mph almost bumper to bumper. I never in a million years thought I say it. It’s out of control. It needs to be 65 mph and tickets at 72 mph. And big fines. I don’t mind the speed. People just don’t stay to the right. And don’t pay attention. I’m thinking next trip getting out maps and two lanes around cities where it’s the worst. I did that coming back before Atlanta. Adding 20 minutes and peace. Oops off subject and rambling. Adios.

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Posted (edited)
1 hour ago, customboss said:

Having a very low bore-to-stroke ratio would make the engine unsuitable for a performance sedan.

 

:rolleyes:

 

Really

 

(from the PDF)

• Mean piston speed: longer stroke increases the average piston speed and limits the maximum rpm of the engine.

🥴

Word play. The limit is piston speed not rpm and yes rpm varies with b/s ratio. This matters how when these things are geared to run in the bottom 1/10 of the band? 

 

Engineers stating the obvious with long sentences and big words to say nothing useful. Nice graphics however. Guys got' a eat, right? :) 

 

Crap gets mind numbing after awhile. Curtain area thus mean velocity can also be controlled with valve seat angle altering the frustum area and cheaper. Something known for over 100 years.  How early motors got large volumes from low lifts. 

 

The 2.7 T motor in this truck would make a KILLER street motor in a Malibu. 

 

 

Edited by Grumpy Bear
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Posted (edited)
2 hours ago, Grumpy Bear said:

 

:rolleyes:

 

Really

 

(from the PDF)

• Mean piston speed: longer stroke increases the average piston speed and limits the maximum rpm of the engine.

🥴

Word play. The limit is piston speed not rpm and yes rpm varies with b/s ratio. This matters how when these things are geared to run in the bottom 1/10 of the band? 

 

Engineers stating the obvious with long sentences and big words to say nothing useful. Nice graphics however. Guys got' a eat, right? :) 

 

Crap gets mind numbing after awhile. Curtain area thus mean velocity can also be controlled with valve seat angle altering the frustum area and cheaper. Something known for over 100 years.  How early motors got large volumes from low lifts. 

 

The 2.7 T motor in this truck would make a KILLER street motor in a Malibu. 

 

 

OK Boomer,  🤓

 

I haven't read the article in full yet but flame front travel with modern DI engines is probably more of an issue that you mentioned. 

 

No one is worried with modern metallurgy breaking pistons or rods in street engines. 

 

Curtain area altering the frustum " portion of a cone or pyramid which remains after its upper part has been cut off by a plane parallel to its base, or which is intercepted between two such planes"  so that in a modern engine just whacking off valve seat angle  or even piston dome is not enough.

 

Well  maybe planing a  flathead  engine and doing a valve job isn't gonna work on a grossly NOx making timing advanced DI VVT OHV turbo engine.   Oh and run on 85-87 octane fuels. 

 

The 2.7L Turbo L3B is awesome in this giant of a truck. 

 

 

             

 

 

 

 

Edited by customboss
add octane benefit
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Posted (edited)
5 hours ago, customboss said:

Onboard dynamic scanning yesterday, 50F -80 F ambient temps, 60 mph. 

 

 

STFT working to bring LTFT near 0 once warmed. 

LTFT settled at +2.4%  from cold 6.2% 

 

Timing on 85 octane  operating MSL was 7800-9400'  47 o advance max, WOT and some other harder acceleration saw -2 o or -3 o  max, does drop to 0 o closed throttle to slow and engine brake. 

 

I have no way to read boost but supposedly this L3B can produce 22 PSI. 

 

For you tech gurus is any of that gonna detonate this L3B on me?  

BUMP Any of you chevy genius's have an idea of what the L3B dynamic timing range I shared means and are they normal? Too much timing retarding? Too much pulling timing as is known on the this site?  r-e-t-a-r-d is blocked here....wow. 

 

I am learning this engine.  I don't know but it sure runs good on 85 octane for a turbo'd 4 popper. 

 

 

 

 

5 hours ago, customboss said:

 

 

 

 

 

Edited by customboss
****** being blocked
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Can your scan tool read a channel called knock re tard?

 

That is how I monitor timing with HP Tuners. I log both the timing advance and the knock channel. The V8 trucks can range from similar values, cruise timing in the 40's and jumping up to 50-60 degrees off throttle coasting. I watch both those channels because I will be able to see the actual timing and the timing the knock is taking away.

 

So if the timing shows 15 degrees but the knock shows 5 degrees that means it was asking for around 20 degrees of timing to begin with. I could go back into my calibration file and look at the rpm and cylinder airmass value to see if indeed I was commanding 20 degrees just to make sure.

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1 minute ago, CamGTP said:

Can your scan tool read a channel called knock re tard?

 

That is how I monitor timing with HP Tuners. I log both the timing advance and the knock channel. The V8 trucks can range from similar values, cruise timing in the 40's and jumping up to 50-60 degrees off throttle coasting. I watch both those channels because I will be able to see the actual timing and the timing the knock is taking away.

 

So if the timing shows 15 degrees but the knock shows 5 degrees that means it was asking for around 20 degrees of timing to begin with. I could go back into my calibration file and look at the rpm and cylinder airmass value to see if indeed I was commanding 20 degrees just to make sure.

Sadly no. I watch the raw timing. It’s a 2007 version scanner. 
What you describe is what we used for GM Oldsmobile road racing but it was GMs not ours. 

My service manager is a racer and might help me with it but they won’t allow me to drive with that I bet. 
Thanks Cam!!!

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51 minutes ago, customboss said:

I haven't read the article in full yet but flame front travel with modern DI engines is probably more of an issue that you mentioned. 

 

Lean burn slower. Turbulent faster. Yep. I've played that in 50/60's motors to reap 25+ mpg for factory tunes that got less than 15. And on richer jetting. 

 

30 degree seats were not uncommon in OHV motors. Kids these days. 44/45 has become a default angle. Pro Stock motors run something in the neighborhood of 60-65. Multivalve VVT/VVL...everything plays. 

 

 Kids these days. Nothing new under the sun....

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More direct observations from dynamic scanning ( note I have no way to data log nor do I care at this point). 

 

Experimenting still with 85 octane, 87 via mixing, and 91.  Notable delta in timing retarding with 87 and more so with 91 vs more with 85 but not excessive.  However it really depends on load and which of the 3 phases of mechanical cam setting.  Low lift, high lift, AFM.  

 

AFM is really interesting and neutralizes overall timing to near 0.  On two cylinders when AFM is engaged the RPM can be about 1500 at 65 MPH or 1750 or so at 60 mph.  

 

Using 88- 91 octane fuels allows the lower RPM AFM operation at lower speeds. With 87- 85 octane the RPM has to come up to maintain AFM # 2 and #3 cylinders deactivation but MPG is about the same.  This engine is a marvel really.  Lord help me if the 3 valve coolant switch ever sticks because cooling is really critical. 

 

On cold start coolant temps via scanner hit 165-175 nearly instantaneously.  It takes a few minutes at lower RPM to read 201 degrees which is about normal operating temp fully warmed.  Gauge cluster shows 210 F. 

 

MPG readings are unusually stable regardless of fuel octane used.  I am seeing operating temps from 45F in the mountains to 80F in the valley.  

 

Winds are very high and blustery here so I pay attention to them and their effect. The New Mexico wildfires are literally 70-80 miles south of us right now so its a very unstable test environment. 

 

26.2 mpg with mixed 60-65 mph cruise speeds on highway is consistent with 91 octane fuels. 26.2 kept showing on 40 mile legs regardless of wind azimuth,  downhill or uphill in lower velocity winds.

 

25 with 87 octane

 

24 with 85 octane 

 

I did change out stock HD AC OEM air filter about 500 miles ago and MAF is free flowing to turbo. 27lbs/min at WOT test.  Cruises at 3-4 lbs/in flow at speeds mentioned above.

 

I THINK from what I am reading the HO version will REQUIRE 91 octane or at least some dealers are claiming that from what I see in internet. 

 

Will follow up with BlackO2Silverado oil analysis from to verify scanner and MPG observations, overall very happy with performance and value to date which is approaching 9000 miles on ODO.  

 

 

 

 

 

 

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MPG with 2.7 Turbo: Towing my 14 foot 3300 lb. camper trailer last week. Averaged 11 MPG over flat lands of Kansas. Average speed was 60. 310 miles

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4 hours ago, David Bodine said:

MPG with 2.7 Turbo: Towing my 14 foot 3300 lb. camper trailer last week. Averaged 11 MPG over flat lands of Kansas. Average speed was 60. 310 miles

Hi David, towing 3300 lbs should reduce your average MPG unloaded by ~ 15-25%. 

 

So the question is what is your overall average MPG unloaded?  When I am off road here in the Trail Boss in 4WD in rough Terrain I might get 11 or so but average 14-17 MPG so far. 

 

On highway I am seeing wonderful MPG.  22 would be a good reference for average and our winds are horrendous since owning this baby.  

 

 

 

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1 hour ago, customboss said:

Hi David, towing 3300 lbs should reduce your average MPG unloaded by ~ 15-25%. 

 

So the question is what is your overall average MPG unloaded?  When I am off road here in the Trail Boss in 4WD in rough Terrain I might get 11 or so but average 14-17 MPG so far. 

 

On highway I am seeing wonderful MPG.  22 would be a good reference for average and our winds are horrendous since owning this baby.  

 

 

 

 

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Ok, well 20% of my usual 20.1mpg is 4 = 16 should be the mpg after towing my 3300 lbs. trailer. But is it was 11mpg. That is the Kansa trip. Last month my trip to Arkansa yielded 10mpg. I am going to have to accept that the 2.7 gets very poor gas mileage. 

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Just now, David Bodine said:

Ok, well 20% of my usual 20.1mpg is 4 = 16 should be the mpg after towing my 3300 lbs. trailer. But is it was 11mpg. That is the Kansa trip. Last month my trip to Arkansa yielded 10mpg. I am going to have to accept that the 2.7 gets very poor gas mileage. 

If you are in boost at levels higher than normal it's gonna burn more fuel.  I bet we can find some help here. 

What are your tires pressures cold? 

What's your normal RPM @ 60 mph towing no wind? 

How many miles on the truck now? 

Have you changed the factory air filter yet? 

What octane fuel are you running while towing?  What brand of fuels are common in use? 

You are in 2WD right?  Not Auto? 

Do you use tow mode? Have you experimented with tow mode vs normal mode on level ground. 

For living in or around Branson, MO  20 MPG unloaded  is 2 mpg less than me in Mountains. 

My unit has almost 9000 miles on it and I changed air filter early with a O'Reilly MGA 10941 that gives me some improved air flow for that turbo vs the HD AC Delco factory air filter. 

 

 

 

 

 

 

 

 

 

 

 

 

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