# GM LFX V6

Discussion in 'General Auto Conversion Discussion' started by pfarber, Apr 26, 2019.

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1. May 11, 2019

### BJC

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Why?

BJC

2. May 11, 2019

### pfarber

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I don't consider a long TBO as a benefit. I'd rebuild every 5-10 years simply because it would be so cheap.

Better fuel burn
Better performance
Cheaper parts (of the same or higher quality.. OEM parts only)
Much lower initial cost (unless you purchase a FWF package, the you lose almost every benefit of an auto conversion)

The FAA is most of the problem. Adding electronic ignition should not require an STC for every model. Having to pay $300+ for a paper STC to run mogas? really? I'm happy there is an E-AB catagory, but honestly, I have seen very few 'advancements' from the E-AB side migrate over to the certified side. 3. May 11, 2019 ### pictsidhe ### pictsidhe #### Well-Known Member Joined: Jul 15, 2014 Messages: 6,461 Likes Received: 1,675 Location: North Carolina If you don't want to re-engineer anything, you need to abandon any idea of putting a car engine in an aeroplane. If you do decide to plow ahead, I also think the LV3 is a better choice than the LFX. There are people who will do the work for you in exchange for pictures of dead presidents. You should listen to the people who have installed car engines in aircraft. Ross converts engines for a living, ignoring his free advice is in a word, stupid. As for deleting the VVT, that is very commonly done by hot-rodders. The less bits you need to tune, the easier (and cheaper) it will be to set up. http://lmgtfy.com/?q=lt+vvt+delete+kit 4. May 12, 2019 ### pfarber ### pfarber #### Well-Known Member Joined: Feb 21, 2019 Messages: 196 Likes Received: 9 Location: Pennsylvania I agree that the LV3 is a better candidate and considering I can take off the balance countershaft and save another 15-20 lbs thats even more icing on the cake. There really is no changes to be made to the fundimental car engine. Sure, remove some parts and save as much weight as possible but deleting VVT is dead simple on some motors, and more difficult on others. I guess in the evolution of the my selection criteria I would have to weigh the few ounces saved in deleting VVT might save vs the effort to actually delete it. On the LV3, being a single cam engine, I would still rather keep it and its benefits. No, VVT is not needed, but if it gets me a few HP at the cost of a VVT solenoids weight I can always lock it out via the ECU or simply use it. One stark truth of the V6 engines is that there are very, very few performance mods for it. I still can't even find a mild performance cam for it. 5. May 12, 2019 ### rv7charlie ### rv7charlie #### Well-Known Member Joined: Nov 17, 2014 Messages: 389 Likes Received: 149 Location: Jackson To quote an ancient map, One stark truth of the V6 engines is that there are very, very few performance mods for it. I still can't even find a mild performance cam for it. "Here there be dragons." Shortest route to a failed conversion is an attempt to get more than stock rated power when converting to a/c use. Running in an a/c is not the same as a 5 second dyno blip. pictsidhe likes this. 6. May 12, 2019 ### pfarber ### pfarber #### Well-Known Member Joined: Feb 21, 2019 Messages: 196 Likes Received: 9 Location: Pennsylvania This is an old wives tale. The stock cam is there for a few reasons: emissions and vacuum for brakes. Higher perf cams (or even just selecting a cam that moves the power band to where you want it) will not destroy a motor unless you go hog wild or ask the basic design to do things it was never intended. But I will gladly sacrifice some idle quality (I don't need vacuum for things like brakes) to move the power band down a few 100RPM. I am not looking for double springs and .500+lift and lobes that resemble triangles. If that's what you think then you are 100000% incorrect. I would like things like roller rockers (the LV3 already has roller lifters) and since its not an interference engine maybe a slightly taller rocker ratio for more valve lift. Since the LV3 is a baby LS1/2/3/4 maybe some of those parts will interchange.. maybe not... but right now the LV3 aftermarket parts are sparse at best. I like the idea of an electric water pump (Ask any certified engine owner if they would pay$400 for 15 more hp.. the answer is YES).

IF you read the LV3 specs you'll see this:

• Vacuum Pump: The 4.3L, 5.3L and 6.2L truck engines feature a mechanical vacuum pump to enhance braking performance. It is an engine-driven pump.
This already tells me that the cam is pretty aggressive as there is not enough vacuum provided by the engine to operate the brakes at low RPM, so maybe the cam is already as good as it will get'.

7. May 12, 2019

### pictsidhe

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The LV3 is 3/4 of an LT, not an LS

8. May 12, 2019

### Himat

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The stock cam does have a profile that also takes vacuum to the brakes in consideration?
No vacuum there. Actually, I thought that with modern ABS brakes there are either a separate vacuum pump or hydraulic pump for the brakes. On all cars. At least back in the 1990’is one failure mode on some car ABS units were worn out brushes on the electric motor providing hydraulic pressure.

Last edited: May 12, 2019
9. May 12, 2019

### Voidhawk9

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Where is the power to drive the electric water pump coming from?

10. May 12, 2019

### pfarber

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Simple typo.

Its a NET GAIN. Yes the alt will need 1-2 more hp to make the additional power, but the removal of a significant load like a water pump GAINS you 8hp overall.

https://www.hotrod.com/articles/hrdp-1201-baseline-testing-do-water-pumps-suck-power/

When we swapped to the GMB water pump, using the March underdrive pulleys, we recorded an average of 523.1 hp and 470.9 lb-ft of torque, 8.1 hp less than the Meziere electric pump and 4.4 hp less than the Weiand mechanical pump.

It seems that by using an electric water pump and removing the balance shaft you free up almost 20hp and reduce the engine weight 15-25lbs. All for \$400.

11. May 13, 2019

### pictsidhe

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Almost every diesel car I've seen had a vacuum pump. The only exceptions were Citroens that used hydraulic boosting from the suspension system. Their hydraulic petrol cars used that too, despite using the same engines that ran vacuum brakes in Peugeots and other cars.

12. May 13, 2019

### pictsidhe

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So, the with the electric water pump and no alternator, it put out 0.4hp more than with the best mechanical water pump.
Adding the alternator to a mechanical pumped engine resulted in a drop of 8hp. But that wasn't even driving the electric pump, so we can expect a much larger power loss if it was. You yourself are estimating 1-2hp. How is the electric pump going to be better under continuous use?

Why don't you test the claims?
Set up your engine with a club prop. Try it with a mechanical water pump and a normal alternator. Then try it with a magical electric water pump and a 120A larger alternator.
Then pull the balance shaft.
I'd put money on you being very dissappointed with the RPM and power gains...
Shafts don't take 15hp to spin, unless you are including inertial effects, such as a flywheel dyno would...
I found a paper yesterday for the design of a balance shaft for a 4 cylinder car diesel engine. It used less than 1/3hp.

13. May 13, 2019

### wsimpso1

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Lot's of stuff on this thread.

First thing is direct drive. Putting the prop on the end of the crankshaft might be OK, might not. Gyroscopic moment from the prop Inertia times engine rotation times combined yaw and pitch rotation rate possible in the airplane has to be within the capability of the crankshaft end. Check this one out carefully keeping mind your expected flight combinations including inadvertent spins, the crankshaft materials, and crankshaft design. If the gyroscopics are too high for the crank, then you must put a floating prop shaft on its own set of bearings that connects to the crank. This weighs something, yeah lighter than the PSRU, but heavier than nothing...

Omitting the balance shaft is 15-20 pounds? Sounds high, but maybe. Power use? Pretty small. The loads are easily estimated, then the bearing torques and then power. But as someone who is trying not to do things that require development, it seems wrong to do it. Not just because it requires tear down, blocking oil passages, etc. But because the whole system was developed and tested with that Inertia spinning twice engine speed with the crank, the system resonance will change, maybe enough to make a difference, maybe not. If you won't touch the VVT, maybe you ought to leave the balance shaft alone too.

Electric water pumps are great for drag racers. No power taken from the engine during the run, just drawn from the battery. In an airplane used for travel, well, the power used to drive the water pump has to come from the crankshaft, either from the belt drive or detoured through the alternator with losses at alternator, controls, wiring, and electric motor. If the pumping and pump rpm are the same, same power at the impeller shaft.

If the electric one runs really low power, maybe it is not moving much water, which might be OK on a drag racer, as they only make big power for seconds, while our airplane has to be able to cool in steady state...

We will usually run idle speed such that the prop runs 500-600 rpm, and usually never over 2700 rpm. And a prop at low rpm, the power and thus the waste heat is pretty small. You can only make big waste heat at big rpm, when an engine driven pump running fast. Cars have to cool well at big torque even at lower engine speeds so the stock FEAD ratios probably run the stock pump (and alternator) pretty fast. You can probably run your alternator and water pump at significantly lower speeds than in the car or truck. Water pump power is torque times speed, and the water pump torque goes with speed squared, so power goes with speed cubed. Down to 80% speed, and you are at 50% power for the pump, 63% down to 25%. Alternator power goes with square of rpm squared. Yeah, new pulleys and maybe belts, but if this engine is 3/4 of a V8, maybe there are race pulleys out there that will fit both V8 and V6...

That is enough for now.

Billski

Last edited: May 13, 2019
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14. May 13, 2019

### wsimpso1

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More.

Power brakes have historically been powered with manifold vacuum. Diesels never have manifold vacuum. Some run a vacuum pump, some run a hydraulic pump, heavy trucks run springs and compressed air. Biggest reasons to run pumps for brake boost are irregular brake boost, start-stop systems. You want the brakes to feel the same all the time. Irrelevant to us airplane guys.

DOHC lets your engine breath better to higher rpm than SOHC. Peak torque usually occurs at a higher rpm, and the torque falls off slower after peak, so the horsepower claim and performance at WOT is higher... Great, but most of us will derate a little by setting max operating rpm lower than in cars and trucks. The SOHC heads will usually do just fine to our reduced max rpm, and shave quite a few pounds per head.

Have fun guys...

Billski

15. May 13, 2019

### pfarber

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So you didn't read the thread WHERE HE WEIGHED THE SHAFT???? Dear lord man, don't just start making claims when the information is in front of you.

You didn't read the posts about the dyno tests and that electric pumps are used in high end street vehicles? I mean if you can type a post FULL OF WRONG INFORMATION clearly you can read the posts that explain everything, in detail???

Another 'I didn't read the article' and worse, can't do math. The AVERAGE DYNO TESTED increase in HP was between 5-20HP with an electric water pump running off an alternator.

TIL: most people are not doing ANY research yet post WAG about how things work. Get informed or stay quiet. I rarely post something without a source to back it up.

16. May 13, 2019

### wsimpso1

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All the hot rod mag articles in the world can not exempt anyone from the laws of thermodynamics. Good luck with your perpetual motion machine...

17. May 13, 2019

### pictsidhe

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Try reading the article again, a little more carefully. I suspect that it was deliberately a little unclear as magazines exist to sell featured products.

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18. May 13, 2019

### Toobuilder

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Pfarber - If you can put down your matches for a second, can you tell us what kind of flying experience you have?

19. May 13, 2019

### mm4440

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Hi, when you see how engines are dressed on the dyno with an electric water pump there are typically no belt driven accessories on them. Dyno time is expensive and it speeds up testing. Both V-6 engines are worth considering in detail: size, weight cost, etc. Cylinder deactivation and VVT can be deactivated. They have no benefits for aircraft use and introduce more failure modes and control challenges. Do not remove balance shafts, you will be sorry if you do. They are used for comfort and to keep the engine from shaking itself to pieces. The cost effectiveness and simplicity of an LS based V-8 solution for 250 hp and up would be my choice.

20. May 14, 2019

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