Gen V 5.3l turbo build - 87 octane and AFM/DOD

BoomBoomBamaPhD · October 6, 2021

Let me start by saying hey thanks for having me, new here.

I will probably make a build thread for my 15 Silverado separately, but I felt like this discussion needs to happen.

I want to preface this by saying that I am decently versed on the actual theory and thermo of the discussion as I am a current Engineering PhD student studying combustion. I do however lack the physical experience of boosted applications as well as engine tuning.

The two topics to be discussed here are probably highly controversial and I am not looking to start a pissing contest about anything, but rather a tame discussion.

Please let me know if I should split these into two separate posts, but these would be in the same build for me.

1. How much boost could I run, or power could I make, while running 87 octane. (5.3L "Eco-boost")

And yes, I realize the disadvantages of 87 in regards to a boosted application, but if Ford can do it stock, I don't see why we couldn't do it aftermarket (and probably better tbh).

But for reference, I am not actually looking for a high HP or drag type build. More a reliable DD that will be used for truck things like towing occasionally, but would like to get as much out of it as possible. (haven't even settled on it needing to be turbo)

2. Can the newer (2015) AFM/DOD be upgraded and/or tuned properly to be reliable and retain the intended advantages that were originally intended, with or without adding boost?

Half of 5.3 is close to 2.7(eco-boost), so I don't see why I couldn't leverage the fuel economy of a turbo "4 cylinder" while having access to the full V8 when wanted.

RJSmithers · October 6, 2021

Well I have a turbo 5.3 however I can't quite tell you the level of boost you could run on 87 octane fuel. Being an engineering student studying combustion I'm sure you're more qualified than myself on the topic. I know it's typically standard to run the highest octane readily available as it's more stable and then my engine is even tuned slightly richer on its AFR as a factor of safety. In theory I believe you could run maximum of 15 psi before running into the need to upgrade other parts, that may however require an upgrade to the in tank fuel pump. I'm currently at 9psi and that has me at 450hp at 5200 rpm and 514tq at 4110 rpm with no real other modifications. I suppose 87 octane would be possible in theory, you'd have to see how much knock you'd be getting and adjust accordingly I would think but I am certainly no engine tuner. You might have better luck on https://www.performancetrucks.net/forums/ or even parish8 on camaro6 this is a link to his turbo L83 camaro he built https://www.camaro6.com/forums/showthread.php?t=583101&highlight=l83

I haven't heard of anybody upgrading the afm/dod systems however I haven't been cruising through the newer truck forums, perhaps the 19+ with the dfm systems have upgraded the lifters? I am not sure. Everybody who has one fail seems to rip them out as they don't want to pay to open up their engine again and replace them (I wouldn't want to pay for that a second time either)

Do you have access to ethanol fuel where you are? I don't have the link but I believe another gentleman here just upgraded his 5.3 to allow for e85 and he got in the ballpark of 30hp. That was without any sort of performance tune as well

Can't say I'd be looking into forced induction for practicality though. If I had to do it all over again I'd probably try to find an LT4 take off supercharger and swap that onto my engine.

BoomBoomBamaPhD · October 6, 2021

So is that with a totally stock engine?

Just bolt on turbo kit?

What octane do you run?

I see that I failed to mention an important piece of info. I realize that at 87 octane it would be necessary to decrease the compression ratio if I wanted to build boost without knock.

So all this to say that I wouldn't expect to use just a bolt-on kit with no engine work, I plan on building the engine accordingly.

I sadly do not currently have E85 readily available to me, that would just be too easy though, am I right haha.

I have a love/hate relationship with superchargers though. They are badass for sure, but terribly inefficient. Will def build a supercharged muscle motor in the future though, just not for my daily.

But thank you for those links, I'll have to check them out.

shakenfake · October 6, 2021

No you cannot run AFM with boost. I highly highly recommend you delete it at the same time.

In terms of 87 octane and boost? Not going to happen. You will get pinging. You have got to get 91 or 93.

BoomBoomBamaPhD · October 6, 2021

Hey thanks for joining the discussion. But from here on out how about everyone try to put some thought and explanation in their answers.

Obviously 87 octane can be run in certain boosted applications, aka the Ford Eco-boost. As referenced multiple times in the original post. Though I have already conceded to knowing it is not the most ideal. And with the direct injection of the newer engines I'm pretty sure the only difference fundamentally would be the compression ratio, which I have mentioned being open to changing previously. (Please let me know if there is some other fundamental difference I am missing.)

And as for the AFM with boost, do you have a reasoning it can't be done?

I think I have a pretty good idea of how the cylinder deactivation works mechanically, and I wouldn't think it would be effected really at all by boost or cylinder pressures.

shakenfake · October 6, 2021

Lol okay let me put some more thought into my explanation then. You are comparing apples to oranges with those engines. The tune for that Ecoboost is stupid safe, when on 87 octane. Low timing and low boost basically. BTW the ecoboost is recommended for 91 octane.

Second of all let me roll my statement back. Sure you could get boost out of your V8 but the issue is your timing is going to be weak as hell. You also are going to make basically no power. Instead of getting say ~10hp per pound you are looking at like 3. It is just going to be not worth it. It's not that you can't it's just that it won't be worth it. And you won't be able to run high boost pressure either because of the crappy gas.

The reason why I say no with AFM and boost is because I do not know a single tuner that would do that. I do not really know how AFM would react with boost. I assume it would be okay but the thing you might run into is that AFM just never activates. Your tune would just be incompatible unless you figured out a way to do it or found someone who knows how to tune boost+AFM

BoomBoomBamaPhD · October 6, 2021

I apologize if I came off as rude or ungrateful, I just don't think one line answers are helpful in discussions like this.

I understand that the recommendation is not 87, but nevertheless, it has to be robust enough to be a production engine where most consumers will not think twice about just filling up with regular.

I know that the afm can be "soft-deleted" with tuning, but how complex can you get with it? Is it just a on-off switch, or can you actually tune how/when it activates?

shakenfake · October 6, 2021

Just basically on/off switch. I do not believe you can tune how/when it activates because it is more of a mechanical activation that the computer then reads.

I also would suggest that you should just fully delete AFM as there is no real point in keeping it and you will gain more power without it.

@CamGTPchime in please. You know more than I do.

Amcguy1970 · October 6, 2021

8 hours ago, BoomBoomBamaPhD said:

2. Can the newer (2015) AFM/DOD be upgraded and/or tuned properly to be reliable and retain the intended advantages that were originally intended, with or without adding boost?

Half of 5.3 is close to 2.7(eco-boost), so I don't see why I couldn't leverage the fuel economy of a turbo "4 cylinder" while having access to the full V8 when wanted.

So your thesis is that these motors aren't reliable without boost and they don't operate as intended by your brothers in engineering that designed these motor? Whew, you are off to a rough start... What is your source for this observation, a few threads on the internet you read? There are thousands of these motors with hundreds of thousands of miles on them. Follow the maintenance guideline and chances are very high you won't have an issue, but it is a mechanical unit assembled by robots and people, there can be the rogue issue that gets blown out of proportion or recently a supplier part issue.

In terms of boosting, even though I am good with and a fan of AFM (it saves the V8 for a little longer) if I were boosting the motor I would be going for performance, and with that would want to do it right and would delete AFM. Partly because at that point I see no reason for having it on there when performance is my goal and second to make proper use of the added power I would have the valvetrain upgraded and a cam ground for it. I don't believe AFM was designed for boosted applications so as with any stock component that gets more power thrown to it I would want stronger upgraded parts. With that GM's new boosted motors have AFM on them (LT4 and the 2.7 turbo).

Tyler

KARNUT · October 6, 2021

When the 14s first came out there was plenty of experimental tuners tinkering with the 5.3s. They were on this site. They all recommended using premium gas for maximum performance. KR was the reason. I have some experience with super chargers on my vehicles. All recommended premium fuel obviously. For the same reason the 6.2 recommended premium. It’s part of the tune.

BoomBoomBamaPhD · October 6, 2021

Never meant to sound like I thought the stock engines were inherently unreliable, I apologize for it seeming that way.

Isn't the afm controlled by a solenoid?

And I do agree, most boosted applications are strictly for performance. But a turbo can be used to increase efficiency and versatility of an engine. Which is the reason why manufacturers have added them to consumer vehicles, we all know a lot of performance is usually left on the table through simple tuning with most stock turbo systems.

pokismoki · October 6, 2021

1 hour ago, shakenfake said:

No you cannot run AFM with boost. I highly highly recommend you delete it at the same time.

In terms of 87 octane and boost? Not going to happen. You will get pinging. You have got to get 91 or 93.

doesnt LT4 have afm ?

BoomBoomBamaPhD · October 6, 2021

So that's the second mention of the LT4 now so I looked it up and yes it has afm.

And so does the L3B (turbo 2.7l).

I was not very familiar with the 2.7l from gm so now I think I have even more "ground to stand on."

Wouldn't it be great to basically switch from a turbo 4 to a turbo 8 whenever you wanted/needed? And iirc with the newer engines you can basically choose however many cylinders you want/need at a given time/load.

KARNUT · October 6, 2021

7 minutes ago, BoomBoomBamaPhD said:

So that's the second mention of the LT4 now so I looked it up and yes it has afm.

And so does the L3B (turbo 2.7l).

I was not very familiar with the 2.7l from gm so now I think I have even more "ground to stand on."

Wouldn't it be great to basically switch from a turbo 4 to a turbo 8 whenever you wanted/needed? And iirc with the newer engines you can basically choose however many cylinders you want/need at a given time/load.

I would research farther. There’s a big difference between factory and aftermarket. Iv had a few blown trucks. All recommended premium fuel. As far as cylinder deactivation. If it is all that. Adding a blower wouldn’t change that. If want to learn more about cylinder deactivation. Type in your browser the benefit of cylinder deactivation. I wouldn’t own one. I don’t like DI engines either. I’m holding out as long as I can.

shakenfake · October 6, 2021

You would have to figure out how the AFM works on those. I think yes you could keep it but hell no would I want to and also you would have to figure out the tuning aspect. I only said no because of the tuning reason. Mechanically there is no problem I wouldn't think.

37 minutes ago, BoomBoomBamaPhD said:

Wouldn't it be great to basically switch from a turbo 4 to a turbo 8 whenever you wanted/needed?

But you really wouldn't be because you are no longer utilizing boost when in 4 cylinder mode. I think you might be thinking AFM comes on a lot more often then it actually does.

1. AFM comes on between 20-75 mph

2. AFM is based on throttle position, I can't actually remember what it is but it is low, like sub 30% low. Which means once you open up the throttle and allow the turbo to spool up you are already out of V4 mode and back into V8. So no more V4 turbo.

3. It deals with RPMs but don't know much about that one. Again you will never use the turbo in V4.

My point is is that you are not going to actually use the turbo in V4 mode. And no the newer engines you cannot choose the amount of cylinders you want to use lol

The lifters with AFM is a mechanical operation and NOT electronic.