I've got Spark Knock!

[TeamFordRaptor]

The spark knock is really getting to me. :mad2:

My motor mods are Volant CAI, Flowmaster 44 Catback, and now a Superchips tuner.

The spark knock hasn't changed so I'm going to switch to 91 octane fuel.

I do have a few questions for those who have knowledge on this:

1. How many tanks after I switch to 91 should i give it to tell a difference?
2. If that doesn't work is octane booster my last shot?

Im just totally perplexed on what to do about this problem. any suggestions?

The foreman at ford blames the CAI & Temp, the guys at 4Wheelparts thinks thats BS. JDM says its due to using 87 octane and if that doesn't do it the CAI needs a specific tune, superchips thinks its octane.

On a side note I was told that tuners are not really adjusted for a specific CAI and that the tuner simply notices a difference in air levels and adjusts accordingly. It has no idea if it's a CAI or a change in altitude or temp.

Those who suggest 91 or 93 octane, these are not applicable solutions for a spark knock. If there is a sprak knock with 87 octane, the problem will only increase and possibly become louder with higher octane (Higher octane, hotter ignite, louder knock). Octane booster again will only make the louder knocks, well, louder. Understandable if the engine is sluggish or you've added a supercharger or turbos, but with a Spark Knock, less is more. This isn't my or one mans opinion, this is Ford's and any intelligent mechanics knowledge. Got off the phone with Ford and 4 engineers just minutes ago.

The CAI does NOT need a tune. The computer still has the capability of reading the air flow regardless of stock or aftermarket. The computer then adjusts the mixture accordingly. Ford engineers have specifically designed this engine to run at a certain temp with air and fuel factoring in all these things.

The tuner has nothing to do with the knock as I'm sure everyone is aware also. The tuner is most cases would run smoother with 91 octane, but again the spark knock will only grow the more you add.

We are looking for a solution to the specific problem and I will post again when we nail it. Thanks!

 

[Hockster]

Those who suggest 91 or 93 octane, these are not applicable solutions for a spark knock. If there is a sprak knock with 87 octane, the problem will only increase and possibly become louder with higher octane (Higher octane, hotter ignite, louder knock). Octane booster again will only make the louder knocks, well, louder. Understandable if the engine is sluggish or you've added a supercharger or turbos, but with a Spark Knock, less is more. This isn't my or one mans opinion, this is Ford's and any intelligent mechanics knowledge. Got off the phone with Ford and 4 engineers just minutes ago.

The CAI does NOT need a tune. The computer still has the capability of reading the air flow regardless of stock or aftermarket. The computer then adjusts the mixture accordingly. Ford engineers have specifically designed this engine to run at a certain temp with air and fuel factoring in all these things.

The tuner has nothing to do with the knock as I'm sure everyone is aware also. The tuner is most cases would run smoother with 91 octane, but again the spark knock will only grow the more you add.

We are looking for a solution to the specific problem and I will post again when we nail it. Thanks!

Add the fact that these so called CAI's are not really CAI's... They draw underhood air... They do not draw cold air... I have seen temps up at 167 here is Va and out west they are ever greater... You cant get performance drawing that hot of intake air... The PCM sees that and makes adjustments for it... add to that the fact that hot air is less dense... You can get some performance after the air is cleared out but that takes 10-15 seconds when drawing underhood air...At the stock location its 2 seconds to get colder air... I have been taking videos and reading with my thermocouples at the stock location and underhood... It takes to much time to clear the hot air from underhood to get good performance... and as soon as you stop is the temp is back up again.. When you see CAI dyno testing they always have the hood open.. When do you drive your truck with the hood open?
Fo my suguestion I would stop drawing underhood air to see if that stops the knock... I do have some years of experience at this.. I worked in powertrain calibration at Ford for 11 years... and retired after 30

 

[Madcowranch]

I love all the combined knowledge represented on this forum!

 

[MarkT]

Those who suggest 91 or 93 octane, these are not applicable solutions for a spark knock. If there is a sprak knock with 87 octane, the problem will only increase and possibly become louder with higher octane (Higher octane, hotter ignite, louder knock). Octane booster again will only make the louder knocks, well, louder. Understandable if the engine is sluggish or you've added a supercharger or turbos, but with a Spark Knock, less is more. This isn't my or one mans opinion, this is Ford's and any intelligent mechanics knowledge. Got off the phone with Ford and 4 engineers just minutes ago.

The CAI does NOT need a tune. The computer still has the capability of reading the air flow regardless of stock or aftermarket. The computer then adjusts the mixture accordingly. Ford engineers have specifically designed this engine to run at a certain temp with air and fuel factoring in all these things.

The tuner has nothing to do with the knock as I'm sure everyone is aware also. The tuner is most cases would run smoother with 91 octane, but again the spark knock will only grow the more you add.

We are looking for a solution to the specific problem and I will post again when we nail it. Thanks!

Octane is the measure of a fuel's ability to resist preignition (aka "spark knock"). Period. Higher octane fuel does not necessarily "burn hotter" and using a higher octane automotive pump gasoline most definitely will REDUCE knocking.

(I've spent many hours testing various gasolines and octane boosters using a certified Waukesha ASTM-CFR test engine... at the time I was a member of the SAE.)

I do understand that the computer should be able to read the airflow and the sensors should adjust the fuel trim to get the mixture correct. But as I understand this issue, it is not a "steady state" problem. It happens under acceleration.

A few things I can think of:

Resonance in the intake pipe can wreak havoc on the fuel mixture/air delivery. It is possible that the particular intake has a detrimental resonance that "fools" the MAF.

It could be that the "free flow" of the air filter requires more "accelerator pump" richening which the computer can not compensate quickly enough for.

It could be that the higher intake temperature (caused by drawing hot under-hood air) is contributing or causing the issue. Increasing the intake air temp just a few degrees has a significant effect on knock. I've personally done the tests under laboratory conditions. (and the tests agree perfectly with what Hockster said.)

 

[TeamFordRaptor]

Octane is the measure of a fuel's ability to resist preignition (aka "spark knock"). Period. Higher octane fuel does not necessarily "burn hotter" and using a higher octane automotive pump gasoline most definitely will REDUCE knocking.

(I've spent many hours testing various gasolines and octane boosters using a certified Waukesha ASTM-CFR test engine... at the time I was a member of the SAE.)

I do understand that the computer should be able to read the airflow and the sensors should adjust the fuel trim to get the mixture correct. But as I understand this issue, it is not a "steady state" problem. It happens under acceleration.

A few things I can think of:

Resonance in the intake pipe can wreak havoc on the fuel mixture/air delivery. It is possible that the particular intake has a detrimental resonance that "fools" the MAF.

It could be that the "free flow" of the air filter requires more "accelerator pump" richening which the computer can not compensate quickly enough for.

It could be that the higher intake temperature (caused by drawing hot under-hood air) is contributing or causing the issue. Increasing the intake air temp just a few degrees has a significant effect on knock. I've personally done the tests under laboratory conditions. (and the tests agree perfectly with what Hockster said.)

I don't feel like arguing so I'll leave it at this. I sepnt over an hour talking to Dearborn Engineers a few days ago, 4 to be exact along with mechanics and my shop foreman. Higher octane will not reduce the knock. Period. Pre-ignition resisting is correct, however higher octane does burn hotter, but it does as such that the engine runs cooler since it burns faster. What happens when it burns faster? The timing speeds up. Timing speeds up as well as the spark knock. I've spoken to Chris (Riku) and he agreed that the knock was louder with the higher octane. I can appreciate individual testing, opinions, or even a group member where similar results can be seen. This does not take over 10 years of R&D by Ford along with the knowledge and experience backed by it from the engineers and mechanics.

The air flow doesn't matter. The computer senses this no matter what air intake you have, stock or aftermarket. If it was a year 2000 Heritage style F-150, sure the computer could be slow enough. Not now the computer can handle most whatever you throw at it engine wise (It's a Raptor, it controls ELD, Off-Road Mode, Hill Descent, Traction Control, ABS, Transmission shifts both Sport and Normal, among other things. The engine is the smallest thing the computer controls in the sense of what it does. Chris has even tried an aftermarket tune along with trying a tuner. It still does it.

I don't want to sound mean, cocky, or rude but the issue is still there with Chris and his Raptor so the time for theories, opinions, and one man test runs need to stop. Some of the suggestions given in here void the warranty on the Raptor, anyone aware of that? If you are, great! Be sure to state that in your post. Chris has done some things to the truck that he has to reverse and then hope that Ford lets it slide. Aftermarket tuners, engine tunes, even things such as wheels and tires, Ford has already denied warranty claims. The truck is set to run top notch the way it is set. If it doesn't- HEY, GREAT NEWS!!! There's a warranty!!! I've already had 2 of my customers lose there warranty because they went out and changed the geometry of the suspension, tuner, and wheels then brought it back in for a transmission problem... EEEEGGGGGGHHHHHHH! Game over!

If anyone is upset from my post, my cell is (623) 302-6244. My dealership for mechanics and my managers is (702) 395-5100. We all will be more than happy to explain warranty do's and don't's as well as engine and overall truck troubleshooting. Our mechanics, managers, and especially myself are very passionate about this truck, more so than most owners. We have to, we sell it and take your money so we better stand behind our product. Especially one that I will be buying when mine arrives. This is why we don't enjoy coming in here and telling some of you that you're wrong, because you could be messing it up for someone else. Ford has done their homework, otherwise you wouldn't have the Raptor to begin with. Let Ford fix it. Thanks!

 

[BigJ]

I think something is getting lost in translation. Some of the points you fellas are arguing were covered in my Auto Shop 101 mid term final.

Octane rating, by definition, is a fuel's resistance to auto ignition; aka ping aka knock. The higher the octane rating, the more resistant said fuel is to auto ignition.

Can we at least agree on that?

If we can agree, everything else rolls down hill from there. The statement "higher octane will not reduce the knock" might be entirely accurate, however NOT because of the fuel's octane rating. It might be (most likely is) that the ECU detects the higher octane rating, and adjusts the timing to account for it, therefore bringing conditions back to baseline, therefore reintroducing the knock the higher octane fuel is inhibiting.

So if all that is true then yes, the statement "higher octane will not reduce the knock" is also true for this engine and ECU combo. But its a misleading statement in my opinion because, as we've already agreed, its a counter intuitive conclusion one might draw, based solely on the definition of octane rating. It fails to pinpoint the ECU (aka a big brain) as being in play here, and as the thing that's seeking to return operating conditions to a safe baseline, and that its effectively "tuning out" the effects of the higher octane.

Higher octane rated fuel does NOT burn faster or hotter. Again that's Auto Shop 101. Instead, it allows for more compression of the air fuel mixture, which means more heat (the more you compress air, the hotter the air gets). Also since the mixture is more compressed, there's more 'stuff' closer together to burn, it burns "faster" (bear with me on that; trying to keep it ultra simple for the sake of this discussion). A gas can full of 93 sitting next to a can of 87 will NOT burn hotter or faster if both are set on fire (again, those who know, please go with me on this for simplicity sake). However, 93 when atomized will allow for far more compressing before auto igniting (due to the heat produced by the compressing air) and THAT mixture, a hotter mixture, will burn "faster" than a less compressed, cooler mixture of atomized 87.

But now go back to our already agreed upon understanding of why higher octane fuel in this case doesn't help reduce knock... the ECU is accounting for the higher octane in search of its baseline. So I have to believe the ECU is adjusting the timing and fuel trims (aka how much fuel is added to the air, to create the air fuel mixture) to fire at the time which, not only creates the knock, but also keeps the compression of the mixture approximately the same as with a lower octane fuel... and therefore no additional heat and no additional faster burn.

I appreciate what you're trying to say TFR, and I think your conclusions are correct. However I think your path in getting there might be a little confused, which is where I think Mark is trying to help clarify.

And for what it's worth, I 100% agree with you regarding everything you said about the warranty and who's best to advise Chris right now. He needs Ford to take care of him, and for that to happen he needs to follow your advise. My only issue with your post is the engine theory that seems a little muddled, and the (in my opinion unfair) hammering of Mark because of it.

Hope that makes sense.

 

[TeamFordRaptor]

And of course that's why I said if I upset anyone, please call me. I can exlpain mine and Ford's position as well as apologize if it feels like I attacked you personally. My intent was to K.O. all the opinions that revolved around octane, tuners, tunes, and CAI. Aside from that, if it feels like I attacked anyone directly, without calling me, then I apologize. I'm simply trying to fix an issue that has gone from bad to worse because of comments in this forum that are based on one circumstance or opinion. It's frustrating to have the right answers (not by my word or experience which counts very little compared to those gentleman I talked to at Ford) and have them questioned, ignored, or argued about over one opinion. I am OCD to start, and a true mechanic and racer at heart. When something goes wrong with my Ducati, I don't want guesses, opinions or someone questioning my dealership when I want results. When we all can agree that this is a $40,000+ vehichle and needs to be taken in that respect, then you'll see where I'm coming from. Chris is at the end of his rope cause the knock grew a little louder when he tried what everyone suggested, and with the Sema Show coming up, he wants it fixed. I don't blame him! I don't race my Kawi around the track at 160+ when he has a knock or misfire. Nor do I take my Cobra to a car show if it's leaking oil.

Again, my intent is to get Chris' problem fixed First. Then make sure that everyone understands the mechanics of the engine and this truck. I love this truck, and in some cases your truck would come first to me over you personally (Again, no offense, I'm just a gear head and passionate about it). The post was not targeted at Mark individually other than he was the last one to post something. I would have made the same comments no matter who would have made another post about octane or any of the above mentioned.

Thank you for clarifying BigJ, hopefully this makes more sense as to why I said what I did.
Thanks to the rest of you as well

 

[BigJ]

Well I dont thinks its a matter of being upset TFR. I won't speak for Mark, but I have a feeling he was more concerned with making sure the theory was understood, than with proving you right or wrong. Like I said, your conclusions in terms of what's best for Chris, in my opinion, are dead on. The tough part though is the lines drawn between the dots getting there were a little wonky in places (or more likely just not fully articulated as you'd hoped). And that can be a little tough to overlook in a format like this; the concern is, when the 'next' Chris comes along two years from now and reads this conversation, they might get the wrong idea, and act based on misunderstandings.

We pride ourselves on being the foremost technical forum for all things Raptor... so when something isn't precisely technically correct, we tend to discuss and correct eachother, so that at the end of the day the most 'technically correct' explanation is what remains, even though the correct conclusion may have been reached dozens of posts prior. See what I'm saying?

So no worries. I look forward to seeing Chris' issue resolved, as I know Mark does, you do too, and probably everyone reading this. We're all on the same team here.

 

[boxcartommie22]

it says in your manual that you may have spark knock....mine doesn't..i have k&n cai...i know that k&n does exhausting testing before they release a product.k&n says you donot need a tune with this raptor.

 

[MarkT]

I'm not upset at all. Nor do I feel "attacked". And BigJ is correct. I was just setting the record straight regarding octane ratings. I could write a book on the facts about octane ratings and what they mean.

You might notice I was specific about comparing the octane of "automotive pump gas"... one of the many fallacies is that 100 octane aviation gasoline is similar in octane to racing fuel. Truth? Avgas octane is measured using a completely different set of standards. 100LL Avgas tested using the (RON+MON)/2 methods resulted in an octane rating of about 87... yup, the same octane as regular automotive pump gasoline. (and there are many other reasons not to use avgas... it is simply formulated to meet different standards)

As far as warranty? I have nothing but admiration for the fact that Team Ford (and Ford) is working with Chris to solve the issue in spite of the mods. My theories about the IAT, resonance, and the inability of the computer to compensate are sound and I stand behind them... none of them void the warranty either. :mrgreen:

I'm intrigued by BigJ's "octane sensor" explanation... does anyone know if there is an "octane sensor" in the fuel system? (my experience is that the computer sets the timing based on the knock sensor feedback... )

We're all on the same page here and working towards finding a solution... and believe it or not forum members have helped solve issues before that Ford and the dealer were puzzled by.

What puzzles me are these statements... (and please don't take offense Aaron):

SNIP It's frustrating to have the right answers (not by my word or experience which counts very little compared to those gentleman I talked to at Ford) and have them questioned, ignored, or argued about over one opinion.

SNIP I don't want guesses, opinions or someone questioning my dealership when I want results.

These statements beg the question: If the dealer has the "right answers" what are they? (You've only said it's not the CAI, tune, or octane or any other opinion voiced here.)

Is it a bad knock sensor or some other "conventional" problem? One thing I know is fact is that none of us would continue to try to help solve the problem if it were fixed...