Extrude Honing

I've seen many references to dyno testing of extrude honing and I'm left a little sceptical.

Not sceptical that extrude honing is a good thing, but sceptical that the results are inflated.

For example take this article:
http://www.nissanperformancemag.com/june05/qg/

They dyno the car, then add the extrude honed manifold and did some "minor fuel tuning" for the second run.

Ostensibly to "compensate for the extra airflow" which is BS. The cars ECU gives it extra fuel if it detects extra airflow.

It's not an accurate test if you screw with the air/fuel ratios.

screw with the air/fuel ratios.

it is if they are off....

I have nothing useful to add to this, but extrude honing is some pretty cool stuff, and can be effective in the right situation.

I wish AFR tuning was so simple. The computer might have adaptive capability, but that doesn't mean its capable in dealing with every single possible situation. Sometimes you not only have to change the mixture blocks, but the throttle fuel enhancement (aka, the "accelerator pump" action).....which isn't handled by an adaptive ECU.

it is if they are off....

If they are "off" then it should be sorted before the first baseline is taken.

If they are "off" then it should be sorted before the first baseline is taken.

not following you there. If you change things in the system, your baseline is meaningless compared to the new parameters.

not following you there. If you change things in the system, your baseline is meaningless compared to the new parameters.

That's my point.

If the test is to see what improvement the extrude honed manifold makes, then changing other parts of the system makes the test meaningless.

That's my point.

If the test is to see what improvement the extrude honed manifold makes, then changing other parts of the system makes the test meaningless.
so anything that changes the base parameters is uncomparable??

Ok.....

you can't have your cake and eat it too. If you make a drastic (or even not-so-drastic) change, it will change parameters. That is the whole purpose of making drastic changes to the parameters.

For example, going from a standard single TB to a ITB setup will drastically change your engine management parameters, are you suggesting that those two situations aren't comparable also, since you MUST change EM settings to make both work?? By that definition, very very few changes are ever comparable.

IMO, HP is the name of the game. You go for optimal EM conditions in both situations and compare the HP curve. That will tell you which is more worth while/cost effective. If you are only willing to make changes that require no EM manipulation....well....I guess you'd be better off selling the car and buying something that is closer to your desires. Might be less headaches, but won't necessarily be cheaper!

so anything that changes the base parameters is uncomparable??

Ok.....

you can't have your cake and eat it too. If you make a drastic (or even not-so-drastic) change, it will change parameters. That is the whole purpose of making drastic changes to the parameters.

For example, going from a standard single TB to a ITB setup will drastically change your engine management parameters, are you suggesting that those two situations aren't comparable also, since you MUST change EM settings to make both work?? By that definition, very very few changes are ever comparable.

IMO, HP is the name of the game. You go for optimal EM conditions in both situations and compare the HP curve. That will tell you which is more worth while/cost effective. If you are only willing to make changes that require no EM manipulation....well....I guess you'd be better off selling the car and buying something that is closer to your desires. Might be less headaches, but won't necessarily be cheaper!

Yes I'm saying if you change two (or more) variables to get a result, it's pointless trying to attribute the result to only one of those variables.

Do you think changing a factory manifold for an extrude honed one requires a retune of a/f ratio?
Or do you think it was done to fudge the test results?

Yes I'm saying if you change two (or more) variables to get a result, it's pointless trying to attribute the result to only one of those variables.

Do you think changing a factory manifold for an extrude honed one requires a retune of a/f ratio?
Or do you think it was done to fudge the test results?
I think two situations that have the exact same AFR's are comparable. How you get those results are note worthy and very important. A modification with bad AFR's isn't note worthy since its only showing where your EM is lacking, not where your modification by itself is lacking.

lets take an extreme example, you throw a turbo on a NA car. You do absolutely nothing to the EM. You lose HP because it falls on its face when you hit boost. You decide that turbo's are a complete waste of time, because they cause a loss of HP. Is your modification at fault, or the EM? I'd say the EM is most definitely at fault. You didn't compensate for the modification, and this caused the lackluster results. You can't ignore the EM when you modify a system.....that is my simple point

I think two situations that have the exact same AFR's are comparable. How you get those results are note worthy and very important. A modification with bad AFR's isn't note worthy since its only showing where your EM is lacking, not where your modification by itself is lacking.

Given that the car is running on a closed loop controller. Why would you suspect the AFR was bad?
Why would you need or want to alter the AFR for a modification as simple as a polished intake manifold?

Is it simply a case of richening the mixture before the bolt on is dyno'd to make the reported power gains significant?

Given that the car is running on a closed loop controller. Why would you suspect the AFR was bad?
Why would you need or want to alter the AFR for a modification as simple as a polished intake manifold?

Is it simply a case of richening the mixture before the bolt on is dyno'd to make the reported power gains significant?
I see two problems with your above post. A) you assume anything with a closed loop is always just right on the cruise AFR (as if cruise AFR's means anything towards peak numbers) and B) richer equals more power IE take any closed loop system and force it into open loop with richer mixtures and it will magically have higher HP numbers no matter what.

FYI, there isn't a system out there that stays in closed loop at WFO (WBO2 setups are a little different....not quite closed loop since they are meter optimal peak AFR at WOT)

Correct me if I'm wrong.

I see two problems with your above post. A) you assume anything with a closed loop is always just right on the cruise AFR (as if cruise AFR's means anything towards peak numbers) and B) richer equals more power IE take any closed loop system and force it into open loop with richer mixtures and it will magically have higher HP numbers no matter what.

FYI, there isn't a system out there that stays in closed loop at WFO (WBO2 setups are a little different....not quite closed loop since they are meter optimal peak AFR at WOT)

Correct me if I'm wrong.

If you've finished editing.:iceslolan

I didn't mention cruise AFR, I asked why you would suspect it was a bad AFR?
Althought dyno'ing an engine at cruise AFR then peak power AFR would give the results most component makers would love.

If the engine is running leaner than the maximum power AFR then yes richening the mixture will give power increases. Given the QG18de is a lean burn ULEV engine, it's a fair assumption it doesn't run that rich.

I think your both running around each other, with out actualy argueing about the same thing.

There are lots of stock spec engines, that even factory new, are not tuned to give thier full potential hp. Its usualy for reasons of driveablity, engine life, and fuel economy. Often a simple retune of the ECU to tweak the AFR is all that needed liberate a noticable increase in HP.
If such an engine was tested by someone, who want to show false increase in performance from the fitting of another part, it would be very easy for them to run the car in its normal state of tune, then add the part, and tweak the AFR which on its own will give a noticable performance increase.
Its then possible to word an add or article in such away to make it look like the added part, rather than the AFR tweak was the cause of the power increase.

Of course as has been mentioned by someone in here already, you can just make lots of runs on the same dyno, and easily get two runs with a 5+% differnce in power due to the dyno's own inaccuracies.


And of course, if you modify or replace any parts that have an effect on the engines airflow or fuel delivery, then depending on the ECU fitted its quite likely you will also have to make a manual adjustment to the AFR.


All of it just goes to show why you should be VERY wary of anyone trying to sell a product based solely on claimed performance increases shown on one model of car on a Dyno.


As for extrude honing, I have very little experiance with it, but Iv only ever seen it used by people who simply wanted to add another bit of work done to the display board at a car show, or on race cars so heavily modified there wasn't anything else left to change.

Also remember that a perfectly smooth surface isn't always the best for promoting fast air flow, and that some engines rely on a turbulant inlet flow to properly mix the fuel with the air.
While extrude honing may have some benifits, it should be looked at like all engine mods, and considered only on an engine by engine basis, not used as a magical cure all and performance enhancer.

Also remember that a perfectly smooth surface isn't always the best for promoting fast air flow, and that some engines rely on a turbulant inlet flow to properly mix the fuel with the air.
While extrude honing may have some benifits, it should be looked at like all engine mods, and considered only on an engine by engine basis, not used as a magical cure all and performance enhancer.

Couldn't have said it any better. What do they call that phenomenon?... laminar barrier or turbulence barrier... something like that. The little bit of stalled air stuck on the edges of a textured tube makes a barrier. The flowing air is only frictioned against the stalled air. A smooth surface won't trap that barrier and the flow can be reduced since its turbulently rubbing against the side itself. I haven't ever really seen numbers but that was actually a chat I had with an Extrude Hone guy in Pittsburgh when I was considering it for my LT1 intake manifold.

Its then possible to word an add or article in such away to make it look like the added part, rather than the AFR tweak was the cause of the power increase.

this goes both ways. I don't really see how this point is even note worthy. I could talk for days about people modifying a motor, being idiotic about the EM to compensate for the mod's, and losing HP, or at the very least, not getting anything near their peak capability, because they don't want to mess with it.

And lets not even bother talking about the millions of people that have turbo'd something and imediately blew up the motor for the same reasons.

EM is important. Pay attention to it....even if you consider it "cheating". If its not necessary for whichever mod you're considering....then don't worry about it

Couldn't have said it any better. What do they call that phenomenon?... laminar barrier or turbulence barrier... something like that.

Boundary layer?

this goes both ways. I don't really see how this point is even note worthy.


Well the first post in the thread questions the worthyness of the results.
And while they show that on a spefic engine, when extrude honing combined with an ECU tweak can produce a measurable performance gain, they do not show that the same gain can be applied to all engines, which is what is implied in the article.
It is basicly falsly promoting the benifits of extrude honing, when in reality there may not be any, and in some cases may decrease performance, or have no effect on it what so ever.

This sort of marketing is used far to often in the auto industry, although this is a very mild example, and mostly down to bad journalism.

Remember that as a percentage of the potential market, those of use with advanced amature knowledge make up a very small percentage, so the majority of people who read that will come away thinking extrude honing does wonderful things to any engine, and if you want to make lots of hp its an essential step. When of course the reality is quite different.


Not questioning the use of extrude honing as a performance inhancement, just its use in all applications.

A friend of mine (who I consider one who posseses a lot of "advance Amateur knowledge") and has taught me a lot (especially about the importance of chassis mods - stiffening etc along with engine mods ) had me convinced that I should extrude hone my intake on my 86 Mustang 5.0. As some of you may or may not know the 86s used a 58mm TB and E6SE Heads (These heads are considered to be restrictive). The next model year a gain in perfomrance occured via a 60 mm TB and a different type of head (7E truck heads). These were the significant changes that resulted in 25 more HP and more torque.

He extrude honed his 89 5.0 and is convinced (although he does not have data) that it has significantly improved his performance (well the car's performance anyway). I was planing on doing the same to mine to help compensate for the shortcomings of the 86 set-up.

Now I am having 2nd and 3rd thoughts.

I think you should look at the cost of honing vs the cost of a throttle body, inlet manifold and head swap.
After all you have to remove everything anyway to extrude hone it, the cost of the honing might be as much as, or more than the cost of the replacement parts.
Especialy since as a pretty good general rule, if you remove a head, you rebuild it.

I would get your mates car on a dyno, and see how it compares to.
Often, and Iv experianced it myself, after spending lots of money on parts any performance gain can be largely phsycological.

I think you should look at the cost of honing vs the cost of a throttle body, inlet manifold and head swap.
After all you have to remove everything anyway to extrude hone it, the cost of the honing might be as much as, or more than the cost of the replacement parts.
Especialy since as a pretty good general rule, if you remove a head, you rebuild it.

I would get your mates car on a dyno, and see how it compares to.
Often, and Iv experianced it myself, after spending lots of money on parts any performance gain can be largely phsycological.

To be honest the whole car needs to be restored/rebuilt and I was planning on replacing the heads and tb with the improved versions as I have a source.
I still may have piston clearance as my pistons are flat top........but enough of that for now.

In any event I used to be sure that extrution honing "couldn't hurt" but after following this thread I see "the other side" so I will have to research. My friend's car on a dyno would not be relevant as he has made many other mods too.

extruding is like head work. You can't lump all examples together. Some systems will definitely benefit greatly from it, because you removed a big restriction to a system. Other systems may not be so happy with it, because you DIDN'T have much of a restriction there, and you lose all velocity by making it bigger. This can not only give you holes in the power band, it can cause a loss in peak hp also, regardless what you do to the EM.

This isn't so simple as do X and you will gain 30 hp. Nothing is ever that simple when you're discussing air flow through an engine.

If you are doing a very light extrude, just to clean up the machine marks and round off the edges a bit, thats different....and honestly, I doubt it makes much difference.

Some systems will definitely benefit greatly from it, because you removed a big restriction to a system.

How exactly is extrude honing "removing a big restriction"?

by removing material?

I don't understand your question. The process involves removing material. The question is, is the material you're removing beneficial or not.

by removing material?

I don't understand your question. The process involves removing material. The question is, is the material you're removing beneficial or not.

You're claiming it can remove a big restriction. Which requires removing a lot of material.

I don't believe extrude honing is capable of such a feat. It's main claim to fame is surface treatment. Which can not remove a major restriction.

There's a limit to what can be acheived by pumping abrasive grit throgh a passage.

You're claiming it can remove a big restriction. Which requires removing a lot of material.

I don't believe extrude honing is capable of such a feat. It's main claim to fame is surface treatment. Which can not remove a major restriction.

There's a limit to what can be acheived by pumping abrasive grit throgh a passage.

I didn't say it WOULD remove a "big restriction" I said it COULD.

Extrude honing forces a clay like substance (ie, very heavy thick stuff) through a port. When the forcing of it through the shape, if there is a narrowing of the shape, the force is increased. The increased force will apply more material removal there.

There is no limit on how long you leave the machine on. If you leave it on long enough, it'll hone the object to the point that there is huge holes poking out. Thats a lot of material being removed.

There is no limit on how long you leave the machine on. If you leave it on long enough, it'll hone the object to the point that there is huge holes poking out. Thats a lot of material being removed.
So how long would that take?
Days? Weeks?
How much would they charge you?

But the big problem is, it's not targeted, the outside of bends will get more honing than the inside, whether it needs it or not.
Your gas flow may be worse, not better.

Of course this could be easily refuted by dyno tests, but we don't have any reliable evidence.

Do you have any undisclosed interest in the extrude hone companies or methods?

Your gas flow may be worse, not better.


gosh....that sounds familiar :banghead:

Good luck.

gosh....that sounds familiar :banghead:

Good luck.

Try reading the whole post in context. It'd help your replies.

I am no expert by any means but I thought the whole point of the honing is not to remove material (although by definition some will be removed) but rather to polish the surface. The amount removed should be insignificant but the theory is that the airflow will be less turbulant and thus less resistive to flow resulting in an increase in airflow. If the honing process removes more material than is necessary to polish the surface then it is probably not being done correctly.

Of course reading through this thread it seems like another "angle" that was mentioned is that the air to metal (aluminium) resistance may be greater than the air to air resistance (created by the non-moving air film that a casting grade smoothness traps) may be less. I am not sure I totally buy this theory because at the molecular level there is still a lot of roughness, but the theory is certainly worth consideration.

I am not sure I totally buy this theory because at the molecular level there is still a lot of roughness, but the theory is certainly worth consideration.



Golfballs.

Your gas flow may be worse, not better.




psst, thats exactly what Unclebob has been saying :wink:

some engines rely on a turbulant inlet flow to properly mix the fuel with the air


Ive noticed intake inlets for sale on several performance websites which supposively twist the air flow into the intake manifold (sort of like a twister tornado) for better intake performance. Are those inlets even worth spending money for?

Are those inlets even worth spending money for?


Common question, there are several threads on it.
The answer is always no.
These things a complete waste of money, more likely to inhibbit air flow than promote it.

psst, thats exactly what Unclebob has been saying :wink:
I was talking in global general terms, he was asking specific detailed questions about particular aspects of the same terms. The answer is the same in both situations IMO, but I won't bother argueing the point further.

My main point wasn't to diss the proceedure, only to add a dose of reality. Not all intakes are the same. Not all heads are the same, not all extruding services are the same. The end result is material removed. These are facts. Results will definitely vary.