A&Q about 350Z
Q:
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:
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.
A:
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.
A:
If they are "off" then it should be sorted before the first baseline is taken.
A:
not following you there. If you change things in the system, your baseline is meaningless compared to the new parameters.
A:
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.
A:
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!
A:
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?
A:
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
A:
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?
A:
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.
A:
If you've finished editing.
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.
A:
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.
A:
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.
A:
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
A:
Boundary layer?