extrude hone alternatives? (3.2 intake)
 

I understand the concepts behind the benefits of extrude hone, and I understand that it would only benefit when the air need of a cylinder exceeds the capacity of the plenum with the poorest flow (assuming there is not a more significant upstream bottleneck). I.e is is of benefit in cars with more power, and presumably other upstream intake mods.

So my question is, has anyone mimicked this process (the original process uses abrasive clay) without cutting open the intake, polishing, and then re-welding? i.e. has anyone mechanically polished the intake with a flexible abrasive device like a metal brush (think chimney sweep for lack of better terms).? Sure it would be imperfect, and challenging in the plenum bends, but I am just trying to think about a feasible alternative that does not involve 1K after shipping my plenums across the continent.

With the right gear, you could still flow match, and even if you did not, blindly polishing all plenums, even a bit, would improve flow rates and at least raise that ceiling where the cylinder air demand exceeds the capacity of the plenum with the poorest flow.

Another way to look at this is, for those that had an extrude hone flow report, which plenum/cylinder had the lowest flow pre hone? I know people report differences as high as 30%. I suspect there will be a pattern there as some are further from the throttle body than others. My logic here would be the "poor/lazy mans solution" to hone out only the plenums with the lowest expected flow. Again, raising your ceiling. Sure, you would not know how much you raised it, but you would.

thoughts and experiences would be appreciated. This is an exercise in mental masturbation as much as anything.

After 'extrude honing' was referred to me as an option, I tried to figure out what it meant and was unsuccessful. So, I began looking into something I DID understand, which was displacement. My current exploration is in obtaining a 3.6L engine. That's actual HP. The 'extrude honing' sounded like voodoo to me.

I would, however, defer to someone who actual figured out what 'extrude honing' is and whether or not it produces real horsepower.

I am going to 3.4. As you know an engine is an air pump. To make more power you need more fuel, and more air to match. The more air you can get into the combustion chamber, the more fuel you can add for increased power. The more power the engine produces, the more demand it puts on the intake. Eventually, the intake needs to be opened up (usually limitations are seen in high rpm's where air flow needs are higher). Extrude hone is one way to open up or at least improve the efficiency of the intake. I don't see a lot of value on it's own as other intake factors will limit things first, but that is getting off topic anyway. Same for the 3.6. I know the benefits of that swap, I am just trying to reason a "poor means extrude hone".

What would be interesting is to know the flow rates of each plenum, and then calculate the flow demands of each cylinder given a set hp. You could then go through the entire intake calculating rough flow rates based on cross sectional area and determine where the restrictions are largest. You open that up. It would be interesting what flow rates (engine hp) would be required before the plenums (extrude hone) actually become the bottle neck.

Dogma from some folks around here is that the airbox is the low hanging fruit of intake limitation. That is why cone filters or open airboxes add power on the top end. Another is the AFM itself. Another is the throttle body, and finally the plenums. I suspect the plenums themselves don;t become a significant restriction until engine hp becomes quite significant.

I think you are right here.

My understanding is that there are far greater intake restrictions upstream of the plenum and until they are addressed, there isn't much benefit to extrude honing the intake. But a big benefit is balancing the flow between cylinders.

So I would love to see what people found in regards to flow per cylinder. These intake plenums were cast, so there is a strong possibility that the flow indifference is a result of the mold and could be repetitive. So one could say, work on improving the flow of a single cylinder to balance things out.

Exactly! It would not be as ideal as extrude hone, but would give most of the benefits if you could polish the offending "slow" plenums.

See here... Porsche 911 SC Carrera Machine Work - European Cars Magazine

Thanks for that link. Pretty clear 1 and four are down on flow, which mskes sense given they are furthest from the throttle body. 2 and five are closest, so have the best flow, and 3 and six are in between.

Will be interesting to see more examples to see if this pattern holds up.

Do the low hanging fruit would be to polish 1 and 4. Too bad, as they would be the hardest to reach from the top.

#1 277 351 (numbers are flow before and after)
#2 280 349
#3 280 351
#4 295 351
#5 286 349
#6 289 352

This is the data from the linked article above

#1 - 197/322 +125 CFM gain

#2 - 313/335 +22 CFM gain

#3 - 227/331 +104 CFM gain

#4 - 197/348 +151 CFM gain

#5 - 313/339 +26 CFM gain

#6 - 233/335 +102 CFM gain

1 257.1 290.3
2 253.2 298.4
3 250.9 297.7
4 264.7 294.6
5 250.4 300.6
6 260.8 297.1

Exhaust port image
 

I had opportunity to remove my exhaust recently and it gave me a chance to look at the exhaust ports, here are 2 pics of #1 & #4. Is the difference in burn color attributable to the constricted flow through intake?

http://forums.pelicanparts.com/uploa...1426263430.jpg


http://forums.pelicanparts.com/uploa...1426263457.jpg

Of interest, not everyone has a lot of variability of flow between plenums in stock form. Thus, to eval need, it might first be best to flow test the plenums.

Two out of the three plenums above have what i would call statistically insignificant differences in flow out of the box.

I wonder if early vs late castings had variations. Maybe they identified the issue at the factory and corrected the design for the later 3.2's...

Allan, many factors could be at play. I will go on a limb and speculate that in a stock engine, the plenum flow will not play a part in what you see.

How about just adapting a plastic 964 intake?

I read about that with the adpators. Would be light... But i like the oem look.

Does Extrude Hone actually claim to balance the flow or do they just run the abrasive through all ports and call it a day? Do they provide before and after flow numbers for each port?

If anyone wants to get really ambitious there is info out there on building your own flow bench. I haven't seen it in Pelican, but I know Hot Rod magazine had an article a number of years ago. Then, you could experiment with porting using old fashioned abrasive tools powered by a hand drill with a flexible shaft to which the abrasive wheels are attached.

To answer your question, yes. I had my done years ago. When I did mine, there was a HUGE discussion about several of the ExtrudeHone locations not doing the job correctly. In the discussions (way back when), it was found that the location that did the best work was the one in Wisconsin.
I sent mine off to the WI location, and within 2 weeks I received mine back. I had paid the extra $60 or so to get the before and after flow results. The intake came with a computer printout of the before and after results. It didn't increase a lot, ( maybe 60 CFM or so...) But, what it did do was even out the flow between ALL of the runners to within 10CFM. Before, there was a disparity of which the greatest was 80CFM.
That might not make a difference to a person with a stock engine. But, with mine pushing over 800HP and running on the ragged edge, I didn't want to lose an engine because of an imbalance.
They do have a good process. Its a media that contains walnut shells. When they force it through a part, it flows through it like water. (water takes the path of least resistance), so it only really takes away metal at the point of the most restriction. It really doesn't open it up much, just makes it flow better, and equals everything out.

All the numbers were before and after that i copy/pasted from other threads.

I did mine too when I did my 3.4 - per Steve Wong - the biggest difference is above 5,000 rpms and the absolute difference is only about 7 HP above 6,000. THE biggest benefit is evening out the flows of the runners - mine too were off close to 20% so it definitely makes sense to try and even things out especially as you try and optimize your engine.

Extrude Hone is far from voodoo. It mimics actual airflow by using a paste with abrasive particles pumped through the passages.

Tried and true for decades.