SPOautos

yea, you would make a intake manifold system yourself for way less than that if you know what your doing. Course, if you dont REALLY know what your doing from an engineering perspective your probably going to loose power rather than gain it.

The best thing would be to find a proven setup and duplicate it for cheap. The only prob is its going to be hard to find a proven setup besides on an all out race car and I dont think it would be very practical for a street car.

STEPHEN

BATMAN

that is nice.........

DamonB

Let's assume you have the perfect design for a 13B-REW intake manifold and let's assume you designed it yourself so that it didn't cost any money.

So for 600 bones you have someone who will build a higher performance tubular intake manifold (replaces both the upper and lower stock pieces) with the throttle body flange, engine side flange and proper bungs for vac hoses, injectors and sensors? I would like to know who it is, I have a lot of work they could do.

BATMAN

My question is does extrude honing kill the low end HP and increase lag since it takes greater air volume to flow through the UIM and LIM?

Also, does a large LIM (and perhaps UIM) slow the velocity of the intake mixture?

BATMAN

http://www.extrudehone.com/price_list.pdf

BATMAN

Another issue is that the "rough" textured surface helps atomize the AF mixture.

While a smooth surface helps in maximizing intake velocity due to less drag.

So which is better?

absolute in both ends of the spectrum?

or is it a combination of the 2?

Tim Benton

iTrader: (1)

the 600 was just for the extrude honing for both the UIM and LIM, add on another 200 or so for the jet hot I'd imagine, maybe a bit more or less.

Tim

93BlackFD

www.batlground.com is who i would have do my custom fab if i were doing so

and damonB, i wouldn't think you'd be worried about vaccum lines, etc, you'd probably be single turbo, and probably wouldn't care.....

think OUTside the box i'd say the biggest limitation is the stockers in the way, once you had a turbular exhaust manifold, a tubular intake manifol would be no big deal

rallimike

iTrader: (1)

With all the money RX7 owners spend on performance items, if someone developed a superior intake manifold, they'd have a big seller. My guess is it's been tried, without enough success to make it worthwhile. I'll know in a few weeks if the extude hone was worth it. I'll post more when I know more.

DamonB

BAH! Whatever you think the rough surface may gain you in fuel atomization (regardless of the fact that fuel in our engines is practically injected right into the ports, so the intake manifold is not "wet"), it costs you much more in airflow. The texture creates turbulence and turbulence inside a closed system decreases flow.

rallimike

iTrader: (1)

I asked EH about this "wetting" effect that some say happens if you smooth the surface of intake manifolds. He claims they have run all kinds of tests, and it never happens.
I have to add that when I was a kid (BTC), any serious performance upgrade included porting and polishing the intake. Now, it seems the only thing discussed is running more boost.

BATMAN

I know, just wondering if the turbulence in that millisecond that the "rolling" air mixture will "churn" the A/F better in the combustion chamber just prior to the combustion event.

DamonB

Any supposed possible gain (I highly doubt it) is completely offset by the poorer flow through the "rough" manifold.

Smooth runners are good for every engine, it's always an improvement.

SPOautos

You might want to read that first sentance again, it says if YOU DO IT YOURSELF. Having it made will cost much more than $600 because its very labor intensive....however the material would be less than $600 so if you did it yourself it could be done. However that gets back to the other sentence about having the skills and knowledge to pull it off.

STEPHEN

SPOautos

Its a combination of the two, you want it slightly rough in some areas and very polished in others. The exact way depends on the manifold design and gets back to the thing about someone needing to be very educated on the subject to pull it off and it work better than stock. As for polishing the stock lim/uim there is no fuel atomization until the very bottom of the lim so you'd want to have it polished slick all the way down to that area at least.

BTW - The stock lim/uim set up does effect performance around 7000rpms when running higher boost

STEPHEN

BATMAN

so smooth right up to the part where it enters the combustion chamber, than a little swirl for the mix?

SPOautos

You want it slighly rough once the fuel is mixed in or else it will seperate from the air

STEPHEN

DamonB

So I guess all these carbuerated race engine builders just polish the insides of the manifold runners and combustion chambers to a mirror finish because they have nothing better to do?

Atomization of the fuel is the key to suspending it in the air. Air and fuel don't really mix, they just travel together. The finer the fuel mist is the better it will disperse into the airflow.

SPOautos

If the wall is polished smooth the fuel wont atomize as well. Do a search on it, I'm sure you can find all kind of information.

If the walls are polished slick in an area that the air and fuel travel together the fuel will stick to the walls. If it is rough it will create turbulence that will keep the fuel in the center with the air.

Also, it might not be that they have nothing better to do....maybe they're just shade tree mechanics that have just never been educated and dont have a flow bench to REALLY do it right. Just because a lot of people do it doesnt make it right, a lot of people also think low rpm tq is benificial.

Also, when I say "rough" I'm not talking about super rough its more like after you do a port job just dont polish it slick, it looks about like you used high grit sandpaper.

STEPHEN

BATMAN

I can see the appilcation of rough surface to better atomization in a carbuerated application.

But it looks like the smoothest surface is ideal for a injection setup.

Tim McCreary

I went to school for aerospace engineering and this turbulence you are talking about is BS. The rolling effect is BS (flow eddys). What happens with the inside surface of anything like an intake is it creates resistance drag at the cylinder wall. It produces a cone shape flow in the fluid (in this case, the air fuel mixture) where the center of the flow has the highest speed and the wall speed is effectively zero. The frictional layer between them is the turbulence that you speak of and it's not really turbulence, just friction. The thickness of this frictional layer is usually measured in microns, but it can affect the overall flow considerably. The frictional layer can be altered by the surface of the intake. The smoother the surface, the thinner the frictional layer. It all has to do with slowing the fluid down and the internal friction of the fluid itself (viscosity).

There is a thing called laminar flow and turbulent flow where you get large mixing and swirl eddys, but this does not occur normally in an intake. This would be more of a phenomenon that occurs at the tail end of an airplane where the air passing above and below come back together. Or it would be where there is a large change in the cylinder wall to generate the same effect. (similar to a probe in the mainstream flow)

To answer some questions, I know it has been posted somewhere else that polishing the intake runners to a mirror finish will only gain you a maximum of 5 hp or less. Opening the intake runners up (port match) to achieve a larger volume of flow will increase horsepower, but again, intake gains are minimal compared to other options. Bang for buck says to leave the intake go until last. The effects of an open intake would only be seen in a streetport or larger intake port motor. Batman is right when he says the velocity of the air flow slows down. With all else maintaining the same (IE no change in streetport of the engine, no change in the intake air filter, etc), the speed of the intake charge slows down. Same volume of air pushed through a slightly larger tube generates a slower flow. The plus side to this is that the larger tube generates less overall sidewall friction at the same time. You might think: well the larger diameter has more surface, so the friction is increased. Yes, but you also have to remember that the area increases in an exponential function, so the overall friction based on flow decreases giving a more efficient flow.

If you honestly think that the turbulent flow is your ticket, go get one of those SpiralMax inserts and put in your car.

Don't get me wrong, when you are talking about a carburetted car, there is some validity to churning the intake mixture because the fuel is just dumped in and you will get the problems you are describing. But with the technology of fuel injection, the injector atomizes the fuel very well and there is little improvement by churning the air flow. Any gains in atomization would be lost with the restrictive flow created.

With this said, $800 to gain a few Hp is a bit much, but it is not our money to spend. For the same amount, you could gain much more in different areas of the car. Heck, I know that just changing the timing will lead to a 5 Hp difference. Also, if the car has had all other modifications completed to maximum gain, then the intake runners would be the next logical area.

Quote: With all the money RX7 owners spend on performance items, if someone developed a superior intake manifold, they'd have a big seller.

The reason this has not happened in 10 years is because there is very little power to gain by doing this. Why waste the money? (Again, unless you have a ported motor and such) You can see there are a thousand different companies selling exhaust systems at a steep price because if you take the restriction out, you get more power very easily. Quick gains is where the market is, not in high priced small gains.

Good luck
Tim

tekno62

tek

SanJoRX7

Jet Hot coating, on the other hand, might have some serious benefits. By coating all reasonable parts in the intake/exhaust path, I would guess that underhood heat would be significantly reduced, presumably meaning that there would be 1) less chance of overheating, due to less chance of heatsoak, and 2) overall better performance of all of the cooling components (though, the thought has crossed my mind that they would be more effective at higher temps, but someone, please confirm).

DaedelGT

SPO is right. I witnessed a talk about high speed air collection techniques yesterday and one of the main things they had to overcome were wall effects. The heavier molecules would stick to the wall and would skew the results greatly, so they came up with a new channel design that introduced some turbulance at the walls to decrease these wall effects. Mind you, I'm talking about some miniscule amount of turbulence, but they were collecting at .7 mach.

BATMAN

It's BATMAN, not Batman or anything else

I might smooth out the inside of the LIM.

My beliefs are confirmed that there is a formula to the respective mods, such as turbo size, CFMs and boost being applied, to the ROIs with respect to this topic at hand.

Opening up the LIM and UIM probably makes sense when one is boosting at 1 bar of boost or greater and/or if the turbos create greater CFMs which is the case with most single turbo conversions and even Twins like BNRs..........