-xlr8planet-

iTrader: (3)

First time I make it into someones signature!

I dont care about the reason

Paul Loatman

I agree the more info the better, all i have right now is a completely stock 12A and i haven't decided on what to do with it so the more **** i know about stuff the better.

Jon, take it easy, this is an internet forum, the things that people write don't always come out on the other end as it was intended to, no one should take it personally.

Siraniko

iTrader: (13)

I say keep it going. the only way to learn is from experience and from trial and error

Box_Man

I asked an engine builder as well, and he told me to go ahead, just make sure that you port the entire runner to avoid having a "Megaphone" type of deal going on in the runner. The reason I did it was because I had my entire intake apart, and was doing a vacuum nest delete, along with the shutter valve, plugging unneeded vacuum ports in the intake manifold, etc. Since I already had the die grinder and dremel out, and was using them on the manifold, it was most convienient. I like to get my **** done all at the same time, I don't like to take baby steps and revisit things.

So, instead of getting on my *** about armchair mechanics and go fast philosophers getting on my nerves, why don't you send me a stock intake manifold to compare, make videos, take pictures, and if I can find one, dyno the car?

DivinDriver

iTrader: (15)

Myself, I've always figured that there was a reason Mazda made the intermediate ports smaller than the (much longer) end ports.

After all, making them smaller costs more aluminum in the casting... and when you make a few hundred thousand of them, that difference adds up.

bliffle

Not at all. You learn more from studying and understanding the underlying theories. Any Trial and Error experience is half error to start with.

Guys who are reluctant to understand simple electricity, like Kirchoffs law for example, end up doing way too much work and spending too much money, whereas a little study and thinking would solve their problem.

blackdeath647

iTrader: (2)

i must agree and disagree, the only way to learn is through the scientific method, in which you do BOTH http://www.sciencebuddies.org/mentor...c_method.shtml

dj55b

iTrader: (2)

The way you listed is pretty much saying what bliffle said. But in either way ... maybe we should get carl or sterling to maybe do a dyno test for us all.

Scott1982

OH come on - no one bit at this? Trial and Error? Lawyer?

DivinDriver

iTrader: (15)

If find the very best way to learn is to understand the theory... and then learn through the applied errors of others.

feerocknok

I plan on pulling my mani to clean, smooth, and paint, but will wait till I hear some more opinions. Seems to be alot of interesting concepts, but I'm mostly curious to what the half-way point would result in.
Quick O/T, is the intake manifold gasket reusable?

7aull

iTrader: (2)

I can't bring any expertise to this interesting discussion - just some (interesting?) pix.
I sent off this 79 Mani to Carl last spring, and here is how HE ported it - doesn't appear he touched the engine-side, just the carb-side. Or if he DID work the engine side, its much more subtle. The fact he did it this way obviously has SOME merit since I think we all have high regard for his expertise. Maybe we can coax some comments from him?
And, unfortunately, I can't contribute any user-experience (yet) 'cause I haven't installed it in the car with the Sterling Nikki....
Stu Aull
80GS
Alaska

SerpentKing

I got my own projects to build, chief. Check eBay.

What grinds my gears is the how you dismiss the questions and theories of forum members who are actual builders, not "armchair mechanics". Armchair mechanics don't turn wrenches, it's possible we have some clue what we're doing. R-E-S-P-E-C-T.

Rx-7Doctor

iTrader: (13)

Keep it civil please guys. :-)

Siraniko

iTrader: (13)

aw come on everyone know what Im saying so "Don't quote me boy, I ain't said ****." -EZ E ..."

SerpentKing

Eddison has investors to pick up the tab for his mistakes. He also didn't have to work 50 hrs @ week, pay the bills, THEN come home and invent the lightbulb. And why shouldn't he go ***** out, he stood to make a fortune. We might make a few extra hp, if we're lucky.

Eddison was smart in that he brought in researchers to back him up. If you can accelerate your learning curve by talking to others, YOU SHOULD.

SerpentKing

OK, we should probably cool the banter before we get a potentially useful thread closed down. Shutting up now

TheRX7Project

iTrader: (3)

I am selling a stock manifold. DO IT!!!!

Siraniko

iTrader: (13)

And how do you think I learned. I aint no engineer nor I got the funds to support it. Everything is about patience and do not get discourage for failed attempts. That is life...try and try until you succeed...

Rogue_Wulff

Paul Yaw has done plenty of testing on these things, but he isn't always 100% correct. For instance, he stated on his website (last year, at least) that vacuum advance should be hooked to manifold vacuum. Manifold vacuum decreases as the throttle is opened (increasing the engine load), and therefore the timing would actually retard, just when it should be advancing.
Most experienced engine tuners know that vacuum advance needs to be hooked up to venturi vacuum, as the vacuum at the venturi increases as more air flows thru. This would advance the timing as the engine load is increased, which is what needs to occur.

I know this info is not relevent to the manifold porting, but it does prove that not everything found on the internet is correct, even on Yaw's website.
I haven't explored his website in about a year, so I don't know if that little piece of misiformation was ever corrected.

Now, back to the topic at hand. I have had several rotary engine builders tell me they always port match intakes to the engine. I have not, however, had any that could provide any proof that it helped or hurt performance. This could easily be done by simply dyno testing the same engine, with the intake mod as the only item changed. It is possible that port matching will really help the engine's performance. It is also possible that it will hurt performance. For that matter, it could help under some conditions, while hurting under other conditions. Testing is the way to determine what the outcome is.

REVHED

This whole post is one piece of misinformation.

Ignition vacuum advance is never hooked up to venturi vacuum. It's either hooked up to pure manifold vacuum or ported vacuum which is just above the throttle plate so it sees manifold vacuum as soon as the throttle is cracked open.

Your theory defies the laws of physics. As load increases the pressure inside the combustion chamber increases which helps the mixture burn quicker. This means you need less timing.

I can't find one source on the net that says to use venturi vacuum for ignition timing yet there are countless articles that support manifold or ported vacuum.

http://www.vetteclub.org/technicalti..._explained.pdf

REVHED

http://www.chevelles.com/forums/show...t=ignition+101

TIMING AND VACUUM ADVANCE 101

The most important concept to understand is that lean mixtures, such as at idle and steady highway cruise, take longer to burn than rich mixtures; idle in particular, as idle mixture is affected by exhaust gas dilution. This requires that lean mixtures have "the fire lit" earlier in the compression cycle (spark timing advanced), allowing more burn time so that peak cylinder pressure is reached just after TDC for peak efficiency and reduced exhaust gas temperature (wasted combustion energy). Rich mixtures, on the other hand, burn faster than lean mixtures, so they need to have "the fire lit" later in the compression cycle (spark timing retarded slightly) so maximum cylinder pressure is still achieved at the same point after TDC as with the lean mixture, for maximum efficiency.

The centrifugal advance system in a distributor advances spark timing purely as a function of engine rpm (irrespective of engine load or operating conditions), with the amount of advance and the rate at which it comes in determined by the weights and springs on top of the autocam mechanism. The amount of advance added by the distributor, combined with initial static timing, is "total timing" (i.e., the 34-36 degrees at high rpm that most SBC's like). Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero, and the vacuum advance drops out entirely; it has no part in the "total timing" equation.

At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not "ported" vacuum - more on that aberration later) is activated by the high manifold vacuum, and adds about 15 degrees of spark advance, on top of the initial static timing setting (i.e., if your static timing is at 10 degrees, at idle it's actually around 25 degrees with the vacuum advance connected). The same thing occurs at steady-state highway cruise; the mixture is lean, takes longer to burn, the load on the engine is low, the manifold vacuum is high, so the vacuum advance is again deployed, and if you had a timing light set up so you could see the balancer as you were going down the highway, you'd see about 50 degrees advance (10 degrees initial, 20-25 degrees from the centrifugal advance, and 15 degrees from the vacuum advance) at steady-state cruise (it only takes about 40 horsepower to cruise at 50mph).

When you accelerate, the mixture is instantly enriched (by the accelerator pump, power valve, etc.), burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can returns to zero, retarding the spark timing back to what is provided by the initial static timing plus the centrifugal advance provided by the distributor at that engine rpm; the vacuum advance doesn't come back into play until you back off the gas and manifold vacuum increases again as you return to steady-state cruise, when the mixture again becomes lean.

The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions. By today's terms, this was a relatively crude mechanical system, but it did a good job of optimizing engine efficiency, throttle response, fuel economy, and idle cooling, with absolutely ZERO effect on wide-open throttle performance, as vacuum advance is inoperative under wide-open throttle conditions. In modern cars with computerized engine controllers, all those sensors and the controller change both mixture and spark timing 50 to 100 times per second, and we don't even HAVE a distributor any more - it's all electronic.

karism

I have nothing more to add,than to quote Jeff.

I have done it myself ,and the results were as Yaw stated.It performed worse on low and high rpm situations.

Cheers

Karis

karism

EDIT!!

I have nothing more to add,than to quote Jeff.

*Edit*

Oh what the hell.Look at the brochure for a Ford SVT Contour.The intake manifold was Extrude honed.
Now as everyone knows,this means that you pump abrasive paste into the manifold,which smooths it,but allso enlarges it a wee bit.

They did not just port match the manifold to the head,but they changed the whole shape,size and how the smooth the manifold is on the inside.

Airflow is a very,very difficult to work with.Small changes make a big difference.Most of the time negative!


Cheers

Karis

REVHED

Reversion is not the only issue. Port matching the primaries causes the port to both expand and turn at the same time due to the sharp turn at the end of the runner. This is very bad for flow.