XelderX's Intake Porting
- Thread starter xelderx
- Start date
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- 2002 BJFW, 2007 BK3P, 1979 SA22C, 2005 BK3P
kooldino has some good shape spare heads
oh yea!gone_fishin
Member
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- One of a Kind '99
xelderx said:
Hey xelderx, wish I would have seen this thread earlier. I used to extrude hone port and polish heads and manifolds at a hot rod shop, and have done a number for proteges. I guess you're already done, but looking at the initial pictures of how much you planned on extruding from the intake manifold outlet ports, I think that may have been entirely too much-- on the order of twice what you'd want to (without being conservative). On a side note, I guess things turned out well? Anyway, I'm sure you already know these things, but this is what I've learned over the years from porting:
Expanding the diameter of the intake manifold outlet ports beyond the diamter of the head inlet ports will cause the air to dam at the wall that's been created-- this causes eddy's and disrupts the objective laminar flow to the head, which can absolutely negate any gains you might have received from expanding the port diamter, if not worsen the flow path of the unmodified manifold. The ideal situation would obviously be a port matched manifold and head where all of the coinjoining surfaces between the manifold and the head are completely flush. If you can't port match for whatever reason, it's actually better to err on the side of conservativism with an intake manifold port of a lesser diamter than the head port itself.
Also, I'm sure you know this also, but for those that don't, for the same volume of air, air velocity to the valves actually increases with decreasing path diamter, and decreases (significantly) with increasing path diamter. A hugely increased diamter may actually hinder performance due to lessening the velocity of the intake charge-- this is especially applicable to N/A applications. Porting is about finding a unique balance between increased diameter and maximum velocity-- this is where a flow bench comes in. The balance is slightly different for every manifold and head. Porting is often times counterintuitive. There's a common misconception that sharp bends and corners are bad-- and in many cases they are. However, there's almost an equal ammount of cases where they serve to actually maintain the air velocity in compensation for a wider path diameter somewhere else. Someone mentioned it, but porting is all about the small things.
In my experience, I would port an intake manifold without a flow bench so long as it's port matched. However, porting a head without a flow bench and the proper equipment is like having sex with a blind-fold and ear plugs-- you might end up in the right place by some stroke of luck, but you'll have absolutely no idea how you got there. IMO it's asking for a big disappointment and possible disaster-- especially after the ammount of work, time, and effort porting takes. Not to mention the ammount of work involved in replacing a head.
Wow good info.
Def one of those things that make sense once u think about it.
(stooges)
I used the gasket to mark the mani with a permanent marker before grinding.
(bike)
This also supports my feelings that the 626 mani with single runners and no VICS/VTCS will show gains for me even while N/A.
Now if I could just solve the injectors and fuel rail issues...(dunno)
Def one of those things that make sense once u think about it.
(stooges)
I used the gasket to mark the mani with a permanent marker before grinding.
(bike)
This also supports my feelings that the 626 mani with single runners and no VICS/VTCS will show gains for me even while N/A.
Now if I could just solve the injectors and fuel rail issues...(dunno)
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Yea...when I started this I had two spare heads. That meant I could completely screw up and still have a good head for the car. I saw what everyone else was doing with their porting and decided that was a step in the right direction. My problem is leaving well enough alone. I'm a tinkerer by nature and like doing things on my own and seeing just where things will go if you actually step over the "normal" line.gone_fishin said:
Actually mine is port matched and the MSP we are doing now will be the same, but your point is exactly right. The first order of business was to smooth out the airflow and any sudden change in port sizes is counter productive.
I have no doubt in my mind that my porting will show flaws on a flow bench. There is absolutely no science or engineering in it. I simply made the hole in the gasket as big as possible and went from there. I also have no doubt in my mind that my porting will show more gains than the stock head and probably one that has simply been gasket matched. I'm not claiming perfection at all, but I will claim improvement. We all know how anemic our motors are above 6,000 RPM. It has been proven that the problem is the head can't supply enough air. If just gasket matching is an improvement then why wouldn't a little bit further be a little more improvement as well. I know all about messing up the flow and velocity stuff. Honestly I've probably overstepped things a little bit, but somewhere between gasket matching and porting into the oil/water jacket there is a magic place that is optimum.
Don't worry. I know all about disappointment and replacing heads. I went through at least 10 cylinder head replacements in 2005 trying to sort out a few problems with stuff unrelated to my porting. My car has nothing special powerwise on it. Fidanza flywheel, UDP, CAI, 4-2-1 Header, Hiflow cat, MP3 ECU. That is it. Everything in the motor is bone stock...not even overbored. Aside from the porting everything in the head is bone stock. Show me another N/A Protege making 130whp on stock motor and stock ECU. You have to admit that whether I got there by sheer luck or not, I did something right. Once again I will state that there is probably even more to be gained by doing it the right way and possibly by doing it the right way with less porting, but I did it for free aside from my time.
Now lets talk about an F/I Protege. Don't have to worry about velocity as much since under boost you'll be shoving air in instead of sucking it in. I can't wait to get it bolted up on Barry's car with the T28.
Crazee D said:
The 626 mani would probably show peak gains, but I believe you would loose too much midrange to make it worthwhile. At least for me...racing I spend just as much time between 4,000-5,000rpm as I do above 6,000. I'm afraid I would loose all the power (my car makes peak torque, 130ish, at 4,000rpm) where I spend most of my time....pulling out of corners in the middle of the rev range.
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- 03' Mazda Protege 5
subbin
I just talked to Barry and he says the car is running great other than a multiple misfire code. He says that it is misfiring above 5,000 RPM under boost. We think he needs to reduce the gap on his sparkplugs as I believe the spark is getting blown out by the pressure. He said he was running about 15psi on the GT28.
I have the 626 manifold with no vics/vtcs and there is no power lose at all. There is actually a very noticable gain in midrange power where most n/a proteges get their power from. It almost feels like vtec now...without revving to 6k. I keep seeing these threads with people who have not tried this on an n/a protege, saying that theoretically it does not work so I figured I'd stop the presses. Anyways i'm using the Manifold Protege Garage sells. just pm me for any other info, but the other people I have spoken with this mod on an n/a have ALL spoken of at least some kind of noticable gains....so NO YOU WILL NOT LOSE POWER WITH A 626 MANIFOLD. ok...lol
djarkitek said:
Dyno it. I want to see the graph.
Ok...your not N/A nevermind. No one with an N/A car has dynoed it with the 626 manifold yet. I never said that you wouldn't gain anything. I just want to see what you are sacrificing. Believe me...there will be a loss somewhere.
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