Redneck porting job...

[T45]

Well since I'm waiting on parts and money to get the V8 back together I decided to grab my dremel and do a little porting work. I have read a lot about it and decided to give it a go. I have zero experience with porting so don't follow me until I get some dyno numbers up. I'm mainly focused on port matching and smoothing the airway rather than enlarging the port to maximum size. The factory did a fantastic job on the intake and heads as far as casting goes but it still has a few flaws that I wanted to take out.

My basic understanding is that the bigger the port, the slower the air velocity. I'm sure Nissan did it's homework and thought that the port size was big enough so I just took out the ridges and smoothed up things a bit. Some of the ports weren't round so I tried to make them as round as possible. I am also not worried about polishing because I have read conflicting articles that polishing doesn't help in an engine. I read that air gets lazy over smooth surfaces and also, fuel will puddle on a smooth surface like rain on a fresh wax job. So with that in mind I just cleaned up everything and left a 120 grit surface on it. In the pics it looks like a very rough and jagged surface but by touch it's baby smooth. The small ridges left by sanding will create enough turbulence to keep the air rolling on little air ball bearings. If it were smooth it would basically have a layer of stagnant air to slide over instead of roll over.

Some basic theories are like a golf ball. Without the dimples a golf ball wouldn't fly half as far. The dimples act as little air bearings to help reduce friction. I'm no aeronautical engineer so here's what I did and no matter if it helps or not, I think I will get my $20 bucks worth in dremel drums...

First was the exhaust manifold. The robot that welded them left an uneven, overhanging lip so I just burred it out and smoothed the radius. The factory tube manifolds will help me keep the torque that I'm after. I think making high flow headers wouldn't benefit my application so I just cleaned them up a bit to improve efficiency.

Before:

After:

Pic of lower intake runner before molestation. Notice how bad the holes are from the factory:

After with a better representation of a circle:

Lower runner from the top. Again the hole that's supposed to be a perfect circle is far from perfect:

After:

I put a little knife edge where the intake splits into the siamese head ports:

Looking through the injector port at the split before:

After:

Sorry for the pics but my camera doesn't take close up's well. I figure it if gives me 5 hp then it's worth it and it gave me something to do in my free time besides drinking beer. I still have the upper intake and heads to do. I wanted to get my feet wet on the runners first as they had a lot of meat to remove. The only thing I will do different is give the exhaust runners and combustion chambers a nice polish job. The reason for that is so carbon doesn't build up on them and create hot spots that can cause detonation.

[Q45tech]

One would normally use a flow bench to quantify each port [all 32 individually and by cylinder] as to flow and measure the reversion [backwards flow]................not so good to only think in flowin terms!

The engineers had to do tricks to make the engine kinda behave at 1500-3,000 rpm where most use was in a street lux car.

Lots of difference in a dyno queen and an engine which will be driven everyday on the street. A narrow high peak is useless except in a graph!

Can you imagine a Ferrari engine modified to make it functional with an automatic in a 4500 pound loaded car in summer traffic..........can't spill the saki smoothness.

[maxnix]

A high mirror polish will probably delay carbon build up on the part above the injector spray.

[T45]

One would normally use a flow bench to quantify each port [all 32 individually and by cylinder] as to flow and measure the reversion [backwards flow]................not so good to only think in flowin terms!

The engineers had to do tricks to make the engine kinda behave at 1500-3,000 rpm where most use was in a street lux car.

Lots of difference in a dyno queen and an engine which will be driven everyday on the street. A narrow high peak is useless except in a graph!

Can you imagine a Ferrari engine modified to make it functional with an automatic in a 4500 pound loaded car in summer traffic..........can't spill the saki smoothness.

I don't think I overdid it with my porting lines and the amount of material I removed. Just removed casting flaws, made the circle, that's supposed to be a circle, a circle, and everything else that this mass produced engine should have had.

What does a Ferrari have to do with the price of saki in Japan? It's not like I bolted on ITB's or a tunnel ram intake and lightened the crankshaft. It's just port matching. And as you can see from the pics, I think it needed it.

Why would carbon build up on the intake side of the engine? From the gas or the EGR? I'm removing the EGR system so the only issue is fuel which can be cleaned up with BG44K from time to time. Unless I'm missing something...

[Q45tech]

Normally the gasoline spray washes the reversion and egr and dirt from bad air filters away and into cylinder.

EGR is only flowing at steady cruise 1500-2800 rpm.

My point was the runner diameter, taper, head ports, and valve size are already too large for a street car.

Porting and polishing will only degrade performance until you exceed 4,000 rpm because you will be further slowing the air speed into engine.

Consider why the VVT reduces overlap and intake cam advance above 4600 rpm as the flow speed finally reaches enough to properly fill the cylinder.

Why not tulip the intake valves if you really want more air flow.

Having minor differences in flow between ports adds to the tumble and mixing as the 2 streams hit and combine coming out of the valves.

Have fun seems like a lots of hours say 4 per cylinder to gain so little?

[T45]

Well my main goal of this was to just match the ports. The factory holes that are drilled into the runners are way off from where they should be. When the runners were removed I could see the black marks on the head and the corresponding ones on the runners and almost all of the runners were not lined up to the head ports.

The gasket lays perfect on the head. The gasket lays off center of most runners. I am trying to align them to have a smooth flow into the head as the stock setup has the ports misaligned.

I do thank you for your wisdom and can see that you know a lot more about this than I do. But I don't think there is an engine designer out there that wants the ports off center by 1/8th of an inch or more. This is most of the extent of my venture into porting my engine. I hadn't planned on enlarging the ports in the head, just cleaning up the junk. I also don't have any plans for grinding valves and such. Like I said, I want the torque that this engine is designed for.

More airflow does not always mean less torque.

[maxnix]

My point was the runner diameter, taper, head ports, and valve size are already too large for a street car.

Porting and polishing will only degrade performance until you exceed 4,000 rpm because you will be further slowing the air speed into engine.

More airflow does not always mean less torque.

What Q45tech is saying is that with any further increases in port size, there is less velocity at lower rpm so you may get less cylinder filling due to intial inertia of the air column and thus less power, more likely to stumble. Maybe above 4K rpm you might get another 3 - 6 HP?

Removing EGR for street is not a great idea, but neither is it crippling unless you frequently cruise on the interstate or have emissions checked at 2500 rpm.


Modified by maxnix at 3:21 PM 5/3/2007

[Q45tech]

Or care about cruise MPG since egr reduces pumping losses [from an almost closed TB---necessary to keep rpms low].

10% egr mass [sum of Nitrogen+CO,+CO2] since most O2 has been consummed can improve 60 mph by >2 MPG.............a useful byproduct on Nox control.

10% less fuel because there is 10% less burnable air in the cylinder

[ScottJackson]

I'll take the other side and say, "good job". I don't think you'd noticeably hurt anything by smoothing it out like that. You probably gained a bit in the upper rpm power. As for the Ferrari engine thing, the VH45 is very similar to the modern Ferrari V8s. Give it another point of compression and bigger cams with more overlap along with a larger plenum, and it'd be one nasty, fun, high revving motor. Oh yes, and as was mentioned, the valve seats and cuts on the valve make a HUGE difference in flow, especially at low lifts. If you have the valves out, get the intake valves back cut (don't bother with the exhaust valves as it won't make much difference).

[db_autotek]

Wow there is some serious flaming going on.. I think you did great and was thinking of doing it myself, just to remove some of the casting imperfections. I did the same on my mazda and felt a little better throttle response from it. Nothing official though (dyno results), just that old fasioned seat-of-the-pants measurement.

[T45]

I can totally understand that enlarging port size will slow air speed. But the mis-alignment of intake runners to the head, blunt edges on the split, and un-round runner ports have deeper impact on airflow than enlarging the runner ports to match the head ports.

Also, on the exh manifold, the welds protruding into the passage can't have a positive affect on air velocity unless air flows better around 1/8 th inch obstructions in oval tubing.

I'm not concerned with EGR or highway mileage as not only does VA not have emissions.....but I'm rolling on 35's anyways so mileage went out the window a long time ago.

[T45]

Or care about cruise MPG since egr reduces pumping losses [from an almost closed TB---necessary to keep rpms low].

10% egr mass [sum of Nitrogen+CO,+CO2] since most O2 has been consummed can improve 60 mph by >2 MPG.............a useful byproduct on Nox control.

10% less fuel because there is 10% less burnable air in the cylinder

= 10% less power?

[StarPD]

Q45tech and maxnix are absolutely correct about "porting", and it goes without saying, "polishing". Even if done using a flow bench, actual performance in a given engine can produce characteristics that are in contravention of your goal.

That being said, the way I understood your post was that you restricted your work to port matching and casting cleanup. In the case of the Q, which has more than optimum port sizes I don't see it helping that terribly much, but I also don't see it hurting either. That is only if all you did was match ports and remove casting flash. Any more than that would be counterproductive.

[T45]

Looking down into the head the port actually tapers after leaving the intake runner just after the injector. It is my understanding that this area is where you want the maximum airspeed and not earlier on in the intake. These areas are very round with hardly any flash at all. I am leaving these areas alone because of so.

The NICO tuned ECU runs the rev limiter up to 7200 rpm's which would make the airspeed supersonic if I remember another thread correctly. At those speeds I think every little bit makes a difference.

I'm not saying anyone is wrong and I don't see any flaming going on. It's a nice debate and I am still learning a lot. I'm used to working on tugboats and the like. The current engine we are installing is a 4.3 liter diesel.....per cylinder x 8 cyl's. It's hard to adapt it to something like the VH. 10.2:1 compared to 80:1 CR.

[Q45tech]

4494/8= 561.75cc x1.204 [mg per cc] x 0.8 VE @7200= 541 millgrams of air in 10 milliseconds,

[darinz]

First was the exhaust manifold. The robot that welded them left an uneven, overhanging lip so I just burred it out and smoothed the radius. The factory tube manifolds will help me keep the torque that I'm after. I think making high flow headers wouldn't benefit my application so I just cleaned them up a bit to improve efficiency.

I've cut up a set of factory tube exhuast manifolds and getting rid of them can only be good. They look OK from the outside but internally they are terrible. The poit where the runners join is very very bad. The runners is flaired nicely and weld from the outside but on the inside there is a hole cut in the bigger tube. That hole is far smaller than the runner tube size ie there is at least a 10mm lip sticking in. Even making up a very basic log style manifold would be better. The standard manifolds are really bad.

[T45]

It seems that every time I have lost a race, wether on a bike or in a car, it has been to someone that has had their heads ported and polished. One would assume that this engine is just like the rest and has some small issues that need to be dealt with.

Next time you have a head off, run your finger down the intake and exhaust ports. There is a sharp lip at the port entry and at the exit of the exhaust ports. Lay a gasket on top and their is a couple mm's of uneven material that can be removed to smooth airflow and still maintain stock runner size.

I keep hearing how much time, money and thought went into the VH when it was engineered and how they "got it right the first time" and not to second guess millions of dollars on development and so on and so forth. Then I hear that the engineers made the ports and runners too big?

[sijoko]

It seems that every time I have lost a race, wether on a bike or in a car, it has been to someone that has had their heads ported and polished. One would assume that this engine is just like the rest and has some small issues that need to be dealt with.

Next time you have a head off, run your finger down the intake and exhaust ports. There is a sharp lip at the port entry and at the exit of the exhaust ports. Lay a gasket on top and their is a couple mm's of uneven material that can be removed to smooth airflow and still maintain stock runner size.

I keep hearing how much time, money and thought went into the VH when it was engineered and how they "got it right the first time" and not to second guess millions of dollars on development and so on and so forth. Then I hear that the engineers made the ports and runners too big?

Good job in cleaning up the production flaws. The VH is well designed but actual manufacturing will always introduce some bottlenecks. All you did was remove them a bit.

How thick are the welds on the exhaust manifolds? I'm building a turbo kit for my Q45 and am using modified stock manifolds. I want to clean up the welds around the flange area but don't want to weaken the manifolds. Do you have any other pictures of the flange area. Thanks.

- Siju

[T45]

I would estimate that after burring off the extra weld that there is about 3-4 mm of weld left. If you're concerned about strength you could always run a bead around the outside of the flange around the tube.