2Lucky2tha7

iTrader: (3)

Since I have no air pump (the bracket broke), I wired the VDI open and I keep the auxillaries closed. My powerband really seems to come alive roughly around 4500-5000 and up to redline. It never tapers off. However, when I keep the auxillaries wired open, it's very hard to keep a real good idle on it and I have to rev it around 2000-2500 to get moving, or else I practically stall it out. It has almost no power up to about 5500-6000, then the power just seems to spike straight to redline and has a higher peak hp output of the 2 "settings", but is certainly not streetable. 2 entirely different powerbands. I have to keep the auxillaries shut because with them open, the car is just not streetable. Yes, I ported and rebuilt this motor myself, but I really wish that I didn't go so big on my ports. The primaries and secondaries are as big as I could possibly go (the leading edge of the side seals just barely have a surface to ride on), and I ported the auxillaries way too big. I used the pineapple racing inserts and then ported up and forward and made a nice smooth ramp, but unfortunately that ended up compromising the actual compression numbers when open. I learned this the hard way. As for the exhaust ports, they are wider, ported lower, and ported higher a good deal more than stock. Very noticeable. Unfortunately this porting setup creates a bit of overlap. I also have a cold air intake I made myself and I run a RB header and presilencer. No cats, no emissions, no powersteering.

My suggestion for a good streetable 6-port?
Personally I would instead have only ported down and out on the exhaust ports, and not up at all. (Some may disagree), and as for the auxillaries, just insert the pineapple racing inserts and possibly a "little" smoothing. I still would have made the primaries and secondaries the about the same size, maybe a bit smaller actually. My one mistake was a pretty dumb one, I admit. I ported forward on the primaries and secondaries towards the oil seals. I think I went forward like 2mm if I remember correctly. Maybe a little more, maybe a bit less. I made the mistake of thinking that the oil seal tracing left behind on the metal on the side housings was where the outside of the oil seal was riding, however, it's more towards the inside of the seal. So after the porting, I noticed that I could see the oil control o-ring a bit. Now my engine burns oil because it slowly gets injected into the chambers.
If I were to do it again? I would just use 4-port housings and do a large street port. Simplified and less hassle. Gets rid of the bulky intake manifolds and gives me the opportunity to throw a turbo on it later on. Unfortunately, you lose the VDI this way. The VDI makes a big difference on my engine when open.
Anyway, I guess I just felt like rambling because I wish I could have done it differently than I did.
Brian

rotarygod

iTrader: (1)

I agree entirely with your suggestion for a good streetport. WAY too many people have a bad habit of going as large as they can. Bigger is not always better. Smaller is better until you max it out. As large as possible is almost never a good idea on a street car, even if it is only a streetport and not a bridge or larger.

t-von

iTrader: (8)

What you should have done was left the primaries alone. The stock TB opens the butterflies to the primaries first then the secondary butterflies open later. You can go pretty big on the secondaries if the primaries are left alone. Your large porting of the primaries mainly killed your intake velocity in the lower rpm range. You need that velocity to properly fill the cumbustion chamber. Less velocity leaves less fuel/air to burn which in turn causes a smaller explosion on your power stoke. Smaller explosion means less force on the rotating e-shaft. This is how you lose torque on the bottom end. It's not about you going to big, it's about you opening too early with the primaries causing too much overlap. Why do you think 1/2 bridges still have decent bottom end?

GtoRx7

iTrader: (5)

I agree with T-von, but how large did you port the primaries and secondaries? Did you follow a template, like racing beats? It sounds like you are right on the porting to far up on the exhaust, as it effects down low power big time. I also agree with you to do a 4-port motor, I built a TII motor a couple years ago, and used TII S5 intake manifolds, and S5 n/a rotors, ported the primary and secondary to racing beats template. Ported up and down just a little on the exhaust. Used a Haltech E6x. It had torque everywhere, down low was acually ALOT more than a stock 6-port without sleeves, and ALMOST as much as a stock 6-port with sleeves. It was a total blast to drive. It sucks for you, but at least you helped others with your experiance! Best of luck in the future!

2Lucky2tha7

iTrader: (3)

From what I remember, I have the the opening timing of the primaries and secondaries as far back as I could possibly go,(pretty much "maxed" out). So the primaries look double the size from stock. As for the closing timing on the primaries, I think I went up like 4-5 millimeters from stock. As for the secondaries, it's kinda obvious because the auxillary port sits right above it. The closing "shape" of the auxillary ports is a "right angle" shape. (I should probably post a pic of this). Unfortunately I ported the auxillaries wayyy too far up. VERY late closing timing on these. Now, as for the exhaust ports, if I remember correctly, I ported upwards probably close to 5 millimeters. WAYYY too much for closing timing. So with the combination of alot of opening timing on the intake ports and alot of late closing timing on the exhaust ports. So I've got a bit too much overlap. Oh yeah, I didn't follow a template at all. I ended up making my own template after I ported the first set of ports.

Well one thing I can say is that with the auxillaries closed, the powerband above 4000 rpms feels great, but anywhere below that just sucks in my opinion.

t-von

iTrader: (8)

The next time you open your engine, swap out your center plate and you will be happy again I promise.

Bluem

bp on 6-ports have way too much overlap and power bads are way high for street even if you dont go to high on the timing

evelhalo

Hey,
Stock Gxl 87
Cold Air in mail
exhaust next week


My buddy is experianced at porting, but he works on big block american cars and 2jz's and shiaat so i want to know exactly what to tell him so dont srew up my block cause i cans afford to replace it

We have the tools, and im only going for a medium streetport(it has to be a reliable street car) But what should i port and where?

Should i only port the intake until i have some forced induction? should i do the aux ports? which direction do i need to go, or how far?

peejay

High overlap makes for midrange grunt at the expense of part-throttle driveability. The powerband is determined by intake closing and to a lesser extent exhaust opening.

As the original poster found, close the intake ports extremely late and you kill off the low end and midrange power. This is unrelated to the amount of overlap.

Nutshell:
If the intake ports closed earlier, the powerband would be shifted down the RPM range. If they also opened earlier for the same effective port open time, peak HP wouldn't be affected but since the closing time is earlier, lower end power isn't hurt so much. This increases overlap, the downside of which is that the engine makes less power below full throttle. In other words, it makes *more* power in the midrange, but *less* power at part throttle.

For extremely high overlap engines, exhaust and intake tuning become more sensitive. If your exhaust system isn't straight through, don't bother. Super low engine speeds where port velocity is poor also don't work so well... my 12APP was a laughable slug below 2000, but it felt stronger than any N/A *13B* I've ever driven above that.

RXDad

iTrader: (2)

I ported my S5 NA exhaust down about 9.5mm and out, my Aux port about 9mm up, my secondary port as close to the aux port as comfortable. I left my primary port alone.

I'm happy with the results. The engine seems to have lots of low end torque while running very good at the high end.

RXDad

t-von

iTrader: (8)

^ nice way to port!

GUITARJUNKIE28

close the aux ports that late and you're gonna need to build a manifold to take advantage of them. that closes later than the renesis!