Velocity port + boost

[S12 Drifter]

Velocity port is great for a N/A setup but has anyone velocity ported a boosted engine cylinder head and seen the results of velocity porting? I.E

I velocity ported my KA24DET gained 12.6hp down low or. i velocity ported my KA24DET and lost 12.6hp and powerband is wacky.

[PoorMans180SX]

I'm not sure what you mean by "velocity porting". Please explain.

[S12 Drifter]

instead of making a port bigger and DECREASING air velocity (bad thing you need to rev higher to make the same power) you make it smaller (take up dead space).

theres moto man and theres a few people who have actually done it on their own bikes and cars with good results.

Homework (http://mototuneusa.com/homework.htm)

I tried Motoman's porting... - General Dirt Bike Discussion - ThumperTalk (http://www.thumpertalk.com/topic/698335-i-tried-motomans-porting/)

Small port heads. - Nissan L6 Forum - HybridZ (http://forums.hybridz.org/topic/72851-small-port-heads/)

xfi rebuild smaller intake ports for mpg (http://geometroforum.com/topic/4915684/1/)

please take time to read up and add to the topic, i have not found anything in boosted application.

[PoorMans180SX]

I'd say that works with bikes because the intake ports are generally a lot larger than the intake valve diameter. On most car engines, including the KA, the intake runner is generally sized much more proportionally correct with the valves.

[S12 Drifter]

the RB20 intake valve is 30mm the intake port is 45mm wide just measured. I'm going to do this anyway regardless of whats said, but I wanted to know if anyone here has done a velocity port on a turbo engine.

[PoorMans180SX]

the RB20 intake valve is 30mm the intake port is 45mm wide just measured. I'm going to do this anyway regardless of whats said, but I wanted to know if anyone here has done a velocity port on a turbo engine.

It's a VOLUME thing, not just how big around it is. You can actually CC the intake runner/port. I highly doubt this "velocity port" is a good idea on an automotive engine, where they already tend to emphasize low-end torque. All you'll gain is a tiny bit of low-end torque and will pay at the top end, where the KA already suffers.

[Frank_Jaeger]

Velocity port is great for a N/A setup but has anyone velocity ported a boosted engine cylinder head and seen the results of velocity porting? I.E

I velocity ported my KA24DET gained 12.6hp down low or. i velocity ported my KA24DET and lost 12.6hp and powerband is wacky.
Try the stock S13 butterfly valves. As far as I'm aware, these do exactly what you're asking but variably.

[S12 Drifter]

I have a RB20DET the KA24DET was a example that was thrown out, should have said that.

as you know RB20's make torque but not down low.

[S12 Drifter]

It's a VOLUME thing, not just how big around it is. You can actually CC the intake runner/port. I highly doubt this "velocity port" is a good idea on an automotive engine, where they already tend to emphasize low-end torque. All you'll gain is a tiny bit of low-end torque and will pay at the top end, where the KA already suffers.

volume is important but if you have a 90mm piston which is creating a low pressure zone with a port thats say 50mm and you decrease to 38mm port area you increased air VELOCITY the air will quickly reach speeds of 300mph or more.

air has momentum so it takes time to stop air, because air takes time to stop a small port will fill the cylinder slowly at the start but as soon as the piston starts to cause a very big low pressure zone the air will rush and quickly fill the cylinder and it will continune to do so even when the piston is on it's way up because it takes more time to stop high velocity air vs a port with big volume.

This WORKS it's been done and had GREAT results for automotive engines, check out the thread on hybrid Z. I'm not asking if it works or not because it clearly works on naturally aspirated applications.

But again, no one has input on how this would work on a forced fed engine. I.E damn good theory or PERSONAL experience with this, I'll be picking up a cylinder head very soon for a RB20 to test this theory and see how it works on a boosted application where air is already being compressed and forced creating higher velocity then that of N/A but I fear it may be too much a restriction more then improve flow.

[PoorMans180SX]

You'd be far better off investing in a better twin-scroll turbo setup. Have fun though.

[S12 Drifter]

it's about having low end torque not spool up time, if i wanted spool up time i'd do a divided turbine housing with a dual ball bearing turbo, ceramic coated and heat wrapped exhaust manifold, turbine ceramic coated and heat wrapped.

torque is what makes horsepower.

the plan is to have a RB20 that is not a total dog to drive in the city. of course keeping the top mount throttle body.

[aga]

turbo cars are different. the NA are very dependant on intake velocity, and the air is moved just by the piston, so it matters a lot. on turbo engines, the air is SHOVED in, so its better to have big volume intakes, large cams etc. whats the meaning of gaining a little on the low, and when on boost the engine gets chocked?

[jr_ss]

It's counter productive on a boosted setup. If you want torque throw the baby 2L out the door and step up to the 2.5L...

[Croustibat]

it's about having low end torque not spool up time, if i wanted spool up time i'd do a divided turbine housing with a dual ball bearing turbo, ceramic coated and heat wrapped exhaust manifold, turbine ceramic coated and heat wrapped.

torque is what makes horsepower.

the plan is to have a RB20 that is not a total dog to drive in the city. of course keeping the top mount throttle body.

The RB20 is a crappy engine. Yes, even if it has "RB" in it. Whatever you do wont transform it in a great engine. By design it has no low end torque. Either deal with it, or if you cant and really want torque slap a big V8 in the car.

Ah yes, i forgot. These are not JDM tyte yo compliant. :picardfp:

[Kingtal0n]

I should not appear in this thread. Why? Because I've never tried a velocity port on anything. The same goes for everyone else that posted anything besides experience with dyno charts to back it.


On the other hand, we can make some generalizations without doing testing.

Do velocity ports (or anything custom / out of the ordinary for that matter) cost money? (can you fabricate your own for basically free and have unlimited time to screw around with them?) If NO then goto fuckit:
else goto Yes:

Yes (they cost money):
Do you actually need a velocity port? (If you are not sure, goto "Why do we install velocity ports:")
Is there already a proven alternative that does not require fabrication (i.e. greddy intake manifold some engines?)
Compare dollars:benefit ratio. The whole idea of any power related modification is to increase volumetric efficiency at some rpm without damaging the engine, period. That sums up every modification ever made for power, from cams to turbochargers. Turning the dial on the boost controller up 1-3psi will probably outweight the benefit of any velocity port tuning that is done- and it should be cheaper since turning a dial is free. <begin advice>My recommendation here is simply install the right turbocharger so that you can actually turn the dial up at that point and call it a day, as the cost associated with the additional maximum power is included with the compressor.
Also consider that no matter how good your velocity ports are, any additional power on a turbo engine needs to be supplied by the compressor anyways since it will only flow so much to begin with. Also, Keep it simple.</advice>


why do we install velocity ports:
google this. Also, no.


fuckit:
might as well make some and post up results then.
There may be some benefits to low-speed driving. It may improve off-boost throttle response and fuel economy and idle characteristics if done right.


exit sub

[PoorMans180SX]

.

torque is what makes horsepower.

the plan is to have a RB20 that is not a total dog to drive in the city. of course keeping the top mount throttle body.

You are too general in your statement sir, top-end torque makes horsepower. As torque falls off, so does power.

[S12 Drifter]

You are too general in your statement sir, top-end torque makes horsepower. As torque falls off, so does power.

if you dont need to revv to 8k+ why have to? if you can revv between 3-7,500 with a nice powerband why would you want anything higher?

[PoorMans180SX]

if you dont need to revv to 8k+ why have to? if you can revv between 3-7,500 with a nice powerband why would you want anything higher?

There is a balance to everything in an engine. If you want a powerband from 3-7500, then buy small cams and get a fast spooling turbo. There is no sense in permanently restricting the intake port. Torque and power are going to fall off HARD at the top end, especially if you have a stock intake manifold and small turbo already. The only way this might be effective in widening your powerband is if you have a large turbo and short runner intake manifold that are already biased towards top-end power. You then might gain back some low-end that you lost.

Like I said, a fast-spooling, twin-scroll turbo is far more effective in gaining you "area under the curve" than making the intake ports smaller. A twin-scroll HX35 would be awesome on an RB20, and give you the super-wide powerband you're after. Especially if you got some mild cams.

Just because it gives a butt dyno gain on anemic NA L28 engines doesn't mean it's a good idea for all engines.

[koukistylejdm]

this guy has weird projects ololol

[jr_ss]

He's just trying to polish a turd...

[S12 Drifter]

There is a balance to everything in an engine. If you want a powerband from 3-7500, then buy small cams and get a fast spooling turbo. There is no sense in permanently restricting the intake port. Torque and power are going to fall off HARD at the top end, especially if you have a stock intake manifold and small turbo already. The only way this might be effective in widening your powerband is if you have a large turbo and short runner intake manifold that are already biased towards top-end power. You then might gain back some low-end that you lost.

Like I said, a fast-spooling, twin-scroll turbo is far more effective in gaining you "area under the curve" than making the intake ports smaller. A twin-scroll HX35 would be awesome on an RB20, and give you the super-wide powerband you're after. Especially if you got some mild cams.

Just because it gives a butt dyno gain on anemic NA L28 engines doesn't mean it's a good idea for all engines.

yea dude a HX35 is too laggy they wont make full boost till 5000 rpms. I've seen a lot of videos of HX35's on RB20's and their too laggy. i need full boost by 3,500 rpms or so. I'm keeping the top mount intake manifold for more torque.

by nature L28's make lots and lots of torque as a matter of fact they make TOO much torque and end up breaking ringlands and transmissions. they are no where near anemic, as a matter infact most will put a KA/SR/VG/ to shame when built properly.

i choose the RB20 because I'm doing road racing with my car and sometimes torque can be more of a curse then a help. i wanna stay under 400foot pounds but over 400 hp. I got rid of the VG because oil pumps can't keep up and they usually get rod knock.

I think I'm keeping the stock ports but i want to make the throttle body a 56mm and make the intake runners longer then they already are. 90mm TB's are for ricers. Going to need a dual ball bearing turbo though.

[Def]

This "porting" method works primarily by raising the port floor and increasing the short side radius. Take a look at the cross-section of an F1 engine's head. The almost straight port is good for flow, and production cars typically have a much sharper radius for the short side which is the primary limiter of their flow besides basic work close to the valve sealing surface.

The reason making the port smaller works on bike engines is they have ports that are typically larger than a passenger car's engine that makes much more power than those small engines do. So of course you can raise the port floor up a bit and port it in other areas and get more total flow throughout most the powerband (except the very top). Most of that is the attention to detail a good porter is paying to it, not so much the fact that the port is just "smaller." Lower the roof of the port and the thing will lose a ton of power with the same port size.

[PoorMans180SX]

yea dude a HX35 is too laggy they wont make full boost till 5000 rpms. I've seen a lot of videos of HX35's on RB20's and their too laggy. i need full boost by 3,500 rpms or so. I'm keeping the top mount intake manifold for more torque.

.

First of all, what Def said above.

Secondly, I guarantee you no one has put a twin-scroll HX35 on an RB20. I have personally driven a 2.0 liter 4G63 with a twin-scroll HX35 that reaches a full 30psi by 3500rpm in fourth. It was an awesome street monster.

Lastly, an L28 IS anemic, I have never seen or driven or ridden in one that impressed me, especially for their displacement and weight.

[S14DB]

Is this some sort of an abortion of Swirl / Tumble Ports?

[thefro526]

Just out of curiosity, why not just spray down low? A small, appropriately timed shot, should give you all of the power down low that you'd ever need, and with the right controller, the transition between spray and boost could be essentially seamless.

Or - ditch the RB20 for something with more displacement?