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Tech Spam thread - because 1/4" BSP gets 5 hand spans to the jiggawatt


Roman
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44 minutes ago, Testament said:

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Golf ball inlet port?
Yeah I dunno, anyone seen/heard of this? I'm thinking that's quite different a golf ball spins/rotates and does a higher speed for a while at least. Cool points for aesthetics though.

Race car paint has "orange peel" finish for the same reason, supposed to improve flow by disturbing the layer of air that "clings" to the surface.

Some discussion here

http://speed.academy/10-myths-of-cylinder-head-porting/

https://forums.mightycarmods.com/forum/technical/tech-talk/798217-porting-clearing-the-elephant-in-the-room-about-rough-vs-smooth-vs-dimples

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8 hours ago, locost_bryan said:

Race car paint has "orange peel" finish for the same reason, supposed to improve flow by disturbing the layer of air that "clings" to the surface.

Race car paint is orange peel because fast/cheap paint job

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I think the dimpled thing is bullshit, because the point of golfball dimples it is to reduce the flow seperation at the rear of the ball as the air flows around it. So less drag.
The only place on a port that I think you could get anything similar would be on the short side radius of a particularly gross port.
Or if you are reducing the boundary layer, then you're increasing the effective area of the port. 
So it would make a big port worse, but an undersized port potentially flow a smidge better.
But I'm sure I remember reading stuff about it being useless essentially.

Most of what I'm learning from @kprs fine work at Garage4AGE is how important seeming things do fuck all, and seemingly arbitrary things make a big difference! 
 

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18 minutes ago, Roman said:

I think the dimpled thing is bullshit, because the point of golfball dimples it is to reduce the flow seperation at the rear of the ball as the air flows around it. So less drag.

I just came here to say exactly that*.

Only other considerations might be something to do with turbulence and atomisation** but I wouldn't expect it to do anything positive for the flow rate.

* I have a pretty solid idea on this

**I don't know what I'm talking about on this

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Also saw that being done to the high performance ecotec 3.8 moo edition. 

But just to the plenum and not the runners. To trick the plenum into thinking its bigger than it is as above

 

Of course no data to back it up, but looks cool

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In terms of fuel atomization, if you've tried cold start tuning then you'll  know that the port shape or surface doesnt stop fuel from sticking to the port. 

When the motor is hot. You spray the fuel onto a hot port and hot valves while they are closed, then the heat vaporizes it back off the walls and you get a good air/fuel mix. 

When the motor (port) is cold, you have to add a bunch of extra fuel because so much of it pools to the walls and doesnt remix. 
If the boundary layer could affect this, then every single manufacturer would have dimpled ports just for sake of cold start emissions. Because cold start is a huge contributor to bad emissions.

(well, prior to direct injection at least I guess) 

When you've got carbs mounted really far from the port, then rough surface probably helps more to keep fuel off the walls, but what would help even more is just keeping the whole thing hot. 

Also people always talk about airspeed like it's fixed. At 1000rpm you've got 1/10th of the airspeed of 10,000rpm. 

At a cold idle you've got no airspeed (so port shape means fuck all) and no heat in the port and it's a fueling disaster regardless of what else is going on.

I guess point being that port shape changes dont affect all load and rpm ranges equally, and the times where you'd want to best increase fuel mixing is when dimples do nothing 

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on the subject of dimples......went to the Winternationals a few years back and did a tour of a few shops in the days leading up to the drags......one of them built engines for a top-tier V8 Supercars team.....engine was torn down in the clean room, dimples in the ports and chambers....just sayin'

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I gotta see numbers on a bit of paper tho. Cos they used to bolt a bit of metal inside the chamber of flathead to increase performance and I'm entirely sure all it did was increase preignition lol

 

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Pretty sure that one comes from the same guy who makes rings on the back of valves

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If the port shape/size is good it probably doesn't make it materially worse, so if some engine builder is all about it and builds everything else good you could easily have a positive bias result bias. i.e. it would have been a great motor without but you didnt test that.

pretty sure the next secret will be to paint the ports yellow because thats the fastest colour.

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Reminds me of that story where one of the F1 teams (or whatever) came up with a new front wing or front duct or something that made them go faster. 
Every time the car came into the pits, the team would throw covers over the rear of the car as a distraction
So everyone kept trying to peek under there and figure out what was different. But no one looked at the front 


Excuse me if this is an absolutely awful paraphrasing

 

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There's probably some optimal mid rpm/load point where the dimples actually make a difference. Probably not enough of a difference to be worthwhile on a 4K though.

If you're at the point of trying to trip turbulence in an intake port, your engine is probably already optimized as far as possible in all of the low hanging fruit areas

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Fuel stabilisers: snake oil or the real McCoy?

I have a car that has a 3/4 tank of bp98 and has only run a few times in the past 4 years, idled, driveway moving etc. And I wanna know if a good fuel stabiliser is worth it or should I just run injector cleaner as I plan on running it a bit more. Cheers 

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25 minutes ago, 87creepin said:

Fuel stabilisers: snake oil or the real McCoy?

I have a car that has a 3/4 tank of bp98 and has only run a few times in the past 4 years, idled, driveway moving etc. And I wanna know if a good fuel stabiliser is worth it or should I just run injector cleaner as I plan on running it a bit more. Cheers 

Drain the fuel out and replace it. It's 4 years old, trying to use it will just end up doing more harm than spending $40 on new fuel.

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Can i make my bigport head  have smaller ports, if i put  pimples instead of dimples in the ports ?

I'd try it but there is only so many times one can swap a 4age head, before going insane and thats coming up real fast.

Agree with what @Roman  says about the fuel sticking to the walls.   dimples only going to help when it doesn't need help.    one of my vids i done with camera looking down the port. the fuel all chills out in one of the mismatches where 2 parts of the intake runner joins.  soon as open throttle a decent amount.  the fuel gets pulled out and goes down the hole with the rest of it.   so dimples probably just give the fuel more places to chill out when airflow is low

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