dimpled intake/header (what's your thoughts/experience?)

[gtengr]

Dimples are a generally a bad idea unless you know exactly what you're trying to do and have the expertise to prove the concept. The dimples on a golf ball represent a nuanced situation and only reduce air drag for a certain range of Reynolds number values. It has no effect on a chip shot, and a golfing robot with superhuman strength would experience less air drag using a smooth golf ball. Also, a golf ball is an object in free stream flow where the objective is to reduce air drag, while the intake tract represents pipe flow, where increased surface roughness means more friction losses. You're trying to pump air through the cylinder head, not throw the cylinder head through the air.

A modern cylinder head should have good atomization and cylinder filling properties as that is paramount to making 100 hp/L type numbers. I think poor atomization is generally more of an issue with older fuel injection and carburetor systems or otherwise dumping a lot of fuel before the intake valve. I know the FA20 has port injectors too, but still.

IMO the most likely flow improvements from surface treatment is knowing how to implement a gentle spiral shape in the intake port. I'm not sure how well it works or exactly the shape to go for, but it's the only surface treatment I've seen that I could see having some beneficial fluid dynamics wizardry to it.

[Escobar89]

I feel that my English is lacking here and it's a bit difficult to build up correct sentences.
Here you have a picture of the "intake valves house" on the saab engine, that produced an estimate of 12-14 whp extra with the dimple technique.




Here is also a picture that is from a Swedish car magazine. The engine that is showing in the Pic is a NA V8 with the dimple technique as well.

[Lantanafrs2]

"Estimate of 12-14 whp"? I've heard that about intakes as well lol. Imo the more the cylinders the greater the actual gain from any port trickery but smaller percentage relative to original output.

[Lantanafrs2]

Imo once you figure in time, cost of gaskets, risk of mis assembly etc., better to just boost it.

[NoHaveMSG]

I was always taught by some engine builders in the MX world that texturing ports for improved atomization is extremely misunderstood and what they are really shooting for is the correct boundary layer effect for the port velocities at which they were trying to make power. Improved fuel atomization was just a by product.

[gtengr]

Originally Posted by Escobar89

I feel that my English is lacking here and it's a bit difficult to build up correct sentences.
Here you have a picture of the "intake valves house" on the saab engine, that produced an estimate of 12-14 whp extra with the dimple technique.
[img]https://thumb.ibb.co/kRanJe/FB_IMG_1538673857164.jpg[img]



Here is also a picture that is from a Swedish car magazine. The engine that is showing in the Pic is a NA V8 with the dimple technique as well.
[img]https://thumb.ibb.co/ifEQ4K/FB_IMG_1538695820926.jpg[img]

I understand what you're saying. How old is that cylinder head (Saab went out of business in 2012)? How good of a port was the intake port in the first place? I think the benefit is more likely due to the dimples improving a poor/basic design than it is a dimpled surface being outright superior to smooth.

The Maserati doesn't strike me as a methodical approach. Seems like the owner just fell in love with the concept and dimpled every surface in the intake tract. Dimpling the radius of the bellmouth on the intake runner seems especially disingenuous.

[Escobar89]

Yes, I get your point there. The saab engine is from a old standard that goes back in the earlier 80's actually, but is it really so, that Subaru actually has manufactured this engine so good that there is only minor or even none benefits by improving the engine parts? The reason you could find a lot of power by just modify or improve existing engine parts, is that the manufacturer isn't able to put the effort it needs to polish or porting everything. This was very badly described by me, but I hope you get my point though? To get an example here. My saab engine is stroked from 2.0L to 2.4L, and without the turbo I did successfully get it to peak at 245whp, and that is made from improving the existing parts in the engine. It almost feels that our original 200hp in our FA20's is quite poor when you set it to reference.

[Escobar89]

Worth to also mention is that 245whp was made on ordinary 93 Ron, you could easily improve these numbers by using E85 and with that as well increase the compression.

[humfrz]

Originally Posted by Captain Snooze

I've only had one dimpled header. I used to nearly faint. *sigh*



Attachment 171298

If they are doing it right, all cheeks are dimpled -

(if I remember right)


humfrz

[Lantanafrs2]

What type of dyno were you on when you saw 245 whp?

[Escobar89]

Originally Posted by Lantanafrs2

What type of dyno were you on when you saw 245 whp?

This was made for about 5-6 years ago, and for what is all worth I can't say anything other than I don't know anything more than we sat it to rolling dyno (hope this is the correct frase on English). I have some dyno graphs in a hard drive somewhere.
For a 2.4L allover tuned engine, I wouldn't say it is in anyway extreme. For example was Honda making 240hp in their 2.0L inline four S2000.

[churchx]

Engines of past were way less strangled by emission eco regulation. Even honda, that made best small inline-4 engines, gave up, and now has turbo-ed engine in it's type-R. For modern NA engines ours is among most efficient ones already.

[Lantanafrs2]

You're confusing crank and wheel horsepower. S2k doesn't make 240 whp stock. I don't buy "estimates"

[Escobar89]

Originally Posted by Lantanafrs2

You're confusing crank and wheel horsepower. S2k doesn't make 240 whp stock. I don't buy "estimates"

No, its only you that is confused now. I never wrote 240whp I wrote 240hp, which in first case describe the amount of power at the wheel, second case is 240hp and this describes the power at the crank.
I know for sure the difference between whp and hp.

And yes I shouldn't put the s2000 against my saab, it was not very hard to see that this could be misunderstooded. My idea was just to highlight the 240hp in the s2000, that this car could deliver much power with low cc and no FI.