531 Valve Seat sizing

[whilliam]

True! But remember the pressure is high at first part of the lift - meaning more massflow at this point than later on.
Also, should we tell somebody that wants the best engine to "sacrifice" 4.5% ?

Too much massflow early in blowdown can have their downsides also.

I do not know how you think or what explanation you have for this statement. I do know that everything is depending on timing AND massflow - this in turn means that higher massflow at an early state will be compensated by camtiming and this in turn helps us with the wider powerband (which is all i was after - not maximum peakpower only)

To Erland, I dynoed 619whp at 1.9bar with 36.5mm exhaustvalves.
I feel like the 38mm exhaust is a little too big for the rings in the head, thereby i grinded down the exhaustvalves to 36.5 and also gained some flow at the area nearest to the chamberwall.

A lot (if not nearly all) of this result is up to the turbo (at least with the engines that Erland talk about).....
I have seen examples of his result at 500+ Hp on B230 engine @ 1 Bar of boost - this means that 2 Bar should give us in the region of 750 Hp (why is it not like that?)
Answer is the turbochoice - with a turbo more suited for 750Hp @ 2 Bar it would have been the result.

[Kadett4wd]

You want speed

[whilliam]

Exactly And speed is from energy, energy at the exhaust is from pressure difference and the more "sudden" it can happen the more difference there is.

I want the supersonic speed to occur at the area between valve seat and stem, this is the only explanation i can think of that makes an engine insensible to static exhaust pressure. (this represents the "other side" to make a wide powerband on a turbo engine)

In the thread about "överljudshastighet" it is more on this topic.

[Kadett4wd]

Here we go again,, it never reaches above supersonic(as i´ve been learned), at least not in a way that is important if it ever does(small small small area in front of pulse, almost insignificant and can´t be calculated with).
It may increase speed in km/h above ~2472.85km/h(900c) as the front of the pulse compresses the media,(raises temperature) and by this allows for higher speed as it has pushed the mach1 speed further up in km/h, say 1100c allows for 2675.35km/h, but still under mach1.

[Samman88]

Thankyou all for your replies, they are all informative for me
Today I shaped a radius in some tungsten carbide and cut the valve seat inside diameters to 40.5mm and 33mm and cleaned up the inside of the port around the valve stem with the radius cutter at the same time to match the seat.

I will attempt to shape the chambers similar to your photos on topplocksverkstan Erland.

Is there much premature wear on the valve and seat from cutting down the valve guide flush to the roof of the port?

Swedish:
Tack alla för era svar, de är alla informativa för mig
Idag formade jag en radie i lite volframkarbid och klippte ventilsätets innerdiametrar till 40,5 mm och 33 mm och städade insidan av porten runt ventilspindeln med radiefräsen samtidigt för att matcha sätet.

Jag kommer att försöka forma kamrarna som liknar dina foton på topplocksverkstan Erland.

Är det mycket för tidigt slitage på ventilen och sätet från att kapa ned ventilstyrningen till taket på porten?

Screenshot_20210907-195459_Gallery.jpg[/attachment [attachment=0]Screenshot_20210907-195511_Gallery.jpg

[Pacman]

A lot (if not nearly all) of this result is up to the turbo (at least with the engines that Erland talk about).....
I have seen examples of his result at 500+ Hp on B230 engine @ 1 Bar of boost - this means that 2 Bar should give us in the region of 750 Hp (why is it not like that?)
Answer is the turbochoice - with a turbo more suited for 750Hp @ 2 Bar it would have been the result.

If I remember correctly it was about 720-something at 2,0bar. When do we see something you have built Whilliam?

[whilliam]

I never heard of that figure, what power for the 670Hp @ 1 Bar?
Whatever engine you have, let me build the turbo and enjoy the power - rest of the engine is not what i am occupied with (but i need all of the knowledge to calculate the turbos right)

[Erland Cox]

The engine I built I got the first raw mapping dyno numbers for at 1,96 bars and they were RWHP.
670 something. And torque was kept below 750Nm:s to make the engine stay together.
Tested by Borgs garage, also on this forum.
There is a guy training with me on Sturup with a really well built and fast turbo 940.
He has a small turbo, mild cam and maybe 350-400 hp and 500Nm:s.
His engine stayed together for 10 years but now it split a cylinder wall even with only 96mm bore.
So I wonder how true the torque readings of the 1000Nm red blocks are?

Erland

[Erland Cox]

Do not cut the intake valve guide down.
If you are running alcohol fuel you should change to bronze wale guides at least on the intake side.
Usually I sleeve the exhaust and put solid bronze on the intake.
When porting the exhaust do not raise the roof from the valve guide and out, only widen it.
Make the back wall an as long radius as possible towards the valve stem.
Widen the port under the short side radius to 33mm:s and blend the ported area of the port together with the exit.
Do not make the exit on the exhaust port bigger, you only have to port half way out.

Erland

[whilliam]

The 940 at Sturup, do you know if it had standard pistons (hypereutectic) or forged ones (aftermarket?)

[Erland Cox]

Nån Wiseco kolv och H profilstakar, vet ej om det är standardlängd men troligen.

Erland

[psa]

I checked a list from Mahle that had alloys noted, and from that list it appears as Volvo used the low silicon casting alloy and not the hypereutectic high silicon. Couldn't find any information on the B23ET pistons though.

[whilliam]

I must confess i do not know for sure, since people say that the standard pistons is so good i took it for granted that they where hypereutectic.
What i have heard is the word "silikonsmidda" almost as: silicon forged (but i know that is not correct)

Well, since the engine with broken liners had som aftermarket, we can not blame the OEM Volvopiston.

Maybe the design of the piston skirt could have had something to do with the problems?

[Pacman]

The OEM B23ET pistons were some stirdy pieces of metal!
One B23ET I had the valve siezed in the guide when open and the piston first hammered the plate off the shaft and then the plate danced around until it jammed the engine in an upright position. The piston didn't care less and tilted so the block liner cracked open instead. After taken apart I examined the piston and besides some scary marks on top it was still intact.

They don't make pistons like those any more!

[psa]

I believe both the casting alloys used by Mahle was developed by Rolls-Royce during WW2 for fighter aircrafts. I'm guessing many other brands use the same alloy as well, but that was what I found at the time. https://www.us.mahle.com/en/motorsports ... ston-sets/

Wiseco seems to make good pistons, but according to some sources their custom service is more of a miss than a hit, and they pretty much only use 2618 low silicon forging that's less suitable for street use.
It's best to stick to the usual big brands if shopping custom pistons from America (JE, Diamond, CP, Mahle and a few others).