radius seats on intake

[lasse]

This topic is really interesting. Here is many experienced engine builders having different experiences with very different engines, but does anyone have theories why? I really like to hear some theories why some VJ does and doesn't work in some engine combinations. Does anyone have some data about airflow, reversion airflow and fuel behavior (also droplet size should be considered) between various VJ configurations? Does anyone have done some CFD about this? I know simulation is simulation, but sometimes it can clear up some things.

[LotusElise]

A lot of talking here but no visual proven results .

EA113 head.jpg

This is a flow bench result of a EA113 head (VW Golf, GTI, 2-Liter Turbo, TFSI) at 28" water column and standard conditions. It's a 4-valve head (34/28 mm) which need some extra boost for 22 bar of BMEP compared an PFI port of the 90ies+ (Honda H-, B-, F- and K-series, Toyota 2ZZ-GE, BMW S14, ...), which flows much better. Concluding it's a cost effizient, low quality design for an boosted direct injection engine.

I won't tell much about the seat design, just the 3-angled seat design is simple but not badly efficient 30°-45°-70° 6 mm deep below valve seat-cut and the radiused has a two-radius-two angle design. I have no back to back test regarding power but for the flow bench result. Here you can see the radii-cut benefits flow-wise around scavenging phase and a bit on the high lift side.

The fully ported intake flows over 300 scfm@13.5 mm (28" water column) on the stock throat size, developed for an 1200 hp boosted 2-Liter-application, where scavenging phase pretty important. Here the radius cut will help, as well as it will for the I4-, V8 and V10-NA applications. As you know, if scavenging passed by badly utilized, there will be no power left on a lazy accelerated air column.

[LotusElise]

This topic is really interesting. Here is many experienced engine builders having different experiences with very different engines, but does anyone have theories why? I really like to hear some theories why some VJ does and doesn't work in some engine combinations. Does anyone have some data about airflow, reversion airflow and fuel behavior (also droplet size should be considered) between various VJ configurations? Does anyone have done some CFD about this? I know simulation is simulation, but sometimes it can clear up some things.

As Larry mentioned, the atomization has an supporter effect. The better the fuel is homogenized with the fast flowing air the less dependency on the valve cut you will see. Once a lot of fuel sticks on the wall and get released and pushed by the fast flowing air the homogenization is badly and a lot of fuel utilization depends on what happens in the bowl section. Radiused cuts have the tendency to let fuel to stick longer to the wall and attaches to it even around the seat contour better. That means fuel was separated, fuel is separated and fuel will be separated after spark ignition has happend.

A fast combustion need to have the fuel-air in a certain range of homogenization, so that oxygen finds the way to a vaporized hydrocarbon to do it's thingy with the temperature driven oxidation. The more fuel is separated the later and the less fuel will find it's oxygen to utilize further heat and therefore pressure to push that piston down the road to transfer it to torque. The sharper and more angled the edge the easier the pushed by shear force film and droplet will separate from the port wall around the valve seat and find the way to the liner wall or partly into the air by vaporization.

A lot of head specialist, I think Mr. Mondello was one of the first, who do wet flow bench investigations, introduced on their ports so called fuel ramps to help huge agglomerations of fuel to take off the wall after passing that specific ramp. This was often done with much better power results over the revving range along with a few cfm less. Less of this can be found today, most wet flow testing is done with huuuuge 2-valve heads, which have naturally a lot of more fuel to stick on the port wall then smaller ports (diameter-wise).

So far my hypothesis to that.

[Fusion Works]

I heard some comment about the radius VJ outflowing everything on the bench but not outrunning a regular angled VJ on track and then re-read this thread today. I wonder if a modern direct injection engine could use a radius VJ on the intake and see some improvements. Obviously no fuel cross the intake port so the argument for "chopping up the fuel" goes out the window.

[cwodgers]

My head porter radiused the intake and exhaust seats. It appears to perform much better than expected as it is a street/strip 400sbc, AFR195 heads, comp cams xe292R cam, 10.8-1 compression. Dynoed at 602hp 6400 rpm, Best 1/4 10.49 @128.25 at DA5300'. The car with me in it is 3250 and has a powerglide. The Wallace calculators suggest over 630hp corrected to run that at 5300' denisty altitude. The cam has 110 LSA and it 106-107 LSA would be better for maximum performance. Im curious if the low life flow benefit from the radiused intake is helping with the suboptimal cam.

[Tom68]

According to Darin Morgan radiused seats flow more.

Radiused exhaust seats flow more and increase power.

Radiused intake seats flow more and lose power.

That's for wet flow engines at least.

[Bigchief632]

To sum up the thread, the guys that use radius seats on the intake side, Larry Widmer, and LotusElise, note those are 4 valve, fuel injected engines. The guys who say distinct angles make more power from their testing, including mine, we did a test that took a few days, left engine on the dyno, pulled the heads, changed the valve job, started with a radius form under the seat first, then pull heads apart, and I used single angle blades, started with a 58, and a 70, then a 62 and a 75 on a 45 seat and 38 top cut, to change the radius to angles, these were Ford Super cobra Jet Ford motorsports heads, in the 950hp range, the seat and top cut never changed, meaning, the original intake seat and top cut were never altered, installed heights, seat depths, short turn depths, chamber blends, etc stayed the same. The conclusion was it was a big waste of time. There was some gains from the multiple angles, and it liked the 62/75 under the 38/45 the best. It wasn't earth shattering, some tq, 6-8 ftlbs, not a lot of hp gain, and it improved the bsfc numbers, and wanted a little leaner jetting to make a touch more power, hence the lower bsfc's. Definitive enough to use multiple angles though. Not to say there could be other applications that could possibly like a radius intake seat. Anyhow, the sharp angle crowd, are talking about mostly 2v domestic type engines. The 4v import stuff, the intake runners are usually quite short, with the injector much closer to the valves. I've also seen heads with down nozzle style fuel injectors, where the injector comes in from the back side of the intake bowl from the exhaust side, such as a sprint car type head, that had radius intake seats. Brodix used to do all radius seats, or at least a lot of them were for while, then stopped doing it. I've had heads come through from Kasse, Rheere and Morrison, Foltz, etc, seen heads from BES etc, all multi angles. Never seen a head from Dart with a radius intake seat, or any of the other head manufacturers, obviously if there was something there, they would do it.

This thread started pre direct injection engines, and those can run a radius intake seat, as do the high performance diesels I've worked on. With that said, i've had heads come in that had radius intake seats, that ran good, when I redo them, I cut my multiple angle seats on them, and they run jus as good or better after. Tom's summary above also is spot on for most stuff, there is always exceptions obviously.

[Bigchief632]

The other thing to note, this thread started 14 years ago. The general consensus hasn't changed. Multi angles on 2v type heads, and radius seats on 4v import or domestic type heads, and a radius seat will work well on a direct injected anything.

[Erland Cox]

I made a turbo 2.3 liter Volvo engine for a road racing Volvo.
It won 2 classes in 2020 and then their dyno guy called me next year.
He had tested the engine I built to 675 hp and it was torque limited to 750Nm:s to save the block at 1,966 bars of boost.
A little under 3 bars absolute.
2021 the engine only gave 530 hp whatever he did,
I had heard nothing from the owners so I expected the engine to be as delivered and as they had swapped the engine
to another car I looked at the exhaust system first.
By changing the exhaust system from a 45 degree cone from turbo to 3,5" to a 7 degree included taper power was up to 600 hp.
Still 75 hp missing so I called the owners and asked if they had done something to the engine.
While mounting dry sump on the car the cambelt had broken and the valves had bent.
So they sent the head to a local guy who cut radius seats in my head that had 85-75-60-45-35 angles and lost 75 hp.
This was an ethanol fueled car and the power loss was from plug wetting because of the radius intake seats.
I just asked them why the local guy hadn´t built the whole engine from the beginning?

Erland

[Tom68]

Darin Morgan says in that 3hr interview to never send your heads to anyone other than the guy that ported them for you.

[digger]

You dont need need every single angle discreet to shear the fuel IMO at least 1 on valve and 1 on the seat ought to do it provided they are sharp/crisply cut

[Erland Cox]

It is more critical with alcohol fuels than with gasoline but I would never use a radius seat on the intake.

Erland