"Hedifolds" the good, bad, and ugly?

[NewbVetteGuy]

I'm curious about the thoughts on cylinder heads with integrated/ partially integrated exhaust manifolds like the Supra variant of the BMW B58 engines.

What are the pros / cons of the hedifold design? Are they here to stay?
-If they're so great, why did BMW not use them in their own performance cars with the newest 383 HP TU1 Update to the B58 and leave them relegated just to the Supras?


Adam

[BLSTIC]

They are fantastic for warmup emissions. Not having a huge external manifold saves an awful lot of heat dissipation area and the volume between the exhaust valve and the cat converter is smaller.

The volume between exhaust valve and turbine is also much reduced, this would likely improve response. I don't like the flow implications of it though.

That said, I've got a 6 cylinder Subaru project upcoming and the simple manifold design is a factor in choosing the early, less powerful, single port design. My manifolds will be two flanges and a reducing cone. No way I could mount the turbos that high with a multi-port head.

[midnightbluS10]

Isn't that the same thing GM has had on the 3.6L V6 in Buicks, Chevy's, and Caddy's since like 2012 or so?

[NewbVetteGuy]

They are fantastic for warmup emissions. Not having a huge external manifold saves an awful lot of heat dissipation area and the volume between the exhaust valve and the cat converter is smaller.

The volume between exhaust valve and turbine is also much reduced, this would likely improve response. I don't like the flow implications of it though.

That said, I've got a 6 cylinder Subaru project upcoming and the simple manifold design is a factor in choosing the early, less powerful, single port design. My manifolds will be two flanges and a reducing cone. No way I could mount the turbos that high with a multi-port head.

What's wrong with the flow implications? -Seems like it makes it very hard for people to screwup by choosing a low-velocity, over-sized header where it matters most (right after the exhaust port and for the first several inches); with a straight 6 like the B58 it also keeps the pulses separated properly as you don't have more than 1 cylinder contending for the merge point at a time -seems perfect for twin scroll or twin turbo.

Do you mean the implications of not being able to easily improve exhaust flow? (This is an application where a super simple "Dumb" exhaust port job like via extrude honing would make sense, right?) -But you could just get a new exhaust cam with more duration then, right?


Adam

[BLSTIC]

What's wrong with the flow implications? -Seems like it makes it very hard for people to screwup by choosing a low-velocity, over-sized header where it matters most (right after the exhaust port and for the first several inches); with a straight 6 like the B58 it also keeps the pulses separated properly as you don't have more than 1 cylinder contending for the merge point at a time -seems perfect for twin scroll or twin turbo.

Do you mean the implications of not being able to easily improve exhaust flow? (This is an application where a super simple "Dumb" exhaust port job like via extrude honing would make sense, right?) -But you could just get a new exhaust cam with more duration then, right?


Adam

I can't imagine there being much room inside the head for nicely curved bends and collectors. If you were building an all out horsepower engine this would be important, the single port makes individual cylinder a/f tuning difficult as well. I can't comment on cam duration, but with the EZ30 you definitely have different exhaust flow for each cylinder, so it's a concern.

However, for my purposes where I value response and simple fabrication over power, and it's been proven the head can make power enough anyway, none of that actually matters. I'd wager that's the case for just about any turbocharged street car. I mean the vast majority of turbo cars on the road have a log manifold with short runners (or variation of), so most people are throwing the individual port advantage out the window anyway.

[Circlotron]

I can't stop wondering how much extra heat must be dumped into the coolant by having the exhaust manifold effectively surrounded by water. Kinda like Ford flatheads with the exhaust port going across the full width of the bank.

[Kevin Johnson]

I can't stop wondering how much extra heat must be dumped into the coolant by having the exhaust manifold effectively surrounded by water. Kinda like Ford flatheads with the exhaust port going across the full width of the bank.

For an OEM that is often a plus as it quickly warms up the engine for low emissions. When that engineering team is happy the cooling system is probably someone else's problem.

[JodyB]

Economics. That is all. Will the head warp on the ex side? Yes. Within warranty? Prolly not.

[modok]

Makes good sense on a v6 IMO

yes there is significantly more damage if the head is overheated. that's a little depressing for somebody in the rebuilding field.
but, there are MANY engines on the road like that right now and people like them just fine. If overheated, just have to buy a new one. Oh well.

[hoffman900]

Plenty of them racing in Formula and endurance sports cars / prototype circles (Mazda, Honda, etc). Mazda has had some problems, but I think they have sorted them out.

[dfarr67]

My Honda 2.4L has that- great packaging if you want to turbo. At 200hp- I don't think output is affected at this level.

[hoffman900]

My Honda 2.4L has that- great packaging if you want to turbo. At 200hp- I don't think output is affected at this level.

The US Formula 3 engines make 270 NA from the 2L version. They are not hand grenade engines either at that power level.

Anyone remember this thread?
viewtopic.php?t=8305

[Ken_Parkman]

I think the heat into the cooling system is very good in a cold climate areas with todays high efficiency tiny engines. It seems to be a problem having sufficient heat rejection to the cooling system to keep the interior of the car warm enough, and to keep the windows clear. I regularly travel through a really cold climate in winter and it's a problem. I once saw a guy in a Prius scraping ice from the inside of his windshield!

The bad old days they had too much heat rejection, now not enough.

[ptuomov]

Great idea with high unit volume, not so with low unit volume.