Intake port shape on heavily boosted engine, 60lbs+ 1

[Alkyhauler]

I just joined this very interesting forum and this is my first post.
I am designing a billet alum. cylinder head for an inline six Deutz engine(actually six individual heads). The engine will run on Methanol instead of Diesel and it will run with about 60-90 lbs of boost,maybe higher. It will either have two, large single staged turbos or 3 turbos (2 feeding into one) twin staged, both applications intercooled.

This is a 2-valve head as the rules dont allow for 4 valves, or even hemi style heads....valves must be parallel with one another, but can be canted up to 15 degrees. Currently I have it designed by having both Int. and Exh. canted 15 deg.

RPM range is 6500-8000, bore is 5.5 inches and plan on using an almost 3" intake valve. Intake port flow shoud be around 650 CFM. Currently I am think about using round ports on both intake and exh. Intakes to taper about 3 deg, exhaust about 5-7 deg. I thought that a round port would produce better flow with less friction, but am not so sure any more. Perhaps with running large amounts of boost it doesnt matter as much, perhaps more? I have the ports as steep as I can get them and still be able to get valves that length. With the ports at 15 deg. the intake port actually comes through the top of the head, but port location isnt a problem for this application. I am looking for feedback on port shape regarding this kind of manifold pressure and anything else that comes to mind with this scenairo.

Please feel free to criticize as I want to come up with the best design possible....I have a lot more questions, but one at a time.

 

[kenre]

Before getting too deep into cylinder head design, i would be more worried about keeping the bottom end together at your planned RPM. Max rpm as a diesel would be what 2500? measure your stroke and calculate the piston speed.

Ken

 

[Warpspeed]

Ken is right, but the engine could be significantly destroked.

A three inch intake valve is a bit of a worry from the weight (inertia) aspect at those Rpm.

 

[thundair]

With boost your biggest problem (as far as head design) is to exhaust everything. See thread on "valve ratio".

You will need to intercool the charge to be able to pack in the density.

Also look at your wall thickness and do some dynamic pressure calcs for the chamber area.
This is a big project that could go bad if something is overlooked.

Regards

 

[thundair]

Sorry I just reread your statement about

"both applications intercooled"

 

[Alkyhauler]

Thanks for all the replies so far...It is really appreciated!

The bottom end has been proven already, as a fellow tractor puller has run his at 6500 to 8000 rpm's for several years. He is using billet alum. con. rods, Arias pistons, light weight pins etc. The valves are fairly heavy, but titanium is used in the valve train where possible. The rockers are made from billet alum. and have been reworked several times to withstand the inertia from the weight of the valves.

The block/crank case has 7 mains using a twin counter weighted crankshaft. The main journals on the crank are approx. 4", but does require almost 300 psi to keep the bearings in it with such a large main journal at high rpm's. There is also a 2" alum. girdle between the block

Since we will be running a smaller cubic inch motor (504 is the limit, because we run a different class) compared to his at 650, we will have a shorter stroke motor (approx. 3.5625).

I realize that the rod to stroke ratio will not be considered ideal, but I know of a couple guys that are the same or worse, and are some of the top runners in our class.

This engine was originally air cooled, and we are eliminating the jugs and replacing it with a solid alum. piece that has been bored and fitted with sleeves. This will actually help strengthen the block and we are considering making this shorter than stock, so we can use a slightly shorter rod if needed.

This is a little background on the lower end, and I hope this helps. If you have any questions please feel free to ask....

 

[ivanheow]

make the port round and taper at less than 7 degrees down to .9 of valve dia just before valve and flare gently out into the seat ,straighter the flow to the back of the valve ,the more a tulip valve back may pay off use a flow bench ,read the superflow pamphlet on port design .robert.oh ,and use a bog off strong valve spring,youv got a 3 inch valves area with 60 psi on the back of it trying to keep it open.

 

[kenre]

Alky, sounds like you have done your homework! impressive.
With a 3 inch valve make sure you dont have any shrouding that could restrict the flow into the cylinder.

Ken

 

[Landmark]

Ivanheow - and alkyhauler
Normally boost around 60-90 psi reqires a backpressure in the exhaust in comparable size.
So the pressure in the cylinder will never be much less than the backpressure, that is net difference across valve will be less important at spring calculations. Or what?
Regards Chr

 

[ivanheow]

chr. if you achieve the same pressure or more in the cylinder ,as you do in the port before the valve ,then you are doing a remarkable job of porting ,i think youl find that there will be situations prob just as the valve is opening, shutting ,when the cyl is at a lower pressure than the port .specially at the high rpm.robert.

 

[RGRv6guy]

Ivanhoew, I'd like to see that pamphlet on Superflow Port Design, please. Thanks!

 

[Alkyhauler]

Ivanhoew....I would also like to take a peak at your Superflow Port Design pamphlet...I would really appreciate it!

Thank You, for yours and everyones input!

Dan

 

[ivanheow]

if you give superflow s sales man a call in your area youll prob get one free .regards robert.

 

[ivanheow]

sorry boys ,i have no scanner at mo. if you see your local superflow chap they give them out as advertising info ,,or they used to ,try that .
regards robert.