GregBBRD

How much air is required to fill each cylinder 100% at 7,000 rpms on a 6.5 Liter stroker engine?

6.5 Liters=396 cu.in.

49.5 cu.in. per cylinder.

7000 rpms=3500 complete combustion cycles per cylinder, so each cylinder will be filled 3,500 times per minute.

49.5 cu.in. x 3500 complete fillings=173,250 cubic inches of air required.

173,250 cubic inches=100.26 cubic feet

100.26 cubic feet of air are needed to fill each cylinder of a 6.5 liter engine running at 7,000 rpms....assuming 100% volumetric efficiency.

GregBBRD

That's correct. My mistake.

slate blue

On a coffee break here, my understanding of the flow through the heads as I briefly mentioned in the previous post was that 28" is used because it is relatively inexpensive to construct a bench that can pull that vacuum but it pulls or simulates the pull of only 50% of what a live engine would do.

In relation to flow figures and actual engine demand, again you need to take into account the above but also there is time area that the intake system has to deliver that air as such it needs to supply that air within the camshaft profile. This means it needs a high capability to deliver it. The speed of the air is also important and in the link I provided earlier another one of Blair's papers it does concur with 0.5 Mach, that was a Moto GP engine which are extremely powerful for their size but one thing I really want to find out is why despite identical air speeds there can be a big difference in volumetric efficiencies. How does an F1 engine achieve 145%? That I would love to know.

In Pipemax there is a page that details what air the engine is seeking and what air is available. That is one big factor in determining volumetric efficiency. Greg when I get home (10 hrs or so) I will send you a paper by Prof.GP Blair and it deals with these issues, time areas and delivery rates etc.

Cheers Greg

slate blue

I think a V10 F1 engine used to suck in 600 cubic metres of air a minute, please correct if wrong. I haven't really looked at this aspect but it is interesting.

Greg

slate blue

Well an update Tuomo generously used his engine sim calculator and came up some of the following figures.
RPM 6,000_250__500__750_7,000_250_500_750_8,000_250_500
Torque ________547 542 538 542 543 533 519 499 480 455 431
HP ___________ 624 645 666 697 723 736 742 736 731 714 697

I was pretty happy with those numbers but thought the torque was too high low in the rev range, that is over 500 ft pounds and one of the issues I wanted to address was to limit the potential damage to the gearbox. I wanted to keep torque limited to 500 ft pounds.So for folks that have sims here's some details.

I put a bigger cam in 260 duration at .050" and 255 on the exhaust. Net lift was 0.525"/0.500" The cam was installed position was 108 degrees on both sides and installed straight up. The comp was 12. to 1 Bore stroke 4.060" /3.543" Rod 6.2" yes the piston speed is fast but not as fast as the Nascar stuff gets, given it is all nascar stuff in the rotating assembly, i.e crank rods pins and pistons the strength aspect will be fine, hopefully the oiling will be too otherwise one big mess.

I gave it plenty of flow on the exhaust and intake, the exhaust is from a 850 hp Gibbs Chevy, literally the best headers used in Nascar, they are the same headers they use on the open engine and plate motors, so great versatility, they are Tri-Y and start of 1.75/1.875/2/2.4 and then to dual 3 or maybe 3.5" and using a by pass valve for torque, I know how well they work. On the intake I tried to convert the flow figures from Larry Meaux of Pipemax which was around 9,000 cfm from the (8) 56 mm throttle bodies.

The flow figures from Tuomo's heads were used on the exhaust side as I will be putting in 35 mm valves this flow will probably be a bit higher from my previous testing on my 2V heads. I used If you use the 28" but plug in 25" it will give an increase over the curve by 5% which is probably fair. The intake ports were 2.4 sq" and so was the intake, the length was short like Louie's around 5" The best spark was chosen. So there are the number


RPM _ 6,000__250__500__750__7,000_250__500__750___8,000__250__500
Torque 485___504__517__518__506___500__500___505___498__484__470
HP____555___600__640__665__674___690__713__745___771__782___784

By Louie 928 in the "A New Monster In the PNW, Congrats Louie!" thread

Greg

slate blue

I bought one SAE paper that included a British touring Car Engine and the author didn't state from what period it was from. The power from memory was around 260 hp or 130 hp per litre, I suspect it may have been a mid ninties engine as the Volvo wagons had around that power in 1995.

However the power climbed rapidly up to 2001 where it reached a peak of 165 hp per litre. This was at a revs capped 8,500 rpm which is why I was interested in the specifics. These engines are dry sumped (now banned) and unlimited lifts on the cams, (now restricted to 12 mm) I will try to post a pic later if there is interest about this topic as they have a very different cam lobe and these are direct acting buckets like ours.

I found it interesting that when they discussed the size of the tappet that they said it was a whopping 36 mm in diameter! Well we are at 35 mm and 38 for the 2V engines, so not too far away from us. The article goes on to talk about making sure the lobe doesn't touch the edge of the tappet which of course is a disaster.

The lift was 0.610" or 15.5 mm which is the same as F1 in the same period, the duration was only 280 degrees ramp to ramp! That is something like my 2V cams which have 251 degrees @ 0.050" So they have very quick ramps and as such they need light components. With an ITB setup 280 degrees total or 250 degrees at 0.050" is docile as Mike Simard has said on Pelican. So that is great news.

While I am not contemplating 15.5 I am looking at 13.5 mm so that may be mixed with the restricted BTTC type cam lobe design. Those cars with wet sumps and 12 mm lift are still over 130 hp per liter and some are still apparently as high as 150 hp per litre. These cam profiles would probably need to be tamed down on the closing ramp so the valve doesn't slam shut as fast and pound the seat.

How you attain high volumetric efficiency is starting to makes some sense, if you have a look at the pic I posted earlier of the Cosworth I beam head, have a look at the intake cam profile. They rip the valve open and put it down much slower to avoid trashing it. I am sure they are employing the same tactics in BTTC.

So it appears getting a great design on your cam is critical to making big power, then of course you need to control the valvetrain. If I do this project I get my valves custom made in Australia, an old bloke who really knows what he is doing, what we can do with the custom valves is when the tappets are changed over to solids due to the revs change the installed height of the spring. The installed height of the spring can be greatly increased by about 10 mm. This is due to the elimination of the plunger in the hydraulic lifter.

So you can get a much longer spring which will be able to better handle the higher lifts being thrown at it. An example of this is Nascar, they use an installed height of around 2", compare that with what we have and you will see how important that extra 10 mm will be. It should allow this to be a very well designed system.

Greg

GregBBRD

Here's some really fresh flow bench numbers. These were taken at 10" and converted to 28". There is no intake system used. The stock head had just had a complete valve grind done, to factory specs.

Stock

.050" 41.2cfm
.100" 90.0cfm
.200 195.4cfm
.300 255.3cfm
.400 271.7cfm

Theshie design head. Titanium valves/beryllium seats

.050" 43.9cfm
.100 97.8 cfm
.200 210.2cfm
.300 279.0cfm
.400 305.9cfm
.500 317.7cfm

ptuomov

Earlier,you said that you can't get the Threshie head to "work." What did you mean by that?

GregBBRD

The heads themselves are pretty nice (expect for the valve guides). The rest of the package is a complete worthless cluster &*%#.

slate blue

Greg, I think your bench is giving numbers that are about 5% conservative, add that factor and your numbers come into line with Tuomo's and Carl's. If that is the case the Threshie heads are flowing around 330 cfm @ 0.500" which is where Carl's ported heads are. If we add that 5% the heads are what Phil claimed. So in all not too bad and definitely worth saving. Sounds like the heads need a sort out and then they can get back to work.

Greg

GregBBRD

I'm not sure about being conservative....perhaps. I'll go flow them on another, (bigger) bench and compare. That's easy, but really not all that important, for me.

Seems that any of these heads will deliver enough air to support a really nice stroker engine. Sure, if you are looking for 800hp, they may need some additional work, like you have done. However, that is not what I've been after with my work.

If you look at any late 928 engine, with the intake manifold off, it is pretty clear (from the areas that get carboned up and from the areas that get "fuel washed") that the fuel flows down the shortwall, then "runs" past the "valve divider" wall, and is still very poorly mixed as it turns the corner and flows through the valves.

Flowing these heads and studying the port velocities and flow characteristics confirmed that there are significant "dead areas" in the stock port design...especially on the short wall, where the fuel is sprayed. The air flow is really "confused" right there and actually has quite a bit of trouble "deciding" which valve to go through. Port velocities get low and the fuel literally "runs" down that wall and through the valves.

My work has been to make the air flow more uniform through the port and remove the significant dead areas that plague the air flow. This allows the fuel to mix much better with the air, resulting in much more uniform "charges".

The results are significant. Our 6.5 liter stroker engines get 2-3 more miles per gallon than their stock 5.0 liter counterparts and have very, very "clean" exhaust, while delivering significant improvements in torque and horsepower.

Kind of "the best of both worlds." Increased performance and reduced emissions. Not quite "green", but not supercharged, dumping boatloads of fuel and using open oiling systems venting to the atmosphere, either.

Hilton

Carl bought Threshie's old stock - sounds to me like its a reasonable asusmption that his CNC porting job reproduces Threshie's 4v design?

If so thats a pretty safe way to decent flowing heads.

slate blue

Yes I was somewhat shocked when I saw how bad my S2 injectors sprayed on the bench. That was one fact that lead me down the path to replace them with the 4 spray hole versions. They used to spray like a hose set on hard not sprinkle. As I mentioned earlier in the thread I would like to use those motobike 12 spray hole injectors and get a well atomized spray.

Greg

GregBBRD

The original pictures of Carl's heads were not close to a developed port...they were just giant, hogged out ports...(the coffee can approach). They were not close to what was done to Theshie's ports. (I have no idea who did the work-up on Theshie's ports.) I have not seen any further information about port work, from Carl....hopefully he has improved his designs.

Note that whoever did Theshie's ports made them adequate for use.....whoever did them did not turn the ports to junk.....like most beginner port grinders. They are certainly not "state of the art."

I'd have to guess that all of the "done" heads were sold, way before Carl got any of the "junk".

GregBBRD

Greg:

I have not considered this. It is possible that better spraying injectors would solve the problems with the air/fuel mixing in the port without having to change the way the air flows through the port? Obviously, the more atomized the spray, the better the fuel would mix, however the direction of the spray is right into a terribly poor flowing area of the port. Is this a good thing or a bad thing? Is there a reason Porsche picked this area of the port to spray the fuel? I'd alway assumed that the fuel sprayed here because that is where the engineers had space to install the injector.

It seemed that fixing the airflow so that it was smoother and directionally more stable was the only solution to getting the fuel to mix consistantly with the air.

Readers please note:

This is a non-hostile discussion about airflow and fuel, with straight-up questions and answers, not the usual "forum" combative crap.

I have great respect for Greg Gray. He researches and studies his topics to a great degree. He understands the theory and knows considerable amounts about what others have done, regarding his topics. Technically speaking, he is "light years" ahead of me. Trust what he says....I'm trying to learn whatever I can, from his reasearch.

I'm more of a "hands on" guy. I grab onto something and fuss with it until I can fix it to work the way I think it should....with total disregard for what others do and have done.