slate blue

Well, I managed to get some cash together to get this test done, the suspense was killing me. So while the head flowed is a development head this port configuration can be changed. I won't keep reflowing it as I did the 2V head and history has shown there will be more on the table probably another 10 to 20 cfm but when you see the figures that may not be needed. I have compared the flow figures to the stock figures posted by Carl of 928 Motorsports or where there were not available I used Tuomo's numbers.

LIFT______STOCK______MODIFIED
0.050"_____42cfm______53cfm
0.100"_____105cfm_____103cfm
0.200"_____187cfm_____234cfm
0.300"_____248cfm_____291cfm
0.400"_____267cfm_____342cfm
0.500"_____297cfm_____370cfm
0.600"_____306cfm_____382cfm

The link here http://www.topplocksverkstan.se/mercedes190dtmtopp.html

As you can see the heads I have outflow these also. So big things would be expected from an engine like this

The link is to a Mercedes DTM head and those engines are 2.5 litres, I don't know what it revs to but will try to find out, it makes 373 hp though. My proposed engine is 6 litres and revs to at least 8,000 where I would like peak power but it would redline around 8,250 to 8,400 rpm.

While the top end flow figures were not exactly what I was expecting as I thought at peak cam lift I may have 400 cfm if I was lucky, 375 cfm is pretty good but those low end flow figures are huge. They will help a lot.

Below is flow figures from some of Darin Morgan's Nascar RO7 heads, so the best in the business. You can see these 4V heads out gun them to 0.500" and then the tables are turned, does the 4V engine flow enough down low to equal the best Nascar heads?

Probably not but I don't think it is that far off, especially with the "rev rule" where the engines are not seeing 10,000 rpm anymore. What that means is that the Nascar engine in the real world may not create the demand to use all that air now. Maybe these days their ports are smaller because they are seeing less revs? It certainly seems like it in this listing. http://cgi.ebay.com/ebaymotors/ws/eB...#ht_500wt_1182 815 hp from less than another 10 cfm and they won't flow as well down low.

LIFT_Version1 Version2

0.2000 131.9 142.9

0.3000 214.4 220.7

0.4000 298.8 306.7

0.5000 368.3 371.1

0.6000 409.8 408.5

0.7000 424.9 426.4

0.8000 441.6 446.4

0.9000 449.2 453.5

1.0000 451.2 459.2


So as some will now I am looking for development partners to get certain bits made, the head design is pretty much sorted but a CNC program will be needed, the cams are now accounted for, Mike Simard can make these, the headers, materials at least are fairly easy to access, these are made from inconel but stainless will probably do. The intake is where there is further development needed. That includes the throttle bodies which might be Mike's or use 944 throttles. It is a complex induction system and will be a essential element to success. Need at least 3 interested parties to build this engine and you will need to be able to bring some skills to the table. Let me know if there is any interest.

Greg

John Speake

Did you also compare with the figures claimed by Phil Threshie in the article in the 928 Forum magazine ?

slate blue

Well John I did but with my eyes failing me I have to guess the figures, also Phil quoted figures with the manifold on, that is fair enough too but just not an apples to apples comparison.

Phil's figures below,

0.100"_____84cfm
0.200"____190cfm
0.300"____276cfm
0.400"____308cfm
0.500"____331cfm

If these are slightly wrong I probably should have spent my money on glasses or at least a magnifying glass

There is better flowing heads out there, I failed to match the ones in this thread https://rennlist.com/forums/928-foru...or-sale-3.html although I do not know what the lower numbers are nor the port velocity which are all critical factors in making actual power versus flow numbers. Although I absolutely have no doubt they were great. It would be nice to know if they are on an engine and how they are performing. It would help with projections and design.

Those flow figures quoted were

"390 cfm at .500 lift at 28" _ ??????
366 cfm at .440 lift_B1 cam lift
330 cfm at .400 lift _ stock gt lift"

There are differences in benches, just like there is differences in dynos and some heads may flow well and not make power like they should as mentioned in that thread. Also there is different flow curves, some may flow great up high but the cam doesn't go that high, others may flow better down low and sacrifice the high lift numbers.

The bench we use is accurate and slightly conservative, that has been deduced from comparisons from AFR "Airflow research" heads and other heads that have been on other flow benches.

As I mentioned development is not finished, the port I flowed was not optimized, I intend to "hi port the head and fill the floor. Once I do this I will never be able to sell the head if it doesn't go ahead, so I just did the first major change to see what we would get. Just like Phil I would like to flow it with the throttle body on with the intake runner connected.

The next change fully brings into play the Formula one design, I suppose I will do this when I make the manifold adaptor plates like the ones Adrian showed on 928 racing. At that point I need to know what the design is. The worry is the epoxy may fall out. I intend to coat the port to protect the epoxy which is very expensive, if you went on cost alone it should work.

Oh yes, the port is 5% bigger than a standard 928 port.

Greg

John Speake

So what have you done to increase the flow ? I assume 968 valves, but you say you haven't done much to the basic port shape yet ?

slate blue

John, I am not a big fan of the 968 valves for this application, the valves I am using have not been optimized, that is the optimum valve angle has not been identified. I am going to use quite a flat valve and the test was done with tulip exhaust valves. Formula one valves are surprisingly flat. The flat valves tend to be a bit lighter too, it may save going to Ti on the intakes, I would never use Ti on the exhaust. Using stainless valves is better for durability.

The port shape is changed but not drastically, as I mentioned 5% larger and that is basically wider. While the port may not flow the highest ever achieved it has enough air for 800 hp. Pipemax say I need between 340 and 360 cfm. Being a basic program it doesn't allow input of lower lifts where this head is very strong. The trick is using all that air.

It would be interesting to see what others have achieved and then what power numbers they have, so we can get an idea what port flow and speed they had to achieve certain power levels.

So please stroker people publish your numbers. The number especially interesting are the ones that have the none standard manifolds, as we know the standard manifold has limitations. These numbers may well explain why Louie engine is very strong in relation to other strokers.

Greg

John Speake

There's a stroker with ITBs going together near me over the next few months..... so we can see how that works out.

slate blue

I have been just informed by the developer of Pipemax that I should not use 120% VE. Apparently very very difficult to achieve despite everything being optimized. 110% is what should be used for this engine, that takes the power down a lot, that 10% is equal to 100 hp loss.

I'm told work off the lower figure adjust if needed. The 56 mm throttles are apparently sized well for this application, which is great news for this project, the $10 throttles great stuff. So all that extra flow won't get used unless I achieve more than 110%.

So John that will be interesting, are the heads going to the flow bench? Without that we wont be able to work it out. I was reading up on the early British Touring car engines and at their peak they achieved around 165 hp per litre. All that happened at 8,500 rpm. It would be interesting to have a chat to some of those builders.

Greg

stuartph

Greg

Neil Brown engineering have made a few BTCC Honda engines and some DTM Audi as well, try talking to them

BC

Hi Greg. Where is this "928 racing" - is this a website?

Lizard928

it is a mailing list Brendan.

slate blue

Stuart funny enough the article was on Neil Brown engineering, they were the ones that achieved just over 165 hp per liter. I would absolutely love to chat to them, to solve my questions a look at the spec sheets of one of those engines. I only need 135 hp per liter and basically I can turn it to 8500 but I was being conservative.

So things like headflow at the various lifts, the spec of the camshaft, the runner diameter to work out the speed of the air, details of the exhaust although I have a fab or a Good Fab exhaust from an engine that produced 140 hp per liter so it is up to the challenge and I checked that with manufacturer who was very helpful.

So just typing this out, an expert has also confirmed that 56 mm throttles are perfect so really it will all come back to the camshaft and the air speed. I suspect a quick action cam will be critical in capturing the air rammed into the cylinder. The quicker the cam the lighter components need to be, the buckets weight 36 grams, beehive springs will save a lot, Tuomo has had some of these made already. Then the valve, on the intake side, what to use? A steel valve will weigh around 65 grams versus a Ti one at 40 grams. These are big big factors and to have someone been there do that would be fantastic.

I was also reading about the Volvo BTTC engine and it had 0.825" lift. Now I don't know what its airflow curve was like but this is why I was excited by the flow curve of the port I have just done. At 0.300" lift it can support 600 hp and at 0.400" lift it can support over 700 hp, and the cam has still got more lift left at around 0.525" nett, so I may not need some crazy lift. .525" should be quite durable with a thick oil and DLC.

Also another idea I had was to use two injectors side by side, as my port is wider than standard each injector could spray at each valve not the divider. The injectors I want have 12 spray each for a super fine spray and well atomized fuel, the bikes report around a 2% gain over standard injectors. Think about it, the fuel should goes more evenly into the cylinders and less should land on the port walls and maybe have better propagation?

Greg

BC

You mean like the old "get 100s of emails a day" thing? What does he think this is? 1994?

blau928

Greg, have you seen my injector block/runner design for the SC/Turbo setup..?

ptuomov

Greg --

Kudos, your heads will likely have a higher peak power potential than mine, and you probably completed them for less cash than what I will end up spending.

What size valves did you use in your test? Mine were stock S4, 37mm intake.

If you'd have to pick a single intake lift number that you think is the most relevant, what would you pick? I'd pick .300, given the 37mm intake valve and 7mm stem. My heads flow 280 CFM at that lift, yours seem to go at 290 CFM.

What bore size did you flow you heads with?

My heads have essentially the same minimum cross-sectional area as the stock .4R heads. What casting revision did heads did you start with? Is the 5% increase in the size the increase in diameter or area? Furthermore, is it the increase in the minimum or average?

How much did you end up increasing the combustion chamber size to reduce the shrouding?

Did you get the local flow velocity numbers from your flow guy? Just interested in seeing how uniform the flow is. Not that I really understand what the benefits of uniform flow are...

Best, Tuomo

P.S. You might want to ask Jim Morton what his big heads flow. Dennis Kao posted some photos of those here some time ago.

docmirror

I made a chart, cause I'm a geek. But I didn't label the axes well. Anyway, what I want to show is that the lift is about finished around .4 or a bit higher. Once you get to the area of the lift where the valve opening column is bigger than the surface of the valve, the gains fall off quickly. I would think anything past .5 will show little additional power. Depending on ramp, intake geometry, etc.