blown 87

That Diesel is not going to fare well with a 2 lb bird down its throat either, and damn sure not the ones the throw at aircraft engines at 350 MPH.

Pretty wild footage of big turbines chewing up big birds and not miss a beat.

Ducman82

i remember seeing that video of the 777 engine eating a frozen turkey shot from a cannon.....

GregBBRD

Mark Anderson's 928 won't run at full throttle on my dyno, without many hundreds of pounds of weight in the rear. Even with that, it kills the tires very quickly.

I'm not sure how many rear tires I've blistered or completely blown the tread off of, but it is certainly measured in dozens.

Again, why would I bother to run an engine on an DTS engine dyno, if I could possibly do this on my own dyno? Certainly, it will go onto my dyno, for tuning and testing once it is in the car....but it won't/can't be operated at full throttle for long periods of time...like it can be on an engine dyno.

Look, if Carl wants to spend thousands of dollars getting a car ready and moving it across the country to run at Bonneville, without having ever ran it at full throttle for more than a few seconds....that's great...it's his time and money.

I felt like I need to test my engines as close as I can to how they are going to be run...in order to find any potential issues.

928man

WOW! I didn't know my simple question would create all this ruckus, your right Dave!

928mac

This is a very interesting thread.
Thank you to all all of you that have added to it.
Please continue for us less experienced guys

My faverite engine dyno vidio is the porsch 911 test dyno that rolls the engine side to side and back and forth,
seen here
http://youtu.be/fv53RbvgfGc

This 935 6 cylinder engine pulls over 900 HP on this video

http://youtu.be/wPfK_BispVo

I don't know, maybe Porsche had something with the apposed flat 6, but I am a front engine 8 cylinder man.
I guess its a north american thing
.
.
.

slate blue

So just for fun I keyed in the following details, 4.186" bore 3.75" stroke, peak power at 8,000 rpm volumetric efficiency at 115% and got required airflow of between 380 and 405 cfm at peak cam lift. They would be achievable in itself due to 375 cfm has been done on a much smaller bore and flow normally gets better with bigger bores. So that gets you right onto the edge of 900 hp NA. That efficiency BMEP will not be a good as say a Nascar engine.

Realistically, the port would need to be large and it would be a race only engine, it would want to live higher in the rev band. A standard S4 port is around 2.4 sq" in terms of cross sectional area (CSA). The head I did from memory was around 2.5 sq" and I also flowed it at around 2.7 sq but it lost some flow due to the reduction in the short side radius I had built. Even at 2.7 sq the port would not be big enough.

Say 4.186 x 4.186 x 3.75 x 8000 x 0.00353/ 2.7 = 687 FPS when you really want it down in the low 600 FPS range. that would mean a port with roughly a 3 sq" cross sectional area, that's big.

900 hp maybe very hard to attain but regardless that engine with heads like that could easily do over 800 hp. A VE of 110% is required for 800 hp with headflow of between 345 and 365 cfm

GregBBRD

Frank:

I own my own flow bench and have data from stock and modified heads...I'll need to go back and look at some stock flow numbers to get you exact numbers. I don't want to guess.

I can provide you with stock numbers....but "fully ported" is left pretty much to what the individual person believes is "properly" ported and what is appropriate for the individual engine. Since I'm working mostly with "naturally aspirated" street/track engines, I need to have ports that have adequate flow for my power goals and still have enough velocity to work well from idle to full desired rpms. They need to work well making 40 horsepower, at cruise, and they need to work well making 400, 500, or even 600 horsepower....depending on what the customer desires. Currently, I have about 5-6 different port designs that all work very well...for which engine they are designed to work with. You need to keep in mind that I've personally been "cutting" on 928 heads for over 20 years...so I've had a bunch of time/have a lot of experience to "work up" different port designs.

This gets pretty complex, but here's the "short version": Airflow and air velocity through an engine must be matched to what the engine is designed to achieve. It makes no sense to increase airflow to very high numbers, if the engine will never use these flow numbers. Higher airflow will almost always result in a loss of velocity...which hurts how an engine fills the cylinders at lower rpms. If you go to a company like Air Flow Research and read about their heads, they make many different versions of cylinder heads, for the same basic engine (IE: Big Block Chevy.) If you carefully study the airflow that they achieve versus the size of the port, size and airflow are very critical. The differences in airflow and size can actually seem insignificant, but if incorrectly applied, can turn an engine into something completely wrong for the desired application. This is why I have several different port configurations.

When I "saw" Carl's ports that he "had professionally ground" for his supercharged engine...I suggested that they had used the "coffee can" method of porting....just hog the port out until you are very close to minimum port wall thickness....bigger must be better!

His ports might work adequately at WOT on a supercharged race engine....but I'm dubious (understatement) that they would work on anything else....I find it absurd that he now thinks he can offer them as CNC ports for street naturally aspirated engines....but I find a lot of what he tries to do absurd, so that is not a big surprise.

Mike Simard

My current engine has a 3.34² at the head/throttle interface. that was after machining .100" from all sides. My concern was keeping a consistant taper through the entire intake tract. My flow numbers though are nothing like what you've mentioned and don't have the good low lift flow that GB gets either. I have my own theories about airflow and don't consider steady state flow rate all important. A port sees an accelerating/decellerating column of air in real life! That mantra is also convenient when one is not a head porting expert

So would the current valve spacing be usable for 900+hp? The port cross section could be opened up a wee bit but those valves are sitting in the middle of a giant bore. Mine is 4.286 x 3.700. The curtain area of a pair of 39mm valves looks ample at .500 lift but they are lost in the bore. That's my main concern. Building a 15:1 engine for 8000+ rpms is one thing, how would it like those little valves in the middle?

Thanks for the interesting discussion Slate'.

Strosek Ultra

I think Mike Simards intake port area is somewhat too large. He is loosing air velocity. What can been seen from the pictures the intake tracts are very short. Looking at the dyno chart of his engine I would like to tune the length of the intake tract for 6000rpm (40cm or 16" from the open end down to the valve head). In order to get 100+ hp from one cylinder you need two 42mm intake valves which can be achieved without changing the spacing. In order to support the 42mm intake valves the intake port cross section area do not need to be larger than a diameter of 48-49mm (appr. 2.9 sq"). I prefer running 36mm exhaust valves in combination with the 42mm intake. This creates a small problem, the valves will interfere with each other during overlap. The inclined angle of the exhaust valves need to changed by one degree. Some machining is necessary, oversize exhaust valve guides must be custom made. We make them ourselfes. We never cut the valve guides in the ports. Good support of the valves is vital. Oversize 37mm solid lifters also on the intake side will be installed. We use lightweight motorcycle lifters. I never use hydraulic cams in a high performance engine. The valve lift need to be about .500. We usually have WEB Cams to do our custom made cams. I have developed what I think a rather smart solution for an adjustable cam sprocket on the intake cam. In that way the cam timing can be altered as you wish. The intake port will flow about 240 CFM at 10" (400 CFM at 28"). Actually I need to invest in a larger flow bench for these big heads. These valves sizes are for a bore size of 4.250". Made my first porting job in 1966 on a BMW R69S 600cc motorcycle. Much has happened since that.

Ake

tv

VERY COOL! First time I have seen visual proof of the Nardo runs, mentioned first by the french owner and in the 2002 euro gathering PDF.

The 928S (LH euro?) run AVERAGED 156mph for 24 hours!!!!!!!!!!!!!!!!!!!!

That means they were doing about 160 or more on track to make up for pit downtime. Like the guy in the track video says, that's FLAT OUT! My Euro loves to red line and runs like a top and has also done that speed.


Does anyone have a full size shot of this poster? This would make the ultimate 928 poster!

tv

Can anyone make out what kind of wheels are on that car or the sponsor decals?

slate blue

Hej Ake, the current GT3 head has a lot in common with the late model 928 head, there is so many GT3 engine variations also but the race engines often have 42 mm intakes and 35 mm exhausts, that ends up being quite reasonable in terms of valve area to bore size. The race engines use around 102 to 103 mm bores. I believe the included angle is 27.4 degrees. Mike also makes cams, you should check them out, they are very nice.

GregBBRD

The proof of what one does is in the results. You have to be doing something very right with your port work. I personally have not achieved enough airflow through the 928 head to "support" making the horsepower that you are able to make. Your rear wheel power indicates that you are making over 700 flywheel horsepower. That means that your ports have to be flowing 20% more air (about an additional 30 cfm) than I have been able to achieve, in my work.

To be able to make 600 hp from one of my heads, I'm getting a true VE of about 105%. While I know that the "Internet" has created "urban myths" of very high VE and everyone thinks a VE of 110% to 130% happens everyday, I can count, using both hands, the number of engines I've built (in my lifetime) that actually achieve a VE over 100%!

I'd be thrilled to see a 5% increase in airflow, from where I am at. A few cfm increase is a huge gain, when working on an already "developed" port. I can't even begin to figure out how to improve things by 20%. Everytime I study and flow these ports, I seem to be kicking my flowbench...wondering what is wrong with it. (I have trouble kicking my own ***...so I have to settle for kicking my flowbench.)

My hat is off to you, Mike!

BC

Supposedly, a 944 tuner/builder is using the PC-9 coating from Swain on JE and other aluminum alloy pistons and its working.

Z

Has anybody mentioned Kelly-Moss yet? Years ago already they built a couple of normally aspirated 928 engines making over 800hp. That was on an engine dyno, not rwhp. The engines were de-tuned to 7xxhp in the car when set up for racing, in part because of drivetrain and traction issues. Seems that some drivetrain parts and the tires were having a few more issues than they were back when the turbo four cylinder engine was in the car.