911T Head Flow Rates

[snowman]

[snowman]

Why it do that I didn't push the post button yet?

I just measured the Flow of a stock 911T to verify earlier measurements I had made. For anyone interested here is what the flow is:

Stock 911T w 46MM intakes 42MM exhaust
intake
lift flow (cfm at 28" )
0.1 " 60
0.2 " 121
0.3 " 174
0.35" 192
0.40" 200
0.45" 200

exhaust
0.1 " 52
0.2 " 99
0.3 " 129
0.35" 142
0.40" 149

These are very good rates for a stock engine. It means that the head will support up to a 300 plus HP engine, normally aspirated. Note that there is almost no increase in flow above 0.35" of valve lift, so put the money in duration, not lift unless mods are made to the head.

[TimT]

Porsche heads flow amazingly well, They didnt use the T head for competition engines as far as I know, but they used an S head or a competion head in engines where they extracted 230hp from a normally aspirated engine using 60's technology (type 911/22) with MFI they got 230hp from the same engine (911/20)

These engines used 38mm ports.

Given modern engine controls Im sure the specific output of the T engine can be increased easliy, without porting the heads..
Compare the Porsche head geometry to a small block V8....By inspection you can tell which flows more air.
There are a few people who have made Porsche heads flow more, but the returns are dimishing, as the head works so well to begin with ( check out CMW and the "D" port)

Id love to see 300hp out of a 2.2T, Just how long will it last?

[BK911]

These sound like the flows from a 2.2T head. An MFI head flows about 25 cfm less because of the MFI port. That's why it's crucial to plug the entire port when converting to carbs, most people only plug the opening.

BK

[snowman]

The flow numbers just mean that the head will support the 300 HP. NOT necessarily the crank, valve springs, Pistons, whatever. If you shot peen the crank, rods, and balance the engine, use better rod bolts, and head studs, add oil squirters, add a front oil cooler, increase the compression ratio to 12:1, change the pistons to forged,change the cam, and rejet the carbs, you can get the 300 HP. AND thats on a 50 year old engine design!
With all the modern junk you can get about 330HP.

[Zendalar]

What kinda of cam would have that 0.35" lift? I mean are there any that would fit in straight up and no need to regrind.

Also, If one used the heads it now has, shifted the cam to one which has 0.35" lift, what pistons could one use there?

I was thinking if one could use pistons from some other car, which has the same size diameter, almost same height when connected to rods, but would have thick enough top to take off metal so the 0.35" lift would not cause the piston to hit the valves.


If I just could find a seized 911 engine somewhere, preferably a T , cheap or free (would pay postage of course, Wonder how much it would cost to ship an engine from the USA to Finland.)

[jluetjen]

I've combined this data with some flow data that BK911 has pulled together in the past and it seems to hold together. It looks like the S heads flow a little bit better at higher lifts, but it's hard to tell given small sample size.

As far as the T heads being good for 300 HP -- I doubt it. 160 is about the best that you will most likely see out of 911 motor with T heads. The 2.4E's define that point -- any more HP then that and Porsche used the S heads or something with bigger ports. BTW - Porsche did rally some early 914-6 2.0's with T heads and S cams and they reportedly got 180 HP. I've documented elsewhere on this BBS where non-CIS 911's seem to have limit of about 100 meters/second intake gas speed before they get choked off. I have yet to see many (if any) engines where the peak HP engine speed was pulling an intake gas speed of more then 100 meters/second.



BK911 -- I've got a 2.4TK (30 mm intake ports) that I'm taking apart right now. Once I get the heads off I'll send one to you if you still have access to a flow bench and you can try running that one too. This will start to give everyone a pretty complete view of the 911 head flows for the early cars at least.

- John

[Scott Clarke]

John-
How did Porsche get 180hp from 32mm ports?
-Scott

[snowman]

The reason I can say that the heads can support up to a 300 HP engine is simple. IF you use the ACTUAL air flow of the head, thats what I measured, it is tha REAL ammount of air that can be sucked in to the engine. If you mix the correct ammount of gas with this air, about 13:1, you can get 300 HP that simple. It has been shown over and over again that this is correct, and many engines have been built that can prove this is accurate to withing a few percent. In fact newer engines with all the tricks can get about 5 percent more HP than this. BUT THE CAVIOT, I am only talking about a head, not an engine.

The basic limitation here is 2.2 liters, the displacement. The engine is being limited by the displacement, not the heads. There seems to be a limit of about 2 HP per cubic inch, no matter how good the cam, heads, or whatever, for a normally aspirated engine. If you do everything absolutely right you can get this much power. Thats the most compression, cam, best carbs, whatever. The point is that the heads will not be limiting the power, something else will be, until the displacement is increased to over 150 cubic inches. At that point the heads will have to be made better.

There are technical glitches of a small order of magnitude to deal with, such as intake velocity. Making the ports bigger, as in the case of a 911S will decrease the intake velocity at a given RPM. However the S engine is designed to operate at a much higher RPM than the T engine. So making the ports bigger only keeps the maximum intake velocity constant at the point of maximum power. A point I made earlier is that at a LOWER RPM, ie 6000, the T engine looks like it can make 157HP, the same as the S at this RPM. But not the same at the higher RPM that the S can operate at. With the correct displacement the stock T heads can make 300 HP. With the 2.2 displacement the RPM must be higher than the 2.2T design is capable of. The primary limitation being port size and compression. The other limitation is simply material, ie it ain' strong enough to spin up that high (6,800 RPM), eg non shot peened rods, cast crankshaft. But it is strong enough for 6000 RPM.? The quesion then is heat. Are squirters really needed?, are anti shuffle pins needed. The answer, probably not.

What the heak am I getting at anyway? Well the 2.2 T engine is capable of a lot more than Porsche made it to be. For whatever marketing reasons they detuned the 911 engine. Whats the easiest way to get the most out of what they did? The heads are real performers, they did not end up limiting the power for the T engine all that much. This is nice to know as it points to cheaper ways to increase the power a lot for a few bucks. It is well known that replacing the cam in T engine can up the power, what is not known is "is there easier ways to get back the power Porsche threw out to degrade this motor? The flow numbers seem to indicate that simply increasing duration of the cam will do the trick, up to a point, ie 6000- 6500 RPM. Even more intriguing is the possibility of simply retarding the cams to get the power, see related post.

[jluetjen]

Scott;
That particular ~1970 914-6 engine (901/26) is not particularly well documented. There is also a similar 911 rally engine from 1967-68 (901/30) which appears to only have generated 150 HP. Here's what I know of the spec's. It appears that the valve size is the biggest difference, so basically the valve curtain area.

901/26: 80x66 mm B&S, 42 mm intake valve,38 mm exhaust valve, 32 mm intake and exhaust ports. Weber 40 IDS carbs. 911S cam. 180 HP at 6800 RPM, 132 lb/ft of torque at 6200 RPM. The average intake gas speed through the 32 mm ports at the peak HP engine speed (basically calculated as the average air speed to pull one cylinder's worth of air through the ports every 2 rev's at 6800 RPM) is 93.5 meters/second.

901/30: 80x66 mm B&S, 39 mm intake and 35 mm exhaust valves, 32 mm intake and exhaust ports. Weber 46 IDA's. 911S cam. 150 HP. Apparently this early engine had "polished" intake ports, increase CR, platinum spark plugs, a sport exhaust, free venting of the oil tank, a lightened flywheel, special alternator and special spark plug gaps (The Porsche Book by Boschen and Barth). Assuming the same cam, engine speeds and ports sizes this engine will have the same intake gas speed as the 901/26.

And then as I mentioned is the 2.4E which made 165 HP at 6200 RPM with the same 32 mm port size. In this case at 6200 RPM the average intake gas speed is 100.3 meters per second.

Finally there is the vaunted 2.7RS engine also with MFI which made 210 HP at 6300 RPM. Curiously this engine's peak HP engine speed is down significantly from the 2.4S's even though it is using the same heads and cams. But if you look at the intake gas speeds again through the ports, it is 92.4 meters per second at 6300 RPM.

It just seems that 911 motors don't want to pull more then 100 meters per second (excluding CIS motors where the drop in manifold pressure below ambiant downstream of the air meter allows a higher gas speed in the ports).

Jack;
I've shown you my examples -- can you show me yours. Can you give me some examples of 911 engines with 32 mm ports (basically T or E heads) which make more then 180 HP? You mention that it has been proven over and over again in many motors that it's possible. Can you show me? I'm in the process of building a 911 E-Prod motor and I'd really be interested in how to get there (excluding any form of supercharging or nitrous).

[Scott Clarke]

John-
Thanks for your response. I guess what I'm currious about is the combination of S cams and 32mm ports. I have assumed that there is little to be gained with such a combination, as the limiting factor seems to be the gas speed in the ports (as you have documented well), but this 180 hp 2.0 motor makes me wonder. The cost of porting and modifying MFI stacks is quite a bit higher than reground cams. It also seems like the combination might be contingent on displacement, as gas speeds for a given port will rise with displacement, right?

[jluetjen]

Scott;
I think that you and I have been thinking of the same thing. Why could a 2.0 get 180 HP with 32 mm ports while a 2.4 could only seem to get to 165?

In the case of the 911 and other engines with individual intake runners, I suspect that it does have to do with the cylinder volume. Basically the intake ports limit the total amount of air that can flow (on average) as well as the amount of air that the cylinder can breath in one "gulp". The smaller cylinders of a 2.0 at 6800 are basically taking smaller (.333 liter) gulps more often. The 2.4 is taking .444 liter gulps less often, but the 32 mm ports are limiting the amount of air that it can ingest in any one gulp at higher RPM's.

I guess the "general rule" would be that smaller capacity cylinders at higher RPM's will more closely approach the absolute flow through a given intake port then a cylinder with a larger capacity at a slower engine speed.

I wonder if I should put a set of S cams in 2.0E and pick up a few more HP???

[snowman]

John,

The heads flow enough air with the ports in them to make up to 300 HP, the rest is dependant on everything else. In otherwords there is a displacement that with these heads will make 300 HP and some particular RPM. In fact the RPM can be calculated given the flow. I do not remember the formula but I will look it up. The formulas for these calculations come from the Company that makes the Superflow air flow bench. They have a video of a class they run on the subject.
Jack F

[TimT]

John havent we been through this before ad nauseum ?

Jack has some valid points, but there must be a reason that Porsche stopped developing the 2.0/2.2/2.4 engines..... They had the heads and cams to make loads of hp, but the controls didnt exist.

They probably just realized it was easier to get power from a larger displacement engine, than it was to to try and extract every bit of power out of a small displacement engine .

My ex T engine has been shuffle pinned, all the oil mods done to it, and have has squirters installed. The heads have been massaged. Jack keeps mentioning shot peened rods...Porsche rods are "well prepped" from the factory. All the right things have been done.

Ill be happy as a pig in ***** if this makes over 210..

[Scott Clarke]

John-
It seems like the other variable is the duration of the "gulp." A larger displacement cylinder could effectively draw air through the port at or near peak gas speed for a longer period of time, even if some restriction (due to port size) existed at the period of peak demand (when the piston is moving fastest while the intake valve is open). Perhaps this suggests that a camshaft with a lot of duration might work with a motor with small ports. I'm in waaay over my head, but I'm intrigued by the information Jack is presenting.

[snowman]

Tim T,
Cubic inches always wins.

The best reason that you will not get the 300 HP out of a 2.2 engine is that it happens at about 9000 RPM. That means a whole lot of things must change and it is no longer $ wise to go that way. It would simply burn up in 10 minutes or less.

I am talking about the MAX HP that is possible. A street engine can NEVER run at or even near this as its life is measured in minutes. Street engines can run at about half the max ie about 150 HP for a 2.2 and live a while. Even then the life is reduced to 100,000 to 125,000 miles from that of a conservative engine, 500,000 miles.

The discussion seems to miss the main point, that is this. If you have a 2.2T engine and you want to get the most bang for your buck, don't fool with the heads as they do not need any improvement.

Increasing the compression is productive if you do not mind paying for high test. This is good for about 10 HP and improved fuel mileage.

Another 10 HP can be gained by improving the windage inside the crankcase, free HP so to speak. And finally increasing the duration of the cam will add up to the power of an S engine. ( A little longer duration than the S cam will do.) Or if the dyno 2000 program is correct, simply retarding the standard T cam by 10 degrees will bump the HP up to 157 HP.
If you add this up you get 177HP at about 6000 RPM. Thats the same as an S gets at 6800 RPM. You would be wise to add the squirters as the heat had gone up, and the T rods are not shot peened, so you should do this, and the T crank is not as strong, so you should shot peen the radius to prevent cracking and wallah, you have the same or even better performance than the 911S did without all the expense. Just don't plan on reving the T up to 6800 RPM and getting even more power as the components are not up to it.

[jluetjen]

Thanks TimT for the reality check. I do think that there is a good thought here about being able to use duration to eke the last HP from a given set of heads. Sure extra duration will help, which is why putting in a set of E (AKA Solex) cams will get more HP out of a T engine (~130) (assuming that the pistons are replaced or modified to avoid a spatial event with the valves). Put S cams in (with similar changes to the pistons) will get you pretty close to one of those rally engine's with 150 HP. The problem is that you can only extend the duration so far for a couple of reasons:

1) Longer duration generally means higher rev's which we discussed earlier.
2) If your overlap increases, you start to lose compression at low rev's which kill's the torque at those speeds. This is why a T or an E produce more torque then an S below 4000 RPM. Putting 906 cams for example in a T head may result in an engine that pulls like a 906 below 5000 RPM and stops developing HP at 6500 RPM. I doubt the engine will ever pull to 8000 RPM like a 906. That's not much of a rev range.
3) If you spread the lobe centers you'll keep the compression at lower rev's but you'll start to be opening the valves too early/late compared to the piston's stroke.

Basically the compromises get to be too much to make it worth while. At some point you just need to open the ports to let in more air. That point seems to be at about 160-180 HP for 911 engines 32 mm ports.

[snowman]

I am getting used to the forums capabilities. Here is the flow bench I used to measure the 911T head.

Next is a a silicone mold of the intake port and compression chamber I made using an RTV made for this purpose. It is accurate to within a thousand of an inch of the actual head.

The silicone mold is used to help visualize the inside of the ports and make accurate measurements of the same. It is also used to makd a plaster copy of the head to experiment on.

[emcon5]

Anyone have the flow numbers from a stock late-SC 3.0L head?

By "late" I mean smaller ports.

Tom

[jluetjen]

Snowman; Cool!