I know that the motor should "grow" when it gets warm/hot...anyone have some numbers for how much wider the engine grows when it's at operating temperature?

The reason I ask is that it might influence my design of the linkage for my individual throttle bodies

thanks

QUOTE (Mueller @ Mar 16 2005, 09:49 PM)

I know that the motor should "grow" when it gets warm/hot...anyone have some numbers for how much wider the engine grows when it's at operating temperature? The reason I ask is that it might influence my design of the linkage for my individual throttle bodies thanks

carbs dont have issues.....

use a self centering carb style linkage

ALA cb performance

dude, you know who you are talking to right???

I cannot follow the normal path of doing anything

QUOTE (Mueller @ Mar 16 2005, 10:15 PM)

dude, you know who you are talking to right??? I cannot follow the normal path of doing anything

mike... rock on

i can only aspire to be like you my friend...make stuff mo betta!

what do you have in mind oh wild one?

QUOTE (Aaron Cox @ Mar 16 2005, 10:17 PM)

i can only aspire to be like you my friend...make stuff mo betta! what do you have in mind oh wild one?

You must be thinking of someone else, I don't make anything better, just more complicated than it needs to be, LOL

my idea is to have the main throttle cable meet in about the middle of the engine, it'll be connected to a pulley which will have 2 seperate cables feeding to each pair of TB's.

The problem is that if the motor "grows" too much, it can have an effect on the position of the throttle plates....doing something similar to the CB linkage might be better, I'll have to mock something up to measure my engine...of course it has cast iron cylinders right now and my motor and Randels motor will have Nickies which should expand more than the cast iron units.

thats why bellcrank linkages blow....

motor expands, and messes up linkage geometry.....

I recall reading somewhere that it expands by 3-5mm from dead-cold to full hot. Don't know if that recollection is correct, though...

--DD

You wana test individual TB's on my sbc??

The thermal expansion coefficient of aluminum is about twice that of iron. The coefficient for iron is roughly 6x10^-6 inches per inch of length per degree F. That's 0.000006 in. The cylinder section we're interested in is about 3 in long. So, figuring an average 200dF temperature increase from dead cold to running across the whole engine, we're looking at 3 thou for each cylinder. Figure the heads will grow about 2x that, so including the case, I'd make a swag that the whole engine grows about 36 thou, or just under 1mm total from cold to hot, valve cover to valve cover. The centerline of each throttle shaft will move about 0.3mm away from the centerline of the case, give or take a few microns. With Nickies, you'd adjust that up to about 42 thou, or a bit over 1mm total, or about 0.4mm for the throttle shafts.

And typical casting alloys of aluminum don't grow as much as pure aluminum, so both of the numbers above are high. The actual numbers for total width could easily be 0.3 to 0.5mm, and Dave just misplaced a decimal point.

I measured a 911 engine to grow .006-.008 at 220 degrees oil temp and 280 CHT. This was with aluminum cylinders and stock studs. Having a higher grade of stud and iron cylinders would change this, as for the expansion rate of alluminum, throw those calcs out of the window, because the major expansion portion (cylinder and head) are held together by the studs from the cases and their growth is restrained, thats why your figures seem a little high.

Now on 944 blocks, the growth is huge, like .018-.022 not that any of you guys have those rats. I do not know on a type 4 block, But suffice to say if you are making Throttle bodies and engieering them, you must tie them to one another by some solid mechanical means so a linkage system can be stable. But I am sure you already know this. and I hope you are building counter rotating Barrel valves, because if you are doing butterflys, you are wasting your time. You can't make them for as cheap as you can buy them, when you figure time and materials.

But if you are going to all that trouble, build something real nice.

Erik

Its near impossible to answer this question...

When I was designing my aluminum pushrods I noticed that the temp of the engine played such a key role with the expansion rate that the only way to measure it was in increments of 50 degrees.

At minimum the engine grows .010 at max I have seen .030 on an overheated engine...

BTW- Your Nickies change this a great deal because they expand way more than cast iron and their studs are made to stretch with them.


I know what your idea probably is for the linkage, it'll work as long as you can give it some slacl to make up the difference of expansion.

QUOTE (Thorshammer @ Mar 17 2005, 08:37 AM)

I measured a 911 engine to grow .006-.008 at 220 degrees oil temp and 280 CHT. This was with aluminum cylinders and stock studs. Having a higher grade of stud and iron cylinders would change this, as for the expansion rate of alluminum, throw those calcs out of the window, because the major expansion portion (cylinder and head) are held together by the studs from the cases and their growth is restrained, thats why your figures seem a little high. Now on 944 blocks, the growth is huge, like .018-.022 not that any of you guys have those rats. I do not know on a type 4 block, But suffice to say if you are making Throttle bodies and engieering them, you must tie them to one another by some solid mechanical means so a linkage system can be stable. But I am sure you already know this. and I hope you are building counter rotating Barrel valves, because if you are doing butterflys, you are wasting your time. You can't make them for as cheap as you can buy them, when you figure time and materials. But if you are going to all that trouble, build something real nice. Erik

Mike isn't "building" anything, he's using motorcycle fuel injection throttle bodies. The really hard stuff has been done for him already.

I quite like that I can make a complete guess based on first principles and get it within a few percent of his measurements (0.3mm to 0.5mm is 0.012" to 0.020", which is pretty close to his measured figures).

As for the studs constraining the growth of the Al bits, most of the air-cooled studs I've seen aren't steel, but some other weirdo alloy with a thermal expansion coefficient that's close to that of the case and head materials.

Steel 911 studs regardless of their alloy DO NOT expand at the same rate as aluminum cylinders and heads. Thats the reason Dilivar was developed, for the later 2.7 liter. Porsche changed the stud material to increase the expansion rate to try and eliminate studs pulling out of the cases which changed drastically due to the hotter engine temperatures from 5 bladed fans and thermal reactors. So, even the factory with all of their German engineers got it wrong with calculations. Thats why we have simulations these days and testing. To find what is not/or very difficult to calculate. This IS one of those calculation dilemas. Dilivar still does not come anywhere near the expansion rate of the aluminum. So there IS a restraining factor in head studs.

Retrofitting motorcycle throttle bodies is an excellent starting place, The late model Triumphs are FI and have three cylinders. Althought the placement of the injector angle may not be optimum for our type of head, and they are kind of small. It would be cool if he could put together a package that would give a secondary throttle valve and actuator to increase port velocity at lower rpms while enabling a much longer duration camshaft for better top end performance. I would consider TL1000S throttle bodies, plenty in the salvage yards, and 52mm...... yahoo!

Not to get into a pissing contest, but you must realize that temperature has such a great effect and the target temperature the engineers determine, may not be the actual operating temperature. I have seen this with motorcycles, we engineer products and improperly arrive at a result via calculations which can be intuitive, but not always. Shit in, shit out is a common term. As for a direct measurement as to growth at a given temperature, that may be possible, but whos to say that is the temperature achieved. Raby has spent countless hours with the DTM optimizing, and it was designed prior to him taking over the project. So after swirl straighteners and vortex generators (sorry if I don't have the exact changes Jake) he has found the correct combination, through testing. And after all the calculations and all the intuitive figuring, this is what it comes down to: How does it perform in the real world and does it perform as we intended. If not, apply Demmings (drill down) principles and continue refining until it does.

Erik

Yep... Paper is worthless.. It takes trial and error to really work kinks out.

Since I'm no engineer it is my only method.

While it may take longer it yields great results most of the time!

The factory had all sorts of problems. With the 917 motor they found they had to put covers over the nuts on the top of the engine. The cooling air from the fan over-cooled the top row of nuts compared to the lower row, thus the need for insulation.

Dave, The TIV has the same issue..

Thats also why the later 911 had encapsulated head studs.

Charles and I are working on encapsulated Nickies for use with my new heads exclusively.

Won't the linkages heat up and expand a little as well, sort of making the question moot?

QUOTE (Jake Raby @ Mar 18 2005, 09:01 AM)

Dave, The TIV has the same issue..

I kind of figured you would have discovered the problem and found a solution.

QUOTE (Jake Raby @ Mar 18 2005, 08:22 AM)

Yep... Paper is worthless.. It takes trial and error to really work kinks out. Since I'm no engineer it is my only method. While it may take longer it yields great results most of the time!

I'll slightly disagree here.

First, you ARE an engineer. You're designing something, testing it, measuring it, and redesigning to suit. That's ALL an engineer does. Having a degree and/or a certification does NOT make you an engineer, and not having those things doesn't mean you're not one. You differ in method from the way some engineers operate, but the results are the same. One of the greatest engineers of all time, Isambard Kingdom Brunel (quite a name), who designed bridges and steams ships in 19th century England, had no formal training of any kind, largely because no formal training existed when he started, and hardly existed by the time he died.

Second, paper and theory isn't completely worthless, it's just not useful by itself. You use calculations to make approximations, then experiment to test and refine those approximations. If they agree (more or less, these are approximations), then you're on the right track. If they don't, you made a mistake somewhere. This may simply be a calculation mistake, or there may be something else going on you're overlooking. This CAN lead to very interesting new things. More practically, doing the approximations can also reduce number of trials (and therefore errors) you make to get a result. It's a cost saving tool, not an end-all design tool. You don't use paper, you use intuition and experience to avoid some blind alleys. I'm sure there are cases where you could save a considerable amount of time and money by trying out of a bit of theoretical work before you made some of your trials.