project 31 8k 5 port
Turbo Mini Forums

I assume there is :
an optimal valve opening speed
an optimal lift for a given valve size
an optimal cam shape for valve train reliability
and a car manufacturer sells durability and reasonable fuel consumption and tries to do that the cheapest way possible.

If optimal valve opening speed is out of reach of optimal cam shape for valve train reliability and the compromise sought after by the car manufacturer does not require it, then we end up with a rocker ratio less than optimal on a power point of view.

That being said, our car manufacturer probably got the best of what was available otherwise.
So he designed a 850 engine and stretched it to 1275 over the years but the DNA of the engine is still there.

I believe cam follower diameter is the limiting factor on the cam side so the only other way to increase valve speed opening is rocker ratio.

Well, that sounded like a can of worm post all right !

Rusty by nature

this might be of some use:

this is what pipemax spits out for the bottom end:

i'm no expert but shaving a few grams of a piston makes sense if you see the G loadings

8000 rpm:
------- Piston Motion Data -------
Average Piston Speed (M/S)= 21,69 in Meters per Second
Maximum Piston Speed (M/S)= 35,37 occurs at 75,451 Degrees ATDC
Piston Depth at 75,451 degree ATDC= 35,8540 MM Cylinder Volume= 152,1 CC
Maximum TDC Rod Tension GForce= 3720,62 G's
Maximum BDC Rod Compression GForce= 2099,97 G's

9000 rpm

Average Piston Speed (M/S)= 24,40 in Meters per Second
Maximum Piston Speed (M/S)= 39,79 occurs at 75,451 Degrees ATDC
Piston Depth at 75,451 degree ATDC= 35,8540 MM Cylinder Volume= 152,1 CC
Maximum TDC Rod Tension GForce= 4708,91 G's
Maximum BDC Rod Compression GForce= 2657,77 G's

Edited by Sir Yun on 8th Jul, 2012.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

yunmiester, what weight of piston and rod was that for ?
it would be great if you could run it for the weight of a stock rod piston combo ,and then my lighter combination ,and see how high up the rpm range it gets before it exceeds the loads on a stock setup.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Hi robert,

I just copy pasted what pipemax spits out. It just uses the rod and stoke to calculate but it does not consider geometry of the entire assembly. ( piston offset ect ect)

It's in G's so you have to take the mass of the combo and multiply it (sort off as it is a little more complicated due to the surprisingly complex geometry).

If you really want to know what goes on you should model the whole lot in pro engineer or something alike and do a FEA.. I'd like to but i don;t have the apps or the skill :(



edit// 138 gram weight saving.. about 5036 N load less



I have NO clue on the tensile properties of an a-series rod, so when it's going to go bang is hard to predict. Judging from what I have read think you could consider nitrocaburising the rods but not the caps as they deform too much

Edited by Sir Yun on 12th Jul, 2012.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

bit of progress , red is new port design ,and the jiggly lines below are the % improvements over a stock 33mm port ..







i have found a way to get about 130 cfm ,so thats my next step .....all this with the 35.7mm valve. :)

Edited by robert on 16th Jul, 2012.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

nice. now thats a handy bit of kit

My small bore turbo project http://www.turbominis.co.uk/forums/index.php?p=vt&tid=473901

this really is cool!

Speeding is like masturbating, everyone does it, but not all of us film it and put it on the internet

[quote=fab,8th Oct, 2010]fuck off

Wish I had such a fun toy in my shed to tinker with. Good stuff.

been playing with the seats robert?

impressive gains !! . i reckon its changed just below the seat area ?

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Some old geezer earlier in the year was telling me that they have started adding material in certain areas of the port, to gain an increase.

i have seen a lot of filled ports but i'm always worried it comes off and gets munched ..

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

Depends on the glue,

there are glues out there that will survive in the exhaust ports!

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM