SPI, deffinition

WingingIt74 Sun Oct 07, 2012 2:21 pm

I know or I think I know what it is. For those of us who are a little fuzzy, can someone explain it to us?

dckrsn Sun Oct 07, 2012 2:45 pm

Hi Travis. It's a rainy Sunday afternoon here, and I'm way too lazy. sleep

Luckily these guys weren't.
https://www.coxengineforum.com/t1051-sub-induction?highlight=sub+port+induction
https://www.coxengineforum.com/t1439-sub-piston-induction-what-does-it-do?highlight=sub+port+induction
I think Rusty's explanation in the second thread is the most succinct and easiest to digest.
Bob

Kim Sun Oct 07, 2012 8:29 pm

Thanks for that link! I somehow let Rusty's note slip by without being pasted in my Important Engine Notes File !!!

**RknRusty** Sun Oct 07, 2012 9:21 pm

Kim wrote:Thanks for that link! I somehow let Rusty's note slip by without being pasted in my Important Engine Notes File !!!

The question gets asked every so often. We could sticky an explanation. But since I based my whole explanation on my own inferences(I wasn't taught that stuff anywhere), I hesitate to post it as fact. Someone could come along that knows the real answers and blow me out of the water. Then I'd look all SPI, deffinition Crazy

Kim Mon Oct 08, 2012 8:12 am

RknRusty wrote:
Kim wrote:Thanks for that link! I somehow let Rusty's note slip by without being pasted in my Important Engine Notes File !!!
The question gets asked every so often. We could sticky an explanation. But since I based my whole explanation on my own inferences(I wasn't taught that stuff anywhere), I hesitate to post it as fact. Someone could come along that knows the real answers and blow me out of the water. Then I'd look all

Not likely! Someone picks on our Rusty, they pick on ALL of us !!!!

WingingIt74 Mon Oct 08, 2012 8:13 am

Basically, if you see the bottom of the piston skirt, it's SPI?

**Cribbs74** Mon Oct 08, 2012 8:16 am

WingingIt74 wrote:Basically, if you see the bottom of the piston skirt, it's SPI?

Yep, when at TDC if you see a gap then you have some SPI.

I tend to think of it as Ram Air! lol!

PV Pilot Mon Oct 08, 2012 10:04 am

A somewhat free forced induction.

**RknRusty** Mon Oct 08, 2012 10:44 am

cribbs74 wrote:
WingingIt74 wrote:Basically, if you see the bottom of the piston skirt, it's SPI?

Yep, when at TDC if you see a gap then you have some SPI.

I tend to think of it as Ram Air!

Yep, ram air by suction. The vacuum that the rising piston creates is only partly satisfied, because there is some resistance from the reed and(in most cases) small venturi, so when the SPI gap opens, the remaining vacuum pulls in free air to fill the rest of that void. With Tee Dees, SPI isn't quite as effective since at TDC the valve is still partly open, venting the crankcase to atmospheric pressure through the wider venturi.

Thanks for y'all's vote of confidence. BTW, I just made all that up too. Smile

Sponsored content

SPI, deffinition

SPI, deffinition

Re: SPI, deffinition

Re: SPI, deffinition

Re: SPI, deffinition

Re: SPI, deffinition

Re: SPI, deffinition

Re: SPI, deffinition

Re: SPI, deffinition

Re: SPI, deffinition

Re: SPI, deffinition