| Author |
Message |
theregoeslouis
Samba Member
Joined: June 24, 2021
Posts: 50
Location: Portland, OR
|
 Posted: Fri Feb 10, 2023 10:26 am Post subject: Piston..."Engine Calculator" |
 |
|
I've been working on my engine and I'm at the point where I'm about to install the pistons and heads. I've never done this before but with some books, manuals and internet I've gotten this far but just wanted to double check a couple things
77 bus 2.0 type 4, fueld injected.
This are the specs that I've "calculated"
Do this calculations seem right?
On my deck height, should I be adding the "step" in my AMC head thats about .031
so deck height + step = total deck height?
.041+.031= .072
Last edited by theregoeslouis on Fri Feb 10, 2023 5:15 pm; edited 2 times in total |
|
| Back to top |
|
 |
chrisflstf
Samba Member
Joined: February 10, 2004
Posts: 4262
Location: San Diego
|
| Posted: Fri Feb 10, 2023 10:59 am Post subject: Re: Piston..."Engine Calculator" |
|
|
| 2 plus 2 is still 4. Why do you think its wrong? |
|
| Back to top |
|
|
theregoeslouis
Samba Member
Joined: June 24, 2021
Posts: 50
Location: Portland, OR
|
| Posted: Fri Feb 10, 2023 11:07 am Post subject: Re: Piston..."Engine Calculator" |
|
|
| chrisflstf wrote: |
| 2 plus 2 is still 4. Why do you think its wrong? |
Never done this, but just getting a second opinion.
What would be a good compression ratio?
That seems to be the "topic" everyone has an opinion on |
|
| Back to top |
|
|
chrisflstf
Samba Member
Joined: February 10, 2004
Posts: 4262
Location: San Diego
|
| Posted: Fri Feb 10, 2023 11:27 am Post subject: Re: Piston..."Engine Calculator" |
|
|
| Gonna need motor specs, vehicle and intended use |
|
| Back to top |
|
|
theregoeslouis
Samba Member
Joined: June 24, 2021
Posts: 50
Location: Portland, OR
|
| Posted: Fri Feb 10, 2023 11:43 am Post subject: Re: Piston..."Engine Calculator" |
|
|
| chrisflstf wrote: |
| Gonna need motor specs, vehicle and intended use |
Working on my 77 bus, fuel injected( what other specs?), is just street use, maybe road trips |
|
| Back to top |
|
|
Pruneman99
Samba Member
Joined: February 22, 2012
Posts: 5013
Location: Oceanside
|
| Posted: Fri Feb 10, 2023 12:07 pm Post subject: Re: Piston..."Engine Calculator" |
|
|
| 71mm stroke? |
|
| Back to top |
|
|
94touring
Samba Member
Joined: October 24, 2020
Posts: 672
Location: Tulsa - OK
|
| Posted: Fri Feb 10, 2023 12:10 pm Post subject: Re: Piston..."Engine Calculator" |
|
|
| I'd get rid of the step and keep it at .04 deck height and open up the chambers so you're closer to 9:1 on premium. On the other hand at .07 deck you're at about 8:9 which is good too. 0.7 deck is just a little outside optimal. |
|
| Back to top |
|
|
UK Luke 72
Samba Member
Joined: September 07, 2011
Posts: 2875
Location: Little Britain
|
|
| Back to top |
|
|
theregoeslouis
Samba Member
Joined: June 24, 2021
Posts: 50
Location: Portland, OR
|
| Posted: Fri Feb 10, 2023 12:26 pm Post subject: Re: Piston..."Engine Calculator" |
|
|
| Pruneman99 wrote: |
| 71mm stroke? |
yes |
|
| Back to top |
|
|
theregoeslouis
Samba Member
Joined: June 24, 2021
Posts: 50
Location: Portland, OR
|
| Posted: Fri Feb 10, 2023 12:35 pm Post subject: Re: Piston..."Engine Calculator" |
|
|
| UK Luke 72 wrote: |
Type 4 I'm guessing.
I'll also guess your comp ratio is perfect if that makes you feel better? Based off very little... gotta give these guys some info.
Cam, elevation etc etc. |
Yeah Type 4, This wasn't a complete tear down(( everything was stoke) It needed new heads, but since I was already in there I decided to put in new pistons. |
|
| Back to top |
|
|
Pruneman99
Samba Member
Joined: February 22, 2012
Posts: 5013
Location: Oceanside
|
| Posted: Fri Feb 10, 2023 1:19 pm Post subject: Re: Piston..."Engine Calculator" |
|
|
Oh type IV. Duh. I'm going to just finish eating my crayons.
The only thing I would say is I don't like the step in the heads. I feel it diminishes quench. |
|
| Back to top |
|
|
theregoeslouis
Samba Member
Joined: June 24, 2021
Posts: 50
Location: Portland, OR
|
| Posted: Fri Feb 10, 2023 1:34 pm Post subject: Re: Piston..."Engine Calculator" |
|
|
| Pruneman99 wrote: |
Oh type IV. Duh. I'm going to just finish eating my crayons.
The only thing I would say is I don't like the step in the heads. I feel it diminishes quench. |
is there different types?  |
|
| Back to top |
|
|
Vanapplebomb
Samba Member
Joined: November 03, 2010
Posts: 5573
Location: Holland, MI
|
| Posted: Fri Feb 10, 2023 2:57 pm Post subject: Re: Piston..."Engine Calculator" |
|
|
If it is a “bus” 2.0, the compression is way optimistic because the bus pistons have those lousy dishes in the piston crown… lucky if you can even hit 8:1 with those pistons.
If you substituted the later bus style pistons with the earlier 914 style flat tops, well, now you got something. Type 4 engines love a bit of compression, and a good tight deck. 0.041 is right on the money man. 
_________________
1800 Type 4 Berrien 295
http://www.thesamba.com/vw/forum/viewtopic.php?t=487021 |
|
| Back to top |
|
|
Vanapplebomb
Samba Member
Joined: November 03, 2010
Posts: 5573
Location: Holland, MI
|
| Posted: Fri Feb 10, 2023 3:07 pm Post subject: Re: Piston..."Engine Calculator" |
|
|
| theregoeslouis wrote: |
| Pruneman99 wrote: |
Oh type IV. Duh. I'm going to just finish eating my crayons.
The only thing I would say is I don't like the step in the heads. I feel it diminishes quench. |
is there different types? |
Yes, aftermarket heads can have a step cut. Basically, they added material there to take the place of the head gaskets… which 2.0 engines in particular were notorious for burning through. VW released a bulletin to remove them and add a barrel spacer to compensate. The aftermarket step cut heads compensate by adding the lip around the edge so you don’t need barrel spacers.
To get a good tight deck, you can either turn the cylinders down to shorten them so the piston is basically at the top of the cylinder, or machine out the step cut in the head. If you have a step cut head, and all else is stock, effective de k height will remain around 0.070 inches, which is too much in my opinion. T4 engines run cooler with a tighter deck, in my experience.
_________________
1800 Type 4 Berrien 295
http://www.thesamba.com/vw/forum/viewtopic.php?t=487021 |
|
| Back to top |
|
|
nsracing
Samba Member
Joined: November 16, 2003
Posts: 9758
Location: NOVA
|
| Posted: Mon Feb 13, 2023 8:05 am Post subject: Re: Piston..."Engine Calculator" |
|
|
That is a healthy compression - 
Also -leave the deck alone at that number. Do NOT increase that deck |
|
| Back to top |
|
|
Takamotti
Samba Member
Joined: January 02, 2020
Posts: 73
Location: Finland
|
| Posted: Thu Feb 16, 2023 3:24 am Post subject: Re: Piston..."Engine Calculator" |
|
|
| theregoeslouis wrote: |
Do this calculations seem right?
|
No, stock chamber 50 and piston has 14 pocket + distance shim below cylinder is 0,25mm and head gasket about 0,35mm (stock deck height 1,9mm) = compression 7,4
If you have the step on heads you probably won´t use head gaskets but result is the same. If you remove the shim too, compression will be 7,5 |
|
| Back to top |
|
|
Vanapplebomb
Samba Member
Joined: November 03, 2010
Posts: 5573
Location: Holland, MI
|
| Posted: Thu Feb 16, 2023 4:52 am Post subject: Re: Piston..."Engine Calculator" |
|
|
Yeah, huge difference between bus dished pistons and 914 flat tops. Unfortunately, the OP hasn’t said which pistons he is using.
_________________
1800 Type 4 Berrien 295
http://www.thesamba.com/vw/forum/viewtopic.php?t=487021 |
|
| Back to top |
|
|
|
