[Tom Vaught]

Originally Posted by charlie66

My real wonder is if it has the same compression ratio at 33 psi as the old 40, is there any more / less or the same heat? It is 7 less psi but with the same cylinder pressure.. So is it a wash or is there more to it? I lean to think if its the same pressure , then with having less psi it might have less heat...

You are on the right track there Charlie.

There is a Physics process called the Heat of Combustion that comes into play with all fuels and the pressure and temperatures that they start out at.

You kept the same fuel and Air/Fuel ratio but you changed the combustion process with the change in the compression ratio prior to the combustion event.

So you actually did not keep EVERYTHING exactly the same except for the compression ratio.

Food for thought. At the end of the day, sometimes just better to be happy with the new combination vs try and figure out completely why the numbers changed.

Tom V.

[charlie66]

Maybe. haha...

[Tom Vaught]

I can send you some links to the Heat of Combustion for Ethanol or you can do a search yourself if you have the inclination, Charlie.

Tom V.

[charlie66]

Originally Posted by Tom Vaught

You are on the right track there Charlie.

There is a Physics process called the Heat of Combustion that comes into play with all fuels and the pressure and temperatures that they start out at.

You kept the same fuel and Air/Fuel ratio but you changed the combustion process with the change in the compression ratio prior to the combustion event.

So you actually did not keep EVERYTHING exactly the same except for the compression ratio.

Food for thought. At the end of the day, sometimes just better to be happy with the new combination vs try and figure out completely why the numbers changed.

Tom V.

Thanks Tom. But figuring all this out is fun for me. Especially when I find things out that nobody really cares about... I like that on the paper I made with the comparisons , that the compression ratio spike at 27 psi shows in the real world with my new build...

[charlie66]

Originally Posted by Tom Vaught

I can send you some links to the Heat of Combustion for Ethanol or you can do a search yourself if you have the inclination, Charlie.

Tom V.

Ok Thank you...

[Tom Vaught]

Heat of Combustion Explained:

http://en.citizendium.org/wiki/Heat_of_combustion

(There is a chart in the article with many fuels and values)

I have posted below two fuels used in racing.
Heat of Combustion Ethanol vs Methanol

Methanol
Molar heat of combustion - 726 KJ/mol
Molar mass - 32.042 g/mol
Density - 0.7918 g/cm3
Molar Volume - 40.467 mL
Heat of Comustion - 17.94 KJ/mL

Ethanol
Molar heat of combustion - 1367 KJ/mol
Molar mass - 46.0688 g/mol
Density - 0.789 g/cm3
Molar Volume - 58.388 mL
Heat of Comustion - 23.41 KJ/mL

Tom V.

[charlie66]

Im not sure where E85 fits in with all those figures ..

Im trying to learn in comparison how different the to different compression ratios really are besides the psi factor. Seems to me when you find the right psi where the two equal the same out come in compression ratio after boost there very similar to tune.. In my case it seems things go south at 27 psi though .. I find this very interesting that the chart I made shows the same thing....

[73 TRANSAM]

Charlie, that is nice of you to share your real world experience on your two different compression combo. I wish I would have read your chart when I was at the beginning stage of building my first turbo conversion. That chart you have made will be helpful for the guys who's thinking on building a boosted Pontiac. Good luck and happy Boosting..

[charlie66]

Originally Posted by 73 TRANSAM

Charlie, that is nice of you to share your real world experience on your two different compression combo. I wish I would have read your chart when I was at the beginning stage of building my first turbo conversion. That chart you have made will be helpful for the guys who's thinking on building a boosted Pontiac. Good luck and happy Boosting..

Thank You Edwin . But you have chose the perfect compression ratio for your motor..

Its going to be a monster .

You should make a thread about . Everyone will be interested . I guarantee it !

[Stan Weiss]

Originally Posted by charlie66

So getting back to the subject on comparing the change I made in static compression ratio. I made a conversion chart showing what the differences are between 8.4 an 9.8 with boost.. Its starts out where there's around a 5 psi difference between the 2 to equal the same boosted compression ratio. Then as boost rises it eventually grows to almost 7 psi in there comparison . That's where the old 40 is the same as the new 33 psi. But its interesting to me that the change doesn't really show all that much until 27 psi. At the top of the list in the beginning the increase is around .09 of a point. By 27 psi its .86 of a point. Then by the end its 1.92 almost 2 points .. So something is drastically changing at the 27 number.. Another interesting thing is now that im running the car with the change and not just looking at the conversion chart I can tell that the motor gets very angry at an after 27 psi. There's no doubt that it does.. So there's a correlation there confirming some validation of the chart.. From 20 to 25 psi there's a power change but go 2 more to 27 , feels bigger. Yes this is just my a$$ meter so there's no track numbers or anything like that .. I will be going over to the dyno again one of these days though...

Ok so here's the conversion chart I made . I hope it will be of some interest to others as it is to me...

I still need to get my head around these calculations. Why are the two I have red lines with not linked.

Stan

[Stan Weiss]

Charlie,
I am not sure why there is a difference in are calculations. This is what i get.

Stan

8.4:1 CR
psi -- effective CR
10.00000 14.116
11.00000 14.687
12.00000 15.259
13.00000 15.831
14.00000 16.402
15.00000 16.974
16.00000 17.545
17.00000 18.117
18.00000 18.689
19.00000 19.26
20.00000 19.832
21.00000 20.403
22.00000 20.975
23.00000 21.546
24.00000 22.118
25.00000 22.69
26.00000 23.261
27.00000 23.833
28.00000 24.404
29.00000 24.976
30.00000 25.548
31.00000 26.119
32.00000 26.691
33.00000 27.262
34.00000 27.834
35.00000 28.406
36.00000 28.977
37.00000 29.549
38.00000 30.12
39.00000 30.692
40.00000 31.263
41.00000 31.835
42.00000 32.407
43.00000 32.978
44.00000 33.55
45.00000 34.121
46.00000 34.693
47.00000 35.265
48.00000 35.836
49.00000 36.408
50.00000 36.979

==========================

9.8:1 cr
psi -- effective CR
10.00000 16.469
11.00000 17.135
12.00000 17.802
13.00000 18.469
14.00000 19.136
15.00000 19.803
16.00000 20.47
17.00000 21.136
18.00000 21.803
19.00000 22.47
20.00000 23.137
21.00000 23.804
22.00000 24.471
23.00000 25.138
24.00000 25.804
25.00000 26.471
26.00000 27.138
27.00000 27.805
28.00000 28.472
29.00000 29.139
30.00000 29.806
31.00000 30.472
32.00000 31.139
33.00000 31.806
34.00000 32.473
35.00000 33.14
36.00000 33.807
37.00000 34.473
38.00000 35.14
39.00000 35.807
40.00000 36.474
41.00000 37.141
42.00000 37.808
43.00000 38.475
44.00000 39.141
45.00000 39.808
46.00000 40.475
47.00000 41.142
48.00000 41.809
49.00000 42.476
50.00000 43.143

[charlie66]

Originally Posted by Stan Weiss

I still need to get my head around these calculations. Why are the two I have red lines with not linked.

Stan

what do you mean when you say , not linked?

[charlie66]

Originally Posted by Stan Weiss

Charlie,
I am not sure why there is a difference in are calculations. This is what i get.

Stan

8.4:1 CR
psi -- effective CR
10.00000 14.116
11.00000 14.687
12.00000 15.259
13.00000 15.831
14.00000 16.402
15.00000 16.974
16.00000 17.545
17.00000 18.117
18.00000 18.689
19.00000 19.26
20.00000 19.832
21.00000 20.403
22.00000 20.975
23.00000 21.546
24.00000 22.118
25.00000 22.69
26.00000 23.261
27.00000 23.833
28.00000 24.404
29.00000 24.976
30.00000 25.548
31.00000 26.119
32.00000 26.691
33.00000 27.262
34.00000 27.834
35.00000 28.406
36.00000 28.977
37.00000 29.549
38.00000 30.12
39.00000 30.692
40.00000 31.263
41.00000 31.835
42.00000 32.407
43.00000 32.978
44.00000 33.55
45.00000 34.121
46.00000 34.693
47.00000 35.265
48.00000 35.836
49.00000 36.408
50.00000 36.979

==========================

9.8:1 cr
psi -- effective CR
10.00000 16.469
11.00000 17.135
12.00000 17.802
13.00000 18.469
14.00000 19.136
15.00000 19.803
16.00000 20.47
17.00000 21.136
18.00000 21.803
19.00000 22.47
20.00000 23.137
21.00000 23.804
22.00000 24.471
23.00000 25.138
24.00000 25.804
25.00000 26.471
26.00000 27.138
27.00000 27.805
28.00000 28.472
29.00000 29.139
30.00000 29.806
31.00000 30.472
32.00000 31.139
33.00000 31.806
34.00000 32.473
35.00000 33.14
36.00000 33.807
37.00000 34.473
38.00000 35.14
39.00000 35.807
40.00000 36.474
41.00000 37.141
42.00000 37.808
43.00000 38.475
44.00000 39.141
45.00000 39.808
46.00000 40.475
47.00000 41.142
48.00000 41.809
49.00000 42.476
50.00000 43.143

I don't know why. my calculation's are based off of the facts of my motor. Cam timing events, actual effective stroke number/bore size and rod length too and Altitude . Could it be that? I don't know...

[charlie66]

Wow ! yours are much higher!

[Stan Weiss]

Originally Posted by charlie66

what do you mean when you say , not linked?

I guess I do not understand what you charts does. I was thinking you were looking to see what boost at the old CR and boost at the new CR produced the same effective CR.

Stan

[charlie66]

I was looking to take my old compression ratio with a X amount of added boost pressure and compare that answer to my new ratio answer. Then compare at what psi both answers where at. So mostly it was a 5psi difference up until 27 psi where it started to grow more. This way I could keep the original tune I had as close as I could with minimal change.. And thats what ended up happening...