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Engine Modification Horsepower Calculator
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ideola  



Joined: 01 Oct 2004
Posts: 15505
Location: Woodstock IL

PostPosted: Thu Aug 23, 2007 6:29 am    Post subject: Engine Modification Horsepower Calculator Reply with quote

I've been reading Corky Bell lately. I put together a spreadsheet to help me calculate achievable power output numbers, and thought you all might be interested in looking at the results. Here is an image, along with a link to an downloadable, editable spreadsheet that you can all play with.

{EDIT} Now available online as a public Google Docs spreadsheet.

This doesn't take into account every possible variable, but it allows you to plug in the key modifiable parameters of the engine (stroke, bore, volumetric efficiency, rpm and boost) and determine reachable BHP numbers. It also provides flow requirements and pressure ratios, which should be useful in mapping your goals onto a compressor map to see if it will provide the boost and flow required for your application.

Comments and suggestions for improvements to the spreadsheet are welcome. I don't profess to be an engineer, I'm just applying some basic principles and formulas to help estimate (and that's the key word) whether my HP goals are actually achievable.

Enjoy!



{EDIT}
I put the flow requirements in CFM and cm3/sec because some of the maps have flow expressed as CFM and some as cm3/sec ... this should help in the conversion process so you can plot your goals onto a map regardless of the unit of measure used on the map...
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Last edited by ideola on Thu Dec 11, 2008 10:17 pm; edited 1 time in total
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Rasta Monsta  



Joined: 12 Jul 2006
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PostPosted: Thu Aug 23, 2007 7:00 am    Post subject: Re: Engine Modification Horsepower Calculator Reply with quote

ideola wrote:
I've been reading Corky Bell lately.



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bass gt  



Joined: 02 Dec 2004
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PostPosted: Thu Aug 23, 2007 7:43 am    Post subject: Reply with quote

SteveVery Interesting.

As a point of reference, my car is astock displacement engine, but with improved intake system, and slightly better turbo. My car made 250 crank BHP at 12 psi of boost, so somewhere in the upper regions of the stock figures.
more boost made more power, but in a diminishing pattern. I think the backpressure of the turbo started to choke it up, and the air temps got very hot
oh, BTW, ou have tooooo much time on your hands
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jazz guy  



Joined: 26 Nov 2002
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PostPosted: Thu Aug 23, 2007 8:50 am    Post subject: Reply with quote

Quote:
tooooo much time on your hands

Waaaaaayy tooooo much! But it is fun to hear from someone excited about upgrading his car's performance. I look forward to reading more about your progress!

Cheers, Brian
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RC  



Joined: 25 Mar 2007
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Location: Australia

PostPosted: Thu Aug 23, 2007 1:17 pm    Post subject: Reply with quote

Yes, since you do appear to have a lot of time available how about calculating the piston speed at 7.5K with your stroked crank and comparing it to the stock one at Porsches 6.5K redline.

See you have crower rods but what other mods are you intending on the botton end?

IMHO it would be more effective to do the EFI first but ultimately t is your time and money.

Roger
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ideola  



Joined: 01 Oct 2004
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PostPosted: Thu Aug 23, 2007 2:12 pm    Post subject: Reply with quote

Too much time? Why? I was going thru these numbers anyway to see if my goals were realistic...it was faster to throw together the spreadsheet than to sit down with paper & pencil and write out a thousand different calculations, lose the paper, and have to redo the calcs all over again Just my analytical mind at work.

RC wrote:
how about calculating the piston speed at 7.5K with your stroked crank and comparing it to the stock one at Porsches 6.5K redline
All I need is the formula. And by the way, the build I am going for is Scenario 2. I just put Scenario 3 together to see what the numbers would do at the extreme limits of what might be possible on our little 2.0 truck motors In no way do I mean to suggest that Scenario 3 is remotely feasible...Scenario 2, on the other hand, is what I'm shooting for...

RC wrote:
IMHO it would be more effective to do the EFI first
Firstly, EFI doesn't deliver power...and that, after all, was the point of this post, and the primary objective of my build. EFI might help harness the intrinsic capabilities of the engine by enabling modern fuel control and proper air/fuel mixture in high-output scenarios, but in and of itself, EFI does not deliver power. I see little value in diverting project funding or time toward developing an EFI setup now based on theoretics, which could prove to be inadequate later when we understand the real-world power output potential and fuel requirements based on an actual functioning engine. In my situation, I believe it's best to address the fuel delivery system as the final stage of development, after the powerplant has been built to pump as much air as possible.

Secondly, the engine is completely in pieces (as is the chassis), so there is absolutely no point of spending a dime on EFI right now. EFI is nowhere close to being a bolt-on off-the-shelf prospect, unlike many of the mods I've performed to the basic engine design. Furthermore, I've never done EFI before, and so, as with anything new, it will be a trial and error process, one I am not eager to pile on top of building a stroked and boosted monster. One variable at a time, please!

Thirdly, I will be executing a very controlled development & tuning process once the core powerplant is back together. When I've confirmed that it is functioning properly at slightly-higher-than-stock boost levels (for which a slightly modified version of the stock CIS system will be JUST fine), then we'll tackle the fuel delivery system. The execution plan will follow a careful, iterative process of dialing in more boost, monitoring results and effects on the various engine components, while carefully controlling air/fuel (among other variables, of course). I've heard too many horror stories about guys building their monster and blowing it up on the first run. Happens all the time here in Motown, but not on this project!

RC wrote:
ultimately it is your time and money.
Right you are...and bear in mind, I have four other P-cars that are all well-sorted and downright enjoyable; it's not like this project is a daily driver or even a track car that I need to get back together next week. This is a long-term learning project, a hobby, one I enjoy spending time and money on, so I'm in no hurry. My objective is to build a beautiful, impressive, monster-fun car that can be driven on the street OR track, and that will give the condescending air-cooled snobs a run for their money...all on a budget that is less than a quarter of a modern 911. My goal is to also avoid as many mistakes as possible and to do as much right the first time as I can.

RC wrote:
What other mods are you intending on the botton end?

{EDIT}
I've moved this information into a new thread to help keep this one focused on the spreadsheet. For info on my specific build, go to the official Ideola's Ultra Wide Body 931 Build

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Last edited by ideola on Sat May 09, 2009 4:49 am; edited 3 times in total
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ideola  



Joined: 01 Oct 2004
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PostPosted: Thu Aug 23, 2007 2:19 pm    Post subject: Reply with quote

bass gt wrote:
stock displacement engine, but with improved intake system, and slightly better turbo. My car made 250 crank BHP at 12 psi of boost
Steve, very very interesting point of comparison! Do you have any idea what affects your "improvements" may have had on VE? If you look at the graph, 250 HP at 12 psi with stock internals puts you dead nuts on .077 bhp/cid (the high end of Mr. Bell's scale) ... assuming you're getting at least 85% VE. I'm wondering if you're getting even better VE...!

The other factor to consider is that the book is 10 years old (published in 1997)...I suppose it's feasible that recent enhancements in fuel management, such as the system you're running, could potentially drive the bhp/cid numbers a bit higher. Maybe????

In any event, the formulas are only meant to be a guide to point to an approximate achievable power output. Any way you slice it, your real world numbers confirm that the chart has some merit.
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bass gt  



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PostPosted: Thu Aug 23, 2007 6:14 pm    Post subject: Reply with quote

i was just ribbing you!! I know how much time it takes to complete these projects!! I have started on next years race config now, even though the season is not starting until April 2008. Time flies ect.
My optimised set up is based upon a good EFI system and ECU to control it. I believe this is the single most significant improvement we can make to these cars. It sems to clean up the running, improve ignition and fuelling, thus increasing the BHP in one move. I would be suprised if the EFI/ECU and Intercooler alone once set up correctly are not worth somewhere in the region of 40-50bhp.
As you say, the book is 10 years old, and although technology has moved on, i think the fundamental principals within hte book are still valid.

Regards,

Steve
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Min  



Joined: 04 Nov 2002
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PostPosted: Fri Aug 24, 2007 1:17 am    Post subject: Reply with quote

ideola wrote:
When I've confirmed that it is functioning properly at slightly-higher-than-stock boost levels (for which a slightly modified version of the stock CIS system will be JUST fine), then we'll tackle the fuel delivery system.


I could be wrong, but I havn't heard of anyone with a stroked/slightly increased boost motor running CIS ....... so what data points were you using to suggest that cis would be just fine? ..... stroking a motor changes what it needs completely from stock, the ignition curve will no longer be adequate, and neither will the fueling CIS is intended to provide. Good luck.

Min
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Rasta Monsta  



Joined: 12 Jul 2006
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PostPosted: Fri Aug 24, 2007 1:52 am    Post subject: Reply with quote

+1 to that. . .remember how CIS fuel metering works. . .the shape of the cone the metering plate moves up and down in is how the fuel delivery is enginieered into the system for differing RPM and load conditions. One shape=no adjustablility. I think changing basic engine characteristics as you are suggesting (bore, stroke, cam profile) will be very problematic for the CIS system.
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ideola  



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PostPosted: Fri Aug 24, 2007 2:43 am    Post subject: Reply with quote

Don't disagree. I'M NOT PLANNING TO RUN CIS LONG TERM...JUST LONG ENOUGH TO GET THE MOTOR RUNNING...AND THEN TACKLE EFI.
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Rasta Monsta  



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PostPosted: Fri Aug 24, 2007 2:52 am    Post subject: Reply with quote

I understand, but do you want your fresh build leaning out at an inoppurtune time?
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ideola  



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PostPosted: Fri Aug 24, 2007 2:58 am    Post subject: Reply with quote

OK, I think it's time to start a new thread. I'm open to suggestions on my build, no doubt, but the point of this particular thread was to solicit comments on the spreadsheet as a general tool to plan an engine build.

I'll start another thread to solicit feedback on my specific build.

{EDIT}
I've moved the aforementioned information into a new thread to help keep this one focused on the spreadsheet. For info on my specific build, go to the official Ideola's Ultra Wide Body 931 Build

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Last edited by ideola on Sat May 09, 2009 4:50 am; edited 2 times in total
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Rasta Monsta  



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PostPosted: Fri Aug 24, 2007 6:39 am    Post subject: Reply with quote

Ooops, sorry. The chart is quite interesting!!


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leadfoot  



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PostPosted: Fri Aug 24, 2007 4:23 pm    Post subject: Reply with quote

very nice work, often optimistic to assume %VE efficiencies,
what are the GT cam specs out of interest?

As for your build it sounds excellent,
Leadfoot
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