BMEP tells you the net outcome, but BSFC might help to understand some of the underlying reasons but ideally other data is available as wellDavid Redszus wrote: ↑Mon Mar 09, 2020 11:57 amShould we be looking at BSFC or BMEP?digger wrote: ↑Sat Mar 07, 2020 5:47 pmfriction hurts BSFC, negative work hurts BSFC.David Redszus wrote: ↑Sat Mar 07, 2020 3:01 pm
Digger, you are asking for trouble.
While it seems easy to understand measured values, even without an appreciation of measurement error,
it becomes a real son of a biitch to understand WHY.
For a performance engine. I don't much care about BSFC but care a lot about BMEP.
A change in fuels could easily affect BSFC without impacting BMEP.
Engine Masters rod ratio test results
Moderator: Team
Re: Engine Masters rod ratio test results
Re: Engine Masters rod ratio test results
Nope, never said it was huge.digger wrote: ↑Fri Mar 06, 2020 9:08 pmat the 5,700 the number i gave was not a good number for the short rod as it was at the extreme end not an average
at 3,000 i said the long rod was was better
in both cases it was still a small difference not a huge difference like you said
its probably better to try and understand why
Re: Engine Masters rod ratio test results
Yup, from the little data provided it was all over the place..inlet 10deg is enough to make up the differenceLoganD wrote: ↑Mon Mar 09, 2020 1:04 pm This wasn't a very accurate test, I wouldn't read into this too much. The variables were not well controlled.
To do this right you'd need an oil conditioning unit, a water conditioning unit, a complete intake air conditioning unit, and a dyno that uses an electric motor with at least two torque meters for averaging. I'd prefer to see a fuel conditioning unit as well.
Re: Engine Masters rod ratio test results
Isn’t BSFC in this case worthwhile comparing identical engines with just a rod ratio change?David Redszus wrote: ↑Mon Mar 09, 2020 11:57 amShould we be looking at BSFC or BMEP?digger wrote: ↑Sat Mar 07, 2020 5:47 pmfriction hurts BSFC, negative work hurts BSFC.David Redszus wrote: ↑Sat Mar 07, 2020 3:01 pm
Digger, you are asking for trouble.
While it seems easy to understand measured values, even without an appreciation of measurement error,
it becomes a real son of a biitch to understand WHY.
For a performance engine. I don't much care about BSFC but care a lot about BMEP.
A change in fuels could easily affect BSFC without impacting BMEP.
I agree ,I wouldn’t care what the BSFC was if it made more power. Not including if fuel efficiency was a concern
- Stan Weiss
- Vendor
- Posts: 4801
- Joined: Tue Feb 20, 2007 1:31 pm
- Location: Philadelphia, PA
- Contact:
Re: Engine Masters rod ratio test results
I would want to look at BSFC while also looking a fuel lbs/hr, A/F ratio, and scfm /ve%.
Stan
Stan
Stan Weiss/World Wide Enterprises
Offering Performance Software Since 1987
http://www.magneticlynx.com/carfor/carfor.htm
David Vizard & Stan Weiss' IOP / Flow / Induction Optimization Software
http://www.magneticlynx.com/DV
Offering Performance Software Since 1987
http://www.magneticlynx.com/carfor/carfor.htm
David Vizard & Stan Weiss' IOP / Flow / Induction Optimization Software
http://www.magneticlynx.com/DV
Re: Engine Masters rod ratio test results
gmrocket wrote: ↑Mon Mar 09, 2020 5:03 pmIsn’t BSFC in this case worthwhile comparing identical engines with just a rod ratio change?David Redszus wrote: ↑Mon Mar 09, 2020 11:57 amShould we be looking at BSFC or BMEP?
For a performance engine. I don't much care about BSFC but care a lot about BMEP.
A change in fuels could easily affect BSFC without impacting BMEP.
I agree ,I wouldn’t care what the BSFC was if it made more power. Not including if fuel efficiency was a concern
None of it is worthwhile if the ignition advance curve for best output over the engine's entire operating range with each rod length combination is not determined.Isn’t BSFC in this case worthwhile comparing identical engines with just a rod ratio change?
Re: Engine Masters rod ratio test results
The pulls start at 4K, how much of a curve do you think is needed from that point?Tuner wrote: ↑Mon Mar 09, 2020 9:49 pmgmrocket wrote: ↑Mon Mar 09, 2020 5:03 pmIsn’t BSFC in this case worthwhile comparing identical engines with just a rod ratio change?David Redszus wrote: ↑Mon Mar 09, 2020 11:57 am
Should we be looking at BSFC or BMEP?
For a performance engine. I don't much care about BSFC but care a lot about BMEP.
A change in fuels could easily affect BSFC without impacting BMEP.
I agree ,I wouldn’t care what the BSFC was if it made more power. Not including if fuel efficiency was a concernNone of it is worthwhile if the ignition advance curve for best output over the engine's entire operating range with each rod length combination is not determined.Isn’t BSFC in this case worthwhile comparing identical engines with just a rod ratio change?
They did test each engine for max power timing.
Re: Engine Masters rod ratio test results
If the timing wasn't checked at 500 or at least 1000 RPM steps from lowest to highest over the range of interest how will anybody know? This is too big a factor to be ignored.
I've played this tune on lots of different engines but never with the same engine just changing the rod length, as this thread is about, so I recognize that in the variety of engines I've dealt with there is more to it than just rod length.
In my experience, some engines want 1 or 2 degrees per 1000 RPM and some want 2 or 3. The ones that like the most are usually in the short rod category. This trend is found in OEM factory service literature and "off road" tuning handbooks in which advance curve specifications are published.
With the common SBC example of circle track and road race engines I have done this enough times I am sure, beyond any doubt, that an advance curve that increases 1 to 1.5 deg. per 1000 RPM from 3000 to 8000 will give a distinct advantage in a field of others that all have "locked advance", in which case the locked advance is actually retarding about 1+ deg. per 1000 RPM due to ignition system slew rate.
I've played this tune on lots of different engines but never with the same engine just changing the rod length, as this thread is about, so I recognize that in the variety of engines I've dealt with there is more to it than just rod length.
In my experience, some engines want 1 or 2 degrees per 1000 RPM and some want 2 or 3. The ones that like the most are usually in the short rod category. This trend is found in OEM factory service literature and "off road" tuning handbooks in which advance curve specifications are published.
With the common SBC example of circle track and road race engines I have done this enough times I am sure, beyond any doubt, that an advance curve that increases 1 to 1.5 deg. per 1000 RPM from 3000 to 8000 will give a distinct advantage in a field of others that all have "locked advance", in which case the locked advance is actually retarding about 1+ deg. per 1000 RPM due to ignition system slew rate.
-
- Guru
- Posts: 9633
- Joined: Tue Nov 27, 2007 9:27 am
- Location: Chicago
- Contact:
Re: Engine Masters rod ratio test results
I've played this tune on lots of different engines but never with the same engine just changing the rod length, as this thread is about, so I recognize that in the variety of engines I've dealt with there is more to it than just rod length.
It sounds very easy to only change the rod length. But this also means a new piston with a different mass, a rod with a different mass and center of gravity relocation. Now we have G forces that are quite different. Changing only one thing at a time is almost never possible. Except on paper.
Modern computerized ignition systems allow for the construction ofIn my experience, some engines want 1 or 2 degrees per 1000 RPM and some want 2 or 3. The ones that like the most are usually in the short rod category.
a complex ignition map using a number of input parameters. The result is an ignition advance curve that looks like the
Rocky Mountain Range. And it changes constantly, even under conditions we think are stable.
I have yet to meet the racer (or engine builder) who knows the actual timing curve of his engine while on the track.
-
- Vendor
- Posts: 3627
- Joined: Sat Feb 14, 2004 4:04 pm
- Location: Abbeville, LA
- Contact:
Re: Engine Masters rod ratio test results
i'm likewise wondering :Stan Weiss wrote: ↑Mon Mar 09, 2020 12:35 am Where are these dyno sheets at ?
If you have accurate dyno room weather data (BP, VP, TEMP), fuel lbs/hr and A/F ratio. SCFM can be calculated.
Stan
Where are these dyno sheets at ???
anyone have a web Link to these Dyno Sheets ??
Re: Engine Masters rod ratio test results
I don't know what to say. I thought you were acquainted with a better crowd than that. Perhaps you need to get out more."I have yet to meet the racer (or engine builder) who knows the actual timing curve of his engine while on the track."
I have confidence the curve seen on a distributor machine and confirmed in the engine, on a dyno or not, is what you get on the track.
-
- Guru
- Posts: 9633
- Joined: Tue Nov 27, 2007 9:27 am
- Location: Chicago
- Contact:
Re: Engine Masters rod ratio test results
"I have yet to meet the racer (or engine builder) who knows the actual timing curve of his engine while on the track."
You're kidding, right?I have confidence the curve seen on a distributor machine and confirmed in the engine, on a dyno or not, is what you get on the track.
For vintage ignitions tuned on a distributor machine, track results are very often affected by shaft end play,
point bounce and jitter, coil over heating, loose electrical connections, cylinder pressure and temperature variations and a whole bunch more.
For electronic ignitions we have measured ignition lag due to switching delays, heat buildup of coil and ignition box and a whole bunch more.
For mapped ignitions, we have measured variances from the map due to input errors, sensor errors and incorrect mapping. With multiple inputs used to drive ignition maps, it is often not possible to accurately predict actual curves.
The cool thing about ECUs and data loggers is that you can see and measure invisible variables.
The sad thing about ECUs and data loggers is that you can see and measure invisible variables.
Re: Engine Masters rod ratio test results
As in all things, if you think so, or you don't, you're absolutely right.
Re: Engine Masters rod ratio test results
David Redszus wrote: ↑Tue Mar 10, 2020 5:49 pm"I have yet to meet the racer (or engine builder) who knows the actual timing curve of his engine while on the track."You're kidding, right?I have confidence the curve seen on a distributor machine and confirmed in the engine, on a dyno or not, is what you get on the track.
For vintage ignitions tuned on a distributor machine, track results are very often affected by shaft end play,
point bounce and jitter, coil over heating, loose electrical connections, cylinder pressure and temperature variations and a whole bunch more.
For electronic ignitions we have measured ignition lag due to switching delays, heat buildup of coil and ignition box and a whole bunch more.
For mapped ignitions, we have measured variances from the map due to input errors, sensor errors and incorrect mapping. With multiple inputs used to drive ignition maps, it is often not possible to accurately predict actual curves.
The cool thing about ECUs and data loggers is that you can see and measure invisible variables.
The sad thing about ECUs and data loggers is that you can see and measure invisible variables.
I have confidence the curve seen on a distributor machine and confirmed in the engine, on a dyno or not, is what you get on the track.
No, are you?You're kidding, right?
Do you own a distributor machine? How much actual experience do you have repairing distributors and using distributor machines to calibrate advance curves, hours, days, years, decades?
Have you ever gathered timing information on a dyno in 500 or 1000 RPM steps through an engine's full RPM range to maximum engine speed, used a distributor machine to apply that information and confirmed the results on the dyno?
You present a good argument that a vintage mechanical distributor can be a more accurate ignition timing device than an ECU. What do you consider a good vintage?
Re: Engine Masters rod ratio test results
Don't want to lose track of the subject of this thread, comparing the rod lengths.maxracesoftware wrote: ↑Tue Mar 10, 2020 12:58 pmi'm likewise wondering :Stan Weiss wrote: ↑Mon Mar 09, 2020 12:35 am Where are these dyno sheets at ?
If you have accurate dyno room weather data (BP, VP, TEMP), fuel lbs/hr and A/F ratio. SCFM can be calculated.
Stan
Where are these dyno sheets at ???
anyone have a web Link to these Dyno Sheets ??