Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 05-26-2020, 04:57 PM   #261 (permalink)
Master EcoModder
 
gumby79's Avatar
 
Join Date: Dec 2014
Location: Butte, Montana
Posts: 714

little jona - '91 Dodge D 250 first gen cummins LE
Team Streamliner
90 day: 23.4 mpg (US)

Little Jona airo modded - '91 Dodge RAM 3/4 TON D 250 24 AUTO
Pickups
Team Cummins
90 day: 18.5 mpg (US)

The Salted Hound Jenny. - '87 Dodge Ram 50/D-50 5sp 4X4
90 day: 20.24 mpg (US)

Jona Allison aero - '91 Dodge Ram D-250 Le
90 day: 20.84 mpg (US)
Thanks: 206
Thanked 416 Times in 269 Posts
Quote:
(But I am still struggling to understand how that helps on engine modifications, as you suggested.)
An engine that is more effectively extracting energy from the fuel being inserted will go faster by translating more power off the same fuel at the same throttle setting. EG :this would allow modifications targeting a specific throttle% setting.

If all the parasitic losses are isolated meaning not changed,then a positive or negative result in speed is to the engine modification.

especially if it is repeatable with Aba.

In my opinion motor modification testing in this manner would have to occur with absolutely no crosswind. Julian has kindly demonstrated and charted how much of a skew this is had on the Windows Up Down Baseline test

---
Julian may I suggest an amendment to your test procedure.

Windows up > down as Baseline skue/ calibration run at the beginning of a test session to establish the current environmental conditions versus Baseline so that multiple iterations of a modification can be compared through time

----
Quote:
But a fixed amount of fuel does not equal a fixed power! It closer approximates a fixed torque. But given the influence of that on the drag calculation (^2 rather than ^3), the basic approach should still be valid (on diesels anyway)
No.
Only for naturally aspirated diesel ( ancient dinosaurs not applicable to this discussion)
Diesel is a fixed amount of fuel not a fixed amount of power measured in Horsepower or Torque ,Diesel is a variable ratio engine. Therefore can make a variable amount of power on the same amount of fuel based on how hard the turbocharger is spooling changing the fuel ratio and power output.


With a fixed fuel rate if you increase the load on the engine it lights the turbo better resulting in a higher pressure ratio going into the intake leaning out the engine changing the power output continue loading the engine and continue building boost at the same fuel position. Observation of this fact, is the dividing line between Gas and Diesel Chassie Dyno operators; gas guys go to the floor and read the graph industry-standard that works, is accurate, and is backed up at the track. Diesel Dyno operator is going is going to throttle up to the window hit the brakes and throttle up to load the turbo once the turbo is loaded the brakes are released now you have a loaded dyno test for accuracy of your all out effort, that you can back up at the track. EG a diesel tuned on a chassis dyno using Gas techniques for 9.8sec in the 9.9 bracket class( bracket race speeds/times are dictated by safety equipment limitations) will brake out (produce more power than expected and exceed the safty limmits of of class required equipment, resulting in a banned from competition until New safety requirements of the next higher class are met ).

__________________
1st gen cummins 91.5 dodge d250 ,HX35W/12/6 QSV
ehxsost manafulld wrap, Aero Tonto
best tank: distance 649gps mi 24.04 mpg 27.011usg
Best mpg : 31.32mpg 100mi 3.193 USG 5/2/20


Former
'83 GMC S-15 Jimmy 2door 2wd O/D auto 3.73R&P
'79 Chevy K20 4X4 350ci 400hp msd custom th400 /np205. 7.5-new 14mpg modded befor modding was a thing
87' Hyundai Excel
83 ranger w/87 2.9 L FI2wd auto 18mpg on the floor
04 Mitsubishi Gallant 2.4L auto 26mpg
06 Subaru Forrester XT(WRX PACKAGE) MT AWD Turbocharged 18 plying dirty best of 26mpg@70mph
95Chevy Blazer 4x4 auto 14-18mpg
04 Chevy Blazer 4x4 auto 16-22mpg


  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 05-26-2020, 08:21 PM   #262 (permalink)
Master EcoModder
 
Join Date: Nov 2017
Location: Australia
Posts: 496
Thanks: 36
Thanked 528 Times in 291 Posts
Quote:
Originally Posted by gumby79 View Post

Julian may I suggest an amendment to your test procedure.

Windows up > down as Baseline skue/ calibration run at the beginning of a test session to establish the current environmental conditions versus Baseline so that multiple iterations of a modification can be compared through time
Yes that could be done. However, at this stage I use throttle stop testing only for changes that are made on the spot.
__________________
Modifying the Aerodynamics of Your Road Car

A really good book that should be added to the library of everyone working in automotive aerodynamics, as well as those making car aero modifications at home. - Rob Palin, former Tesla aerodynamicist
  Reply With Quote
Old 05-27-2020, 06:31 PM   #263 (permalink)
Master EcoModder
 
gumby79's Avatar
 
Join Date: Dec 2014
Location: Butte, Montana
Posts: 714

little jona - '91 Dodge D 250 first gen cummins LE
Team Streamliner
90 day: 23.4 mpg (US)

Little Jona airo modded - '91 Dodge RAM 3/4 TON D 250 24 AUTO
Pickups
Team Cummins
90 day: 18.5 mpg (US)

The Salted Hound Jenny. - '87 Dodge Ram 50/D-50 5sp 4X4
90 day: 20.24 mpg (US)

Jona Allison aero - '91 Dodge Ram D-250 Le
90 day: 20.84 mpg (US)
Thanks: 206
Thanked 416 Times in 269 Posts
Quote:
Originally Posted by JulianEdgar View Post

Yes that could be done. However, at this stage I use throttle stop testing only for changes that are made on the spot.
I guess I was thinking too far ahead. Any future changes to the barge boards / Edgarwit external air curtains to correct the lack of attached flow past 1/3-1/4 cord at "any angle of attack/yaw angle " a direct result of using the wrong airfoil profile as we both agree the only way we can find out if a modification is done right is to test. This modification was done well not right, the only way to do it wrong is to get a net negative result, do not let this statement detract from the Brilliance of your device I have a similar design drawn years ago. Inspired by the Dodge racing team that attempted reverse flow Cooling, in high-pressure with a base of the windshield out through the front. They were successful in their designing and function testing up to 205 miles an hour where the belt would start slipping next iteration was going to be a COG belt, the team member that return my email said NASCAR stepped in and they're not even allowed to talk about outside of what was published in the article. for every team member would be banned from Nascar for life.

"Further testing and versions will be required to get it right." you're advice to us, our advice to you

Future Generations will need calibration runs . I still need to post my retractionon on that thread. I was completely wrong about my analysis of the flow with the eroding clay. I assumed a single yaw angle. A very nice presentation would be a series of eroding clay different yaw angles, to see the impact this has, at least two with the same yacht angle but from opposite sides.


Quote:
...
(But I am still struggling to understand how that helps on engine modifications, as you suggested.)
This would be the perfect use case of Windows Up Down pretest calibration step to cancel out inherent environmental changes over time. Let's face it back-to-back tests among many other RPM targeting things, changing a turbo from a cast wheel stocker to a forged Billet wheel(effect of swap: less inertia lighter material faster spin capability less lag lower spool more power and Tq on the same fuel) is going going to take too long to have an accurate run because a few millibars of pressure priming the new turbo is going to have a direct effect on the result and this does not matter where you live in the world weather happens. helped to pick out the small gains and losses.
---
I plan to apply /mix your goodness and this,accurate temperature measurement to help with with accuracy of assment of modifications.


another conundrum in your presented understanding of diesel is that changing speed due to a change in drag will change the RPM/speed but the torque will stay steady, yet more RPM at the same torque value equals more horsepower regardless of fuel type.

Ps I'm not trying to fight with you I don't think anyone here is trying to fight with you please lose the aggression a community without aggression functions a lot better
__________________
1st gen cummins 91.5 dodge d250 ,HX35W/12/6 QSV
ehxsost manafulld wrap, Aero Tonto
best tank: distance 649gps mi 24.04 mpg 27.011usg
Best mpg : 31.32mpg 100mi 3.193 USG 5/2/20


Former
'83 GMC S-15 Jimmy 2door 2wd O/D auto 3.73R&P
'79 Chevy K20 4X4 350ci 400hp msd custom th400 /np205. 7.5-new 14mpg modded befor modding was a thing
87' Hyundai Excel
83 ranger w/87 2.9 L FI2wd auto 18mpg on the floor
04 Mitsubishi Gallant 2.4L auto 26mpg
06 Subaru Forrester XT(WRX PACKAGE) MT AWD Turbocharged 18 plying dirty best of 26mpg@70mph
95Chevy Blazer 4x4 auto 14-18mpg
04 Chevy Blazer 4x4 auto 16-22mpg


  Reply With Quote
Old 05-27-2020, 10:49 PM   #264 (permalink)
Cyborg ECU
 
California98Civic's Avatar
 
Join Date: Mar 2011
Location: Coastal Southern California
Posts: 5,785

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 66.42 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
Thanks: 2,155
Thanked 1,861 Times in 1,268 Posts
Quote:
Originally Posted by gumby79 View Post
... barge boards / Edgarwit external air curtains ...
Cheek spoiler? Dimple wings? Aerogils? Shoulder pads?

__________________


See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

  Reply With Quote
Old 05-31-2020, 08:57 PM   #265 (permalink)
Master EcoModder
 
Join Date: Nov 2017
Location: Australia
Posts: 496
Thanks: 36
Thanked 528 Times in 291 Posts
Latest videos:

Improving intercooler airflow. Not so relevant to ecomodders, but technique is based on measuring aero pressures.




Getting lowest drag - what you need to know about lift.



Making good aerodynamic belly pans (undertrays).

__________________
Modifying the Aerodynamics of Your Road Car

A really good book that should be added to the library of everyone working in automotive aerodynamics, as well as those making car aero modifications at home. - Rob Palin, former Tesla aerodynamicist
  Reply With Quote
The Following 2 Users Say Thank You to JulianEdgar For This Useful Post:
freebeard (06-01-2020), MeteorGray (06-01-2020)
Old 06-11-2020, 10:50 PM   #266 (permalink)
Master EcoModder
 
Join Date: Nov 2017
Location: Australia
Posts: 496
Thanks: 36
Thanked 528 Times in 291 Posts
Latest videos.

Using a pitot tube under the car. Seeing what is happening when you can't use wool tufts.



Using a pitot tube reference when measuring aero panel pressures, improving the accuracy of on-road surface panel measurements.



Does a box cavity actually increase pressure in the wake and so reduce drag? I find out.

__________________
Modifying the Aerodynamics of Your Road Car

A really good book that should be added to the library of everyone working in automotive aerodynamics, as well as those making car aero modifications at home. - Rob Palin, former Tesla aerodynamicist
  Reply With Quote
The Following 2 Users Say Thank You to JulianEdgar For This Useful Post:
freebeard (06-12-2020), MeteorGray (06-12-2020)
Old 06-12-2020, 01:10 AM   #267 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 16,059
Thanks: 4,213
Thanked 5,404 Times in 4,302 Posts
You keep busy. And that's not even counting the speaker enclosures.

I only found the time for the third one. There exists a picture that aerohead posts occasionally (that I can't find via Search). His friend in the 1980s had a VW camper that he drove to Mexico one a year that had a conduit and boat wrap open-ended boat tail — a bigger cavity than the one you tested. There was some claim associated with it.
__________________
.

Who controls the memes
Controls the Universe

_________________
  Reply With Quote
Old 06-12-2020, 01:31 AM   #268 (permalink)
Cyborg ECU
 
California98Civic's Avatar
 
Join Date: Mar 2011
Location: Coastal Southern California
Posts: 5,785

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 66.42 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
Thanks: 2,155
Thanked 1,861 Times in 1,268 Posts
Your box cavity pressure measurements are interesting and encouraging, but I think your specific build might be part of the reason you got quite different results than Ali. Ali observed in his article that the effect on drag was very sensitive to other mods. There was a lot of "interdependency" (his word) between the cavity, the difuser, and wheel well covers and such. You mention that in your video, too. But your tested design is radically different from Ali's in several ways that quite possibly matter a lot. Ali's final design was much smaller and was not an extension of the side, top or undercarriage body lines. Here is the final optimized box cavity from Ali's Audi A2 test subject:



Remember that he also claimed that the carefully optimized cavity was how he was able to get even more drag reduction through a 2 difuser.

Ali presented this research at Coventry University on October 19, 2011. I downloaded it on March 29, 2012 when it was still fully available on the conference website without a password. I don't see the 2.3% drag reduction claim in the slides detailing the box cavity. I am not saying he did not make the claim, but I don't see it. Which slide is it on?
__________________


See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.


Last edited by California98Civic; 06-12-2020 at 01:41 AM.. Reason: complete dates and correct two typos
  Reply With Quote
Old 06-12-2020, 01:38 AM   #269 (permalink)
Master EcoModder
 
Join Date: Nov 2017
Location: Australia
Posts: 496
Thanks: 36
Thanked 528 Times in 291 Posts
Quote:
Originally Posted by freebeard View Post
You keep busy. And that's not even counting the speaker enclosures.

I only found the time for the third one. There exists a picture that aerohead posts occasionally (that I can't find via Search). His friend in the 1980s had a VW camper that he drove to Mexico one a year that had a conduit and boat wrap open-ended boat tail a bigger cavity than the one you tested. There was some claim associated with it.
I was surprised by a couple of things with box cavities.

1. How low the gain was in the wind tunnel tech presentation that people quote - just 2.3 per cent on the Audi A2. I had assumed from people's comments that it would be higher.

2. That I could actually measure a change (improvement) in wake base pressure with the very large box cavity I trialled on the Insight. But that change, as I described in the video, is very small in terms of drag force - so the small reduction in Cd with the A2 (even with its much bigger wake area) makes sense.

But for vehicles with really large wakes, it could be beneficial. Otherwise, separation edges are easy and cheap to add.
__________________
Modifying the Aerodynamics of Your Road Car

A really good book that should be added to the library of everyone working in automotive aerodynamics, as well as those making car aero modifications at home. - Rob Palin, former Tesla aerodynamicist
  Reply With Quote
Old 06-12-2020, 02:19 AM   #270 (permalink)
Master EcoModder
 
Join Date: Nov 2017
Location: Australia
Posts: 496
Thanks: 36
Thanked 528 Times in 291 Posts
Quote:
Originally Posted by California98Civic View Post
Your box cavity pressure measurements are interesting and encouraging, but I think your specific build might be part of the reason you got quite different results than Ali. Ali observed in his article that the effect on drag was very sensitive to other mods. There was a lot of "interdependency" (his word) between the cavity, the difuser, and wheel well covers and such. You mention that in your video, too. But your tested design is radically different from Ali's in several ways that quite possibly matter a lot. Ali's final design was much smaller and was not an extension of the side, top or undercarriage body lines. Here is the final optimized box cavity from Ali's Audi A2 test subject:



Remember that he also claimed that the carefully optimized cavity was how he was able to get even more drag reduction through a 2 difuser.

Ali presented this research at Coventry University on October 19, 2011. I downloaded it on March 29, 2012 when it was still fully available on the conference website without a password. I don't see the 2.3% drag reduction claim in the slides detailing the box cavity. I am not saying he did not make the claim, but I don't see it. Which slide is it on?
The percentage change can be worked out from the bar graph. Cd = 0.215 with mods up to box cavity, Cd = 0.210 after box cavity. A 2.3 per cent reduction.

It's a very small change in drag. What I measured was also a very small change in drag, so I can't see how you can say that I "got quite different results than Ali". Given the different size wakes, I'd say they're in the same ballpark.

Without further evidence, I'd say that box cavities - especially on cars without large wakes - probably aren't worth pursuing... certainly not as first steps in drag reduction, anyway.

__________________
Modifying the Aerodynamics of Your Road Car

A really good book that should be added to the library of everyone working in automotive aerodynamics, as well as those making car aero modifications at home. - Rob Palin, former Tesla aerodynamicist
  Reply With Quote
The Following User Says Thank You to JulianEdgar For This Useful Post:
MeteorGray (06-12-2020)
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com