Belly Tank Build Diary

[kiwi belly tank]

No "oil rig" at all is preferable (see Wayno's P38 tank) but since you have a big one, all that tubing is pretty much a big air brake in the wrong place & the turbulence coming out the back of that is a mess. Enclosed the air will go around it rather than through it but it needs an appropriate windshield in front of it to direct the air around the opening otherwise it's a bigass scoop to nowhere. Behind that is also important, preventing the wake from crossing over in the low pressure area down the back of the tank will reduce turbulence. Contact Ron "Ronnieroadster" about his real word results. Your front end is also eating a lot of air.
I have no formal training in aerodynamics, in fact being dyslexic I dropped out of school at 15 but then got into race cars & hydroplanes & found I had a logical understanding of fluid dynamics & making $hit go fast. I had a aerodynamicist say to me looking at my work one time, "you can see the air"!
  Sid.

[Mike Brown]

Have you considered the type of dyno that uses rear wheel stud to drive it

I would much prefer a hub dyno however my tuner only has a chassis dyno.  I have been very pleased with my tuner. 

[Mike Brown]

A data log from a mile run at Blytheville Arkansas with the ECTA.  The blue line in the upper block is the rear tire speed and the white line is the front tire speed.  Much better data with the Hall Effect sensor on the tire verses the driveshaft.  You can the spikes where the rear tires spin compared to the front tire speed.  I believe that the math to convert the tire pulses to mph will need some minor adjustment but the relationship is telling even if the speeds are not 100% correct.  I included the throttle position (has the periods of flat lines at 100%) and the rpm.  The blower boost is still coming on strong after shifting but it is much better with the slower opening of the blower bypass valve.  Lots of good data, lots of rain and some water coming up between the cracks in the track after it dried up.  The Mickey Thompson DOT drag radials increased my 1/2 mile speed and did improve the traction overall.  I did not have my best event with a 204+mph run.  Eddie Presnull set a new track record of 271.084 in his Mustang (with a gigantic rear wing) so the track was good for some.  We will work on a few things and have back at it. 

[Stan Back]

. . . reminds me of years back when a friend showed me his chart for his Gas Roadster over on a soggy #3.  Fronts were at 120 and the rear at 163 right before it spun.

We never had any data to tell us something, but we learned how to spin a couple of times.  Damn that Notch.

[Stainless1]

. . . reminds me of years back when a friend showed me his chart for his Gas Roadster over on a soggy #3.  Fronts were at 120 and the rear at 163 right before it spun.

We never had any data to tell us something, but we learned how to spin a couple of times.  Damn that Notch.

Yep Stan, that proves you don't need data to spin....

[Mike Brown]

The reason I added the short panhard rod was that when turning on asphalt with a spool and slicks the rear suspension (Satchell style four link) allowed enough side to side movement that the shocks hit the frame.  When I switched to the QA1 shocks (expensive) I did not want their aluminum body to be dented.  Well as some on here predicted that was not a good choice.  The panhard rod did the job of preventing the shocks from hitting the frame however it did have an undesirable effect on the handling of the car.  The track has more and larger bumps than I originally believed.  the slight displacement of the rear axle as it went through the suspensions travel resulted in the car wanting to wander on the track especially at high speeds (over 175mph).  I removed the panhard rod and replaced with simple snubbers.  They are blocks of UHMW plastic that do not touch the frame (there is about a 1/4" gap) but will prevent excessive side to side movement, saving the shocks, when turning sharp corners associated with staging, pitting etcetera. 

[Mike Brown]

A view from the back showing the gap. 

[Mike Brown]

The supercharger boost was dropping off at the end of a run.  My tuner told me that the supercharger drive belt (6 rib MicroV) was slipping.  In my infinite wisdom I believed that this was due to the intake being a "bologna" sliced tube flush with the body.  The problem did not manifest itself on the dyno.  I surmised that air flowing across the inlet at speed was creating negative pressure at the intake.  I added a small scoop on the intake for this last event.  The problem was still there noticed by the dip in the MAP pressure (green line) so I will take my tuners advice and replace the belt. 

[ronnieroadster]

We use an 8 rib micro V belt no slippage at the close to max RPM the Whipple is rated for. So far top speed 229 at the Loring track 225 at Bonneville. Your tuner is right about the belt.
Ron

[Mike Brown]

I am evaluating the blower drive that is slipping.  I removed the 8 rib Micro V belt and found the peaks of the blower pulley polished.  Obviously the belt is bottoming out on the pulley without the wedging force that is needed for V style belts. 

[Mike Brown]

A photo of the old belt on the left and a new belt on the right.  The ribs are visibly smaller on the old belt than the new belt. 

[Mike Brown]

I will replace the belt but I question my use of a fixed tensioner verses a spring tensioner.  Researching the Gates website indicates that a spring tensioner is preferred.  I will ponder this a little before designing and installing a spring tensioner as there is so little room at the front of this engine installation for an off the shelf solution. 

[ronnieroadster]

I will replace the belt but I question my use of a fixed tensioner verses a spring tensioner.  Researching the Gates website indicates that a spring tensioner is preferred.  I will ponder this a little before designing and installing a spring tensioner as there is so little room at the front of this engine installation for an off the shelf solution.

  We use a spring tensioner with our 8 rib belt early on with the Whipple I tried only fixed type tensioners with mixed results. When i use a blower drive with V type belts or a cog belt the fixed tensioner works best.
Ronnieroadster

[Mike Brown]

I am always looking for ways to quantify data.  In my quest to figure out what is happening with the supercharger drive I did some research on the Gates website.  It is apparent that belt tension is critical on Micro-V belts.  Minimum tension on an 8 rib Micro-V belt after break in is 80 pounds.  I tensioned the belt at what I thought was a good tension then decided to purchase the Gates belt tension gauge (from Amazon for $30) to in fact verify the actual tension.  Much to my amazement the tension was only about 60 pounds.  So, for now I will still run the fixed tensioner but with the proper tension.  It is easy enough to check when prepping the car for a run. 

[ronnieroadster]

Minimum tension on an 8 rib Micro-V belt after break in is 80 pounds. So your going to make a break in fixture for the belts? Data sure works my data shows a spring tensioner allows us to get 18 pounds of boost turning 6500 engine RPM blower RPM just under max allowable. No slippage  equals lots of very fast speeds and records.