Author Topic: Belly Tank Build Diary  (Read 367560 times)

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Offline Stainless1

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Re: Belly Tank Build Diary
« Reply #675 on: February 06, 2024, 05:01:24 PM »
Mike minor suggestion... upper shock mount might be stronger with a gusset...  :cheers:
Stainless
Red Hat 228.039, 2001, 65ci, Bockscar Lakester #1000 with a little N2O

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #676 on: February 06, 2024, 05:27:46 PM »
Mike minor suggestion... upper shock mount might be stronger with a gusset...  :cheers:

You know Woody said the same thing, I guess that I will add a gusset. 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #677 on: February 13, 2024, 11:39:54 AM »
Going forward this shall be known as the Stainless-Woody gusset.

Offline Stainless1

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Re: Belly Tank Build Diary
« Reply #678 on: February 14, 2024, 12:53:30 AM »
Mike, I did my best but failed... trying to resist mentioning I'm familiar with the 'Stainless Woody" but never needed a gusset...  :roll:  :laugh:  :laugh:
 :cheers:
Stainless
Red Hat 228.039, 2001, 65ci, Bockscar Lakester #1000 with a little N2O

Offline salt27

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Re: Belly Tank Build Diary
« Reply #679 on: February 14, 2024, 03:17:33 AM »
Mike, I did my best but failed... trying to resist mentioning I'm familiar with the 'Stainless Woody" but never needed a gusset...  :roll:  :laugh:  :laugh:
 :cheers:

I'm guessing this is from hands on experience.     :laugh:

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #680 on: February 24, 2024, 11:28:54 AM »
I worked with Jerry Magnuson and TRD on a "bypass problem" with Eaton supercharger kits (back in 1997-98).  I found the transition from "spinning blower in vacuum" to "throttle open" would buck and/or stumble the application of throttle.  Jerry's system had a vacuum line controlling the bypass valve, and by installing an .022" restriction in the vacuum line, the "reboost" was ramped in over about 800 milliseconds, which the ECU could handle easily.

When the blower is spinning, and you close the throttle, it acts as a "booster" vacuum pump in addition to the engine capacity.  Reopening the throttle can drive the measured airflow beyond the capability of the ECU (momentarily.)  Using a portable oscilloscope, I was seeing a 5 volt circuit exceed 5.24 volts (where 4.9 volt was the maximum useable signal in the software).

It all reminds me of the "method" needed to test supersonic airplane design.  It is impossible to blow air supersonic with a fan, but if you put a big enough vaccum tank behind it, atmospheric air will easily go supersonic into that big "hole".  A blower in front of a vacuum pump, becomes part of the vacuum tank when you come off the throttle.  Crazy stuff happens when you reopen that throttle.

If yours has that small vacuum line controlling the bypass, you might try a .023" wire welder tip to see if it helps your throttle control.  I don't actually know what your control system is, of course, but thought I could share my ancient history "memory".  We wound up installing that little restrictor in thousands of kits and ended the complaints.

Thank you very much for that suggestion.  My blower bypass valve is no longer controlled by the ECM, I simply plumbed the blower bypass valve dashpot to the intake after the blower.  The other side of the dashpot is vented (through a filter) to atmosphere.  I was contemplating using "bucking" pressure on this side of the dashpot by installing a needle valve that I could adjust to dampen the response of the bypass valve.  An .023" jet will give me a starting point.  I am always amazed by the "been there done that" help that pops up on this forum.

I appreciate the knowledge gained from racers contributing to this forum.  I would like to have some adjustability with the supercharger bypass valve.  Looking for various "jets" to use for this purpose I remembered that I my nitrous system came with a variety of jets.  I have jets from .018" to .062" which will be a useful range.  The next step was to machine a holder for the jets. While measuring the jets I found the "stem" to be approximately 3/16".  I tried them on a 3/16" compression fitting in place of the ferrule and they fit great. 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #681 on: February 24, 2024, 11:29:47 AM »
A photo of the jet installed in the fitting. 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #682 on: February 24, 2024, 11:31:45 AM »
I plumbed the jet holder to the dashpot with short section of braided hose so that the jets would be easy to change at the track.  I will add a foam filter to protect the jet from dirt and debris. 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #683 on: March 01, 2024, 02:47:34 PM »
To protect the restriction jet from debris I covered the jet assembly with a microphone cover typically used on boom style microphones.  The foam cover fit perfectly. 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #684 on: May 06, 2024, 02:53:21 PM »
We ran the ECTA mile this past weekend in Arkansas.  The new rear suspension with coil springs and adjustable shocks was a handful.  I started with 5 clicks (of 18) from full soft on both compression and rebound.  The car was almost undriveable with so much twisting under acceleration.  I moved up to 10 clicks then 13 and it was better.  The best run was 204+ in the mile, note that I have been 210+ on this track last year.  That was spraying the NOS for the last 1/4 mile for the 204 pass.  The 210 pass was without NOS.  The restriction that I put in blower bypass valve did help, I did not break the tires loose at all after shifting.  I think that it is a traction issue, the 210 run had a tailwind while the 204 run was against a headwind.  The data shows about the same RPM through the traps for both runs, or my clutch is slipping.  I have a couple of inputs left on my data logger so the plan is capture tire speed for the front and rear wheels.  That should help figure this out.  I was almost at the rev limiter (6,500 rpm) on both runs, with 2.48:1 rear gears.  I switched to 2.22:1 rear gears and went slower (199+).  I plan to do some testing at the dragstrip with the original rubber springs.  Going fast is harder than one would think. 

Offline ronnieroadster

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Re: Belly Tank Build Diary
« Reply #685 on: May 06, 2024, 04:51:31 PM »
The time slip shows your engine was still pulling from the 3/4 to the mile with the 2:48 gear. From my experience comparing speeds gained in the final 1/4 of the mile most will gain 10 to 15 MPH in the open wheeled class such as yours and the class I run with an engine that makes good power. The reduction in speed with the 2:22 gear could simply be the engine is no longer in its happy torque range trying to push into the wind.
 Ronnieroadster.
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Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #686 on: Today at 08:31:48 AM »
I feel the need for more data to determine where the slippage is in this application.  I have the data logger on the car and there are additional inputs that can be configured for "frequency" signals.  The data logger allows me to apply the math to convert the frequency to MPH.  I decided to add Hall Effect sensors to the front and rear tires so the tire speed can be logged separately.  I really like Hall Effect sensors since they have a reliable square wave output.  I am using a reverse biased gear tooth sensor (GT1) that is available from Ebay for $25.  These sensors have a magnet inside the sensor and detect ferrous metal.  With properly configured target they and operate reliably from zero speed up to 20kHz.  I decided to use two pulses from the driveshaft at the transmission.  I machined a wheel that can be attached to the drive shaft yoke that is wide enough that the sensor will still work properly as the drive shaft moves in and out with the suspension movement. 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #687 on: Today at 08:34:26 AM »
The sensor for the front wheel was much easier.  I used the same sensor with the "spokes" of the brake rotor as the target.  Using a simple hex brass spacer the sensor was attached to the inner wheel disk. 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #688 on: Today at 08:43:34 AM »
A very "interesting" car that pitted beside us at the ECTA event this month.  It is a 1959 Renault with an 85" wheelbase.  It is powered by a 3.8L Buick V6.  The engine had a large single turbo and the owner claimed 1,100hp on the dyno.  The interesting thing was that the output of the turbo was connected directly to the throttle body.  There was no intercooler.  He ran water (no methanol) injection before and after the turbo.  He showed me data from a run with over 30pounds of boost and the manifold temperature was only 140 degrees F.  His goal was 200mph in the 1/2 mile.  He ran multiple passes at 183mph with a best of 184mph.  He was plagued with traction issues the entire event.