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Author Topic: Belly Tank Build Diary  (Read 95194 times)
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Mike Brown
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« Reply #330 on: October 19, 2018, 07:42:33 AM »

Last night I was at Kilkare dragstrip for a test & tune session.  It was a wonderful cool evening.  I was able to get in three 1/4 mile passes.  The changes to the car all seemed good by the seat of the pants feel and the time slips.  The additional link definitely stiffened up the chassis eliminating the bouncy feel during shutdown.  The smaller clutch master cylinder gave me better feel of the clutch eliminating the digital feel while still insuring complete disengagement.  The engine was making significantly more power I assume do to higher boost.  I had the highest top speed (115.12) and lowest ET (12.1891) of all my test & tune sessions.  This car is obviously not a dragster with a 2.48:1 rear gear so I roll off the starting line and do not press the throttle to the floor until after the clutch is fully engaged.  For the first time the shift light came on in second gear and I had to shift into third gear.  I have not reviewed the data from the logger but I would expect to higher boost since properly adjusting the boost bypass valve and we will see if the MAF sensor is happy with the new scoop.  The staff at Kilkare is tops in my book.  They are professional and run an orderly and safe event.  The data from the $25 test & tune session is invaluable to me. 


* Kilkare Timing Slip small.jpg (188.12 KB, 756x1008 - viewed 79 times.)
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tauruck
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« Reply #331 on: October 19, 2018, 11:46:03 AM »

Nothing you do in LSR is wasted time or energy. cool
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Mike Brown
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« Reply #332 on: November 04, 2018, 08:17:36 PM »

I attached a photo of the data from the last test & tune session at Kilkare drag strip.  The middle graph is the MAF sensor signals which are very choppy.  The tune up definitely needs to be changed from MAF to speed density.  Note that at wide open throttle the ECU does not use these signals for fuel or timing.  The bottom graph is the acceleration.  The acceleration rate slows down at about the 1:39.5 mark, the rpms are still climbing at a fairly quick rate and I attribute that to traction issues as the tires are probably slipping.  I do not heat the tires up with a burn out as I would never get that opportunity in a mile event.  In the top graph I included three different signals.  The white trace is the throttle position.  You can clearly see taking off (40% throttle), shifting twice and shutdown.  The green trace is rpm.  The engine is about 3,000 rpm as I take off dipping to about 2,500 as the clutch engages and the car starts accelerating.  You can see the rpm climb through the gears.  I did not spend much time at full throttle in third gear so I think that the car will easily run quicker than 12 seconds in the quarter mile.  The light blue trace is the MAP signal.  Ambient air pressure is approximately 100 kPa so anything above that is supercharger boost.  The disturbing thing is that as the RPM climbs the boost drops off.  The most likely scenario is that the ribbed blower belt is slipping as boost increases.  The tuners at Weapon-X have suggested that there is not enough belt wrap on the blower pulley.  Their suggestion is to move the idler pulley closer to the blower pulley.  So I did pick up some boost by adjusting the blower bypass butterfly however there is still substantial amounts of boost (horsepower) to be gained by correcting this belt slippage issue.  My previous blower drives were all timing belt drives and I never had any belt slippage in that configuration.  There is not room for a conventional timing belt drive with a 2.6:1 overdrive ratio needed for this small blower so I will look to optimize the ribbed belt drive.  Without my AEM data logger I would not be able to diagnose problems like this, make changes then verify if the changes corrected the problem. 


* Kilkare 2018.jpg (440.92 KB, 1404x906 - viewed 62 times.)
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Jack Gifford
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« Reply #333 on: November 05, 2018, 01:13:17 AM »

That's a good  display of data logging usefulness.
If the shifts weren't so lazy, ETs would be in the tens! rolleyes
I don't understand why a timing belt blower drive of the same ratio wouldn't fit? Problem with minimum bend radius of toothed belt?
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Mike Brown
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« Reply #334 on: November 05, 2018, 07:46:47 AM »

Jack,

As always thanks for the comments.  Test & tune sessions for me have always been about getting some data in an effort to improve the mile performance.  I have always wanted to get data and not break any parts, hence rolling out easy waiting for the clutch to engage before applying full throttle and lazy shifts.  The 12 second quarter mile was a little exciting and I may try a little more aggressive driving without breaking parts. 

I am limited to not much more than an 8" crankshaft pulley due to my water tank construction.  The factory ribbed belt is 7.8" diameter with a 3" diameter blower pulley which gives me a 2.6:1 ratio.  The blower spins at 16,640 rpm with a 6,400 engine rpm.  I can find crankshaft pulleys for 8mm gearbelt pulleys (I would have to change to an aftermarket harmonic balancer) in that size however I cannot find a blower pulley small enough.  The crankshaft pulley would need to be reduced in width and custom blower pulley created.  The OEM blower pulleys are steel and pressed onto the shaft, no keys, pins or other driving components.  Aftermarket pulleys use a press on hub that the pulleys are bolted to much like when using a GMC type blower. 

There are two aftermarket systems that are too wide for my application that I may be able to modify.  I plan to make some changes over the winter in preparation for next year, I just haven't decided which way to go. 
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Jack Gifford
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« Reply #335 on: November 06, 2018, 12:51:20 AM »

I don't know about narrower, but I recently bought a 32 tooth 8mm pulley (3" wide belt). It didn't take me long to machine a hub for it to fit my crankshaft.
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Mike Brown
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« Reply #336 on: November 06, 2018, 07:43:46 AM »

With a little research I found that LSX Concepts has 8mm HTD upper and lower pulleys for $900 per pair.  The lower pulley requires an aftermarket harmonic balancer for $500 and the upper pulley requires the Lingefelter 10 bolt hub for $65.  The 8mm HTD belt is about $50.  In my application I would need to design and build the idler pulley for this system as theirs uses attachment points on the OEM water pump.  I don't have an OEM water pump.  At the modest boost levels that I am looking at I may try a Gates "green" belt with the idler pulley mounted closer to the blower pulley.  A trip to the drag strip for a test and tune session or a dyno session would let me know if this corrected the problem. 
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Stainless1
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« Reply #337 on: November 06, 2018, 11:33:00 AM »

Hey the nice part of that is "there is a solution...  it just costs time and money"  cheers
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Stainless
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MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
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« Reply #338 on: November 06, 2018, 11:54:14 AM »

Gee whizz, those pulleys are cheap as chips here.
Maybe I've got the wrong idea but I'll post a pic tomorrow.
Maybe you get lucky???.
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Mike Brown
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« Reply #339 on: November 06, 2018, 03:30:48 PM »

Gee whizz, those pulleys are cheap as chips here.
Maybe I've got the wrong idea but I'll post a pic tomorrow.
Maybe you get lucky???.

Thanks for the response, cheap as chips would make for a lucky day.  I look forward to your reply. 

Mike Brown
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