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Discussion Starter · #42 ·
What's wrong with the throttle cable? I modded my honda APP sensor to fit my 240sx throttle cable as did speed academy for their throttle body.

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The OE cable was too short to reach the TB. I ordered one for a later Supra model that's 5" longer. The barrel that inserts into the throttle pulley is a little too large but that's easily fixed.
 

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Discussion Starter · #44 ·
Dyno time.

After a few teething issues the K24 is running well in its new home. The torque curve is quite different than the inline 6 cyl!

I'll upload video of a run when I figure out how to get it off my phone :lol:



[video=youtube;k7UdSB87I6c]

 

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Discussion Starter · #45 ·
Track day update: Road Atlanta 12-6-19. Video will be added when iMovie stops crashing on my laptop.

Executive summary:
1. The car drove onto the trailer under its own power after 5 sessions.
2. Oil pressure (65psi hot at speed, 33 at idle) and coolant temps (180-190) remained steady all day.
3. With a couple of clear laps during the final session it ran its fastest lap ever at RA: Hand-timed 1:43.9
4. The cars weighs 2340 lb with no driver and the weight distribution is 50/50. Now I have to find a way to increase front grip!
5. The transmission has a big gap between 2nd and 3rd gear that was not as evident with a torquey 6 cylinder.



Video of the 4th session: Never got a clean lap.

<iframe width="560" height="315" src="
" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
 

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Discussion Starter · #46 ·
First race weekend with the K24. Road Atlanta Champcar.

Executive Summary:
1. An AFR problem was solved and the car ran great.
2. I knew we were in trouble when the first driver indicated a low fuel warning light only an hour into his stint. The car stumbled coming out of T10 and he dove into the pits where Nobody was ready to fuel the car. Mike and I got suited up as quickly as possible and fueled the car (only 9 gallons), we threw a new driver in and somehow managed it all within 5 minutes.
3. The new strategy was 1-hour stints.
4. Through a series of lucky breaks (Red Flag, FCYs, terrible conditions) we managed to hover in the top 10, and even up jumped to third place late in the race.
5. We ended in 8th OA, 2nd in class B, and the car drove onto the trailer... WIN!!

A few photos from the weekend...





 

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Discussion Starter · #47 ·
It was a challenging weekend at Road Atlanta AER race. One week after the snow race at Road Atlanta we were back there again with America Endurance Racing.

A lack of oil pressure kept us from qualifying Friday. Fortunately I noticed this in the pits at idle. We spent the afternoon dropping the front suspension and oil pan to find that the oil pickup pipe that I welded together broke just above the pickup. Mike welded the pipe back together and we gooped up the oil pan - unfortunately it was difficult to get the surface of the block clean before installation and we ended up with an oil leak Saturday morning.

The good news was that we got 40+ laps in before the leak got too bad to continue. The car turned a 1:42.9 with me driving - more than 4 seconds faster than I've ever been around RA. That lap is somewhere in the following video. I can't wait to see what a good driver can do with it.


It may be time for Grumpy 2.0

Damage from a shunt in T1



Splitter arms - slightly bent



Balancing the damage f/r



 

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Arouse the DAMPFHAMMER!
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The good news was that we got 40+ laps in before the leak got too bad to continue. The car turned a 1:42.9 with me driving - more than 4 seconds faster than I've ever been around RA....
These are very good news revvhappy! I really liked how the car is going in the video, where one can see the advantage of an wider engine speed bandwidth on power. Very good (y)! Sorry for your visit in the gutter and the damages on your chassis and engine. Grumpy 2.0 sound nice and made me curious what it will be :D?
 

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Discussion Starter · #49 ·
I have a spare Supra chassis in my driveway. Now that the K24 concept is proven to work I'll start with a new chassis and incorporate everything I've learned over 6 years of racing. The engine, drivetrain, and suspension will be swapped to the new chassis, and a fuel cell will be added. The Supra chassis is strong and just happens to function very well in endurance racing.
 

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Discussion Starter · #51 ·
A few updates since the last race:

1. Exhaust
2. Power
3. Oil pan

1. Champcar opened the rules a bit and I'm taking advantage. We can now use any exhaust for free as long as it was OEM on a car in their list of legal vehicles. The Honda S2000 comes from the factory with an amazing long-tube "header" - it takes a little effort but can be made to fit the K24. The #1 and 4 exhaust ports line up exactly with a K24 head but the #2 and 3 ports are closer together on the F-series engine. So... cut the flange off each exhaust, heat and bend the S2000 #2 and 3 pipes to match the K24 flange and weld it back together. The size and length of the primary tubes allow much greater flow, and it all tucks nicely in the chassis. A full 3" exhaust runs to the rear of the car.





2. As I mention early in this thread, I've never been happy with the dyno numbers and especially in the midrange. A friend of mine with a KMiata swap had his car tuned by a different shop in the Atlanta area and his numbers with a similar set-up to mine were incredible. I took my car to the same shop and 2 hours later he had found my missing power. It turns out that there is a problem in the Megasquirt code in the K24 program that is related to ignition timing. Using a second "auxiliary" timing table he was able to add 20 degrees of additional advance and the engine came alive, gaining 40-50 hp and lb-ft from low to mid rpm. The change is amazing.



3. The steel oil pan worked adequately for a couple of races but the warping from welding was creating constant oil leaks. Touge Factory introduced a front sump oil pan for 240sx K24 swaps and it looked like it might fit the Supra.



I had to move the engine forward 3" but it seemed worthwhile to get a good oil pan solution. It's a beautiful piece but ultimately I had cracking problems on the welded seams within 4 hours of track time with 2 pans that they sent me. Oil leaks were becoming very frustrating, then KPower (formerly KMiata) finally released my solution - a pan for a BMW E30 Kswap. It's a very similar front-sump design to the TF pan and holds 7 qts of oil. It fit perfectly in the space I had. It completed a track day and 11 hours of racing last weekend without issues.





The results of all of this progress? A fast race car! Even with a clutch that didn't work for the final three hours (we used 3rd gear only) the car finished 2nd overall and 1st in class at Barber Motorsports Park.



An hour of my stint before the clutch broke.

 

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Discussion Starter · #52 ·
To get clearance for a coolant hose under the intake I removed the water pump boss that held the OE serpentine belt tensioner. The KMiata pulley simplified the belt to the crank, alternator and water pump, but the "tensioning system" has never thrilled me. When the belt gets loose the intent is to space the alternator away from the water pump with washers.

I stared at pages of belt tensioners all weekend and finally came up with a fairly simple solution. I used 1/8" steel plate and two of the OE motor mount bolt holes. The plate is slotted for adjustment, as is the idler which is a timing belt tensioner pulley from the original Toyota engine. It's not spring loaded but an adjustment should last an entire race. I welded the idler bolt from the back and ground it down for clearance.





 

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Arouse the DAMPFHAMMER!
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To get clearance for a coolant hose under the intake I removed the water pump boss that held the OE serpentine belt tensioner. The KMiata pulley simplified the belt to the crank, alternator and water pump, but the "tensioning system" has never thrilled me. When the belt gets loose the intent is to space the alternator away from the water pump with washers.
Yery nice solution. Are there any critical vibrations seen when the engine is running on that thin bracket? Does the big washer touch the bearing sealing or is there a smaller washer below the big to clearance there?
 

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Discussion Starter · #54 ·
Both are excellent questions. I'll answer #2 first - the bearing in the idler pulley is large diameter to accommodate a slotted internal sleeve. I have a smaller washer that sits only on the internal slotted portion. I also bought a much lighter nut to replace the one in the photos and added a lock washer.

To answer question 1: I have no idea yet about the forces on the plate. The steel seems thick enough to avoid excess flexing and the primary force on it will be parallel to the edge of the metal. I'm hoping that the width of the roller and "elastic" properties of the belt will keep the forces straight and dampened. Only time will tell.

103530
 

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Discussion Starter · #55 ·
I now have data to answer question 1 above.... The belt tensioner was a disaster at a race this weekend.

Executive summary:
1. The idler wheel I used was not quite wide enough to cover the full width of the belt (about 1.5 ribs were not supported).
2. After 4 hours of running the unsupported area of the belt separated and whipped around, knocking the VTC connector off of the solenoid and damaging the crank sensor wires.
3. One hour later the bracket broke where I welded the bolt for the idler wheel. We had to shim the alternator away from the water pump housing to get tension on the belt again and ran the next 6 hours without incident.

We lost about 20 laps in the pits due to these issues and finished 18th overall and P3 in class. The car had the speed to win, setting the fastest lap of the race (starts at 20:50 in the video below).

I have a K24Z3 water pump housing on the way. With small modifications it will bolt on and uses an alternator that pivots to allow adjustment.

 

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Arouse the DAMPFHAMMER!
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I have a K24Z3 water pump housing on the way. With small modifications it will bolt on and uses an alternator that pivots to allow adjustment.
Sorry for your mess with the belt, but that sentence has the right information. Your car ist most competitive! YEAH! Thanks for the video.
 

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Discussion Starter · #57 ·
GB2 is alive:



After many years, miles, and contact with other cars and walls Grumpy was ready to retire. Suspension and drivetrain were swapped to the new chassis. Upgrades include a 22 gallon fuel cell and a halo seat. I'll also redesign the front aero based on the OE bumper.








The maiden voyage was a Champcar race at Carolina Motorsports Park where I had some brake pad and suspension (broken strut) issues. The car was running in the top 3 before the problems.

After the race I had surgery in July that will keep me hobbled for 6 months, but the car is visiting DIY Autotune for some MS3 diagnosis. I can't share yet what they are working on but the results are nice.

 

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Discussion Starter · #59 ·
In the Champcar series we are limited to 18.1 gallons of fuel (2 gallons more than the OE tank), and we should be able to get 2-hour stints with that at most tracks. There are currently displacement blocks in the cell so it can't take more than 18 gallons. I can remove them for other series to get the full 22 gallons.
 

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Great to hear that DIY Autotune was able to look at the car. Hopefully this is in regard to updating MS3 code for the K series? I am starting a K swap into an MR2, and despite the very little info on the web regarding megasquirt K series builds, I settled on MS3+MS3X because that's what I run in my Chevelle and we put a MS3 PNP in my dad's Grand National.
 
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