Toyota Celica Supra Forum banner

1221 - 1233 of 1233 Posts

·
Registered
Joined
·
38 Posts
One of those times where the car's not the only thing making skid marks, eh, Billy? You two sound like you're having a blast! I can't wait to really drive my Celica. She's getting a new-to-me rear end put in as we speak. =)
 

·
Super Moderator
Joined
·
10,544 Posts
I have time, energy, and passion for these projects, so why not. There are worse hobbies to have :)

I did find a kink in the left frame rail in front of the crossmember today. It doesn't affect the alignment, but will affect the position of the front air dam.

You could actually open up the inside of that rail, from the wheel well. If you remove this panel (by drilling out the spot welds)...
14105


Underneath that one is another piece of 18/20 gauge sheet steel, the piece that forms the front half of the wheel well. You can see it here with all of these parts, including the rail, seperated...

You could cut out a an access hole through the wheel well piece to get unrestricted access to that dent and then be able to hammer it out fully. Then weld that first piece above there back on and you shouldn't be able to tell you were ever in there if you do it right (but race car, so probably don't need to finish it that nicely).

Here's the whole post where I took apart a rusty front end to fix the battery acid leak these cars suffer from...

Photobucket is bandwith limiting everything so they are probably blurry, you should be able to right click on the images and open them in a new tab to view them at full resolution.
 

·
Registered
Joined
·
1,291 Posts
Discussion Starter #1,223
After spending a weekend rebuilding the splitter/airdam and hammering the bodywork and chassis until a few bolt holes lined up the Supra was presentable enough for a track day. The hood barely lined up with its pins and the hatch took a bit of effort to close.




GB2 is under construction with a fuel cell and halo seat (thanks to DHardy), so I now call this car "Grumpy Mule" - a test bed for bad ideas that can be transferred to the new chassis. With the header in place I took the opportunity to open the rest of the exhaust to 3" with a 2.5 to 3" adaptor right after the header and a cheap Amazon resonator. An hour of welding later I had a single long system from the header back connected with a v-band... more on this later. I didn't have time to tune for the header so I made a note to watch AFRs during the first session.



The Just Track It event at Road Atlanta was a nice day with temps in the 80s. Session 1 was a shakedown to make sure that all the mods to move the engine forward didn't break or fall off. Success! Mule ran great and the AFRs and oil pressure were solid.

The second session started with a bang... literally. As I was leaving pit lane and accelerating up the hill I was hit with a wall of loud noise - definitely exhaust-system-related. I had to make it all the way around the track thinking about all of the possible issues it might be while the AFRs were off the charts. Broken weld? Broken header? After making it back to the paddock I could only laugh when I figured out the problem - the exhaust system had disconnected from the header. While I was mocking up and welding the exhaust system the header was bolted to the engine, and in my happiness at finishing the welding I tightened the Vband without ever welding one of the the Vband collars to the header. It was merely held there by a tight "friction fit" during the mock up, which lasted an entire session! The good news was that the exhaust system is so well supported that it never touched the ground and the entire Vband including collars was still in place. I couldn't find a welder so Kevin lent me a sacrificial ratchet strap and in typical Lemons fashion I lined everything back up and pulled the system into the header. The ratchet strap held up nicely for three more sessions :)

[video=youtube;YZozh2v1ggs]


Everything ran smoothly after that. People were saying the track was getting greasy but the Supra was running 1:43 - 1:44 with no traffic. I'm quite happy with that. Next on the agenda is a trip to the dyno and replacing the power brakes with a manual setup.
 

·
Registered
Joined
·
1,291 Posts
Discussion Starter #1,224
If you watch the video in the last post you can hear the big gap in ratios between 2nd and 3rd gear - it's painfully obvious going up the hill out of T10b and through T5. The inline 6 Toyota engine had the torque to make this gap a non-issue. After seeing a friend's Miata Kswap dyno graph I was drooling... if my engine could make that torque it might be the answer, and I've always believed that something was missing in my torque curve. Our setups are nearly identical now (stock K24a2, header, 3" exhaust) so it was time to get some answers.

The original tuning with the OE header was done on a Dynapack dyno and Andrew's Miata was tuned on a Mustang roller dyno but the shape of the curves is the important part.

For comparison purposes here is the original 6 cylinder dyno chart on the Dynapack. Oodles of torque from low rpm but runs out of steam at high rpm (and burns a ton of fuel doing it).





My tune with the OE header and 3" exhaust (Dynapack) vs Andrew's set up (Mustang). The Dynapack shows revs from 4-8krpm but you can see the sagging curves. Andrew's K24 plot shows a plateau of torque and a linear HP curve.






With this information I decided to use the same tuner as a control to identify any issues my car might be experiencing. Below is a graph with a baseline run on the old tune (dotted - which was not tuned with the header) and the new tune with header (solid lines). Fairly dramatic changes in the midrange (40-50 lb-ft)! Something was creating a misfire after 6500rpm but nothing in the datalog is weird so I think it might be a coil or plugs going bad.



I hope that this newfound torque will close the gear ration gap. Can't wait for another RA track day in a couple of weeks.
 

·
Super Moderator
Joined
·
10,544 Posts
Thats quite the improvement, and quite the flat torque curve over a long power band for a 4 banger, impressive.
 

·
Registered
Joined
·
1,291 Posts
Discussion Starter #1,226
The I-VTEC is an amazing system. The variable intake cam timing is the key too all the torque. It still doesn't feel like if has the grunt of the 6m Frank that I pulled out, but the extra hp on top is noticeable.
 

·
Registered
Joined
·
1,291 Posts
Discussion Starter #1,227
More Mule Testing: Manual Brakes.
The intent is to have better feel without adding too much effort (and lose a few pounds).

Out with the old. Brake booster and 15/16ths master cylinder.




The new master cylinder is externally identical and has a 7/8ths bore. Sourced from the same year Celica and I found 2 new on clearance at Rockauto for a total of $15. I made a large plate of 0.20 aluminum to add some strength to the firewall then built a smaller mount plate for the MC. The Supra reservoir is a direct fit.




I mounted the MC about 1" higher than the OE position. Had to cut about 1/2" semi-circle at the top of the firewall hole to clear it.






The MC mount screws are countersunk so the 2 aluminum plates and the MC are one solid unit.




In with the new. The entire setup is about 4" back from its original position which affected the brake lines to the proportioning valve.




With a little "massaging" the front (top) brake line made it to the new position but the rear had no chance. While scrounging in the junkyard Wednesday I came across a 1990 Cressida and noticed the brake lines were longer. $5 later I had something that might work. It took a bit of bending but made it into place.




With the MC raised an inch I had to modify the brake pedal. I welded in a piece of 1/4" steel and drilled a new clevis hole. This brake pedal leverage ratio is already high and I have no idea how much I changed it, but that's what testing is for.

 

·
Registered
Joined
·
13,112 Posts
Wow - they found 50 ft/lbs at 4500rpm?! That's going to be a spectacular change for the drivers!

How did moving the engine forward turn-out. Any noticeable downside on the car's willingness to rotate?

Great work as always and awesome to see the progress.

--billyM
 

·
Registered
Joined
·
1,291 Posts
Discussion Starter #1,229
From the first real dyno runs of the K24 I thought something was missing. I did a TON of reading about the new engine and it should have made significantly more torque from low rpm. It did pick up 20-30 hp over the 6M and still went 4 seconds faster at Road Atlanta. I replaced the VTEC solenoid, checked the oil screens for the VTC, and double-checked every timing mark and sensor. When my friend had his K-swap Miata tuned a couple of weeks ago (very similar setups with Megasquirt) and I saw the torque curve I wanted to see if it was my tune or something wrong in my wiring, or a bad sensor, or ??? Without that data point it would have been difficult to track a problem. There seems to be a bug in the Megasquirt programming that affects relative crank timing and this tuner had figured out the issue. There is still another 10hp waiting above 6500 - I just have to figure out why the misfire is happening.

I can't feel any change in the handling of the car with the engine moved forward. Most of the engine weight is still behind the centerline of the front wheels and I would guess that the weight distribution is probably 52-48 at the worst. It is a joy to drive fast on a track with the 255 rubber. The new chassis will have a little more weight in the rear with the 22 gallon cell and its cage.



The new halo seat will add a bit of weight also but the additional safety factor is worth it.

 

·
Registered
Joined
·
3,373 Posts
I'm honestly amazed that there was a Cressida in your junk yard. Haven't had one of those around here in years.
 

·
Registered
Joined
·
1,291 Posts
Discussion Starter #1,231
The body was in great shape. I have no idea what shape the 7m was in. I'll be it doesn't take much to total a 30 year old car these days.
 

·
Registered
Joined
·
3,373 Posts
Oh it doesn't even have to get totaled to hit the junk yard, lots of people hitting hard times right now. Any little part goes out on it, they can't make rent, whatever, boom off to the junk yard.
 
1221 - 1233 of 1233 Posts
Top