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4GMR2 Build

16035 Views 152 Replies 17 Participants Last post by  Sabertooth^2
What's the Eclipse missing? Traction, power at the rear, and weight balance.

So here's the build thread to focus on my 4G, mid engine, rear drive 2 seater build. 4GMR2. Sorry Toyota.

The car started life with Plain Jane around here, but after an unfortunate incident at the track which may or may not have been related to running 5W-20 while racing (don't do it), the engine decided it had enough of living. Plane Jane had life in the way, and so the car needed a new home. So I took over.

Credit where it's due, here's his build thread.

It was a sad day for Plane Jane, and a day with mixed feelings for me, taking over a friend's car. I still have a hard time referring to it as anything but his.
Here it was, leaving to a new life.

This is where I took over. The end of his build thread, minus a good engine. The cylinder walls are scored, the bearings are shot. It has no oil pressure.

Quickly, it found space with a friend nearby

And had fun watching the stripper take it all off

Then getting forked out in the parking lot

But here's where the car sits now.

Today was a productive day, with the seats coming out, gas tank, fuel straps, seats, some trim, center console, rear subframe, evap components, fuel filler neck, the wrappers of 3 Cliff bars, and some other stuff, such as the mouse poop from 3 Cliff bars which I may have been rolling around in (hint: yeah I was before I knew it was there)

So, next up, I've got to pick up some blades, and I'll be cutting out the rear end sheet metal. Everything between the frame rails is coming out.
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Good video!
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Hey Sabertooth, Gingium from YT is copying you! Haha. A friend of mine sent me one of his videos, he's building a mid engine 4g63 4G. Better show him who's in charge haha.
First update in a while. I got the car corner weighted today.

48:52 weight distribution, and best of all... About 800lbs lighter than stock. 2749lbs (with my laptop, a portable speaker, and few insignificant things inside).

Next up, math, measuring, and custom coil overs.
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Hey Sabertooth, Gingium from YT is copying you! Haha. A friend of mine sent me one of his videos, he's building a mid engine 4g63 4G. Better show him who's in charge haha.
He claimed originally to have the first... I think I ruined some of the fun for him when he found out it isn't.

But I gave him a good set of pictures and instructions to work from in case he wanted stuff to reference. So far, his build seems to heavily be going the same method
From a bunch of math then sim testing in Assetto Corsa, I settled on 4k front 6k rear spring rates. It's a bit softer than a 10k front 6k rear setup, which I feel is likely too stiff for my local track anyway. Time will tell. But even in digital with those new rates I dropped half a second off my best lap time, out of practice.

what I was looking at was the spring frequencies. They take in account the wheel rate (calculated from spring rate and geometry) and mass. I aimed for the flat ride principal, which is what you tend to find used by most manufacturers. 15-20% being the goal. I settled on a match giving 17.4%. In the future I could always change the springs anyway to fine tune, but staying mildly softer and paying attention to roll bar tuning seemed the nicer go for now.

Beyond that, I went with digressive valved shocks and custom strut body lengths to get my ride height. The digressive valving will act as a stiffer damper when I hit the brakes, gas, or enter a corner preventing dive/lift/roll, but allow for good tire contact with softer damping otherwise than a standard valve. That allows me to use a softer spring rate to give the benefits of a stiffer one without the downsides as well, on a non aero based car. Eventually if it sees high downforce, spring rate will be the only way to counter it.

Brown Handwriting Rectangle Font Music
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Some updates, small ones.

I added camber bolts because my suspension won't be done until mid-late MAY now. May 8th is track day, so that's a no go.

I trimmed my rear bumper support to match the bumper. It doesn't serve any purpose but to hold my bumper now. That should help airflow (about 2.5" cut off)
Vehicle registration plate Automotive tail & brake light Tire Vehicle Automotive lighting

I replaced my stock tails with some painted ones I started in 2019.
Automotive parking light Automotive side marker light Vehicle Car Automotive lighting

And I added a light strip to my firewall. It's my only interior lighting, but lets me see my cargo bay (re-usable grocery bag behind the passenger seat) at night. Actually lights up the whole cabin
Automotive lighting Gas Electric blue Event Midnight
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Well, I made it to the track yesterday. I did a couple sessions to learn the car a bit before I put the dash cam and GoPro in for the afternoon. The car handled fantastic surprisingly, even on very wrong suspension. It did blow up the muffler, however. So for anyone looking to run an OEM muffler at the track on a shortened exhaust, don't.

Unfortunately, to keep a long story short, it has a cam sensor code and couldn't keep going through the day. It's back in my shop now for diagnostic. It's not a bad cam sensor, as I replaced that with a spare and have no luck. Next up is tracing the wire connections, checking timing marks, checking the cam reluctor trigger, ECU grounds (unlikely), crank position sensor, and then some very unlikely scenarios past that if it comes to it.

Oh well, every Wednesday starting next week is a chance for the track and some footage
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Alright, so diagnostic result was that the timing slipped. Which is especially odd, as the belt is still tight.

I'll be checking out the crank keyway, and the teeth on all the gears. I'll also be using new tensioners and a fresh belt
Everything was fresh, assembled outside of the car, and torqued. That's why it's so odd that this would have happened.
Could you have not fully tensioned the belt when you first put the timing assembly back together?
It's a possibility, but it's still tensioned right now even. Beyond that, the auto tensioner should be able to take about 1/2" of slack out had I had that much deflection.

Something might be out of round, failed tooth, or failed key
The tensioner pulley maybe not down enough or something walked, maybe something shifted with the waterpump. Timing is my biggest concern with my engine build

belts, main bolts and main bearings seem to be the only weaknesses of these engines

did you bend any valves?
I haven't had time to look at it beyond "yep, that's out of position". Likely won't have an answer for a couple more days. I need to do work on my TT, gonna start to daily it again and it needs a few things done, most pain in the ass being a spring changed (snapped the front left). But I'm sure the strut is going to fight me coming out with everything it's got
Dude enjoying the builds like where your headed with these cars
Dude enjoying the builds like where your headed with these cars
Thank you.

The coilovers have arrived. They needed to be watered for a bit as they were small

Hand Circuit component Finger Thumb Nail

But then they filled out
Camera accessory Gas Cameras & optics Automotive tire Machine
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The coilovers are on, as is a new quad tip exhaust. It needs an alignment
Car Vehicle Vehicle registration plate Tire Plant

Wheel Automotive parking light Tire Vehicle Car
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Aaaaand a video clip of the new exhaust sound. This was the first I'd heard it rev out. It sounds good. Not super loud either.

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