AW11 MR2 Rallycross build

In reply to dherr (Forum Supporter) :

Looking back on the transmission work, I really should have just pulled the engine along with the trans.  I didn't really have any reason not to, I had a left and an engine hoist.  The only thing stopping me was not wanting to muck around with the wiring harness, and my heavy dislike for bleeding the coolant on this thing.  The last time I pulled a transmission, it was on a front engine rwd car, and it was a lot easier.  Looking back on it, I think it would have been easier to just pull out both together.  

As for the V6, no amount of extra cylinders is going to make me faster at the track.  Power isn't the issue, its definitely the nut behind the wheel.  That said, I know a couple of people down in VA with a less than functional MR2 spyder who seem pretty hot on the idea of V6 MR2, or maybe they could shove it into one of their many Miatas. I bet it would fit.

Understood, I'll definitely be putting it all in as one assembly and pulling it out as one assembly to separate the current V6 since I need the transmission for my swap.

Please pass along the deal to your friends down in Virginia if they are serious about a V6, this a good deal for the right person.

This weekend it's time to get back to work on the MR2.  Actually, I'm starting to run out of parts, so soon there won't be much left for me to do on the car other than wait for extremely delayed shipments, and wish I could take it out to get it dirty.  The game plan for the weekend is to replace the shift lever in the car, and to tackle the brake proportioning valve.  Should be easy, but being me I figured out a way to mess things up.

The AW11 came with a shift lever meant to be held like a pistol grip, and the PO then installed a janky short shifter, and a ball knob on top.  The result used to be that the knob was a little too high, but now with the 6 speed in there I'm also having trouble getting into reverse because the short shifter is interfering with one of the shift cables.  Here's the shift lever today:

The car came without a shift boot, so I make the one on the car long ago out of some flannel.  The sewing job on it leaves a lot to be desired, but it's mostly holding together.  That said, the janky short shifter also causes the fabric to be caught between the shift cable and the center consol, and ripped my artful sewing.  

The new shift lever comes out of a later model 93+ MR2, which apparently fits right in but is shorter, which means reverse shouldn't (hopefully) interfere anymore.  So, I pulled apart the center console and disassembled the shift lever only to look at it and realize I really needed to grease the ball joints, and of course I don't have any grease in the garage.  I'm not sure how that happened, but apparently I haven't done any work requiring any grease up to this point.  I considered greasing them up with vasoline (it'd probably work), but finally gave in and ventured out into the plague infested countryside to get some grease.  Here's the end result

The shift lever is much more comfortable now, it doesn't interfere of the shift cable when shifting into reverse, and as an unexpected bonus there's a ring/ledge thing around the top of the lever which holds the shift boot up.  While I had the center console out, I also re-installed the fake-leather armrest thing, you need to bend the tabs in from under the center console to get than damn thing to stay in place and I've been too lazy to bother since it came off on me while someone else was codriving the car at a rallycross.  

With that, I took the car out for a quick spin just to make sure everything was working right, only to find I couldn't get into reverse!  I suspect that the bracket at the back of the car, which now has a little bit of wiggle room when the bolts are loose, shifted a bit on me.  So, I took the air filter off, loosened the bracket up, conned my wife to test shift for me, then tightened it all up again.  Reverse works fine now, great, but I discovered during the test drive that you can't get into 5th any more.  Well, sometimes you can, but usually you can't.  Oddly enough, 6th works just great.  

After filing the hole in the mounting plate a bit wider so that the lever didn't interfere on the mounting plate when pushed right, and loosing and tightening the bracket in the rear 5 or 6 times, and driving around the block after each change only to find the problem still there, I finally found a solution:

In the photo above, you can see the shift lever without the center console in the way.  What was happening when you went for 5th is that you'd move over to the right just fine, and then as you pushed up the lever would sorta slide to the left on you.  It wasn't fouling on the (square) hole in the metal mounting plate, it was hitting the end of travel on the (circular) ball joint bushing.  What I needed to do was pull the gear lever back just a hair, so that I could get it into that 5th position, actually if you squint just right at the photo above, you can see that it's sitting slightly forward (it's in the neutral position).  

I was about to go fiddle with the bracket in the back of the car, even though previous attempts had only moved the lever left and right (not back and forth), when I noticed that there is some adjustment on the back-forth shifter cable!  So, yeah, I screwed that guy in, and everything was fixed.  For such a simple project, it sure did take a long time.  

On to the proportioning valve, that'll be easy right?  I got a new Wilwood proportioning valve as a kit for a Miata since they share the same 10 mm brake line fittings, it came in a kit with everything I would need.  Except of course it didn't.  Here's the proportioning valve for the MR2:

2 ins, and 3 outs.  2 of the outs go to the front wheels, and the 3rd is routed back to the rears.  Apparently Miata's are weird and have a proportioning value with 2 ins and 2 outs.  So, the kit came with a simple straight barrel union, and in the MR2 I needed a Tee.  I actually figured this out weeks ago, and already had the Tees I would need in the house.  So, no problem, right.  Well...

Here's those 10 mm brake line fittings attempting to be fit into the new proportioning valve.  Both of those fittings are screwed in about as far as I can get them, and have a whopping 1 or 2 threads of engagement.  I had the same basic problem with the Tee fitting as well.  Call me cautious, but I don't think that's enough.  The problem is being caused by the rather long unthreaded section on the MR2 fittings.  They were designed to go into the cavernous depths of the Aisin proportioning valve, and all my adapters are just too shallow.  

To add just a bit more aggravation to all of this, when I went to remove those brass adapters on the proportioning value to confirm that they really are too shallow, I discovered I screwed them in way too tight into the valve.  The valve body is just aluminum after all.  I got one out, but it mangled the threads.  The other shattered on me, apparently you can shatter brass.  I thought about repairing the valve, but at $40 (this time with 10 mm inlets from Wilwood instead of brass adapters), I don't think its worth my time.  I also ordered a new Tee, hopefully the new bits are deep enough, if not I guess I'm going to learn how to flare brake lines.  

With the brakes waiting on parts, I picked up a small shop project that I've been putting off.  Back when I pulled the transmission, I picked up a transmission jack (seemed like a good idea).  But, the lift I have in the garage is only a mid-lift sorta thing, and even then I top out on the garage door opener (a future project) before I run out of travel on the lift.  This meant that the transmission jack with stand was way too tall to actually fit under the car.  I could get the hydraulic cylinder under, but not the stand with wheels.  

I used it anyway during the transmission install to support the engine, but it would be a lot more useful to me if it had wheels.  So, I went through my metal scrap bin, found some 1/8" angle and bar stock, and put together this:

The 4 captured nuts mount to the base of the cylinder, and the large hole there is access to be bleed valve.  Then the legs with wheels that came with the jack attach with 3 bolts on either side of this box.  If nothing else, it was an excuse to get a bit more practice with the tig welder.  The welds don't look great, but they seem pretty strong.  Here's the whole thing put together

I can pretty quickly unbolt the cylinder from the base for easy storage as well.  The box base isn't quite as stiff as I'd like it to be, it would have been better if it were made of thicker stock which I don't have.   But overall I'm pretty happy with how it came out.  While I'm not planning on replacing the transmission again any time soon, this should be useful for other more common projects, like removing or installing the skid plate every oil change (i.e. after every race).  

Ugg, these brakes are not being easy for me.  

The new proportioning valve is here, and it's not going to work.  The inlets are threaded M10-1.0, so the threads fit.  But, the seat is a bubble flare instead of an inverted bubble flare.  Finding M10 inverted to bubble adapters is even harder than finding M10 to NPT adapters.  Back to the drawing board I guess.  

I've spent way more time looking for a solution to the brakes than I'd care to admit.  The options were either get a flaring tools, or find fittings that would make the conversions needed.  I really want to take the second route so that if the brake proportioning value really causes me a bunch of trouble I can just put the stock part back on.  Can't do that if I cut the brake lines.  

The problem is that there just aren't that many options available for converters between M10 and well, anything else.  I couldn't find anything from M10 inverted flare to M10 bubble flare for sure.  I breifly though about making my own adapter, but that sounds like a bad idea.  My lathe skills aren't that great.  Flying Miata has M10-1.0 inverted to NPT adapters, but I already tried those and know for a fact that the female end of them is too short.  I checked out what the ae86 guys do when they put proportioning values on, and got a part number for the Tee (272061ERL), but nothing on converters for the valve inlets.  

So, after hours of frustrating google searching, I finally settled on a plan.  I could find M10-1.0 inverted flare to -3 AN fittings, and these were the only fittings that explicitly listed Toyota compatibility.  That wasn't going to work with the Wilwood proportioning value, but it would with a Tilton.  The Tilton valve is twice as expensive as the Wilwood and fewer reviews on it, so hopefully it'll work.  Here's a photo of all the parts:

In case you're trying to do something similar, the part numbers are:

Tee: 972061ERL

M10-AN adapter: 989538ERL

Porportioning Valve: Tilton 90-1000

Here's one of the M10 to NPT adapter from FM in comparison to the Earls adapter.  You can really see the how much deeper the female end of the Earls adapter is.  The shape of the fitting would also fit in any of the brake line mounting tabs on the car, not that I need to do that.

With all the right adapters, it was pretty quick getting the valve installed.  Here's everything in place

I did need to fab up a mounting bracket for the valve.  It would have been pretty easy to bend up something out of steel, but because I'm a glutton for punishment I opted to weld up some aluminum scraps instead.  The welds are pretty impressively ugly, but the bracket seems stiff enough. 

Since I have the brake lines pretty much empty of fluid now, I figure it was a good time to go ahead and replace the original rubber brake lines with some snazzy stainless ones as well.  I've never bothered with these before, figuring if I can lock up the brakes then what more do I need.  But, there's a first time for everything.  I got about this far with the first line before I decided I really needed to do something about the brake line tab

Up till now, I've just been bending the brake line tab on the strut every time I took the struts off.  The SS lines are a little narrower than the rubber ones, so if I expanded my cut just a little bit I figured I could get the line in place without bending the tab each time.  So off came the strut.

Around that time, a shipment showed up at the door that I've been waiting on for about 9 weeks or so.  In it is a coilover conversion kit for the car.  So, guess there's more strut work to do.  That brings us to struts.  Shock options for the AW11 are super limted, KYB and Koni is about all there is.  The Konis are great, but don't last long in rallycross.  

A little noodling around on the internet will find you stories of people adapting SW20 struts to an AW11, if the SW20 struts work then I could get Bilstein HDs.  That's pretty desireable for a rallycross car.  As chance would have it, a few months ago a set of used SW20 struts came up for sale on Craigslist for not that much money.  I figured I'd use them to see if they could be adapted.  Here's a photo of an AW11 and SW20 strut

I've tried to get the mounting holes for the control arm lined up here.  Spacing looks like it should work, but the SW20 holes are bigger.  My original plan was to make some adapter bushings on the lathe, but there's another issue.  While the body of the SW20 strut is shorter, the overall length is also reduced.  I took measurements:

SW20 - travel: 155 mm, length: 385 mm

AW11 - travel: 165 mm, length: 414 mm

The length is measured from the top of the control arm mounting bracket to the top of the threads (and is not accurate to 1 mm).  What does all this mean?  If I adapt the SW20 struts the front suspension will have to be lowered at least around 30 mm (1.18 inches).  I don't want to lower the car, the scrapes on the bottom of the car indicate that it's already plenty low enough.  

In summary, I ordered a coilover conversion kit for the AW11 from T3.  Like many other 'bolt on' kits, there are some fitment issues.  In particular, the weld on seats are pretty clearly not the right size:

The ID of the weld on collars is 2.040", where as the OD of the strut body is 1.784", about 1/4" out.  I don't think I'll be bridging that with weld...  I'll contact T3 about it, but I also ordered some 2.5" OD, 3/4" thick tubing from McMaster, I should be able to make collars out of that.  

Well, the situation with the coilover conversion kit is worse than I thought.  After looking at these things a bit more closely, it's pretty clear that the sleave things were made assuming a nominal strut diameter of 2 inches.  The AW11 struts are not 2 inches in diameter, they are distinctly smaller.  In addition, the upper spring hat things also are too large for the shaft of the AW11 shocks.  They seem about right for the SW20 shocks, but the AW11 ones are smaller, as seen in this photo:

All of this is a problem because I really want the springs to generally stay parallel to the shock shaft, and certainly don't want them flopping around.  If this were a street car, maybe I could get away with this.  But, I'm driving this car aggressively over very not smooth surfaces, I'm pretty sure it's a bad idea to allow the spring to move in the not up-down direction.  

I also don't want to lower this car any more than it already is, I already said that.  So, when I ordered the kit I ordered it with 10" long springs.  I did actually get the longer springs, here's a pic of the new springs next to one of the Eibach pro AW11 springs, they're about the same length

To allow for maximum travel, I want the top of the coilover screw thing is be about inline with the top of the shock (or strut).  If we look at the length of the screw, it's pretty clear I'm going to have to remove the swaybar brackets to get it that far down the strut tube

Removing the swaybars was actually part of the plan though.  The autocross setup for the AW11 usually doesn't include front or rear bars.  I also asked around a bit last year to see if sway bars were at all desirable for rallycross, and the answer I got was that @irish44j didn't use them, and he's the fastest mod-rear car in the region.  That generally meshes with my conception that more wheel independence is better when the surface you're working with has less traction and isn't smooth.  Anyway, the springs are 400 lb/in front and 200 lb/in rear, which is just proportionally scaled down from what the autocross guys are running.  

So, where does that leave me.  Well, in addition to fabbing up some new weld-on spring perches with smaller ID, I also need to make something to keep the coilover threaded sleave parallel to the strut body.  That's just a ring with a 1.75" ID and 2" OD (measurements very approximate).  And then to keep the upper hat in place, I'm going to need to make a bushing thing probably out of aluminum.  If there's a lip at the top of the bushing, I shouldn't need to weld it in place which is good, cause I suck at welding aluminum.  It's a good thing I have a lathe, or I'd be pretty frustrated about now.  

Anyway, I'm pretty clearly committed to this possibly bad idea

Also, I don't have a use for the Eibach spring anymore, you know if anyone else building an MR2 in the area needs them.  

Well, plans changed but for the better.  I contacted T3, and they had the perches, top hats, and o-rings in the correct size.  Those came in a bit ago, and they test fitted just fine.  Means I don't need to machine my own bits by hand, which is a bit of a bummer.  With that off my mind, I went ahead and cleaned up the strut bodies better using a wire wheel.  They looked like they had a bit of surface rust, but either it came right off or it was just dirt.  There's a lot of dirt on this car.  Anyway, they're looking a bit better now, not quite weld ready but close

The strut with the sharpie markings has some high spots still, high enough to keep the perches from slipping over.  The other 3 have a line where I plan to weld the perch at.  

With that done, I turned my attention to the strut top hats.  In front, the AW11 has bearings in there.  At some point, one of the POs kindly removed and lost the dust caps which keep dirt and grime out of the otherwise pretty open ball bearing.  This this idiot followed their example and proceeded to race the car on dirt.  They're not very clean anymore, and it doesn't look like it'll be easy to get new ones.  I see them in stock for the 87+, but not the earlier AW11 Mk1a, and they're different.  So, I cleaned them out as best I could, and will re-pack them with grease tomorrow.  Here's a before and after, hopefully you can tell which one has been cleaned.  

The only issue is that they're sure to get all grimed up again after my first event, meaning I should probably put some form of dust cap on there.  I could probably buy something, but it's much more logical to use expensive machinery to mill down expensive delrin material into fender washers worth pennies, right? I think these should do the trick.  The larger ones go on the bottom, and the smaller ones on top.  The upper ones fit tightly enough that it's very difficult to get them out again once you put them in.  

Timing to finish up the suspension, so I fired up the tig and got to work.  I had a bit of trouble with the first strut, the weld kept pulling junk up into it, which is generally worrisome.  I did grind down the surface of the strut where the weld was to bare metal, but was still having issues.  Turns out the problem was the scale on the perches, whatever it was wasn't nice.  I had hit them with the belt sander already, but the scale was thick with these guys.  I probably would have had an easier time with a weld process less picky about contaminants, but the welds made by the tig are always stronger than what I can get from my mig (because it's a cheap POS).  Anyway, here's one of the welded perches, could look better but should hold up fine.  

Next up was paint.  If I don't paint them, they'll surely rust in about 30 minutes.  Also, my understanding is that the brighter colored your performance parts are, the faster your car goes.  They're the same blue I used on the transmission brackets, cause I still had a bunch of that laying around.

The top hats up front also had some rust on them.  Ideally, I'd bath them in some evaporust, but that's probably not a good idea with the bearing in there (it would absolutely etch away at the bearing surfaces).  So, I coated those with some Rustolium rust converter, and hoped for the best.  They look pretty good, if you don't get too close

I also repacked the bearings with grease, I didn't forget to do that.  

The rear tophats also have a good layer of surface rust, and they don't have a bearing in the middle, so those did go in a vat of evaporust for several hours.  But, I'm an impatient person, and wanted to get these all together.  So, I pulled and painted them as well.  I can still buy the rears anyway, or I could get some fancy camber adjustable things maybe (I'm not sure how well those will play with bumpy rallycross courses, that's why I don't have them already).  

The threaded sleeves are held concentric to the strut housing using some beefy o-rings.  The o-rings fit tight enough that when you try and slide the sleeve over, it will roll the o-ring down the housing.  To fix that, I used a ridge of slicing tape below each o-ring.  If you haven't run into it already, splicing tape is awesome.  It makes a waterproof seal, handles weathering very well (for tape), and when you finally have to remove it doesn't leave any adhesive residue.  This is my go-to for sealing electrical connections and (shock) splices.  It's also useful for things like above.  Everyone should have a roll or 3 of this stuff in their garage.  

From there, it's just a bit of futzing around until you have a fully assembled coilover.  I added a washer between the upper spring seat and the bearing seal, cause that seemed like a good idea.  Finished product looks something like this

Side note, hat giant adjustable wrench there has proven to be more useful than I thought it would be.  I thought I'd only ever use it for the purpose I bought it for (tightening the seal on the air compressor), but that has proven to not be the case.  on this project, it's big enough to get onto the gland nuts.  

Nice work on the coilovers, I might be interested in the Eibach springs, are these the standard Eibach Pro-Kit for the AW11?  Did not realize how close you are to me, I am just down the road in Frederick.

In reply to dherr (Forum Supporter) :

Yeah, they're the standard Eibach Pro kit, and they're available for barter

Got a bunch of AW11 parts, what do you need?

In reply to dherr (Forum Supporter) :

I'm sure lots, now if only I knew which they were...  My most immediate need is a set of helper springs (see below), but I also accept IOUs, help rebuilding engines, cookies, and beer.

As for the build, I got a bit more done today.  I've had the suspension on and off this car a number of times, it's probably not worth listing them all.  The rears are always a pain to get lines up so I can get the control arm bolts in.  The AW11 control arms are very freely moving.  So, first order of business was to build a new tool, an alignment pin.  Basically something with the same diameter of the control arm bolt, but with a nice gradual chamfer at one end.  

It's a little hard to see the bevel, it's only about 3 degrees or so.  In hindsight, I should have made it a bit steeper.  That said, I did use this on the rears.  It's always the rears that gave me trouble.  Then, after not that long, all 4 corners had shocks and springs again

Finally, I just need to bleed to brakes before I can take this thing for a short test drive.  I don't have any daughters with face paint, so I didn't take photos of the bleeding process.  It was pretty boring and uneventful except that the rear driver bleed valve was clogged.  I was able to un-clog it with a small drill and a bit of fiddling.  What brake fluid was in the lines was pretty cruddy, I suspect the brakes hadn't been bled in at least 2 owners worth of time.  Here's the car on wheels on the ground

That photo was taken on a slight downhill towards the front end.  It's pretty clear that the front's a tad higher than the rear now.  This shouldn't been too surprising as I just replaced whatever the OEM/Eibach springs were with springs I'm guessing are twice as stiff.  The weight of the front end didn't change, so the car settled on the springs less.  Of course it did, seems obvious now.  

I can't fix this by getting shorter springs.  The amount of spring compression while the car is stationary is going to be the same so long as the spring rates are the same.  And if I lower the spring seat, then the entire setup will come apart if I ever completely unload one of the front wheels (... catch air).  Fortunately (depending on how you look at it), this is fairly likely to happen at a rallycross.  Unfortunately, the spring seats tend to not take it that well when the car eventually lands again.  What I need is a helper spring, well 2 of them (the rears looks ok as they are).

I took the car for a test drive anyway, and it actually handles quite well.  I suspect the alignment is all screwy now, but even so turnin was reasonable, and it corners fine.  At the current proportioner setting, the brake bias is such that the rears just barely lock first on dry pavement, which is probably about right for dirt, maybe.  There is a snag there as well, the adjustment level for the brake proportioning valve fouls on the front strut bar.  I didn't notice before because I didn't have it on.  

The solution to my the suspension rake has arrived in the form of ebay-special helper springs.  Helper springs from all the normal sources were annoyingly expensive, especially for springs that don't do much.  These were pretty much the cheapest 2.5" springs I could find, which means they're great quality for sure.  Like all the best things, these were made in China and they included plastic spring couplers, which I don't think I'll be using.  I also got a chunk of aluminum tube so that I can just make my own.  

Given the price point, it's no surprise that they didn't come with a specified spring rate.   I've seen helper springs specified with spring rates between 5 and 100 lbs/in, these look a little on the chunky side so I'm guessing they're at the upper end of the range.  Obvious thing to do is measure them!  Mostly curiosity really.

First I tried compressing the springs with an old break disc, that didn't work.  Then I pulled out the big guns and put together some ultra high-tech equipment to measure them

To compress the spring, I stood on top of the 2x4, carefully.  If my measurements are correct, these are indeed 100 lb/in springs.  

I wouldn't sweat the reverse-rake. I've intentionally been running that way for years now and have always felt it made the car much better on the dirt. Obviously different weight setup, and you aren't going high up front to get engine cleance though. Just saying, might be worth running first with the reverse-rake and see how it works for you - especially at Panthera with the hills. 

In reply to irish44j (Forum Supporter) :

Your suggestion appeals to me because it means not taking apart the suspension again.  If there were an event coming up really soon, I think I'd run the car like this at least once.  But, I'm also worried about the lack of droop travel in the front, during my test drive I was feeling the car skipping over sudden drops in the road.  No droop travel is probably ok for smooth pavement, maybe not for dirt.  

Quick and dirty calculation, the MR2 is 2200 lbs with a 45% front weight bias.  That should mean about 500 lbs on each front wheel, which should compress the front suspension about 1"-1.25" (there's some slop because I don't know the motion ratio).  Overall shock travel is about 6.5".  Is that enough droop travel?

Yeah, but your droop travel isn't being limited by the spring itself, it's limited by the maximum extension of the strut (and/or by frame interference as the control arms drop, in the case of the e30). MR2 has radial bushings at the inner end (so probably no restrictions there, but a balljoint at the outer end (so not sure how much additional droop angle it can take before maxing out). Adding spring height doesn't increase your droop travel, it decreases it since at static ride height you're already closer to the strut's maximum extension. 

Are you lifting the front wheels on flat surfaces, or when turning? If the latter - do you have a front swaybar installed? I don't know MR2s well enough to say, but my recollection is an e30 has about 8" total travel at the front wheels - but I have taller shock towers of course. MR2 has tighter packaging. 

just for the sake of comparison, I just went out and jacked up the front of the e30 and my Porsche 924. 

e30 is probably about 1" taller than stock, and has exactly 4" of front droop travel from static ride height (so, would be more like 5" from stock height). Obviously, this car is more nose-heavy than yours.

Here's my front droop ;)

Porsche on totally stock suspension has 4 1/8" of droop travel from stock static ride height. And that's a car that has slight rear weight bias, so closer to the MR2. When I drive it, the front end is definitely more likely to skip a bit on rough turns (the rear end never, ever loses traction). 

Honestly, I think that's just the nature of having a car with that kind of weight bias. How much droop do you get from static ride height if you jack up the car (both sides, if you have a sway bar)?

Few things. First your spring rates seem really high for rallycross. Front spring rates on e30's in our region are between 200-250 lb/in. My Volvo 240 is at 225. Rear wheel rate on the Volvo is good at around 200ish. Keep in mind these cars are all in the 2800lb range. 

With the coilovers the car will sit off the springs at full droop, this is normal. Just run tender springs (the thin wire springs, like 10lb/in rate) with that spring joint connector you got with the helper springs. The actual regular spring length is only of consideration in trying to prevent coil bind, and also making sure your coilovers sleeve can go low enough to actually fit the spring.

Normally you'd aim for 45/55 droop/bump travel (not including bumpstops). It's not really that specific though, just try and get it in the ballpark. Maybe go with more in bump travel because your car is limited in travel and your not gonna be jumping it.

The car skipping over bumps is probably both lack of droop travel and low rebound on your shock. Is the skipping speed related? The Volvo's valving on the rear makes it hop over speedbumps at 20mph, but at 50 they feel great. 

I would suggest going down to a 175lb/in spring in the front with a tender spring. For the rear I'm not sure, probably aim for at 175lb/in wheel rate, also with tender springs.

I just went and measured, looks like my estimates were surprisingly accurate.  The front has 1.25" of droop travel (must have a motion ratio close to 1, which makes sense).  Droop travel in the rear is 2.75" (vs. 3" expected from the rear weight and the spring rates).  I think I'll do a full motion ration measurement this weekend, seems like a good thing to know.

Somewhat related, if I follow ¯\_(ツ)_/¯ 's simple method of estimating spring rates, I should be looking for about 2.1" of static droop, which yields 225lb springs front, 300lb springs rear. Springs are cheap enough that I'll probably try that out sometime this season, and see which setup I like better.

In reply to lxnm :

If they are still available, would like to get those eibach springs from you. I have decided to start with the Koni inserts and pro springs as the starting point, since my project is a street car. Happy to trade you for beer, have any Flying Dog favorites?

In reply to Nesegleh :

Somehow I missed your comment earlier.  Adding tender (helper) springs to the coilovers is exactly what I'm trying to do.  I don't think I can go as low as a 175 spring rate, the MR2 is pretty travel challenged and I suspect I'd spend a lot more time on the bump stops.  

The helper springs came with some plastic couplers, but I don't trust those very far.  So, I went ahead and made a set myself

That's 2 couplers on the lathe there, I'm about to part them off.  The aluminum gave me a bit more trouble to turn than I expected.  To get good chips I needed to take a pretty deep cut, but if I did that I'd stall the lathe and the drive belt would slip off the drive pully.  This resulted in one of the drive belts crashing into the wall leaving a pretty good mark; the wife was not pleased.  

But, I more mistakes than that were made.  The helper springs had an ID just under 2.5" (2.450 was my clearance OD radius for the springs).  I rashly assumed that the nicer Hypercoil springs on the coil over would be the same.  They're not, they have a slightly larger OD.  But, did I take off one of the coilovers before making these?  Of course not.  I was able to get the whole thing together though

Of course the issues don't stop there.  I sure hope someone is learning from my mistakes because it obviously isn't me.  To get the helper spring on the coilover I had to compress it, the spring perch is wound all the way down to the bottom there.  Then because the helper springs are so stiff, the preload on the strut meant that the suspension didn't drop very much, about another 0.25".  

But, there's a bigger problem brewing which I didn't notice until I had the strut on the car but you can see in the photo above.  With the helper spring at the top there, when the suspension is at full compression the helper spring is going to overlap the screw colar.  That's ok, I suppose, except that the adapter collar doesn't clear the screw.  With the setup as above, I've effectively reduced my already lacking travel by a few inches, and replaced my bump stops with aluminum.

I took it all apart and bored out the adapter.  By the time I got enough material removed from the adapter, there wasn't much material left.  The wall thickness was reduced to about 0.020".  That will fold over if it ever catches the strut body.  I'm going to need to re-design the adapter collar so that it matches the ID of both the main Hypercoil springs, and the smaller helper springs, while still somehow clearing the threaded sleeve body.  I'm probably also going to have to shave off some material from the ID of the helper springs, actually I already had to do that on one end because they didn't fit over the upper spring hats.

And, I need new shorter springs. Since I need new ones anyway, this would be a pretty good opportunity to listen to the people in the region with more experience than me who are also faster than me.  But, instead I loaded up Dirt Rally 2.0 to test out the setups I'm considering, this is probably a very bad idea.  The closest car to the MR2 they have is a Stratos (similar weight and weight balance, a little shorter wheelbase amazingly, and a bunch more power) and tried Hoelscher inspired spring rates (that's what I have now, 400 front 200 rear), and  ¯\_(ツ)_/¯ inspired rates (225 front, 300 rear), neither setup with swaybars.  I'm distinctly faster on the Hoelscher setup.  Shorter 400 lb springs are ordered, I'm probably going to regret this.  

Fyi...Tender springs and Helper springs are not the same thing. Tender springs have pretty much no rate whatsoever and just enough spring to them to keep themselves in place. The coils are basically super thin and flat in profile. They pretty much have no effect whatsoever on the car suspension feel - they only exist to hold the main spring in place. when your car is sitting on the ground a tender spring should be pretty much fully compressed onto itself and doing nothing. The only time they are uncompressed is when you are at droop. Also because they are so thin they basically don't add any additional length to your overall spring stack height.. maybe half an inch at most

Helper springs actually add rate to your overall spring rate (which is why they are thicker and have a round profile), and actually can be extremely stiff. A lot of people use those to get some kind of progressive rate on their overall spring rate or to tweak their main spring rate up or down.

Those are helper springs you have there. Here is what tender springs look like: 

as you can see tender springs have so little rate you can fully compress them just using one hand.

For what it's worth the effective rates on my stage rally E30, which is substantially heavier than your car, are 225 up front and about 200 in the rear (the actual rear spring rates are different because of the suspension setup having them mounted on the trailing arm). What kind of rear suspension does the MR2 have?

It's got McPherson struts on all 4 corners.  The rear almost looks like it was lifted out of a FWD car.  That should mean the wheel rate is very close to the spring rate (I was supposed to try and measure that today)

On the Tender vs. Helper spring question, you may have it backwards?  They really seemed about the same when I was looking them up the first time around.  In any case the red spring in the pictures has flattened coils, and is fully compressed when on the car.  But the coils are substantially thinker than the black spring you have in your hand there, and the spring rate is unsurprisingly higher.  The red springs also do clear the threaded sleeve, but not with much to spare.