[DefSport]

BTW - been pouring over data, and noticing what is likely the cause of the Megasquirt PNP needing way more inj. duty cycle up top than the AEM Infinity. I have a fuel pressure gauge installed with the Infinity, and it references fuel pressure. I knew it dropped a tad towards redline - no big deal, it'll never been EXACTLY base pressure referenced. But after putting a gradient color scheme on the fuel pressure difference channel - wow, it really drops a ton.

It generally runs 44-45 psi base pressure with zero inj duty cycle, light inj duty cycle like cruising at 70 mph is around 42-43 psi, but under high load and 17 psi of boost it drops down to 34-35 psi... yuck. The Infinity totally compensates for this, but it makes me think this is voltage drop going through the stock fuel pump wiring?

Supposedly there's a Supra TT Denso pump installed... I hope it's not some Chinese knockoff or something??? Do you guys think this is a stock fuel pump wiring issue? I would like to do a fairly clean install with a secondary relay if I do that - is there a spare fuse location in the driver's footwell fuse panel and a large 12V+ batt source to tap from? Otherwise I could come off the secondary fuse box I added in the engine bay into the cabin to feed a relay with a 12 AWG feed. But it seems silly to go from battery to rear fuse panel, to another fuse box, then forward to fuel pump.

You can see on the bottom trace where the fuel press diff channel drops down (kpa only - some annoying unit display bugs in Infinity Tuner... only real bugs I've found), it goes from green to red when it dips below like 41 psi I think.

 

[joshuaho96]

You can try seeing what the voltage drop across the fuel pump if your diag connector is still functioning by measuring voltage across FP+ and E1 while going full throttle on the dyno. I don't see any reason for the fuel pump to be losing voltage at high RPM in the OEM circuit diagram, it's a direct path to B+ so any voltage difference between FP+ and E1 compared to battery terminal is just losses in the wiring.

 

[DefSport]

Well, a stronger fuel pump will draw more current than the stock pump. I agree that on a stock pump you probably won't see a huge voltage drop through all the wiring, but a higher capacity fuel pump can easily pull 50-75% more amps than a typical ~7-9 A stock pump (which is why it has a 15 A fuse and probably 16 awg equivalent wiring). Start pulling closer to 12-14 A and the voltage drop will more than double through the stock wiring. This causes current draw to go up, etc.


Question - does the stock SW20 fuel tank starve on track at all? I can see it being really good on corners since it's so narrow, but it's super long, so I wonder if it tends to starve under acceleration. If it does - maybe I'll just add a Walbro 450 lph pump I've got into a small surge tank in the engine bay. It'll add some additional heat into the fuel, but it'll make fuel starvation basically impossible.

 

[GDII]

Well, a stronger fuel pump will draw more current than the stock pump. I agree that on a stock pump you probably won't see a huge voltage drop through all the wiring, but a higher capacity fuel pump can easily pull 50-75% more amps than a typical ~7-9 A stock pump (which is why it has a 15 A fuse and probably 16 awg equivalent wiring). Start pulling closer to 12-14 A and the voltage drop will more than double through the stock wiring. This causes current draw to go up, etc.


Question - does the stock SW20 fuel tank starve on track at all? I can see it being really good on corners since it's so narrow, but it's super long, so I wonder if it tends to starve under acceleration. If it does - maybe I'll just add a Walbro 450 lph pump I've got into a small surge tank in the engine bay. It'll add some additional heat into the fuel, but it'll make fuel starvation basically impossible.

The fuel tank has a surge tank type construction around the pump already so it does quite well at keeping fuel where it needs to be as long as the tank isn't too empty.

 

[Alex W]

Question - does the stock SW20 fuel tank starve on track at all? I can see it being really good on corners since it's so narrow, but it's super long, so I wonder if it tends to starve under acceleration. If it does - maybe I'll just add a Walbro 450 lph pump I've got into a small surge tank in the engine bay. It'll add some additional heat into the fuel, but it'll make fuel starvation basically impossible.

I have run it down to the 1/8 mark or less on track with no starvation issues.

 

[DefSport]

I have run it down to the 1/8 mark or less on track with no starvation issues.

Thanks, sounds like a good design then. I’ll run some thicker gauge wire to the “Supra TT” pump and see how it behaves.

Alex, am I correct in you mentioning you used an empty fuse spot in the driver footwell fuse box? I thought I read that, but can’t find the old thread again.

 

[Alex W]

I used an extra spot in the fuse box in the frunk. There may be extra spots in the drivers footwell as well, but I know there are two extra spots up front.

 

[DefSport]

Gotcha - is there convenient 12V batt to tap there where you don't have to run a wire to the positive battery terminal?

 

[Alex W]

I think so. Seem to recall a pretty big main power wire from the battery to a screw terminal that you could add a wire too. It's been a while though.

 

[DefSport]

Got a new Wix fuel filter to see if maybe that was a bit clogged. I don't know when it was changed, and while I haven't driven the car a ton, might as well see if that fixes it.

Also washed the car... first time of 2020 for sure, can't remember the last time (it's mostly a garage queen):





Cleaned up pretty nicely.

Otherwise been mostly working on house projects since I've been on an SW20 project kick, and I've just been working on the tune after some datalogs. It honestly drives really well, although I have had a weird return to idle stall that a bit puzzled on. It's only happened twice on the Infinity, and the logs don't look odd other than the AFR is a bit lean when it returns to idle for some reason. I think some lambda feedback PID tweaking will definitely get rid of that.

Also working on a stereo upgrade on the SW20 with stuff I've mostly already got (single DIN Pioneer). There's been some crackling randomly when driving over speakers, and the DOME fuse popped once - think something is messed up SOMEWHERE in the radio/amp setup. Might as well start fresh.

4" rear speaker bracket prototype:



Revised to reduce interfere with trim:



Mounted:



Going to use 4 channel motorsports amp for everything. ETA is whenever - don't have much time to spend on it these days.

 

[DefSport]

If anybody has a 3D printer, and wants to use 4" rear speakers on their SW20, these brackets work well for me and JBL GX 4" speakers. There's a left and right so that the upper bolt locations are not pushed out towards the interior panels too much:

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I printed them with PETG, which is super easy, and a bit stronger and more heat resistant than PLA. PLA might work if you don't live in a super hot climate. ABS would definitely work as it's more heat resistant than PETG, but moves around much more due to temperature.

 

[DefSport]

Haven't done too much with the car lately. The 4 channel amp I had blew a pair of channels 10 mins after install, sent it back for a warranty claim and they haven't had stock to ship me a new one for over 3 months now. All I can get is "store credit" and to find a replacement somewhere else. I really need the same amp (Hifonics TPS-A350.4 or MB Quart NA2-320) as it's the biggest that will fit in the stock amp space in the b-pillar. It was within 3 mm of touching in multiple spots, so no way do I want to work out fitting anything bigger (doubt it will in the end).

I'm leaning towards taking the store credit and getting a double din stereo at this point, but it's not like I'm driving the car (rains constantly here in winter around Seattle). The interior is all torn apart still and it bugs me though.

Anyway, decided to pull the steering rack and install my MR-S rack pinion gear. The rust proofing was surprisingly bad on the steel rack. It's like they barely gave the braze joints any paint, so they started rusting pretty quickly. It's kinda crazy what's rusted on this car given it's obviously never been driven in snow/salt etc and has 88k mi on it. It's definitely stuff that the factory just barely could get through the factory warranty period with mild signs of corrosion even when not exposed to road salt.

Rack as taken out of car:





Took off pinion housing and gave it 2 coats of paint. It's cast iron, so it just had light surface rust. Now it's good to go for another 30 years:



Made homemade version of the Toyota SST to remove the rack end cap. I wasn't having luck with tapping it with a screw driver much:



Wire wheeled all corrosion away:






Hit it with a coat of zinc chromate primer and 2 coats of gloss black. It should be better for rusting than the factory finish which was extremely thin paint with no primer.



Questions on steering bushings, I posted another thread so it's searchable, but thoughts on a solid steering column bushing? Thread: SW20 solid steering column bushing?


Also, rack bushings. The factory bushings look to be in ok shape, and I thought I ordered replacements, but I seem to have been waiting to examine the condition I guess. I saw some reports that the Prothane ones for the AW11 didn't fit the SW20 rack well. Powerflex has some, but haven't seen any reports on how they worked out. They're honestly a little pricey for urethane bushings too, as I've definitely seen that exact same design be a wear item on 240SX chassis that have similar rack mounts. Under hard driving they tend to shear the polyurethane "lip" that keeps the rack located side to side every 20-30 track events. Not bad when the bushings are cheap and you can toss a new one in quickly, but I'm not sure either applies to the SW20.

I don't mind a little isolation in the steering rack, as I'm not looking to make a full out race car. Just street car that can do a little track work here and there and have fun on a back road. So get a new factory bushings? Try out Powerflex?

 

[senna21]

Curious if you feel that gear is a game changer or not once you get it in. This is the first I've heard anything about the bushings so I can't add to that conversation.

 

[DefSport]

The Edelmann 9077 rack end bushing seal blew the housing apart. It was about 1 mm bigger in diameter than the stock compressed seal, but I figured it would compress down when installed and was helping seal it.

I gave a bit more of a chamfer on the housing to guide things in well (stock chamfer was tiny, like 0.5mm) and it pressed in nicely.

Then right after I got the seal all the way in... BAM! Piece of housing blows up.

Anybody have a PS rack for sale? Looks like the only way to get this piece...




Where it is on rack

 

[DefSport]

A used rack looks like near $200... ugh

I ordered some 12L14 steel rod - going to see how the old mini lathe does. It's a simple part, just a question if the lathe can maintain good surface finish with the tool pressure required. Given it's free machining steel, we'll see.

 

[DefSport]

Got some 12L14 bar and things went about like I feared. Even with new tooling it was a struggle holding better than +/- .002” on dimensions. That’s generally pretty tight except for sliding bushings like this that were probably toleranced at +/- .0005” or so on the interfacing dimensions.

Then I attacked the ZZW30 rack, which I figured no way it’d have the same part, as it looks much different externally. Got it apart, and what do you know, same seal housing!

I’m inclined to just leave the ZZW30 seal in place, as it’s 10 years newer than the SW20, and I guess I’m a little scarred from the experience of blowing it up. Lol

 

[Alex W]

It's like I was saying in another thread, Toyota doesn't seem to change mechanical parts without a good reason. Glad you found a replacement!

 

[DefSport]

The external of the ZZW30 housing looks completely different so I didn’t even think it was the same part, but was a bit desperate after my 2nd screw up on the machining (more like need .001 off radially, end up getting like .003 off due to tool post deflection, oof).

They pretty much changed everything but this seal housing, rack is different, pinion housing is aluminum and very different. It seems out of place with how many changes there are, but I guess there’s about a decade between the car intros, so I imagine the supply chain just changed over the time (both racks made by Koyo).

 

[Alex W]

(both racks made by Koyo).

And this could be the root of it. They outsourced the rack design and production to Koyo, and while they gave them a different set of specs for how it mounts to the car, how long it is, how light it had to be, etc, the internals where it didn't HAVE to change, didn't get changed.

 

[DefSport]

Aye, looks like they added quite a bit of cost to use their existing rack machining/tooling lines but meet some of the packaging requirements Toyota had.

I’m debating using the fiber/paper gasket in the rebuild kit or getting another viton coated gasket from Toyota. But I fully intend to put the rack back together soon. Getting kinda tired of messing with this thing to be honest. Kinda fiddly work that’s not really enjoyable changing all these seals out.