SR20 Swap

After 2.5 years with the 16v 4AGE, I decided to go to a SR20DE engine from an S15 Silvia. 

Installation was fairly straightfoward. Using a wiring specialties harness, only a handful of wires need to be connected for basic operation. I had to get a custom driveshaft made, cut a new hole in the trans tunnel for the shifter, and some minor firewall clearance.


Parts used:


Still to do:

Installing the Engine

Installing the engine was a bit of a challenge. I removed the core support following this Doctored Garage video where you drill out all of the spot welds for the radiator support and replace them with threaded rivnuts. This makes it much easier since you'll have to pull the engine in and out a few times to get the clearances right. 

Note that JSPFab said in the swap kit instructions it was necessary to grind down the steering rack bracket on the driver's side, but I didn't actually have any clearance issues with it. Maybe this is for turbo engines only? 

For the most part, though, everything should slide in without too much difficulty. The worst part is fitting the transmission. The shifter hole has to be cut very far back to make it work. Ideally, you would want to use an RB20 transmission which shares the same/similar body as the s13 one but has the shifter about an inch further forward. Or you could use a Hardbody D21 transmission which will put the shifter in the stock AE86 location. I sit far back in my car though so I honestly prefer the s13 shifter location. 

The firewall had to be clearanced slightly on the driver's side.

Intake

For the intake piping I chose to make my own short ram style intake. This piece is 3d printed and places the air filter in the corner of the engine bay, similar to where the factory 4AGE intake is placed. The couplers and MAF adapter were also 3d printed. If you would like one let me know! 

Exhaust

The factory SR20DE manifold will bolt up with minor clearancing to the firewall, but the exhaust exit is in the wrong location. I don't think you could make it work without extensive modification. Since custom headers are expensive and off the shelf s14/15 headers probably wouldn't fit either, I opted for a SR20DET turbo manifold with the output flange cut off and a pipe welded to it. This allowed us to direct the exhaust in a more suitable direction 

Wiring

Wiring with the wiring specialties harness is very easy. Since my 

Fuel

I reused the 4AC fuel filter bracket which has a spring clip on it to hold a filter. This actually fits an S13 fuel filter quite nicely, I just relocated it to a factory bolt hole on the passenger side frame rail. I had already set this up when I put the 16v 4AGE in the car, so this part was very easy.

Miscellaneous 

Heater Valve

Following a Facebook post by Devin from Doctored Garage, I was able to rotate the heater valve 90 degrees. I believe he originally did this to clear the ITB setup on his Beams Corolla, however, it helps here too since the SR20 intake manifold sits pretty close to the firewall. You will have to grind down the arm that the cable attaches to a little bit since it will hit the pipe when rotated.

Regardless, the brake booster vacuum fitting will interfere directly with the heater valve. Instead of drilling a new hole for the cable or moving the valve over, I opted to look into a 90-degree fitting for the booster so I could get some additional clearance. This is still a work in progress, but I'll update you when it's done! 

Throttle Cable

The EnglishTune bracket worked well enough to get the car driving, but the AE86 GT-S throttle cable is slightly too long to fit, leaving a fair amount of slack in the gas pedal. I thought of two possible fixes for this. Either a spacer on the end of the cable where it meets the gas pedal or a custom bracket that puts the pickup further back. I've opted for the custom bracket, which you can see on our site!

The factory throttle wheel works, but the hole for the barbell end of the cable will need to be drilled out slightly to fit. 

Speedometer

The speedometer was actually very easy to get working. All it required was a cable drive pinion to replace the factory VSS on the s13 transmission. I used Nissan P/N 32702-58S20 which is from a Nissan R32/C33/S12. It only cost about $30 shipped from eBay.

I had to make a quick and dirty retainer bracket, just a small square of aluminum with a hole drilled in it for a bolt. The factory AE86 speedometer cable is long enough to work, and it also fits into the pinion without issue. This is an easy way to make your speedometer work! Note that the ECU will not be getting a speed signal, which may affect your fuel economy and other things. The AE86 cluster converts the analog cable input to a digital output for the 4AGE ECU and the factory cruise control computer, so I will be looking into wiring that up and converting the signal if necessary for the S15 ECU. 

Also, note that I'm not sure how accurate the speedometer reading is, I will update this once I get the car up to freeway speeds. It seems to be vaguely correct though. 

Tachometer

I attempted swapping the 30KOhm resistor on the tachometer board for a 10Ohm resistor as some people have done for Beams swaps, however, this did not work for me. I have been told that you can wire in a 2Ohm pull-up resistor on the tachometer signal wire to make it work, however, the downside is that you have a piping-hot resistor sitting under your dashboard now. I've ordered a tachometer signal booster from Widgetman and hopefully, that will fix the issue. Will update when it's done!

Oil Pressure Gauge

The factory AE86 oil pressure sender is the same thread as the SR20 one (1/8 BSPT), so this means you can just swap the senders and wire it up then you're good to go. This is still a work in progress but I believe it should work!

Coolant Gauge

The resistance values are different for the factory gauge cluster senders. However there is some overlap in the values, so using the SR20 one will be accurate for telling you when the car is up to operating temperature. However, I'm not confident that it will be accurate enough to tell you if the car is overheating. 

The thread pitches are significantly different. The factory AE86 one is M16x1.5 and the SR20 one is M12x1.25. From my research, a 1JZ-GTE sender shares sufficiently similar resistance values to the AE86 one, but is instead an M10 thread. This may be an easier approach, but I'm not too worried about getting it working 100% accurately since I have an aftermarket coolant gauge and a PiConsult installed in this car. 

Radiator

I used a Mishimoto SR20 radiator since it came with the engine. I think an AE86 Koyorad "Beams Swap" radiator would be better, however, this worked okay too and I didn't have to spend $400 on the Koyorad piece. The only issue with it is that the coolant outlet on the bottom will hit the passenger-side tension rod mount, so I found it necessary to install the JSPFab tension rod spacers. This was probably a good move anyway since they correct caster geometry after lowering the subframe. I paired this with a set of Yay Racing SR20 AE86 radiator brackets and it was good to go!

Fan Shroud

Still needs to be addressed...

Driveshaft

Pretty straightforward! Paid a local shop about $600 to make me a new one-piece shaft. The distance from the transmission output seal surface to the diff flange was 42.5" on my car, so I just gave them the specs and brought a stock S13 slip yoke and AE86 diff flange for them to order new versions of. 

Clutch Line

I chose to run an S13 clutch line on this car. I opted for the GKTech unit since it is slightly longer than some other aftermarket ones. The thread pitch on the master cylinder side is the same as the factory AE86 one, so it will thread in without issue. On the transmission side I am just using a factory S13 slave cylinder.