4afe build ??!

[autocrosscelica]

Hello,
This thread is going to be following my 4afe build for my ‘91 celica st that I’ve been toying with for over 2 years now. Mostly suspension and brakes work (Had bimbos for a bit but am back on the bigger 92-93 fronts). This build is not gonna be quick as I am still in university but I have got some fun stuff planned that I don’t think has been documented that well yet.

Goals: I want to try and make power up to 6500 rpm naturally aspirated. I know what you’re thinking, that's stupid, it's just a torquey-ish economy engine. You’re right, I know that, but who doesn’t love a good challenge. If I wanted quick and easy power I would go 4age or 3s but I have accepted my fate. In typical engineering student fashion, I chronically over research everything but I am finally ready after 2 years to start using some of this useless knowledge about the 4a engines to build something. I do not have any power goals at all, it’ll make what it makes, but I am excited to go through the process and see the effects of changes in the future.

4afe History: The early 4afe (88-92 corolla/prizm, 90-93 celica) was essentially toyota throwing efi at the turd of an engine that never dies: the 4af. 1.6l, small journal bearings(40mm), small wrist pins(18mm), small valve included angle!(~22 deg) but the port slopped out horizontally to fit the injectors that were cast into the head. Not a bad engine but leaves some to be desired and can be hard to come by parts nowadays. The obd1 late 4afe is then introduced (93-95 rolla) along with the obd1 7afe (94-95 celicas, some corollas). This remodel is in every way better: journal bearings to match the 4age’s(42mm), same for the wrist pins(20mm), still narrow valve included angle but this time the injectors are moved to the manifold and the intake ports are a straight shot to the back of the valve. Bigger valves, buckets and cams as well as a pot style tps and electronic iac!!! Then finally, the obd2 4/7afe’s came around (96+ celicas and corollas). Nothing major here except having a crank position sensor and a proper cam position sensor instead of the Nippondenso CAS that doesn’t play very nicely with a standalone. I should also mention that the late 4afe and 7afe have the same head castings and components except injectors. Some claim that the 7a cams had larger lift cams, some said they were the same, idk. Out of all of these, I have found the 7afes to be the most abundant in junkyards and on FB.

The Plan: I got a cheap early 4afe on fb from a ‘92 prizm (maybe) about a year ago and have mostly sat on it till now. I plan to use this as my block because A: I already have it & B: a late 4afe has proven hard to find in the midwest. I should also mention that I wanted to stick with 1.6L because I like the bore/stroke ratio at 81/77mm for a NA ‘higher’ revving build better than the stroker 7a (lower piston speeds and little easier on the main caps which are a limitation on 7age builds). In the last couple weeks I have started collecting late afe head parts from the junkyard and some FB finds. Of those includes an awesome deal on a 6th gen celica head, so 7afe, that already had been resurfaced and the valves & valve seats recut (I tested with carb cleaner and some compressed air down the intake before I tore it down, flawless seal). The cams that were included had some slight rust. Evaporust would clear it up but the rust would come back slightly if you left it to dry (I have another set from the junkyard). This combination should be effectively a late 4afe with a slightly weakened bottom end (won’t matter for the power I’ll be at) and slightly higher lift (maybe? Conflicting answers online). All 1.6 cars had a 1.4mm head gasket but the 7afe had a .7mm HG. Things like this and shaving the head down give me the opportunity to bump compression up a little.
Wiring: I think I will end up with a Megasquirt product because there is a lot of support for it here in the US and I have a good local tuner. I also have read the documentation a couple times over the last 2 years and feel sorta confident. The microsquirt does everything I need it to but the MS3 would leave some room down the road for more inputs and outputs. I’ll price the two out down the road and make that decision. The major inputs will be the crank angle sensor from an obd2 late afe. This sensor is mounted in the oil pump so I will be pulling a CAS oil pump from the junkyard this weekend and test fitting it on my early 4afe when I make it back to the garage where the rest of the engine and the car is stored in about a week. The sensor reads teeth on the crank timing gear but the stock teeth are 36 tooth spacing with 4 of the teeth connected solid. I don’t believe MS can recognize this so I may have to get creative. I also have the option of using the stock obd2 late afe cam angle sensor in the distributor but I don’t intend on running full sequential on any outputs so I don’t think I will use it at first. The stock late afe tps is a pot style which is great and the map, coolant, and wideband sensors seem pretty straight forward. For outputs I will probably run a wasted spark setup with 2 batches. The fuel will be the same with batch fire of 2’s. I would also like to keep the functionality of the dash. If it proves too difficult I might go to a raspberry pi setup but I’ll give it a go first.

Limitations to Power: If you’re not aware, the afe heads are able to achieve this narrow head because they use a slave cam setup (the two cams are geared together and driven by one cam gear). Modern engines use roller rocker cams(cough cough 2ar-fe I love this engine) but the slave cam was still pretty cool for its time. Although we lose some adjustability, I think we can follow the footsteps of all the d series guys and still make some power. The lift of the 7afe cam I think will be sufficient to start actually (and being safe with shim over bucket) but where it lacks is in duration. Sitting around 220 deg stock, there is hardly any overlap at about 8 deg. I am curious if a regrind with a little bit longer duration and subsequently overlap would allow this head to scavenge and breathe a little better at higher rpms. But I plan to have the first iteration use a stock cam and then go from there. For compression ratios (9.5:1 stock) we can do about anything we want and reach the limitations of pump gas at about 12:1 (shell 93 is gold) without doing anything too crazy. 4age pistons are dropped in on a late 4/7afe bottom end and since the 4age has a larger combustion chamber volume than the afe’s have in the head, the piston is taller to compensate. So, 4age pistons + afe head = easy high compression. The valve reliefs in those pistons wouldn’t be perfect, but I think we could get creative if this build got that far. The manifolds on the other hand may be the end of me. The stock exhaust manifold just shoves all the ports together as fast as possible and although the stock intake is a cool 2 piece design, the runners are rather small. There is a mythological oem exhaust sold in certain European markets for a late 4afe head with a 4-2-1 design that might actually scavenge well but I can’t imagine the pain of tracking one down and shipping it over here. I have found one aftermarket header that looks okay but would be coming from Australia. And for intakes I am pretty sure there is only one aftermarket option and it is an overpriced billet unit that doesn’t even take advantage of the intake port angle. So we may have to get our thinking caps on for that down the road. I do have some experience with itb’s but that would be a last ditch hail mary option. Albeit awesome, it is very involved and can be very finicky. But it would give us a plethora of powerband tuning opportunities.

Updates will probably be infrequent due to me having very limited space to work on these projects while in school, but I will update as I start to test fit components. If you’ve made it through this blab fest, you’re awesome. Feel free to share about input, suggestions, and/or experiences with the 4a platform to keep me motivated 

Also how the heck do you post an image on here ?! haha

[cuttyman9]

Haha bimbos and you switched to 92-93 brakes haha.


Images it should allow you to add attachments underneath the text box, there’s a plus symbol next to it

[autocrosscelica]

Couple of interesting updates:
   Looks like the oem trigger wheel on the crank timing gear will work with MS. Despite the 4 teeth being joined, it acts just like a 36-2 tooth setup under an oscilloscope. This is good news because a 36-2 setup is good for wasted spark without a cam position sensor and I do not need to modify anything.
   Of course this all depends on if the oil pump and everything from a late afe block fits on the early 4afe block. But it should. I was able to make it down to the junkyard yesterday and pull a 96+ oil pump, crank timing gear and the vr sensor. I will be able to check the fitment of those next weekend.
While I was at the junkyard, I also grabbed a 1zz coil on a plug. I have heard that these are a good option for someone looking to retrofit a COP setup. They should work with the 4afe head if you sand down the outside insulation a little to make it slide in and out a little easier. I think this would be a cool upgrade but doesn’t really make sense right now. It would make wiring a little harder, not much, but a little. I’ve heard they don’t last as long as a separate unit because of the heat and lack of airflow which I kinda believe. It would make it harder to get a timing light on a traditional plug wire. But they also have their advantage as they would only be firing once per 2 revolutions. This allows it to have a better burn at higher rpm. Igniter dwell is something I still don’t totally understand but will look into later. I will probably wait to do this till the quality of burn becomes a limitation.
   Also the adjustable cam timing conundrum. I did some research and found 2 possible solutions as an adjustable cam gear is not offered for the late afe. However, there are adjustable cam gears available for the 4ac which is the same as the early 4afe and there obviously gears for the 4age. Here is some background info:
Early 4af/4ac: ⅜” pitch, 18/36(crank/cam # teeth) teeth, .75” width, square teeth
Late afe: 5/16” pitch, 24/48 teeth, .84” width, rounded       <- Has the trigger wheel we want
4age: ⅜” pitch, 18/36 teeth, .75” width, rounded
As you can see, the early 4afe and 4age are so close to compatible, but the early 4afe has square cut teeth on the belt and pulleys. This is relevant because a company offers a modified 4age crank gear that works with the 96+ oil pump and has a 36-1 trigger wheel on it. Since I have heard so much about people swapping 4age cranks into 4afe’s, I think it is safe to say the thickness and bore inner diameter of those two gears are the same but it is worth double checking. I also have a hunch that a 4age cam gear would mount up to any of the afe cams based on pictures but couldn’t find anyone online asking or confirming. We would obviously just use the exhaust one in that situation. So the two option are:
1: Use the modified 4age 36-1 crank timing gear with a single 4age adjustable cam gear.
2: Weld a trigger wheel onto the back of an early 4afe crank timing gear with the 4ac adjustable cam gear.
Both of these solutions would be around $200 but option #2 involves a little more time on the lathe and welder. However there is a little more room in option 1 for it to not fit. Sooo who knows. I think I will wait till I get everything running on the stock 96+ timing components for ease of setup. I also think that it would involve a lot more precision practices to time those 2 homemade setups without the original timing marks. So I will save that headache for later and stick to the stock stuff for now.
I will be finishing up my internship this week and heading back home for a tad so not sure how much progress I will be able to make until life settles down for a bit.
Excited as always, see ya

[autocrosscelica]

Got a few things ordered today getting prepped for the engine assembly next weekend. Went with an Aisin oil pump from the 96+ late 4/7afe's. I got some random gaskets and belts that I still needed for the bottom end. But it was when I started looking at water pumps that I realized a little hiccup. I'll attach some photos but the early 4afe and *I think* 16v 4ages had the coolant bypass routed outside the head to the thermostat housing. However the late 4/7afe's and *I think* the 20v 4ages all had there's routed through the head. No problem, just get a late afe water pump and use that housing to mount in to the head. That would be fine and dandy but my head is a 7afe. When I was at the junkyard I pulled the coolant pipe from the pump to the head but the 7afe deck is 15.4mm taller than the 4a deck. I do not exactly know where that material was added but I have a feeling it was above the water pump. So long story short, my water inlet hose would be too tall. I called around to a couple yards that car-part said they had 1.6 corollas and they wanted way too much for em. I think I found one of ebay that should do but it is still ~$40 that I didn't want to spend. So I ordered the Aisin late 4afe water pump (which is a dif part # than the 7afe) and will be getting a late 4afe coolant inlet pipe to go with. Hopefully everything fits up.

[cuttyman9]

So your goal is to use only factory parts?
I don’t mind odd builds as I’ve always had interest in 5sfe builds but I would use your head and bigger valves out of something else, also the rpm limit will have to be lifted as power without boost almost always requires that.

Also lightening the valve train will only help ya, I believe 1NZFE gave shimless buckets.

[autocrosscelica]

I did read the thread about the types of Toyota buckets so thanks. Yeah this iteration will include mostly stock parts considering my budget right now and allow me to get familiar with the standalone. This will be the first time I am wiring a car so simple is better right now. My plan was always to let it rev out some more. The issue right now is valve springs are pretty soft and the intake runners are little narrow on the manifold without any good easy solution at the moment. So the plan is get this running and on the dyno to see the power curve and then try to overcome some of the restrictions.

[autocrosscelica]

Only had the weekend to get out there to do some work. Stripped the block down to the rotating assembly, cleaned everything and then started building it up. Everything went together very smoothly as expected. Did the rear main seal, oil pump, water pump. Put new valve seals on the head while it was off before throwing the valve train back together. I felt like the timing belt tensioner was a little loose but it was a new spring for the 1.6 so maybe it doesn't need to be very tight on the non driven side. The coolant pipes were different as I suspected so it is nice that I was able to catch that. I unfortunately need to track down some new timing belt covers because the ones I pulled off at the junkyard are a little sad and the early 4a ones do not fit. I also am gonna get a torque wrench that goes down below 20 ft lbs. My lug nut torque wrench is not cutting it anymore for the finer things like the cam caps.
I didn't get a good back to back picture but the late heads intake ports are just so much bigger and more direct to the valve. I am excited for when we will be able to take advantage of that.