Pre-93 5SFE (and Gen2 3SGTE) vs Post-93 5SFE Distributor Writeup, Potential 5SFTE Owners: This is for you, EMS-related info. Options

[Syaoran]

This is going to be a write-up explaining the differences of both distributors and why from my experience the stock distributor on our 6GC (93+ 5SFE) is simply not an option if you're going to run an EMS such as the Megasquirt. It will explain why using the stock 2G 3SGTE or the 1st Revision 5SFE Distributor is your only option other than going 98+ Camry 5SFE Ignition setup which, for reference, consists of the following components:

1. crank gear with trigger wheel
2. oil pump with crank position sensor
3. cam sprocket with single tooth
4. cylinder head with cam position sensor
5. stock 98+ Coils or any other coil you decide to use

I'll start by giving you a picture of both distributors with their caps removed. You'll immediately notice the difference in internals and in overall body size.



As you can see, the one on the left is the pre-93 5SFE distributor (it came on 90-92 Camry(could be wrong), 90-92 Celica and 90-92 MR2) so they are really easy to get ahold of.

The right one, as you can see, has that huge thing on the bottom. That huge thing is the coil that has to fire 4 times per revolution of the crankshaft. I will explain why this is bad later on and why I don't like distributors for a forced induction application.

Coil:
This coil is stupidly small. I can't think of it being able to generate enough energy to light up anything effectively in a forced induction engine. This is why the 3SGTE never came with a coil inside the distributor in my opinion. One that is outside the distributor can both be bigger (more windings in the coil = more energy) and it doesn't heatsoak as bad (which increases the resistance in the windings and in turn diminishes the power it can produced /when/ it gets too hot, leading to a weak spark or even worse, spark blowout (no spark)

The duty cycle this coil has to go through in it of itself is already bad (which I believe it is 4 times per crank revolution, going based off of the trigger wheels, which I will demonstrate later), and is enough to generate concerning heat at high RPMs... another reason why I believe the 5SFE comes limited from the factory in terms of RPM limits.

To put it into perspective, here is (left) a Dodge/Chrysler 420a Coilpack (2.0 engine(as well as the stroked 2.4 version) in the USDM Eclipse GS, Neon, etc) vs the OEM coil inside the distributor (right)





Basically the coil inside your distributor is as small as 1 coil from the 420a coils. The 420a runs on a wasted spark setup with a 60-2 trigger wheel and sequential injection, all of which the 5SFE lacks. The 5SFE is as crude as it can be. Not a good thing for boosting it past stock CT26 levels...

Moving on, these are the trigger wheels inside the distributor. The one farthest into the distributor is gives the VR sensor a rising voltage signal, from what I can tell based on the shape of the "slanted" teeth (I would say it works sort of like a sine wave vs a square wave from the traditional toothed trigger wheels like the one you'll see next). The one close to the beginning of the shaft is a single tab, which I believe would indicate Piston 1 TDC, but I could be wrong:



In comparison, here is the other distributor (pre93 and 3sgte). As you can see it has a 24-teeth, which means that each tooth marks 30* of crankshaft rotation. (720*/24 = 30*), which makes it the crankshaft position trigger wheel (and its sensor the crankshaft position sensor on the distributor). It also has a smaller wheel below that is similar in form to the one on the post-93 with the slanted teeth, which I believe is the camshaft trigger/position. How it exactly measures TDC is beyond me. I haven't put that much thought into it yet.



Why any of this is important

If you're going to be running an EMS all of this info is vital. First of all, I wouldn't run the 5S boosted with a distributor. We've had fellow owners have a successful (although short) experience by just using a piggyback and boosting the engine all the way up to 3x its stock power (presure2 made 300WHP, and his has made the most because Cali-spec OBD2 Celicas came with sequential fuel injection). That isn't enough however, to determine that it's a good idea to do it that way in my eyes. If Toyota (and all other manufacturers) have improved their designs over time it's because the technology required for such designs were available back in, say 1998. It's 2013 and we're still using distributors. At the very least, upgrade to 98+ crankshaft position, camshaft position sensors and 98+ oil pump and coil pack.... In it of itself it's an upgrade, MUCH, MUCH better than running a distributor.

Alongside that, if you were to buy a 98+ head it would come with camshafts, which you could use to get them reground for at least a WebCam 294 grind. It woud give the 5S a very big boost in power with a tune, and we haven't added any forced induction, intake manifold or throttle body mods, no headwork or valve job or anything.

If you're going to run a Megasquirt (or any other EMS), my suggestion is that you eliminate the distributor and upgrade to the 98+ Camry electronics. I was having starting issues with the Megasquirt-II wired into the stock distributor.

An MR2 from a friend of mine who had the crank trigger wheel installed (using the pre-93 distributor as a camshaft position sensor) is running perfectly, with 0 starting issues. He was having starting issues as well before with the stock distributor (his is a 93, which comes with the same distributor as our 6GC)

After the stock distributor, he ran the pre-93 distributor and took of a tooth from the 24-teeth wheel to make it a 24-1, which is 100% compatible with the Megasquirt-II. He ran batch fire injection and wasted spark ignition with the 420a coils I showed you before. It ran great, but it was still crappy batch injection. Now he finally has the best setup easily accessible to us.

With the Camry electronics you can run fully sequential injection and coil-on-plug ignition with 4 coils. You just have to find 4 coils that fit and wire them up to the Megasquirt. (working on it)

In summary, if you're doing a stock turbo setup with a CT26, 2-bar MAP sensor, 315cc injectors and a Apex'i SAFC then don't worry about it, you'll be fine.

If you want real power with reliability, you HAVE to do this in my opinion and this applies to ALL 5S-FE (90-93, 94-95 and 96-99) inside a Celica. You will have a much better time doing it this way, even if it sounds like a lot of work right now. It'll save you much more work down the road, as well as make more power than the same setup but with a distributor. I would go as far as to say that most people that have said that piggybacks fight the stock ECU on our cars are wrong, and that the stock ECU is so dumb that there's no way it can fight any piggyback. The piggybacks simply have trouble picking up the signal from the distributor and interpreting it correctly. That is my opinion, and take it with a grain of salt because I could be wrong.

All of this information was given to you after analyzing the facts, calculating here and there and trying to understand. It is my interpretation of the information given to me by these parts and the education that I have which lets me interpret this information in a technical way (5 years of Engineering), which means I am in no way a professional or a Toyota Technician but I am doing this for me, for my own knowledge and have nothing to gain from this. I share it with all of you because I would like to see more 5S-FTE that don't blow up on the street after a dyno tune, or that have a ton of issues later down the road. This is a surefire way that any EMS will be able to control the 5S-FE engine properly and better than the stock ECU.

The distributor used to do this writeup will be put up for sale in case anybody needs a new distributor. It will include used rotor, cap and wires in good condition (less than 5,000 miles on the cap, rotor and wires and less than 500 miles on the distributor, bought new/reman.)

Thank you for reading this and I hope you learn something from it.

[lagos]

If you're going to be running an EMS all of this info is vital. First of all, I wouldn't run the 5S boosted with a distributor. We've had fellow owners have a successful (although short) experience by just using a piggyback and boosting the engine all the way up to 3x its stock power (presure2 made 300WHP, and his has made the most because Cali-spec OBD2 Celicas came with sequential fuel injection). That isn't enough however, to determine that it's a good idea to do it that way in my eyes. If Toyota (and all other manufacturers) have improved their designs over time it's because the technology required for such designs were available back in, say 1998. It's 2013 and we're still using distributors. At the very least, upgrade to 98+ crankshaft position, camshaft position sensors and 98+ oil pump and coil pack.... In it of itself it's an upgrade, MUCH, MUCH better than running a distributor.

I finally go around to reading this thread and wanted to bring up a few points.

1. There is nothing wrong with running a boosted engine with a distributor. All 3sgtes run perfectly fine with them. COP is great, and its an option with an aftermarket ecu, but saying that its a bad idea to use a distributor is really false. I'm also running the stock 3s distributor on megasquirt with zero starting issues or anything like that. Having said that, the cam signal on all Toyota distributors has a pretty high amplitude, and you have to use pull down resistors in the circuitry to get it to show up. I had to use a 33k resistor to get a perfect signal. However MS2 deals with the signal path of the cam signal differently than the DIYPNP that I am using. Almost no one was able to get the cam signal to pick up on a standard MS2, however with the DIYPNP unit, its just a matter of adding a resistor to pull the voltage signal down.

2. Pressure 2 engine was originally from a Cali Spec OBD2 car (it was actually my old engine), however when we swapped that motor in, we used his stock 94 harness, ECU, and distributor. So his engine made 300hp on a normal 94 OBD1 ecu (and an insanely high factory NA ignition map).

Now correct me if I'm wrong (I probably am since its been a while since I worked on a 5s), but I was under the impression that only the 7afe distributor came with the built in coil. I remember 98 5sfe having a separate coil, and I thought Presure2's 94 had his own coil as well. The only reason why we used his distributor was because the harness plug key was different.

This post has been edited by lagos: Jan 3, 2014 - 2:33 AM