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6th Generation (1988-1992) Specific discussion of the AE92

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Old 11-30-2008, 09:12 AM   #1 (permalink)
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4afe ECU modifications

OK
so i've seen a few 'modified' 4afe's and i know they aren't uncommon in AUS even as a taxi!!!

there is supposed to be a way to give the computer a slightly more-aggressive map elongated to meet a higher 7200 rev limit

anybody have some info to offer would be much appreciated...

im about to run 7psi and a richer curve would really help and eventually i'd like to run 4age on 4afe electronics!

Note:i also have larg-port ecu so if that could be modified for 4afe i'd be just as happy
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Old 11-30-2008, 03:36 PM   #2 (permalink)
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Change the crystal speed of the ECU. That's how people get the higher redline.
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Old 12-01-2008, 12:28 AM   #3 (permalink)
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crystal... like on a pager??

can u clarify so i don't blow up my car lol
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Old 12-01-2008, 01:26 PM   #4 (permalink)
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Basically the same thing. The crystal controls the clock speed for the computer. If you increase the clock speed, you'll speed up everything that the ECU controls. If you increase the clock speed by 10%, you should get an 10% increase in your rev limit. It'll also change when TVIS activates, how long your injectors fire for, and probably some other stuff.

This is all second- or third-hand info from me. Toyotaspeed90 knows a lot more about these than I do.

I don't know what safe values for the crystal are. The person who modded Toyotaspeed90's ECU hasn't posted the specs (that I'm aware of) and charges/charged $100 for the service.


Look up overclocking old computers for basic details on crystals and clock speeds.
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Old 12-01-2008, 04:15 PM   #5 (permalink)
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i know how to over clock a computer but i dont have a bios on my rolla lol...

so would i be replacing the crystal with a higher frequency??? that is how pagers work...
diff crystall=diff frequency

i have a ton of old crystal equipment at my work for re-crystaling pagers

i appreciate any and all info including contact info on the *modder in question i wouldn't mine paying 100 bucks as long as it works on the setup i am using and would possibly change
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Old 12-01-2008, 06:21 PM   #6 (permalink)
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Yes, same thing.

I mentioned "old computers" because that's how we used to overlock them "back in the day" (as the kids say) before you could do it in BIOS. It's just changing the mhz the FSB runs at.



Just a quick math exercise:

M = stock ECU mhz
R = stock rev limit

M * (72000 / R) = new mhz


I vaguely recall that the stock rev limit is 6800. And let's just make a wild-ass guess that the ECU runs at 16mhz (that's what 5SFEs run so it will either be the same or lower).

16 * (72000 / 6800) = 16.94mhz


If those numbers are correct, you're in luck because one of the more common crystal frequencies is 16.9344 (common because it's an integer multiple of 44.1khz).

Hope this helps somebody somehow.
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Old 12-01-2008, 06:55 PM   #7 (permalink)
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stock rev limit is 6300, not 6800
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Old 12-01-2008, 07:35 PM   #8 (permalink)
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That might be a problem. 14% is a big increase.


Quote:
Originally Posted by jmaz87 View Post
im about to run 7psi and a richer curve would really help
This mod will lean out the car because the injectors will be firing for less time.
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Old 12-01-2008, 08:07 PM   #9 (permalink)
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Quote:
Originally Posted by Ghostyman View Post
That might be a problem. 14% is a big increase.
exactly why i said to him to keep the 4A-FE stock

and for the record, if you want to know the rev limit, just get a rpm and get it to the rev limiter, normally toyota cars with an ECU usse an rev limiter that is setted to cut straight on the redline (in this case, 6300)
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Old 12-02-2008, 08:25 AM   #10 (permalink)
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yes it's 6300 with 4afe but sometimes it seems i get to 6500 without smacking anything...

i was gonna use slightly larger injectors with a 12:1 FMU and a rising rate FPR and retard the timing a bunch

this is an otherwise stock 4afe with a t25 getting smacked on..

so is a 7000 rev limit out of the question??? im more interested in affecting the map at this point.
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Old 12-02-2008, 10:08 AM   #11 (permalink)
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Quote:
Originally Posted by jmaz87 View Post
yes it's 6300 with 4afe but sometimes it seems i get to 6500 without smacking anything...

i was gonna use slightly larger injectors with a 12:1 FMU and a rising rate FPR and retard the timing a bunch

this is an otherwise stock 4afe with a t25 getting smacked on..

so is a 7000 rev limit out of the question??? im more interested in affecting the map at this point.
I imagine if you increase the size of the injectors by the same percentage your increasing the clock speed, it should be fine, maybe a bit bigger.

EDIT: also have you looked into getting a Megasquirt ECU? it would solve all your problems

www.megamanual.com
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Last edited by eage8; 12-02-2008 at 10:10 AM.
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Old 12-02-2008, 10:23 AM   #12 (permalink)
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Wink

It's no wonder why I see so many posts with blown engines.. why do some people want to rev way past the power curves? (on the downside of the power curve the power drops off fast) The power on these stock put-put engines drops off before they crazy rpm's people push these stock engines to (power curve drop could be as low as at 5,000 rpm). If the drivers want more power and at higher rpm's you really need to build the engine to put the power out at those RPM. (valve springs, compression ratio, intake and exhaust components) But, that is really a waste of money to get 10 more hp out. When you push the engines, damage them, and damage the tranny, clutch and other drive train componenets, you wil just waste time and money.

If the engine needs rebuilt, that would be the time to add some higher performance parts, but like I said, for what? 10 more HP? You are better off doing something else with the money.

IMHO
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Old 12-02-2008, 10:58 AM   #13 (permalink)
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I'd normally agree but in this case he's putting a turbo on it. If the internals can hold it, he'll want the extra revs.
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Old 12-02-2008, 05:44 PM   #14 (permalink)
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Quote:
Originally Posted by jmaz87 View Post
yes it's 6300 with 4afe but sometimes it seems i get to 6500 without smacking anything...

i was gonna use slightly larger injectors with a 12:1 FMU and a rising rate FPR and retard the timing a bunch

this is an otherwise stock 4afe with a t25 getting smacked on..

so is a 7000 rev limit out of the question??? im more interested in affecting the map at this point.
the famous 6500 on that you see on the tachometer is in fact 6300

above 4000 RPM the toyota tachometer (dont ask me why) display 200 RPM higher than the real engine speed, probably something that got to do with the age of it (most of the car and pieces have nearly 20 years old if not a little more)

Last edited by Rookie_One; 12-02-2008 at 05:45 PM.
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Old 12-02-2008, 05:53 PM   #15 (permalink)
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EXACTLY RIGHT!!!

i don't care about 10hp blah blah those extra 700 rpms will give me more room to play in rather than smacking the limiter every other gear understand??? driveability not performance (under boost the power drop will be slight)

the reason i haven't just bought MegaSquirt is the cold-start issue... 4afe has a cold-start injector and nobody would be able to give me proper fuel-timing for that injector and my car would never start on a dime again...

if i was only autoX'ing then MS away but then i'd just use my 4age and would have no problems
im using the 4afe as a base because im still rebuilding my large-port and 4afe parts are very cheap...

If i blow the motor it will be a huging learning experience i will cry for a second, then start putting in my COMPLETE SPARE MOTOR

im not one of those guys who spends all his money on a turbo-kit,blows up car and then bitches about shitty parts

i started with my suspension and brakes then moved to weight reduction, safety and tires... now that i have a spare motor, a 3rd block and a bunch of stuff in between i want to see what gains low-boost will have on 4afe...

i'm thinking about getting base-dyno 70$ for 2 pulls im guessing around 85WHP hoping to make 120whp at about 8psi THIS IS WHY I WANTED TO MODIFY ECU
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