Is there a way to change rev limiter?

[IJ.]

LOL - I may be correct a good portion of the time, but I'm nowhere near infallible! And I absolutely don't mind being corrected, or worry about a good debate, years in management has taught me how to keep personality and real-world issues separate.

After all, I spend my days explaining to testers how to tell coders that they have made mistakes... hopefully without having to soothe injured egos on the development team for weeks afterwards.

Ditto always learning!

 

[jetjock]

Ditto always learning!

Lol, then take it from me: Learn to verify even when you trust yourself

 

[IJ.]

JJ: LOL Always end up triple checking even if I'm "certain"!

This is the beauty of such a huge resource like the WWW.

 

[3p141592654]

Shoot! I was hoping to finally see the assembler code. I pulled apart a supermonitor to try and see if I could extract the code, but it was using an unknown processor with markings D 151801-5300. I believe this is the same processsor used for the ECU. D probably stands for Denso. I couldn't trace it to anything.

Dr Jonez has schematics for a ROM dump and ROM add boards on his site. I wonder if he has done any experimenting.

http://mkiiitech.com/forums/viewtopic.php?t=334

 

[3p141592654]

3p141592654's explanation sounds more likely than mine, I hadn't thought of the decel condition until he mentioned it. Though there is still the question of why it would turn on and off at certain RPM, that's a pretty good fit for what the engine does just above redline...

I think it has some hysteresis to improve the drivability. Without it you would get a nasty surge if you happened to be coasting along near 1600 rpm with your foot off the gas. It cuts in a little above idle to prevent stalling.

 

[jetjock]

JJ, the cut happens above redline, though I'm not sure by how much, I'm usually to busy watching the track to keep any attention on the tach, especially if I'm running WOT in first gear. This is nothing like the cutoff that you get if the stock ecu thinks too much air is flowing through the engine, that is MUCH more severe, this is a much smoother bounce. Anyhow, keep us posted when you figure it out.

Ok, I've reviewed the factory TCCS manuals as well as the aftermarket documentation I have. All cuts, be they rev limiters, excess airflow, rpm cuts, ect, are injection cuts. Ignition is not involved.

I hadn't reviewed this material in years (as it delves much deeper into TCCS operation than is needed for normal troubleshooting) so I'd forgotten just how sophisticated TCCS programming is. A review of this stuff shows many misconceptions remain about what the TCCS does and when, whether it involves failed sensors, diagnostics, and the fail-safe and back up modes. It's a very sophisticated system for it's day so screw with it at your own risk. It's no wonder the engine sometimes won't run 100% right after messing with it even in minor ways. The bottom line is your stock ecu is a whole lot "smarter" than most realize.

You need to be careful modifying this engine while retaining the stock ecu because there are a lot of subtle things going on and it's easy to upset them. For a car used as other than a daily driver you can certainly live with them but the more you mod this engine and still drive it on the street the more careful you need to be. In either case you may not notice what's changed but the effects are nevertheless there. Keep in mind that although Japanese auto engineering is excellent they've long been a cut above when it comes to electronics.

If anyone wants I can do some write ups on the programming but in order to understand them you'll have to be pretty well versed in how the basic system works to begin with. Either that or if anyone has questions about a particular subsystem or operation (ISC, injection, timing, starting, ect) ask and I'll do what I can to pass on the information when I have the time.

 

[Nick M]

Ok, I'm NOT saying that anyone should push their redline... however, this logic is flawed.

The same engineers put fuel injectors capable of double the stock horsepower in the same car. They also built a bottom end capable of holding well over double the stock power. Furthermore, they built a chassis capable of holding 3-4 times the stock power levels.

I don't see how it is flawed logic to trust those that designed the car regarding where to set a redline.

Anybody that remembers a mechanical fuel governor has seen a different approach. It limits the total fuel. This doesnt cut the fuel, it is just all the fuel your engine will recieve. That limits total engine speed. Toyota may have taken a similar approach. Iam in the middle of the pacific ocean, I didnt drag old Toyota TM's here either. But they are quite useful. Next year I will look it up.:3d_frown: Not the factory repair manuals. They have made TM's. And the TSB's in 87 and 88 claimed to have a 6800 rpm rev limit. Toyota stopped putting out that sort of info in TSB's shortly after though.

 

[GrimJack]

All I am saying is that the engineers overbuilt everything else... so it's logical to assume they did the same with the rev limit.

Even so, I *still* don't suggest anyone push their rev limit unless they know what they are doing AND expect to replace / rebuild their engine regularly.

 

[Nick M]

All I am saying is that the engineers overbuilt everything else... so it's logical to assume they did the same with the rev limit.

You think they over did it when they decided on 58 lb/ft of torque for the head bolts?:biglaugh: (what would the internet be without a wiseass)

I know they over do things, I agree. But a rev limit after the advertised redline is probably there for a reason.

Somebody with a 5 speed put your pedal on the floor and see what it does. The old 5.0 had a 6250 rev limit after a 5800 redline. It didnt shut down fuel, it just wouldnt supply anymore, so the tach needle would bounce at the limit.

 

[GrimJack]

Truth on the head bolt torque. The theories behind this are varied and there are a lot of them - everything from a deliberate failure injected into the manufacturing process to avoid heavier tariffs on japanese imports, to printing mistakes on the TSRM, to alien influence on the design team.

Personally, I think that's just the exception that proves the rule.

Somebody with a 5 speed put your pedal on the floor and see what it does. The old 5.0 had a 6250 rev limit after a 5800 redline. It didnt shut down fuel, it just wouldnt supply anymore, so the tach needle would bounce at the limit.

I have done this rather often... my first gear runs out so fast (even when I can keep traction, which is rare) that I bounce off the rev limiter more often than not.

 

[jetjock]

My bet is on the alien thing .

Btw, my books confirm what Nick states: 6800 on the limiter. Fwiw when I bought the car I remember reading several magazine reviews that claimed the 7M behaved badly at high revs. I remember one claiming it had "serious inertial" problems. Funny, but I remember that just from the choice of words. So I went and took mine up to redline. Sure enough, it made such a racket I've never done it again. This is all on a basically stock engine though.

 

[IJ.]

JJ: I noticed this on my last motor with the 6M crank if revved hard (7000) it wasn't happy!

New motor with the 7M crank is turbine smooth at 7700!

 

[jetjock]

Neat. Are you implying the stock motor has a "6M" crank?

Btw, I'm familar with turbine smoothness. I also know what it's like to hold as close to a bazillion HP as you can get in your hand. Also neat

 

[IJ.]

JJ: Pre 89 has the 6M crank post has the 7M!

mmm love turbines one day we'll have access to em for cars!