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Increasing rev limit...

21K views 164 replies 34 participants last post by  shaeff 
#1 ·
Man theres nothing out there for us to do this. I want to raise it to 7k. Dont worry aobut whats needed mechanically, or what should be done ... thats for another thread. sole purpose of this one is to determine what can be done.

Option 1 - Standalone, big money to buy and tune, big hassle you have to know what youre doing and expect downtime, definetly worth it in the end.

Option 2 - Techtom from reg reimer. Almost as much as standalone, Not worth it at all IMO (cost vs benefit)

Option 3 - Greddy rebic LC (completely removes it) with ignition device that supports rev limit. Not too expensive, but rebics are RARE...

None of these options are acceptable to me, anyone have any ideas as to how to A) completely eliminate rev limit without affecting fuel maps and such. Or B)Actually raise it another way than those listed??

Thanks,
Ang
 
#2 ·
SuprAng said:
Man theres nothing out there for us to do this. I want to raise it to 7k. Dont worry aobut whats needed mechanically, or what should be done ... thats for another thread. sole purpose of this one is to determine what can be done.

Option 1 - Standalone, big money to buy and tune, big hassle you have to know what youre doing and expect downtime, definetly worth it in the end.

Option 2 - Techtom from reg reimer. Almost as much as standalone, Not worth it at all IMO (cost vs benefit)

Option 3 - Greddy rebic LC (completely removes it) with ignition device that supports rev limit. Not too expensive, but rebics are RARE...

None of these options are acceptable to me, anyone have any ideas as to how to A) completely eliminate rev limit without affecting fuel maps and such. Or B)Actually raise it another way than those listed??

Thanks,
Ang
damn SupraAng

you came up with a doozie.

If there is a way to trick it. IT has to be some sort of piggy back that clamps the signal at 6.2k RPM and then augments it itself (AN FCD For rev). Though what you ask is not easily done. At least not on our cars.
 
#6 ·
I always thought the Rebic was the fastest and easiest way to achieve this...are they really that rare to get a hold of??

Khris
 
#8 ·
But as ang said, the rebic *removes* the rev limit....Gotta have a cap on it at some point - But I'd be interested as to how it does it as well....If that can be found out, then an fcd-like product could be made pretty easily to bump it up a bit...even a 7000rpm rev limit would make a huge difference i think :)
 
#9 ·
MSD ignition can take care of the rev limit, so long as the rpm signal isnt clamped.

I wish ide bought the rebic off dr j from a while back, only reason i didnt is because it was 87-88 style harness.

Dr.J i looked on mkiiitech for some wiring diagrams of the rebic, couldnt find any? you have any, ide really like to know how it does it.

Ang
 
#10 ·
I'd love raise my rev limeter to like 7200-7500rpms. I didn't know that the Rebic could raise the rev limeter? I just thought it was a fuel tunner like the SAFR or SAFC??

Has anyone tried the computer upgrade from Reg Reimer?? It is supposed to raise the rev limeter and a bunch of other stuff like adjust fuel map and timing???
http://www.supras.com/~riemer/sonictech/techtom/

I'd just want to raise the revlimeter without buying a standalone unit.

Rcd
 
#14 ·
EMS is a standalone.

MSD cant raise rev limit, it can lower it, or set it. so if you found a way to take it out completely, you could rely on it to stop you from revving. (same idea as with a two step)

I have no idea how much of a difference there for 500 rpm (more like 250 for 6m crank guys) in fueling and timing. But i would prefer to look at my tach and have it say 7 as opposed to 6500.

Theres gotta be a way, just need to figure out how the rebic does it.

Ang
 
#15 ·
Where is your rev limit now? I believe that all supra's have a slightly different rev limit. Mine will rev to 7050 rpms. Of the 4 other cars I know, none of them have the same limit. They range from 6600 to 7100. Or is the limit change from 88 to 89 style ecu?
 
#18 ·
There is no way to fool the stock computer into driving the ignition to anything beyond the rev limit. If you clamp the frequency of the signal, you will be creating a rev limiter at that RPM. That is how rev limiters work. The pulses come at the set rate. If the engine tries to go faster, it will get more and more retarded until there is no power to rev higher.

The problem is that the ignition is synchronous to the CPS signal. The engine uses the RPM signal to know WHEN to fire the ignition, not just how much to advance it. For fuel, it just translates AFM frequency to a fuel flow, but it does not have to be in sync with the injectors.

The only possible way to increase the rev limit (besides reprogramming the ECU) is to drive the ignition signals yourself. If the Rebic can, in fact, increase the rev limit, then it must be directly driving the igniter.
 
#19 ·
durrrrr

shit i don't know why i didn't think of this before.

You can always do standalone IGNITION like the Electromitive HPX
6 cylinder. Still use the stock ECU for fueling requirements.
 
#20 ·
7k is rev limit? :wtf: i remember cruising around in my old NA and trying to see how long i could go before shifting while racing and it only reved to about 6500 and then bang would drop down. now im a bit older and realize that its not good to do that plus i have my turbo now. i would like to rev higher also but what kinda reliability issues would we have with the higher rev limit?
 
#22 · (Edited)
yes 89.5+ have lower rev limit than 87-89 due to the cranks.

I beleive rev limit is somehow associated with gears (maybe load) this is just from personal experience.

The fact is, while i can maybe get close to 7k on occasion, i want it to be 7k and not 6800 one time and 6600 another.

K dog, thanks for the info, do you mean to say, we need to "unclamp" the signal to get rid of rev limit?

This standalone ignition thing is another option for sure. But ide really prefer to just find a way to do something with the cps signal. And still have the car function properly. Sorta like an fcd. Let me know if you guys come up with anything else.

i would like to rev higher also but what kinda reliability issues would we have with the higher rev limit?
I really dont want to get into this in this thread, but I dont think anything will happen other than extra wear at 7k. Keep in mind youde need to make power up top to make use of it. If anyone does not agree start another thread, and ill be sure to talk it through.

Ang
 
#23 ·
K dog, thanks for the info, do you mean to say, we need to "unclamp" the signal to get rid of rev limit?
There is really nothing you can do because the clamping is inside the ECU. If the ECU sees a speed that is too fast, it will not send the ignition pulses any faster than the desired speed and the engine will retard until there is no power.

You could clamp the RPM signal to a lower level to make a rev limiter, but you can't go above the limit because it is controlled by the ECU.
 
#24 ·
K-dog said:
There is really nothing you can do because the clamping is inside the ECU. If the ECU sees a speed that is too fast, it will not send the ignition pulses any faster than the desired speed and the engine will retard until there is no power.

You could clamp the RPM signal to a lower level to make a rev limiter, but you can't go above the limit because it is controlled by the ECU.
the only way is to take ove the signal. there is not other way. But here is the problem with that. Ignition affects fuel unfortunatly. Because if you are spinning at 7k RPM and the ECU is controlling the injectors that a clip of 6.5k RPM. Then you will be running lean unless you direct control the injectors via an e-manage or OTHER fuel management system to increase fuel flow at this flow. Now you just made it more complicated.

I don't think you have to many options short of reverse engineering the toyota ECU (perhaps TRD japan still has these maps) and raising those limits.
 
#25 ·
why would anyone want to risk increase the revs without some head work, at least valvetrain. im not sure buy anything beyond 7k and its approaching floating valves. . even though i shouldnt talk cause my head is stock and im in the 7k area every now and then - vpc safc avcr is all i got..
 
#26 ·
Why would anyone say it can't be done when not one person on this board that I know has tried it and failed? ;)

I've hit 7000 many times on my 87 however, depending on gears and how fast i get there depends on cutoff... usually 6700 is when I hit rev limit. 7000 isn't extremely high from 6700... I really don't think 300 RPM for 1-3 seconds is going to cause a big mess.

Main reason is so I can ride out the gear to 6500 and when I shift NOT hit rev limit.
 
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