Monday, November 13, 2006 - 12:54 pm, by: Mark Paddick(Sparks)
For the V8 owners the easy and best way is to aquire/adapt/fit an American SC400 ECU. These have a bit more aggressive tuning, slightly higher rev limit and no speed cut. Most US ECU's require 4 Oxygen sensors. ANY other way of doing it while retaining a factory ECU will have problems. The gearbox control will not know what the hell is going on and won't be able to change above the modification speed (usually 170kph) and the cruise control won't work either. You will also upset all of the systems in the car that use the 'speed' output of the dash, i.e. just about every system in the car (whether or not this will be a problem is unclear). Any claims to the contrary by manufacturers or others are pure bullshit.
Fot TT owners you need to find a version of the factory ECU that will work with your engine/gearbox and does not have a speed limit. Offhand I can't think of one (early 1JZ US Supra perhaps) BUT nearly all Mines, TOMS, Blitz etc ECU's have the speed limit code removed.
Monday, November 13, 2006 - 10:21 pm, by: Dan McColl(Hoon)
Mark Paddick wrote on Monday, November 13, 2006 - 12:54 pm:
ANY other way of doing it while retaining a factory ECU will have problems
I found a Blitz speed cut remover in my car and it seems to all work OK. Gearbox changes perfectly into top gear at around 179Ks. Cruise control will hold any speed. I'm not sure about any other speed outputs, though.
Monday, November 13, 2006 - 10:35 pm, by: James Johnson(Jamesy)
With the apexi RSM the car has trouble changing into overdrive (4th gear) at over 180km/h. if you do a quick pump of the throttle it will change up to 4th!
(think this is because when you let go the car thinks your cruising so it will go into top gear. then when you flatten it again you are going ot fast for it to drop a gear again. just a guess)
Only know this from laps of Phillip island. only place you need the speed cut! the race track.
Tuesday, November 14, 2006 - 04:25 pm, by: Jeff Wilkins(Calin)
James and Mark, mine has no issues whatsoever with gear changes over 180 with an RSM installed (series 2).
Since having the RSM I haven't tried using cruise control that high, will have to have a look. I used to set it at 180 pretty regularly to stop it hitting the limiter and 'bouncing'.
Wednesday, November 15, 2006 - 02:20 pm, by: Mark Paddick(Sparks)
Like I said. I don't care what you think. There ARE issues with gearbox control using any interceptor type mod (and the only way to do it right is to remove the code from the ECU; only Toyota, mines or Blitz can do that). Whether or not these issues are noticeable to the driver or even harmful to the gearbox/engine is immaterial, they are there and logic, experience and Murphy say that they will give trouble....and at the worst possible time.(a lot will depend on whether it is a TT or V8 gearbox; TT's are less complicated in their control and less likely to be affected). The cruise control will most definitely not work past the mod point but that is not really a concern, at least not to me. I wouldn't be using cruise at those speeds and I certainly won't trust something on my car that has known problems at those kind of speeds. I'd rather live with the speed cut (or stick in a nice cheap US ECU and have a few more revs to play with as a bonus).
Wednesday, November 15, 2006 - 02:53 pm, by: Peter Nitschke(Pen)
Like Mark says, an interceptor (eg RSM) just interrupts the signal to the ECU and makes it think that the car isn't going over 180kph.
Now as the car thinks it is only doing 180kph, it makes these decisions.
1. No need to use speed cut. 2. If throttle is not wide open, might as well use O/D 3. If throttle is wide open, might as well use 3rd gear.
So the main risk is, that if you are doing over 180kph and lift off a tad to get O/D, then keep accelerating to eg 240kph, and then slam your foot to the floor, the ECU may make decision 3 above.
I haven't been quite game to try it, I always keep my foot just off the floor above 180kph when doing track days.
Wednesday, November 15, 2006 - 10:17 pm, by: Dan McColl(Hoon)
Mine doesn't.
My cruise also works perfect. Speed calculated off tacho reading.
foot just off the floor will still give WOT, as the linkage at the top of the accelerator pedal is spring loaded. Gives WOT about 1 cm before contact with the kick down button.
Also, mine doesn't kick down over 180, even if I mash it after cruising at less than WOT.
I'm not trying to argue, just saying what mine does.
Thursday, November 16, 2006 - 01:47 am, by: Richard Johnson(92soarertt)
^ my SC300 does the same with a greddy (well did before i got a SARD ecu).
Speedo even read fine past 110mph, didnt stop working. Doesn't downshift going too fast, speedo works fine... I didnt even change any dip switches on the speed cut out of the box, i just wired it in.
Thursday, November 16, 2006 - 06:22 pm, by: Adam Barry(Acdchook)
Richard Johnson wrote on Thursday, November 16, 2006 - 01:47 am:
Speedo even read fine past 110mph, didnt stop working.
Yes, but being in the US, you'd have an analog gauge, so one would expect it to keep increasing all the way up to the end of the scale. On the digital dash, it will only read up to 180km/h, as the dash itself is not programmed to display any numbers higher than that.
Tuesday, November 21, 2006 - 12:08 pm, by: Matt Gill(Drifter4ag)
For the manual trans cars can you just cut the wire going to the ECU ? or will this stop the dash from working? I ran into issues at the recent drift round with the car cutting at 180kmh .. i just unplugged the sensor from the box but would rather have the speed displayed?
Tuesday, November 21, 2006 - 12:43 pm, by: Mark Paddick(Sparks)
The ECU is after the dash so no, it won't stop the dash but will upset the ECU (how much and whether it's still drivable is anybody's guess). You need to provide the ECU with a signal that doesn't change above about 170kph but is normal below that. One possibility is the Jaycar Digital Pulse Adjuster. It may be able to provide what is needed, it may not. If it works then it is fully adjustable and capable of non-linear correction which is really what you want. A speedo corrector kit would work but they are a linear corrector so you would alter the speed signal going to the ECU by a fixed percentage which is adjustable. The percentage to set would be calculated by; (((170 / (max speed car is capable of)) x 100)%
This will affet the auto behaviour a little at low speed as the ECU will think it is travelling slower by the percentage you set. This may or may not be a bad thing and may not even be noticeable if the correction factor is kept as low as possible (zero correction factor is zero change to the signal). Keeping the correction factor as low as possible while avoiding speed cut is the way to go. There should be no problems at all with a manual gearbox. With an Auto it is possible for the speed differential to be high enough between reported and actual speeds that the line pressure is way above what the ECU is expecting and it is possible for the ECU to tell the gearbox to do something quite stupid which it would not ordinarily attempt to do. This usually results in bits of gearbox where they should not be if it does happen. It may be a bit remote but it is a risk you take with autos over the 180kph limit.
Previous
