Greddy Turbo Timer "Hiccup" Fix Mod
Conception and R&D
Testing and Certification
Sum up the researching process of finding the perfect turbo timer (for me) as well as detail the fix to the "hiccup" which occurs when engaging the timer function (i.e., turning the key to ACC or OFF) of the GReddy Turbo Timer. Note that this is only a known issue with US-spec MkIII Supras. The Japan-spec ones don't do it but other cars using the same harness might (and there are a few).
Background (choosing the best unit)
When I originally went to purchase my first turbo timer, I wasn't sure which unit to get. There were many issues left unresolved by group members. So, as usual, I had to take them on myself. The things I was looking for in a timer were the following:
To resolve the above issues and learn more about the unit's inner workings, I purchased both of the top two turbo timers out there (HKS Turbo Timer IV and the GReddy Turbo Timer) and hooked them up. I didn't even go near the newer "combo" models from various companies which combine the timer with things like electronic boost controllers or injector controllers. Such things are best bought as standalone units. Anyway, basic installation of each of these is extremely easy. It simply involves a "T"-in to the primary ignition circuit which the units will keep active once you turn the key and break the circuit. The similarities seemed to end there...
I hooked up the more popular HKS Turbo Timer IV first and was pretty much stunned at the fact that it hardly met any of my criteria. I wasn't sure exactly why people were drawn to this unit since it didn't shut down the accessories at all, didn't allow the alarm to arm and the build quality was just marginal. The whole thing was pretty much just a molded plastic case and they expected you to mount it with double sided tape. Give me a break.
Next, I hooked up the GReddy Turbo Timer and was again shocked. This thing actually did what it was supposed to do! The stereo along with everything else accessory-wise, shut down with a flick to the ACC position and the timer activated. It turned out that having a unit which shut down the accesssory circuit automatically proved invaluable since the alarm and TDSE boxes both looked for this simple occurrence as a trigger to allow their activation. Also, it proved extremely easy to then move the trigger wire for the headlight auto-off function from the key ON position to the key ACC position. This way the auto-off still worked as I thought they pretty much should. I wanted them off once the key was out and not sapping the battery while the car was idling nor staying on until the car shut off (and thus announcing to the world where the lone car on the turbo timer was).
As far as other extras, the GReddy TT was tops here as well. The build quality is excellent. The entire case is made of a cast aluminum chassis with integral mounting hardware included. This made it very easy for me to do my hidden mount in the center console with near-professional results. Functionally, the unit also ties into the emergency brake system like the HKS, but again, that's where the similarities end. The GReddy unit will sound a little audible alarm if you leave the e-brake down when engaging the timer! This will turn off as soon as you pull it up. If you then put the brake back down, the car will shut down (thus thwarting any would-be thief from driving away -- of course by now the alarm would be active too). The HKS unit would just shut the car off it the brake was down. Also, the GReddy unit allows you to tie into the speedometer signal going to the ECU (which I, of course, utilize). This will shut the car down if the unit detects movement of any kind. Such an example would be if the brake was up enough to keep from rolling on a small hill but the car was then attempted to be flatbedded. The car would turn off. Lastly, there's a tie-in for a Japan-only function, which I have yet to investigate, which supposedly allows the unit to act as a lap timer in essence.
Anyhow, I was happy and I was sure I had found the best timer for me. Now, on to the nitty-gritty...
Details on the Quirks
In turned out that both timers could have some of their quirks rectified, but one took me a
little longer to nail down. First, the HKS TT's inability to shut down the ACC circuit (that is
until the car shut itself off) was fixed by the simple cutting of a wire on its harness. I
typically shun such actions, but this seems harmless enough. Keith H., in his infinite wisdom
(and extreme good luck) happened upon this solution after a few months of calling HKS. He was
simply trying to recover the use of the factory alarm system when using his timer. He just
finally came upon the right person who knew the answer. For more details of his HKS TT fix,
Recover Use of the Factory Alarm when using an HKS Turbo Timer.
As far as the GReddy TT, the fix was a little more elusive since their really wasn't a problem in functionality -- per se -- yet I'm sure it's been seen by everyone running this timer on their MkIIIs. When the unit is engaged, there is a split-second loss of power. It's so fast that nothing blinks or anything, yet it's enough to make the car's ECU think you just turned the car off and on really quickly. Thus, the idle will come up a few hundred RPM and then settle back down. Also, the ABS system will reset and it's light will come on and then turn off. Lastly, the TEMS system will reset and you'll see it go from 3 lights back to whatever it's set at. This was deemed by a few of us as the turbo timer "hiccup". The whole scenario is no more harmful than turning the car on every morning or turning it off at the grocery store, but I wasn't that crazy about it. Other than that, the timer itself worked fine, the alarm armed and all was somewhat right with the world. But not to a perfectionist like me.
More Details (for the EEs out there :-)
I won't go into too much detail here (so I don't bore the majority of readers here), but starting in the early '80s and continuing up to now, all Toyotas have had a dual-ignition feed known as IG1 and IG2. IG2 is responsible for the running of your ignition system. This includes the ignitor, coils, cam position sensor, TCCS, etc. IG1 is responsible for the starting system. This includes the starter solenoid, theft deterrent system, cold-start injector time circuit and various neutral start switching. It also branches off to a lower amperage circuit to run the ACC or accessories circuit. This is a crucial piece of the puzzle since the HKS timer runs 4 things through it's circuitry; IG1, IG2, ACC and a 12V constant (for memory) (Click here for a reference schematic). GReddy sought a simpler approach, and really all that's necessary it seems by running just IG1, IG2 and the 12V constant through their system. This simple difference, it seems, turns out to be the reason the GReddy unit acts more normal than the HKS which seems to want to control too much.
Anyway, after much testing by me and getting GReddy Engineering on board both here and in Japan, we seem to have found the problem and the extremely easy solution. The problem, it turns out, is that IG2 seems to have a brief power flux when the key is switched off. This doesn't happen with IG1. Now all turbo timers keep both of these circuits active, but the circuit which is the catalyst for the engagement of the timer turned out to be IG2 and that's what caused the "hiccup". The reason the Japanese didn't pick up on it sooner and fix it before coming off here is because it simply doesn't happen on the Japanese-market car. Interesting huh?
The fact that it didn't happen over in Japan was verified by my new friend in GReddy Tech USA, when he went over to Japan to finalize a remedy with GReddy Japan. They took an '89 Turbo MkIII (like mine) and found that, as connected like mine, it worked flawlessly... BUT... if they reversed the IG1 and IG2 feeds into the timer, that they could duplicate the "hiccup". Thus, the hypothesis became that the problem could be simply solved over here by switching the IG1 and IG2 leads into the timer. Well, the very next weekend, on a sunny afternoon, Dane and I both did it to each of our cars and you know what? I worked!
Case solved. Here's exactly all you need to do...
The tools needed are simply:
There are basically (3) harnesses involved in the GReddy Turbo Timer hookup. You have a 4-pin connector coming off the timer itself along with the secondary mini-harness (for hooking up the e-brake, speedo sensor and race functions) (not shown in pic). An intermediate harness connects this 4-pin connector to the primary ignition harness "T" connector. The intermediate harness includes an integral ground wire which splits off independently for grounding and thus leaves a 3-pin connection on the ignition side. This just leaves the ignition "T"-in connector itself (shown as Main Turbo Timer Harness in pic). It's the "T-off" part of this connector that you need to modify. You will touch nothing having to do with the pass-through of your ignition circuit, so don't worry about creating problems, and for those of you who already have their timers installed, this is the easiest harness to gain access to. In '86.5 cars through '89, we just need to remove the panel below the steering column with a bunch of phillips head screws (easy with a power screwdriver) and for those '90 and up, you access the same panel via 10mm bolt fasteners.
To better help show exactly what you need to do, here's a quick digital sketch of the system I did:
Once you've removed the Main Turbo Timer Harness, you simply need to swap the BLUE (IG1) and GREEN (IG2) wires on the 3-pin connector. Don't touch the RED, since this is simply the 12V constant which lets the unit remember your presets. To remove a pin on the connector is fairly straightforward. Looking at the pin side (not the wire side), you'll see a little notch above each pin's connection point. If you look in there you'll see a slightly bent piece of metal (from the pin) which snaps in and anchors it to the plastic connector (a tang). You need to push in a small diameter pin or finish nail (we dremelled our own from a finish nail :-) in there and push that little piece down. Then, using the needlenose pliers and grabbing the connector (not the wire), push in a little (to dislodge the connector) and then pull it out. Repeat for the other side.
Then, since the tang will have been bent down from the removal process, lift it up with your nail a little bit and then reinsert the wires back into the connector in the opposite place. They will click when inserted fully.
Here's the Before and After of what you're going for:
Simply swap the BLUE (IG1) and GREEN (IG2) wires
That's it! Now, just reassemble everything back together (it can only go together one way) and enjoy...
Ok, somebody out there is probably wondering, "then why doens't it occur on the HKS unit?" My answer? Who knows :-) Since this turned out to be simply a harness issue, then they could simply have theirs flipped around already. Or, it could be flipped around internally on the board. Or, they could have internally spliced together something and piggybacked the circuit onto the ACC position. But really, I don't care very much since the unit just didn't impress me all that much. It does just the bare minimum of what a timer should do and for my money, I saw that you can get more out there. So I did. Enjoy the fix everybody!