V8 TCU in TD5

**AK83** · 14th August 2022, 09:16 PM

Originally Posted by twr7cx

Question - why fit a V8 TCU and tune it to suit the Td5 rather than adjust the Td5 to suit better? Is it a case of the V8 one being tuneable and the Td5 one not? Or is the V8 a better/closer starting point?

If you want to get serious about this then the Compushift is the way to go but it's a lot of output and then still requires you to figure it all out and setup to suit - Jose of Td5Inside has previously described a wellsetup one in a D2 as being able to drive like it's a 6 speed transmission in it's effect - I've always been surprised that there isn't a tuning market for this like there is for the ECU's...

If it were easy to just 'tune', then of course this would be the way to go, but AFAIK, the TCUs aren't 'tunable' .. hence why something like the compushift product exists.

My experience with the swap to the V8 TCU is like a 'poor mans 6 speed'.
As I said earlier, I use it held back in third most of the time, even at 60k/h. Only if I know I can sit at 70 for an extended time(at least a few minutes), hit 4th.
The early lockup in 3rd, and the strong pull of the mapped TD5 are a perfect match. Not quite as strong as the V8 down low, but maybe 90% or so.

IIRC, one major gripe with the std ECU in bros tuned TD5 was the 2nd to 3rd shift point, always felt far too delayed when stuck in heavy traffic that hardly moved at 30-40k/h.
In fact as I recall, all gears just held on too long.

The reason to plug in a V8 TCU would be ease and cost of getting one. V8 D2's are easier to find at the local wrecking yards (u pull types) ... TD5s at those wreckers .. I've only ever seen one, once in about 5 years(pick-a-part) .. lots of V8s.
I dunno how much they sell for, but from other bits I've recently got from pick-a-part, I'd guess about $30 or so.
Compushift would be nice, as it allows user preferred tuneability .. but at over $1K!!

If you don't use cruise control, just swap to a V8 TCU and you'll immediately feel the difference. But if you use CC a lot like I do, if it turns out like my experience, you'll hate it.

**twr7cx** · 15th August 2022, 12:50 PM

I mistook some of the earlier conversation to be about adjusting the TCU when rereading them now it was the ECU being discussed. My bad.

Originally Posted by AK83

...just swap to a V8 TCU and you'll immediately feel the difference.

As I described previously I've previously tried the V8 TCU and it was a significant downgrade in driving behaviour.

**AK83** · 16th August 2022, 10:27 PM

Originally Posted by twr7cx

....

As I described previously I've previously tried the V8 TCU and it was a significant downgrade in driving behaviour.

If you're ever in Melb, feel free to contact me and take this one for a drive. Would be interesting to hear your experience/opinion.

**johnp38** · 17th August 2022, 12:44 AM

Originally Posted by twr7cx

As I described previously I've previously tried the V8 TCU and it was a significant downgrade in driving behaviour.

There are different versions of the V8 TCU, the high compression ones suck big time as they are too touchy and quick to kickdown and hang on.

I have 3 V8 TCU.

The one that worked best out of mine was the UHU 000 020 which I am pretty sure is low comp 4.0 V8, it cost me over 100 from some wrecker/mechanic in TAS

The other 2, one is IGG 000 010 got locally from u pull it for 35, the other is IGG 000 040 from ebay (sydney wrecker) 45 delivered.

The aussie sellers generally want around 100 unless you go to a pick ya part ya self type place or jag a cheapie online.

If you are handy with mechanicals I would still go the V8 torque converter and ashcroft kit first, the V8 converter will bring your revs down to around the same as locking up the Td5 at lower revs using the V8 TCU but you wont have the touchy feely driveability issues at higher speeds.

My disco with stock tune was quite happy locked at 60k with the V8 TCU and could pull to 90 easy staying locked as long as I was not too aggressive on the loud pedal. Unfortunately after that it was a bit harder to keep it in top gear if I put the foot down even with the better performing of the 3 units I have.

**Cambo_oldjaguar** · 17th August 2022, 08:42 AM

Our tuner already did some work on the 4HP TCM used in the Jags, I know the LR versions are not exactly the same but similar enough to be not starting from scratch.

If someone has some spare modules on hand, V8 & Td5, I'd be happy to have a look at them and see what we can do in regards to modifying the tunes.

**Cambo_oldjaguar** · 17th August 2022, 08:45 AM

Originally Posted by Rymnd

But to slightly hi-jack the discussion, anyone come across this before?

Auto Gearbox Tuner for Land Rover Discovery 2000 - 2004 2.5 TD5 - 138HP

If it's doing the same thing as their other products, it's quite a dangerous thing.

In the 6HP26 all these devices do is corrupt the EEPROM with the adaptation values, sets them all back to zero and prevents re-learning.

**Rymnd** · 19th August 2022, 08:17 AM

Originally Posted by Cambo_oldjaguar

If it's doing the same thing as their other products, it's quite a dangerous thing.

In the 6HP26 all these devices do is corrupt the EEPROM with the adaptation values, sets them all back to zero and prevents re-learning.

I actually have an update on this, as I enquired what exactly they do to the TCU. They replied that it wont flash the TCU directly (as shack also mentioned) but it will make changes to ECU that will make the gearbox shifts faster and lock up earlier.

So this leads me to the question as to why the TD5 tuners can't make such (faster shift/early lock-up) changes (I've asked and was told it's not possible), and if it's maybe the case that Nanocom doesn't pull those maps down. Or that it gets pulled down but they're not identified?

**shack** · 19th August 2022, 08:59 AM

Originally Posted by Rymnd

I actually have an update on this, as I enquired what exactly they do to the TCU. They replied that it wont flash the TCU directly (as shack also mentioned) but it will make changes to ECU that will make the gearbox shifts faster and lock up earlier.

So this leads me to the question as to why the TD5 tuners can't make such (faster shift/early lock-up) changes (I've asked and was told it's not possible), and if it's maybe the case that Nanocom doesn't pull those maps down. Or that it gets pulled down but they're not identified?

Shift points are controlled by a number of things, but the final decision as to the lowest lockup point is calculated by the TCU, and from my endeavours this appears to be hard wired.

Some other things that the TCU gets from the engine ECU can be modified to improve driveability... But of course what is desired changes between drivers.

There are no "maps" in the engine ECU that this will be changing that are unavailable to most tuners.

As Cambo said, I'd be pretty wary of this product.

I'm currently working on TCU mapping at the moment, I've got some stuff sorted but it's gonna be awhile..

**Rymnd** · 19th August 2022, 03:34 PM

Originally Posted by shack

I'm currently working on TCU mapping at the moment, I've got some stuff sorted but it's gonna be awhile..

It’d be well worth the wait if one can get faster shifts and earlier lockups! It might revolutionse TD5 life, as we know it. 😁

**shack** · 19th August 2022, 11:25 PM

Originally Posted by Rymnd

It’d be well worth the wait if one can get faster shifts and earlier lockups! It might revolutionse TD5 life, as we know it.

What do you mean by "faster shifts" ?

Earlier shifts? Or less engine retardation during shifts? Or just a quicker shift?

The ECU has I believe "target shift times" and it attempts to adapt modulator pressure to achieve this.

I don't think much is to be gained by playing with the actual speed of the shift, other than killing the auto quicker!

It's so long since I've really driven a stock auto with stock ECU and TCU tuning, I can't remember what they are like, probably ordinary... Which is why I started tinkering.

Cheers
James

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