Td5 bogging down at low RPM

[MLD]

Hiya all,

Before I go down the route of changing the truck's set up and potentially spending money on the wrong solution, I wanted to see if others are experiencing the same problem and if you found a solution.

The problem: at rock crawling speed the truck boggs down at low RPM and to get her into a usable torque range i have to give her a little throttle. She sparks up and overshoots the ideal speed making driving obstacles a bumpy and borderline uncontrolled experience. There seems to be a flat spot in the throttle control at the ideal speed for crawling.

The other negative experience I have is that she wants to run on in first low. ie move forward without acceleration at a knot of rates. Not a pleasant experience when you want to control speed descending a rock ledge. To get around it I ride the clutch to remove drive from the driveline. It's not ideal for control or mechanical parts.

Truck details:
110 TD5
TC, gearbox and C&P: standard gearing
Engine ECU: upgraded map from Bruce Davis (non-flashable)
Rubber: 255/85's MT (33")

Is this a TD5 trait? The ECU mapping? The larger rubber combined with the mapping? I appreciate one solution is changing the gearing of the TC. Not a cheap solution. The other solution is to change the C&P but i appreciate the taller gearing on the hwy.

Words of wisdom welcome

cheers Mark

[Frenchie]

The increase in revs is the anti-stall feature. I agree it can actually be counter-productive when you're slow rock crawling. I usually counter it with a little brake pressure though descending in first low I would have thought the engine would be revving above idle anyway.....

Must admit I haven't had any issues with bogging down in 1st low, I have the same setup (same tyres, BD chip)

[Yorkshire_Jon]

...The problem: at rock crawling speed the truck boggs down at low RPM and to get her into a usable torque range i have to give her a little throttle...

Mark,
Not sure Im following this correctly. Are you aware how the ecu plays with low 1st? The anti-stall will kick in if all feet are off the pedals so you shouldnt need to find the torque, it'll do that on its own. When you accelerate you disable the anti-stall.

To slow down (rather than stop), use the brake not the clutch. That way the ecu will keep the moto going and you remain in more control. If you need to go much slower for serious rock crawling then look at the Ashcroft Crawler-drive.

Standard running gear & your tyre combo wont give you any problems, if its all well maintained and problem free. I have no experience with the map you are running though, I do however know that there are good and bad maps - In fairness I would expect BD to use pukka stuff/maps that are specific to your ecu.

The good news is that if its a bad map, now your ecu is flashable, anyone should be able to re-program another chip and swap it out for you - all the hard work / soldering has already been done (converting from non-flashable to flashable).

All things being equal Id suggest that either the map is at fault (incorrect base ecu info for your specific ecu version), or its simply a case of managing / adjusting expectations of the TD5 and/or driving style.

hth
J

[MLD]

Hi Jon,

Dealing with your first point. When declining rock steps I'm moderating speed using the anti-stall speed while depressing the clutch a smidge to take pressure off the driveline and braking as required. If i didn't depress the clutch I'd fly off the ledge or stall by braking too hard to arrest the speed. In effect i'm using the clutch as an accelerator by engaging drive as required.

As to inclining rock steps: What i'm experiencing is probably what you describe as the line between anti-stall operating and me lightly pressing the accelerator thus disengaging the anti-stall. A flat spot where I feel there is inadequate drive because I've put the ECU in two minds. I then accelerate thinking it wants to stall.

I'm out and about this weekend weather permitting and i'll modify my driving to see if I am the problem. Will still need to resolve the fly like an Eagle attitude to declining rocks.

Bruce Davis said he'd play with the truck to see what the problem is and if it's the ECU map. There will be a solution.

thanks for the advice Frenchie and Jon.

Mark

[Yorkshire_Jon]

Mark,
When descending the rocks, do you generally drive along wit accelerator pressed a little and then lift off when you need to, or effectively stop, then crawl forward with no accelerator pressed?

Engine breaking in low 1st is most effective if you stop, engage low 1st (if not already selected) and setoff without pressing the accelerator. The engine breaking is not particularly effective if your moving beyond crawling speed and expecting the engine to slow you down just by lifting off the gas. Control the intial acceleration and thereafter with the brake, not clutch or loud pedal.

[wayne]

Hi Jon,

Dealing with your first point. When declining rock steps I'm moderating speed using the anti-stall speed while depressing the clutch a smidge to take pressure off the driveline and braking as required. If i didn't depress the clutch I'd fly off the ledge or stall by braking too hard to arrest the speed. In effect i'm using the clutch as an accelerator by engaging drive as required.

As to inclining rock steps: What i'm experiencing is probably what you describe as the line between anti-stall operating and me lightly pressing the accelerator thus disengaging the anti-stall. A flat spot where I feel there is inadequate drive because I've put the ECU in two minds. I then accelerate thinking it wants to stall.

I'm out and about this weekend weather permitting and i'll modify my driving to see if I am the problem. Will still need to resolve the fly like an Eagle attitude to declining rocks.

Bruce Davis said he'd play with the truck to see what the problem is and if it's the ECU map. There will be a solution.

thanks for the advice Frenchie and Jon.

Mark

Hi Mark
I had similar symptoms on my 130 and it turned to be the airflow meter.

Cheers Wayne

[MLD]

Thanks Wayne
I had a faulty air flow meter which was replaced when I chipped the truck. It's 8 months old. I will be dirty if it's gone again so soon. I'll check it.

Anyone in Sydney metro with a Nanocom that cares to share my company and your equip for a test?

cheers Mark

[Yorkshire_Jon]

Hi Mark,
I have full TD5 diagnostics and am based on North Sydney of that helps you out.

R
J

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[MLD]

Thanks Jon, PM sent. thx Mark

[Yorkshire_Jon]

Thanks Jon, PM sent. thx Mark

Good oh. I've set you an email.

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