slow defender

dave_b · Jan 1, 2016

hi ya, just after some advice if you don't mind

i've got a 300tdi that has a egr blank and a decat down pipe.
but it just seems slow, hates being much over 60 on motorways.
i'm running 33x12.5 15's. but that hasn't changed the fact it doesn't like anything much over 60mph
what do you suggest changing to make it less revvy and happier cruising at 70mph
cheers dave

Jonnyb1990 · Jan 1, 2016

Give a full service, does wonders,

Other than that check the fuel pump, has it been tampered with or is its anti tamper plate still intact, if it hasnt been attack, drill it would and turn right a 1/2 turn, will go better, if it has been tampred with, make a mark where it was and have a little play, may be over or under fueling,

Check sediment filter, can cause fuel starvation affecting performance,

Other than fitting a disco transfer box, not alot you can do on the cheap,

If you have deep pockets, theres a 2 stage turbo available from allard motorsport I think

flat · Jan 1, 2016

Tyres more appropriate for motorways would help I would have thought, them ones you have are quite large lol

dave_b · Jan 1, 2016

yeah that are a tad on the large side. and i like the look

dont do much motorway driving, but its something i dont want to dread if i have to use one
will try and have a look at the fueling and see if it needs adjusting
cheers for the suggestions

Turboman · Jan 1, 2016

dave_b said:
yeah that are a tad on the large side. and i like the look

Maybe so. But big tyres are always going to take a lot more power to drive, extra diameter, more rolling resistance, plus you have to move the weight of the tyres themselves.

Probably the root cause of your performance issues.

dave_b · Jan 1, 2016

doesn't seem any worse since fitting them in all honesty
cheers dave

blackstrat · Jan 1, 2016

ur speedo will be out remember

IamRobbie · Jan 1, 2016

Transfer box?

109inches · Jan 1, 2016

You won't notice them on slower roads as you'll be in the torque curve more of a tdi. However when getting on to an open road in the higher gears and revs the engine will just give up.

You could buy a boost pin. I have one in my 200tdi defender and improves it quite a lot. The acceleration will push you into the seat.

Fitting a disco transfer box will make it worse as those wheels have upped the gearing too much. Meaning the engine doesn't have power to increase the speed past 60mph as you have to remember wind resistant is quite large at that speed which means more power is needed to overcome it plus more force needed to turn the bigger heavier wheels. Slap some 7.50/16 road tyres on.
Unfortunately mate you'll either have to put up with 60 or lose the monster truck look.

What might help if you want those big wheels is a 1.6 transfer box from a 110. Unless you need those wheels for off-roading or a practical reason, logic would dictate you go for a smaller wheel size.

_Stingrey_ · Jan 1, 2016

I suffer from similar issues.
Check your lift pump.
What boost are you achieving?
Do you have any boost leaks?
Check the diaphragm isn't split inside the boost compensator on your fuel pump.

I fitted a boost gauge and identified that I'm only producing .4-.5 bar boost max. I think I have a leaking intercooler so I have just purchased a replacement. If this proves not to be the route cause then I will be replacing my turbo as there is a little play in the turbine.

dave_b · Jan 1, 2016

cheers for the info...i appreciate what your saying about the tyres, but they will be staying.
is it worth playing with the fuel pump or go straight for the boost pin ??

flat · Jan 1, 2016

Get the fuelling spot on first so you get max effect from the boost pin.your top end won't change that much though to be honest so you will have to just live with it

_Stingrey_ · Jan 1, 2016

Whats a boost pin?

dave_b · Jan 1, 2016

cheers flat... will try and have a play with the fueling tomorrow

Coffeelandy · Jan 1, 2016

Go for the boost pin Mate its easy as anything. You'll notice immediate results but be mindful that your truck needs to be at factory settings.

IamRobbie · Jan 1, 2016

I removed my boost pin as I thought it was a load of rubbish... Felt like the truck wouldn't move so it's gone back in lol

Shanec · Jan 2, 2016

Where do you buy your fuel from? You may be interested in increasing performance by altering your fuel. A hydrometer is a good starting point.

top drive · Jan 2, 2016

i found it much cheaper to sit with the trucks in the slow lane.... not to mention more economic.

Turboman · Jan 2, 2016

top drive said:
i found it much cheaper to sit with the trucks in the slow lane.... not to mention more economic.

Yep! Me too!

Its a tractor, so why not drive it like one!

marktdi · Jan 2, 2016

Check your boost presure first . Inspect boost hoses to make sure they are all sound and not leeking . dont waste money on a boost pin for the pump diaphram as you can adjust the standerd pin for free . Take the top off the diaphram housing on the pump and move it clockwise 1/8th of a turn then have a drive and see what its like . There is no point in messing with the fueling untill you know the boost presure is right

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