Thread: Highway cruising 300tdi

There are a lot of threads about this so try searc..but

No 3000 at 100 is too high..more like 2300 depending on tire size

Is the auto box moving into lock up around 80? If not, then 3000 at 100 makes a lot of sense and it is a transmission fault.

The generally accepted way to go about this with a 300tdi is

Get egt gauge
Adjust FIP
Mostly this is sufficient but if not then.
Bigger intercooler
Re adjust FIP ( bigger intercooler on it’s own without fip fiddling does little)

If you need more then

There are also tricks with adjusting boost
Then if you still need more then you are into the realm of better turbos including the hybrid style you mentioned.

100kph is normally around 2400 revs in my 300 TDI auto. IIRC the tacho signal come from the alternator so your replacement maybe giving a false reading.

Sounds like the alternator pulley to me also - just remember that if you install the correct one you'll probably need a longer belt.

Yeah i think it might be the alternator pulley too as when i calculate the ratio difference 3000 rpm at 49mm pulley diameter will mean 2400 RPM at 61mm diameter pulley. Hopefully thats it anyway. My auto gear up to 4th is almost smack bang on 80 as well. I wish it had a 5th though, then it would be perfect.

I guess my main question is whether any of the above changes (intercooler... turbo...) actually made a real world difference in 4th. I already have an egt and the most i could get it up to was 620 at id say about 105 yesterday on the sunshine coats Bruce highway (I think my top speed is 120 km/h on the speedo so about 110 in real world numbers). It has crept up to around 650-680 on big inclines (gateway bridge, bunya mountains) so i’m Somewhat hesitant to change my fueling without changing components like intercoolers first. I just feel it needs a bit extra due to the weight she’s carrying (its got “the works” in bullbar, winch, rear bar, rock sliders, big roof rack, lights, water tank, shelves in the back, dual battery etc.

Turbo, intercooler, changes will make very little difference to cruising at a constant speed. They will help when accelerating.

If the exhaust is restrictive it may hinder it a little.

I have adjusted my injector pump and boost on my 300tdi manual, it is much perkier now! Huge difference.
I wouldnt mind a VNT turbo for the increase in boost low down in the rev range.

I have a 96 300tdi manual D1. It has the Allisport Uprated intercooler and, as from about 4-5 months ago, a Hybrid turbo. When I fitted the intercooler, it has about 10% more power and will hold a little longer going over a hill. The Hybrid doesn't give it a lot extra power, but the power does come in a little lower in the revs, maybe 500 revs lower. The best description that I can think of is it is the difference between having a fairly heavy box trailer on when going over hills.

It definitely makes it more drivable and helps it stay at cruising speed a lot easier. Mine will easily sit on 120 or so without having the fooot all the way to the floor. Not saying that it will go much faster than that, but it is doing it within itself if you know what I mean. My car has nearly 304k on it.

Tom

Awesome, thanks Bmachining and Tom, some real world feedback is always excellent I think my course of action will likely just be an intercooler and FIP tweak at MR auto to help with some responsiveness. Ill see how that goes then consider some changes to the boost and or turbo unit and exhaust if I still feel I need a bit more responsiveness.

Tom mine is catching you up! 301k kms . Done about 40k in the last 2 years after doing 35k in the 15 years beforehand and 230k in its first 8 years or so of life. She’s certainly had a new lease on life since ive taken her on . Just trying to give her a fighting chance at keeping up with the highway traffic and not cause a backlog a mile long on every hill.

You should be able to happily sit at 120 all day long. If you can’t you need to fix what is broken.