Safe revs?

[serenitycamper]

Hello people, I have a slight dilemma which is beginning to bug me.

I have an '88 T3 with original 1.9 DG and original gearbox (don't know which code) and I need to know what is a safe rev limit to run at consistently. I have never driven the bus over 3500 RPM which is about 60-65 but its becoming increasingly annoying not being able to even keep up with lorries and having no power to speak of. I've read that the safe limit is 5400RPM but on a 26 year old waßerboxer with original head bolts and gaskets, I'm not exactly sure that would be a good idea. I've also read conflicting reports of people saying you should be gentle with them alongside other opinions saying they were built to be revvy engines. So which one is it? Can I tootle along happily at 4400RPM which is the end of the green hatching on a stock rev counter, or am I likely to blow the s*%^ out of it?

Would fitting a 2.1 with the 1.9 Pierberg carb help matters?

I'm also considering contacting Aidan regarding stretching the legs of the box with 3rd, 4th and final drive. Would this benefit the cruising speed and if so what would it do to the ability to climb hills? Obviously this is a while off due to the cost but I'd like to know to formulate some kind of plan.

Thanks in advance

[Dad]

I think the longest gearbox is only 19mph/1000 rpm so 4000 revs would be 76mph. I'm not sure id want to go much quicker than that, I cruise at 70-75 (indicated). Bigger tyres will bring the revs down abit. A 2.1 will climb hills better.

[CovKid]

Its not cheap changing gearbox ratios. I'd concur with above although I can definately beat some 2.1's uphill owing to reduced weight (the vans not mine).

If you're running on 14" wheels, shifting up to 15" can help a lot. I found it made the speedo right at last and the bigger rolling circumference seems to come into its own when you're cruising - it gets into a comfortable stride without having to rev the heart out of it and providing you're not thrashing through the gears to pick up speed all the time, it can be reasonable on fuel. Consider/try that route first before embarking on gear cog changes as it may well do the job for you and is relatively cheap to do.

The VW is almost agricultural so its not designed to rev like modern engines but there are a few things you can do to improve things, the above being one of them.

[serenitycamper]

Well I'm already running on 245 40 18 to keep the rolling diameter as high as I could whilst maintaining the look that I wanted. According to my calculations using an online gear calculator and brickyards data currently my 3000 RPM is 55 mph. After Aidan's fettling (£550) that would increase to 71mph. That's a massive improvement for our setup. In the meantime however, I don't want to blow it to bits!!

[syncronized]

I don't know the power/torque curve of the DG engine but are you sure it would have enough beans at 3000rpm to pull the van along at 71mph?

[shepster]

Well I'm already running on 245 40 18 to keep the rolling diameter as high as I could whilst maintaining the look that I wanted. According to my calculations using an online gear calculator and brickyards data currently my 3000 RPM is 55 mph. After Aidan's fettling (£550) that would increase to 71mph. That's a massive improvement for our setup. In the meantime however, I don't want to blow it to bits!!

I think you'll do well to hit 71mph at 3000rpm with a 1.9dg engine, theoretical gearing calculations are all well and good but you need the motor to do it.

I swapped my 1.9 for a 2.1 and run 215/60x16" tyres which gives a slightly overall increase in gearing, Aiden also built me a gearbox with longer 4th and my van now sits at a GPS 70mph pulling around 3600, prior to the changes it would be revving at 4000.

On paper what your suggesting may well sound possible but in the real world there are many factors to consider, still a worthwile upgrade though.

[bigherb]

not being able to even keep up with lorries and having no power to speak of.

Raising the gearing is not going to help there.

I have never driven the bus over 3500 RPM which is about 60-65

Well which is 3500 @ 60 or 65 it makes a big difference to knowing what box you have fitted.

[CJH]

I don't know the power/torque curve of the DG engine but are you sure it would have enough beans at 3000rpm to pull the van along at 71mph?

Here you go.

[serenitycamper]

I've found this data already using the search option and I understand what these engines were capable of when NEW! My question is simple; is it safe to run the engines at the age they are at 4000 rpm consistently so I can arrive at my destination a little quicker?!!

[serenitycamper]

Well I'm already running on 245 40 18 to keep the rolling diameter as high as I could whilst maintaining the look that I wanted. According to my calculations using an online gear calculator and brickyards data currently my 3000 RPM is 55 mph. After Aidan's fettling (£550) that would increase to 71mph. That's a massive improvement for our setup. In the meantime however, I don't want to blow it to bits!!

I think you'll do well to hit 71mph at 3000rpm with a 1.9dg engine, theoretical gearing calculations are all well and good but you need the motor to do it.

I swapped my 1.9 for a 2.1 and run 215/60x16" tyres which gives a slightly overall increase in gearing, Aiden also built me a gearbox with longer 4th and my van now sits at a GPS 70mph pulling around 3600, prior to the changes it would be revving at 4000.

On paper what your suggesting may well sound possible but in the real world there are many factors to consider, still a worthwile upgrade though.

Did Aidan change your final drive too? Seems very high with a longer 4th and that's only 5 mph more than we're getting at 3500 with a standard box and oversize tyres. Oh and it's GPS speed not indicated speed.

I would be after longer 3rd 4th and final to increase the overall length but not muck up the gaps between the gear ratios.

[Ralf85]

Talk to or pm Aidan for advice!

[serenitycamper]

Will do! Thanks

[California Dreamin]

Serenitycamper....there is an old saying 'You don't get owt for nowt' and I think it applies very aptly to this conversation.
Taller gearing 'WITHOUT' more power is pointless as you will find yourself 'playing tunes' with the engine, shifting up and down at the slightest head wind or incline.
You will also use more throttle to maintain the same speed (because of the decrease in torque from a longer final drive ratio) so your fuel consumption will likely be worse.
Higher gearing only ever works in conjunction with an increase in engine power, ie; going scooby or TDI
As for revs...and this is my opinion....the green band on the rev counter was very carefully worked out by VW and represents the maximum sustained revs for reliability and reasonable fuel consumption. Anything beyond the green band is working the engine too hard, with consequences such as: shortened engine life, high fuel and oil consumption, excessive noise and vibration....diminishing returns! just not worth the extra speed! simple as.

Martin

[shepster]

Well I'm already running on 245 40 18 to keep the rolling diameter as high as I could whilst maintaining the look that I wanted. According to my calculations using an online gear calculator and brickyards data currently my 3000 RPM is 55 mph. After Aidan's fettling (£550) that would increase to 71mph. That's a massive improvement for our setup. In the meantime however, I don't want to blow it to bits!!

I think you'll do well to hit 71mph at 3000rpm with a 1.9dg engine, theoretical gearing calculations are all well and good but you need the motor to do it.

I swapped my 1.9 for a 2.1 and run 215/60x16" tyres which gives a slightly overall increase in gearing, Aiden also built me a gearbox with longer 4th and my van now sits at a GPS 70mph pulling around 3600, prior to the changes it would be revving at 4000.

On paper what your suggesting may well sound possible but in the real world there are many factors to consider, still a worthwile upgrade though.

Did Aidan change your final drive too? Seems very high with a longer 4th and that's only 5 mph more than we're getting at 3500 with a standard box and oversize tyres. Oh and it's GPS speed not indicated speed.

I would be after longer 3rd 4th and final to increase the overall length but not muck up the gaps between the gear ratios.

Firstly, as suggested you need to speak to Aiden for exact ratio's available but as far as I'm aware having a 5 speed 'box, which I assume you have as you mention 3rd,4th and final, makes very little difference as the final gearing on 4 speed and 5 speeds are almost identical.

Secondly, does your van do 60 or 65 at 3500 revs because you can't seem to make your mind up, this may sound picky but if it does 60 then the difference is 10mph for 100revs more which is a worthwhile increase whereas if you are only gaining 5mph for the same revs then perhaps you already have a highish geared'box, again Aiden is the man to ask.

Thirdly, like my tyres you have only gained around 10mm overall which to be fair is only really the difference between a new tyre with 8mm of tread and a bald one so not really going to make that much difference to overall gearing.

Is it a higher cruising speed you are after or just looking to lower the revs for economy, with my old DG engine and gearbox i would sit at 4000rpm on the motorway but the van seems a lot happier at 3500 to 3700.

Also what is your van? fully laden hightop camper, poptop or empty panelvan? all these factors will have a bearing on whether you would be able to pull the revs when in top anyway.

[serenitycamper]

I see, so there's bad news everywhere with simply stretching the gears

It's 65MPH @ 3500RPM in its currently configuration. 4000RPM is about 75MPH but it's theoretical, I've never pushed it that hard.

It's a Dehler high top camper.

From another post

'The tacho on our DJ has a solid green area between 2k & 4k, then hatched green to 4400. The hatched red area starts at 5200 to 5400, then solid red.