RPM and turbo etc

[Gripped]

Just wanted to see what RPM your diesel Bongos do on the motorway.

I know it's an auto, but it does rev quite high 2,500rpm = 60mph (ish) I think. Compared to my 6 speed car, which would be doing 80mph+ at 2,500rpm ! As the Bongo has quite a torquey engine, you'd have thought it could pull a higher gear ratio.

No wonder the fuel economy is poor.

Also, the turbo hiss is noticeable most of the time. I guess that beng a small turbo, it is desgined to simply supplement the engine all the time rather than give a noticeable "kick" like other turbo cars.

Just interested in other people's engine dynamics !

[Simon Jones]

You wont get any 'kick' from a Bongo turbo as its running pretty much all the time as you've noted. The gearing on the V6 seems to be slightly higher than the diesel: I seem to recall that 3000 RPM = 69 MPH, but with a petrol, all the power is at the top end. It could definitely do with another gear in there somewhere to bring the revs down a bit.

[scanner]

Just wanted to see what RPM your diesel Bongos do on the motorway.
I know it's an auto, but it does rev quite high 2,500rpm = 60mph (ish) I think. Compared to my 6 speed car, which would be doing 80mph+ at 2,500rpm ! As the Bongo has quite a torquey engine, you'd have thought it could pull a higher gear ratio.
No wonder the fuel economy is poor.

How many "6 speed cars" are the same size, shape and weight as a Bongo?

Anyway - on my 1997 2.5TD it's actually 2700rpm at 70mph which equals just about 26mph per 1000 rpm.

Exactly the same as my previous 1997 "5 speed car" also a turbo diesel and also much smaller, lighter and more aerodynamic than the Bongo.

[scanner]

The gearing on the V6 seems to be slightly higher than the diesel: I seem to recall that 3000 RPM = 69 MPH,

That's 23mph per 1000 rpm - so lower gearing Simon.

[Simon Jones]

It's all relative . It's different anyway.

[Gripped]

Having done a GPS check of my speedo, 70mph is more like 65, so it does rev quite high for the speed.

Point taken about the size and weight, I just feel that the engine could easily pull a higher gear.

[Driver+Passengers]

Nigel Hawes discusses in his factsheet on improving MPG, amongst other things, the effect of putting larger wheels on to increase the rolling circumference, thereby reducing the RPM for a given speed. He quotes a 10% improvement. Note that if you do this, you may have to adjust the speedo so that it's not under-reading (illegal).

membersonly/factsheets/mpg_improvement.pdf

[Gripped]

That is a good idea..... so get hold of some 17 or 18" wheels.... I think the standards are 15" aren't they.

The Bongo under reads more than I expected, so bigger wheels might improve things. Not to mention the pimped up look !

[Driver+Passengers]

That is a good idea..... so get hold of some 17 or 18" wheels.... I think the standards are 15" aren't they.

The Bongo under reads more than I expected, so bigger wheels might improve things. Not to mention the pimped up look !

There are discussions on here regarding larger wheels and the clearance they may or may not have under full lock or max suspension travel. I can't comment on those things, myself.

Edit: It should also lower the road speed at which lock-up occurs, which is another benefit.

[skater]

Smaller tyres will make lock-up happen earlier.

Gearbox thinks ( speedo says ) you're doing 40, actually doing 36 ( for eg ), so lock-up is sooner.
Bigger wheels ( overall diameter, not just rim size ) means 40 ( speedo ) =44 actual ( eg depending on tyre sizes ) ,so won't lock until 44 in this eg.

Mine revs at about 2200 for 60mph, ( 225/70/15 tyres so slightly higher gearing than standard but 60 =60 )
When I had the standard 215/65/15 tyres 60 = 56, so revs @ ( actual ) 60 were higher ( less than 2500 tho' ).

Mine has pretty good kick under 40. At higher speeds it's less obvious but not surprising considering the work required to get a Bongo over 60.

I can't hear my turbo hissing so maybe you have some pipework that needs tightening. There is alot of "air" pipework.

[Driver+Passengers]

Smaller tyres will make lock-up happen earlier.

My mistake.

[The Great Pretender]

Well put Skater, I run the same wheel/tyre configuration as you and find my tin top would happily pull a higher gearing, as on my private road it will exceed the limit by getting on for 30mph and would pull higher gearing without problem.