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More power for 2.5NA or other tyres?


henk
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I fitted some 2 years ago a completely rebuild 2.5NA in my 88 but driving around this weekend in Marquanterra (FR), it still lacks some power on longer hills.

Marquanterra is sand terrain. Tyres used were Black Star Guyane 235/85 down to 1 bar at the rear and around 1.2 bar at the front.

Is there a way to get more power out of this 2.5NA or should I take other tyres (available are 255 BF Mud, 205 XPC or 305 AT's)?

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I think the 2.5NA only gets around 70BHP. On long hills even my 200TDi (120bhp?) would gradually slow up, topping out at 60mph on a long uphill run was not unusual, while on the flat it would be 70+/- 20mph.

I think sand driving saps the power too.

So... I guess either live with it or consider putting something with a bit more grunt up front.

Over here they sell lots of after market turbo (and intercooler) kits, but the 2.5turbo has a bad reputation of failing, but was without intercooler.

I think Les has a 2.5 turbo with an intercooler fitted, I would expect this to get you a good bit of extra power 10-20bhp? and I think Les reckoned the engine was good to run with the intercooler.

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I wouldnt fit an intercooler to a TD to get more power, i'd fit it to help cool the inlet charge and hope it makes the engine last a little longer.

They really arent strong enough to start hopping up the power.

I'd took to replace the NA with a decent TDi, they're becoming cheap as chips these days.

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88 runs standard diffs but with 2 LSD's. I go up the hill in 2nd low to make as much speed as possible: it is a steep hill !!

As you can hear the engine dies at the end

Here another movie of a first attept of a 110 with 2 ARB's ... he only succeeded in his 3th try

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If the diffs as you say are "Standard" then they are both 4.7:1s ?

These are OK, and there not lower diffs to my knowledge, well rare 4.88:1 series 80s stuff :lol:...

but 2 things

Running 2 x LSDs will increase the 'Bogging' of the engine when they kick in

2nd is the tyres are going to raise the gearing and make the 88 feel 'boggey'

as well, ....the 2 together may be the root cause... with a low BHP / Torque engine

You could maybe look at tuning the engine, wouldn't be a cheap route

a more simple engine transplant to a more powerfull unit could be an easier + cheaper route

The 2.5 is not an engine I have come across as ever being one that tuned, doesn't mean it can't be done

but it may pay to stand back and think of options. Lastly may pay you to shove it on a rolling road and find out

just how much BHP its actually producing - in case there is something wrong with it at the mo ?

Lastly lastly consider going back to the same climb, and change the wheels and tyres to more std units

and see how it then performs - I think its gearing and power combo plus maybe your engine is not

in its 1st flush of youth and producing all it should ??

HTH

Nige

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I'm no expert but I'd definately say there was room for improvement in that engine by the sounds of it :)

Les' old catflap wouldn't have died like that I'm sure. In low 2nd even my old S3 derv 2.25 would plod on reasonably well.

Like Les said sounds like somethings straggling it, have you crushed the exhaust? air intake delaminating inside or something?

Will :)

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@diffs: 4.75 they are

engine: I stripped it completely, bored +0.040, head skimmed, new pistons etc, it runs very nicely

exhaust: collector and downpipe are from the previous 2,25D, this could indeed be reason for not breathing at its maximum

tyres: 235 Black Star Guyane = probably too much profile

Most other hills were taken at first attempt, contrary to some Defs and D1's.

One other steep hill needed 4 attepts after which I smelled the clutch :( , but that was about 2 hours before this one

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Rolling road it :)

Diffs are slighly better than 4.7s all helps to compo for the bigger tyres,

but try Rolling road / close look at Engine and BHP Outputs and tyre size

Frankly 235s are not that big, so engine power output has to be top of the list

of things to check, a 10 mins session on a rolling road will tell you everything you

need to know re engine, its condition, and BHP & Torque outputs :(

Nige

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2-inch bore pipe for a 2.5 N/A. I had a similar problem to you once and it turned out to be the rear silencer. I removed it and the engine was fine straight away. I cut the silencer open and the innards were just a solid lump of rock hard clay.

Les.

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2-inch bore pipe for a 2.5 N/A. I had a similar problem to you once and it turned out to be the rear silencer. I removed it and the engine was fine straight away. I cut the silencer open and the innards were just a solid lump of rock hard clay.

Les.

OK, I'll look at the downpipe and the silencer

Thanks for all comments and advice

Henk

ps: For those that go to Billing: have a beer on the D&G stand

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  • 3 weeks later...
OK, I'll look at the downpipe and the silencer

Thanks for all comments and advice

Henk

ps: For those that go to Billing: have a beer on the D&G stand

Coming week-end I go again to Marquenterre but now I will try it with Michelin 205 XPC tyres rather than the Black Star Guyane 235's.

I also meaured the downpipes of the 2,25D (=45mm) and the one of a 2,5D (=55mm), but this is a change for later the season

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