Diesel Alternative Engines..... Read before asking questions

for questions and answers about alternative power transplants on the T25, GTi, Porsche,Subaru etc, this is the place. You must register to post but anyone can read.

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Diesel Alternative Engines..... Read before asking questions

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VW are renowned for their diesels and those fitted as standard to the T25 do not do it justice. What can you replace them with to getting better power and economy ?

1.9NA

If you're going from a 1.6 then this will give slightly improved economy and power and increased longevity…. Just not much !

1.9TD

The key engine here is the AAZ " this has been fitted to a wide range of VAG vehicles and is a good solid engine, with a nice fat torque curve. Like the 1.9NA it's possible to use mostly stock T25 fitting kits, you may need to trim the engine mounting bars to make the turbo fit when it's between cylinder 2 & 3. These engines are tough units, but may have done a lot of miles, so make sure there aren't head gasket problems, or worn valve stem seals when buying.

1.9TDI

There are a bewildering array of VW 1.9TDI engines, from 90bhp upwards to 150bhp. Early units are basic electronic TDI, later make even greater use of electronics for smoother running and economy. If you are going electronic be aware that if the donor is 96 onwards you will need to have the ECU from that engine and ignition key, barrel and clocks, or have got the integrated security 'burnt out' of the ECU. Later ones (PD or Pumpe Duse) are said to have changed engine mounting bolt holes that may need new mounts to be fabricated and all TDIs will need a beefier clutch than the standard T25 diesel one.

Who can I get to do the work ?

Known converters include: Russel at Syncronutz, Simon Baxter aka Mr Brickyard and Central VW-Audi on the Wirral

Audi 5Cylinder engines

Yes it's possible, but as with the 5 cylinder petrol it's a lot of Work. Russel at Syncronutz has implemented this conversion, but has since gone 1.9TDI.

PSA diesels " life's complicated enough, there's a wide range of VW engines, but if you MUST here are some words from another member who's recently made this conversion: 'I got a kit from a guy called Phil Thompson 07703844035-cost £230. But fitting isn't that straightforward... You need huge amounts of time and patience to fit, then remove, modify and refit everything about a dozen times to get it right.'
Last edited by Diamond Hell on 03 Nov 2007, 23:00, edited 5 times in total.
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Anonymous

AAZ weakness

Post by Anonymous »

Tom, just to add. The AAZ has a weakness.
The crank pulley bolt comes loose. This holds the timing gear and bottom pulley onto the crankshaft and they have a habbit of coming undone.

They are supposed to be torqued up to 140ftlbs or something like (can't remember off the top of my head) but aren't always done up that tight.

Have a damn good look in this area. If the pulley is wobbling about, its had this problem. If it comes loose, it will shear the key, write off the crank and all the valves will hit the pistons. End of engine!!

MG

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Post by Simon Baxter »

My thoughts on mechanically injected 5 cylinders... waste of time for 100 ish bhp when a 1.9TDi is a much easier swap and more or less bolt together. 5 pot sound nice and are very smooth but unless you go 2.5 tdi I think the amount of work involved in getting one is far outweights it's benefits.
Last edited by Simon Baxter on 09 Nov 2005, 20:19, edited 1 time in total.
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Post by Anonymous »

Simon,
Re- 2.5 TDI and Turbo Diesels.. Russel spent a long time rebuilding a Turbo Diesel 5 Cyl only to find it wasn't worth and put it up for sale very quickly after.
I'm happy with the way my van goes (lots of torque) with the 2.5TDi but gearing is still an issue and I'm looking at rebuilding my syncro transmission just to put in higher 3rd and 4th gears from Long Enterprises.

I think anyone looking at installing a diesel should think about gearing before buying an engine (wish I had now!) as TDi rev limit is around the 4750rpm mark. Much lower than a petrol and you'll notice a difference when on the motorway.

MG

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Post by Russel »

As i have been telling everyone on this forum for a long time, u cant just fitt a TDI without changing the gear ratios in ure gearbox.The TDI's have a lower rev limit than the TD's.The fact that u have more torque also means you want to drop your revs considerably in top gear to save fuel and engine life. Any mechanical mod made to a vehicle has a knock on effct somewhere else.

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Post by Magnum »

Hi Russel,
please can you tell us the posibilities available to get the better gear ratio?
:?:
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Post by Simon Baxter »

Rebuild the gearbox with a higher ratio final drive. This mean buying and installing a new ring and pinion, the replace the pinion is a whole gearbox tear down.
Ring and pinions available from several sources in germany.
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Post by Magnum »

Thanks Simon, I asked this question on the old forum and didn't get a reply apart from the usual "bung a petrol box in" Do you have any more info on the German suppliers? Have just managed to change the diff brgs in a 5 speed box but not sure if I would want to attempt a full overhall yet.
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Anonymous

Gear ratios

Post by Anonymous »

Gear ratios on the T25 came in all different shapes and sizes (or so the saying goes)...

The highest factory box uses a 4.57 Crown and Pinion and a .85 4th gear. With factory 185/14 tyres (thats 185/80/14 if you're wondering), 60mph is at 3053rpm, 70mph is at 3558rpm and 80mph is at 4079rpm... give or take :D

However this wasn't the higest 4th gear as the diesel comes with a lower crown and pinion ratio but a higher 4th gear... 0.78. So by combining the 2, you can end up with 60mph at 2813rpm, 70mph at 3270rpm and 80mph at 3734rpm.

You can buy higher ratio crown and pinion sets and 4th (or 5th) gears (0.70 is the highest) from Long Enterprises and Fast Forward in U.S and Canada but you're starting to approach Porsche figures when changing the crown and pinion.

Just to keep you thinking :)

MG

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Post by Magnum »

Excellent information. At the moment I am running a 3H, 5 speed box and have just put 195 X 14 tyres on the back. The 195s seem to make quite a difference with the slightly larger diameter and revs drop have dropped when cruising.
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Anonymous

Post by Anonymous »

Magnum
Your box has a 4.83 Crown and pinion and a .82 5th gear. With 195/14 tyres.. you're doing 60mph@3045rpm, 70mph@3543, 80mph@4059rpm.

If you want some links for info...

Here are most gearbox ratios
http://volksweb.relitech.com/helmut/GEARBOX.HTM
These are also posted on the club80-90syncro website.


This is where I got my gearbox and tyre calculator from. Its a brilliant site and well worth downloading the calculator... you'll use it again and again!!
http://www.geocities.com/MotorCity/Garage/1811/


MG

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Post by Magnum »

Top stuff MG,

I'm amazed at what difference the 195,s make. Had to put the 185,s back on for a day just to confirm the outcome. It's got to be the cheapest way to improve the gear ratios on a AAZ conversion.....not the coolest but beggars can't be choosers as they say! :idea

Paul
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Post by andylekker »

how much money ( approx ) might it cost to replace a 1,6t diesel engine with something simple and economical. ( diesel again ) ?

thanks,
andrew

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Post by andysimpson »

andylekker wrote:how much money ( approx ) might it cost to replace a 1,6t diesel engine with something simple and economical. ( diesel again ) ?

thanks,
andrew

You won't get more simple unless you get a 1.6 non turbo.

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Post by andylekker »

andysimpson wrote:
andylekker wrote:how much money ( approx ) might it cost to replace a 1,6t diesel engine with something simple and economical. ( diesel again ) ?

thanks,
andrew

You won't get more simple unless you get a 1.6 non turbo.

i meant a simple newer replacement - whatever fits in easily doesnt have to be a 1.6 but a suitable replacement. i read 1.9td deisel are ok in the OP but it doesnt say how much it costs.

just looking for a ballpark figure :)

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