Ease of fitting AAZ/AHU - confused!

[domiles1]

I've been searching, for some time, for a AAZ to go into my '87 T25, and I intend to try to get a whole car so that I can check the engine running and in case any other bits are needed from the car to fit the engine in the van. BUT, there seem to be very few AAZ vehicles around, most of the VWs around seem to be TDi. I understand the post-1996 TDi are a little more complicated to fit (I read the info you need to read before posting) but I feel I might have to go down the TDi route and I am wondering how much more work (for whoever fits it for me) and how much more expense it will be compared with a AAZ. I'm hoping that someone can say " the next easiest engine to fit after the AAZ is......"!!
I keep reading the threads on this forum but most of it goes over my head, I'm afraid.
Also, any info regarding what type and age of cars I should look for would be very welcome.
Thanks
Dom.

[Aidan]

Dom
there's a post here by billynumbers about TDi instal below, he's close to you, he can advise and even do the work I reckon, so pm him...
electronic tdi more wiring but not that difficult really, ideally wants chipping to accomodate being in a heavier vehicle, and any TD or TDi will benefit from chargecooler and oil cooler, enemy no 1 is heat and they produce it locally, though don't seem to strain water cooling system too much esp with air con stat.

[andysimpson]

Dom

electronic tdi more wiring but not that difficult really, ideally wants chipping to accomodate being in a heavier vehicle

Chipping will increase torque/power but will still leave you with an engine which trips over the gearbox, chipping is not the anser sorting a gearbox with correct ratios is the anser, there are no standard or modified t25 gear ratios available that suit an electronic tdi, they are to restricted. Mechanical will give another usable 1000rpm and better economy and no dodgy electrics bodged to fit a t25.
Find an alternative gearbox to t25 box and you will be right

[..lee..]

can any body explain as to why exactly a tdi is so compramised when it comes to revving.

with petrol engines its down to air flow and camshaft features so would a cam change on a tdi give it a bit more rpm its not that difficult to make a petrol engine that was limited to say 6000 rpm rev to 9000rpm " stopping them from blowing to pieces is something else mind "

lee.

[domiles1]

Thanks for all the replies, everyone.
I'm still confused - Andy, what do you mean by "Mechanical will give another usable 1000rpm and better economy and no dodgy electrics bodged to fit a t25". This is due to my lack of technical knowledge on the matter but my question is - mechanical what? What do all the electronics do that can be replaced by a mechanical version? Sorry to be so dim!
Dom.

[andysimpson]

can any body explain as to why exactly a tdi is so compramised when it comes to revving.

with petrol engines its down to air flow and camshaft features so would a cam change on a tdi give it a bit more rpm its not that difficult to make a petrol engine that was limited to say 6000 rpm rev to 9000rpm " stopping them from blowing to pieces is something else mind "

lee.

Its is resricted via electronic governer, short of totally staring again with an ecu map your always going to have power trailing off around 4000rpm, yes they will rev to just over 5000rpm but there is no power, this is done just for emission reasons. With mechanical pump max revs can be set easily and power to 5000rpm is very easy to achieve and upto 7000rpm if you have deep pockets. It does not matter what you do to a electronic tdi you will only ever increase power but never usable rev range due to the way bosch/volkswagen intended it to be with a car with decent gear ratios and not the nasty things we have in vans.

[..lee..]

cheers andy.

[rsxsr]

Hello, My first post. I might be able to shed some light on why the gearing needs to be modified to work with a TDI. In stock trim, max torque on a VW 1.9 TDI is at around 2100 rpm. Max hp at the wheels is around 3800 rpm. You could run one of these TDI's at 3800 rpm, but the economy would be gone and it would buzz you out of the cab. I am in the US, so the conversion may be off. I have a 4.14 Ring and Pinion with a .77 4th. I am also on some taller tires on 16 inch rims. I can now run 70mph and maintain between 2800 and 2900 rpm. I see 30 plus mpg. For maximum acceleration through the gears, you'd like your rpm drop so that you are on your max torque after each shift or 2100 rpm. Chipping, nozzels, pumps etc, can increase the torque/hp and move the numbers up the rpm curve, but at some cost.