Petrol Turbo?

Way2go · Post by **Way2go** » Thu Sep 14, 2006 3:07 pm

Seeing the great work Kitch is doing on his engine rebuild and the swaps others have done made me wonder the following:

1) Is it possible to fit the turbo off the diesel onto the 1905 petrol engine?

2) If so, what boost could be expected on the GTi 8v and the GTi 16v?

Anyone with experience of this, or opinions please.

cavmad · Post by **cavmad** » Thu Sep 14, 2006 3:12 pm

Way2go I asked a similar question a while ago now, I think there`s issues with engine internals not being up to the extra pressure applied.

Toddman · Post by **Toddman** » Thu Sep 14, 2006 3:17 pm

Easy option is to go for the CT from a Xantia or 406.

In theory ypu can turbo the 8v or 16v lumps but you have to consider the engineering involved, mounting the turbo is trick on the 16v and of course you would have to use an ecu with the relevant inputs - thus making the CT and its loom etc a realistic option.

Oh and yes you could use a turbo from a diesel but again it is the mounting of it that is the tricky part.

There re plenty of topics about this mod on the 16v forums.

Cheers
Luke

Toddman · Post by **Toddman** » Thu Sep 14, 2006 3:21 pm

cavmad wrote:Way2go I asked a similar question a while ago now, I think there`s issues with engine internals not being up to the extra pressure applied.

The 16v bottom end is more than capable of handling the increased pressure and the 8v is not exactly weak and I am lead to beleive that the D turbo bottom end is based on the 8v GTi bottom end anyway.

If you are worried just use the 16v bottom end with the 8v head.

Cheers
Luke

jeremy · Post by **jeremy** » Thu Sep 14, 2006 4:19 pm

The diesel cranks are different from the petrol cranks in that the crankpins are 5 mm bigger - and there may be clearance issues on the main bearings.

There is an enormous number of differences between a n/a and a turbo diesel - strengthened connecting rods, stronger pistons with an iron guide for the top ring, oil jets to lubricate the pistons, huge oil pump (shared with 16valve) to name a few. This just gives some indication of the work necessary to fit a turbo and make a reliable engine.

The 16 valve in fact has a performance better than many of its turbo contemporaries and was designed as such - without the drawback of turbo lag.

Best to use a known turbo engine and have the benefit of someone elses mistakes and development budget.

Xantia/XM CT engine may be suitable but a BX hasn't much room under the bonnet - as is apparent from the GTi's Turbo-diesels and 16 valves - and somehow I think it was designed without certainly the latter 2 engines in mind.

tim leech · Post by **tim leech** » Thu Sep 14, 2006 4:41 pm

Heres a thought why not convert a 1.9TD into a turbo petrol engine?
The engines themselves are fundamentally similar I think (no doubt if Im wrong you will all tell me)

Gti injection system and a 19TD engine and turbo? is it possible?

Kitch · Post by **Kitch** » Thu Sep 14, 2006 4:45 pm

No because diesel heads are totally different!

Spark plugs? Inlet manifold system? Sensors?

Plus all the common turbo PSA petrol engines use Iron blocks, as do all the diesels. BX petrols use alloy.

tim leech · Post by **tim leech** » Thu Sep 14, 2006 6:48 pm

Will a petrol head not fit a diesel blcok then? Excuse my ignorance!

jeremy · Post by **jeremy** » Thu Sep 14, 2006 7:05 pm

I think petrol heads will fit diesel blocks. Cranks and pistons may be a bit more of a problem as the diesels don't rev over 4600 rpm and I expect the crank counterbalancing may not be appropriate for 7000 rpm and the pistons and rods are probably rather heavy too.

The diesel pistons are basically flat topped with a cutout below the 'comet' discharge point - not correct for a petrol engine.

Have a lok at some of the articles on this link - gives you some idea of what can be done and what the weaknesses are:

http://www.pumaracing.co.uk/

Kitch · Post by **Kitch** » Fri Sep 15, 2006 9:43 am

tim leech wrote:Will a petrol head not fit a diesel blcok then? Excuse my ignorance!

They'd physically bolt together, but whats the advantage? As Jeremy said they're setup to never rev at a high speed. If you want to fit a turbo, the head is where you've got the majority of playing around to be done.

Only issue with std petrol bottom ends is that the pistons might carry too much compression. A common theory if turboing a BX 16v lump is to use the pistons from the DFW engines (with cats) as they are lower compression.

Easiest way to turbo charge a petrol BX and go fast is to plug a 2.0 CT in as used in the Activa and XM. Its a fairly poor engine in standard form, but literally just a boost increase, filter and decat will push 200bhp with a higher figure in torque. Even with the added weight of the engine, which isn't much thats going to make a quick car! It makes an Activa shift and they weigh over 1400kg!
Only issue is the gearing. The Activas use the ML5T gearbox, which is light years ahead of the BE range for smoothness and robustness. But the ratios are pretty much the same as the 2.1 TD, they've very tall. So if you wanted to sprint quickly you'd have to have a fiddle.

Toddman · Post by **Toddman** » Fri Sep 15, 2006 4:38 pm

Yup! as I said earlier the CT is the easiest route.

You can also use the 8v GTi pistons with the mi lump to give a nice comparatively low CR and the TT 205 used the std pistons with a little machined off the crown.

I might still have all the calculations etc that I did when myself and KA were consiering supercharging a BX 16v but it is just so much work when the CT is available.

Cheers
Luke