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DrSarty

Xmt - Sarty's Xsara GTI6 Turbo

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DrSarty

Thanks Pete and Mei. DFZ was another typo; well spotted.

 

4 liners per Mei's link are about £155 delivered. If I can find a decent Mi crank (as mine are all rusted) for a decent price, then I can stick to the current plan.

 

So offers from the forum for cranks please, or I may consider a pattern, even billet one; but with the latter I suspect cost starts to shoot up.

 

Or, silly question perhaps, could the XU7 crank be used in the Mi block?

 

Otherwise it still seems more sense to do an XU7 b/e complete, plus RS head, with some proper CR solution. What are the GTI6 (RS) forced induction boys doing for their CR - custom piston? Surely they can't be running 10.8:1?

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DrSarty

Plus I've just noticed Pete's second post. Are there any other 88mm crank options which means I could stay with the XU7 block?

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petert

Any 1.9L 205 crank would do. However, surely you guys have plenty of 1.9L turbo diesels laying around at wreckers?

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wicked

I think the forced induction gti6 guys use decompression plates.

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welshpug

not the ones I've seen, restrictor rings and run half a bar from Rotrex superchargers for around 250 bhp, or cheap forged pistons and around 8.5-1 and 1 bar. for circa 350 bhp, or turbos and lots more power.

 

 

any XU9 or DW10 or XUD9 crank will fit the xu7 block, yes the XU7 crank will go in the XU9 block to.

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welshpug

Any 1.9L 205 crank would do. However, surely you guys have plenty of 1.9L turbo diesels laying around at wreckers?

 

not so many these days but plenty or the DW10's which are the same part number.

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wicked

Speno has some low compression pistons for sale on the forum. Could be an option if you could find someone to bore your liners to 83.50 or order custom westwood liners.

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Kane

Given you've got Mi parts in abundance would it not be worth having a couple of drains drilled and tapped on the rear of the head to help with the potential oil control issues? Should be relatively cheap to do in comparison to solid lifters etc and it will allow you to have a fairly decent head out of the box and all the associated parts (cams pulleys etc.) At zero expense.

 

Interested to watch how things progress as I would like to put together an Mi turbo myself. Keep the updates coming

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Andy

Hi. I have access to a good Xu9D crank that I was going to use in an Mi16 build for a friend, but he decided to go with the standard Mi16 crank rather than the diesel, so I am sure it is for sale if you need one . Not sure about the cost, but I could ask him. It is sitting in my garage so I have access, I can photograph it and it has been machined slightly so that the webs clear the alloy block

Andy

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DrSarty

Thanks Andy; thanks everyone.

 

The temptation to buy shiny new stuff is huge, eg Speno's pistons, and each option has pay-offs and drawbacks. I'm keen to hear which option seems to make the most sense. I'm being quite cautious and consultative about this as I want it to work with minimal outlay and to last.

 

My current approach is to stay basically Mi, ie not use a J4R or RS head, as it seems to present CR problems that have costly solutions. I also have 95% of the bits needed. The inherent oil issues relating to the Mi head and/or block combo I'll have to live with, but as Pete says, they'd only really be relevant if I was tracking the Xsara.

 

These should be the final questions:

 

▪ Can I use the XU7 block complete with liners, but with Mi rods & DFW pistons on an XUD9 crank (via Andy)? === ~9.7:1 CR / crank cost only

 

▪ If yes to the above, would it be prudent to use new liners (my XU7 has 76k miles on it) & do I use the XU9J4 or XU7 variant? === as above plus £155

 

▪ If no, Mi block / XUD9 crank / DFW pistons / Mi rods / New liners === as above (drawback is that block is older & needs mod for windage tray)

 

▪ (Costly option but may have benefits) XU7 or Mi block / XUD9 crank / XU7, Mi or new liners BUT bored to 83.5mm / Speno's pistons === 8.5:1 CR / >1905cc? / up to £500

 

Money isn't the driving factor here, but I am looking for value. Does the forged Wossner 83.5mm piston option deliver any benefits due to the lower CR? If no, and the 9.7 CR isn't a drawback/has its own benefits, then it seems to be unnecessary cost. That said, I'm leaning towards the bottom option. I'd like to stick with the XU7 block if possible, changing crank and rods, choosing the best piston option.

 

Thanks for your opinions in advance.

 

@Andy: I'll text you about the crank.

Edited by DrSarty

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welshpug

xu9 into xu7 block works fine yes.

 

liners are probably fine if not rusty.

 

you'll lose the oil filling point if yiu fit an mi16 head.

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DrSarty

And I suppose, if I splurged on the pistons, the R or RS heads are back in the mix, but cost goes up again to circa £600+.

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DrSarty

Good point Mei but only a plumbing inconvenience.

 

Is there really a benefit of the full cash outlay, i.e. Speno's pistons, new over-bored liners (as mine are rusted), plus the diesel crank, all shoved into the XU7 block with an RS head on top?

 

Ultimately what does 8.5:1 give me with an RS head that 9.7:1 doesn't?

 

I'm assuming bandwidth for more boost and an oil filler.

 

Nearly there folks, honest.

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wicked

Maybe some points to consider;

- XU7 doesn't have oil jets under the pistons (ifaik)

- Aftermarket liners (goetze stuff) are not as rigid as the OEM ones. I would not build a turbo lump with Goetze liners. They are ok and value for money for most engines, but for highly tuned ones I would take OEM or Westwood liners($). Search for boosted XU9's and count the number of cracked liners. I know it also comes down to proper mapping, but still.... You want to build the engine only once.

- Aftermarket forged pistons do not always fit OEM rods properly. I have clue about the ones that Speno offers. Which rods will you use? OEM or forged?

- In the end it is about dynamic CR, not static CR. If you're a tad high with static CR, you can lower it with a long duration inlet cam or retard the inlet.

 

It is wise to be strict on budget; you'll have a lot of unforeseen costs later on. A lot...

I've been working on a similar build and I think the bare engine on it's own is not even half the cost of the whole project.

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wicked

Is there really a benefit of the full cash outlay, i.e. Speno's pistons, new over-bored liners (as mine are rusted), plus the diesel crank, all shoved into the XU7 block with an RS head on top?

 

My bet in your case would be;

 

XU7 bottom end, DFW pistons and rods, 86mm XU10 crank, RS head. CR about 1:9.22. (Check the valve cut outs! Maybe PeterT can comment if this will work out)

Or with XU9J4 head; 1:8.93

 

The XU10 crank does not fit in the XU9J4 bottom end without modification, because it will hit the oil jets under the pistons. But afaik the XU7 bottom end doesn't have them and it MIGHT be a drop in..

XU9 crank feeds the 4 big ends with oil via 2 main bearings; the XU10 crank feeds the big ends via 4 main bearings. (Search forum; I've posted the details some years ago)

Edited by wicked

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DrSarty

I have to thank Wicked here for some excellent info, and even more options, specifically adding an XU10 (or similar 86mm crank) into the equation.

 

The rising cost warning I noted a while back; I know it's going to get expensive. I'm guessing it's a balance of spending now and avoiding 'bang' later, or being very clever on the design and spend in the first place which avoids bang. As you can see, I'm in the latter camp.

 

So if someone can confirm the XU10 crank fit proposal in the XU7 block, in conjunction with the Mi rods fitting it, plus whether the DFW piston cut-outs would be OK with an RS head I can make a final decision. Can someone also confirm if the XU7 has a baffled sump and windage tray please? I'm sure it was mentioned earlier.

 

Basically I'm going to use the XU7 liners and not buy the forged pistons, meaning it's just a question of crank choice, as I have to get a crank anyway. I am assuming that the XU7 is a good block (being the basis for some high power engines), despite it not having oil spray jets. If people say the jets are of real benefit, then I guess I revert to the XU9 block and crank solution. My gut feeling is that the XU7 doesn't need the jets, and in conjunction with the XU10 crank not only helps with oil supply but provides a CR drop.

 

If anyone has a convincing argument for staying with a static CR of 9.7:1 they should say. The Astra VXR as an example I believe is about 8.8:1, with not too many engines being near 10:1; they all seem to be 9.5:1 or lower, and there must be a reason for this. What I'm concerned about - but perhaps shouldn't be - is that 9.7:1 may limit the value of bolting the turbo on, i.e. I never get much out of it. However, if the higher CR gives better idle, economy, more tractable power etc and sees a less stressed engine, then it's still worth considering.

 

Decision by tonight I promise.

 

EDIT: This article is quite good re static vs dynamic/effective CR (as people keep mentioning). It seems to hint that 9 or 8.5:1 is the best road car compromise, which is perhaps why the VXR as an example is 8.8. This leans me towards XU10 crank into XU7 block, DFW pistons and rods with the Mi head. This only costs me the crank (£), no oil jets and no head oil filler, but gives me just under 9:1 SCR which looks like a good start point.

http://www.xcceleration.com/cr-boost%20101.htm

Edited by DrSarty

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welshpug

xu7 does have oil jets, they squirt through the rods.

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welshpug

as for compression ratio plenty have been running just over half a bar through gti6 engines at 10.8-1 without issues for a few years now, so not sure why you would want to forgo some low down power off boost by lowering the compression.

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welshpug

no windage tray in an xu7, easy enough to fit one, does have a baffled sump.

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DrSarty

As you're on a roll Mei....XU10 crank into XU7 block?

 

RS head needing DFW cut-out mods?

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welshpug

never tried one Rich but I cant see why not, i have an xud9te crank in an xu7 block and we know they also go in the xu10 block.

 

xud11 92mm crank does fit but not quite turn all the way round, a little fettling somewhere would sort that.

 

dfw cutouts are huge for a standard piston, though i havent checked radial clearance to see how close they are, RS inlets are larger, R valves are the same diameter as Mi16.

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petert

If you run an 86mm crank the pistons will be 1mm down the bore, thus they'll be plenty of valve to piston clearance.

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DrSarty

Thanks all.

 

In which case then, whilst I love the Mi and all it stands for, I am leaning towards an RS head because (in conjunction with other things too) it practically eliminates the potential oil issue, and gives an easy oil filler/simpler plumbing solution.

 

On the XU7 block with XU10 crank (assuming it fits, which looks likely), plus DFW pistons and Mi rods in the XU7 liners, I'd apparently have 9.22:1 static CR which seems a good compromise.

 

This does mean - if I commit, which means not hearing any screams about keeping the Mi today - I have several Mi bits to get rid of, and am in need of an XU10J4RS (GTI6 / VTS) head. I don't even need cams, lifters or covers as I'm sure I have these already. Perhaps I can swap some Mi heads, cams and blocks etc with someone, or find another way to buy in what I need and sell what I don't...to fund this madness!!!! :wacko::blink::huh:

Edited by DrSarty

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wicked

I chose for the Mi16 head, for the love of the 'daddy 16v', but reasoned with the brain, the reasons mentioned would make the RS the best choice.

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dcc

Cant help but think a xud block would be better for your needs, easy to overbore to 83.5mm for those pistons, no worry of a crap liner ruining fun, yes its a bit heavier, but peace of mind... I'd also bet it takes more boost. Slap on a RS head (double valve springs as standard), a set of cheap rods (i.e. pec at £300?) And you have a very cheap engine which will take a fair amount of boost, at the cost of only a bit of weight? (Circa 10kg?)

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