Xmt - Sarty's Xsara GTI6 Turbo

[calvinhorse 870]

Yeah but a turbod 1.8 is more like the proper T16 engine ????

[petert 586]

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?)

I'm with you on this. If you buy the 83.50mm forged pistons, it makes perfect sense and gives the most options.

[DrSarty 90 1 Cars]

Nice one Dan...(and Pete now); cat amongst the pigeons or what!

 

Can we quickly compare pros, cons and effort requirements of the current XU7 vs XUD(9) options, and then I'll get onto photos and supporting info for the build? 6 specific questions below I'd love your help on before I finally commit please.

 

1. XU10J4RS head is a definite; it fits either block. I've sourced one, just checking it, but if OK that's £100.
2. I also have Piper vernier cam pulleys (to avoid the evident problems/risk of the OE items). They also save weight and give accurate adjustment. Another £180.
3. Assuming Speno's 83.5mm pistons are stiil available, that'd be another £350 plus £300 on PEC rods. QUESTION 1: Which rod length and crank combo options/recommendations are there that specifically suit those pistons? They give an 8.5:1 CR and 1927cc apparently in an XU9J4 on standard 88mm crank and Mi rods. I am assuming I have a choice of 86mm (XU10) or 88mm (XUD/XU9) crank, so based on mixing these 3 components, how does displacement and more importantly static CR shape up please?
4. Assuming XUD9 is the appropriate starting point (standardly 83mm bore x 88mm stroke), QUESTIONS 2 & 3: Are the blocks all the same regardless of turbo variant or not? And any steer on best donor vehicle, e.g. the dullest, least-ragged candidate? I would guess £50 cost plus £75 on the rebore. (Let's assume the crank costs zero). *XUD9 info here: https://en.wikipedia.org/wiki/PSA_XUD#XUD9*
5. QUESTION 4: Are there any RS head to XUD9 block fitting considerations such as HG to use or headbolts needed? I'll assume £50 for bolts and gaskets.
6. QUESTION 5: With the RS head, would you recommend a complete overhaul and diligent rebuild per Andy's Mi16 thread such as installed spring heights, loads and shimming, valve guides and seats etc? I think it sensible to ring-fence about £250 for a head refresh.
7. QUESTION 6: If I stayed XU7, would you recommend a liners out, new seat seals and fully diligent refit (i.e. protrusion measure and work etc)? If yes, I would assume £200 cost which I've offset in the comparison cost below.

In principle I agree with this suggestion, notwithstanding a £575 price hike. I am a bit concerned about some negative things I've read about some forged pistons; I'm sure it was Wossners, so I'd only consider going this (considerably more expensive) route if:

[A] I was convinced the pistons would be OK

There wasn't too much faffing and cost to accommodate the XUD block.

 

In short, is this change in approach really worth about £600 more in terms of either engine performance and/or build reliability? I appreciate reliability is difficult to put a price on, especially in terms of effort and disappointment when sh1t goes wrong.

 

In performance terms - putting reliability aside for a second - if I assume the XU7 bottom end (regardless of crank used), re-use of the XU7 wet liners and the DFW pistons with Mi rods all works and lasts, is there anything that says the XUD iron block route would be better in terms of available power or torque, e.g. XU7 might only be safe at 250bhp but XUD would achieve the target 300bhp plus? Being negative, am I just spending more money for more weight and peace of mind? I am assuming the head is the limiting factor if anything from a performance POV, so is 300bhp just as achievable via the XU7 alloy block, only with more risk of failure?

 

I don't think I should apologise for this deliberation, and I do appreciate I type a lot. People often type very helpful but short answers, and people like me need to lay out our thought processes and understand the reasoning.

 

So I need convincing about this potential last-minute change.

Edited October 22, 2017 by DrSarty

[petert 586]

Why do you need new rods? I would have thought Mi16 rods would be perfectly adequate given the rpm you'll be using. However, if you need to close & hone the rods and fit new rod bolts, then new rods might be worth considering.

 

You'll definitely need to give the head a full inspection and start from the guides if necessary. The last thing you want is boost leaking past a poorly seating valve.

 

The benefit of the 86mm crank was to help reduce CR. This won't be necessary or desirable with 8.5:1 pistons. Off boost performance will be very lack luster.

 

Buy the pistons and forget about the alloy block & liners. Boring an iron block is cheap and easy. Sealing an iron block is also cheap and easy.

[welshpug 1,657]

xu9 rod would be too short in an iron block if you use an xu9 piston.

[petert 586]

xu9 rod would be too short in an iron block if you use an xu9 piston.

true

[DrSarty 90 1 Cars]

Thanks Pete. Concise as ever.

 

Rods:

Dan proposed new ones for 2 reasons I believe - further reliability and tuning options (read: more power at less risk), plus someone said forged pistons might not easily fit the OE rods without effort/cost. If I assume they/the pistons would need work to fit together, then £300 extra would be needed.

 

Crank:

Understood. If I use DFWs I'll go 86mm; if I use the Wossners it's back to 88mm. I have access to either.

 

Head:

Thought so. I'd like to understand more about the spring height/loading thing that Andy covered on his project. Where could I get a summary of what to do? Perhaps Andy if he's kept info you sent him. I'm confused about it referring to weight/load, i.e. 90lbs as well as use of a dial gauge and shims measured in mm. Probably not that complicated.

 

Block:

I completely appreciate your sensible motivation, but I just need to know answers to Qs 2-4 i.e. XUD9 possible fitment challenges and donor vehicles (e.g. previous turbo or not or doesn't it matter)?

[DrSarty 90 1 Cars]

And thanks again to Mei too. This means Q2 is still valid and I need some help.

 

If we assume I need new (PEC) rods, attached to the Wossners, what rod length on which crank? It was looking 88mm just now, but if I'm replacing the rod does this mean the 86mm is back in the frame?

 

EDIT: I'm guessing, per your comment Pete re 'why new rods', that these SHOULD only be needed if going for silly power and/or silly RPM. The PEC rods talk about 8,500 RPM and 250bhp PER CYLINDER!!! So if we can get the correct rod length needed per Mei's comment, what rods could we use trying to avoid the need for expensive aftermarket (and frankly unnecessary) ones?

Edited October 22, 2017 by DrSarty

[petert 586]

Rod length (88mm Crank) = 235.1 - 37.5 - 44

 

However, I wouldn't buy the rods until I'd done a trial assembly with Mi16 rods and measured the difference. Anything is possible with Wossner pistons.

 

Won't the XU9D block come with an 88mm crank?

Edited October 22, 2017 by petert

[welshpug 1,657]

yep, turbo block will have piston oil spray bars.

[welshpug 1,657]

whats the height of the xu10j4 piston vs the 9j4?

 

might be able to use 10j4 152mm rods, which are bushed.

[DrSarty 90 1 Cars]

Thanks for keeping on this guys. I'm sorry to be a pain, but we're not talking about an insignificant amount of money here.

 

You both have PMs BTW, as a quick voice chat might help me here, especially to not mess Speno about.

 

To recap:

- XUD9 turbo block (to get the piston spray jets) e.g. XUD9 TE, L or Y / XUD9 SD (per the Wiki link above)

- Above bored to 83.5mm (to suit Wossners)

- 88mm crank (comes with the XUD9 block)

- Rod options:

{a} trial fit with Mi rods

{b} trial fit with XU10J4 rods pending 9 vs 10J4 measurements. Questions: if measurements OK in principle, can 10J4RS rods be used? Any other OE rod options?

{c} resort to custom rods

- Aiming for at least 8.5:1 static CR; ideally nearer 9:1

- Questions: Any XUD9 block fitment challenges per Q4 above i.e. will the XU7 or RS sump fit? Is the XUD9 pump usable? Oil or water management? PAS pump? I take it that physical mountings aren't a challenge as it's a standard 205 block.

Edited October 22, 2017 by DrSarty

[DrSarty 90 1 Cars]

In addition to the above, the XU7 has a knock sensor. I have no idea (and doubt) if the XUD9 block has one; do diesel's need knock sensors?

[Andy 105 1 Cars]

Valve spring installed height. Peter guided me through this, and the reasons behind it. Basically, when the valve is installed and closed, each spring should be exerting the same load on the valve as all the others. If using hydraulic lifters, this pre load needs to be higher than with corresponding solid lifters . For the springs I used (PAC s0010) an installed height of 37.0mm gave me a preload of 40kg. Hence, to ensure that installed height, I had to measure each valve with its associated collets and cap and then use shims underneath the spring to ensure that installed height. Tedious job, but that is the point. Building an engine with both precision and accuracy is just that. Not that I am experienced or skilled, but I do have some good teachers ( PeterT and Guy Croft for starters)

Next time I do this, I will measure each one and then get shims made to suit. To my shame, last time I used several thinner shims to get to the correct installed height.

P.s Just sent you my thoughts on your turbo plans .Treat my views in the same way you would with water from a stream......... with caution

Andy

[wicked 103 3 Cars]

To be honest, I think this not the best solution in the end.

 

You are sincerely underestimating the work ($) involved to make the XUD9 work. I see no reason why you should stick to the 83-ish bore (no competition regulations) and why you should overbore (way more expensive that the mentioned $75 imho), just to use some pistons that are for sale. If you would stick to the Mi16, it would have made sense.

Keep in mind that the XUD9 is in more ways different from the XU9; you also need custom engine mount for the XUD9, etc. It not just a iron XU9.

You're also not reusing any of the parts you already have, which was one of you objectives.

 

If you want to go the iron block way (I won't argue that the iron blocks are more robust btw), why not just buy a complete gti6/RS engine and fit new low compression pistons?

What would give the XUD9 with all the custom rods and pistons extra, compared with the almost of the shelf gti6 engine (with low compression pistons), except a bigger drain on you budget?

[DrSarty 90 1 Cars]

Well! Out of discourse, debate, argument, even conflict, in the end comes harmony.

 

I was all set to use what I had, even changing from Mi block and head to sensible alternatives, then the Welsh and Ozzy contingent piped up with obviously sensible (but costly) alternatives.

 

I think it's great BTW. I'm a PM by trade and would call this healthy analysis, info gathering, design, diligence, risk, budget and benefit realisation management. All normal to me and hopefully gets a lot of grey matter churning!

 

Instead of jumping on the justifiable XUD bandwagon, I started asking about catches about this approach such as fitment, even ignoring the cost, which Wicked has indicated would be more than my estimates. In short, it's always a compromise of some sort.

 

Whilst common sense pulls me towards the costly XUD-based solution, I am quite prepared to try the cheaper option first, perhaps at my peril. But if the XU7 attempt goes bang, I won't have lost much bar a head really.

 

I think you can tell where I'm going. This was an interesting and educational design and planning journey with a nice twist, but I have to commit today, and it's likely going to be XU7 TBH. Rightly or wrongly, and as these are 2 very different routes, I'm perhaps going to have to accept the higher risk but considerably lower cost option.

 

My power demands aren't that high. And if I need to revisit this due to XU7 failure I'll have a workable Xsara only needing a heart transplant; all the plumbing and ECU, manifolds etc will already be there....and at least 4 of you can say "we told you so!".

Edited October 22, 2017 by DrSarty

[Andy 105 1 Cars]

Afternoon. Opinionated old git here . You will know from my text that I favour an iron block. Couldn’t care which one really! However, I can see the sense in making the best use of what you already have . I really would urge some forged pistons . Boost equals heat ( well, not quite true as this is a dimensionally incorrect assertion but you know what I mean ) . Use the best flowing head you can ( you are ) , care with the cams and use a really good ecu that is going to support sequential injection, COP, as well as the obvious map, throttle air and water temp, wastegate control and some sort of det. management, and probably a host of other parameters that I have not thought of.

Oh. Valves. You probably are not going to be able to get sodium filled exhaust valves, so the above becomes even more critical .

All this discussion, thinking and planning is excellent fun. Keep it coming!!

Andy

[petert 586]

whats the height of the xu10j4 piston vs the 9j4?

 

might be able to use 10j4 152mm rods, which are bushed.

 

XU9J* - 37.50mm

XU10J4 - 39.1mm

XU9J4 pin - Ø22

XU10J4 pin Ø23

 

Why do you need a custom engine mount for the XU9D block?

 

Sandy uses XU9D blocks for Colin. He might be a wise person to chat with.

[welshpug 1,657]

colins engine is sat bolt upright on custom mounts.

 

drillings on the front of the block are different at the top half, theres a mechanical injection pump bolted on with three m8 bolts, mounting bracket bolts to the side similar to an 8v xu.

[petert 586]

Given that news regarding the engine mount, I've just lost interest in the XUD block.

[Andy 105 1 Cars]

Ditto.( still use iron though).I know Rich. XU7 It will be fine.

[B1ack_Mi16 67]

Why not just put a thick head gasket onto an orginal engine?

 

If you only wanna make 300bhp I would guess that shouldn't really be a problem.

[DrSarty 90 1 Cars]

I find 'only 300bhp' quite funny. Not disrespecting here as I know you know your stuff.

 

Retracing our steps a little, we've had 10 pages of design discussion. I was doing an all Mi (XU9J4) engine, where I could've gone thicker HG. Then it was DFW pistons to lower the CR; not much I grant you, but still could've also used a THG.

 

Then it was just turbo the XU7, but the head untouched probably would've strangled it. I still would've needed a THG, or as with the above it would've ended up a low boost solution.

 

But even low boost on either the above would've resulted in circa 250bhp, which is not to be sniffed at in a sub-1000kg car. My Mazda 6 MPS has got 256bhp, but weighs more.

 

So I suppose I'm saying that in context of turbo tuning possibilities - possibly superchargers too - 300bhp MAY be quite low from a peak figure point of view. But if you'll excuse my French, I'm not a sad c*nt that's only interested in peak/headline figures.

 

And you know I'm not saying you are; but 300bhp I suspect would be not only accessible in the Xsara, but tractable, responsive (due to a higher CR, but 'detrimental' to peak figure chasing) and hopefully reliable too.

 

I'm sure you advocate 300 reliable and accessible horses being 'better' than 400-500 that entail crappy lag and high risk?

 

So I think, following all the discussion and review of options, a relatively low cost and potentially reliable but definitely usable 300 or even 280bhp is a sensible but fun and realistic target. What would I do with on/off 400bhp anyway?

[DrSarty 90 1 Cars]

Apologies for what may have seemed like a rant. Just me rationalising things.

 

So I've ended up with a decent compromise I think, using 90% of the bits I've got, and you're saying 300bhp is quite achievable with that choice. More would be possible via other means, but that's not practical for a variety of reasons at this stage.

 

So thanks is what I mean, and a 300ish target with this plan is what I'll push on with.

 

RS Piper verniers arrived today, so next steps are:

- in-situ loom labelling

- XU7JP4 removal & disassembly ready for rebuild (giving crank & pistons etc to builder)

- remove or replace other bits on the VTS as applicable (exh gone, wishbones & driveshafts refreshed etc)

- get head and prep it for rebuild

- design, build & trial fit exhaust manifold twin-scroll solution & downpipe

- plan intercooler & turbo feed & exit solution

- finish Emerald loom design incl ignition solution, get the bits, make what I need & install ready for engine drop-in

- get engine final assembly & install bits (belts, fluids, headbolts etc)

 

Can't do much else for now. Custom exh from the downpipe back has to wait. Engine builder will supply rings, seals and bearings etc, possibly the cambelt too.

 

Hopefully you'll see some progress, useful docs (like my loom design) and pictures very soon.

 

(Insert smiley)

Edited October 24, 2017 by DrSarty

[Andy 105 1 Cars]

Right. You have a plan. Not heard from Steve yet. I will call him tomorrow if he does not call me. Do you still want the crank or just the head with its associated bits . Feel free to call for a chat if required