BXProject

[Bx Bandit]

I know there has been some criticism of the design of the 2.1 TD head, but why? Furthermore, wouldn't fitting one to a 1.7TD improve things, mostly higher end oomph?

[Vanny]

oh no my son, 12 valves do not automagically make things better! There are plenty of petrol 24v engines of various makes which don't put out as much as the valver, number of valves don't mean much if everything else isn't right.

To my knowledge it isn't possible to fit a 12v head to a 8v block, i expect water channels etc don't line up. The 12v isn't just a 1.7/1.9 head modified its a whole different engine top and bottom, and its slow and lethargic. Having driven an XM with one in many years ago it just didn't want to go, that point when you know the car is a turbo came and went with little commotion, it was dull and just didn't pull like a proper XUD.

[Bx Bandit]

From what little I've read, there can be detrimental effect at low revs, but otherwise then there is an advantage. Having said that, I think the info was mostly based on petrol n/a's and I know not of relevance to diesel T's......however, the 12v (or 16v on later engines) must be beneficial otherwise manufacturers wouldn't do them! So I was just thinking and being curious about the whole affair!

[Vanny]

basically, more valves = potentially bigger opening (in or out).

Bigger cylinder inlet/output potentially means bigger air intake and exhaust.

More air potentially means moe power.

BUT you can make your intake and outlet to/from the cylinder as big as you want. If there is a huge back pressure thent he exhaust gas can't get out, and equally if you have a shite intake manifold the air can't get in. All you then do is choke the thing either because the exhaust doesnt have the time to clear or because your trying to suck litres of air through a straw. The 12v was a nice try but not really up to it. And as for 16v (and i assume your talking diesel here) then thats a whole different kettle of fish as it is HDi.

[docchevron132]

Well, the D12 head will fit on a 1. block, but the valves wont open unless you scollop the top of the bores, so it's all a tad pointless.

Also, everything Vanny said. The D12 is a pretty good engine when set up right, but I really do believe the D12 would have been a good deal better with a well flowed 8V head, which is what I always intended to build, and never got around to.

[Bx Bandit]

Hmmm, scolloping the top off the bores sounds tedious - could I do it with a hacksaw?

Yes Van I did mean 16v diesels and I hadn't thought of the HDi factor. I understand what you mean about letting the thing breathe...I'm guessing there is more to be gained from letting the engine breathe better than from fitting the xud11 head. But do both and there must be even better gains. The xud11 has a cat whereas the xud7 doesn't so that's improvement again.

The xud11 has bags more torque than the xud7 and although the pump/injector setup/increased engine size is the larger part of that, the head must be part of it too.

I'm not after huge gains btw, just bits here and there that are simple but noticeable. The bosch pump will mave a mahoosive difference but I like to think out loud my thoughts on these things. It would probably be more work than it's worth but the 'argument' is would it have a +ve impact above and beyond what can be done with an 8v head?

[Vanny]

erm, two things, first, since when (and on what planet) does a cat help performance? They are simply a legal requirement and not of any benefit to fuel economy and performance.

secondly, your not after huge gains, fine, but what are you trying to gain? You can have more BHP, more torque or better fuel economy, but you can't have all three! I would like to suggest that a correctly setup 1.x XUD with garret turbo tuned up a little, bosch fuel pump setup correctly an well fettled injectors would give you 110bhp+ and anything upto 70mpg with bags of torque if required. The 1.x XUD is a remarkable piece of work and i don't personally believe that the 1.7 XUDTe can be improved other than correctsetup and blue printing. That crazy Stefan guy used to get 170bhp out of his 1.7 (for all of a couple of hundred miles before it went pop) and i doubt very much that you could get that from a 2.1.

If you want to put an XUD11 in then you have to do it because you like the engineerin challenge or you like the way it normally drives. You can't do it because you want the engine to be better because it just wont work out like that!

[Philhod]

Happy New Year Guys ...I`m back home again....by the skin of my teeth, but more of that later.

I was wondering when you would get round to mentioning a Garret, coz there is a newer one, with either an Asymetric type vane or a variable vane fitted....the latter is quite a bit dearer.
These new types actually do give you more BHP, Torque and MPG.
Weather you are running petrol or diesel a 4 branch exhaust manifold and an extended ( in length) and again 4 branch a la XUD, inlet manifold, both suitably improve things no end.

Err.. Train was late into Gothenburg by 1/2 an hour, so I only had 1 and a half hours to get to the airport....Go to bus station... airport bus in.... get on book to Landvetter airport...last on, stood near driver... as we turn onto motorway I say youv`e gone the wrong way....he says Oh I`m going to City airport first you really should have got the next one, what times your flight
I say 5-20, he says oh dear............. get to city airport... go to cab rank,
now 4-25.. ask driver can he get me to Landvetter for 5.. he sayscan do 600 kronor please (£50) I say goooooooo!!!!! We get ther 3mins past but just manage to get on flight....phew!!!

[Vanny]

Asymetric, phooey, what you really want is an electronically controlled variably adjustable gate (VAG) type garret turbo, you can make it a big turbo or a little turbo electronically meaning you can have zero spin up time at all revs! Second hand i've seen them for about £3000! But my how lovely that would be.

[Vanny]

actually, can a diesel be super charged?

[Bx Bandit]

What I meant by the cat is that there is one on the 2.1 but there isn't (and nor would I fit one) on the 1.7. So, whatever advantages a 12v head may bring to a 1.7 will be further improved by the lack of a cat. (I think I either didn't word it properly 1st time or you misinterpreted what I said (I'll go for the latter...... ))

What am I trying to gain?
-130 bhp tops but I'll settle for somewhere between 110 and 130.
-Much increased torque from as low down in the rev range as possible - this is my only real criticism of the engine (or as you say it's set up) The bosch pump should go along way to helping this.
-Better mid range performance to enable more relaxed m/way cruising, esp with regard to reduced engine noise by using taller gears (1.9td g/box maybe????)
As far as economy goes, so long as I get above the 40s then again I'm happy.

I'm trying to achieve the better performance by better setup which is what you are saying Vanny, as opposed to just winding up the wick on the turbo and go guns a blazing. A faster spooling turbo would be lovely, although the cost will no doubt be prohibitive.

So, assuming I achieve the above (Bosch pump/tweaked fuelling/tweaked turbo/better breathing (fore and after) and better intercooling (if needed)) then a logical progression (to my little brain at least ) is to consider other options which improve engine efficiency to gain performance. Hence my 'what if an xud11 head was fitted to an xud7 question'

So, exactly why wont performance improve with the 12v head? I know low rpm performance may suffer (which is counter to what I'm in part trying to achieve but the bosch pump may well prove sufficient to my needs there.) That leaves the need for higher rpm performance than can be helped by a 12v head...??????? (Or not....? )

Well Done Phil, back in old blighty now then mate! How was all the snow?

[Vanny]

Yes a 12v might give benefits, but this one wont, its shit. The porting is poor, its overly complex for no apparent reason and the airflow is much worse than a 1.x. It would be interesting to bench flow the two and see if all the speculation i'm providing is correct, but if your going to stick a 12v head on, then you might as well just fit a really small air filter and plenum and suck through that to achieve a similar effect.

If you want to have a decent go at a perfromance diesel then you would be better starting from the 1.6 HDi and work from there, infact why not fit that? Tax wont go up any which is nice!

[docchevron132]

Running 130BHP on a 1.7 is right on the very edge of what you can get away with before the head implodes, and a D12 head wont really be any different.
I agree with Vanny here, The d12 head really doesn't breathe very well, for a 12 valve it's piss poor.
Not all d12 engined cars have cats ya know, and equally, the performance effects of a cat are lessened ona diesel anyway.

Without doubt you'll want to bin the standard intercooler for anything over about 110BHP as it really cannot cope and the performance just dies off as the air entering the engine gets superheated.
You can actually feel the performance fall away.

In essence, I think the best setup you can hope for using a 1.7TD as a starting point is fitting an N/A cam, that gives more torque off boost.
As will the Bosch pump properly set up.
A Garrett T2 (Or T3 if you can find one!) that has the wastegate suitably tweaked to provide more boost lower down, and a good deal more boost at higher speeds.
Spending some time on the porting, and making up a better exhaust manifold will help, as will an inlet manifold capable of moving more air.

Either way, you dont really want to run a 1.7TD at RPM's above 5100 anyway.

[Philhod]

Doc likes to live on the edge. I wouldn`t take one past 5000

Yes that`s the one I meant doc, the wastegate alters and also the angle of the vanes so that you get max blow at all revs. As a much lower price alternative, the asymetric one has vanes that change angle at the end giving more blow low down and the increase surface area gives more push at high revs.
I made an excellent cooler for one of these, some years back. Same size as the air to air one fitted.
Welded up an aluminum box with attachment lugs in the same place. before welding on the top, I fitted 3, 22mm copper tubes inside joined together with 180 degree yorkshire fittings. The air entry and exits in the same place and where the copper came out, a ally tube welded on, big enuff to allow a rubber pipe to tightly fit between the 2, finished off with jubilee clips, once the top was on, filled with water. We modified it with an air intake on the bonnet but I didn`t think it was necessary.
Never found out the increase in BHP, but I would have thought it would have ended up around 125.
The other changes have already been pointed out 19 na cam, (which Bandit has cos I gave it him)
A 4 branch Ex manifold and an extended inlet ( by about 3"") coupled to a plenum under the cooler
It all worked surprisingly well, for a one off.
I didn`t make the ex manifold, by the way, some bloke in Bolton was making them up with all attachments for the turbo.

[Bx Bandit]

Hmmmmmmmmmmmmmmmmmm Well I don't want a car that's 'on the edge' so I guess 110 is a safe aim. So, my technical girlies, I'll stick to a standard head then.....(if you so insist like..... )......When you say ported Doc you mean smoothed/remove rough casting lines etc?
As regards improving the exhaust manifold, I'm not familiar enough to make a judgement!
The inlet manifold from a 1.9TD with 1.9 td i/c & ducting would be better......? and even moving the airbox to where the fuel filter sits would be beneficial.........?
What's the advantage of a T2 or T3 turbo then Doc? I'm guessing there's sufficient boost in the standard turbo (T1...?) but does the T2/T3 spool up quicker then?

Thanks for tolerating my ignorance chaps!!!!

1.6 Hdi is not a bad idea Vanny.......

[David]

The inlet manifold from a 1.9TD with 1.9 td i/c & ducting would be better......? and even moving the airbox to where the fuel filter sits would be beneficial.........?

There's no difference between the piping, intercooler and inlet manifold on a 1.9TD or a 1.7TD engine. The only differences are mechanical mountings.

TBH, the best things you could do "on the cheap" would be to wallop a 1.9 (or even a 1.7 if you can get it) N/A cam in the head, up the boost a bit and wind the fuelling up appropriately. That will give you much improved mid-range torque, and a little bit more power too (possibly 95-100hp)

Anything more than that starts costing money.

[Philhod]

16 HDI is an excellent idea as it`s just about the best all round unit today. and fitted in Cit/ Pug/ Fraud/ Volvo. Mini (well it will be shortly)

Don`t forget it breathes the other way round, with the exhaust (and Turbo) right at the front. Ive looked at this problem. The solution in a BX is to split the exhaust after the turbo and run down each side.

The 19 td wasn`t around when we did the TD mods Bandit

[Bx Bandit]

Dave, doesn't the 1.9 have the intercooler at the front by the rad? Isn't that better intercooling? Or is it at the expense of a more convoluted routing?

Phil, so that was a water: air intercooler? Doesn't air (even at 30 deg C) have a better effect than coolant at 90 deg C ?

[Vanny]

Dave is talking about a 405 top mount 1.9TD, as your well aware bandit your talking about a Xantia setup, the BX never had a FMIC! Bandit, i have pretty much all of these parts dotted around the north west (including two xantia intercoolers i think) inclusive of the bosch pump, injectors, intake and exhaust manifolds, but you'll have to be quick, much of this stuff is attached to an engine awaiting the scrap man (including a money spent immaculate 1.9td cylinder head)!

[Bx Bandit]

Bolx I just bought a Xantia i/c.........but it was only a pound and my dad collected it for me! Fuck, well.....yes please mate. How much do you want mate and by when do I need to haul my ass oop norf?