Tuning Pointless?

Guru Meditation · Unread post by **Guru Meditation** » 29 Sep 2003, 21:22

Check this link out http://www.cardomain.com/member_pages/v ... 472&page=2 I was searching for breakers etc when I came across this. This guy has swapped his turbo for a BX 1.7 turbo beacuse "....As U will be able to tell after U read this im not a big fan of spending cash but The Uprated turbo is actually off of a Citroen BX 1.7 Turbo, because it boosts at a higher pressure than the original ZX turbo...." Surely that has to be the most pointless thing ever-I mean both the standard Garrett and KKK units can have the wastegate tweaked to provide more boost than you could ever need?

jeremy · Unread post by **jeremy** » 29 Sep 2003, 21:48

I agree - anyway I'm not sure they do have higher boost, my Haynes manual covering the BX TD and another covering the ZX state they are the same models blowing at the same pressure.
Now where is Portrush?
jeremy

Unread post by **Jon** » 30 Sep 2003, 03:32

Sounds like a load of old cobblers to me.

Unread post by **alan s** » 30 Sep 2003, 03:43

<font face="Comic Sans MS">What was that sound like 'dumph....dumph....dumph' I could hear when he turned his stereo on??</font id="Comic Sans MS">
Methinks that could be a cap assabout mod type site. There was a group of young guys who had a mailing list on modded Cits a couple of years ago and the general tone of conversation there makes it appear as this is either them or something similar.
I suppose they're not doing any harm so long as they don't run into anybody or sell them one of their cars after they've finished disembowelling them!! [:o)][:o)]
Alan S [:D]

Unread post by **Jon** » 30 Sep 2003, 03:52

I was not aware that the Zx Advantage TD was the latest victim of the modifier. Maybe I'll "big up" the old Zx Aura again soon. Maybe not! Its in its years of dotage now.
All ZX Td's banged out a healthy 92BHP from their 1905cc. Now I think about it though, the BX TD managed 90hp from 1769cc.
Perhaps the blokes onto something.
Both run Bosch or Lucas pumps with a KKK or Garrett turbo. Perhaps our old friend the BX really did run some more boost. I fail to see the point in changing the ZX turbo for a BX one though when its easy to crank the boost on both types of Turbo (the Garrett being the best to respond in my "knowledge" of these mods)[:p]
???? [^]

VisaGTi16v · Unread post by **VisaGTi16v** » 30 Sep 2003, 06:11

"the BX TD managed 90hp from 1769cc."
i thought the 1769cc was 60bhp and 75bhp with the turbo whereas that 1905 was 75 and 90 ?

jeremy · Unread post by **jeremy** » 30 Sep 2003, 13:12

1.7 TD is quoted as 88 or 90 BHP and 134 lb ft torque. Performance for TZD Turbo saloon seems to be generally in the region of 10.5 secs 0-60 mph and 11.0 50 - 70 mph. 1.9 RD is about 16.3 secs 0 - 60 on 71 BHP and 50 - 70 mph takes 15.7 secs (What Car 1990) - So you can see that the turbo is of more than marginal benefit especially as there is no apparent fuel consumption penalty.
Jeremy

rossd · Unread post by **rossd** » 30 Sep 2003, 13:54

The 1.7td is 78Bhp without intercooler (eg Pug 205/309) or 88Bhp with an intercooler (Cit BX). The intercooled 1.7 and 1.9 both run the same turbos on the same boost, KKK or Garrett, on approx 0.9 bars at 3000rpm.
This is according to the autodata manual, I have a pdf version for the 1.7td if anybody wants a copy!
Ross

BonceChops · Unread post by **BonceChops** » 01 Oct 2003, 05:17

Maybe his original turbo was knackered - he does not say if it made any difference at all. I have been playing with my fueling and have increased boost pressure from about 12.5psi to about 14.5psi. The waste gate is supposed to be set at 1 bar (14.7 psi). So when you read that you cant just adjust the waste gate on a turbo diesel and get more power it is most definately true. The car feels faster now - quite noticably.

VisaGTi16v · Unread post by **VisaGTi16v** » 01 Oct 2003, 05:49

do none of the 1.9td's like in the zx/306 etc come with intercoolers then? Surely they dont if they only put out 92bhp to the intercooled 1769cc's 88bhp.
I saw in another thread someone mention a tuning company who do a intercooler solution for the 1.9td which takes it up to 135bhp or something stupid. I wonder how difficult it is to do it yourself, fix a 1769cc one on etc? I have no idea how but im sure someone does and has tried it

Unread post by **RichardW** » 01 Oct 2003, 13:03

All TD units fitted to Citroen (cars) are intercooled*. Both the 1769cc (fitted only to the BX) and the 1905cc (Xantia, Xsara, ZX) produce around 90 BHP, with the 1905 unit making slightly more torque - oh and using a shed load more fuel[:(!] It should be easy then to squeeze another 8 horses out of the 1905 unit to get to the same specific power ouput as the 1769. Don't know why PSA made it the same power output (something to do with fitting in with the power bands that all manufacturers seem to stick to I expect!)
RichardW
* There is an exception - the later Xantia 1.9D was badged 1.9SD and used a low blow turbo without an intercooler.

jeremy · Unread post by **jeremy** » 01 Oct 2003, 13:36

I've never seen anything as to the reason for the 1.7 TD - I couldn't believe it when I bought mine, not knowing uch about BX's at the time.
The Turbo engine was introduced around 1988 by which time the Xantia was probably in the planning stage and the ZX certaily was. I expect it was known then that both would be substantially heavier than the BX and it was thought wise to hold something in reserve. Another reason might be that the smaller bores would give a slightly larger gasket face and improved sealing? It is also possible that the smaller blocks were considered more rigid.
Does anyone know if it is possible to bore a 1.7 to 1.9?
jeremy

AndersDK · Unread post by **AndersDK** » 01 Oct 2003, 14:08

Jeremy -
The BX bores are :
1.7 (XUD7xx) : 80.0mm
1.9 (XUD9xx) : 83.0mm
Both engines have the same stroke of 88.0mm.
There are several differences in the cylinder head : cam timing, valve size & clearances - also between n/a & turbo variants same bore.
I've never heard of anyone done a reboring to such engines - but frankly I've no idea.
A re-bore could be surprisingly low-cost - comparing to the cost of shimming a head - I donno.
In a thought engine overhaul/rebuild process, it might be interesting to consider the cost of a possible re-bore, as machinery specialist these days can do just about anything - with incredible accuracy - and fast delivery.

BonceChops · Unread post by **BonceChops** » 01 Oct 2003, 15:29

"Another reason might be that the smaller bores would give a slightly larger gasket face and improved sealing?" --- Jeremy, are you suggesting that the BX runs at a higher boost pressure?

jeremy · Unread post by **jeremy** » 01 Oct 2003, 16:39

No I'm not suggesting the BX runs at a higher boost pressure - as far as I know it runs at about the same. What I am suggesting is that the surface area of the block face (after subtraction of the holes as it were) is greater as the bores are 3mm smaller in diameter.
There are many cases where the larger version of an engine hasn't proved as reliable as a smaller one, usually due to overstressing of some component. My suggestion here is that turbo diesels for the public were relatively new and this one was a pioneering engine. Therefore what precautions were taken to try and avoid problems, and was the use of the smaller block one of them?
Anders - the possibility of overboring would obviously depend on the thickness of the cylinder walls. It may be the the castings are the same and just bored to different dimensions or they may be different in which case overboring would weaken it too much. Checking spare part nos would be useless unless Citroen supplied unmachined castings which I think unlikely.
I think the 1.9 turbo heads may be thicker and of a different design to reduce cracking for which the 1.7's seem prone. As there is no combustion chamber this wouldn't cause a problem. I agree that the 1.9 TD valve timing is different - but so are later 1.9's as in Zx rather than BX so I suspect this is for some other reason - like emmissions but doesn't materially affect output.
Fortunately mine doesn't seem to need re-boring at the moment so there's no way I will part with the money! - probably smash the transmission as well! (maybe not - but I was brought up on overstressed British transmissions looking for any excuse to fail)
jeremy