Unblocking a HDi exhaust NOW WITH Video!

citroenxm · Post by **citroenxm** » 23 Jun 2011, 08:16

Cut the cat out with a grinder and find a tube that will fit into each end of the echaust pipe and weld it up..

Online auto motive used to do de-cat ones... we have a local exhaust specialist who can get which ever you want..

Paul

Deanxm · Post by **Deanxm** » 23 Jun 2011, 08:22

I think on petrols they actualy release about 1 or 2 bhp, ive seen lots of stuff on the net showing cars being rolling roaded before and after removal, the gains were minimal.
Certainly on my XM removing the cat made it slightly more gruff but there was no power increase you would ever notice.

What i did notice was the 1mpg extra that was possible with it gone, but it didnt make any difference when driven around town, only on motorway stuff.

D

citroenxm · Post by **citroenxm** » 23 Jun 2011, 10:06

Well, Ive been told on the 24v PRV in the XM S1, with 3 cats, removing them releases 5bhp each..

Paul

Deanxm · Post by **Deanxm** » 23 Jun 2011, 12:24

Not sure if you would get 15bhp out of all of them but i would imagine it would make more of a difference to a multivalve engine such as the 24v PRV rather than its 12v counterpart or my 8v unit.

I have looked into tuning nasp engines and its a very interesting subject indeed, increasing air flow in the exhaust may lower torque at certain revs but increase peak bhp and the key is not overall airflow anyway, its mixing the fuel and air fully in the cylinder, really worth looking at properly if your sad like me

when you read proper articles by people who know what they are talking about regards air flow the science of the combustion chamber you can understand why induction kits and porting more often than not are responsible for power loss at some point or accross the whole rev range.

D

citroenxm · Post by **citroenxm** » 23 Jun 2011, 12:38

To be honest Dean, the PRV 24v is that eager and goes so well its far far good enough for me!

Id be interested in the power to weight ratio, or the BHp/ton readings..

Id not wantmore, shes got pleanty enough for me as she is.. and makes me smile every time I go out in her..

Paul

Deanxm · Post by **Deanxm** » 23 Jun 2011, 12:43

I bet she does go well Paul

Would be great to get one on a rolling road wouldnt it, see how many horses it has lost over the years and what it performs like on toadays fuels/oils, i even onder if anyone has had one tested when it was new to see how many pony's it REALLY left the factory with in the first place.

D

citroenxm · Post by **citroenxm** » 23 Jun 2011, 12:44

I doubt shes lost many, previous owner changed the oil every 3k!! The oil was still golden! NOT Saying she hasnt lost any either..

Ive not done enough miles in her.. but we have an oil leak to attend to now on the sump.. so that will get a change then.

Paul

Deanxm · Post by **Deanxm** » 23 Jun 2011, 13:11

Did you watch topgear where they tested the power of their 5 grand super cars

http://www.topgear.com/uk/videos/budget-supercars2 about halfway through the vid, really worth a watch if you have not seen it.

D

Citroening · Post by **Citroening** » 23 Jun 2011, 13:17

Out of interest what's the BHP and Torque of the 24v's - the 12v's are about 170BHP, so must be getting to 200ish surely.

Deanxm · Post by **Deanxm** » 23 Jun 2011, 13:52

200bhp exactly i think

D

citroenxm · Post by **citroenxm** » 23 Jun 2011, 15:07

Figures...

Ok.. 200bhp straight 200bhp.. (With 3 Cats)
Top end, well somewhere around the 150mph mark.. Prooved too by myself and a fellow owner

0-60mph, well, testers claimed 7.5 seconds, and its is something like that, well 60 in second gear I know that much, and she will pull strongly right up to the 6300 or so red line!

They ARE some serious motor. Remember though, this is an un modified or tuned unit.

I beleve the S2 CX Turbo 2 motors were officially 200bhp too, though official figures were never released and Turbo 1 figures were always used at 168bhp. I can beleve this if the S1 Turbo was 168bhp, then the CX T2 must have been more. Im not sure of S2 performance figures though.

Paul

Deanxm · Post by **Deanxm** » 23 Jun 2011, 15:15

Ive been looking about for PRV specs after your post on cxm and i found some torque and power graphs for the prv, this is the turbocharged 12v though and they seem to follow outputs of similar volume 4 cyl engines but the graphs go to 8000rpm and all the power shows between 5k and 8k

must be race engines surely.

Also found some info relating to the 24v heads being transplanted on to the low compression blocks and twin turbocharged race tuned for 650bhp, now that would put a smile on your face Paul

D

Citroening · Post by **Citroening** » 23 Jun 2011, 15:31

Interesting Paul.

The figures for the CX GTi Turbo and CX GTi Turbo 2 were exactly the same but that just doesn't stack up! I believe that Citroen kept the figures the same due to some French law - or something along those lines!

Differences included an intercooler, T1 used higher comp pistons (they changed to avoid risk of detonation in the later cars with the more efficiently intercooled turbo), T1 had a lower ratio gearbox and smaller CC Fuel Injectors are used in the Turbo 2. The GTi Turbo 1s have a low ratio gearbox, so will affect the top speed slightly but by no means are the GTi Turbo 1s a slow car though...in their day, Dad used to have 'burn-ups' along the motorways and dual carriageways with Merc 190 Cosworths and came off best.

Each GTi Turbo is completely different from another and they each have their own personality. I'd say that 200BHP would be optimistic and they'd be circa 180. Saying that though, I do know of a very sprightly car that measured over 190 on a dyno!

As you probably know, a Maikonics Kit (if you can find one!) boosts them up to 250BHP and they're a completely different animal - 320FT/LB torque too.

The 24v figures are impressive though being standard!

citroenxm · Post by **citroenxm** » 23 Jun 2011, 19:23

Right FUN OVER BACK ON TOPIC.....

I removed the HDi exhaust pipe tonight, and started the engine... The turbo spooled up, I could hear it out the manifold, and when I revved the car the boost came right up!! and so did the revs...

So blocked the pipe is!!

Next to find a pipe to replace it with, Ive a feeling Ive got one in the shed at the farm....

Paul

DickieG · Post by **DickieG** » 23 Jun 2011, 20:05

citroenxm wrote:Right FUN OVER BACK ON TOPIC.....

Oi we'll have no more of that nonsense, remember where you are