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Discussion Starter · #1 ·
My 2.4 JTD is remapped, very very nicely thank you, but as a petrolhead i am somewhat used to a more hands-on approach, and doing a bit myself!

i would normally start with things like breathing better, air in gas out stuff, basic things like that to begin with.

now, air induction aside for a mo, i would normally go custom exhaust route with my petrol stuff, and with my inbuilt hatred of all things catalytic, that particular piece of political pipework would be the first thing to be eurotrashed!

however, this is pretty new territory for me, tuning diesels i mean, and after a quick study of the stock pipework i'm left with a small quandry...

should i

A - decat (sports-cat), and keep a reasonably baffled rear silencer.

B - keep the stock cat for back (negative) pressure, free up the rear section and silencer as much as possible

C - sports cat and free flowing unrestrictive rear section and silencer.

i have no idea how this sort of modern diesel will respond in either power gains or losses or noise levels in and out of the car, so some assistance and experiences please?????

thanks in advance

shrew
 

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rip out the cat you dont need back pressure with a td
it doesnt really matter what you do with the exhaust it wont get loud
 

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Mine has been de-catted, with powerflow stainless steel exhaust.
Not really that loud at normal driving speeds, but a nice 'roar' when you drive it properly:p
 

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From what I gather you don't need the cat on the diesel to pass m.o.t's and by replacing the cat you'll gain some power, the most noticeable improvement is the reduction in lag. I plan to do this to my 1.9jtdm.

A FMIC will provide good gains too, there's a few threads in the tuning lounge about the intercooler set up.
 
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Discussion Starter · #5 ·
yeah, ive got to go steady though.

the mapping has taken me to the limit of the stock clutch's capabilities (330ftlb) so ive got a CG Motorsport item already to go in, so i don't mind a couple more perks but much more and it will be the gearbox next (360ftlb) which i don't want to get into!

good to hear as i suspected that it won't get too loud with some free flow pipework, and i'd do a sportscat rather than straight pipe de-cat, so at least it looks real!

i think fmic would be great but a tad too much for my target, so more air in and easier to get out, and if it spools quicker too it'll be as far as i want to go i think.

brakes had better be next i suspect, 5 minutes of spirited braking can have them fading like a Tony Hart watercolour!

thanks for the advice and comments so far, keep them coming though, theres life in the topic yet!

cheers

shrew
 

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if you replace the cat with straight pipe instead of a sports cat the money you save you could spend on induction or intercooler
 

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Must say that 330mm discs and Brembo 4-pot calipers are great! No fading what so ever! And I only have a 1.9, but with traction on all 4...

On my old 155 2,5 TD I hade 2,5" pipes and only one silencer at the rear. Not loud at all. The turbo takes most of the noice away. You will get a better respons/spool up with a more free flowing system. The system on my 156 Q4 is starting to rust away, so I'm concidering a new system in a year or so. I will remove at least one of the three silnencers.
 

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The cat is not an issue, but the bore of the cat are the real problem as much smaller than the rest of the exhaust originally of 55mm.

I fitted a universal diesel sport cat 55mm bore and welding a 60mm SS pipe to fill the length difference. then supersprint 60mm all the way ... :thumbs:
 

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I've got a stainless steel exhaust on my JTD 20v. I kept the diameter the same but went for a free flowing back box and de-cat (but silenced to look like a cat!). The most important bit of the exhaust is to make it free flowing and if anything wider at the Turbo end. Where the gases are hotter as they come out of the engine, they are larger particles(due to their expansion) and by the time they get to the cat area, the temperature has significantly decreased by a few hundred degrees apparently and the exhaust doesn’t need to be any wider from the cat on, just free flowing. If you de-cat the main cat and also the pre-cat (right next to the turbo), you will get a few more bhp, but more torque lower down. The turbo should spin more freely as the gases can escape quicker and come in slightly earlier too 200rpm or so, maybe more. There was a noticeable improvement at lower rev’s around 2-2500rpm but a slight dip in acceleration immediately after the de-cat at around 3-3500rpm, the rev’s sort of hang then carry on again, not sure why that is though.

If it were me and you’re purely trying to make it faster in a straight line (as there are also braking and suspension to consider) improved induction, front mount intercooler and exhaust are good things to consider, then another re-map. Something like a BMC CDA for induction or a GSR intake could be considered, both are around the £150 mark. Front mount intercooler’s can be fitted but it’ll cost you a fair bit of money. For approximately every 10 degrees you decrease the intake temps you will improve in power and torque by approximately 4% power & torque. It’s best to look at single pass though(intake and exit at either end) as they perform better.

As mentioned before though, you’ll be on the nearing limits of the gearbox and things will wear out quicker due to the extra stress on the engine, gearbox, driveshafts etc. Might also be worth improving the handling & brakes unless you’ve already done those.

Cheers,

Mark
 

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I would be inclined to tweak the map, lower the torque or certainly limit it by the torque limiters in the map, then you can concentrate on extra torque higher up the rev range resulting in extra power.

Was the 330lb/ft at the wheels? (measured on a rolling road?)

FMIC on its own will add only a little power, but will allow extra tweaks in the map. Good £ for lb.

GSR intake is the best £ for lb increase in spool up.

Removing the butterfly restriction is worth doing.

fitting a 3bar map sensor is good too.

You can get 215bhp without touching the exhaust, then your looking at a bigger turbo, then the exhaust is really worth doing and you should be around 250bhp from an old 10valve at this point.


Just seen its an angel map, so I doubt you have proof of the power its kicking out, I would get it measured on a rolling road first to see what its doing before touching anything else.
 
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Discussion Starter · #12 ·
hi guys

thanks for all the great info, it all sounds very very tempting to get the credit card out and go get some ponies!

however, this is supposed to be my miss's car and the everyday run around, so at some point she will get a say in what happens.

probably should have started the thread with this included, but i didn't expect to get as far as fmic and borderline bigger turbo's!

i can consider this thread well and truly answered thank you all, so my plan will be as follows...

a straight through decat silencer, and a free flow rear section, maybe even just a piped tip depending on how volume levels when i try it de-cat'd but no rear box on!

probably match it up with a free'er flow filter element first, a'la K&N or similar, suggestions welcome on suppliers and versions, but i'm not going to spend £100 plus on full induction systems for now.

finally, i'll have angeltune relook at things once done just to check ticketyboo'ness!

i can have a final check and map done by angel on a rolling road i know of, but you're right it was a static uploaded map to begin with, but i tell you what, its bloody good!

and so is my 2.5 cdti movano, finally a van that kicks sprinters ar5es!!!

as i said at the start, this will likely be a custom build from my regular guys for pipework, with maybe a few purchased parts to help the build price and speed, but it should be nice.

if i can i'll get some photos and maybe a you tube clip of it all put together and see what you all think at the end, but this will likelt be two to three weeks away, so if you want to subscribe to the thread i'll post a quick note when ive got something to shout about.

thanks again guys, diamonds as usual...

cheers

shrew
 

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Damn - and I was trying so hard not to want to even think of modding my 2.4 JTD 156 until I stumbled across this post lol!

Good info there!
 

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have a chat with 'cph' before you waste your money on k&n or other brands, he will tell you the real dyno proven bhp benifits of induction.
In fact, its best to run past him your ideas anyhow, as he will tell you (dyno proven) £ for lb where your money should be spent - unless your dead set on exhaust and power is not an issue?
 
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Discussion Starter · #15 ·
Hi Jason

thanks for the recomendation,who or what is "cph"?

i don't mind spending the money on induction, but i am trying not to get into the realms of gearbox breaking torque!

in fact (Attention Gordy!) the remap alone is a stunning tune for the money, and massively improved a car that was already marvellous, but....

as i started the thread, i'm a petrolhead, and used to doing such things, as much for personalisation as outroght power increases, its just nice to be a little different aswell as knowing the guy next to you at the lights is going to get the shock of his life if it tries it on!

I was under the car the other day with my exhaust guy initially because i need a rear silnecer hanger seeing to. Whilst under there i noticed how simple the exhaust on these oil cooker 's is, mine has just the cylindrical catalyst up front, tubed back to just a rear silencer box, thats it.

so a thorough inspection of what was good and not so, i thought sod it, i'll rip the boxes out the thing so long as it doesn't end up too loud and the miss's complain!

my fears on diesels becoming too noisy with little silencing are now quashed, all good there then, and i was only really in the area of a better air flow in just to make a little more of free'ing up the catalyst anyway.

i'm happy as pig in muck truth be known with outright power, and don't drive this car very hard anyway as it is the daily runabout and i have other toys to abuse when i'm feeling leary, but i do want to personalise it a little, hear it growl a bit to match the already infectious induction noise, and just a tad more power would be greatly appreciated but not essential.

more importantly, with my comparitively miniscule experience of tuning or modding diesels, i wanted to make sure i wasn't going to lose any power or torque for the sake of an exhaust growl, but that fear is well and truly quashed too now thanks lads!

shrew
 

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cph is petes user name, he is the brains behind the GSR kit, but been in the motor industry for the best part of 30years and really knows his stuff in most areas.

I am also against dyno-queen torque figures, they do nothing for top end power and just knacker the box and clutch, even though my old bus is on target for 225-240bhp, I have the torque limited to 290lb/ft at the wheels.

Good luck, you will see Pete 'GSR' loitering around the induction threads.
 
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