Normal characteristics of 20v JTD? - Alfa Romeo Forum
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(Post Link) post #1 of 5 Old 22-07-11 Thread Starter
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Thumbs Up Normal characteristics of 20v JTD?

Hi guys

I was wondering if anybody could put my mind to rest on a few things. I've got a 20v jtd (156) and after fitting my boost gauge I've observed that on cruising the boost never sits any lower than around 0.4bar...I know it'll never make below 0 as it's a diesel but is it normal for it to always be on boost even with minimum throttle?

The other thing is I've noticed if I'm moving up through the gears with say half throttle there is a noticeable change in boost characteristics at roughly around 2250rpm and at this point there is also a notable difference in the sound of the engine/ abruptly becomes deeper like it's suddenly stepped up if that makes sense?! If anybody has driven a Honda vtec it's like that as the revs hit a certain point and the vtec changes the cam profile....

Probably these things are normal but I'm hoping somebody can confirm theirs does the same. It's been like it since I've had it. There is no loss of power at all and the boost/throttle response seems spot on. I had a rolling road session on it before I touched anything and it came out as 168bhp & 305lb/ft. It seems to boost up to around 1.3bar of pressure in 3rd or 4th gear...

Anyway I'm fairly happy with my first Alfa experience so far! I've got a downpipe back sports exhaust and a ram air maxflow filter on custom pipework from the turbo. I've obviously done the boost gauge and I've blanked the EGR, all in preparation for my remap only problems I've had is a dud thermostat which I promptly changed and having to grind down the entire underneath of the passenger compartment floor as Alfa saw fit to only put paint on a lot of it instead of some kind of underseal so that's all been redone for the future



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156 JTD 2.4 20V

Hi James,

Welcome to the forum and congratulations on your great taste in cars I cannot comment on the boost as I don't have a boost gauage but it all sounds pretty normal to me. They do snarl and make a nice noise as the revs rise. I've not had mine too long either and also spent a day grinding/painting/undersealing with exactly the same problem underneath the passenger side. Maybe the underseal nozzles were blocked that side on the assembly line and no one noticed

Have fun,

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Originally Posted by Alfa.James.2011 View Post
"If anybody has driven a Honda vtec it's like that as the revs hit a certain point and the vtec changes the cam profile...."
Welcome to the forums James.... Interesting comment above, That's simply because Alfa Romeo thought of the idea long before Honda did, thus twinsparks with variators, V6 24v busso's all change profiles... Not sure about the oil burners but knowing Alfa, they would have done something like that to them too.
But then again, it isn't the first time that another manufacturer steals ideas from Alfa!
Just look at Seat Ibiza Mk3 rear ends and tell me it doesn't look like a 156 or even Honda Civics with the "hidden" rear door handles.... Hmmm I wonder wher they got that from too
The 2.4 20v lump is very, very tunable, just be mindful of twisted driveshafts/ CV joints if applying a massive amount of boost
(Post Link) post #4 of 5 Old 23-07-11 Thread Starter
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Keith, I'm sorry you went through the grinding too but I'm kind of glad I wasn't the only one in the end I had to grind back the whole floor pan from front to back! Took me absolutely ages to do it properly. I intend to do under the boot soon too as there are a few nasty orange patches there too

Graham, I'm very mindful of the driveshafts and DMF etc as I don't want any horrible surprises it only really gets a good clear out 5% of the time anyway if you know what I mean

The one thing that is bugging me the past couple of days is my breather filter appears to be puffing some horrible smelling smoke half the time. I don't know if that's normal as that breather pipe used to be plugged into the original rubber intake hose. I'm hoping it's nothing serious as the car is only 53k miles....maybe I just need an oil catch can? I'm very interested to see what the box is behind the inlet manifold as it seems that's where this breather comes from via some sort of one way valve...I'm assuming it's supposed to split the vapour?...don't think it's working if so!
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v6 busso's DON'T have variators in any form.... only the twinsparks and possibly the 2.0 JTS
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