Understanding Diesels


Torque Junkie
Rexton 270xdi 2005
ive been trying to upgrade my Diesel 2.7L car over the past 2 years but i keep realizing just different it is from Petrol so i would like you guys to help me understand a little ...
1-Compared to Petrol which requires more Air (im asking this because i plan on using bigger intercooler pipes)
2-On big diesels like the Silverado i noticed a massive exhaust does that mean Diesel produces alot more Exhaust gas than petrols with similar engine size ? (im asking because i plan on Using bigger exhaust systems than what i currently have )
3-the guy whos going to build me the aluminum pipes told me that in the past he replaced a stock Downpipe on a Seat Leon Diesel FR , going from 2.5 to 3Inches and there was a drop in performance (can somebody explain to me why ? would a 2.75 have been a better choice or is the stock the ideal even when remapping ?)
4-does all the mentioned above still hold true if i were to add a bigger turbo /injector nozzles ?
5-i read somewhere that diesel takes alot longer to burn and so adding more fuel through bigger injectors isnt going to do much unless you add some additive to the fuel to make it burn faster .. your thoughts on the matter ?
6-Intecoolers is bigger still better in Diesel case or will it cause Lag and weakness at low rpm ?

Thanks in advance (i apologize for my weak English , if something isnt clear ill do my best to try to explain what i mean )
Ermmm thanks i guess :) ... so regarding my post i went today and got a bigger intercooler with 2.5 aluminum pipes .. and ive gotta say the car has become far more responsive .. it feels alot faster .... i do however hear a sound of leaking air when im around 2.5K Rpm ill have to check that out later ..
i tried but i cant seem to produces the same noise when the car is in Neutral , i guess it requires more strain on the engine for noise to come out ... i did however notice some dark oily misty areas near the connector to the Manifold and on the wielding of one of the Intecoolers aluminum pipes , so i fixed and tightened the band on the manifold connector , as for the aluminum pipe , i guess ill have to get some sort of material to seal it around the wielded part or ill head back to the guy who built them for me and see what he can do .
with the one near the manifold fixed , the sound is still there so its not the one causing the "leak" , further more the area in the aluminum pipe with the leak is so tiny i doubt it could produce the sound i hear , when in neutral and revving i cant feel air or see oil spraying from them so its a pretty minor one , theres probably something more ..

something tells me it has something to do with the waste gate because the hissing sound it makes when it leaks is very similar to the sound i get when i Rev to 3k Rpm and let go , is there a case where the waste gate gets jammed or fails to operate properly because of higher air flow than stock ?
If the leak is only at load/revs... its quite feasible you've a boost leak somewhere. Most engine ECU's will have numerous boost maps which are selected in certain conditions. It's quite possible your car doesn't boost much (if at all) at low load in neutral - which annoyingly makes things like this hard to find.
the thing is i dont know what exactly to expect because changes were made to the car and the leak came along with them , if it was in the same state as before the leak id be able to compare times and response but in this case ive installed a different intercooler with different size aluminum pipes and there was a change in their routes ....

Over all any leak should be indicated by the dark oil that escapes the pipes which is a great advantage to diesels and right now its my only way to locate them but i cant shake the feeling that theres no leak issue but something else like back when i had Open pod installed instead of my stock filter/filter box , again around 2.5k Rpm while moving it would make a noise (Different from the current one it sounded like those things they use to water grass , the ones that keep changing directions while spraying water ) , i have a theory but i dont have anything to base it on so tell me what you think about it

my theory is this , in both cases i improved intake (Bigger intercooler/bigger intercooler pipes) while maintaining downpipe/Exhaust at the same size , what if the amount of air going in is too much and is forced back or out of the wastegate/dump valve while on 2.5k rpm ? as to why its not the same case when on higher RPM perhaps its cuz the air fuel ratio evens out at higher rpm and theres less pressure .... this is probably a flawed guess since im not sure how it should go
but im hoping this might lead you to possible case
How should i put this ... ermm well for starters i found a Cracked EGR pipe at the Exhaust side of the engine , the EGR delete on my Rexton is at the intake manifold side so air was still accumulating in the pipe from the Exhaust side and the extra pressure led to a crack in the pipe .. when i physically deleted the EGR from the Exhaust side aswell this time the whistling weakened but it was still there and i thought i didnt solve anything ..
however after a couple of weeks the sound just vanished , now you can only hear it when the engine is cold , like only when i start up the engine , once i Rev up the engine the sound vanishes , meaning it has something to do with the heat in the engine bay .. perhaps some seal that dilates under heat or something ..
im ignoring it currently because its no longer an issue for me since it vanishes a minute after start up , it does however still annoy me that theres a leak somewhere that im unable to locate and fix

oh and thanks for asking xD i was hoping to reply once i solved this issue but i cant consider it solved yet :p

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