[Renamed:] Exhaust inquiries for diesel engines

**Panzer** · October 10th, 2004 04:45 PM

Sa diesel po ba, mas magada po ba ang fuel efficiency pag yung exhaust pipe malaki compared to maliit? Maraming salamat po.

**Drexx** · October 11th, 2004 01:39 AM

11Oct2004 (UTC +8)

Short answer? Yes, with turbo-diesels.

**Doc Diesel** · October 12th, 2004 05:17 AM

No.....

fuel efficiency in diesel does not come from big tail pipes. have your fuel injection system in optimized form, clean cold air intake and clean diesel is what it takes.

believe me, we have seen customers doing this but it did not do anything expcept for a bigger pipe of smoke belching.

**Drexx** · October 12th, 2004 06:31 PM

12Oct2004 (UTC +8)

DocDiesel's answer is more general (of which I agree to also), and maybe (just maybe) because the vehicles he saw did not have at least 4" pipes that stem from the turbo *and* 4" mufflers too. Of all the muffler shops that I saw here in Muntinlupa area, they only install measly 2.5" inch pipes, which are typical stock vehicle sizes.

My reasoning is that if you have a larger exhaust system, it will allow your engine to breathe more easily by minimizing the back pressure caused by the turbo, and thus make more power by having more air to inhale, and thus the driver doesn't have to over-rev the vehicle all the time...

..but then again, more power means that the driver will in most probability drive more aggressively, and so throw that earned fuel efficiency away...

**luckytruck** · October 12th, 2004 07:17 PM

guys, hitch ako, how about for the pajero with 4d56 turbo? will an exhaust, straight from the turbo downpipe of 3" be sufficient to have noticeable power gains? especially when coupled with a better drop in filter (finer filter or k&N) and the washer mod?

andy

**Doc Diesel** · October 14th, 2004 09:04 AM

Drexx,
may mga clients kami na 4" pipes naka kabit pero only thing I saw evident was loud revvs...

having bigger tail pipes does not minimize back pressure coming from the turbo since the pressure does not even reach the cat converter if available or not because it is already released through the wastgate which is its primary function. other peeps modify their wastgates but I can't comment on that....

my .02 cents.

**Doc Diesel** · October 14th, 2004 09:07 AM

Originally posted by luckytruck
guys, hitch ako, how about for the pajero with 4d56 turbo? will an exhaust, straight from the turbo downpipe of 3" be sufficient to have noticeable power gains? especially when coupled with a better drop in filter (finer filter or k&N) and the washer mod?

andy

IMHO, you need a bigger turbo...but then you need an upgrade in fuel injection system to match the juice....

**luckytruck** · October 14th, 2004 09:56 AM

thanks Doc, in other words, i'll save my money na lang for other mods (like rims and tires)

Doc, di ko pa napa check in pajero ko sa Betan Davao. They requested two days kasi para mabusisi talaga lahat ng ni-list natin dati., tsaka carbon clean if necessary.

i will be dropping the pajero off sometime in early November na lang, kasi that is when i will have an extra car when my brother goes on vaction.

thanks,

andy

**OTEP** · October 14th, 2004 10:03 AM

Panzer,

That would depend on how restrictive your present exhaust set up is.

On a Pajero, there is still some room for improvement as there are really restrictive kinks in the exhaust system.

A mandrel bent system could help also.

**jim** · October 14th, 2004 10:18 AM

sa jeep ko kasi luma na diesel engine ko i made sure that the injectors are in optimal condition, fuel filters are clean, used a free-flow air intake system, and the exhaust has no restrictions. i get 11-12 kms/liter for a 2.2 engine.

having a big exhaust pipe will only make the sound more macho but there is no or minimal effect in fuel efficiency BUT a restricted exhaust pipe will definitely DECREASE fuel efficiency.........