Quote:
Originally Posted by dremd
Mkiv VW's have a bit of factory ram air.
Bigger turbo would only move BSFC curve up, the motor spends most of its time at low- moderate load and 1400-1900 rpm's. Would be fun, but most of the time that I make a boost request, I only want it for 3-7 seconds and a VNT-17 would make me need to downshift (maybe 2x) for the power I normally want.
I do have significantly larger turbo inlet piping (improved spool, tad bit less smoke at WOT). My TIP is from PD150, air box snorkel/ ram air bits are from Euro Dual Clutch R-32.
As far as boost side plumbing, I'm running a stock turbo outlet hose->1.8t pancake pipe (reduces spool a tad with larger volume, but reduces charge temps epically at cruise and allows a tad more high rpm power)-> Ebay stock size, but much higher mass and nicer fined inter cooler-> water / methanol injection (mostly to keep intake clean of EGR geww, but also quiets motor a bit at high power, drastically improves HP when heat soaked, and a tad more high RPM power with not much down side other than using crappy washer fluid up at 1.5x my normal rate) -> 99.5 upper charge pipe which relocates map much nearer intake and after the water/ methanol injection so I can keep a bit more timing from the corectly sensed intake air temp-> PD150 intake manifold (I've never run one before, but everyone loves them and my stocker was sheared off in the wreck.
My buddy runs a 3" straight pipe on his ALH, I'm not 100% sure, but we think he lost a mile or 2 to the gallon with it. Sounds pretty epic, reasonably quiet at idle/ cruise, not terrible at WOT, but sounds like a big single 2jzgte doing 100-150 pulls (except it is actually 30-60 pulls).
This car is for super comfortable highway cruising, so I'm running stock sized exaust with diesel Cat-> glass pack resonator -> factory giant 1.8t muffler. I'm expecting factory noise level, but hoping for lower.
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I run my diesel at lower speeds too, 1,200 to 1,600 RPM, its always making some boost above 45mph.
I have experemented with water methanol injection also, its pretty nice.
My W/M system is not installed but I plan to reinstall it this summer.
The thing with diesels on turbos is a lot of the factories seem to have put undersized turbos on them. The OEMs seem to favor smaller turbos because they are cheap, they spool quickly and they like them for the fact that they are small.
A good example of wrong sized turbos is what they used on GM diesels back in the 90s. When you check fuel economy numbers for the last year of the N/A diesel and the first year turbo there is almost no difference.
I picked up over 2mpg when I added a much larger than stock turbo, using 100% non factory parts for everything else.
The problem is the factory turbo on the old GM diesels were too restrictive on the exhaust side.
I went with a turbo that would be more efficient at my normal driving engine speed. It seems to have worked out pretty good.
If you look of your turbo specs and cross that with engine air consumption at certian given speeds you may find the two don't go together very well where you want them to.
I don't see how a free flowing exhaust would hurt a turbo diesel.
Also have you tested an EGR delete?
EGR delete seems to always help trucks get better milage, but cars don't always benifet. I think some cars have a problem getting up to staying at operating temperature with out EGR.