Turbo lag - can it be improved?

Watty · **Posted:** Wed Oct 19, 2005 7:11 am

All CRD owners are aware of the so-called “turbo lag” issue that is experienced during acceleration. My question is very simple. Can the lag period, or seconds waited before the turbo kicks in and give the much wanted compression needed for the required power from the diesel mill, be improved on. Alternative turbo’s, maybe even a second unit, ram/spinned air flow inducers, etc??? Any ideas?

gsbrockman · **Posted:** Wed Oct 19, 2005 3:00 pm

What displacement is your '03..... 2.5L or 2.8L ?
I don't have any complaints with the US version 2.8L w/VGT.
Greg

Ricky5 · **Posted:** Wed Oct 19, 2005 6:36 pm

I dont have any issues with the Turbo response in my '05 either. I've got more issues with the 5 speed auto in mine then anything. Getting that thing to shift like you want it to is a pita. But I guess that is the fun of an automatic.

spoonplugger1 · **Posted:** Wed Oct 19, 2005 9:27 pm

I'm with the guys above, once they changed the EGR valve, which most have been bad since day one, the turbo lag is almost none existent. By the way a turbo doesn't raise compresion, it forces more air into the cylinder so you can burn more fuel cleanly, with more power. Also helps keep the power up in higher elevations.

crdawg · **Joined:** Mon Sep 12, 2005 10:55 pm **Posts:** 98

maybe a module would help,some of the guys on this thread put one on and said it eliminate or reduced their turbolag.thanks Chris

Dutchy · **Posted:** Thu Oct 20, 2005 8:57 am

Had turbolag on my 2002 2.5 CRD but they solved that on newer models, together with better shifting, lowered suspension and rear disks, my 2003 2.5 CRD has no turbolag at all.

oldnavy · **Posted:** Thu Oct 20, 2005 6:36 pm

The type of turbo used now on the CRD (VNT) has been used for years on VW cars and has almost no lag because of the variable vains. The only reason you have much lag on stock CRD will be from the CPU limiting if for EPA reasons. Chips do wonders for these diesels.

These turbo's have one drawback and that's the exposed actuating arm for the turbo variable vains can become corroded and not allow full opening. The cure is to do a WOT at least once or twice between fill-ups. Also the vacuum line operating the rod can become cracked and leak or even break. Most VW diesel heads (I was one till we trade the VW TDI for the CRD) had replace all engine vacuum lines with high temp silicon vacuum lines. I had them on all my vacuum lines on my MB diesel with great sucess.

Biggest problem in the US is poor quality of diesel fuel with cetane levels of 40-42 range, unless you are running the B2, B5, B10 or any mix up to B100 of bio diesel. Most fuels that are running a 2% to 10% or even higher bio diesel mix will usually be 49 to 55 cetane and it will make so much difference in performance and fuel mileage as to be amazing. To switch from the 42 cetane rotgut fuel over to a 50 cetane bio mix fuel would mean the difference in our old '02 VW Jetta of 112 mph topend or 125+ mph topend. On the road fuel mileage would jump from 46 mpg to 50 mpg. Our first tank of rotgut fuel mixed with the factory 50 cetane B5 fuel still brought in 21 mpg, but the engine really quitened down after we fill it up with B10 50+ cetane fuel. My guess is the CRD is going to average about 23 city and 32 highway the way we drive.

kj lad · **Posted:** Fri Oct 21, 2005 4:36 pm

Chipped mine..... NO lag!

Ian

grywlfbg · **Posted:** Fri Oct 21, 2005 5:36 pm

KJ Lad,

Any problems from chipping? I heard that one of the ways they increase power is by increasing injector pressure leading to increased injector wear and failure. Also, any problems w/ the warranty?

oldnavy · **Posted:** Fri Oct 21, 2005 5:48 pm

grywlfbg wrote:

KJ Lad,

Any problems from chipping? I heard that one of the ways they increase power is by increasing injector pressure leading to increased injector wear and failure. Also, any problems w/ the warranty?

I've seen VW's & Dodge PU's driven 100k mile's chipped without a problem and I seen them blow turbo's, clutches, and the whole engine in less then 10k miles. It depends on how they are driven or used/abused in the car. I've never seen the scanners detect a chip, but if the car or truck has way too much power the tech will know. Unless it had a engine failure and is not running. :shock:

kj lad · **Posted:** Sun Oct 23, 2005 2:11 pm

No problems so far

Done about 20K on the chip....... monsterous torque off road :twisted:

Ian

BKH · **Posted:** Sat Nov 12, 2005 6:59 pm

Where do you get the chip? How much? No drop in MPG?

bbo · **Joined:** Fri Sep 30, 2005 5:17 pm **Posts:** 382

I'm with BKH ... specifics on chip please !!!

DaveO · **Joined:** Fri Jan 06, 2006 6:34 am **Posts:** 18

You will find that modern light TD engines are are usually on boost most of the time.

However there are a couple of contributors to your expectattions;
1. diesels are not rev engines - they take time to increase revs (try driving a NA MB300D or other light NA diesel)
2. most exhaust systems are restrictive - fix that and spool up to higher boost levels improves
3. more fuel will improve spool up (but that does not fit with EPA)

As a result the engine is somewhat below its performance potential.

1. fix the exhaust system (2.75"-3" all the way)
2. plugin a diesel tuning module (like the ENG-TEK or similar unit)
3. improve the induction tract (beware of foam type filters - there are lots of turbos with bits of filter behind the compressor)

Katmandu · **Posted:** Sun Jan 22, 2006 5:43 pm

DaveO wrote:

1. fix the exhaust system (2.75"-3" all the way)
2. plugin a diesel tuning module (like the ENG-TEK or similar unit)
3. improve the induction tract (beware of foam type filters - there are lots of turbos with bits of filter behind the compressor)

I'm not sure about the CRDs downpipe (that connects directly to the turbo), but MOST other diesels I know of are VERY RESTRICTIVE.

Simply changing to a LARGER diameter downpipe greatly reduces Turbo Lag.

Just like putting headers on a Gasser!

Just how restrictive is the stock downpipe on these CDRs anyway ??

DaveO · **Joined:** Fri Jan 06, 2006 6:34 am **Posts:** 18

Katmandu wrote:

DaveO wrote:

1. fix the exhaust system (2.75"-3" all the way)
2. plugin a diesel tuning module (like the ENG-TEK or similar unit)
3. improve the induction tract (beware of foam type filters - there are lots of turbos with bits of filter behind the compressor)

I'm not sure about the CRDs downpipe (that connects directly to the turbo), but MOST other diesels I know of are VERY RESTRICTIVE.

Simply changing to a LARGER diameter downpipe greatly reduces Turbo Lag.

Just like putting headers on a Gasser!

Just how restrictive is the stock downpipe on these CDRs anyway ??

Changing to a larger (up to 3" for a hi-perf 3 litre) will improved gas flow. In particular it will increased the pressure difference across the turbo exhaust. This leads to faster gas flow, more spindle rpm, higher boost pressures on the inlet and lower restriction on the exhaust. Thats all good.

The best part is that it has a positive effect on performance, EGT, drivability, and possibly economy (the later depending on your driving style).

Experimentation has shown that 3" is more than adequate, usually 2.75" will achieve VERY close to the same results for a significantly lower cost (parts cost and fitting ease). Fit a straight thru low restriction muffler. the dump pipe makes a considerable difference, and should be included with the exhaust system upgrade. CAT back systems dont address the problem - they leave the most restrictive components in the system.

grywlfbg · **Posted:** Mon Jan 23, 2006 5:13 pm

So being new to diesels I have a newbie question - is it possible to have too large of an exhaust system? I know on gassers, the engine needs some level of backpressure to help exhaust scavenging. Is this not a concern w/ diesels?

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

One of the interesting tests that Turbo Diesel Register ran was upgrading the exhaust to a larger size on the Cummins Dodge truck. They found little improvement or much of an effective EGT reduction, due to the turbo casting restriction and relatively small turbine blade size. How can you tell beforehand whether this will occur? The outlet size on the CRD looks to be 2.5" right at the downpipe connection to the turbo.

Turbo lag - can it be improved?

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