Bigger Injectors = Better Mileage?

[1001100]

I saw an auction on Ebay ( http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=170030883906&fromMakeTrack=true ) (or at http://www.TDTUNING.COM ) that was selling larger injectors, .21, for a non-PD TDI. The listing claimed that at higher speeds larger injectors actually got BETTER mileage! I could use this on my 160 mile daily commute, but everything that I know about Gasoline engines tells me this is B.S. Is this true for Diesel?

 

[GoFaster]

The claim is true if the injectors are of good quality (more below), but please consider the source of your new injectors very carefully, because injectors are extremely critical to the way your engine operates, and you need good quality nozzles, not cheap knock-offs.

With a diesel engine, thermal efficiency is best if combustion happens as close as possible to top-dead-center. If you could jam all the fuel into the cylinder in one short shot, that would give best efficiency. Extending it over a longer duration extends the burn later into the power stroke, turning more of the fuel into heat and less into power. So, you need big injectors and a short injector duration to move towards this ideal.

Crappy spray patterns from inadequately machined holes or worn needles due to improper hardening and surface treatment will, of course, turn that extra fuel into smoke rather than power. Once again, be careful about where those injector nozzles are coming from.

Another source: www.kermatdi.com

I will defer discussion about the source that you originally listed to others ...

 

[1001100]

OK. So basically, in a TDI, Bigger IS Better. I think I have found the perfect car....

 

[wjdell]

Go Faster - after my warrenty is up if I was to have a injector go bad and I was to replace what would be the smartest play - I need no power increase but would want the best part that would give me good milage and insure good engine operation.

 

[Lightflyer1]

I am looking at these if I ever need replacements:

http://www.kermatdi.com/servlet/-strse-15/PD100-STAGE-1-INJECTORS/Detail

I don't know if any other adjustments will need to be made though to use them.

 

[Fortuna Wolf]

Is that an automatic or manual?
Start by going only one size nozzle up otherwise you'll smoke badly without IQ adjustments (and chipping) and your mileage improvements will go out the tail.

If its an auto pick up some used manual nozzles. I have a spare set that I cleaned in an ultrasonic cleaner (and their spray pattern is good).

If its a manual start with some Sprint or PP 502s.

 

[wjdell]

I am looking at these if I ever need replacements:

http://www.kermatdi.com/servlet/-strse-15/PD100-STAGE-1-INJECTORS/Detail

I don't know if any other adjustments will need to be made though to use them.

what are the main causes of injector failure

dirt - fuel type etc

450 I hope mine never fail. Is the reason for the CAT filter - Power Service

 

[Fortuna Wolf]

A cat filter and power service should keep the injectors good for a while. The nozzle will still need cleaning of course. I would diesel purge it regularly before you notice any symptoms of clogged nozzles in an attempt to extend the nozzle life before you need to pull them.
If you notice an uneven idle, any sort of irregular jump when its at idle with everything off in neutral...

 

[Mike_M]

OK. So basically, in a TDI, Bigger IS Better. I think I have found the perfect car....

Up to a certain point, yes. If there's not enough air to burn the fuel, you'll get smoke and lower MPG. That means you need more boost.

And as was already stated, that's with good quality nozzles. I know that KERMA nozzles are good quality, made by Bosio. I don't know who makes the nozzles you listed from eBay, but if they're real cheap, chances are they might be cheap Chinese knockoffs (which can be stamped to say anything, including "Bosch", which they aren't).

Mike

 

[wanders]

I would hasten to add that if you like the added power from bigger injectors, you'll be tempted to nail it with a consequent mileage drop. Still if you set the cruise, you won't see a difference.

It hasn't dropped my mileage cruising, but I do LOVE the power!

 

[Fortuna Wolf]

The automatic to manual nozzle swap didn't increase my smoke at all (probably because I thoroughly cleaned the nozzles when I reinstalled them giving better fuel misting), but the power! Better than the Evry mod.

 

[Mike_M]

I would hasten to add that if you like the added power from bigger injectors, you'll be tempted to nail it with a consequent mileage drop. Still if you set the cruise, you won't see a difference.

It hasn't dropped my mileage cruising, but I do LOVE the power!

D'OH! I forgot to mention that effect...yes, if you use the extra power you've gained, you'll lose mileage. It's pretty obvious, but I try to mention it every time. I just forgot.

Mike