How to Build a TDI-M with Highest possible MPG in Mind.

[Ziptar]

and So it begins..... FINALLY!!!!
OK a little background...
My longest and best friend ever has decided to give me his 1989 Jetta Carat that he has owned since new. The car is absolutlety perferct, rust free and dent free with a perfect interior. He has worked as a service writer for VW for years and has always had every little detail fixed. In fact he had all the window motors and regulators replaced when he found out a recall was about to end just before the head gasket went 2.5 years ago. Since then it has been sitting in his garage gathering dust as he also has a Golf III GTI and a Golf 2 GTI that he has been modding for SCCA racing, so the jetta has had very little attention since then.

Recently he bought a couple of vintage Vespas that he is going to restore and mod because I guess he has gotten into Vespa Racing which I didn't even know was a "sport "and now wants the Jetta out of the garage so he has space.

It is a reallly nice car and is loaded with power everything, rear disc brakes and is absolutley wonderful condition.

I am working on getting it hauled the 300 or so miles to my house over the next couple months. I will be removing the 8 valve gas Engine and putting in a TD / TDI-M

blah, blah, blah... so anyway.....  Now the questions....

My preference is a TDI as I have had 1Z and AHU powered cars over the last 8 years and the TDI just goes and goes and goes  while it makes nice strong stock power. My current 03 Mk4 AHU wagon just turned 178K miles. My 98 1Z had 187K on it when I traded it in

When the car is done it will be used to make my 180 mile daily commute to work so what I am after is high MPG and relaibility / longevity.

What should I be looking to do with that in mind?

Intercooling is a big plus for MPG as well as Power.. yes??

In the U.S. the stock 90hp TDI 5-speed has 0.184mm injector orifices and a 10mm pump and, the 90hp TDI with automatic transmission has  0.158mm injector orifices and an 11mm pump. From what I have read this was done for emissions reasons but, since smaller orifices under higher pressure equals finer spray pattern for a better better burn and less smoke doesn't that also equate to the same power using less fuel?? or is it just the same amount of fuel?

In other words would an 11mm pump and 0.158mm nozzles coupled to 5-speed make for higher MPG at the same HP or just a dog slow low power combination with the same MPG?

What should I be looking to use turbo wise, power is nice but, I am not looking for more than stock as stock is plenty for highway crusing. In order to get the most life out of the engine and best MPG should I have a low pressure?, a smaller turbo?, or VNT??

Or.... Do I not fool with the TDI-M at all and get an AAZ, intercool it and turn it up a bit and be done???

Thanks for reading all of that and any advice input is very very welcomed.

[RabbitJockey]

make sure you sell that carat motor, they're probably the most desirable counter flow 8v with highcompression, i drove a rabbit that had one swapped in, it was a race car with a roll cage and stuff, and that thing ***ing ripped, really fun.

[Justin]

for mileage go with a mechanical TDI. the combustion is more efficient. not sure about the plunger head and injector recomendations. the biggest thing is going to be getting your timing down to a science. I have heard guys on hear say 60mpg with m-tdi's

I should have mine running this week and results in a few weeks

later
Justin

[GoFaster]

Counter to some people's intuitions, BIG injectors will let the engine be more efficient (although it's only by a few percent).

You want to squirt the fuel in there in one shot which is as short as possible so that the fuel burns closer to top-dead-center (as opposed to later in the cycle when the piston is further down).

[RabbitGTDguy]

Counter to some people's intuitions, BIG injectors will let the engine be more efficient (although it's only by a few percent).

You want to squirt the fuel in there in one shot which is as short as possible so that the fuel burns closer to top-dead-center (as opposed to later in the cycle when the piston is further down).

Kerma will say this too when you buy injectors from him and Hillfolk seems to have confirmed this too. Its all about how you like your foot on the pedal. Smaller injectors are ok...but are limited in potential power output. Kerma says himself...with the most popular nozzle PP520's and the PP764's that they won't hurt economy on the highway, around town, etc...if not more than likely improve it.... now, when you put your foot into them...thats where the difference is. The same goes for the much larger R520's as well, which are my upgrade for this winter as I'm only currently running Sprint 216's with the engine setup and pump begging for more. Injection timing as mentioned is more tricky...and finding the balance is nice and it really is kind of a science.  I like the way i have it setup with the MKIV pulley as it takes me if I want and have "preset marks" all of about 5-10minutes to make adjustments if I want. I'd like to laser scribe or etch marks in the pulley as well that show different marks as well so I could just adjust on the fly, whereas now, its do it the old fashioned way with the gauge. Gauge is most accurate though, in the back of the pump. I need to personally bump the breaking pressures up on my injectors as well as install R520's (maybe for xmas here? ) and then I'll really start being happy. Larger nozzles though don't mean poor economy....many see very nice benefits from them.

Just for it being out there I checked my mpg last week when i finally filled the car up and I was getting 57mpg not really digging into it that much...
Just took it in this morning for inspection, passed and is now tucked in the garage again ready for bodywork and paint if its in the equation...but def. the AWIC install which is now even sweeter, the injector upgrades and some other options I've been cooking up Going to compare the NA AAZ intake manifold to the G60 one I did and that as well...anyways...thats for a different thread...a few whore'in pics though...

back from inspection this morning, washed...freezing out but ready to go back inside. Inspection guy said it was nutty to drive to say the least

Yeah...another year...for $10 bucks! No problems

Engine pics....which will look very different come spring even with the bay filling back up a bit more again with the additions...

Joe

[935racer]

Hey Joe what did you do about the downpipe and shift linkage clearance with the turbo sitting like that?

[Turbinepowered]

Counter to some people's intuitions, BIG injectors will let the engine be more efficient (although it's only by a few percent).

You want to squirt the fuel in there in one shot which is as short as possible so that the fuel burns closer to top-dead-center (as opposed to later in the cycle when the piston is further down).

I thought ideal diesel cycle was constant pressure combustion, which would mean a continuous, efficient introduction of heat throughout the entire downward stroke of the piston. Otto cycle is constant volume combustion, burn all your fuel and release all your heat in one rapid burn at ignition and complete the burn before the piston moves again.

[Ziptar]

Thanks for all the replies. So basically it's not so much about the pump and  injector orifice size but, the timing,

BTW: looking Sweet RabbitGTDguy

[Darkness_is_spreading]

Well since you have gone this far, maybe get the rust in check along the strut towers, and body and you'll be set......    

But beautiful install, bet it's a nutty car to drive........

If you have any other Rabbit diesels kickin around give me a shout......

[RabbitGTDguy]

Well since you have gone this far, maybe get the rust in check along the strut towers, and body and you'll be set......    

But beautiful install, bet it's a nutty car to drive........

If you have any other Rabbit diesels kickin around give me a shout......

The rust is not an issue on this rabbit. Its merely surface and doesn't dig into the strut towers...compared to my other car this is SOOO solid, and more solid than any of the rabbits I have had to date. Paint and bodywork was in store for this winter...but I'm not sure if its in the budget. Its  a trade off between this year and next year. Either upgrades this year to the motor further and front core reinforcement....or paint and bodywork this year and the upgrades wait until next. I should update my thread, its old at the bottom of things at the moment I believe.

It is a nut to drive...and thats without where I want it after this winter... but the plan is to restore the car completely with the mTDI there...just is a question of $$$ and when...   trade offs...  grad school costs $$$ as does rent, a wedding, etc...soo....



Thanks for the compliments...

If you need any help or just need someone to bounce ideas off of, etc. Let me know...i'm more than willing to the extent...

Joe