Author Topic: New (to me) 1991 Jetta ECOdiesel, performance mods, and ideas  (Read 646 times)

May 07, 2020, 12:08:29 am

Johnnyboy707

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So I have some complex questions and maybe an idea or two. Would like to bounce some ideas off you guys.

1. I want to get a 2.5Ē downpipe for my Jetta. Is anyone selling them, or can anyone fab one up that I could buy. I would pay first, of course.

2. Air to water intercooler. Iím going for cheapest to most expensive mods, doing what I can do myself first. This is my first step. Is this going to mess with anything if I put this on before any other mods?

3. Is anyone selling a custom intake manifold? I saw some old links to PassengerPerformance, but it appears the website no longer exists. Anyone have anything like this laying around, or a link I can buy one from?

4. Covered boost temperature and downpipe... turbos now. Is this turbo reliable to produce 150hp? This is the number Iím wanting to get to. I go on pretty long runs with my (stock) MK7 GTI with a couple buddies of mine (Ď19 STI and Ď19 WRX) on the backroads in West Virginia and have no issues keeping up and pulling on them in the turns (im a bit better of a  driver). I want to be able to do the same with my Jetta while keeping the reliability. I will be getting everything for maintenance (full suspension bushings and any other wear items I can find), as well as some H&R sway bars, and coil overs. what do I need to be able to keep up? (Not concerned with pulling on them in the straights as this wont happen, but I need enough power to get some speed to maintain in the corners)

4. Giles pump. Want to do this... donít want to drop $1k until I get the rest of my stuff done first. This seems to be the best overall mod... but I want all of my other ďsupporting modsĒ done first so I donít have to send it back. Thoughts?

I initially bought this car to use as a commuter, then found out the low production numbers of the ECOdiesel, decided to restore to original, then found out it has already been modified with a 1.8v intake box and the pump was turned up... so Iím now wanting to mod it for the back roads. I will probably split my commute between my GTI, Bike, and the Jetta... so I want to make the Jetta fun and not beat my GTI to ***.

Idea 1: can I use an air-to-water from a junkyard car (I think the F250 uses one), or is this going to be too much flow for the motor?

Idea 2: I plan on getting a mini freezer (16Ē x 17.5Ē) to bolt into the trunk. Putting a couple  transmission cooling radiators connected to each other, and run my air-to-water intercooler coolant through it. Has anyone thought of this? Would a mini freezer be enough to cool the temperature better than one of these coolers mounted in front of the radiator? A fuel cell filled with ice water is the other option, but I donít want to add 40lbs for 4 gallons of water and a fuel cell.

Idea 3: Iím wanting to make my own bumper out of fiberglass or carbon fiber, then paint it to match. I have done some bodywork on my motorcycle and think I can manage not to screw up a front bumper. Then Iíll do the same with the rear bumper, the front fenders, and maybe the dashboard. These seem to save about 20lbs on each fender, 15lbs on each bumper, and a few lbs on the dashboard. This would be enough to offset the weight of the freezer in the back and the A2W intercooler in the front. Would this be good weight savings, or are there easier options that I could make myself? I went to a pretty good welding school and will be getting a tig welder soon, so Iíll probably fab what I can... saving money and keeping myself busy in the meantime.

I just bought all suspension related bushings, belts, o-rings, water pump, a few sensors, and all of the hoses under the hood. Any other maintenance items I should get that I might have overlooked? Iím trying to get this to be as reliable as I can first, then start on the mods I can do myself, then jump to the ones I canít (Giles pump). Any suggestions would be greatly appreciated.

Thanks in advance for any tips you all can provide.

Also, good links to parts are greatly appreciated, but not necessary... I am using my google-fu to track down some little odds and ends I need to bring it back to what it should look like in the appearance department.


1991 Jetta ECOdiesel
2019 GTI
2001 Suzuki TL1000R

Reply #1May 07, 2020, 07:24:27 pm

libbydiesel

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Re: New (to me) 1991 Jetta ECOdiesel, performance mods, and ideas
« Reply #1 on: May 07, 2020, 07:24:27 pm »
I like the 1.6TD engine but now that we're 40 years after it was designed, it seems to me that for a reliable 150hp, you'd be ahead both in labor, financially, and reliability starting with another engine.  I have a 1.6TD in my '79 rabbit and IMO it scoots quite nicely.  It is un-intercooled, running stock boost pressure, and moderately fueled.  Probably close to stock 70hp.  It is most economical in both the short term and the long term for me to just enjoy the car for what it is.  If I wanted a relatively easy and reliable 150hp in that car, I would swap in a Mk3 mTDI (and trans). 

If you are set on that hp from that engine, your process sounds reasonable.  I doubt it will last all that long, though.  You should also add a trans swap to a Mk3 or mk4 manual trans. 
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Reply #2May 07, 2020, 09:15:25 pm

Johnnyboy707

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Re: New (to me) 1991 Jetta ECOdiesel, performance mods, and ideas
« Reply #2 on: May 07, 2020, 09:15:25 pm »
Yeah I was thinking of picking up a donor car to do a full swap as an option as well. Sure would be a lot of down time, but probably worth it in the long term reliability aspect, like you said.

Out of curiosity, what mk4 trans will bolt up? Any concerns with this? I had a mk4 2.0 8v and loved how that transmission felt. Do the mk4 diesel trans feel the same?
1991 Jetta ECOdiesel
2019 GTI
2001 Suzuki TL1000R

Reply #3May 07, 2020, 11:29:57 pm

fatmobile

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Re: New (to me) 1991 Jetta ECOdiesel, performance mods, and ideas
« Reply #3 on: May 07, 2020, 11:29:57 pm »
 The VNT 15 turbo and a fat exhaust really changed my car.
I have 2.5" but 2.25" is probably plenty.

Because of the prechambers I probably wouldn't try for 150 HP with a 1.6 IDI.
Where are you at?
 Wanna buy a MK3 TDI engine?
Tornado red, '91 Golf 4 door,
with a re-ringed, '84 quantum, turbo diesel, MD block

Reply #4May 08, 2020, 01:36:42 am

libbydiesel

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Re: New (to me) 1991 Jetta ECOdiesel, performance mods, and ideas
« Reply #4 on: May 08, 2020, 01:36:42 am »
I haven't swapped a Mk3/Mk4 manual trans into a Mk2 so I can't comment on the details.  The engine to bell-housing bolt pattern is the same for Mk2/Mk3/Mk4.  The shifters are completely different (mk3/4 are cable shift).  I'm not sure about trans mounts or driveshafts. 
Use, abuse or ignorance of any information is at your own risk, confirmation or refutation is your own responsibility, no further 'proof' will be given, take it or leave it, YMMV,terms subject to change without notice, avoid contact with eyes or skin, contents known to cause cancer in California

Reply #5May 09, 2020, 03:45:55 am

Johnnyboy707

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Re: New (to me) 1991 Jetta ECOdiesel, performance mods, and ideas
« Reply #5 on: May 09, 2020, 03:45:55 am »
Fatmobile: I am in MD near the D.C. area. I think shipping would be pretty expensive, but Iím interested. What would all have to be done to make it work? If I got your TDI, I wouldnít have a donor to swap what I needed. Is this something that would be a pain?

Libbydiesel: yeah I remember the MK4 being cable shifted. They are relatively easy to install with a couple inches of cutting and a couple holes drilled. I think that would be fairly easy to do if the bolt pattern and spline for the eng/trans are the same.
1991 Jetta ECOdiesel
2019 GTI
2001 Suzuki TL1000R

Reply #6May 10, 2020, 01:47:40 am

fatmobile

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Re: New (to me) 1991 Jetta ECOdiesel, performance mods, and ideas
« Reply #6 on: May 10, 2020, 01:47:40 am »
Actually the MK3 works good for the MK1s because of the motor mount.

 I have a couple threads in the MTDI fora about my 2002 ALH block into a MK2 Golf.
Tornado red, '91 Golf 4 door,
with a re-ringed, '84 quantum, turbo diesel, MD block