VW GTI - Heavy modding done - what next?
 

Sooo - I have had this 1991 VW GTI for almost 3 years now - and for the first 2 it was getting aobut 21MPG. In August of last year we fixed that with an AHU TDI:

MKII VW GTI Gets a TDI Engine in 3 days - YouTube Video

I'ts mostly modded to go fast so I was shocked at how good the MPG was once I started driving it. I'm really hooked now! I even drove a whole 1100 miles as carefully as possible just to see how it does and was able to get it up to 78MPG! :D though the lifetime average is only about 60MPG.

Since the swap I have added the following eco-mods:

1: High temop thermostat (92 rather than 87 degrees)
2: Taller 5th gear (.622 was .756)

My question now is - what else can I do without getting really crazy? I want to keep it looking as stock as possible. Here are my thoughts...

1: Maybe a belly pan of sorts
2: LRR Tires (already in the plans when it gets 5-lug and Porsche brakes)
3: Some sort of tasteful grill block?
4: Maybe eventually go 6-speed with a .59 5th gear

This site has been a great resource so far - and I think the best info for future MPG gains will come from all you you MPG gurus. :thumbup:

Grille block - Coroplast behind the grille. Nobody will see it.

Try water injection, it might work out for you. Remove the vacuum pump from the motor and grab an electric vacuum pump, pressure switch, and reservoir, or just switch to manual brakes. I can't remember how the AHU develops vacuum, but I believe it's the same as my old Golf D 1.6NA, with a vane pump attached to the oil pump. Open the lid, remove the vanes (they slide out) and put the lid back on, then leave about an inch of hose connected and screw a bolt into it, or remove the hose and put a cap on the nipple.

Boost will enhance the efficiency of the diesel. The KKK K03 turbo from a New Beetle bolts on and no intercooler is necessary for low boost, you just need to turn the fuel up to compensate for it. Don't turn it up until you see the haze unless you want more power, just get it to that point, then back it off slightly. You'll just be using less pedal when driving normally.

Electrical mods. You dont' need the radiator fan unless you drive in heavy traffic or let the engine idle frequently. Based on your current reported numbers, I doubt either is the case. If you want protection from overheating, install a tube with holes that will spray water at the radiator and another washer fluid reservoir/pump. If you notice the temps climbing, spray the water to insta-cool the radiator. If it happens frequently, reinstall the radiator fan.

If you don't use accessories frequently, consider an alternator delete and a deep cycle battery or two. Added weight, yes, but the draw removed from the engine will more than make up for it. If you do this, I suggest you pop start as often as possible to keep the starter draw off the system, and mind your night driving (headlights).

I'm fairly certain you don't have PS, but if you do, get rid of it. It's not necessary on such a light car. Best bet is to swap in a manual rack, but looping the hoses works as well. More weight lost there, as well as parasitic engine drag.

Advance the fuel timing. You'll get a more complete burn, more power, and better economy.

Do not advance injector timing
 

I like that behind the grill block idea - and I will want it to be easy to remove as this car isn't just for MPG - it's also my go-fast car. :D

I wonder if water injection would really help FE - I will need to look into that. I know it would help with charge air temps and allow me to run more fuel for more power though. :D

The AHU has the same style pump as the 1.6 NA - I wonder how much power it uses to build and hold vacuum. I suppose I could hook an electric motor to one and measure current draw loaded and unloaded to find out and then see if it's worth the trouble. Manual brakes won't solve the vacuum issue for me as I have installed a VNT turbo and it operates its vanes with vacuum.

The New Beetle is equipped with a Garrett VNT15 stock. the KKK K03 you are referring to is the factory turbo from this motor. I removed it and installed a KKK/Borg Warner BV43 from a European 2.0L 16V 170HP TDI. It's capable of supporting 25psi of boost through most of the rev range.

Radiator fan has never come on. And idling causes my temps to drop - I believe this is due to the unusually lean burn of a TDI at idle. I will be keeping the fans though. This is due to my frequent hard driving and the fact that it will be at the top of Pikes Peak and Mt. Evans this summer along with some other demanding situations. I can't see any advantage of removing them aside from saving the 5.6LBS.

I forgot to mention that I have addressed the Alternator issue as far as I'm willing to. removing it would be a bit more driveability-killing than I want. I removed the stock serpentine belt assembly that went Crank-Idler/Tensioner-120A_Alternator-AirCon and the V-Belt that went Crank-WaterPump-PowerSteering. I am now running a setup that uses the smaller 90A alternator as the tensioner. It goes Crank-WaterPump-Alternator. It is also manually tensioned and not as tight as VW had it. no slipping problems yet. :)

You are correct - I delted the PS pump when I removed the serpentine tensioner and A/C. It now has a manual rack from an 86 Golf.

The tune i have from TDTuning takes timing as far as my tuner (Mike) is comfortable taking it for the power and FE goals.

Thanks for the input Christ! :D

I will keep the IP timing just where VW wants it. :)
I have VCDS
And thanks! :thumbup:

why do you think this? My experience is different if the original engine has "enough" power to keep up with traffic.

I agree - the advantage of the turbo only really comes in when you can use it to produce more power from a smaller engine. This allows for less internal resistance from the engine itself. I think most gains people see are probably due to the typical non-turbo diesels running a little richer than needed and not enjoying the benefits of a complete burn.

Any reduction in pumping losses is a benefit to efficiency. How you use it makes the difference.

Cool swap! You are getting some really good FE numbers with it. I have been thinking a TDI swap into a Mk II or III would be a fun car to have. Less weight and frontal area than my Mk IV TDI. I used black foam pipe insulation stuffed between the bars for my grill block. It is pretty stealth on a black painted grill (see if you can spot it in my avatar). It is really quick and easy to add or remove depending on conditions. The diesel needs surprisingly little grill area because they run so cool. I have the upper blocked year round even climbing the passes and part of the lower blocked in all but the hottest weather. I priced the Snow Performance H2O/Meth injection kit and at $750 it would take a long time to break even on fuel savings. Might be worth it for more power on Pike's Peak but probably not for hypermiling.

If you have the OBDII port from the TDI a Scanguage is very useful. Instant and trip mpg, real time water and intake temps are nice to have. Can really help teach you when to EON (engine on) coast or to overrun (go downhill in gear-@ 9999mpg).

I deleted the passenger side mirror and folded the driver's side with a blind spot mirror glued to the glass. Also, I am sure you know you don't really need a muffler with the turbo and the cat. I substituted a straight pipe for it to make room for a flatter belly pan. I have a full belly pan from the front bumper to the back. No need to worry about exhaust heat anywhere except the cat/con. (see photos in my albums)

I am curious about tunes on a diesel for better mpg. UFO was trying to eliminate EGR for better mpg but it seems to have hurt his warmup times. If you have a tune that you think helps mpg I would be interested to hear your thoughts.

More boost raises engine efficiency on diesel though you get diminishing returns as it increases.
http://web.archive.org/web/200611080...4/A6_1_022.pdf

The question of whether more boost will help on a particular engine depends on how much more energy it takes to create the additional boost, the efficiency of the system doing so, and the increase in friction due to running at higher pressures (note that the above paper showed efficiency increases all the way up to five atmospheres).

P.S. DO NOT do a WVO conversion but I seem to be getting better mpg with B20 biodiesel. It has better lubricity for the injector pumps as well.

The other place boost is magical is at higher altitude. Without it life does suck.

Amen!!!

I've never tried it in a AHU, but I run various mixes of used motor oil, hydraulic/brake fluid, and transmission oil, as well as raw gas (mixed in, except that one time) in my Golf D. It hasn't damaged anything yet, and I know people that have been doing it for as long as they've owned their cars with no perceptible issues.

I rarely buy highway diesel for my truck or the Golf. Well, I don't buy anything for the Golf anymore, it's sitting on stands waiting for the engine and cradle to be pulled.

I'm quite impressed with the FE myself. And the foam stuffed in the grill idea is great - that will probably by my next thing as it's quick, cheap, and temporary. I will probably not be doing H20 injection anytime soon though as my energy and $ are going in to getting the VR6 suspension, 300x25MM front brakes With Porsche calieprs, and LRR tires - lookl like I will get the Pirelli P7 Centurato 185/55r15.

I already ahve a scangauge installed - it's quite helpful. I find it overestimates fuel consumption when driving hard and underestimates when driving really carefully.

I could easily delete mirrors with OEM blockoff plates - but the safety loss isn't worth it to me. I am also without muffler or Meow right now. Just 2.5" Turbo-back with nothing in it. It's not really very loud at all, and the older VW diesels didn't have cats. I really like the flat belly pan idea - I will need to look into making one for this. It doesn't look all that difficult.

I have no EGR on this either. Warmup is very long - and I wouldn't say my tune improves MPG... the goal of the tune is more power, without hurting MPG. I'm probalby about 120WHP now - and will be making much more once my new nozzles arrive and I get the new MAP sensor board designed and installed, followed by a remap.

Quite the interesting article on boost... I buess more is better! :D

I can get B5 here for a really good price - may give that a try. :) WVO is not for me.

interesting use of various flammible liquids to run a diesel... I'm going to stick with something a bit more proven though.

Belly pans on the MKII VWs works VERY well. If you don't have the front factory belly pan in place, that is my best recommendation to start. Full pan is better, but just the front is considerable.

I started with an upper grill block, black ABS plastic behind the stock grill. No one ever noticed that I didn't tell.

Got looking at your fuel log the other day and couldn't figure out why I hadn't seen you before. Then I looked at your sign up date. Not a stalker, just another VW nut:thumbup:

factory belly pan huh? what do you know of this? ;) I actually have a VW/Audi group OEM belly pan that is full bumper to K-frame and up to the rails... it cost me a ridiculous amount of money though (almost as much as the TDI :eek:) - and I don't want to install it on this nasty K-frame. Once the fully Powder-coated K-frame and VR suspension go in and I confirm there are absolutely no oil leaks - the pan will go on. I will need to make one for the rest of the underside. I need to see what you did to yours... Time to start digging. And if you didn't do a detailed post, I will be beging you for details. :D

No problem. I started hosting pics in my Ecomodder album here but moved to photobucket here. I can see from your website that your and my methods are a bit different, but you might get some ideas from my screw-ups:D.

Great video, thanks for sharing.

Thanks - those pics are a great resource for when i start doing my belly pan - since you can't see it at all from any normal position - I would be willing to do a full pan for better MPG. It would be good for top speed too. :D

Thanks! It was my first attempt at time-lapse with the hacked canon point and shoot (sd750). :)

Brilliant! I've been trying to figure out why my MPGuino reads differently from time to time. I think it's reacting opposite to your Scanguage. Must be a VW thing:thumbup:.

Well, the GTI is getting decent MPG even after the very non-eco-minded mods it got (bigger nozzles, more boost...) I think MPG over 60 can still be a normal thing if I keep my foot out of it. I'm just glad it climbed out of :snail: status and can get out of it's own way ok now. Here is the best run from last night:

1/4 Mile in 14.658 Seconds at 94.757 MPH:

GTI TDI Run 5 14 658 at 94 757 - YouTube

Nice run for a 4-banger diesel. Nice ride.

I am envious. I had an 84 GLI, and later a 91 Jetta. Both would have been good diesel candidates. The 91 had PS that I deleted. It'd get low 30s for mpg... I am tempted to find a similar car and engine and try this myself.
Besides the grill block and belly pan, you could make some small fairings to put in front of each wheel/tire to guide the airflow around them. Maybe a rear wheel skirt too...

While Frankencar indicated his desire to keeping the car looking as "factory" as possible, his MPG success leads one to wonder what would be the (MPG) result if one took an old VW, transplanted in the diesel and gave it the full "basjoos" treatment.

I had a 92 turbo diesel (not eco diesel) and it would get 5.2L/100kms (45mpgUS) all day long with only cruise used on the highway, I didn't know about aero at all back then. I got ~4.3L/100km (55mpgUS) a few times on some long summer trips when there was no wind. Good car for fuel economy, I was always seeming to tinker with it trying to get it not not run too hot.

Probably not going to do wheel skirts - or if i do, something tasteful and easily removable, but the small fairings in front of each wheel could be discreet and would probably make a big difference. Te wheels are very much out in the wind on this car.


Not a TDI, but a VW soon-to-be-diesel with the full Aero stuff - I bet it will get crazy good MPG! http://ecomodder.com/forum/showthrea...tml#post263738

Some IDI's run hot - not sure exactly why. My TDI tends to run very cold. On cold days (and I'm talking below 55 F! :p) I can't ever get it up to temp. I will definitely need to get a grill block done before the summer is over. My current project is to get a complete new suspension in it with bigger brakes to help slow this thing down and it will be getting some LRR tires and the belly pan while I'm under there. I'm trying to get it all in before my road trip to Colorado this summer. :eek:

thermostat
 

My TDI tends to run very cold. On cold days (and I'm talking below 55 F! ) I can't ever get it up to temp.

replace the thermostat , use a VW part do not use aftermarket

Did that - then upgraded to 92 degree thermostat - still - no dice. It's just that light a load. :turtle:

Make the EGR optional instead of blocked ?

With the turbo setup I have - that's not something I will be doing. It would help make it warm up though. I think I will go with a belly pan and some grill block stuff when the summer ends. :thumbup:

And I finally got some LRR tires:

http://i155.photobucket.com/albums/s...r/93009e58.jpg

I still need to get the rear spindle adapters from the machinest in order to install the rears, but the front is assembled - along with bigger brakes and axles to handle the torque of the TDI. :D


http://i155.photobucket.com/albums/s...r/IMG_0332.jpg
http://i155.photobucket.com/albums/s...r/5219db31.jpg

That's just candy, right there:thumbup:. Any semi used parts you want to get rid of, just let me know:D:thumbup:.

Most of what I have is to increase track width and bigger brakes... I think you are looking for the opposite - keep the wheels tucked under and the rotating mass light right? I bet rear disks would be a welcome addition though (less drag, lighter weight) maybe I have some spare rear disk stuff in one of my boxes... If I come across any and make it out to Bonneville I can bring them... :) anything in particular you are looking for? we still get a good MKII in the Junk yard out here occasionally. :thumbup:


And here is the thread with the full detail of the suspension work:
VWVortex.com - GTI TDI Gets a minor suspension overhaul, mostly VR6 & Boxster parts

Nice custom license plate too :)

Rear disk would be awesome:D I'd like to change over to vented disc in the front. I have solid now( came with it). Looks like I could get away with a new rotor and caliper, but I'm not sure. Also if you have any lowering springs( front and rear), let me know. I want to drop mine and raise it with air so I can drop on smooth roads and lift when it gets a little rougher:cool:.

I hope you do make it to Bonneville, we're starting to get a pretty good crowd:D. I want to see that baby run the mile:thumbup:.

Yeah - If you are interested in MPG over everything else, stick with the tiny front brakes and step up to vented to allow for better fade resistance. Anything bigger starts to get heavy real fast. I'm sick and weighed all the suspension parts... Vented fronts should easily keep up with that 54hp diesel too. :snail:

And I really do hope to make it. I'm currently swamped with trying to get the rear end done so I can get the LRR tires on the rear before my 2-week road trip to Colorado next week. Once i'm back I can focus on what it would take to run at Bonneville. :turtle:

Another update:

Installed Mercedes G500 headlights and clear inners this weekend. :D

Removed the stock lights:
http://i155.photobucket.com/albums/s...r/6af30893.jpg

Installed the Merc lights with some adapters I made:
http://i155.photobucket.com/albums/s...r/dd3a702c.jpg
http://i155.photobucket.com/albums/s...r/86c49145.jpg

Comparison:
http://i155.photobucket.com/albums/s...r/109c7797.jpg

And the final product:
http://i155.photobucket.com/albums/s...r/b14d6cfd.jpg

The result is a much wider and more even beam pattern. the 50W HID's in the inner lights also make the high-beam performance scary good. :thumbup:

Installed a NEW chrome rear VW emblem. It has been NLA for a while now, I was lucky to find one. I also installed a Fiat Marea weekend estate rear wiper on a pre-89' wiper hub. :)

http://i155.photobucket.com/albums/s...r/1c67b985.jpg

And I finally installed this:

http://i155.photobucket.com/albums/s...lyPan011-1.jpg

It's a Seat Toledo Belly pan - needs some trimming up front to fit behind the bumper, but makes for a nice underside! And I can't believe how much quieter the car is now! Now it's just the sweet TDI 2.5" straight pipe exhaust note. :thumbup:

http://i155.photobucket.com/albums/s...r/IMG_0346.jpg
http://i155.photobucket.com/albums/s...IMG_0347-1.jpg
http://i155.photobucket.com/albums/s...r/IMG_0349.jpg

And finally the small plastic air channels that go in front of each wheel:

http://i155.photobucket.com/albums/s...r/IMG_0350.jpg
http://i155.photobucket.com/albums/s...r/IMG_0351.jpg

I'm hoping this improves FE a bit. :)

nice looking ride ;).

People you need to remember that more power does not necessarily mean you would need bigger brakes. If you still drive only the same top speed as with old power. Or even if you drive faster you dont need them if you dont start racing it so making many hard brakes after each another...

Exactly. The brake upgrade is for when I go driving like a hooligan. ;)