Engine maintenance and tuning tips. VW Digifant Troubleshooting
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1. the Ninja had a very well thought out ram air intake with two boxes plenums along the intake path which seemed to augment the intake airstream by providing a ready source of slightly pressurized air Top speeds were around 150mph or so VW appears to do something similar with the airbox and the intake manifold One bike that is a real feat of engineering is the Yamaha Thundercat No it s not available here But Yamaha really did their airflow homework It s put together so effectively that the intake increases the compression ratio by 1 or 2 points 2 1 The intake pipe I ve done some measuring comparing the Digifant airflow sensor outlet area 4 sq in to the pipe square area about the same and the throttle body area over 7 sq in The airflow sensor has the smallest area therefore replacing the intake pipe will yield little or no gain It may help smooth the airflow but the sensor is the high airflow read high power limiting factor On CIS cars the S pipe could be replaced with a 3 pipe with a 45 roughly bend at one end aka Sewer Pipe This maintained a constant diameter from the airflow sensor 80mm app 3 thus minimizing airflow directional changes and maintaining velocity better Does it improve horsepower don t know NOTE according to a chart denoting tuning tips in the Dec 90 issue of European Car Digifant is good for 160hp 2 2 Porting the cylinder head and intake and exhaust manifolds Several small gains can be mad2. smell cast iron for two days after you re done mention this on my diesel performance page when talk about match porting the exhaust manifold to the downpipe You don t want to use the stone on aluminum because the stone loads up with aluminum High speed steel gets dull REAL quick on cast iron so use the stone there It s slow going but it works 3 Geta K amp N air filter It costs the same as the paper replacement yet you never need to replace it Great if you re environmentally concious or just want to reduce the amount of maintenance you do Just clean it every 50 000 miles http home earthlink net glime2 AutoTune htm 6 25 2001 Auto Tuning tips Page 3 of 4 use laundry detergent and water and let it air dry overnight no compressed air 4 Do you plan on keeping the car for a while mean over 100 000 miles Use synthetic engine oil use Mobil 1 If you don t want to spring for synthetic be sure to change the oil at 3000 or 3500 miles For the environmental types there are now oils that include 25 re refined oil i e recycled oil that s been refined and the impurities removed Just as good as conventional oils Oil wears out and gets dirty with combustion by products Use a good filter and change it with every oil change If a filter fills up with dirt it starts by passing Meaning the oil still flows through the engine but not through the filter You get the idea use NAPA it s really a WIX filter with a NAPA part n
3. Auto Tuning tips Page 1 of 4 Updated 12 July 2000 Engine maintenance and tuning tips How your car engine works 1 exhaust VW Digifant Troubleshooting 2 airbox and intake mods porting tips hard hot engine starts 3 K amp N air filters awkward off idle acceleration 4 engine oil 5 fuel 6 Ignition wires Other info 7 Diesel injectors and glow plugs Turbos blowers Nitrous 8 Distilled water VW Audi site links Revised and separated 9 Spark plugs Performance chips 10 corroded wires Do you live near Oklahoma City OK 11 Poor man s slotted brake rotors Want performance parts installed on 12 Audi 5 cyl spark plugs NEW your VW Audi Drop me a line Oh nearly forgot Someone previously asked me what my VW experience was Okay here it is I ve worked on several 78 diesel Rabbit 2 81 diesel Rabbits 84 Quantum 5 cyl 84 Jetta GLI fabulous car 90 Audi 100 and a 91 Jetta I ve installed shocks springs complete exhausts stereos alternators gauges a transmission that really didn t need to be swapped got nervous about the mainshaft circlip thing rear axles braided steel brake lines brake rotors drums rear brake cylinders camshafts parking brake cables what a pain water pumps smile stress bars upper ones are easy sway bars etc almost got to swap head gaskets on a diesel once It started to run really bad and when pulled the head off discovered the 2 connecting rod bolts had b
4. I m running 0 045 gaps now I really didn t want to go over 0 050 10 Want to remove corrosion from copper wires around the battery Coat them with ketchup It works You may have to clean it off later and repeat depending upon how bad the corrosion is but it should come out clean 11 Slotted or drilled rotors are expensive and it s hard to get long pad life since the rotor surface tends to chew them up more slot the brake pads instead Just cut a groove with a hacksaw through the pad perpendicular to rotor rotation and that s it However I ve found that brake dust tends to fill that skinny groove so this last brake job used my Sears angle grinder and cut a 1 8 slot The slot allows the brake dust a place to escape and helps keep the heat down 12 learned the hard way not to put Bosch Platinum 4 spark plugs in my Audi 100 It starts harder and stumbles more after starting The original and best plugs are NGK BP6ET or Bosch W7DTC Triple electrodes that really do the trick called my local Audi dealer and they pull these Bosch plugs out at 60 000 miles just to check them Not necessarily for replacement Do you have any tips Was this page helpful Give me the details and I ll add them to my list Send them to glime2 earthlink net http home earthlink net glime2 AutoTune htm 6 25 2001
5. e here as well as engine smoothness increases Don t go crazy when removing material Tom Cloud s page covers his work on a GT 40 engine big block Ford but read through it and summarized it here Remove all burrs in intake and exhaust passages they obstruct airflow P olishing combustion chambers prolongs onset of deposits after this you can cc the chambers if you re really anal making them the same size makes compression the same cylinder to cylinder helps produce more even power Doing this requires using some plexiglass a buret some white grease some mineral spirits and a clean cylinder head surface Remove combustion chamber burrs this avoids hot spots Hand lap valves to ensure good seal Don t depend upon spring pressure Match port cylinder head to both manifolds continues smooth airflow V alve guide bosses just blend material around them to create a smooth contour you don t want to weaken the area Remove ridges around valve seats in combustion chamber and ports most airflow differences are at low valve lifts Why Your valves spend much more time at low lifts than they do at high lifts Intake airflow is more important than exhaust flow Yes exhaust is important but if you don t get air in you don t have to worry about it going out Use a dremel with high speed steel for Aluminum or stone bits for cast iron and wind it out Get a mask and some hearing protection Trust me You don t want to
6. it creates a low pressure area in the exhaust pipe thus making more room for fresh air and fuel More power Originally featured on the 1 6L GTls and most factory performance cars 2 Open up the airbox On VW Digifant cars others are probably similar remove airbox take out the restrictor the vacuum control and such and seal up the hole to the hot air stove on the exhaust manifold unless you re really worried about cold weather cold engine performance This will help a lot Dyno proven by Automotive Performance Systems on a 90 Passat good for 2 3hp You also get a nice intake howl when you put your foot down Picture Howto remove the 2 rubberband hold downs loosen the intake duct clamp at the airflow sensor take off the airflow sensor wiring connector and loosen the clamp on the hot air hose Il removed mine Now undo the clamps and remove the top The air filter might stick just pull it loose In the bottom you ll see what looks like a funnel ending at a flapper of sorts Remove the funnel It will come out the front you have to hold your mouth just right If that s all you want to do put in your K amp N and reinstall the top on the bottom then put the airbox back in the car Reconnect everything and road test You ll hear a throaty growl when you floor the loud pedal To seal up between the airbox and the headlight enclosure used a piece of foam and cut a hole to match the airbox opening This helps ensure you only get cold ai
7. ou release the gas pedal some I ve also been told to avoid using Platinum plugs with the Jacobs wires something about not storing or carrying enough energy through the wires seems to work just fine for me though So what is this bigger gap going to do for you The larger gap exposes more spark to fuel air mixture thus helping light the fire and giving you a more complete burn This helps economy Just don t overdo it Too large a gap is really hard to light off during starting You ll notice this if your gaps get up around 0 050 or so x Oh The Jacobs wire modification is simple had to do this when discovered that one of the wires arced directly from the wire to the cylinder head clearly visible at night Rub some car wax on each spark plug at the top where the wire end covers it Let the wax dry DON T WIPE IT OFF and apply a bead of silicon RTV around the top of the plug I used red Now install the plug wires onto the plugs Actually do the plug wires one ata time It s really a pain to figure out the correct order if you screw it up Let the car sit overnight and then pull the wires off one at a time just to ensure they ll obey Stick them back on and you re done The wax acts as a release agent RTV does a fine job of keeping the spark in 7 Diesels make sure your injections spray at the proper pressure Too low and they really affect performance http home earthlink net glime2 AutoTune htm 6 25 2001 Auto Tuning
8. poor lubricant 5 ALWAYS run good fuel use Amoco Ultimate premium 93 octane or UPDATE Sinclair no Amoco here in Oklahoma I ve tried other flavors Texaco and Shell but these work the best Also avoid gasohol whenever you can if you own either VWs or Audis For diesels make sure the fuel is fresh Truck stops are a good prospect Amoco makes Premier Diesel and Union 76 offers Super Diesel Both have a little higher cetane rating a measure of the fuel s energy rating 6 I m using Jacobs plug wires However Blue Ignitors are purported to be good stuff I ve not tried them Factory ends and such Anyhow Jacobs wires have really low electrical resistance approximately 1500 ohms for the longest wire on my car versus the shortest stock wire at 7500 ohms These do work but you need to modify just a little Don t even try the ignition Digifant don t play that The car runs well with Jacobs wires and stock ignition These wires allow you to open up your plug gaps another 0 015 or 0 020 thus exposing more spark to the fuel air mixture On a 1 8L 8v this equates to 0 042 0 047 I m currently running 0 042 Go above 0 050 as Jacobs tech reps recommend and at low rpm and with heavy throttle input the car will stumble a lot as the ignition can t spark across the gap with so much air pressure You kinda blow out the spark It s really weird to be going along in 5th 1500 1600rpm and stand on the gas and feel the car slow down until y
9. r If you really want to go all out remove the flapper and the vacuum actuator and http home earthlink net glime2 AutoTune htm 6 25 2001 Auto Tuning tips Page 2 of 4 the hot air inlet Then seal the holes with some of the pieces you removed and some RTV to glue them on what did why not you re not using them You could leave the holes open but that lets in hot engine compartment air reducing the amount available and hence reducing power Cold air intake and cost I m cheap are the two reasons did this mod Yeah snowmobile air filters are popular but see the next tip This reminds me remember reading that the typical engine compartment temp is approx 160 F Now for every 10 F temp increase your engine looses 1 hp On a 100 F day with a snowmobile style air filter you ve already lost 6 160 100 60 60 10 6 On a 60 day you ve lost 10 Not good This would likely show up in city driving when airflow through the engine compartment is low Ram air A well known racing team with a Porsche 944 Turbo has a ram air intake and according to dyno testing they ve only seen about 3hp increase at 150 mph The increase is proportional to velocity squared So at typical highway speeds 65mph or so you may only see 1hp However it s free In a motorcycle magazine read a few months back a Ninja had the lowest dyno hp yet on the road it s top speed around 150mph was higher than two bikes with more dyno hp like 1 or 2 more However
10. roken the piston hit the valves Oops Yes VW Digifant can perform as can any engine management system Here is what I ve discovered thus far Most tips really apply to any and all engines not just VWs NOTE When you start your project car get some advice about what to buy and what parts work together and what parts don t Don t blow your wad on one item and have to skimp on the rest Balance is the best approach I E don t use your stock springs with really stiff shocks or don t opt for drilled and slotted brakes and have to buy Hakiko s discount tires You get the idea Also don t neglect yourself Invest some time in a driving school At the least buy a book like Bob Bondurant on High Performance Driving and read and heed it He has many good tips for street driving 1 Get a free flow exhaust One that is dyno proven Go from the head to the tailpipe Make sure you get a performance muffler and mandrel bent pipes they have smooth bends no kinks or necked down areas necessary for high exhaust flow Techtonics Tuning is my favorite Use a dual port exhaust manifold If you re gonna spend the money make it count You can also wrap it with a high heat wrap to retain heat and move the exhaust gases even faster See my Diesel performance page A SuperTrapp muffler allows you to tune your exhaust to vary your engine s power curve Why a dual port manifold A dual port manifold helps scavange more exhaust gases out of the cylinder
11. tips Page 4 of 4 Remember always replace the heat shields each time you remove the injectors Also check your glow plugs as this can be a quick tipoff to poor injector performance I ve seen some glow plugs with half the tip gone Also if the car starts hard in cool weather check to see if the fuse or fuseable link on the firewall in US built Rabbits is still good Glow plugs don t work without juice push started my car for a week once til figured that one out 8 Use distilled water in both your battery and your cooling system Yes both Why Plain tap water has lots of minerals and other goodies that are okay for drinking but bad for engine and battery internal parts Minerals and such tend to accelerate corrosion of copper aluminum iron etc Distilled water doesn t have all of this stuff essentially pure H20 so the impact on internals is much lower as waiter is a very stable molecule Reactive things start the corrosion process 9 Use good spark plugs I ve modified mine Bosch Supers so that the finger is rounded and terminates just above the electrode tip Why It worked good on my pushmower figure I m unshrouding the spark a little more Look at some Allied Signal spark plugs They do the same thing but have a fancy electrode tip Bosch Platinums look similar to what did UPDATE Bosch Platinums allow the engine to start a little easier and run smoother I ve found can run a little larger plug gap also 0 003 more
12. umber WIX is good stuff Fram isn t constructed as well I ve seen inside both tried the Mobil oil filter It has synthetic fiber inside instead of paper and is touted to stop more contaminants 10 a shot though ouch don t think it s worth it I ll stick with NAPA Why synthetic oil It s more expensive but cleans much better and resists breakdown i e heat and pressure literally tearing down the oil better than conventional oils With conventionals you really need to change oil regular i e 3 000 miles The products most people and most quick lubes use won t last much beyond that Synthetics pour easier and flow better also especially in cold weather When they first came out synthetics got a bad rap because they were so high detergent they d clean out the gaps in engines gaskets that the conventional oil previously plugged and cause them to leak oil Nowadays gaskets seal much better and resist that tendency With a diesel heartily recommend synthetic OR changing the oil and filter at 2 000 miles or so Diesels really get the oil dirty and they have more internal friction due to the increased compression they are much harder on oil Another tip Shake your oil bottles a little before you dump them into the engine There s a little additive that tends to settle out when the bottle sits for a long period of time Anyhow this additive antifoam agent prevents oil from foaming during engine operation Very important as air is a
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