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These are Digifant-related Q&As collected from various pages of http://www.europeancarweb.com, for those of you interested in digifant reading... (Again, only Cabriolets 90-93 have digifant FI)

Q: Volkswagen Golf MkII
I was wondering if it is possible to put a 1988 Golf Digifant injection on to my 1987 Golf? (Both cars are 1.8L 8V engines.)
Jordon Palmer
via the Internet

A: While it is certainly possible, it really won't provide any additional benefits, would be pretty expensive and would require extensive modifications to the vehicle, including wiring harnesses as well as all the fuel injection components. I'd stick with the CIS-e fuel injection system you already have in your 1987 Golf. The stock CIS-e injection is generally considered to be vastly more desirable.

Q: GTI 1.8 Power
I own a 1990 GTI Wolfsburg edition, with a stock 1.8l. I am interested in increasing the car's performance but don't want to change motors, as this car has under 40k original and is very tight. I have put oversized sway bars and tower flex on but would like to get more out of the engine compartment. Could you recommend improvements I could make? It seems this engine gets ignored with the 2.0 and 16V out there. Thanks
George G.

A: Unfortunately, you are correct. The 1.8-liter engine in your car does get ignored compared to most of the other motors in the VW lineup. The primary reason for this is the fuel injection/engine management system on that car. The Digifant II system is one that most of the VW tuners did not touch and therefore leaves you, the enthusiast, with fewer options for increasing the output of the existing engine. Your situation, however, is far from hopeless.
The first thing to do in the range of increasing engine performance would be the exhaust system. If you have the exhaust manifold with the single outlet, which came primarily on California cars, that is where you start. You'll need to replace that manifold and downpipe with either a factory dual-outlet manifold or a short header. You can usually get the manifold and downpipe from a dismantler. I have always had great luck using VW Parts (800/VWPARTS). They really know their Volkswagens and Audis and will be able to get you what you need. As for the header, the best thing out there is the Bosal Performance header (part # 999-776). t is extremely well made and fits perfectly and retains the catalytic converter. If you make one of these changes, you'll also need to replace the catalytic converter since the downpipe (or header) to cat flanges are different. The best direct-fit aftermarket catalytic converters I've come across have come from either Eurosport Accessories (www.eurosportacc.com) or Techtonics Tuning (www.tttuning.com). From there, it is a relatively simple matter of getting a performance cat-back exhaust system. I like the systems from all three of the companies above, and each has some different benefits.
After the exhaust system you should contact GIAC (www.giacusa.com) for a chip. They only list their chip for the 1991 cars with the ECU number ending in 023), and have been too busy with developing software for the new cars to get to the other ECUs.
After the above, I'd recommend a mild camshaft, such as the Neuspeed 260 degree cam (part # 60.10.21), which will add some additional top end performance, with little, if any loss in the low end.
The last things, which you clearly are not interested in, would be to replace the bottom end of the engine with a factory 2.0-liter one, and do some mild porting to the cylinder head. These would net a significant gain in useable horsepower, but would be far more expensive than the bolt-ons previously mentioned. Keep in mind that all of the above are virtually useless if your engine is not in good shape to begin with. Simple things, such as normal tune-up items, will really be the first place to start.Good luck.
Jeremy Wolf


Q: Digifant Dismay
I have a 1992 Jetta GL, with, much to my dismay, Digifant Injection. I like the car quite a bit and until someone gives me a 1.8T, I'll be driving this one--still it could use a little more power. Recently I saw a letter titled "Digin' Around" requesting info on how to upgrade the performance of such a car. Based on your reply (ec "Tech Letters," June 2000) I have a number of questions:
1) You state the Digifant system does not like aggressive cams. Would the addition of a reprogrammed chip alleviate this problem? Or would I be better off getting a Cam Adjustment Pulley (Techtonics or Neuspeed, any preference?) and either leaving the stock cam or upgrading and using the adjustment to dial in my power?
2) Your final total horsepower rating is something like 120, does that include the addition of the chip upgrade and cam or just the exhaust work and hotter spark plugs?
3) What about changing the Digifant out for another system? Is that a possibility? Which might you recommend?
4) Finally, what about the stock braking system? I've added drilled and slotted 9.4s with Mintex pads up front, but still have the drums in the back. Will this system cope with the increased power? If not, what are my upgrade choices?
Thank you in advance for any suggestions or help you can provide.

Greg Rogers
Wilmington, Delaware

A: For starters, Greg, if you enjoy the car, enjoy it. Don't worry about what we, or anybody else says. Digifant ain't so bad, and you really lose only a handful of horsepower, if that, to any other systems. Read what we have to say about your questions, and you'll understand what we mean. Now, for those questions:
1. Indeed, Digifant equipped engines do not like aggressive cams. Very true. In fact, neither do CIS injected engines nor Motronic injected engines. Here's why: all three injection systems measure the airflow into the engine in order to decide how much fuel to inject. If the air flows smoothly, it's measured correctly, and the engine works well.
If an aggressive cam is fitted, there can be pulses in the intake tract that flow backwards from the inlet valve. These same pulses give a hot cam that cool, rough idle. The problem is that the pulses confuse all three injection systems' air metering, and typically make the car lose substantial amounts of bottom end power. Honestly, no amount of top end power makes up for a substantial loss at the bottom end, especially on the street. As you've probably figured out by now, a chip can't change the facts we've stated above.
What about an adjustable cam advance? It is conceivable that an adjustable cam advance pulley like the Techtonics or Neuspeed unit could help the bottom end, but it would be at the expense of the top end. That is the way adjustable cam timing works: it "rocks" the power curve, stealing from one end to build on the other. The end result is typically no real gain.
When is an adjustable cam advance pulley a good idea? When a cam is designed or ground incorrectly, or the engine has been modified, and the timing marks won't line up. Since quality cams like the Neuspeed, Techtonics and Schrick cams are designed and ground correctly, it is unlikely that you'll find any serious gains with a cam advance wheel.
You can expect about 120 bhp on a 1.8 Digifant car with a chip, exhaust, cam and colder (not hotter) spark plugs. It doesn't sound like a lot, but that gain is one you will notice and enjoy. We'd probably go for the exhaust, then the cam, then the spark plugs, and finally the chip if we were tuning one.
Should you change out the Digifant for an earlier or later injection system? You're talking about a big job here, Greg, and not something to be taken on lightly. First, there's the legal ramifications--simply put, it's not legal to change the fuel injection system. Second, it's an enormous job that takes someone with expertise and patience - or both. Finally, it's unlikely that another system will add much more power, or even allow you to add much more power.
It's a good idea to think about upgrading brakes--you've already done the first step. The next step we'd take is to go to either 10.2 or 11-in. Either is a straightforward swap, and a number of tuners carry the parts to fit the bigger factory brakes on your car. It's the most cost effective way to go.
Do you need rear discs? Not really. The front brakes do 80 or 90 percent of the work, so going to the trouble to swap out and put in rear discs probably won't give a very big gain.
Digifant isn't all that bad, as you've already figured out by enjoying your car, and a 20 percent power gain is one you can feel and will enjoy. Happy Digin'.


Turbocharging an A2 8V GTI?
I've been an ec reader for about 7 years, and with the knowledge and insight that your articles and tech letters provided I have properly upgraded my 1992 8V Digifant GTI with all the standard bolt-ons. With the exception of intake and exhaust, my 95,000-mile 1.8L 8V engine is stock. I think it's really strong and very quick right off the line, but I'm now ready to put some real power down. I've read all of the recent turbo articles featured in ec and in VW Power and they made me wonder: Can I turbocharge this little 8V beast?
I've managed to get hold of a homebrew turbo system that was on an A3 2.0 crossflow Golf before it was sold for a Turbo Beetle. I have the intercooler, VW diesel turbo, oil cooler, modified oil pan, pipes, adjustable fuel pressure regulator, etc. I know it all works, but will it fit? I'm not keen on switching my GTI head to the 2.0 crossflow head, especially since the current engine is such a powerhouse. But remaining faithful to the GTI head would mean lowering the compression ratio, not to mention a motor-mount retrofit (involving relocating and welding a rear motor mount from a Rabbit into my Golf) so that the turbo, installed upside down, will have enough clearance. I have scoured the web for any info that I can find, but there isn't much out there. I've checked out http://www.8Vturbo.com and it does offer a turbosystem for the 8V Digifant. Am I looking for a headache taking this turbo route? I know that turbocharging works well on the 8V Rabbit and 16V GTI.
Would I be better off to sell the turbo system and stay naturally aspirated? I would put the turbo money toward a hot cam, adjustable cam gear and some higher-flow fuel injectors. Keeping in mind that all of my other upgrades were done on a budget, I don't want to go spending crazy! Keep up the great work; it is invaluable to us DIY-ers. By the way, Digifant fuel injection isn't as bad as everyone thinks. If you have problems with it, check out http://www.members.tripod.com/~fuelie/. .

Steve C.
Via the internet

A: Can you turbocharge your 8V engine? Absolutely. Will the turbo kit you have acquired "fit" your engine? No. Even if the plumbing would bolt in place (it will require at least minor changes, as your intakes and exhausts are in different locations--and what about the exhaust manifold?), the answer would remain "no," in the same sense that a wheel that physically bolts onto your car may not "fit." It is essential for good performance that a turbo be sized properly. The Volkswagen diesel (we assume you mean TDI) is all done by 5000 rpm, which is where you want your engine to be in the meat of its horsepower and torque. We strongly suspect that whoever brewed up that turbo kit didn't really know what he was about. Turbo selection is perhaps the single most important part of designing a turbo system. It is a complex subject that ec has addressed many times in the past and will continue to do so in the future--we plan on keeping readers apprised of the constantly changing rules.
Early turbocharged waterpumpers were based on a kit designed by Callaway. As that company followed the money with more expensive cars, and emissions inspections became more commonplace, the popularity of this system decreased. However, we can't remember seeing an 8V turbo setup that wasn't at least loosely based on the Callaway kit, and most of them still use its manifold or a close copy of it.
Any turbo kit you install should be a fairly easy bolt-on, with no significant changes required to engine mounts or other fundamental vehicle components. Once you have it installed, you will have to tune it. Rising rate fuel pressure regulators seem to work only to about 5-7 psi, and even at that level major power gains can be had by substituting a stand-alone engine management system, thanks to improved fuel delivery and timing.
The Digifant system, being derived from the L-Jetronic flapper-box, doesn't tolerate typical naturally aspirated modifications, such as cams, that significantly change airflow/rpm characteristics. However, properly tuned flapper-box systems work well with forced induction at airflow rates up until the flapper is maxed out. Tuning it properly requires access to the software. Digifant software is easy to modify, relative to the latest drive-by-wire systems, but the equipment and expertise required are not inexpensive to acquire. Your best bet, if smog laws in effect in your area permit it, may be to upgrade to a stand-alone engine management system, such as the Electromotive TEC-II, which is used in some of the most successful one-off turbo systems we have seen lately.
Overall, it sounds like you hope you will be able to accomplish something for (nearly) nothing with the turbo kit you have acquired. Experience shows that this is not possible. A good turbo upgrade can be the foundation of a superb car, but doing all the work to get it right is neither easy nor inexpensive. The same is true of naturally aspirated changes. As we pointed out earlier, your Digifant will probably work poorly with a hot cam. Adjustable timing gears, we are told by those who sell them, are frequently used to restore low-end torque lost when a "hot" cam was installed and made the car slower.
The best cams for cars like yours are relatively mild. They add power all around and are typically unresponsive to changes in timing. Larger injectors will only make the ECU's feedback routines work harder to maintain the correct air/fuel ratio. They are generally required only when significant increases in airflow have been achieved--as with forced induction, a displacement increase or radical internal modifications--and must be combined with suitable software reprogramming.
Given the modifications you already have in place, the best results at moderate costs are likely to be with a mild cam, an upgraded chip (be sure the tuner you buy it from understands what other modifications you have, or intend to do) and ensuring that the basic systems are all in top condition. Spark plugs and wires and the distributor cap and rotor should all be fresh, and it may be a good idea to have your fuel injectors cleaned and balanced, given the mileage on your car.


Edit: Added color.
Modified by Cab42 at 1:56 PM 11-17-2004


Modified by Cab42 at 1:57 PM 11-17-2004
 
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