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Audi Tech Letters

Mar 19, 2004

Audi A4 Transplant
If I have a 1996 Audi A4 with the 2.8-liter V6 engine and itis blown, would I be able to replace the 1996 A4 12V engine with a 1999 A4 30-valve engine? Does everything line up right? Would I need to get an engine computer from a 1999 A4 V6?
Karen Zimmer
via the Internet

Karen,
The newer 30V V6 engine is in fact a newer iteration of the 12V V6 that is in your car. The newer engine would simply just bolt right in. As you mentioned, in order to do the swap correctly, you would in fact need the ECU as well as the complete wiring harness. In addition, you would have to make sure that you get all the fueling issues straightened out as well as I do not believe the fuel rails and other fuel injections parts would work correctly.
Joe Lucchio



Audi S4
I am thinking of buying a used Audi S4 Avant. Should I have some concerns? Any special issues I should be wary of?
Rodolfo Castro
via the Internet

Rodolfo,
Assuming you are talking about the B5 Audi S4 Avant, which was produced between 2000 and 2002, which was available with the 2.7T V6 engine and either a 6-speed manual or 5 speed Tiptronic Transmission. These are great vehicles but are subject to several items that should be checked out prior to purchase. You are better off getting as new a version as you can afford since the first model year in the US, the 2000 model year, suffered teething problems, which were subsequently resolved in the later 2001, and 2002 models. These include the oil lines to the turbos that were undersized and resulted in oil starvation and subsequent turbo failure. Throttle body boots that were subject to tears and loss of boost pressure. Weak second gear synchros that resulted in 1-2 shift problems and transmission rebuilds. The diverter valves also were subject to failure, which also resulted in boost and power losses. In the later model years, these parts were redesigned and in most cases these problems were solved. As with any turbocharged car, you should make sure to check all the maintenance records and make sure that the oil was changed every 5,000 miles along with the filter and that a good synthetic of the proper weight, 5-30, 0-30 or 0-40 was used. The other items to check on the car are the front control arm bushings that can wear out prematurely and cause a noticeable squeak in the front end. You should also stay away from cars that have been modified, especially those, which have had ECU modifications, or ichipsi installed, unless the owner has excellent maintenance records and has done other modifications to accommodate the increased boost and horsepower.
Joe Lucchio



Adjustable Hybrid Blow-off Diverter Valve
I drive a 2001 Audi A4 1.8T Quattro tapped with a GIAC performance chip, a CAT-back exhaust and an open air intake system. I was interested in upgrading my stock diverter valve, but wasn't too sure whether to go with a blow-off valve or a diverter valve. There seems to be much debate over which is better. Then I found these, I guess relatively new, Hybrid Adjustable Blow off/Diverter valves, which appear to be a combination of both types of valves. I guess what I'm trying to ask is, what the heck is the difference in all of them? Which is better or worse for the car? And ,while you're at it, how does the hybrid valve work?
Jimmy K.
Drexel Hill, Pennsylvania

Jimmy,
It sounds like you have some good modifications that should result in some nice power gains. Although Iim not sure what open-air intake system you have, the close proximity of the air intake to the turbocharger on the A4is 1.8T could result in more hot air being drawn into the intake resulting in performance losses rather than gains. If you retain the open element intake, at a minimum, make sure that it is shielded as well as it can be from the turbo. If you current stock valve is functioning correctly, an aftermarket Diverter Valve will not give you any additional power gains and neither will a Hybrid Adjustable Blow-off valve. The most cost effective DV upgrade is to use the OEM i710Ni valve which came stock on the TT 225 1.8T or the Bosch 110 valve n both of which are under $50 and can handle additional boost. Aftermarket solutions such as Forgeis 007 valve and Baileyis DV are also good alternatives although at almost three times the price.
The 1.8T diverter or air bypass valve, when operating properly, re-circulates air back into the intake track to maintain the proper air to fuel ratio. A typical blow off valve does not re-circulate the air but vents it into the atmosphere. This is what results in that cool sound that a blow off valve gives. The hybrid blow off valve does both; it re-circulates some air and vents some. The key to getting one to function correctly is to get the right amount of air re-circulated so that the air fuel ratio is correct. The adjustable ones allow you to set the amount of air that is vented. If you are interested in a Hybrid valve due to the enhanced iblow off soundi, check out the GFB Hybrid valve that is sold by New Dimensions (www.ndauto.com). If sound isnit that important n Iid stick with the OEM.
Joe Lucchio



Audi Tech Question
I have a 2002 Audi A4 1.8t quattro. I want to install a 3-inch exhaust all the way back. But I also want to take the cat off and put on a 3-inch test pipe. What possible problems can this cause on my car?
Jack Pribil
via the Internet

Jack,
I donit know of any reason to run such a large exhaust with a stock engine and unless you have significant modifications such as a larger turbo etc. it wonit provide a significant gain in horsepower over a properly designed 2.5icat-back system. In fact you will more than likely loose some low-end torque. As for running a test pipe n the main issue you will have is with the second or post-cat 02 sensor which will give erroneous readings resulting in a constant check engine light as well as poor emissions test results. You are better off running a high flow catalytic converter instead, although they are a little pricey. You will get similar gains to a test pipe, no check engine light and will be able to pass any emissions tests.
Joe Lucchio

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