Tales of turbos, part 3

[Dave Lawson <dlawson@ball.com>]

Hi all,
I have been looking into performance modifications and engines swaps for my 
83 TQC and thought some of you might be interested in what I have found.

>From Ned Ritchey at Intended Acceleration:
I explained to Ned what I was thinking and asked him numerous questions. Ned 
said that the TQC fuel distributor runs out of umph at around 250hp, same 
for the turbo and the intercooler. This was the first limit I have heard due 
to the intercooler. I was originally thinking of an late 89/90 200TQ 
engine(MC engine code) complete with the harness, dual knock sensors and 
engine computer. Ned said that he can't increase the boost pressure on this 
engine as much as he can on the earlier 5000TQ/200TQ engine(also MC engine 
code) with the single knock sensor due to the increased compression ratio of 
the later engine. He said that they make the same power, but the earlier 
engine feels stronger by a 'seat of the pants' evaluation. He recommended to 
go shopping for a late 85 to early 89 5000TQ/200TQ engine. It seems that 
these early MC engines are all the same and have the largest production. He 
also said to be sure to get all the small parts like the wastegate frequency 
valve, carbon canister valve, idle stabilization stuff, etc. All this is 
needed for a correct transplant. He mentioned the MC engine has larger head 
port castings than the stock TQC head, probably due to the increased 
displacement of this engine over the TQC engine. He said the stock 5000TQ 
fuel distributor and injectors can flow enough fuel to make over 320hp.

When asked about cams, he said he has not found a replacement turbo cam 
which he would recommend. The stock cam is very good. He did mention that a 
normally aspirated cam from the 5 cylinder engine from Germany seems to work 
very well in the turbo engine. For the turbo cam, he said to look for one 
with a very small overlap.

His Stage I/II/III computer modifications have the timing and fuel maps 
changed along with the increased boost pressure. I also learned that Audi 
produced a turbo engine with knock sensing ignition which had a solid lifter 
head. He also has John Buffum's racing computer maps available for anyone 
who wants a racing/off-road computer. This computer works with some of the 
engine ancillary equipment removed. He mentioned that the engine wire 
harness would have to be modified, but he also thought that the traces for 
these signals can be cut on the computer PCB. This modification would make 
the computer for off-road only.

For turbos, he said the S4 turbo is good up to around 250hp. Repeating what 
was stated on the net, this turbo was designed to increase low end torque 
and doesn't flow enough air to make more than 250hp. Now I see why the 
tuners offer a new turbo on the 20V turbo upgrade packages which bring these 
engine up to 290hp. He said that correct turbo sizing was very important and 
that you can make or lose 40hp by playing with the turbine sizing. He said 
he won't be able to get anymore RS2 turbos. Scott, you are lucky and got the 
last one. He does carry a turbo sized slightly smaller than the RS2 turbo 
which is still available.

For TQC intercooler upgrades, he mentioned removing the 2nd radiator and 
installing an oversized primary radiator. Have an intercooler fabricated 
which fits across the in front of the timing belt cover of the engine.

As Scott has mentioned, Ned said all you need to get in the 280-300hp range 
is a modified computer, the correct fuel and the correctly sized turbo. 
Exotic cams and intricate head work is not needed. Pretty amazing.

Ned has also installed a 20V turbo engine into a new style coupe for a 
customer. He said the car really goes and is very quick.

>From John Buffums shop:
I have seen TQCs advertised with 'Buffum cams' and was wondering what these 
are. The fellow I talked to at Libra Racing said that they use a mild 
Schrick cam in the rally cars. They don't have any custom cams made or any 
Audi Sport cams. For a stock TQC, you can easily get 200hp with a computer 
mod and cam change. Most of the improvement comes from the computer. He also 
said that they have been running the hydraulic head engines for the last 10 
years in the rally cars and stopped using the solid lifter engines long ago. 
They use a special design K27 turbo on the race engines.

>From Kim Collins at Quattro Sports in the UK:
He said that they haven't seen a performance cam which is much better than 
the stock cam. They stick with the stock cam. Kim has been advertising a 
Treser engine upgrade kit for the MB engine in the 88-89 TQC and asked what 
this consisted of. It has custom Mahle pistons, a custom hybrid turbo 
camshaft and a custom fuel distributor which used parts from the 911 turbo 
fuel distributor to flow more fuel. Supposedly this kit brings an MB engine 
to 300hp. He was asking 1500 pounds for the kit and it has been sold.

>From TAP:
They don't have any camshafts available time.

For information on  turbo sizing, I have three books that I bough from 
Classic Motorbooks a while back which talk turbo sizing and explain what Dan 
and Jim said. Can't remember the titles or authors right now. There was also 
an article in August 1993 Excellence which explained turbo sizing. They even 
had compressor maps for the KKK turbochargers fitted to the 944 turbo and 
the 911 turbo.

All for now.
 -
Dave Lawson  dlawson@ball.com