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Boost trouble

I was having trouble with boost pressure on our Evo1, the car was only boosting half way. The time had come to fix it.

I also think the Thema cams have a gentler profile, to allow a

smoother ride than the Delta, but I don't know this for certain.

I am also told by your Foreign Correspondent that I can't just

put the old 16v Delta cylinder head and cams on the Thema block, because the Thema pistons are a bit domed also.


Our Evo runs on the original Delta ECU, I had refitted the old engine's cleaned green injectors and intake equipment. The history of this car is uncertain, but it was fast on the original unit, and seems to have a chip of some kind. The car continues to run well with the Thema engine, but it isn't happy above 5k revs, and it wouldn't overboost.

A few years ago I'd fitted a replacement engine into our Evo1,

a new crate Lancia Thema 16v turbo motor from Germany.


This engine is very similar to the Lancia Delta 16v Evo1's, but there are differences. The cam cover is lower on the rear cam box, and it doesn't have a crank breather pipe fitted. The water pump has a different pulley mounting, and the oil pump pick up pipe needs changing to fit the shallow Delta sump.

These external changes can be simply dealt with, but internally the valves are solid and, I think, a bit bigger than a 16v Delta's.

lancia thema engine

We lived with the car this way for 2 or 3 years, enjoying the reliability of the new engine, but we decided it wasn't quite right. I checked all the engine pipework, the turbo had been rebuilt, and checking the overboost pipework against the workshop diagram I found the small bore pipes were mixed up.

I fitted them correctly and the change was amazing,

the boost needle went off the dial! 

This was very encouraging, but left like this it would burn a hole in the pistons, so something had to be done.

lancia delta evo1

Original Lancia fitment ECU controlled Pierburg overboost valve,

solenoid controlled variable openings operated by electrical impulses. 

lancia delta integrale overboost valve

So I booked the car into Pro-Tec tuning in Preston, as asked I wrote a note of the car's specs and problems, and took the Delta over on our trailer.

I hadn't been to Pro-Tec before, but there were several high performance rally cars inside and out, and the staff gave me confidence.

The workshop is on an estate near a little used 4 lane carriageway, the boys use this to test co2 etc. under real load conditions, I left the little car with them.

lancia integrale on trailer

Pro-Tec Performance are very experienced rally car builders and tuning engineers, I hadn't met the crew before, but they gave me confidence that our Delta was in good hands.

There were some interesting cars in the workshop, our Delta and the other cars would have plenty to talk about alone overnight!

Towards the end of the week I jumped on a bus to Preston

and went to collect the car.

The boys at Pro-Tec had increased the fuel pressure to 3.6bar, this helped the car to keep the power on at 6k,

feeding the green injectors better.

They also found the overboost valve wasn't functioning, the boys said after 20 years it was unlikely any Pierburg valve would still be working. So they fitted a Turbosmart boost control valve, this is a simple valve, which is manually adjustable to give the boost pressure required. They set the boost to 1.2bar, which is the max overboost pressure Lancia have set at the old valve,

so it must be a safe boost level.

I was also worried about the actual Thema unit, there are 2 levels of Thema power, 205bhp and 180bhp. A 225bhp Eprom chip is available for the Thema engine, but I hoped I hadn't bought a lower power unit. The guys said the bhp would be controlled by the ECU, so not to worry. The ECU on our car had been chipped, but they weren't sure what it was, but they were happy enough with this chip's functions.

Here's the boost controller, fitted in place of the old unit.

I picked up the Evo1, and had an interesting wastegate conversation, the Pro-Tec team are very knowledgeable about

our age of cars, about turbos and vehicle electronics generally.


On the run home I found the car to be much better. The changes made at Pro-Tec produced more power, good usable boost pressure, and a good solid power delivery right up to 6k. This is now a seriously fast little Evo, with great drivability.

Pro-Tec would write a new chip if required, but I'm very happy with the present set up, I was also very happy with Pro-Tec's service, and the very modest costs involved.

I write this after a 2000 mile round trip to Italy, the Evo ran well

and was quite economical, fighting off all the competition!

This is the controller, adjustment knob

is locked in place with an Allan screw.

Click on image to visit Turbosmart site

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