Alfa 155Q4

Competition engines and ancillaries - general discussion
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Joined: July 8th, 2011, 8:51 am

Alfa 155Q4

Post by LeoM » July 6th, 2016, 1:35 pm

Hi Everyone,
It's been quite a long time since I've posted anything on here due to pressures of work and various personal things but I thought it was about time I shared what has been going on with the Q4. It's been a great lesson in how not to do things ! I'm an accountant by profession and sometimes my enthusiasm for my hobby gets the better of me.
As a reminder the Q4 is an Alfa 155 which uses the Delta Integrale 16v running gear and uses a similar ECU. I had decided to use the car for sprints and hillclimb and that is where my problems began. A novice in a new and possibly unsuitable car.
Alfa Q4 at Crystal Palace
IMG_1448.JPG (271.07 KiB) Viewed 8446 times
I took advice from the book and from these pages and did a few basic modification:
locked the balancer shafts using Guy's simple methodology
3in stainless exhaust system
hybrid turbo and larger intercooler
larger flow matched injectors
uprated clutch
A rolling road session followed which showed around 300bhp at the flywheel which I understand is the maximum on standard internals. I changed all the hoses and decided to fit a new radiator for peace of mind, but that's where my troubles started.
The car started to suffer from overheating problems and extra ventilation and extra fans didn't help. Last year when my brother was doing a track day the car boiled over (he has no mechanical sympathy and didn't once look at the gauges) which resulted in a blown head gasket.
I took the car apart and reassembled it with a Spesso racing gasket after having the very warped head skimmed. It was down to my own curiosity that I decided to compare the aftermarket radiator to the original and found the core to be 6mm narrower than the original and calculated it therefore had around 25% less cooling capacity. Lesson 1 : Even though something comes from a very reputable supplier and is specific only to that model check before fitting.
The engine was reassembled with a slightly larger aluminium radiator and since then all cooling problems have disappeared. I share the car with my brother and so we tend to do back to back runs when we are competing. The next thing to manifest itself on longer sprints was the poor braking performance which was resolved by fitting Alfa GTA brake calipers.
Things were looking promising this year and our performance was improving but all progress came to a sudden halt when the pipe to the turbo wastegate split. Without control, boost climbed to over 2 bar but not for long. A small misfire was quickly followed by clouds of white smoke. I was initially puzzled but on dismantling found that this small split was the culprit.
Silicon boost hose
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Taking the head off revealed some good fortune. The boost had affected the gasket but there appears to be no other damage.
Deformed Gasket
IMG_3720.JPG (142.73 KiB) Viewed 8446 times
I am in the middle of building the engine back together. The boost hoses will be good old fashion braided rubber made in the UK and not imported far east poor.
I like the car but working on it is complicated and time consuming so I am thinking of a change next year. I would like something simple, normally aspirated and run in road modified class. I have an X1/9 1500 standing around doing nothing or possibly a 124 spider. I'm in the middle of reading through pages of great information on this forum so thanks to you all and especially Guy for keeping it going.


Spider 1969
Posts: 154
Joined: September 22nd, 2013, 7:21 pm

Re: Alfa 155Q4

Post by Spider 1969 » July 6th, 2016, 9:49 pm

Succes with your rebuild and I'm looking forward to your next seasons car.

Posts: 590
Joined: November 26th, 2012, 3:50 pm
Location: Dumfries, Scotland

Re: Alfa 155Q4

Post by Will01 » July 7th, 2016, 12:06 pm

Looks good fun times ahead.
Aslong as you enjoyed yourself when doing the sprints it doesn't matter if it broke. You only know where the weaknesses are when you break it so you can make it better in future. All part of the steep learning curve.

Great to see another Alfa on here

If you have the same Brembo brakes that i do on my GTA, then you will find those brakes pretty awesome and keep on delivering good braking no matter what you do. I have never had fade in my GTA, it is so far the only car to do that which i have owned or driven.
I actually have a set which i will eventually be fitting to my Capri as they work soo well.

Have fun

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Joined: September 28th, 2006, 3:26 pm
Location: Nis, Serbia, Europe (A)

Re: Alfa 155Q4

Post by NickRP » August 4th, 2016, 5:43 am

Hi Leo,

Great Q4 adventures.

Regarding the incident with sliced wastegate actuator hosing - how come the ECU boost based fuel-cut didn't kick-in? This feature is there to prevent engine damage in similar cases.

This feature is a standard software part of the IAW 4W6 units, used in Alfa 155 Q4.

My two cents:
If you had this feature removed by a "chip-tuner", consider changing the chip (and eventually the tuner). There is a way to reprogram the limit, and not totally remove it. If your MAP sensor is in saturation at the full boost, then you should upgrade the MAP sensor, too. But the engine management has to:
  • know at any time what level of boost is present in the intake manifold, and
  • have the means to provide engine protection (e.g. by cutting fuel), should the boost go past a preprogrammed limit.

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