I installed variable intake manifold on 1,6TS

As the title says, after a long planning I installed variable intake manifold form 156 1,8TS to 147 1,6TS. Actually I installed it twice. The first try few weeks ago was not successful and after hours of fiddling with the engine I noticed that variable intake uses different vacuum pipe to brake cylinder as the 1,6 manifold. Actually if somebody eventually thinks about this mod, this is the only extra part that is needed (worth 15 EUR).

The installation is not very complicated, except one bolt. You can see it red marked on the B/W picture in attachment. It is almost impossible to reach if you don’t want to strip the cylinder head. You need somebody with slim and long arm to lie on the engine and pass his hand from the throttle body side, under the manifold and side by side with cylinder block to the bolt. It can be touched with a finger from under power steering container, but there is no space for any tool form this side.
Actually all the careful disassembly is about 1-1,5 hours, the assembly is another 1-1,5 hour but this one bolt can take 2-4 hours to unscrew and screw back

The intake length is operated by a solenoid visible on the 3rd picture. It is a simple vacuum piston opened at certain revs and thus operating the manifold. Normally it is in "short" position, when you connect +12V to the solenoid pins it opens lets vacuum pressure on the piston and switches the manifold to "long" position. 1,8 and 2,0 TS operate this way:
idle - 2800 rpm - short
2800 - 5200 rpm - long
5200 – rev. limiter - short
This means you just need to lead +12V to the solenoid between 2800 and 5200 rpm. To do this I purchased a special rpm based switch.
RPM Activated Switches, PN 8950, PN 8956, PN 8957
However I didn’t manage to connect it yet, it requires connection to negative coil terminal but it doesn’t work for me. It seems to expect central coil pack with distributor for all cylinders (my guess). However Alfa has separate coils for each cylinder and it seems it can’t work with this signal (1/4 of the expected impulses???). I am in contact with MSD to solve this.

If you have any suggestion how to make/buy some circuit to operate the solenoid (connect it to 12V between 2800-5200 revs) please let me know. Any help is much appreciated!!!


Results so far (switching not working yet):
Car feels very different. It has much more torque between 1500 - 3000 rpm. It amazed me, but I can feel more power gain as after the remap. Between 3000 - 5500 I can’t comment anything. I don’t think I gained something but I would be very careful to comment any torque loss. I drove the car only for 30 km so far, but in the middle range it feels unchanged. In the range 6000-7000 there is a dramatic change. It always revved nicely, but what I can feel now surprises me. I have to pay attention not to hit rev limiter all the times. It pulls from 6500-7000 very strongly even in 4th gear what was not so natural before.
Car seems to breathe more easily. The new intake plenum has much larger volume. Actually the plenum intake after the throttle has about 25 percent larger diameter. I forgot to take pictures side by side, but 1,6 manifold is really restricted with its intake diameter. The ports to the cylinders alone are the same size.
Engine note has changed a lot as well, it sounds different, but I can’t describe it precisely where the change lies. Except some resonation in the exhaust (???) I started to hear around 3000 rpm

I am very impressed by the change, even though the switching doesn’t work yet. I don’t think that the manifold alone would have so big effect on a stock car, but as I have it custom remapped, custom exhaust manifold and removed pre-cats I think that only now my mods are starting to work together.

I hope that in 1-2 months I will have solved the switching problem and will have fitted my 200 cell racing cat with custom stainless steel center part of exhaust (delayed because money issue, but parts already arrived ).

hmm i see how that bolt could be 'tricky'...

glad ya got it sorted and pleased you like the results, i wish i could suggest how to wire the switch up... im not to sure tbh tho. how does it work, does it take the signal from the rpm sensor? if thats the case could you not just drop the neutral onto a grounding point somewhere? would be lovely to get it to switch!!

Originally Posted by marko

hmm i see how that bolt could be 'tricky'...

glad ya got it sorted and pleased you like the results, i wish i could suggest how to wire the switch up... im not to sure tbh tho. how does it work, does it take the signal from the rpm sensor? if thats the case could you not just drop the neutral onto a grounding point somewhere? would be lovely to get it to switch!!

The switch should be connected to ignition coil. I think it "counts" how often the spark plugs fires and calculates the RPM. The switch can be adjusted to work with 8-6-4 cylinder engines. I adjusted it for 4 cylinder engines, but I think it expects one single coil for all cylinders (giving 4 fires in 2 crank rotations). When I connected it to single cylinder coil, it can sense only 1/4 of it (1 fire in 2 crank rotations). I am awaiting email from manufacturer....

Good job man. Let us know how it performs over the next few weeks

From experience of other manufacturers, one coil per cylinder type ignition systems are 'wasted spark'. i.e coils 1 and 4 fire as one pair and cylinders 2 and 3 fire as a second pair.

This means you get each coil firing once every engine revolution. eg cyl 1 fires at top of compression stroke and cyl 4 fires at the same time but at the top of the exhaust stroke.

If your rpm switches are programmable try doubling your rpm thresholds and program these values, this should account for the difference between single coil and 4 coil systems.

I would have expect your device to give a reading of 1000 rpm when the engine is doing 4000 rpm if it is only reading one coil for example. So is it not possible to divide the revs by 4 and then set the switch to activate at that 'false' rpm...example switch to activate at 4000 rpm then set device to 1000 rpm....

Originally Posted by samdawes

If your rpm switches are programmable try doubling your rpm thresholds and program these values, this should account for the difference between single coil and 4 coil systems.

Unfortunately, it is not programable. Only three things can be changed on the switch. If it is on 4-6-8 cylinder engine, rpm to turn on, rpm to turn off. This is altered via special "jumpers", like on PC. For example to turn it off in 5k I have to plug in the "jumper" for 5k. They are probably only some resistors pre-set by the manufacturer.

Originally Posted by Stori

I would have expect your device to give a reading of 1000 rpm when the engine is doing 4000 rpm if it is only reading one coil for example. So is it not possible to divide the revs by 4 and then set the switch to activate at that 'false' rpm...example switch to activate at 4000 rpm then set device to 1000 rpm....

I thought about this but cant do. Please see the reply above how the swith works. I purchased sets of jumpers to swith it on in the range 1-3k and to swith of in the range 5-6k rpm. If divided by 4 it means I could swith on in 250-750 rpm range and off in 1250-1500 rpm range