Pistons 1.9 vs 1.6

[toolie72 67 1 Cars]

Building up another engine (just starting) for my 1.9

road car

question- I’ve a set of 1.6 pistons that I could stick on the rods, due to the smaller chamber I’ll get higher compression (head still has its tears on it at moment)

is it worth the trouble? Possible issues?

id like your thoughts on it (clean ones only)

[Thijs_Rallye 87 4 Cars]

It all really depends on what combination you are about to make. I've ran a DFZ (XU9J1) block with shallow bowled pistons with a D6B (XU9JA) head, ECU, dizzy and camshaft, which kept pinking on load changes, even on 98 octane petrol.

 

A few years back I've built a similar engine for our trackday car but with a slightly more aggressive camshaft and also this combination kept pinking on quick load changes. After fitting a vernier pulley and switching to a DKZ (XU9JAZ) ECU I managed to get it under control and goes like stink now :).

 

So long story short, if you expect to gain some power I wouldn't recommend it, unless you are willing to switch do a different camshaft and prepare to lose some low down driveability.

[dcc 855]

My old 8v was 1.9 rods with 1.6 pistons, made good power for afairly cheap upgrade

[petert 588]

I've made a few. You can use either a 1.6 or 1.9 DFZ piston. They're the same thing. CR works out in the high 10's. It just depends on how much the head has been skimmed. I've also used MI16 pistons and rods, which I think is nicer. A third option is what I call an SRi piston. They're a true flat top and were fitted to 1.9L 8V 405's over here. The head with the funny ports. Not sure what the engine code is.

[welshpug 1,661]

xu9j2 i believe was the flat tops, you'd be well into the 12's i guess with them!

 

you shouldn't lose drivability at all with increased compression, but a cam upgrade and a map would be ideal, preferably a map or tps based ecu rather than afm.

[petert 588]

Yes, you'll need a bigger bump stick, along with modified advance curve.

[DamirGTI 342]

I did this on my daily 205 years ago , with the CR ranging from 11.1 to the 12.3 trough the years , still have that engine but with a little bit moderate CR .

 

Can't speak for just the pistons alone , as i've done the head porting and some other stuff along with the pistons , but yes the CR will be kinda high thus if you do not plan doing something with the ignition id say don't bother as it'll be bad .. it'll pink on std ignition advance curve even on highest octane petrol , so much that you'll need to retard the timing to a degree where you'll lost most of the power/torque from the engine .

 

Modifying ignition timing is a must with this piston combo ! ..  on a budget , modified dizzy works but proper mapped ignition would be best .

 

Performance wise , again can't tell for the pistons alone , with the ignition timing sorted it does "shift lanes" much more quicker than the std. engine .. goes and feels much faster .

 

As with any modification , few of them in the mix is best .. this one , pistons with some head work and cam , properly set up fuel/spark will get you to the 160hp mark without much money spent .

 

D

[toolie72 67 1 Cars]

Cheers

I’ll just leave it on the 1.9 pistons as I know my limits lol

Many thanks for info

[Thijs_Rallye 87 4 Cars]

23 hours ago, petert said:

The head with the funny ports. Not sure what the engine code is.

D6D if I am not mistaken. They have the Mi16 like intake manifold and a very wide and flat torque curve.