oversize pistons Options

[bam914]

I was looking through the Tech Specs book and saw that they list .5mm and 1mm oversized pistons for the 1.7 engine. Has anyone ever seen these pistons or have any? Or where to get some. Just curious.

Blake

[Jeff Bonanno]

Hi Blake and welcome to the board. There are a lot of options for pistons and cylinders. Do you have intentions of running improved fuel injection and ignition timing? I think many people here would suggest larger displacement such as 94mm or 96mm p/c. If you are running stock 1.7 d-jet, you will have to have your MPS tested and recalibrated.

respected engine builders on this board suggests taking 2.0 cylinders and overboring them to 96mm to receive KB (or other) pistons. this potentially represents other work such as checking and setting your compression ratio and valve geometry. keep asking questions here and you will find your answers.

jbb

[bam914]

I know all about the options on big bore pistons. I am planning on building a 914 for SCCA and I can use .040" pistons. And since just about every set of 1.7 pistons I have are worn out, I thought about getting new pistons. When I saw the overbore in the Tech book I said thats what I need. But I have never seen them or saw them for sale.

Blake

[Walter]

AFAIK, there are indeed no type 4 specific 90,5mm or 91,0 mm pistons available anymore.
As an alternative, you must have also thought of the 90,5 type1 pistons. Very cheap, forged (sort of) and easy to get hold of. It just requires rebushing to 22mm piston pin diameter of your rods, but that should be easy for most shops.

greatings,
Walter

[davep]

I would ask your VW dealer since they were a standard overbore part. The .040" equals the 1mm, so the rules permit the largest factory standard overbore.

[Brett W]

Blake
what Class are you interested in that would benefit you from running a 1.7. FP makes no differentiation between the 1.7-1.8. Although there are some gains to be had by by running a smaller motor. Unfortunately SCCA allows a max overbore of .040 so whether or not the factory manuals list an over bore or not really makes no difference.

[davep]

part # for pistons depends on engine serial #, basically a W series or an EA series.

022.107.119 is a piston
(H) for the later series
001 weight group
003 weight group

021.198.179 set of 91mm rings

[bam914]

Brett, I sold all my FP engine and trans stuff. I am thinking of another lesser class. Trying to find out how much hp I can get out of a 1.7 with stock FI intake, programable FI, possible .040" and some other little mods.

Blake

[Joe Ricard]

If I read the rules correctly. all 914/4 are in C stock no matter 1.7 1.8 or 2.0L So It would only make sense to go to 2.0L Springs tires sway bars and interior put me in SM-2 Oh and the cam.

[Brett W]

Are you planning on using your old FP chassis? I wouldn't bother as I doubt you can get more than maybe 95 out of a stock cam, stock injection 1.7. The over bore really won't help in my opinion.

[bam914]

I sold that chassis 6 yrs ago. Thats why I am looking for a new tub .I am not building and autocross car. I am thinking of building and ITC 914. They are moving the 1.7 out of ITB and putting in C. I want to see what I can get out of the engine before I build it. If I get what I want then I will build it. I am hoping for over a 100hp at the crank. We shall see what happens.

Blake

[Brett W]

Under IT rules you are pretty much locked down as far as internal mods. Unfortunately you can't get much compression with the stock stroke and factory pistons. Though you could throw an illegal cam in with some extra fast ramps and different lobe centers but with the limited airflow through the stock heads, that will really put the pinch on you. Although you could hide a Kit Carson unit inside the factory box, thus covering up the camshaft and providing a little more power and drivability.

Good luck.

[bam914]

You are allowed to raise the compression .5. So I could run 8.7, I cc'ed a 1.7 and I came up with 7.8. So there is alittle improvement there. I have increased the head flow 10% on the intake and exhaust and the head is legal. In IT now you can have any ECU as long as it fits the factory housing and you do not modify the harness. I think I have that under control. Now I just need to get all the parts and get it running.

Blake