I am looking into purchasing 94mm Mahle DISHED pistons.. And I find limited info.. If I look at Mahle's on the web I see little or no product#'s. Bus 94mm Dished Pistons I can get for $300.00 and the porsche 914 94mm dished Pistons I can get for anywhere from $700 to $1300.00 They appear exactly the same except maybe the dish's CC which I get conlicting info on too.. 914 stock dish cc is either 15cc or 5cc depending where I look.. Now I am so confused that I would like to be able to identify what I can use and what is really on my car now?? Help...

I think there is a deeper dish in the top of a bus piston to lower the compression ratio. Stock 914 are dished less, "euro" dished less if at all. Why are you limiting yourself to stock 94's? Many owners upgrade at least to euro p's and c's with higher compression or 96mm to increase displacement.

My new heads are getting cc this week but the person whom remaned the headsis telling me the compression ration is over or around 9:1 which i am told is too high by some way to high so I fugiring increasing the compression ratio by any other mods would be counter productive.. If I put 96mm then will I have to have my crank altered too?? lack of ignorance..

Nothing has to be done to your crank for 96mm pistons. There are 2 versions of the 96mm however, one for the 1.7 and 1.8, which has something to do with the wrist pin offset (??) and another set for the 2.0. However, I don't think 96's will solve your high compression situation, you still have to figure deck height etc. and compression chamber volume to calc compression ratio. There are spacers available for the bottom on the cylinder where the cylinder base goes into the case that may be able to adjust for compression ratio. I don't know if 9:1 is too high a ratio as the euro 2L p's & c's have a 8:1 ratio (if set up for that ratio)

I think I got it now.. just gotta wait for my cc measurements.. the main thing i could not figure out was why the huge price difference (in some instances a $1000) for same Pistons different dish.. I mean flats are cheaper than the dished in some cases and then the deeper dished are cheaper than both.. so who the ?? is selling what ?? for how much more ?? why?? I just thought maube I was missing something else because in the end the money won;t matter if I screw up either my heads or pistons..

There are some "you-get-what-you-pay-for" sets. I would buy mine from a reputable source (Raby aircooled technology, AA, pelican, GPR, come to mind). Consider the 96mm as they are "bolt in" and many people, after driving a 914, search for more power so this might save a step.

your making sense.. what is a good 96mm brand??

Most 96mm pistons and cylinders in motors built in the last few years are AA (not Automobile Atlanta).

Are they any good? what kind of horsepower increase is likely?? lets just say form a stock set up to 96mm.. my heads are getting cc'd and i can attribute that later..

If you're running carburetors, it would be best if you were to change the cam and lifters along with changing the pistons to 96mm. If you're running EFI, you need to be aware that significant adjustments will need to be made to the FI system, and choices of effective cams are basically reduced to stock or Jake Raby's special camshaft for EFI. If you replace your existing pistons, be aware that you need to have the rods reconditioned and the new wristpins fitted to the small ends.

The Cap'n

Perfectly stated right there! and thanks capn, going to keep it stock with what I have. I just finished and have not reinstalled yet my entire DJET making my entire FI system either Nos or reconditioned etc form comtrol unit to injectors and all related sensors... I think I will just install my reman heads with appropriate shims done!!

THanks Cap'n foir pointing out that which others do not saves me time and expense.. I owe U 3 times over now!!.. Joe

The Bus pistons have a larger dish which is in large part responsible for their low compression ratio. The US-spec 914 pistons have a smaller dish. Some old European 914 pistons have a dish that's smaller yet, while most of the ones we find now have flat tops.

The Bus pistons are likely cheaper because there are more Buses out there than 2.0 914s that people want to keep the stock displacement and compression ratio on. Also likely because the vehicles they are going into have a "VW" on the front...

--DD

Thanks Dave, It was what I assumed.. Thought was that my heads are cut to a higher compression and maybe that would be a way of lowering it? I do not have any number to work with.. Then I when I found out these pistons pricing difference is so extreme I thought maybe there was something I was missing.. Thank you for confirming it.. Porsche Shops get $130.00 an hour VW shops get $90.00.. Kinda Of a CRUX for the halfbreed.. 914 pistons 1300.00 VW pistons 400.00 diference?? 10cc's.. Thats about $90.00 a Cubic Centimeter!! Following that Math and Marketing.. A 1971 displacement would cost $177,390.00.
VW BUGATI shops get $300.00 an hour same as a Brain Surgeon.. I do not need a brain surgery to figure out what is going on!!