Hi all, this is my first post here. I've been reading different posts here and seems like there is a good community and lots of good technical info so thought I'd join up.
I don't actually own a G40. I'm currently planning out supercharging a 1.4 AEX from a mk3. From what I've been reading the engine seems very very close to the Polo GT engine, just a slightly larger displacement. As such, I've started looking at how the G40 works since the G40 was a progression from the GT engine. I have a few questions:
Is the G40 head gasket a composite gasket or steel? The AEX gasket is a composite gasket which makes stacking to reduce compression riskier. I'll have to drop the compression from 10:1 in some way as the G40 runs 8:1 and similar turbo or supercharged 1.4 projects (like that Lupo from ed38) have all dropped their compression to 9:1 or 8.5:1.
Following on from this, how IS compression lowered in the G40? Is it gasket spacing or different pistons or how did they do it?
Are the pistons in the G40 forged or are they the same as the GT's pistons?
Finally, what size charge cooler or intercooler does the G40 normally run? I'm thinking of using a mk4 GTI intercooler mounted on the driver's side where there is plenty of room for air flow. I was going to use a mk3 TDI intercooler but that would be mounted under the battery tray and piping would be a nightmare.
For those of you who are interested, I'll be using an Eaton m45 charger and will be running it all on Megasquirt. Hoping to go from the stock 60bhp to 90-100 bhp. Anything more from the initial set up will be a bonus. Not big power by any means, but big power is not my goal. I wanted to do something a bit more involved than 'remove engine A plug in engine B'. I work with sensors, calibration, control systems and such anyway so I thought boosting something and setting up Megasquirt myself would be a good learning project :)
Thank in advance ;D
-Mark
Hi, welcome to the forum.
The AEX from the 6n engine isn't all that similar to the older 86c engines really. For starters it has the combustion chamber in the head instead of the pistons. It also has significantly weaker rods than the older engines. Also strictly speaking, vw made the g40 engine before they made the 3F engine for the GT so if anything, the GT engine is a development of the G40 engine. Really, if you are wanting to do this then the best option is to get a g40 bottom end and then match it to any 86c 1272cc head. It's the pistons in the g40 that lower the CR. G40 uses a composite gasket, also, the AEX engine uses a multilayer metal gasket in my experience, it's a common mod for a G40 engine to swap an AEX gasket onto it to raise the CR very slightly. The gasket on my g40 now is a metal one and I specifically ordered it as an AEX gasket from GSF Car Parts! G40s have cast pistons not forged but they arent the same as GT ones.
In short, instead of spending money getting an AEX engine to be lower CR, just buy a bare g40 bottom end they're not all that hard to find. Or just buy g40 pistons and put them into any 1272cc bottom end.
Megasquirt will be a good project, sounds like you've got some electronics knowledge so that'll help lots. It'll take a lot of work though, don't expect to be able to find base-maps to get a g40 engine up and running, you'll be starting from a blank page pretty much. Not wanting to put you off, as long as you realise it's not just a case of buying a kit, soldering it together and hey-presto and instant running engine then you'll not have any shocks!
Ah I see now. Looks like I got some info wrong before. Thanks for all the input. I'll need to have a more serious think about compression.
You said that some people use AEX gaskets to raise compression, what value do they raise it to?
Yeah I'm expecting a lot of time to go into the tuning side before everything will work. I've been looking through Megasquirts options and a luckily I'm already familiar with a lot of the parameters and sensor operations, just need to figure out how it all comes together ;D
Any info on the charge/inter cooler?
I haven't bothered doing to maths to work out the CR increase of using that HG but it's only a small amount, perhaps raises it to 8.1:1 instead of the standard 8:1?
G40s have a small front mounted intercooler in front of the supercharger as standard, don't know sizes off the top of my head but it's only small, a G-Lader is fairly efficient though and doesn't produce that much heat really. When people fit Eatons they generally put a bigger intercooler on as they'll put more heat into the inlet. Just use what ever you can get your hands on and whatever you can fit as long as it's a reasonable size.