Compond Charged VR6

[Compound_VR6 1]

Hello Guys

I'm in the middle of building a Compound change 2.8 12V, using stock engine for now and a Holset H1C turbo and a Eaton E45 Super charger.

The car is going to become and all out drag car, and one got any advice on what internals to use? CAM Shafts ETC.

Thanks

[RBPE 198]

Hmm, not sure that you want to do that - seems like a bad mix!

I take it given they are so small that you are feeding the turbo via the supercharger? In which case how are you going to develop the electro-magnet to disengage the supercharger so it doesn't over spin at high revs or have you worked that out with the pulley system? Not that such a supercharger is any good for the 2.8 anyway as it's too small.

When I worked out these engines being compounded supercharged to turbo many years ago I think I came up with an Eaton M62 disengaged via e-m feeding something like a GTX42 - pretty sure a little H1C will max out very quickly given the volume and density of air it will be ingesting!

Then there's the mapping too - quite a bit of work on the oem but I suppose aftermarkets are simpler and should probably have provisions for extra sensory inputs fairly easily but they cost.

Also, don't forget that the compounding is putting hugely dense air through the engine and without mage knock control tuning and compression work it'll likely rip a stock block to pieces fairly quickly if the mapping isn't spot on.

Plus you can get as much power much simpler and easier with just a turbo kit which is why I decided not to go through it, just over complicated for what I wanted to achieve.

[Compound_VR6 1]

Hello .., Thanks for the reply 

Yes I'm using the Supercharger to feed the turbo to remove the turbo lag.The H1C is not a small turbo. I have seen a similar set-up and it worked very well producing big power and torque. Plus it looks cool and everyone just fit turbo kits.

Also these are parts the i have laying around so why not .... ,

I'm using 1000CC injectors and Porker 996 Wastegate  Mega Squirt Management with will take care of everything there.

Just looking a places for rods pistons cams etc ...

Edited April 1, 2016 by Compound_VR6

[RBPE 198]

No worries sunshine, although I think you're underestimating the task at hand though! Who's done it before with these, any links?

First and foremost, Megasquirt or any aftermarket system for that matter has absolutely no control whatsoever over an electro-magnetic clutch system and would somewhat need to be implemented into the functional logic of how the systems operate, with the ecu being modified accordingly. A difficult task but not impossible but needs a fair bit of custom work to operate well!

That tiny supercharger is also going to be overwhelmed at any decent air flow being the singular compressor and as such, is going to max out it's airflow at fairly low revs, the disengagement of the em pulley system would therefore have to occur quickly/at low revs, maybe even to the point of not being "in boost" or bringing up the compressor speed up to range for what is desired!

Hell, go for it but it's not easy!

Here's a link to how the compound charging works on VAG vehicles I did some years ago if you want to learn it;

http://www.clubgti.com/showthread.php?257472-VW-s-Twincharger-System-Overview

As for the pistons/rods - probably best set you want;

https://store.034motorsport.com/piston-set-je-forged-2-8l-vr6-12v.html

https://store.034motorsport.com/rod-set-pauter-vw-audi-vr6.html

[Compound_VR6 1]

Thanks for the links

I wasn't planning on disengaging the charger

[RBPE 198]

Unlike centrifugal superchargers the roots type (Eatons) are like air pumps as opposed to compressors, as such, they give very good low down torque through minor throttle openings/low revs/flow rates etc, whereas the centri's tend to act similar to turbo's where the flow increases as the revs do.

VW wanted to give the customer power and torque throughout the rev range and as such, the Eaton/Roots types are very good at these low ranges. The idea was to give low end from them until the turbo's turbine side was up to speed for instant driver demand (i.e. instant torque/power we want when we go WOT throughout the rev range). In order to achieve these goals at low revs, the pulley system has to be correctly ratio'd to provide this when the driver demands it.

As it was designed to accommodate instant low end response/torque/hp when needed, the pulley system ratio is calculated so that the supercharger is always spinning quite fast so we have instant response, even from tickover. The only problem with this is that when the revs rise, the speed of the charger rises as it is in line due to the ratio/pulley off the crank. Because the VW 1.4/Eaton M45 superchargers are small - 310cfm at 16,000rpm max flow - and because you need the ratio's sorted so you have this low end response as that is what it is being designed for unlike a turbo to supercharger compound, then it is going to go past it's max rev limits (16k), very early in the rev range.

This means that it is going to explode pretty much! So, there are two options;

1. Change the ratio of the pulley system, basically use a larger pulley - this, in turn will provide very bad response comparatively as the charger takes more time to get up to speed and the engine has all these extra pulleys to deal with at low revs, it's basically the opposite of what we are trying to achieve really...... or,

2. Design an electro magnetic clutch system that can be disengaged once the turbo turbine wheel is up to speed - which is what VW did!

So, "kaboom" or bad low end due to above is what you would experience therefore if you do not have an EM Clutch system!

Edited April 7, 2016 by RBPE