Supercharged Stock 1600 DP

[T-34]

Thats a good point, never thought of that.

I will include it as a benefit in the sales blurb - where do I send the royalties to?

[MarioVelotta]

The way I see it is your $1800/20hp = $90 per hp

[T-34]

Well after playing about with the jetting I've ended up at with everything set up nicely. Bus is pulling nicely all the way through the range with no hesitation at all. Boost is currently in the region of about 5 PSI. I've ordered a multi-groove serpentine kit and will stick with the current 5 PSI until this arrives.

Had an idea about hooking the vac up but need to weld in an additional connection on the manifold. I want to try connecting both the ported vac and manifold vac to the vac can. I'm going to put a non-return valve in the manifold vac line to prevent it from becoming an air leak when there is no boost.

Here's my musings...

I'm figuring that the boost will be much larger than the vac at any given time.

Generally highest vac is at idle or decel - no boost generated in either of these conditions. Typical values are something in region of 18 to 20 inches HG (source - http://www.linnbenton.edu/auto/perform/vacuum.html) This is manifold vacuum, not ported vacuum.

The SVDA gives about 6 degrees advance at 9 inches vacuum. (source - http://www2.cip1.com/ProductDetails.asp ... 43-905-205) I'm not sure about the accuracy of this info as I'm sure I've seen something like 42 degrees overall on my SVDA before which would put the vac advance at about 12 degrees total. But whatever, the actual figure is inconsequential the important aspect is what vac is required.

Now here's the thing - It will take 5 PSI to cancel out 10 inches of vac (the relationship is 1 PSI = 2 Inch HG). So at my 5 PSI of boost I should cancel out up the 9/10 inches of vac stated for the full advance, however, the advance figures stated above are total vac advance - the actual vac level may be higher.

Ported vacuum drops off as the throttle opens - this is why the vac advance also drops off, so at some point the vac will naturally drop off and the additional advance will disappear.

The boost increases as the throttle opens so at some point the port vac and boost will be in equilibrium. Past this point we will be in boost conditions and the vac advance will be cancelled out.

The thing that I cannot seem to find out is the relationship between ported vac and throttle position. This will determine if it is feasible to use the manifold boost signal to counter the ported vacuum signal to cancel out the vac advance.

Biggest worry is exceeding the overall limit of 24 degrees by having both boost and vac at same time. Whilst I can easily hook it up to test I'm not really sure how I can monitor it.

Any ideas?

[Clonebug]

The monitoring problem was the reason I dumped the DVDA distributor on my turbo setup in the first week.

I doubt you will have very much issue with timing retard at only 5 lbs. boost.

Seems the standard is one degree retard for every 3 lbs boost so you would only need to retard 1.5 degrees if at all. A stock distributor would not have any vacuum advance at full throttle or any significant load due to vacuum dropping off when the throttle is opened. If you run the vacuum advance off of anything other than the stock carb for that distributor it will not give you the correct cruise advance anyways.
Any port other than the actual place for the distributor is going to give way to much vacuum at idle since the distributor port has no signal at idle.

You could probably use a 009 set at max 30 degrees advance and then listen for detonation.

My detonation problems didn't rear its ugly head until 11 lbs boost and then only at 180 degree intake temps.

[T-34]

Hmmmn. Maybe I might just get away with just hooking the vac advance back up.

If I have a total of 24 on the mech advance plus 6 on the vac; that's 30 overall - which is a worst case scenario assuming both full boost AND full vac. I can't see that this will happen, I would expect that I might see half and half; so perhaps 27 degrees at 2/3 psi dropping off to 24 at 5psi.

What I have noticed driving around is that I am hardly driving on boost which means that for about 90% of the time the vac advance would be very useful for keeping temps down and improving MPG. (Note that I'm only intending on using the SVDA in it's normal configuration, not the DVDA hooked up as a boost retarder.)

I don't have any way of measuring EGT at the moment. Although previously I have noticed that the only times I have experienced pinking is when the engine is at it's hottest. EGT might be a good secondary / indirect way of checking if the advance is still in under boost.

As an aside, I was chatting to my dad at the weekend about the project, he reminded me about the '53 Riley RME that he restored - this had a dash mounted advance and retard adjustment - basically a cable that advanced and retarded the plate that the points sat on - a similar setup to many old British bikes. Seems like something similar would be pretty useful here.

Think I will try reconnecting the vac tomorrow and seeing what happens.

[T-34]

If you're a tech geek like me, here's something that might be of interest http://home.exetel.com.au/phelum/ign.htm

The ignition timing is controlled by an ATMEL 8535 microcontroller which monitors the pulses from the distributor and produces pulses to drive the ignition coil. The software contains a table of timing offsets and the relevant entry is determined by the RPM and vacuum setting. Adjusting the dial on the box will change the relevant entry when update mode is enabled. The offsets table can be saved to EEPROM.

[T-34]

Damn - most post 1996 cars are 'OBD' compatible - just plug into the cars onboard diagnostics system and all engine management functions are available in real time. How hard can it be to get the ignition timing out of a 1970 VW?

[T-34]

Okay. here's a Q for those running an LM-2.

Can I hook up my LM-2 to the coil signal and data log the coil pulse?

If so all I need to do is add a TDC sensor (typical crank trigger sensor) and also log this as a comparison.

Thoughts??

[MarioVelotta]

You'll need one of these



http://www.innovatemotorsports.com/xcar ... 250&page=2

[T-34]

Cheers Mario.

Does that allow me to log the actual pulse? It's labelled as an RPM clamp.

Mick.

[Steve Arndt]

It detects the ignition event from the secondary wire and gives your data logger a compatible signal to log RPM.

[MarioVelotta]

It detects the ignition event from the secondary wire and gives your data logger a compatible signal to log RPM.

+1

[T-34]

Well I went ahead and hooked up the vac. No issues no pinking drives a bit smoother, temps seemed to be down about 10 degrees.

So been driving about like this with no issues at all until this morning when I filled up. Tank was pretty empty so stopped off on way to work to fill her up. Last time I filled up I had to use 95 as the garage did not have 98 so this time I filled her up with 98 t the Caltex I usually stop at. Paid the cashier and got back in the bus. Then pretty much straight away and all the way to work the bus was coughing and bucking. I stopped half way and hooked up the LM-2 and noticed it seems to be a bit on the rich side 12AFR on progression through to 9AFR on mains. WTF!?

Not really sure what is happening here. Something obviously up with the fuel. Can't see that using premium would make THAT much of a difference.

Bit stumped on this. Don't really want to change jetting again as it was running pretty good. Plus don't want to have to change it back once this tank of fuel has been used.

Any ideas? Anyone else experienced issues like this with fuel?

[MarioVelotta]

Sounds kinda like a clogged air jet. Different fuels find different ways to clean parts, or dislodge junk.

[T-34]

New tank, new filter, new lines, new pump, carby is squeaky clean. Just can't see it myself, unless there was something put in the tank from the bowser, but then there is a filter at the bottom of the tank so it should just end up there or clog up the tank outlet

Feels like I filled up from the paraffin pump instead of the petrol.