Project Potential... variable vane turbo on 1.6l

[fspGTD]

I got the wastegate mounted, and the without any wastegate exhaust installed, turned the fueling back up to stock 1.6lTD specs and took it for a first test drive yesterday.  Pics of the wastegate install are to come later.  

It looks like the wastegate is opening at 8 psi and regulating the boost solidly in the area of 8-8.5psi.  With the fueling turned back up, the car is performing really well.  Actually where I have the VNT adjustment set, I think the vanes are opening completely just below the 8 psi pressure where the wastegate is opening, so I think it is a great match.  Upping the boost a little bit would beef up the on-boost HP even more, but as is, it is really fun to drive and has a usable, meaty and broad powerband.  Although it was wet out during yesterday's test, I had to regulate the power in 2nd gear pretty severely to avoid wheelspin when the boost came on!  :twisted:

Yesterday I also headed out on the freeway to do some high speed testing.  Cruising steady on the freeway, the boost would sit around 4 psi or a little higher depending on speed and load.  It seemed almost as soon as I mashed the accelerator pedal down, the boost would quickly rise to 8-8.5 psi and was kept there with little creep and no overshoot.  I decided to see what the peak EGTs looked like so in a high speed 70mph zone, I floored it and watched the pre-turbine EGT gauge readout.  The EGTs just kept climbing, although they really slowed down when the temps got high.  I didn't count how long I tested, but it seemed like I had floored it for quite a while... when the EGTs got up to 1400 deg. F (and still climbing), I backed off.  Without the piston cooling oil jets, I don't need or want it to get any higher than that - I will probably back off the fueling a touch to keep it safer (and maybe up the boost a little to compensate?)  And by the way after running it hard like that, probably because the engine was hot, the oil pressure warning light and buzzer would intermittently come on when the RPMs dropped low, like during a shift.  After some easy driving to let the engine cool off, I found the oil light and buzzer went out for good.

When the wastegate opened, it just made the engine sound change to be a bit more "rattly", but overall it was not very much louder.  In fact I found you had to listen very intently to tell if the wastegate was open venting exhaust gasses or not, and I found it easier to tell it was working by just watching the boost gauge instead.  (The behavior of the boost gauge is definitely different with the wastegate installed!) I was surprised how quiet the direct atmosphere wastegate vent was.  After the test session, I found a evidence of the wastegate venting exhaust by a little bit of soot deposited on the firewall, but luckily, nothing else.

[TDIMeister]

A little extra boost on the same fuelling will reduce the EGT.

[2383 GTD]

A little extra boost on the same fuelling will reduce the EGT.

Run more boost!    Did you fit a proper FMIC on that car yet?

You will find that with increased fuelling, the WG will get louder and louder.  A few months ago it was decently loud on my car, but now with a few extra pump mods, the WG sounds like a jza-80 Supra on the highway.  It is not really annoying as it only really opens when you are really on it.  

An interesting detail is I can "hear" how much fuelling I am getting by the intensity of the WG's sound pressure level.  On cool or cold nights (rare anymore) the WG would be quite a bit louder, than say on a hot day after a semi long trip with hot fuel temps (lower fuel density).  Certainly I am losing some mass flow from greater air temps, but with the >4" thick FMIC I am using now, post IC temps never stray far from ambient.  In addition, after the massive FMIC install, the WG sound level increased dramatically as well... an indication of far better mass flow given the same boost  :twisted:

[rackley]

Here's a quick link to the specs for AeroDuct:

http://www.hrpworld.com/index.cfm?form_prod_id=310_3171&action=product

It says it's good for up to 550*F.

[fspGTD]

Pics!
Wastegate mounting adapter flange:


...installed:


-Wastegate air control-
Since the wastegate flows air to cool itself down, as recommended in the instructions provided, I used a 1/4" hose from the intake manifold.  I decided sharing the small vacuum line that was used by the VNT controller, boost gauge, and LDA device would not be adequate.  I decided to tap into the boss on the 1.6lTD intake manifold "El", and used one of the banjo fittings that came with the wastegate.  By filing the boss surface flat, it would give a good sealing surface for the crushwasher.  The banjo bolt required specialized M10x1.0mm threads however.  I found a pressure plate to crankshaft bolt had the same threads, and was able to convert one into a tap:

I hacksawed a couple slots into the end of the bolt (to give thread-cutting edges as well as make a space for the shavings to collect), and then to give the tap a more conical profile to help it get started easier and make it go in square, I pinched the four wedge-shaped pieces together with vice grips, following up with a thread file to clean up the threads afterwards.  Going into the relatively soft aluminum, it worked quite well!

Wastegate air controls completed:


And in this shot you can see how the wastegate mounts with the adapter and also its air control hooked up:


I also found and fixed a fuel leak coming out of the input shaft by replacing the o-ring inside.  When I had the governor cover off, I replaced the intermediate governor spring with a shim.  The idea is to keep the main governor spring revv limiter working at a stock RPM limit, but keep the fuel pumping out at full amount all the way until the revv limiter kicks in.

The wastegate still needs an exhaust.  There is an atmospheric dump tube that was supplied with the wastegate that almost fits!  It might actually work with a little modification.

2383 - That "wastegate sound" load sensor sounds pretty cool!  

I did try upping the boost today by stretching the wastegate spring.  But I found that didn't work, because even after I successfully stretched it a bit, I found it relaxed to its original free height after being coil-bound.  Adding a dial-a-boost would make it adjustable, but would add unsightly bulk and complexity.  Changing the spring would be the simplest and cleanest way to increase the boost.  Right now it seems I have the .6 bar spring.  I am looking at springs in the range of .8 bar - 1 bar.

Also, recall this is my dad's daily driver.  My main task at hand now is completing what I've started with this project, so dad can get back to driving and enjoying his car again.  Taking on an intercooler install project is tempting, but is not going to happen right now as it would take the car out of commission for quite a while, and also there is not a budget for it at this time.  An intercooler is the obvious future performance upgrade path though!  

TDImeister - there are certainly are times when adding more boost pressure while holding fueling level constant can cool the exhaust gas temps, however, as a rule, I don't think it is necessarily true.  For example, if fueling was already richened beyind the smoke point, extra boost pressure may result in more fuel being combusted, which would release more energy and heat into the combustion chamber than the extra air mass could cool.

Also, even if the engine is running lean and efficient, doesn't it still depend on some other factors?  It seems especially for a motor that is non-intercooled and also where the turbocharger was approaching an inefficient operating area, that the added heat from additional pre-turbine backpressure and intake air temperature from the extra boost pressure could more than offset the cooling effect of the extra air mass.

[deepmud]

even tho' you have added a lot of extra fuel, adding boost will cool it. I had the 1.9td running 1300 at 8 psi. I installed a bleeder on the wastegate line, and adjusted to 12 psi. Max egt droppr to 1100, and it takes longer to get that hot, AND it makes MORE power, because it's burning the fuel more completely. Next , it's intercooled. Acutally, next it gets driveshafts and brakes and stuff, but the next performance mod is the intercooler

[2383 GTD]

Everything looks great Jake.  Depending on what boost level you want to run, I would suggest a spring that is rated ~3 lbs less than what you would like to run, and your favorite boost controller.  The controller can be a simple ball and spring type, or any of the electronic controllers.  Yes, they all work well, and yes they make a difference.

On one of my cars, I have a Tial 46mm that had 2 springs in it from the factory; a 1 bar and 0.3 bar springs respectively.  I found that I had much better overall control, and more power and tq (read from the dyno), when I removed the .3 bar spring, and ran the 1 bar in conjunction with a boost controller.  The same maximum boost level was maintained before and after for reference.  This same technique has also been observed with my diesel which also runs an external gate, as well as every other car I've tuned  

[TDIMeister]

TDImeister - there are certainly are times when adding more boost pressure while holding fueling level constant can cool the exhaust gas temps, however, as a rule, I don't think it is necessarily true.  For example, if fueling was already richened beyind the smoke point, extra boost pressure may result in more fuel being combusted, which would release more energy and heat into the combustion chamber than the extra air mass could cool.

If you're teetering on either side of the stoichiometric fuel air mixture, then that statement would be correct.  In this case, peak combustion temperature occurs just slightly on the rich side of stoichiometric, which not coincidentally is where maximum power is made.  However, this is a gasser paradigm, because even when operating at the smoke limit, Diesels are fuelled much leaner than stoichiometric overall.  And even at the smoke limit, the A/F ratio in a Diesel might exceed 18:1 or more (stoichiometric A/F mixture for Diesel fuel is very close to gasoline at ~14.5:1), and combustion efficiency is at a very high level -- over 90% -- so in the bigger scheme of things there's not much "heat" to be gained by, say, burning the addditional 10% of the uncombusted fuel.  A plot of flame temperature versus A/F ratios (which is largely indenpendent of the fuel used), shows a very similar bell-shaped pattern, with the peak just slightly rich of stoic and rapidly falling off on either side.

Lean mixtures do not increase peak temperatures as much as they cause end-of-cycle temperatures (i.e. EGT) to be increased because of the slower rate of combustion.  Again, however, this is generally a gasser paradigm.  Diesel EGTs don't spike up when idling, when it's operating on a 100:1 A/F mixture.

The key thing here is that increased boost increases the charge air mass.  The added mass, even though it goes unreacted with the lean fuel mixture, acts as a diluent.  It is easy to illustrate the effects of increased charge air mass on temperature for a fixed heat input via the First Law of Thermodynamics:

Q = mC(ΔT)

If the energy input (Q) is held fixed (i.e. constant fuelling), and charge air mass m is increased, ΔT must be reduced to balance the equation because the specific heat capacity C is relatively constant for the purposes of the simple analysis.

[rackley]

But the catch is that the energy input is not held constant.  The temperature of the air mass itself increases because 1) the gas is compressed (ideal gas law, Pressure*Volume=nRT where R = universal gas constant = 8.3145 J/mol K, n=number of moles, and T=absolute temperature) and 2) the turbo is approaching the limits of it's efficency envelope.

Ray

[TDIMeister]

But the catch is that the energy input is not held constant.

To the extent of the limits of reasonable simplifications, it is, providing the fuelling is held constant.  An increase in temperature due to the greater compression by the turbocharger is not accounted for in a First Law analysis as a heat input.  For sure, the temperature and pressure at the end of the compression stroke is higher as a result of higher boost pressure.  But this is not a heat input in a thermodynamic sense.

The temperature of the air mass itself increases because 1) the gas is compressed (ideal gas law, Pressure*Volume=nRT where R = universal gas constant = 8.3145 J/mol K, n=number of moles, and T=absolute temperature)

Actually, during the compression process, the state of the air follows (T2/T1) = (P2/P1)^[(k-1)/k] = (V1/V2)^(k-1) for an ideal adiabatic case, where k is replaced by the polytropic exponent n for a non-adiabatic process. where k > n  :wink:

2) the turbo is approaching the limits of it's efficency envelope.

Actually, it can be shown that a VNT15 operating at 8 PSI of boost (PR = ~1.5) and air flow of about 9-10 lb/min. (4.2 kg/min) -- to simulate the VE of a 1.6L engine @ 4000 RPM or so -- is actually not operating at the peak efficiency island.  This turbo has tons of head room for a 1.6L application that would run double the boost of what Jake is currently running, to 6000 RPM.  That's why I have to laugh at people who want to put even bigger turbos into a 1.6

[TDIMeister]

Jake, I think 12 PSI is a nice number to try  Let's see what the EGT numbers show then.

[fspGTD]

TDIMeister - Actually I agree with that if I were to modestly increase the boost pressure on the Rabbit VNT, that it might cool down the EGTs.  In fact I found from experiementation on my GTD Autocrosser 1.6lTD rabbit (with stock turbo) that increasing the boost pressure cooled the EGTs, although that vehicle had an nice, efficient intercooler, which I found helped cool the on-boost EGTs by a great deal - more than 100 deg. F cooler at 14 psi.

Even a 100% efficient compressor as it compresses air will still add heat to the intake air.  Without an intercooler to get rid of it, the added temperature will consequently "linger" inside the engine through the intake, compression, and power strokes.

And the power to compress the air comes from a pressure drop across the turbine.  Additional pre-turbine backpressure means additional pressure and temperature inside the cylinder during the exhaust stroke.  This added temperature and pressure present inside the cylinder during the exhaust stroke cannot be removed even by the most perfect intercooler.

[TDIMeister]

Jake, you're correct.

I was not aware that this car you're working on is not intercooled.  My bad.  Certainly adding an intercooler alone could account for a 100+ degree EGT reduction even on modest boost levels.

Regarding the boost being generated via a pressure-drop across the turbine, corresponding to an increased exhaust manifold backpressure, you are correct again, but I would just add that the relationship is not 1:1, but it can be shown that it is a function of the total efficiency of the turbocharger, and on an SAE paper on the development of the TDI engine equipped with the VNT15 turbo, it is said that in certain operating conditions, the boost pressure actually exceeds back pressure.

If the turbocharger can be made to operate at a more efficient point, then the boost/backpressure balance becomes more favourable.  Currently I plot the best efficiency point for your engine's operating parameters at around 70% (which is still pretty good by most accounts).  Running at a higher efficiency point of, say, 74 or 76% will result in an increase in the density ratio in greater proportion to the pressure ratio, and adding a high-effectiveness intercooler will provide even greater benefits in reducing thermal stresses and EGTs.

[fspGTD]

OK guys - I've got a new project update!  I finished installing the pro-vent and the wastegate atmosphere dump tube.  So all the basic pieces are now done.  It is complete!  But might there be in store for the future some more high-po tweaks to this vehicle?  :shock:  We'll have to wait and see!

wastegate dump tube:


installed:



There is also a pic and some details of the provent install here:
http://www.vwdiesel.net/phpBB/viewtopic.php?t=1490&start=24

Driving the car, it seems transformed for the better after the removal of the governor intermediate spring.  When the RPMs reach a certain point, it seems like the car just keeps pulling without stopping!  It just has this really nice, usable power band!  Dare I say, with the VNT on the IDI diesel combined with the intermediate spring removal governor mod, this seems like the widest powerband of any turbo-diesel I've experienced.  Better than a stock 1.6lTD or VNT TDI or even my lightweight, 6000RPM-revv limited 1.6lTD autocrosser!  The powerband seems great for lazy shifting and is a perfect partner with the 4-speed transmission!

I hope to G-tech the car in the near future!  Will see if I can come up with some power versus RPM plots and/or maybe some acceleration times...

[lord_verminaard]

That's super cool Jake.  Talk about a "happy fathers day" present!  Your Dad's now got himself one sweet ride, a little grocery-getter rabbit with some sleeper suprises!  Any guesses on MPG yet?

And she's running no intercooler, basically stock pump save the govenor mod, and "modest" boost.  So with a tweaked pump, intercooler, more boost... you'd have a tire-melting monster!   Hmmm... :twisted:

Anyone want to make bets on what kind of power it's putting down right now?  

Brendan
84 Scirocco 8v
00 Camaro L36 M49