G-Teched my 1.6TD - Part 2

[malone]

Thanks for the post Jake

Higher RPM in neutral results in a lot more smoke so raising idle won't help.

I've wanted a compression & leak-down test for a while lately, but 935racer has the testers and we haven't had too much time in the shop. 935racer, how about we do it this Saturday?

My engine idles very smoothly, it starts misfiring if you rev it in neutral above 1,100 RPM or as soon as the vehicle accelerates off idle, especially at part-throttle. Despite the smooth idle I guess there still may be improper combustion based on the 300-400 EGT.

Perhaps I should note that I do not have a cold-start pull. I have a 650amp battery and a small gasser starter (transmission is from a 1.8L 8v) but the engine fires to life after 1 or 2 cranks in -4 degree C (24 degree F) weather after sitting overnight. Starts great, but immediately after startup if I hold WOT the engine cannot rev on its own, until 10-15 secs later. Perhaps that's another indicator of low compression?

Anyway I just ordered an OEM cold-start pull that fits in my MK3 dashboard. $28.78. Of course it won't be the ultimate solution, but I may just need a little advanced timing.

When 935racer pulled my 1.9 head, he also replaced the thermostat at my request. I don't recall what temp it is, my last thermostat was 87 degrees C (188 F). I'll ask him what the temp rating is, but the temp according to my water temp gauge is 185 degrees usually.

My oil temp gauge is the only gauge that's not functional. I've visted two auto parts shops for fittings for both oil pressure and oil temp sensors on the 1.9TD head, but they didn't have the proper fittings :evil:. I'm going to visit another this Saturday.

If you feel so inclined... now would be a good time to experiment with ceramic coatings on any or all of the aluminum surfaces of the combustion chamber and piston tops.

If that's the case I'll likely wait until I get a temporary daily driver and leave the TD parked until 935racer gets a ceramic coater.

Another thought - if your glow plugs being turned on during idling solved the situation, you might be able to do something to wire them to go on whenever the RPMs dropped below a certain point.

Good idea. I can get one of my friends to build a switch based on the RPM signal coming from the "W" terminal on the alternator. I drive in traffic a lot on a daily basis, will the glow plugs last long? Does it say somewhere how many continous hours they're rated for?

Glow plugs didn't completely cut my smoke, it just reduced it. If the engine is revved in neutral with or without glow plugs, there'll still be a big plume of white smoke. I already failed Aircare (emissions) with the glow plugs active throughout the test. They repeatedly revved the engine pretty high as part of the idle test, but I normally don't do that in traffic.

Coming up:

Compression #s
Leakdown #s
Oil temp #s

[fspGTD]

Knowing that switching the glow plugs on helped the situation I think says a lot - that you are indeed not getting high enough compression temperature.  Why it misses a little above idle but not at idle is mysterious...  Is it just a transitional thing that happens when extra fueling is given to raise the RPMs, or does the missing happen if the RPMs are held at a fixed number a little bit above idle?

I'm pretty sure I noticed once before when I was watching a codriver racing my car at at the start line, they had this habit of revving the motor aggressively up and down a few times and I remember noticing for the first time ever that I thought I heard missing coming out through the exhaust noise when they revved it very quickly and aggressively under no load.  I never heard it except for that condition, so never gave it too much thought through.  But could it be that too much fuel applied too quickly could make the mixture more likely to miss?  I think it's plausible, because if the fuel is turned up more gradually then it has more time to warm up the combustion chambers, but if a load of fuel suddenly gets dumped when the combustion chamber walls didn't have the chance to get warmed up, the extra fuel would take more heat energy from the charge to convert it from liquid to vapor to the point where combustion could be delayed or might not even happen at all.

Could you switch to any thinner of a head gasket or are you already as thin as you can comfortably get?  Employing a few small tricks instead of one big one may very well be your fix here.  Your coolant thermostat OEM temp?

[malone]

Why it misses a little above idle but not at idle is mysterious...  Is it just a transitional thing that happens when extra fueling is given to raise the RPMs, or does the missing happen if the RPMs are held at a fixed number a little bit above idle?

I believe it's a transitional thing. Part throttle @ say 1,500 RPM will misfire, but WOT @ 1,500 RPM won't misfire as much.

So I'm doing WOT constantly in 45 minute bumper-to-bumper traffic (each way) to avoid the excess smoke. Combine that with a 6lb flywheel and a stiff clutch and imagine how much fun that is But with a stock NA pump I'm not accelerating too quickly.

Your coolant thermostat OEM temp?

185 F (85 C)

Could you switch to any thinner of a head gasket or are you already as thin as you can comfortably get?

I recently switched from a 3-hole 1.9TD gasket to a 1-hole 1.9TD gasket and I don't think I can go any thinner. The piston protrusion height is near the max limit of the 1-hole. The 1.9TD head was also decked which may or may not have affected compression.

if a load of fuel suddenly gets dumped when the combustion chamber walls didn't have the chance to get warmed up, the extra fuel would take more heat energy from the charge to convert it from liquid to vapor to the point where combustion could be delayed or might not even happen at all.

Now that's an interesting thought. I don't remember holding at 1,500 RPM in neutral long enough or stable enough until the cylinders are warm and see if it reduces the misfire. To accurately test it I'll raise the idle screw to firmly hold 1,500 RPM and experiment with different idle conditions.

Employing a few small tricks instead of one big one may very well be your fix here.

I think so too. So I suppose I will try the following in particular order:

1) Higher temp thermostat.
2) Look into building an automated glow plug system for low RPM.
3) Airflow restriction (again). I will install the EGR, keep the throttle plate in an almost closed position and actually drive in traffic - see if it makes any bit of difference.
4) Heat the intake air (briefly experiment with heat gun first). I have a hot air rework station that I use to desolder chips in TDI ECUs.. 200 degrees F for intake air is no problem although I would start at lower temps.

[fspGTD]

Malone - one more idea for you, might more one of the more "experimental" ones though...  Switch to injectors with a different time-fuel release profile, IE: experiment with different pilot injection.  They inject a small amount of fuel before the main load to get the fuel burning earlier.  Then the small burning flame helps the big main fuel load get evaporated and more smoothly combusted.  I know stock VW IDI Diesel nozzles are what they call "throttling pintle" nozzles... which employ this feature to some degree by the pintle not opening a large cross section earlier parts of the stroke.  There are some angled flat-cut pintles that can make the pilot injection transition a little more smoothly into the main fuel load.  I don't know if it would work, but flat-cut pintles are to be found on some OEM VW, european-only eco-diesel applications I believe.  The other way to fiddle with the pilot injection feature is to use dual-spring injector holders (which I'm curious if you've already got or if you just have the single springs?)  The first stage has a lower spring rate so the injector snaps open to get the pilot injection going quicker, and then the spring rate increases and the pintle lift slows down when opening more for for the main injection.  Sort of a lot of fussing to test this stuff when there is only a chance it will fix your problem (and could even make matters worse as it is experimental), but you are kind of blazing new territory here with your 1.9 head on 1.6 block and I suppose that's just part of the territory.

On that note, I can't help but wonder haven't anyone else tried a 1.9 head on 1.6 block before?  A while ago I thought Bryson (Dr Diesel) had build such a beast, IRRC.  But oh yeah... I guess your motor is the first to employ the "secret" combustion chamber mod though... right.

On the bright side of things... at least your motor starts right up... and with a gasser starter motor to boot! :shock:  ...and it sounds like when it gets above 2000RPM that it goes pretty well too. :wink:

[malone]

Thanks for bringing the injector/nozzle alternatives to light - that's something I'll strongly consider.

I just got an injector pop-tester last night so I can test some injector variations, a friend in Europe may be able to send a few injector examples. The tester will be a handy tool.

Both sets of injectors (OEM & GTD) that were used in my TD are single-spring.

I wondered the same thing about whether anyone else has tried a 1.9 head on 1.6 block. Erik, 935racer's friend, mentioned trying a 1.9 head on his 1.6 block. I'm curious as to see how it will run, especially without the head deck mod that lowers compression.

But oh yeah... I guess your motor is the first to employ the "secret" combustion chamber mod though... right.

:lol: I know what you mean. It would be nice if everyone on this board will share all their tricks. If I did the head deck mod myself I would have taken pictures of it and posted it here or at least described what was done.

If my head will come off again for a ceramic coating session then I'll ask 935racer for permission to take pictures. If he doesn't allow it then perhaps we should respect his business... but head work is similar to gassers, there are a number of machinists across the nation that know the same tricks. Maybe there's even publically available info on the Internet, I'll see if I can dig up some links.

[fspGTD]

That's fine with me if you guys want to keep it a secret; I didn't mean to imply or request that you should reveal it.  (But of course, common sense is that you might get useful more help in diagnosing your problems if we knew more about your setup.)

I only meant to say that because there is a secret mod involved, you might have differing results from others who have tried 1.9 heads on 1.6 blocks.

[935racer]

Hey guys don't worry its not really that big of a secret. I am actually working on making a detailed post of what exactly I did. The reason I have not posted any pictures or talked about it much yet is because I wanted to make sure it worked and I wanted to get it on a flow bench to show actual results and stuff first but what the heck I'll try and explain it right now. I am not trying to hide stuff from you guys, I really like how we can all share info and tips and tricks on our diesels and I promise to do my part in showing what I have done.


Picture a cam lobe. Now picture a cam lobe and the head of a valve. Half of the cam lobe is round. The valve head is round. If you were to stack the cam lobe on top of the valve and line the bottoms up there would be that funky shape hanging off the end of the valve. Now put that valve back in the head, and carve that weird overlap shape into the deck of the head about .25-.5mm deep.


It might be hard to picture without pictures I'll try and draw something up and to better illustrate. Mark we can do a compression test on saturday.

[andy2]

Malone,What cam do you have in this engine,1.6 or 1.9,Are they different form eachother mabye swaping them is an option  :?:

[DVST8R]

The deck mod probably adds 5cc - 7cc of volume per cylinder. I dont recall if we mesured it. It is used on the PDR race trucks as well as on some gas engine's it was originoly pioneered by a guy in India, he clamied that on a gas motor it made it almost direct drive, no need for a tranny as the torque spread was so good. It definatly is an air monster. This car went from smoking up three lanes of traffic with thick black soot, with his giles pump to no smoke and needing to turn up the fuel a fair bit for just a haze. :shock:

The cam is a custom build, not sure which stage is curently in there though. Dave?

Mark mabey you can draw up a pic of the deck mod? I don't think my paint skills are good enough.  :roll:

[malone]

I thought the cam's stock, unless Dave snuck in a custom cam when he pulled the head recently

Sure I'll draw the diagram of the deck mod. I'm currently at work and won't be home until late tonight though.

*edit: DVST8R has just posted a diagram on the next page

[DVST8R]

Got your PM.

Here is my attempt at Paint, straight up KG style.



The Red circle is the the exhuast valve, the Blue one is the intake valve, the grey area's on either side are the area that has been relived. Of coures in real life they have uniform shape and size, as well as, they have a slightly differn't overall shape, size, ect..., but it will give you guys an idea. As Dave said earlier the relief is about .25mm-.5mm deep.

[935racer]

Yeah thats kind of what it looks like, I'll grab a core head and go at it with a marker so you guys know what I am talking about. The mod gives a huge increase of airflow. You shoulda heard how shocked Giles was when I said I had to turn the fuel screw in a couple turns to just get a haze under boost. Sorry buddy now you gotta build a bigger badder pump :twisted: This isn;t something I would reccomend unless you have a proper electric die grinder and some porting skills. I can't remember the weight but I think I removed over 1lb of aluminum from Marks head.

[malone]

I wish I took a picture during the 2 days my TD lasted (since it was swapped in my MK3) with Giles' stage 4 pump, but this is a fairly accurate representation of my smoke, although it was more dispersed with a downturned exhaust tip:



While driving I couldn't even see 1 feet past my rear windshield as the smoke was battering it.

Now this picture represents my current smoke at same boost since the airflow improvement:



Zip, nada, no grey smoke The GT20 may have contributed to the extra airflow but according to its map it doesn't seem much more efficient than the stock TD turbo, if at all. The difference in smoke & power though is just incredible, thanks to 935racer's headwork.

I think the modified 1.9 head is worth it. We can reduce the low load white/blue smoke to keep the car daily driveable. Like fspGTD said, it's experimental, but we will make it work.

[DVST8R]

Well since Mark's "smoke" picture didn't work, that and I think it's a photochop anyway, if it's the pic I think it is, this will give you an idea of what it was like.


 :twisted:

[andy2]

Sick :twisted: