Repair-It

There isn't a ton of turbo noise other than air whooshing. I can't hear whistling and that may be because it is not a quiet engine.

kevm14 wrote:Had to pull a TON of spark advance to get it to stop pinging. It's down around 20° under full boost. The knock sensor does seem to respond, because it does pull timing after knock events. The pinging was audible but I got that settled down. This will be a 93-only truck now. It may be that my existing spark map was way too aggressive, and while the engine tolerated it naturally aspirated, with the turbo, it doesn't. I need to look more into this.

I definitely need to look into this. Pulling 17° for 5.5 psi of boost. That's 3° of spark retard per psi of boost! The internet says 2° per psi is conservative...we are over that.

If 20° is really all it needs under 5.5 psi, then I probably have way too much timing in it before boost. Which hasn't seemed to really hurt anything at least.

OR....the timing is more or less correct under atmospheric, but under boost, the engine becomes octane limited because of compression or whatever so I have to pull way more than normal.

kevm14 wrote:Under warmer temps, I will need to tweak the CTS/IAT spark stuff. Basically there are two tables: a CTS/IAT table by temperature that says how much spark to add or subtract depending on the CTS/IAT blend, and the other table says how much CTS or IAT bias you want across the range of air mass flow (grams/sec, calculated). Generally the engine needs more spark advance at lower coolant/intake air temps, and less spark advance at higher coolant/intake air temps. I set it up to use a little less CTS bias at high airflows (or maybe I just thought about it - need to confirm). If the spark is still too much as the weather warms, I can use that table to pull more spark with hotter IATs. These tables can be tricky to get set right, and they are even more critical with a non-intercooled turbo, imo.

I checked last night. I did decrease higher airflow CTS bias down to 75%. Meaning that at higher airlflows, I am telling the ECM that air temp has a 25% influence on air density. It is probably a lot higher than that but this will be a work in progress.

kevm14 wrote:Other notes:
Fuel pressure is tracking perfectly. It's vacuum and boost referenced. The EBL knows about the vacuum reference, which is part of the calibration. In boost, the regulator adds 1 psi of fuel to 1 psi of boost, so the EBL assumes a constant fuel supply. The extra fuel pressure compensates for the extra boost pressure on the injectors. The pressure is ~26 psi at atmospheric, and then tracks right up to 31 psi under full boost (+5 psi), exactly as it should. Fuel system seemed fine, able to handle the pressure and flow. I had to pull fuel out here and there.

Take a second to remark about that - this is an injection system with electronic spark control which this 83 never saw. Not only that, but we are using a heavily modified TBI computer, and a TBI system that was never meant for forced induction, with fuel pressure up to over 30 psi. The stock system is 9-13 psi! And these are the stock injectors from the G20 van.

Oh man I totally spaced - I need to check the logs for fuel injector duty cycle!! I predict it'll peak in the 85-88% range, which is a good safe place to be. I think the stock van injectors are 61 lb/hr. If we assume 13 psi base operating pressure, that is 1.41x the fuel flow of stock. If the van was rated at around 200 hp, then that puts us at 282 hp worth of fuel capacity, with similar duty cycle. Slightly higher max RPM chips away at that margin a little. If we use a 9 psi base operating pressure (GM says 9-13 is good, stock), then we are at 1.7x the fuel flow of stock, or as much as 340 hp of fuel capacity. I would question that as I don't think 9 psi is actually enough, despite what GM says is acceptable. So probably closer to 282 hp worth of capacity. Also remember that we need to run richer than stock (BSFC goes up), so that also hurts us.

All that means the fuel pressure should be good for the time being. I will check DC and see how much headroom it has left before we have to increase fuel pressure.

Trying some intercooler calcs. This doesn't look right but I am posting it here so I have it available.

According to this, the turbo with no intercooler should give us only 3.1% more air density than natural aspiration which clearly isn't true. Needs more work.

kevm14 wrote: Oh man I totally spaced - I need to check the logs for fuel injector duty cycle!! I predict it'll peak in the 85-88% range, which is a good safe place to be. I think the stock van injectors are 61 lb/hr. If we assume 13 psi base operating pressure, that is 1.41x the fuel flow of stock. If the van was rated at around 200 hp, then that puts us at 282 hp worth of fuel capacity, with similar duty cycle. Slightly higher max RPM chips away at that margin a little. If we use a 9 psi base operating pressure (GM says 9-13 is good, stock), then we are at 1.7x the fuel flow of stock, or as much as 340 hp of fuel capacity. I would question that as I don't think 9 psi is actually enough, despite what GM says is acceptable. So probably closer to 282 hp worth of capacity. Also remember that we need to run richer than stock (BSFC goes up), so that also hurts us.

All that means the fuel pressure should be good for the time being. I will check DC and see how much headroom it has left before we have to increase fuel pressure.

Whelp, I think we may have an issue. Injectors may be going static. I will have to deal with this next time I have access to the truck. That, and reducing the deltaMAP AE duration (shorten it).

kevm14 wrote:Oh man I totally spaced - I need to check the logs for fuel injector duty cycle!! I predict it'll peak in the 85-88% range, which is a good safe place to be.

All that means the fuel pressure should be good for the time being. I will check DC and see how much headroom it has left before we have to increase fuel pressure.

So anything over like 4,300 RPM under waste gate boost and the injectors go over 90% DC. In reality, that means he is fine driving the truck because the WOT 1-2 is like 4,500, so it tops out around 92% before shifting. On the WOT 2-3 it's even lower.

However, holding it in 2nd and running it out to 5,000 rpm results in over 100% DC, which is interesting. However, under those conditions, it is also pig rich, like mostly low 10s or even 10.0. So a more fuel can be pulled. I would like to continue doing that next time. However, the right thing to do would be to raise fuel pressure a bit. Certainly it can't take any more boost at this time. Also, if he installed an intercooler, I think that would also be a problem (more dense air, but no additional fuel). Since it is so rich, maybe that would work out OK.

He installed a second fuel pump (designed for TBI so it has an internal relief at around 17 psi) as a lift pump, which pumps into the high pressure pump, also external. This seems to hold pressure, though I need more data. It is way better than before either way.

Intercooler installed. Manual boost controller adventures revealed that method 3 at the below link actually works:
http://mkiv.supras.org.nz/articles/manu ... roller.htm

Here is a nice diagram to see how each port acts against the wastegate diaphragm. It wasn't able to hold boost at all when we tried the "Traditional manual boost controller method." And that may be because that method is made for internal wastegates which work differently than external (the actuation that is). But method 3 does work.

EDIT: See diagram: The principle is fairly straight forward:
After you plumb it all up to match the diagram, you then back the manual boost controller off so it is taken out of the loop (passes all pressure to the wastegate). The vent port is the key here. Using a low pressure regulator, you can dial in how much pressure is on the other side of the wastegate diaphragm which essentially extends the pressure level of the spring to whatever you have the regulator set to. That air pressure helps the spring keep the wastegate closed. Set it to 2 psi and you should get 7 psi boost out of a 5 psi spring. Something like that. You need the bleeder so when pressure drops it has somewhere to go.
The purpose of the manual boost controller, then, is simply to decrease spool time and delay the wastegate from opening until it is basically at your desired boost pressure, rather than begin opening prior to desired boost as it would normally. If you take this out of the loop, you are running Method 2 at the link above.

So they need to be set up precisely but it's not that bad because you just dial the regulator in until you get the boost holding where you want. He did this, and has it at 7 psi now, when it was never able to hold above 5 psi before. Then just slowly dial in the manual boost controller until it begins to spike, then back off a tad. That should be perfect.

A little complicated but it seems to work very well and I look forward to dialing it in to whatever boost we settle on (still thinking 8-10).

Forgot to add...I estimate the intercooler has about a 0.75 psi pressure drop at 5 psi. Not too bad, though I wouldn't want it to be any higher. It'll probably grow to 1 psi by our target boost. Maybe more.

You know what? I need to start making some videos of this thing in action.