Turbo BS Thread

What base spring pressure does your kit have?

How strong are you? "What I wanted to ask was if it anyone knows if you can tighten it too much, if there's such a thing."

 

Time to upgrade to an EBC?

 

7 psi springs.

But I've been overboosting with my y-pipe. Up to 10psi was stated as acceptable by Mat. But that's stretching the limits of the stock fuel system.

 

Maybe try putting ~5psi springs in.

Or choke the exhaust. You could cut a thin plate of steel and put a smaller hole in it to restrict exhaust flow. Example 3" exhaust but only hoke saw a 2.5" hole. Then sandwich it between the exhaust flanges.

 

I have 4.5psi springs sitting in the garage that would be a PITA to put in lol

If I do anything exhaust related, I think I'm more likely to say fuck it and reinstall the OEM y-pipe

 

?remove boost controller?

 

If I do that, I'll definitely be seeing 10+ like I used to. Lol

 

I thought you have 7psi spring?

 

My aftermarket y-pipe allows for additional flow and I overboost as a result.

So if I went back to the OEM y-pipe, then the boost controller coming out would be a solution, although probably unnecessary because the OEM y-pipe would fix the issue on it's own

 

I'd swap those PITA springs in then haha

 

Just giving options.

Putting on that stock Y pipe sounds like the solution.

 

Actually I might be g2g.

I just went for a test drive. 91°F ambient temp. Aircon blasting. Consistently maxed out at 6.5-7psi in gears 2-6 (I never try for heavy boost in 1st, not enough rpm range or traction lol). Only once did I overboost, when in 3rd at like 4k rpm and floored it, spiked to 9 but quickly tapered down. When it starts getting colder I may see some slightly higher boost pressures so I'll leave it there, I'm happy.

Also, it felt like it pulled significantly stronger. I can only assume that by targeting a boost pressure above the fuel wall for the stock fuel system, that it was struggling to keep up and I was likely losing high rpm power. In the ~3700-4k rpm range I'd have a drop in power, like it wouldn't quite stumble but it would definitely drip off quickly before catching itself and resuming. Not anymore. Felt very strong through the whole rpm band, took it up to 4500 several times and it just feels stronger and smoother overall throughout the tach.

Perfect example of how targeting your max possible boost pressure may not always yield the best results.

Will continue to monitor long term.

 

A boost controller, can only raise the boost over spring pressure. Not lower it. Removing it should always put you back to base spring pressure. Unless there is some sort of strange problem.

 

Idk. Mat had said that it would be expected for me to overboost with the y-pipe.

Regardless, it's appearing to be under control now so, should be g2g.

This morning in 72°F ambient temp, no aircon on, I consistently maxed at 7psi. Hit 8 once in 4th but it wouldn't do it again, so I'm thinking it's fine.

When winter sets in, I guess I won't be surprised if I overboost but that's not unheard of with cold air.

 

Marc, some of what you say is of concern. If fuel pressure drops off while at high rpm and boost, then you are quickly (instantly) headed for detonation. In high boost, rich fuel mixture is used to control detonation (richer mixture is less prone to detonation). If your power dropping off is from fuel starvation, this is of concern. Detonation is destructive, especially at high RPM/load.

Not sure of your experience: Are you familiar with the sound of detonation/pinging/knocking? Sort of a cackling sound. Have you been hearing this?

Another thing that might explain, is that these engines have knock control systems, and if it retains full authority with the turbo, it would retard timing at the instant of sensing any knock. This could explain the lack of power, as being the Knock systems reaction to starving for fuel. The knock sensor may react so quickly that you don't hear the detonation, but the timing retard response would definitely reduce power. Then is my understanding that these engines creep the timing back in slowly, to provide better performance/economy. This is why these trucks in stock form, are able to take advantage of higher octane fuel, by regularly creeping up timing till it detects pinging, then backing off, but high octane is also not necessary. My truck definitely runs better on 91 plus than on 87.

I asked Matt some time ago, if the factory knock protection is still completely active with the turbo, but it went without answer. I am interested, because I would consider installing a knock retard Add-on system, for piece of mind, as protection from fuel pressure drop, or a tank of bad gas, especially if running higher boost. If the knock control is fully functioning, and has ample bandwidth to protect, even with the turbo, that is a very good safeguard.

If you are not already aware, BEWARE of pinging/knocking while under load. The tendency to ping increases with load and heat. My professor described it as having such high pressure points, that it is the same as taking a ball peen hammer to your pistons, but with the addition of extreme combustion pressures and heat.

 

I haven't heard any detonation/pinging, although I also stopped actively listening for it some months ago once I felt comfortable that the truck was performing well.

I am familiar with the presence of the knock control system on our 3GT's since it's the reason the tunes offered by OV and myself and others can adjust for octane and would hope/assume it was retained for the turbo tune. Seems like it'd be a waste and foolish to disable it somehow.

For what it's worth, that 3700-4k rpm range is very high for me, I rarely go above 3k in normal driving in 3rd gear or higher. And like I said, that dip in power was when targeting 9psi. Now that I've backed it down, I haven't experienced it further, just pulls nice and strong through there when I tested.

The 6-7psi fuel wall was well noted in R&D by Mat and so I knew from the start that when I was hitting 9-10 that I was pushing the limits of the stock fuel system, even though Mat had told me that everything looked good. So in a way I'm happier that I've backed it down to base pressure for some security and piece of mind. And if I had to still be fearful of 6.5-7psi, well I'd be better off selling the truck.

I'm not surprised you didn't get an answer to your question, he never replies to my emails either lol

 

So the last two mornings I've observed a boost pressure spike upon first WOT that quickly tapers down, and then doesn't happen afterwards again, can't replicate it.

First WOT in 4-6th gear (just one of those gears, not all) will result in a spike to 8-9psi and then quickly taper down to 7, and that's it. Can't be replicated. Yesterday was 72°F, this morning was 67°, both around 0630 so fairly earlier in the day, nice comfortable weather. Idk what this behavior is indicative of but just seems weird. Not to mention I'll be more likely to be overboosting anyway when the really cold weather sets in.

As a result, I may just say fuck it and swap the y-pipe back to stock anyway. This y-pipe just isn't worth it in the big picture Lol.

 

@mZiggy
Pics of the turbo kit and wastegate location?

 

Don't have any good pictures really, tight fit and the wastegates are down lower near-ish the tops of the shock mounts, basically on the other side of the fender liner.

Wastegate actuator arms have free range of travel. And they're not too tight, they got checked when I was having my initial overboosting issue months ago.

 

So with aftermarket y pipe without boost controller you were hitting 10+ psi?

With boost controller you're hitting 7 but sometimes spikes?

What boost gauge do you have?

Do you have a wideband?