I was talking with a buddie of mine last night about my boost levels with my Quad Commander, and he was saying that they are not that accurate?...nor are any of the digital gauges, minus the new Quadzilla X2 gauge that is supposed to be accurate?

I thought the commander seemed to be right on the money and a great tool, but Im just wondering how accurate it is now, especially with boost levels?

 

To add to the discussion, the buddie I was talking about posts on TDR and on one of the posts, he saw people posting that they were hitting 43psi on the quad commander. I told him when I checked my max psi I was hitting 43psi as well, he said that isnt possible on a stock turbo and head studs?

 

I have no idea how that could NOT be possible. He needs to explain why that isn't possible. Lots of people hitting 40+ psi ona stock turbo. I'm not saying it is a good thing....just saying it is surprisingly easy to do. It does not take a ton of extra fuel to seriously overspeed a stock turbo to 43 psi. 43 psi is easy to hit. Head studs have nothing to do with your turbo building boost. They only serve to prolong the life of a head gasket by more evenly holding the head down tight to the block. And 43 psi does not create enough cylinder pressure to even cause stock head bolts have a problem. Your Smarty/Quad Race stack will have more than enough additional fueling to hit 43 psi.

Can your buddy explain why he doesn't think the boost reading is accurate or is he just repeating something he heard from someone else?

 

Let me clarify,
I personally feel and know that with the Smarty/Quad stack that you can make that kind of boost. I'm also pretty sure that the Commander is really accurate. I was meaning that going too much over 43psi you risk the chance of blowing your head gasket, I knew that and that was what he was getting at. What he was saying is that yes..he doesnt think that the stock turbo can handle 43psi or that it can make/hit it. I on the other hand have done this pleanty of times, I know its not good, but my commander reads it. I think he is going off of TDR knowldge, but I just wanted to ask if the commander is right or not when I am hitting 43 max psi?

Good points though.

 

Ok, fair enough. Any gauge can be questioned for accuracy. The factual data to back the claim up is what I would interested in hearing. I'm unaware of the Commander boost gauge being any more or less accurate than any of the other popular methods of measuring boost. It seems most people are running heads stud and/or other gasket options when they get to around 50-55 psi or so. Boost alone doesn't really tell the whole story on what the cylinder pressures actually are. The amount of timing advance and actual compression ratio are important factors. Thos that run less timing advance will get away with higher boost levels before the head bolts become an issue compared to those who are more aggresive with timing. The stock turbo is good for about 35 psi....some say 38 but compressor maps don't lie. Any time a turbo is overspeeding is never good thing but the stocker can most certianly hit 43 psi (as you already know) even though the additional boost is in the form of superheated air that causes a power loss because the turbo is out of its efficiencey range.

 

The reason for the inaccuracy is because it taps into the MAP sensor of the truck. The Quad Commander is not the only device affected by this. The MAP sensor is only accurate to 40-44 PSI, which is fine for a stock turbo, because it operates in unison with the MAP sensor. The inaccuracy comes when you step up to a turbo that will handle above 40-44 PSI. To fix this problem Quad has a device that connects to the commander and it taps directly into the manifold through a boost bolt. This device measures the true boost pressure and displays it through the commander. My Commander is very accurate with all the readings.

 

Yes, I did see the update to use an external anologue boost sensor/sender for reading up to 100 psi.

 

Ahhh...CTD...your the man. You just learned me a great deal about boost, and boost vs. cyclander pressure. Also I learned (clarified) that the stock unit at a high boost level of 43 more or less is going to be out of its usable range, not that it cant produce it, but that it wont be pushing cool air but heated air.

good info my friend!