So I've been searching through this forum and a couple others actually regarding Turbo'ing and Supercharging and every once in a while (well a lot more often than that), I'll come across a post by someone who asks questions and blatently doesn't know anything about FI (I don't know that much myself tho)...

So immediately everyone goes on the attack and says that the guy/girl is going to blow up their motor because they know nothing...and they obviously don't know much...

Now...the way I see it, if he/she doesn't know anything...chances are they won't be doing the install themselves and I don't think the person who installs it would put some ungodly amount of psi into an motor that he knows won't handle it...but maybe I'm just being naive...

But anyway...to my question...other than trying to create more pressure than the motor can handle...how else could a person destroy their motor w/ a turbo?

(Keeping in mind that something like "Installing the turbo on backwards" or "Installing it incorrectly" is a bad answer =P)

 

The phrase you used, "more pressure", can be broken down into two aspects: more horsepower and more detonation. I'll describe those two and then list a few other good ways to kill a turbo motor:

#1 - More boost with enough fuel creates more horsepower; too much horsepower and you'll snap a rod and/or crankshaft.

#2 - More boost without enough fuel creates knock, and knock is the precursor to detonation. Detonation (pre-ignition, the combustion of fuel & air inside a cylinder before the spark plug fires) causes insanly high cylinder pressures well beyond what a normal boosted cylinder would endure. This is a very powerful force and can snap bottom end components though typically you'll see a blown headgasket first. It's not usually horsepower that blows headgaskets but detonation instead.

#3 - The third way I can think of to detonate is to have very very hot incoming air, possibly due to the turbo is too small for the application or maybe there's a slightly undersized turbo no intercooler. If the air coming in is too hot it will have a much greater chance of detonating regardless of how much fuel you throw at it.

There's a fine line to be found in tuning. Richer (more fuel) is safer to a certain degree, but it also means less power. Go too rich and you start knocking due to there being an excessive amount of fuel in the combustion mixture. Leaner (less fuel) equals more power up to a certain point, but after that knock appears which then creates less horsepower. Higher exhaust gas temperatures is a side effect of leaner tunes.

The trick is to tune very well. Everyone says "that motor will take 8 psi" or "don't boost over 6 psi", but that's not it: every motor has a horsepower limit, not a boost limit. Average turbo owners don't tune well and as a result they can detonate, hence people believe they can only run 'X' psi. If you have access to the proper equipment you can tune a motor for no knock and maximum power.

#4 - Some people ignore knock and lean the motor out too far causing incredibly high exhaust gas temperatures, sometimes in excess of 1800*F. Temperatures like these can melt valves and do serious internal damage to the motor.

These are the four ways I can think of to kill a turbocharged motor at 1am on a Saturday.

 

The problem is, a lot of people who don't know what they are doing do have money for the parts and do want to install it themselves, even though they have no idea what they are doing. This causes problems, so we try to discourage them before they waste a lot of money.

Secondly, have you ever heard of a manual boost controller? It's a neat little device, it can be home made for about $20 or bought for under $120. It goes inline with the wastegate vacuum line, and cranking down the adjustment screw ups the boost. It's so simple, a baby could use it. What I'm trying to get at is that any idiot can force a Honda engine to run at 15psi, which will be an untuned 15psi, and the result is a very blown engine.

I've seen a guy on a dyno that had one of those cheap home made manual boost controllers on his Mazdaspeed Protege. It knocked all sorts, he could have lost his engine. :chuckles:

 

The simple reason like DarkLightning said, is that a turbo forces more air into the motor. More air needs more fuel to go with it, and most ill-planned turbo setups do not take this into account.

When the motor runs too lean (not enough fuel) it detonates. This is a condition where the air/fuel mixture inside a cylinder ignites before the spark plug sparks, due to heat, compression, etc. It's also called knocking or pinging. Too much detonation and something inside is going to break--a piston, rod, whatever.

 

But essentially...as long as you can tune it properly yourself OR you get someone who knows what they're doing to tune it...everything should be fine...

Is there anything negative about turbo'ing an engine w/ a V-Tec system? If anything I would think it would definately need new fuel management...but a turbo system would need a new one anyway right?

 

If you can tune it or know a good shop that can tune it for you, you're fine to a certain point. That assumes you have the parts nessicary to do it.

The VTEC system of some Honda engines is really focused on N/A performance, allowing the engine to run a conservative cam profile in low RPMs to keep a good idle, drivability, and fuel economy, but run an aggressive cam profile (with more overlap) at high RPM for absolute performance. High overlap cams are not nessicary for turbo'd engines, purpose made turbo cams actually have less overlap and higher lift. There's a lot of mixed feelings around on the subject, but if it was me I'd save the money on the VTEC engine and use it to better turbo a non-VTEC.

 

On VTEC and turbos: the simple answer is yes, VTEC and turbo are best buddies and can make a bunch of power together.

Now the more detailed answer.

Overlap is defined as the amount of time when both the intake and exhaust valves are open. This helps a normally aspirated motor because the exhaust valves being open creates a vacuum which sucks more air in through the intake valves and then closes the exhaust valve justs as the cylinder "fills up" with air.

On a turbo motor, since air is being forced in at a higher pressure and velocity, the exhaust valves need to close sooner to preven the intake air from blowing right out the exhaust valves before they close and causes power to be lost.

Thing is, while the stock VTEC cams do have a decent amount of overlap, they are not so aggressive such that they stay open and let boost leak out the exhaust valves while they're still open. A more aggressive cam designed for a normally-aspirated application might have that problem, but all that means is you should stick with either stock or turbo cams.

 

Turbos don't kill motors, bad tuners do.

 

:werd: