Blew My Head Gasket On Built Engine

[Captain Bondo]

In theory, shouldn't everything beyond 22psi be released since I have a 22lb spring?

I am talking about the pressure in the exhaust manifold, which is likely much higher than boost pressure.

[GeraldJ]

Ct Bondo is right

The waste gate controls pressure in the exhaust.

Like for example I have a 12lb spring in mine but I run 20lbs of boost. The gate is not just controlling boost pressure but the exhaust pressure also.

Remember also that a wastegate doesnt just pop open at the spring pressure. It opens gradually throught the power band to control the amount of gas going through the turbine.

Yours with the 22lb spring is probably not even cracking open till around 19-20 (just a guess. So you are shoving 40-50psi of air through a very small turbine. There is an incredible amount of pressure in the turbine at the point your motor is turning 7k rpm. All this pressure has got to go somewhere. your kind of lucky that it didnt go through the bottom of your piston or force a rod to bend. It could have made your turbo a grenade and sent chunks of cast iron everywhere.

So in short, the biggest spring that I would run on a 19t pushing 20-22lbs would be a 15lb spring and a good boost controller. A 12lb spring with a MBC. I hold 20psi to 7k pretty easy with a 12lb spring and a lower shores MBC, granted my turbine housing is a bit larger. Although it is starting to puff out any where above 7k because of its small AR

[volvo500bhp]

Russ, No tuner in the world would have made a difference with that 22psi spring. My car feels brutal with a 19t and modest boost at low/mid rpm. With the ecu unable to alter boost until 1.35 bar with a turbo that spools just off idle is never going to end in smiles. I don't think trying to saddle MTE with the blame will help the OP - if he tunes the car with a Turbotuner (they sound great by the way) and that actuator spring then engine longevity will be compromised. He can get a very strong performance out of his hardware with a far safer level of wastegate control. Play to the strengths of your kit - that turbo is all about the 2500 to 5500 rpm grunt not caning it's nuts off. Mine will pull from 1500 rpm and I change at 6000 rpm to keep in the torquey midrange. Whatever the tune - it's a 19t not a big garrett.

Hi Jardon

Your right but surely this should of all been checked and gone through when the map was first put on the car IF the OP has changed parts on the car since the tune then its no surprise the headgasket was lunched but if you see what JC had posted about the amount of igniton used by a ''custom map''its amazing the poor engine lasted....

A good tuner may not have been able to cure the underlying issue, but they would have been monitoring the engine more closely and would have aborted the run before it started liquifying the fire rings on the headgasket.

Correct i am sure a decent tuner would of checked the car properly and not tuned it by text message

Here is what I don't understand. I don't have problems with too much boost or detonation at part throttle or even full throttle until about 5500 rpm. I thought I had it cure b/c I did two rolling runs and progressively got into the boost until I hit 120. The third run is what got me but not until almost redline. How would a lighter spring have helped if everyone is saying that the 19T is out of breath at that point? Why would I want my wastegate to open and release boost?

So had you changed anything since the Tune ??

Your wastegate would not be "releasing boost". Your wastegate would be releasing the 40+psi of 1500+ degree exhaust gases your motor is gagging on. You need to understand the kind of strain that is putting on things...

Very well put :ph34r:

[Jardon]

Hi Jardon

Your right but surely this should of all been checked and gone through when the map was first put on the car IF the OP has changed parts on the car since the tune then its no surprise the headgasket was lunched but if you see what JC had posted about the amount of igniton used by a ''custom map''its amazing the poor engine lasted....

If I fit a 22psi spring to my car tomorrow and blow my HG do you think think I'd have grounds to complain about the state of tune? Would you support a customer who did the same thing with a RICA PPC tune? JC's engine is irrelevant to the OP's situation.

Correct i am sure a decent tuner would of checked the car properly and not tuned it by text message

Do we have evidence to support that?

So had you changed anything since the Tune ??

Yes, please do tell.

Very well put

If the wastegate point is well put then why the MTE digs?

[HeavyIron]

Thank you to Cpt bondo and Gerald for properly educating me on wastegate actuators since many people (forge included) had previously told me that you want a spring equal to the boost pressure you are trying to achieve EPIC FAIL!

I believe the wastegate does play a part, but is far from the whole issue. Marco never asked me about wastegates when he emailed me a list of questions for what I was going to be doing to this car. Furthermore, I have been having misfire/ detonation problems since day one starting as low as 16psi of boost. The situation has gotten progressively better by the installation of the 6AL boax and 3 temp range colder plugs but is evidently still there.

In short, Marco's tune is partially to blame just as my wastegate is partiallly to blame. I will be following Gerald's advice and going down to a 15lb spring and hopefully Marco will be willing to do a little reflash work to correct his. Thanks to all

One last note, rolling into boost the car seems to hold 20-22 psi no problem, but sudden WOT from a dead stop is no good (misfire). Anyone care to expound on that?