What's my boost safety/danger zone?

[GrimJack]

I really should point out that my success does NOT make it safe for anyone to try pushing 18+ psi through their engine on a stock HG. Your mileage may vary.

Keep in mind I was TRYING to kill the motor. Emulating what I was doing will probably end up with the same or similar carnage in your own engine bay.

 

[svnmpwr]

If it were me, I would retorque it right now and just start building another motor.

 

[Clueless]

If it were me, I would retorque it right now and just start building another motor.

 

[dugums]

I'm not making as much power as some here, but I made it a point to add my power as safely as possible (excepting my decision to go composite).

Before adding power, I went through the car and replaced everything that needed replacement. I then added some tuning and monitoring tools just to be on the safe side. I also tested and cleaned the injectors, replaced the fuel pump and afpr, etc, etc...

It's one thing to assume you know what's going on based on how the car feels - it's much nicer to be able to monitor actual boost levels, A/F ratio, EGT's, etc.

I normally run 10psi on a 57 trim with my composite gasket (I have a higher setting I use on occasion). I can't find any rational reason it wouldn't hold up; I did everything carefully and precisely. But I guess we'll see.

 

[theKnifeArtist]

i'm running an oem headgasket on a resurfaced head and arp studs torqued to whatever the arp card said, i forget.
i'm running up to 13-14psi, and it been okay so far *knocks on wood*
that's the setup that i would think is appropriate for a stock ct setup.

 

[Dan_Gyoba]

Don't worry, Grim. I'm not looking to do what you did, since I plan on NOT blowing my motor.

 

[ArmandoP]

the rule I normally use is turn the knob until it goes boom.... then turn the knob back a little bit. YMMV

 

[CajunKenny]

Ok. So, newbie type questions here.

Aside from the knock sensor, how does one know when detonation is happening and how does one prevent it?

 

[IJ.]

Kenny: Safest way is on a Dyno with electric ears then tun below that point.

Usually by the time you hear it on the street the damage is done.

 

[vas85]

IJ, if you could run 30psi on the twin turbo v8 or whatever it was with composite HG, then in theory i'm just trying to think a few things here, the HG on the 7M if torqued correctly at stock specs (for boost etc..) and provided there are no problems with cooling in theory should never detonate, and that in theory means the HG shouldn't blow?

I'm then thinking that incorrectly tuned addon ECU's / SAFCII / MAFTPRO n all that stuff and a lot more power cause detonation and tick tick boom goes the HG?

On my 7M when I had the HKS EVCIV that was running incorrectly I had it about a year ago running 16psi for two weeks or so.. (I dont drive 16psi everywhere but you know random hit here/there) I apparently have a MLS Cometic 1.3mm MHG but I'm not too sure but I would believe it now. Because 1.5years ago when I got my Supra first thing I did was get a low k JDM engine to drop in as the previous one from the owner had severe case of blow-by and ultra low compression. This was all before I knew about any forums, notably supramania which I now call my MKIII home!

 

[IJ.]

Vas: Correct!

My TTv8 had a really conservative tune and ran a Methanol injector as a bandaid as there were almost no electronics involved, tuning this way allowed it to live and I never had a drama with it.

The 7M HG design has built in fail points so a single heavy rattle will kill it, if you tune on the ragged edge it's just a matter of when.

MHG's raise this threshold but a bad tune/hard rattle will kill them as well (I've BHG'd 3 different MHG's)

The difference here is with stock components a rattle hard enough to cause a MHG to fail will usually cause mechanical damage as well

 

[vas85]

IJ: very interesting about the rattle... I was just putting two and two together from a post someone put about the supra ECU before 176* F it runs in enrichment and after 210* it advances or something to prevent detonation.. which then your post made me think about the whole heat issue and why a HG would go in the first place.

What kind of rattles are we talking that cause a HG to fail? like is it something you would hear like rod knock style?

Interesting you've BHG'ed 3MHG's but then again anyone pushing power you're really at the limits of a lot of things so to speak.

 

[IJ.]

Vas: Usually by the time you hear a rattle on a composite HG the damage is done or has started...

Detonation has a very unique sound like somone has a can of small nuts in the motor.

In my case it's just been an ongoing development thing with the LPG fuel system and getting some bad info early on (PWR rate their IC's in Crank HP not RWHP)

 

[vas85]

That's unlucky about the IC's, would you recommend them though for someone like myself pushing at most 400crank HP one day...?

It's amazing too I've learnt so much on this forum from all its members that you would otherwise be left in the dark with.

 

[IJ.]

Vas: As much of a parts snob as I am I would never pay the premium for a Brand Name IC again!

Big Chinese E-bay IC wins hands down!

 

[vas85]

Vas: As much of a parts snob as I am I would never pay the premium for a Brand Name IC again!

Big Chinese E-bay IC wins hands down!

Hahaha... so I guess big chinese IC pressure tested good to go and you're done. LOL

 

[IJ.]

A bud brought his 600x300x75 China IC around to show me and I was all set to bag the shit out of it...... I opened the box had a good look at it and ordered a 100mm thick one the next day

 

[vas85]

hahaha....now that's a funny story...

I'd be curious to find a big IC that would use the stock IC piping points, you've inspired me to check ebay

 

[turbodriz]

Is detonation like pre-ignition?

 

[IJ.]

Driz: Detonation is more an overpressure situation that turns the motor into a diesel.

Preignition is more when there's a shap edge or a carbon deposit that lights off the fuel early.

(this is way simplified before anyone jumps on me)