dkersten

From what I read, here is my theory:

You were running hard, so the IAT's had to be pretty well up there already. You were revving high, near redline, which is the most dangerous time for ANY engine. Then you let off the throttle a little, and punched it. When you let off, fuel stops flowing, but at 6k rpm, you still have a ton of air going in. Then you punched it, introducing fuel to an all air environment, with some very hot air to begin with due to a lack of intercooler, and BANG, detonation. At 6k+ rpm with boost to back it up, a detonation is exactly the reason these motors will go.

If you ever watch your AF gauge, you see that under 7/8 throttle, your AF ratios are not the same as under 100% throttle, they are far leaner. This is dangerous when combined with high revs, boost, and a high IAT. Add dropping off the throttle then punching it again and it is a recipe for disaster.

The boost and lack of intercooler made this situation worse than it already was, but frankly, even an NA engine under these circumstances can be affected. Detonation at high rpms will take out an NA engine just as easily as a boosted application.

Good luck on the new engine, and I hope it all works out for you! Just quit trying to break the speed of sound in the future and you probably won't have any more problems.. heh.

stealth_GT

Ditto. You ever have those moments like what the hell?? what could it hurt? lol yes, there is nothing more frightening than ignorance in action rofl



New motor is great and I am well aware of the consequences of trying to push things to the limit. wish my camera worked when I was dissasembling the old motor before stuffing in the pressure washer. That thing was toast! Cylinder no# 8 was totally wipped out and the piston top was completely thrashed and cracked.. rods were mia except for where it bolts onto the crank. Crank looks good but messed up around that piston that blew. I still have the block just for rememberance of a no good bad situation.. I'll post it up later before I take it down to the metal recylcing plant for some loot. Still got the heads too... one is good, one is banged up..

Mishri

I just don't understand what the problem to begin with was.. the car doesn't shift into 5th until it runs out of gear in 4th if you are wot.. unless your tune was somehow screwed up to bypass 4th which doesn't make sense.. top speed runs in a 4spd with 4.10s wont work obviously.. but will work fine for the track.. you wouldn't have even been trapping anywhere near 120mph.. 4.10s are track gears.. so buy gears based on what you want to do with the car.

4.10s work fine on an auto s/c car.. and my friend with his stock auto did well with a saleen (until he went over 11.5psi and blew the motor going down the dragstrip)..

I've done a lot of passes w/overdrve on and w/it off, and i run the same either way.

stealth_GT

I am not sure actually. I can tap out 4th at 135mph (last attempt, kaboom) with the OD off. I can do 120+ easily in 4th with the OD on, but it takes so damn long in 5th! it'll literally sit at 3200 and slowly climb. I have been trapping better times actually with the OD off with the blower.. going back this weekend for a 12.5@110mph.. gonna drop the pressure on the rear tires a little for more traction..

mcstang

Stealth, did I miss it somewhere? Did you talk to Brenspeed yet about this. I've been following like 10 of your threads and maybe missed it! (JK on the 10)

stealth_GT

uh oh. interwebz stalker.. jk


yes, talked to them the day after it happened. Boost+ topping out on a stock motor is never a good idea, especially trying to hold boost and going WOT like I did... to think I was trying to "save" the motor. I even paused after I shifted (holding 4th/OD off), before getting on it again. Right now, final gear (OD on) is set up ( as it's supposed to be) very conservatively at right around 3200 rpm slowly rising with nearly 0 boost.


New motor runs like a champ. Gonna go back to the track and get those mid 12s@110 I am expecting..

mcstang

So with an auto, you should leave the OD on at all times with a Centri? Sorry I'm slow

stealth_GT

just don't try to hold 4th to 135mph and you'll be okay. the 4.10s burn through the gears soo quickly and without traction it just wastes through the tires/gears.. once I hit final gear at 100mph or so (OD on) it will NOT pick up as much speed with the OD off. Trust me, my traps were 100-104mph with the OD on and 108mph and climbing with it off.

Mishri

weird.. do they change the tune to not top out 4th gear for your vortech when you are WoT from brenspeed(or downshift past a certain rpm in 5th)? because i don't shift to 5th unless i let off the gas when i'm WoT... thats how it' setup from the factory... i also am using a brenspeed tune.

stealth_GT

it tops out 4th but feels like it just taps it at 100mph and then final gear... not too awe inspiring when I know for sure I can HOLD it until 130-135 or so @6100rpm. I don't advise trying. When NA, I used to do roll runs with the OD off and top out quickly, then shut the OD off to top out ( not very safe, nor smart.. I know!) With the OD on, it's like a chastity belt on the blower.. no fun, though from a dead stop it snaps through all the gears very quickly which can be fun.



Honestly, once I get a roots blower- I will go 3.73 or 3.31s..