Gohan3rdrift

iTrader: (11)

Pics coming soon...
I have a theory on why it blew and was wondering if it has happened to anyone else.

My rev limiter is set by "fuel cut" and NOT "ignition cut".
That's where I believe it went wrong.

I had it tuned a few months ago and NEVER redlined it.
I have been racing it without going to the 8000 rpm redline, shifting at 7500 rpm.
I never felt the need to...until I raced this past weekend.
Then at the top of third...BOOM!!!
As soon as it hit rev limiter, it hit it's end.

I have a Haltech E8, and injecting 100% methanol.
~504 whp
~1680 cc injectors ALL AROUND
~(2)Coolingmist S-HSV controlled by the ecu
~(2)12 gph nozzles for meth

The S-HSVs are controlled via "generic pwm" and does NOT have a cut-off option.
Like I said earlier, the "rev limit" is controlled by "cutting fuel", BUT do you guys believe that the meth still spraying is what caused it to go lean and pop?

I expected it to be addressed already that "Meth injection should always be set with an ignition rev limiter."
Either I missed that or I obviously lack that common sense then.

manveru

damn man, thats a ******* bummer, but at least she went out in fashion. top of third WOT ftw. engine number 6 up next?

and you have until november 29th, so get to work son! but for cereal.... you have til november.

jamespond24

iTrader: (13)

What seals were you using?

Gohan3rdrift

iTrader: (11)

you know it bro



I was using the oem seals.

BDC

Having the alcohol on at the point of rev limiter won't cause the engine to run lean. Having the rev limiter shut off the fuel injectors is what caused it to run lean if you want to call it that. But, you are on to something -- As a matter of practice on the cars I setup w/ AI, I use spark cut and not fuel cut. Rather, I'd avoid the rev limiter all together and use a shift lift.

Things to know: What advance? What split? What boost? What was the failure?

B

84stock

iTrader: (5)

OEM seals are touchy with abuse, found that out the hard way. I'll bet you'll find the tips sheared off and your housing scored to hell. Tough break! Ignition cut would have been much better, the only thing you might have blown then is a couple of mufflers when all the raw fuel ignited in the exhaust.

Gohan3rdrift

iTrader: (11)

Your input is very appreciated Brian.

boost: 22psi
advance: 16*
split: 12*
failure: Rear rotor

That's actually the first time I have blown the rear rotor.

Gohan3rdrift

iTrader: (11)

It seems I always have to learn the hard way...

BDC

May wanna back the lead advance off a bit. I used 16* with a 7* split on my old setup w/ the 60-1HIFI up to about 25psi but I was using a hell of alot of alcohol (1/3rd of the overall fuel output was straight alcohol). The split is fine.

As far as advance as RPM's go higher, don't fall into the trap of cranking 2-3* per 500rpm past 6000-6500rpm. That's a big trap and it's causing alot of engines to go to scrap metal heaven. Especially if it's a high overlap engine, keep the advance even. If it's a stock or mild street port, perhaps 1* from 6500-8000rpm.

Edit: Now that I think about it -- how much alcohol are you actually injecting? how much fuel are you replacing? What AFR's are you targetting? What plugs are you running?

B

Gohan3rdrift

iTrader: (11)

At 7750 RPM it's injecting roughly 78% duty cycle.
I'm running two nozzles, both are rated at 12 gph or about 750cc/min together.
I'm running four 1600cc injectors of fuel or 6400cc/min together.

As for the plugs, I'm using the 10.5 racing plugs.
And the AFR's are around 11.2 at peak power.

I just noticed that the "Generic PWM" stops at 7750...
So, what happens after that since my redline is at 8000 RPM?
Why do I have to make such expensive mistakes?

Viking War Hammer

iTrader: (8)

Steve Kan tuned your current setup, right?

Viking War Hammer

iTrader: (8)

Dp

classicauto

iTrader: (3)

How many miles on the engine?

What type of ignition are you running? (wastespark leading?)

Was there an overboost? how did the car feel when it happend? meaning was there a slight hesitation, did it backfire, how did the failure make it react...

Gohan3rdrift

iTrader: (11)

Yesss sir....
Donkey Puncher??? ~~~~~ J/P
I have (4) LS1 coils so it's Direct fire.
Miles on engine since the tune is around 3000.
Boost always spikes because I'm cheap and have a manual boost controller, but doesn't creep.
I was at the top of third so the spike was "leveled out."
No hesitation. It was pulling really hard. Awesome power.
Honestly, I can't recall if it backfired or not.

BDC

Given who tuned it, I would guess too much advance for the RPM.

Also -- how much fuel are you replacing with alcohol? How much is truly being injected? You've told me the totals you've got but that doesn't tell me exactly what ratio of fuel to alcohol is being used. It's important.

Edit: One more thing -- what kind of trigger setup is this? 2nd gen CAS or 3rd gen crank trigger wheel?

B

slo

iTrader: (1)

Is it set on hard or soft fuel cut?

The Generic PWM map stopping at a certain RPM point is configurable. You can change the RPM and MAP points at the map or select a default set of RPM points under another settings tab. I do believe that it continues injecting above the last rpm point.

Howard Coleman

iTrader: (6)

"At 7750 RPM it's injecting roughly 78% duty cycle.
I'm running two nozzles, both are rated at 12 gph or about 750cc/min together.
I'm running four 1600cc injectors of fuel or 6400cc/min together."

i am not clear on your meth injector sizing....

are you running two 12 GPH/756 CC/Min injectors or are you running two injectors that total 12 GPH?

i run two 700 CC/Min injectors on my FJO setup for a 1400 total..

anyway, you have it nailed... the engine went lean when you hit fuel cut and were still spraying meth.

your setup sounds like a real tiger. it must be fun to hang on to.

as to your IGL after peak torque, whether you add a degree or 3 you were toast w the fuel cut.

here's hoping you are back on the road soon... with an ignition cut.

howard coleman

classicauto

iTrader: (3)

For what its worth, any time I've popped an engine due to a lean condition, there was no noise (no audible knock) and no hesitation, just a blown engine.

Viking War Hammer

iTrader: (8)

Yep, the only sound is "BLAAAAAAAAAAAAAAAAUUUUUUUUUUUGHHHHHHHHHHHHHHHHHHH HHH

kev-yorks

If there was total fuel cut under boost how much meths would need to be in the combustion chamber to cause problems? I'm sure i read on here somewhere that you needed 50% fuel in the combustion chamber to get a viable burn. From memory this was something Peter from rice racing posted in the racelogic group buy thread when questioned about the saftey of fuel cut.
Kevin

BDC

That's what usually happens -- doing hard run, get out of the throttle, then the 'bdp bdp bdp' it won't idle pulse.

B

darmy

iTrader: (10)

I was thinking the same as kev-yorks. According to Racelogic, you'd need at least %50 of your AFR to have any sort of combustion. I don't think that half of the OP's fuel was being provided as Meth.

If it is possible for the Meth to cause detonation all by itself, the Racelogic traction control and Meth injection combo seems like a very bad idea. But, it seems like this combo should be common, and we'd have heard if people were popping engines with it.

classicauto

iTrader: (3)

The only part that bugs me (obviously not as much as gohan here though!)

Is that if Steve tuned this car, and fuel cut will pop engines, why on earth would it be set that way? I thought that was part of the tune - the other parameters that keep it safe and running well. Ie. corrections, rev limiter etc.

Viking War Hammer

iTrader: (8)

Can someone contact Kan and direct him to this thread. He needs to see what's going on.

pluto

I just saw this thread. I looked at the map and it was set to hard fuel cut at 8k rpm. There is no reason for the hard fuel cut to damage the engine since almost all OEM computer uses hard fuel cut to set the rev-limiter including the factory Rx7 ECU. If it would damage the engine, OEM manufacture wouldn't use it to begin with. PFC also uses hard fuel cut to limit rpm. On the other hand, ignition cut kills turbos. I damaged at least 6 turbos (thrust bearing failure) due to ignition cut back in 2000 because of it, I stopped using ignition cut along time ago.
Also to BDC, 16 degrees w/ 12 degrees split is hardly too advance for these cars. 16 degrees w/ 7 degrees split is too advanced. Leading timing doesn't kill engine. 90% of the time, it's the trailing timing that causes detonation. Additionally, timing drifts by a couple of degrees at higher rpm (typically around 2 degrees) so it is most likely running approx 14 degrees of advanced. You should revisit your timing map methology before commenting on timing advance.
The only thing suspect is using the Generic pwm map for aux injection. I'm not too sure if it still continues to spray after 7750rpm. There were no adjustment for rpm range so 7750 is the highest it would go. We nevered tuned it past 7700rpm when it was tuned using the dyno pak (it limits how far to go). If the meth injection did shut off after 7750rpm, it would lean out by approx 14% off fuel and could damage the engine.