spoolint78

iTrader: (37)

i think the high boost and 91 octane caused it to detonate.
also, isn't 93% duty kinda high?

what was your timing at?

TTP Engineering

iTrader: (465)

The cylinder pressures seen during detonation are many times that of normal boosted combustion. High enough to force shrapnel back out the intake valve evidently and back through the intake manifold. That is my guess.

86gti

wow.. thats pretty crazy . learn something everyday

althemean

iTrader: (5)

you are right. The answer was there in front of my face. Sometimes it takes an outside look to see things. The rocker arm came off the intake valve (which was hanging slightly open when I pulled the head off) on the cylinder with the cracked piston. Thats how the metal spread.

It has already been verified it was not the tune for all those who are asking. Timing was a little agressive thru the midrange (probably a contributing factor but not the main cause) but I normaly run 100 octane all the time. The afr's were fine. The biggest cause of this was simply my fuel pump giving out and causing a lean condition. Boost levels were at 19psi so nothing crazy happening there.

I will post some pics of the cylinder head in a little while.

althemean

iTrader: (5)

here are the pics of the cylinder head

Ted B

iTrader: (6)

Also worthy of note is the fact that your AEM EMS cannot effectively control your EVOs injectors. The AEM EMS is configured for a low performance (high impedance) injector. Your EVO is equipped with a high performance peak and hold type (low impedance) injector. This creates an significant mismatch that compromises injector control, and is why AEM EMS users report needing ridiculously large injectors. AFAIK, you have the factory injectors, which means that you will run out of injector faster than someone else with factory injectors and anything other than an AEM EMS. Have you considered this? Were you informed of this?

Additionally, I believe you mentioned something about oil in the intake. One thing this will do is dramatically lower the detonation threshold. Even the slightest bit of oil contamination in the intake charge creates very high combustion temps and will surely cause detonation.

althemean

iTrader: (5)

Yes, you and I had discussed this in another thread. While I feel that it is an underlying problem, I do not think it was the root cause. The car would have experienced this problem much sooner considering that I had been driving around for a month on that tune with at least one auto-x on the car as well. If you had been in the car when I was driving while this happened maybe it would be easier to understand. It is unfortunate that I was not data-logging when this occurred but I dont own a laptop and dont tune the car.

In any event, I will remedy that with the larger injectors on my new build-up. It is a by-product of using the AEM unless I want to drop the cash on their injector driver.

superz

iTrader: (7)

The Evo uses low impedance injectors with a resistor pack to convert them to high impedance, which is what most ECUs can control. Therefore I cant see why the AEM would cause a problem here being that it, like most others, controls only high impedance injectors. Time and time again I see failures with EMS systems, wrether its tuning or operation they seem to be time bombs if not done setup correctly.

althemean

iTrader: (5)

who is correct on this then? I know Ted B has a lot of knowledge on these cars but I see that Little title under Superz name.....(BTW I used to have a 83 280zx with a built motor and every bolt-on I could find on it, there is nothing like the old z-cars)

Ted B

iTrader: (6)

The factory ECU IS correctly configured for low impedance injectors. The driver pack does not magically 'convert' them to high impedance. One can no more do this than he can magically convert a 4 ohm speaker to a 16 ohm speaker. The driver pack allows the circuit to apply the current necessary to properly switch the injectors.

As far reputable EMS systems (e.g. F.A.S.T. XFI, Autronic, Microtech, Haltech, etc.), all are equipped for low impedance, peak and hold injectors, which is what virtually every high performance application uses. The AEM EMS is not. A quick trip to AEM's website confirms this. But we all know this because AEM EMS users who don't opt for the extra $300 driver pack must always use unusually large injectors. The reason for this is there isn't enough available current to pulse the injectors quickly. The result is slow response time.

althemean

iTrader: (5)

slow response time.......that is interesting. That concerns me. What about the fact that tuners such as AMS and Buschur have no problems with this system on cars with very high WHP figures and appear to do it reliably. Will just switching to the larger injectors be sufficient?

Ted, it sounds like you just dont like the AEM EMS system

Ted B

iTrader: (6)

Using an unusually large injector is a band-aid fix, and is almost certainly responsible for the hard starting issues with the EMS that have been discussed here. I don't know of any reported reliability issues, although I'd do it differently, as trying to control a peak and hold injector with a high-impedance driver is said to create high current loads that can shorten both the life of the drivers and the injectors.


Like anything else, it has its strengths and weaknesses. IMO, its strength is its logging ability, while its primary drawbacks are the high impedance injector drivers, the relatively weak ignition section, and the price.

jmartinez1170

iTrader: (21)

Yea this happen to my car to join the club good luck with your rebuild. Looks like your going to have to send your head to get reworked as well. I think i spend around $2800 for my rebuild with install.

modvp

iTrader: (13)

This seems like a very common problem with the AEM; however it does not seem to get reported.

althemean

iTrader: (5)

I never had hard starting problems with the car. It had the usual 3-4 extra revolutions over the stock ecu but it always started, hot or cold. I hear what you say on the high current shortening the life of the injectors. It may be worth it to just buy that peak and hold injector driver aem sells. I really like the system. It made great power before the motor let go. I just need to take a few more precautions on the next tune and engine, thats all.