fusion-turbo

I have had a problem whenever i hit WOT under a heavy load (like 5th gear highway) i will hear multiple "creaks" untill i let off. Its coming from the engine bay. I try to avoid it (obviously), but i have done it several times and i am a little nervous. So far my engine seems uneffected.

How quickly does detonation kill a motor, and also is this detonation? Wish i could describe it better

The Spyder

iTrader: (8)

What octane ya running?

AcidShock

iTrader: (49)

Some have described the sound of detonation like popcorn popping. Or in some extreme cases, loud tinny banging inside the engine compartment. On how fast it will kill a rotary engine... fast. The apex seals cannot usually take too much abuse from detonation before they fracture and dig up your housings as they get coughed out the exhaust.

RA claims though that their seals can withstand detonation to a point. Whether this is true or not I have no definitive proof other than what I see on their web site and their reps have told me. Take it for what it is worth.

fusion-turbo

I usually run a mix of 91 and 89, never the 87 I'd like to be running 94, but gas is expensive enough as it is.

As far as detonation killing the engine fast, this has happened to me numerous times. Over 15, and its multiple creaks every time. It doesnt sound like a tin banging or anything, and i also guess its how you interperet the sound of popcorn popping. It sounds like it might, but its closer to a "creak" to me

J-Rat

iTrader: (2)

Dude, you will kill your engine.. FAST... If you think your having detonation issues, retard your timing..

SureShot

You are very close to the edge of disaster.

Like J-rat said: Back off the timing.

OverDriven

94 is too expensive!? You think a new engine is cheap?

-Joe

Relisys190

iTrader: (4)

If your good enough to hear it, back off instantly. a good ping will blow seals FAST... Ever seen a 450hp Rotary ping at 8000 rpms on the dyno at 18 lbs of boost? Trust me, it's a sad thing to see when power levels just drop instantly and than... strange brap, brap, brap... yup, half a motor left. Sometimes your lucky and your turbo doesnt get destroyed as the exhaust pulse spits your seals out...

Get off the wallet, purchase 94octane OR back off the timing properly OR lower your boost levels OR get your intake temps lower OR sell your car and purchase and N/A OR get a large bucket of acid and pour it down your pants.

EASY!

Regards,
-Markus

fusion-turbo

Well maybe what im hearing isnt detonation then. If it kills an engine as fast as you all say it does, this has happened to me repeatedly over the last 6 or 7 months. If i try retarding my timing, wouldnt that just cause me to pre-ignite? right now im sitting right at TDC, definately not advanced. As i said, my engine still seems to be un-effected... would that be strange if this was detonation?

As for 94 octane goes, how would that help detonation? Is that what your all running? Also, i dont even think its available in phoenix, what gas stations carry it?

casio

octane is an anti-knock rating (of some sort; i'm not an expert). the higher the octane, the less likely you are to detonate from an unwanted pre-ignition.
advancing your timing is dangerous, a bit of retarding is safe.
i have never seen 94 at a gas station, where i live its usually 87-89-91-93; if i had a turbo, i'd use the 93 just to be safe. especially in the heat.

::if someone can explain pre-ignition/knock/detonation better, please do, i would love to learn more.

Mephis

My engine makes a wild echoing howling that sounds evil when its past 7,000, but its running perfect, is that det?

vaughnc

I have my NA & TII ping before.

The NA usually just needs a tuneup if you hear pinging

On my my TII I have a bit of boost creep from an open exhaust. Normally not a problem but on cold humid nights you can watch the OEM boost gauge SHOOT up rapidly and you get a nice ping. My engine block might only have 30K miles on it, but everything else has 140K... so I don't think the stock BOV & overboost systems are still as effecient.

Fritz_X

iTrader: (1)

fusion-turbo

I dont even know where to get 93 octane around here, what gas station can you get 93 at casio?

I have an open exhaust and intake and im onlly pushing about 8lbs of boost. i have no way of adjusting my boost manually. I still need to port my wastegate, but i havent noticed boost creep nearly at all. Ill hit 8-81/2 lbs on my aftermarket boost gauge at WOT and it will sit right there, it wont creep any higher.

I know that many of you guys are running WAY more boost than i am, how are you avoiding this?

casio

any. i noticed in west texas they only had up to 91. of course, there is nothing in west texas and i beg anyone to avoid the area from el paso to d/fw. its a desert.
most any gas station around here will have 93. its very common.

casio

exerpts from howstuffworks.com:

Timing
"The timing of the spark is important, and the timing can either be advanced or retarded depending on conditions.

The time that the fuel takes to burn is roughly constant. But the speed of the pistons increases as the engine speed increases. This means that the faster the engine goes, the earlier the spark has to occur. This is called spark advance: The faster the engine speed, the more advance is required.

Other goals, like minimizing emissions, take priority when maximum power is not required. For instance, by retarding the spark timing (moving the spark closer to the top of the compression stroke), maximum cylinder pressures and temperatures can be reduced. Lowering temperatures helps reduce the formation of nitrogen oxides (NOx), which are a regulated pollutant. Retarding the timing may also eliminate knocking; some cars that have knock sensors will do this automatically."

--

"Knocking happens because as you compress air, the temperature of the air increases. The temperature may increase enough to ignite the fuel before the spark plug fires."

"The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting."

"Octane (eight carbons)[as opposed to methane-1/ propane-3/ butane-4/ pentane-5/ hexane-6/ heptane-7 -- casio] handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.

During WWI, it was discovered that you can add a chemical called tetraethyl lead to gasoline and significantly improve its octane rating. Cheaper grades of gasoline could be made usable by adding this chemical. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are:

Lead clogs a catalytic converter and renders it inoperable within minutes.
The Earth became covered in a thin layer of lead, and lead is toxic to many living things (including humans).
When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more."

fusion-turbo

Great info casio and thanks alot. Alright, now the question is where to find higher octane gas. I guess i could always buy a can of octane booster and add some to every tank of gas... gas stations around here just dont have anything higher than 91 from what ive seen. I miss new york.... ah those days of running cam 2 race fuel.... 100+ octane....

I am running very rich from what i can smell in my exhaust. Ive been told people can smell it while driving behind me, so im not afraid of running lean. So if im not running lean can this still be detonation?

fusion-turbo

Does anyone have a video or a sound byte of an rx7 detonating? I would like to hear how it sounds so i can see if thats what im experiencing or not.

fusion-turbo

I did a search for any sound bytes or videos of detonation and came up with nothin, does anyone have any? I would really like to know what it sounds like so i know if thats what im experiencing

casio

it would be pretty hard to get a video i imagine. most sound clips are created on purpose. no one wants to detonate on purpose. i did see a video of an NSX blowin an engine on a dyno run once.

RETed

http://fc3spro.com/TECH/FAQ/deton.html

We've destroyed a brand new rebuild that was using brand new 2-piece Mazda OEM apex seals...instantly.


-Ted

Jennie

Tunning is key. I run 17psi on the street, but that with extensive tunning and lots of supporting mods.

Detonation *can* kill your motor nearly instantly. Sometimes you'll get luckly with lots of small pings that were quite right to blow a seal. A certain someone I know locally ran with detonation for a long time, kinda like you have been, before poping his motor. You aren't going to get any warning. The next time you hear that noise could be the end of your motor.

Smelling gas isn't necessarily a good indication of rich or lean. You could be leaning out under boost and not really know it, unless you have a wideband on there. could be that your injectors aren't really flowing what they should be, or if your fuel pump isn't rewired and supplying proper voltage.

The point is, never guess on the air fuel ratio. Get a wide band to see where you are... that's the only place to start trouble shooting.... otherwise you're just shooting in the dark.

carx7

iTrader: (31)

Uh... that was me,^ but I have no idea where that name came from

-Chris

fusion-turbo

This is mainly an altitude problem. I live at 4500 ft elevation and i can have my car @ WOT on a chilly night and i wont even hit enough boost for fuel cut, and i wont hear this "creaking" sound.

But while in phoenix at 2000ft elevation, its a different story. So i believe my injectors are ok becuase if they were bad it would be doing this all the time.. i think. Still need to do the fuel pump re-wire, that could be it.

Also, do those air/fuel ratio guages read any usefull information on whether im running rich or lean?

casio

i think what someone said about the air/fuel gauge is that it itself is not so reliable, but it could be useful as a reference. if your car runs fine and healthy, then you'll want it to normally run at that point on the gauge. i dont know, i'm not convinced. i'd like to see proof of one coming in handy, but thats me.