It appears that our knock sensor is very conservative and sometimes determines normal engine noise and vibration as knock. The ECU then pulls timing which results in power loss. If you are not FI and always run premium fuel knock should not be an issue and we may gain power from unbolting it. On the other hand, if you were to experience knock I doubt it would hurt an NA motor.

Here are some quotes from Racing Beat's Site:

“We have also tested the knock sensor system and found that though it is good, it can cause minor problems. The sensor seems to detect normal engine vibrations as “knock” (pre-ignition), and because if this, the ECU retards the timing. Unbolting the knock sensor from the #2 rotor housing (do not disconnect it electronically - this will cause an ECU fault and retard the timing.) usually adds a small amount of power (often 1+HP) by eliminating the random, unnecessary retarding of ignition. Of course, if the engine should experience knock, your unbolted sensor will never know it- but cars ran for many years without these sensors and survived!”

Knock Sensor – “The reason for unbolting the knock sensor is that our testing has shown that the ECU sometimes randomly retards the ignition even when there is no actual detonation occurring. (Detonation - pre-ignition combustion of the compressed intake charge.) The difference is only 1-2 HP, but this is more than the differences we are looking for. We obtain more consistent test results by unbolting the sensor (but leaving it connected electronically so that it doesn't cause a fault in the ECU); thereby preventing it from feeling the vibration it mistakenly thought was detonation.”


Thoughts?

 

im remembering the thread where someone was looking for an "aftermarket kock sensor." we all had a good laugh about that.

 

you better be using high octane fuel, otherwise one series of knocks and it's goodbye apex seals

 

this is what some guys at our dyno day were saying might be happening to my car. it was pulling like 20-25hp less (142-144) than similarly configured cars (165) and then ran once much closer to the other guys (155). This was out of 6 pulls. I have new plugs, ignition coils, wires, and good compression.

do you think this could be part of the problem or is there something else i should look into?

 

Were these piston engine owners? The knock sensor is so bad on our car that is pretty much useless. You'd have to hit it with a hammer to get a reading.
Just to make you feel good,, you have less HP then my 4 Port AT.


I would say that the dyno may not be calibrated correctly.

 

nah, 8s. that's what's weird. even an 8 in stock trim did better than mine: 166...

 

That's till pretty low on the scale. I've seen mine range about 25 whp on different dynos on different days.
I've also seen a stock AT do 155 whp. While mine did 145 with intake exhaust and BHR coils and an Accessport. Some 8's just have more HP. I don't know why.

Try some injector cleaner in it. Se if that helps.

 

mine was well below the others and i have intake/catback exhaust/ap/bhr ignition..

i suppose this fails w/o pics though.. i'll try to scan the graphs.

 

Has MM done the full range of tuning on your AP? Or are you guy's still working on it?

 

we did the first part on the dyno in seattle and he told me the coils were bad so i got the bhr ones and recently got those working well so i put it on the dyno again. my plan is to datalog again now and send that in for another map to see if it helps at all.

i can't scan now, scanner's not working, so i'll get them up tomorrow.

 

I'll remind him tomorrow when he gets back in town. Just do the 11 Deadly questions and submit the logs.
I think you'll have better results when the car has the proper tune on it. I hope.

 

Dondo's numbers are from a Mustang dyno. We had 3 8's dyno back to back to back with my car being the 3rd car. I pulled 163 with new OE coils and plugs. I also have RB intake and Corksport exhaust. What is a bit interesting is Dondo's graph. He peaked earlier than the 3 8s that pulled in the 160s where others still climbed.

Note: I believe we had 6 8s get on the dyno. 3 in the 160s, 1 157, 2 in the 140s.

 

That is still some low numbers for all the cars. I suppose it's just the Mustang dyno.





But I like it. It means there are 6 MT RX8's out there with less HP than my 4 Port AT.

 

haha...what are you mods? If you are spraying or FI then it does not count

 

I can't remember what Dondo's graph looked like but we have similar mods and similar results.

Here is mine for comparison.

 

^ your curve goes dead at around 7000, looks like the APV may not be opening

 

Would that throw a CEL?

 

Dondo's graph did that as well. The other 8s keep climbing where theirs start to fall off.

 

here are mine:
SKMBT_C35309052414060.pdf

 

submitted today.
thanks!

 

only if it's stuck in the open position

 

But if it completely stops operating it think's everything is A-OK? That seems odd.

I'll have to check to see if the motor that controls the APV is operating correctly.