Random Little Question Thread
#9091
I'm pretty sure both coupe and sedan have the exact same engine with the exact same compression ratio which in turn means both cars require the exact same fuel. ![39](https://g35driver.com/forums/images/smilies/39.gif)
Thanks buddy, you have answered me with a great deal of information yet again. Now to just clear things up even further, so 94 octane fuel is too high of an octane and may actually reduce power to my untuned '04 G35??
Also the Osirus tune CAN increase compression ratio because our engines have electronically controlled cam phasing meaning my car can be tuned to run the 94 octane??
Thanks again
![39](https://g35driver.com/forums/images/smilies/39.gif)
While you are correct that compression ratio is a mechanical value it's not the only determining factor in actual compression. Two engines with the same compression can have different cylinder pressure readings, which in reality in a more precise measurement of compression. By changing the lobe spacing and valve overlap the camshafts affect compression, since the VQ uses electronically controlled cam phasing a tuner can effectively change the compression ratio.
The other thing to consider is timing, higher octane fuels allow for more timing without detonation, again this is a computer controlled function, you have no idea when the computer pulls timing but when it does it reduces power output. A lightly modified VQ with a stock tune will detonate, when we dyno’d my car it actually went into the high detonation map the first pull we made over 5000 rpm, with 91 octane fuel.
The other thing to consider is timing, higher octane fuels allow for more timing without detonation, again this is a computer controlled function, you have no idea when the computer pulls timing but when it does it reduces power output. A lightly modified VQ with a stock tune will detonate, when we dyno’d my car it actually went into the high detonation map the first pull we made over 5000 rpm, with 91 octane fuel.
Also the Osirus tune CAN increase compression ratio because our engines have electronically controlled cam phasing meaning my car can be tuned to run the 94 octane??
Thanks again
![Biggthumpup](https://g35driver.com/forums/images/smilies/biggthumpup.gif)
#9092
So I've been doing a lot of reading and my eyes are starting to hurt. I noticed that I am fortunate to have 94 octane available at almost every gas station here in Toronto as opposed to other members from other locations who only can get 91 octane.
Intially I thought higher octane = more power. After reading what higher octane actually is, it seems 94 might be overkill for my untuned '04 G35 Sedan and might actually be reducing power as it is harder to ignite and slower burning than the recommended 91 octane for the car.
So my question would be, is my theory correct and could I actually be losing power using the higher 94 octane??
Also if I got an Osirus tune, does that also change the compression ratio and can make better use of the 94 octane??
Thank you in advance to who ever answers this question clearly and in great detail.![Bowdown](https://g35driver.com/forums/images/smilies/bowdown.gif)
Intially I thought higher octane = more power. After reading what higher octane actually is, it seems 94 might be overkill for my untuned '04 G35 Sedan and might actually be reducing power as it is harder to ignite and slower burning than the recommended 91 octane for the car.
So my question would be, is my theory correct and could I actually be losing power using the higher 94 octane??
Also if I got an Osirus tune, does that also change the compression ratio and can make better use of the 94 octane??
Thank you in advance to who ever answers this question clearly and in great detail.
![Bowdown](https://g35driver.com/forums/images/smilies/bowdown.gif)
There is a way where a high octane fuel can become harmful to your motor, but your motor will still be able to put down much more power with it, and you will never have to worry about that problem at any commercial pump or gas station... At least not until they start carrying 112 ethanol.
Last edited by dofu; 05-18-2013 at 01:38 AM.
#9094
Rattle from back of G35. Solutions?
I have this rattle, and found this video on youtube that exactly sounds like the rattle that I have
It comes from the back of the car, and usually occured when going on a bumpy road, but now it's rattling more frequently. What can I do about it? Is it the axis? Something else? It's becoming increasingly more annoying.
Please help
It comes from the back of the car, and usually occured when going on a bumpy road, but now it's rattling more frequently. What can I do about it? Is it the axis? Something else? It's becoming increasingly more annoying.
Please help
#9095
94 octane will not hurt hp output. If anything, it allows your motor to make more power. A higher octane does not necessarily make more power by itself even though you will fell a difference, but that's because your ECU is making adjustments by itself. All you really need to know is that higher octanes help prevent detonation better so you can make more power. This basically allows you to squeeze more fuel into the cylinders, and more gas = more power. For example, we only have 91 out here, but a map for 100 octane gave me over 10 hp to the wheels (something like 18hp... I don't quite remember anymore). The reason for this is because the 100 octane allowed us to tune my car more aggressively than 91 octane would allow.
There is a way where a high octane fuel can become harmful to your motor, but your motor will still be able to put down much more power with it, and you will never have to worry about that problem at any commercial pump or gas station... At least not until they start carrying 112 ethanol.
There is a way where a high octane fuel can become harmful to your motor, but your motor will still be able to put down much more power with it, and you will never have to worry about that problem at any commercial pump or gas station... At least not until they start carrying 112 ethanol.
I'm not sure if I misread your reply but you said that the ECU makes adjustments by itself and adapt to the 94 octane? I thought it just prevents pinging in the engine not increase compression ratio....
![Dunno](https://g35driver.com/forums/images/smilies/dunno.gif)
I have this rattle, and found this video on youtube that exactly sounds like the rattle that I have
Rattle in G35 - YouTube
It comes from the back of the car, and usually occured when going on a bumpy road, but now it's rattling more frequently. What can I do about it? Is it the axis? Something else? It's becoming increasingly more annoying.
Please help
Rattle in G35 - YouTube
It comes from the back of the car, and usually occured when going on a bumpy road, but now it's rattling more frequently. What can I do about it? Is it the axis? Something else? It's becoming increasingly more annoying.
Please help
![7](https://g35driver.com/forums/images/smilies/7.gif)
(I can't believe you have the same name as me lol.....)
#9096
![Question](https://g35driver.com/forums/images/icons/icon5.gif)
So I have a crawford intake plenum. It came on my car when I bought it. So I read crawfords site and it says the slanted stock plenum restricted airflow to the front cylinders. The crawford plenum is designed to have equal airflow distributed to all the cylinders.
Ok, so I ordered the isothermal motordyne 5/16. It should be here Monday. My question is do you think the spacer will be a waste? I'm assuming the purpose of the spacer is to take care of the restricted airflow problem. I know that it has other benefits too with the cooling of the plenum. So let me know what you think.
I don't know if I already have an mrev2, I figure id find out once I put the spacer on. If I didn't have it, id buy it.
Ok, so I ordered the isothermal motordyne 5/16. It should be here Monday. My question is do you think the spacer will be a waste? I'm assuming the purpose of the spacer is to take care of the restricted airflow problem. I know that it has other benefits too with the cooling of the plenum. So let me know what you think.
I don't know if I already have an mrev2, I figure id find out once I put the spacer on. If I didn't have it, id buy it.
#9097
Registered User
iTrader: (18)
^Buying the spacer probably was a waste in your case, or you could just not use the Crawford.
This is what the MREV2 looks like: https://g35driver.com/forums/2540400-post16.html
This is what the MREV2 looks like: https://g35driver.com/forums/2540400-post16.html
The following users liked this post:
License2chill (05-18-2013)
#9098
^ Well I figured if my untuned engine can't compress the higher octane enough then I'm just drowning it with the harder to ignite high octane fuel.
I'm not sure if I misread your reply but you said that the ECU makes adjustments by itself and adapt to the 94 octane? I thought it just prevents pinging in the engine not increase compression ratio....![Dunno](https://g35driver.com/forums/images/smilies/dunno.gif)
^ That's a new gen G35 you're in the wrong part of the forum.![7](https://g35driver.com/forums/images/smilies/7.gif)
(I can't believe you have the same name as me lol.....)
I'm not sure if I misread your reply but you said that the ECU makes adjustments by itself and adapt to the 94 octane? I thought it just prevents pinging in the engine not increase compression ratio....
![Dunno](https://g35driver.com/forums/images/smilies/dunno.gif)
^ That's a new gen G35 you're in the wrong part of the forum.
![7](https://g35driver.com/forums/images/smilies/7.gif)
(I can't believe you have the same name as me lol.....)
#9099
I have this rattle, and found this video on youtube that exactly sounds like the rattle that I have
Rattle in G35 - YouTube
It comes from the back of the car, and usually occured when going on a bumpy road, but now it's rattling more frequently. What can I do about it? Is it the axis? Something else? It's becoming increasingly more annoying.
Please help
Rattle in G35 - YouTube
It comes from the back of the car, and usually occured when going on a bumpy road, but now it's rattling more frequently. What can I do about it? Is it the axis? Something else? It's becoming increasingly more annoying.
Please help
^ Well I figured if my untuned engine can't compress the higher octane enough then I'm just drowning it with the harder to ignite high octane fuel.
I'm not sure if I misread your reply but you said that the ECU makes adjustments by itself and adapt to the 94 octane? I thought it just prevents pinging in the engine not increase compression ratio....![Dunno](https://g35driver.com/forums/images/smilies/dunno.gif)
I'm not sure if I misread your reply but you said that the ECU makes adjustments by itself and adapt to the 94 octane? I thought it just prevents pinging in the engine not increase compression ratio....
![Dunno](https://g35driver.com/forums/images/smilies/dunno.gif)
#9100
That could be! Could you specify where/what metal piece it is? And what can I do about it?
Thanks!!
#9102
It's right before the muffler. If you get down behind the cat, it's a metal piece directly on the other side of the muffler. It has a triangular shape from the side, and it looks almost like another muffler-like canister from below. You can either tighten it or remove it altogether.
#9103
Is my battery going dead
Well im a new driver but have a noob question but want to make sure of this problem
Well yesterday I had my key in the ignition for 10 seconds and my battery didnt die but would not turn over to start
All day yesterday it was fine than a half hour ago 24 hours after the problem never expiernce e this before I go right into my car after work work and put my key into ignition wouldn't turn on.
Is my battery going dead I think so please help because if so I need to buy a new one tomorrow
Well yesterday I had my key in the ignition for 10 seconds and my battery didnt die but would not turn over to start
All day yesterday it was fine than a half hour ago 24 hours after the problem never expiernce e this before I go right into my car after work work and put my key into ignition wouldn't turn on.
Is my battery going dead I think so please help because if so I need to buy a new one tomorrow
#9105