How much can weak gas effect performance?
Thread Starter
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
How much can weak gas effect performance?
Last fill up she took about 10 gallons, filled up at a place where I don't usually buy gas, but it was a Marathon brand on the pumps at this convenience store, and of course I pumped their 93 grade.
Since then, it feels like she's pulling a trailer. I mean, throttle response is noticeabley down and pull feels sluggish. Its like the difference between driving around solo by yourself and driving around with a 350lb friend in the right seat.
She runs smooth and all, so I'm wondering if I got a load of 87 instead of 93 ?
Since then, it feels like she's pulling a trailer. I mean, throttle response is noticeabley down and pull feels sluggish. Its like the difference between driving around solo by yourself and driving around with a 350lb friend in the right seat.
She runs smooth and all, so I'm wondering if I got a load of 87 instead of 93 ?
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Weak gas??? Like watered down? The ONLY advantage to higher octane is in it's ability to resist knocking. If your engine isn't knocking, or your ECM isn't receiving knock counts from the ESC, the the gasoline isn't slowing you down. As a matter of fact lower octane gasoline burns faster and will give a small increase in power.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
A thousand and one things. Do you have any codes set? The best bet is to follow the trouble shooting charts in your HELMS.
It's not knocking? You are getting no knock counts? The timing is propertly set? The fuel pressure is proper?
RACE ON!!!
PS. Forget the timing, I just noticed it's an LT engine. Hows the opti?
It's not knocking? You are getting no knock counts? The timing is propertly set? The fuel pressure is proper?
RACE ON!!!
PS. Forget the timing, I just noticed it's an LT engine. Hows the opti?
Last edited by CFI-EFI; Apr 9, 2005 at 09:18 PM. Reason: PS.
Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
Originally Posted by CFI-EFI
If your engine isn't knocking, or your ECM isn't receiving knock counts from the ESC, the the gasoline isn't slowing you down..
if your engine isn't knocking that either means your knock sensors/ECM are working properly or the gas is ok...
If they are working ok, it means they are taking out spark advance which means loss of power??????
The only way to know for sure is with a scanner, you can't just listen for knocking.....
BTW Toyota says on some of their engines you can run either regular or premium but premium will give you more power.....for a fact this was in my 99 Sienna owners manual and a friends 2004 Corolla manual......and Toyota further suggests not to switch back and forth...my quess is this relates to the ecm "learning" how much spark advance it can use without knocking...
A car mag article a year or so ago talked about lost horsepower, same thing, if your car is getting knock counts and reducing advance you are lossing hp....
I do agree that just changing to premium on most low compression cars doesn't really result in any power gains, unless it allows more spark advance..
Again I don't really know this, but it is what I think...
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
You are right. If there are knock counts, pulling timing, and the higher octane suppresses those counts, the power will be higher with less or no knock counts. Otherwise, lower octane gas produces MORE power than the higher octane gases. That is why I asked if was experiencing knock or was getting knock counts. However, he reports no diagnostics, and it could be ANYTHING causing the lack of power.
RACE ON!!
RACE ON!!
Thread Starter
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Datamaster log shows no timing retard and knock counts only happen when cranking and start up (normal for knock counts to spike at start up). Plus, she has an LT4 knock module plugged into the PCM.
I'm down to 9 more free logging sessions left on my Datamaster program now
Hell, I don't know what is going on. Same weather conditions today, and after fiddling around and running it without the vac line connected to the fuel pressure regulator (plugged the vac line while it was disconnected, of course) then re-connecting the vac line, she seems her old self again.
I posted another thread about smelling a pretty distinct odor of raw fuel at the nipple of the vac line that connects to the FPR (on the FPR end of course). But there's no actual fuel in the vac line that I can tell.
I'm getting suspicious of my FPR, but I hate to buy a fuel pressure gauge just for a one time deal trying to diagnose a weak FPR
Hate to just throw a new FPR at it though
I'm down to 9 more free logging sessions left on my Datamaster program now
Hell, I don't know what is going on. Same weather conditions today, and after fiddling around and running it without the vac line connected to the fuel pressure regulator (plugged the vac line while it was disconnected, of course) then re-connecting the vac line, she seems her old self again.
I posted another thread about smelling a pretty distinct odor of raw fuel at the nipple of the vac line that connects to the FPR (on the FPR end of course). But there's no actual fuel in the vac line that I can tell.
I'm getting suspicious of my FPR, but I hate to buy a fuel pressure gauge just for a one time deal trying to diagnose a weak FPR
Hate to just throw a new FPR at it though
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Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
The gauge you can reuse. It is an investment in future diagnostics and repairs. If you buy an unneeded pressure regulator, it's just money down a rat hole. Since you're getting no knock counts, the problem isn't with the octane of the gasoline.
RACE ON!!!
RACE ON!!!
Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
Originally Posted by Lone Ranger
Last fill up she took about 10 gallons,...........got a load of 87 instead of 93 ?
But since you are not getting any knock counts or timing adjust, I also doubt if octane is the problem........
Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
Originally Posted by LT4BUD
A car mag article a year or so ago talked about lost horsepower, same thing, if your car is getting knock counts and reducing advance you are lossing hp....
:
:
http://www.hotrod.com/techarticles/72498/
....I think it says highest octane made the most power???