I heard that if you use higher octane gas, it can advance your timing. is that true?

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Steve
88 Firebird TBI(WS6),TH700R4 - Open Element, Cat Delete, K&N filter 14*4 element, Flowmaster Catback Exhaust, 180 Stant thermostat, Accel cap and rotor

 

That is always a general rule but you only need to go up in octane if you have high compression and/or AL heads!!! Otherwise, it is a waste of money. IE, you WILL NOT MAKE ANY MORE POWER THAT WAY if you have mellow/OEM CR.


High octane gas just burns slower, to make a long story short, and is more resistant to high-CR preignition.

[This message has been edited by FastBroker (edited May 31, 2001).]

 

then why does my car pull harder when i use high octane fuel?

 

It could (probably) mean that you have your timing advanced too far for regular fuel and the ECU is retarding the timing because of sensed knock. Retarded timing = loss of power.

When you put in Super, the knock diappears and the ECU allows full advance and therefore, more power.

A scan tool will allow you to check for knock counts. The ECU retards A LOT, too, like 4-8 degrees, depending on the PROM, so that's why you have less power. If you are noticing an improvement SOTP with Super, you might want to check your initial timing setting and/or check for knock counts.


You could also have high compression or some carbon specs or other problem in a combutsion chamber that causes a HOT SPOT which can also cause preignition, which will also be cured by High octane fuel.

[This message has been edited by FastBroker (edited June 01, 2001).]

 

These days I would do anything I could NOT to use higher octane fuel, I have tried it on my RS at the track and 87 octane with 3 degree's advanced timing runs as well as 92 octane with more timing.

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92 Camaro RS 5.0 5-Speed
14" Open Air Cleaner
3.08 Posi-trac
Edelbrock TBI Intake
Crane cam
Ported & polished stock heads 3 angle valve job
HyperTech Chip
SLP Headers (Ceramic Coated)
UltraFlo cat-back exhaust

74 Dodge Dart Sport 360 (11.2 1/4 mile)

2000 Dodge 1500 Ram Sport

 

Just remember that when your doing a valve job. The premium fuels tend to use a different additive package, and burn with less carbon. Carbon sitting on the valve and valve seat worsen the heat transfer, and then burn the valve alot sooner.

On some cars, you'll more then make up the difference in price, with better mileage.

 

Well if I did my math right at 20 MPG you will spend about $1500 more for premium fuel over 150,000 miles, I could do several valve jobs for that, and at least on my engine I rebuilt the heads at 100,000 miles just because I wanted to do a three angle valve job on them and port and polish for more flow, and my valves didn't have any heavy buildup on them, just a very thin smooth coating of carbon, but I do use fuel injection cleaner every 5000 miles or so. And as far as getting better mileage with premium fuel that is only the case if the engine has high-compression and was made to burn it. Lower octane has more BTU's per gallon and will make better power and mileage if the engine can run it without pinging.

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92 Camaro RS 5.0 5-Speed
14" Open Air Cleaner
3.08 Posi-trac
Edelbrock TBI Intake
Crane cam
Ported & polished stock heads 3 angle valve job
HyperTech Chip
SLP Headers (Ceramic Coated)
UltraFlo cat-back exhaust

74 Dodge Dart Sport 360 (11.2 1/4 mile)

2000 Dodge 1500 Ram Sport

 

Hey Dart.Are we talking swirl port heads here? Because I was woundering if it would be worth it to port mine.I'm going to put a intake and a LT1 cam in soon,and I was toying with the idea of pulling the heads and trying to remove the restriction in the intake ports.Also do a intake gasket match while I was at it.I'm not building a strip car,just somthing to have fun with driving back and forth to work.
Anybody tryed to improve these squirel port heads?
PS I dont want to buy heads dedicated to a 305 because if I have this car long enough it will have a 350,so lets dont even go there.I've ported heads before and dont mind the work.I just dont know if it would be worth it on these heads.

[This message has been edited by JokerRS (edited June 02, 2001).]

 

These are my current mods.

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92RS LO3
ultimate TBI mods
open air element
Hooker headers
3"cat back
posi with 3.42 gears

 

JokerRS, you will see some improvement by porting the stock heads, I didn't try to grind away the part that causes the swirl and the restriction but I did grind it down some and do a three angle valve job, gasket matched the ports. And to be honest I don't know how much this helped because I added most of my other mods at the same time, but with the head work,intake,cam and headers it runs like a small chevy should run now. I haven't been to the track with it but I have beat several Mustang GT's and Z28's at the stoplight,along with most others that have wanted to run me.

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92 Camaro RS 5.0 5-Speed
14" Open Air Cleaner
3.08 Posi-trac
Edelbrock TBI Intake
Crane cam
Ported & polished stock heads 3 angle valve job
HyperTech Chip
SLP Headers (Ceramic Coated)
UltraFlo cat-back exhaust

74 Dodge Dart Sport 360 (11.2 1/4 mile)

2000 Dodge 1500 Ram Sport