Grand prix GTP 1999 S/Ced running off 87 octane mods - Page 4 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


General GM Chat When starting new posts, please specify YEAR, MAKE, MODEL, ENGINE type, and whatever modifications you have made. Chat about all things GM (and related cars). Off-topic stuff should be in the Lounge, and all Model specific mechanical problems should be posted in the proper forum.

Reply
 
 
 
Thread Tools Search this Thread
Old 11-15-2006, 10:24 AM   #31
Senior Member
Posts like a Camaro
 
Join Date: Dec 2005
Location: Clovis, CA
Posts: 851
Thanks: 0
Thanked 0 Times in 0 Posts
MACDRIVE is on a distinguished road
Default

Quote:
Originally Posted by ChaseSmith

Now I have her trained, all of my cars except for my Sonoma take 93, but she even puts 93 in that now
Yeah... she sure fixed you didn't she? LOL!!!
MACDRIVE is offline   Reply With Quote
Old 11-15-2006, 01:29 PM   #32
Junior Member
Posts like a Ricer Type-R
 
Join Date: Nov 2006
Posts: 11
Thanks: 0
Thanked 0 Times in 0 Posts
CraigTNelson is on a distinguished road
Default

I dont know about running 87 octane it sounds like a bad idea especially with the 3.4 pulley. I also have a 99gpgtp except with a full 3.25 inch pulley setup and I was getting tons of kr on 91oct. now I run stricktly 94oct.
CraigTNelson is offline   Reply With Quote
Old 11-15-2006, 02:28 PM   #33
Senior Member
Posts like a Corvette
 
Join Date: Jul 2004
Location: Winnipeg, Manitoba, Canada
Posts: 1,445
Thanks: 0
Thanked 0 Times in 0 Posts
captainmiller is on a distinguished road
Default

If you have a problem paying for the normal high octane fuel you should look around for a gas station that sells high octane 10% ethanol blended. I pay the same same price as regular fuel and get 94 octane. I really wouldn't want to be the person who ends up buying this car. I just don't see how a car with those mods running 87 only has 4* at WOT on a 3.4.

There are ALOT of supercharged GM cars running around on 87. My friend works at a gas station and he tells me all the time of a 40 year old woman pulling up in a SSEi, GTP, GS, Ultra, etc., and asking for 87. He then tells her thier car requires premium and they think he is trying to sell them more expensive gas for profit, and they snap at him to fill it up with 87. Some people...
captainmiller is offline   Reply With Quote
Old 11-15-2006, 03:47 PM   #34
Senior Member
Certified Car Nut
 
Join Date: Oct 2003
Posts: 19,756
Thanks: 0
Thanked 0 Times in 0 Posts
1993 SLE is on a distinguished road
Default

Quote:
Originally Posted by captainmiller
There are ALOT of supercharged GM cars running around on 87. My friend works at a gas station and he tells me all the time of a 40 year old woman pulling up in a SSEi, GTP, GS, Ultra, etc., and asking for 87. He then tells her thier car requires premium and they think he is trying to sell them more expensive gas for profit, and they snap at him to fill it up with 87. Some people...
most are not modded
1993 SLE is offline   Reply With Quote
Old 11-16-2006, 10:45 AM   #35
Senior Member
Posts like a Northstar
 
Join Date: Apr 2004
Posts: 606
Thanks: 0
Thanked 0 Times in 0 Posts
Chinski is on a distinguished road
Default

Quote:
Originally Posted by willwren
There are many members here who may not understand. There are specific reasons supercharged cars, even in stock form, should run 91 octane minimum at all times. Those reasons are unique to supercharged cars and are unrelated to whatever reasons an Acura may or may not be required to.
I get the part about why to not compare an Acura to a Bonneville...but what are these unique reasons for a SC'd motor to run 91 that a NA motor does not have? I though it all boiled down to preventing knock, no matter what type of induction the motor has. I thought the only thing higher octane does is raise the flashpoint, thus combating pre-detonation.

There is a guy here running 89 in his GTP (because he also doesn't want to shell out the extra $1 per tank for premium), so if there is more that I can tell him than just that he is getting damage from knock, I would like to know.
Chinski is offline   Reply With Quote
Old 11-16-2006, 10:50 AM   #36
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

Non-forced induction motors that require premium are for the most part because of high compression.

We have high compression coupled with the compounding action of pre-heating the plenum charge by compression (supercharger). It makes it worse for us.

Making it even WORSE is running slightly lean for a mechanical reason (FPR, pump, filter, whatever) and getting knock. That usually relates to BOOM under more than stock boost levels. If not BOOM, then lesser damage more widespread.

A stock Series 1 L67 will run about 13:1 effective compression (8.5:1 @ 8psi)
Stock S2'* will be similar. Each step in pulley size you take makes it FAR worse.

I'm somewhere in the neighborhood of 16.5:1 compression under boost on the Zilla right now.
willwren is offline   Reply With Quote
Old 11-16-2006, 02:46 PM   #37
Senior Member
True Car Nut
 
Join Date: May 2003
Location: Holt, MI & Lima, OH
Posts: 3,022
Thanks: 0
Thanked 0 Times in 0 Posts
dbtk2 is on a distinguished road
Default

Quote:
Originally Posted by Chinski
I get the part about why to not compare an Acura to a Bonneville...but what are these unique reasons for a SC'd motor to run 91 that a NA motor does not have? I though it all boiled down to preventing knock, no matter what type of induction the motor has. I thought the only thing higher octane does is raise the flashpoint, thus combating pre-detonation.

There is a guy here running 89 in his GTP (because he also doesn't want to shell out the extra $1 per tank for premium), so if there is more that I can tell him than just that he is getting damage from knock, I would like to know.
You are correct that running higher octane fuel boils down to combating pre-detonation by running a fuel that takes higher temps to ignite. That is the whole point of it. However, with boost not only do you get much higher compression, but you get the heat that the power adder made while compressing the air as well. So its a lot greater effect than just high compression because you're adding the extra temps in there as well. If, in the Acura you mentioned, it were to predetonate with the premium fuel, not only are cylinder pressures not as high as ours, but temps are lower as well and its much harder to cause damage, not only that but it will be much harder to predetonate anyways.

Like willwren said, with boost our compression ratios are already a lot higher than "high compression" N/A engines. In my GP GT my effective compression ratio currently is ~17.7:1, combine that with the high temps my blower puts out and you'll see what we're talking about here. Obviously, running 87 octane in this situation probably wouldn't be the best idea. You can pull timing to make up for the extra heat, but that only works to a certain extent. With a tune, I'm sure his setup could be tuned so that he had no KR under most part throttle situations, and honestly they probably could pull enough timing that he'd have no KR either...but it would make more power if they just went back to a stock pulley.

However, as an example, in my STE I ran 87 octane gas on 14psi boost (18:1 effective compression ratio with the 9.2:1 compression) with 17 degrees of timing and running it very lean (~13.5:1 afr) without any issues. However, the only reason I was able to do this is because my build was built for a much larger turbo pushing much more boost, so with the turbo that was on the car 14psi was actually a little out of the efficiency range so it made no sense to run more boost than that. With my intercooler, cam, heads, compression setup, the 14psi with my tune was very doable. So basically this setup should've been capable (assuming the turbo could flow) of actually doing something closer to ~22-24psi boost, and because I was only running 14psi I was able to run the 87 octane. In the GTP'* situation, he is already running more boost than he should be with his setup.
dbtk2 is offline   Reply With Quote
Old 11-16-2006, 03:04 PM   #38
Senior Member
Posts like a Supercharger
 
Join Date: Oct 2006
Location: Warsaw, New York
Posts: 164
Thanks: 0
Thanked 0 Times in 0 Posts
anotherbonneville is on a distinguished road
Default

So does this mean if i run my car with 93 octain i can gain HP and Milage?
anotherbonneville is offline   Reply With Quote
Old 11-16-2006, 03:22 PM   #39
Junior Member
 
Join Date: Mar 2003
Location: Purgatory
Posts: 0
Thanks: 0
Thanked 0 Times in 0 Posts
vital49 is on a distinguished road
Default

Quote:
Originally Posted by anotherbonneville
So does this mean if i run my car with 93 octain i can gain HP and Milage?
Nope. You will gain nothing from it other than a lighter wallet which may make you go a tiny bit faster.
vital49 is offline   Reply With Quote
Old 11-16-2006, 03:30 PM   #40
DINOSAURUS BOOSTUS

Expert Gearhead
 
BillBoost37's Avatar
 
Join Date: Mar 2005
Location: Enfield, CT
Posts: 41,391
Thanks: 0
Thanked 0 Times in 0 Posts
BillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of light
Default

Quote:
Originally Posted by vital49
Nope. You will gain nothing from it other than a lighter wallet which may make you go a tiny bit faster.
IIRC other members with L27 and L36'* have mentioned seeing slight mileage gains from higher octane fuel.

SingsCountry1967 comes to mind, totally stock
BillBoost37 is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
off topic.........Grand Prix GTP question........ pumpedTSI Buick 7 04-23-2009 10:08 AM
92 S/Ced engine and trans into a 91 SSE FriendSSEI Performance, Brainstorming & Tuning 6 01-18-2009 05:58 PM
Octane Points (Octane Boost) bandit General GM Chat 2 08-28-2007 11:21 PM
1999 Grand Prix GTP price? brnvs General GM Chat 12 12-23-2005 10:47 PM
Need audio of flowmasters on a 1999 pontiac grand prix GTP killer_cr80r Lounge 1 09-01-2004 09:02 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 06:05 AM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.