Focus Fanatics Forum banner

1 - 20 of 36 Posts

·
Shot me 3 deer!!!
Joined
·
9,247 Posts
Discussion Starter #1
well, its not mine, i wouldn't do that. but my buddies day has a early 2000's pontiac GTP w/ the blower on it. 104k miles. he said his buddy told him that it was ok to run 87 in it after a while cause as it lost compression it would be safe. to me this sounded like a flat out lie. maybe in theory, but how much compression would you have to lose? lol anyways, w/ gas prices, he's been doing it FOR A WHOLE YEAR! lol, i think he's nuts. i hear no knock, but it could be something like the J&S could pick up. anyways, is this safe? my first thought is HECK NO. but when it comes to tuning, there could be something i'm overlooking. i mean, i know the computer can compensate on timing a bit, but can it truly compensate for 87? also, he doesn't hit WOT very much at all. but still, its not something i'd EVER do in like the SVT or any other performance car!

What do you think?
 

·
Registered
Joined
·
431 Posts
- Too cheap to pay .20-.30 cents more per gallon for premium gasoline

- Taking out loan to rebuild engine because of detonation damage.............priceless!.
 

·
Registered
Joined
·
1,565 Posts
Depends on what it was tuned for. If it was tuned for high octane then putting low octane is too risky in my book. You are losing power due to timing. If its not knocking then it is likely ok, but still not advised.
 

·
Registered
Joined
·
11,906 Posts
I think someone is a dumb ass for telling him he can run 87 octane... and I also think that someone else is a dumb ass for even remotely thinking he could be right........
 

·
Aurelius Pardus
Joined
·
26,535 Posts
well besides the fact that it states to use 91 octane or higher.... and that boost is boost
. the only question I need to ask is if he is hard on the car and gets into boost a lot or does he take it easy?

if the latter then its fine. I've run my car on 87 a few times and didn't boost it.

then again mine has a 7.8:1 cr and the gtp has an 8.5:1 cr.
 

·
Banned
Joined
·
210 Posts
You can easily tune for 87, there are factory forced induction vehicles that run on 87 just like that.

Something I'd do in an N/A-T Focus? Hell no.
 

·
Shot me 3 deer!!!
Joined
·
9,247 Posts
Discussion Starter #7
he's not tuned. he just doesn't hit HARD boost. he likes to hear the SC every once in a while, but around like 2500 rpm. he doesn't hit high boost. but i thought his buddy was a moron too. when he was telling me this, i was surprised he didn't blow it!
 

·
Shot me 3 deer!!!
Joined
·
9,247 Posts
Discussion Starter #8
are you calling me a dumb ass john? lol, cause i didn't think he was right! lol
 

·
Boost Addict
Joined
·
2,628 Posts
If hes on the stock tune the car might recognize the lower octane and limit the engine accordingly; really don't know much about the car though. Kinda like what the Thunderbird Turbocoupe ECU does when it sees lower octane fuel (Limits boost)

Or he has just been really lucky to not blow the motor; driving easy probably helps too. Its only a couple dollars more to fill up a car with premium fuel; helluva lot cheaper than replacing an engine....the premium fuel is cheap insurance if you ask me.

I would never run 87 in any type of forced induction car; but thats just me. My ST only gets 93 and the '86 Merkur only gets 93...nothing less.
 

·
Shot me 3 deer!!!
Joined
·
9,247 Posts
Discussion Starter #10
thats exactly what i told him. but as it being a roots type blower, how can you limit boost?? i don't think its possible, but i told him he wasn't being smart. but i've never heard of a car being tuned for 91 and able to compensate for 87
 

·
Shot me 3 deer!!!
Joined
·
9,247 Posts
Discussion Starter #11
i did the research on the car. apparently, crusing under 40 mph and staying 100 % out of boost, the KR system doesn't detect knock. however, 1 psi of boost and it starts to retard pretty good. and i was in the car yesterday and he hit boost at 3500 a few times yesterday. so i know he's damaging the engine. i told him to completely stop using 87. but there have been people that have got away w/ 87.
 

·
Registered
Joined
·
11,906 Posts

·
Boost Addict
Joined
·
2,628 Posts
but as it being a roots type blower, how can you limit boost??
Good question. May not be able to. Could just pull major timing. Don't know if there would be any type of bypass valve on it somewhere that could vent all the boost [dunno]

I may ask a good friend who was into GTPs for awhile about this to see if he knows.
 

·
Boost Addict
Joined
·
2,628 Posts
From my friend (former GTP owner and enthusiast)....

known plenty of guys put low octane in the gtp's and they start knocking and it rips the motor apart. The ecu's are tuned for high octane gasoline's, but people have been able to flash the ecu down to a lower octane tune and it solves the knock. but no the ecu just assumes its always running high octane.
 

·
Premium Member
Joined
·
3,617 Posts
My Twin turbocharged truck runs on 87....
 

·
Shot me 3 deer!!!
Joined
·
9,247 Posts
Discussion Starter #16
yes, but ur tuned for it. he's not.
 

·
Registered
Joined
·
81 Posts
This has been suggested earlier, but if the factory tune allows for 87 octane at reduced performance levels then it'd be perfectly safe. Ie. the newer Mazda CX-7 is a turbo engine that performs on premium but will handle 87 safely and de-tune accordingly. That being said I would be pretty impressed if GM was doing it way back in the day! Looks like someone's gonna have to dig through some old articles to get a solid answer!
 

·
Registered
Joined
·
397 Posts
I asked the instructor for the ecoboost course I took and he said the ecu's are programmed to adjust timing Accordingly via the knock sensor. If I recall he said "you can run this engine all day every on 87, just at the cost of reduced power"
 

·
Premium Member
Joined
·
3,617 Posts
I asked the instructor for the ecoboost course I took and he said the ecu's are programmed to adjust timing Accordingly via the knock sensor. If I recall he said "you can run this engine all day every on 87, just at the cost of reduced power"
Not to get this thread off topic, but the EB engine, at least for the trucks are designed to run 87. When you tow or under high load situations they say to run higher octane.
 

·
Registered
Joined
·
431 Posts
The owners manual also states the 87 octane could lower the performance. Who in the right mind buys a turbocharged car or truck, then cheaps out and uses 87 octane. You don't get the full performance that you paid for on 87 octane.
 
1 - 20 of 36 Posts
Top