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Posted by: Neal Sep 8 2003, 01:24 PM

I wanted to know for a engine developed in the 70's and rebuilt in the 2000's do you think 4 octane points higher makes a difference on how the engine performs as a daily driver ?




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Posted by: redshift Sep 8 2003, 01:27 PM

Yep! 2.0s hate premium, runs cold.


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Posted by: aufaber Sep 8 2003, 02:24 PM

OH! That poor F4i!

-Aaron G.

Posted by: tat2dphreak Sep 8 2003, 02:28 PM

is that true for 1.7/1.8L also?

Posted by: redshift Sep 8 2003, 02:45 PM

I don't remember the 1.8 not liking it.

Injected 2.0s and 1.7s I have had hate it. If it's hot outside, they flutter at idle, almost like an overheat, and the idle drops 300 or so, and can cause all kinds of shit warm starting.

We have some of the best quality gas you can buy in the states here, you have even better maybe.

Dense winter air is another story, make you wish you had 104 octane, and 4' velocity stacks.




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Posted by: Neal Sep 8 2003, 02:52 PM

My car has webers and I live in Seattle, would premium help ?, it's a 2.0 with euro pistons and a mild factory cam.

Posted by: redshift Sep 8 2003, 03:03 PM

I don't know.

Washington has boutique fuels, like California?

Test out only a half a tank, or even less, won't hurt you, with carbs, and somewhat milder weather than us poor folks in the killing zone.


i hate heat



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Posted by: ChrisReale Sep 8 2003, 03:14 PM

Premium is the expensive shit, right? Thats all I put in mine....

Posted by: tat2dphreak Sep 8 2003, 03:42 PM

I used premium in my carbbed 1.7... and I wonder if that's one of the many reasons it didn't idle smooth...

Posted by: p914 Sep 8 2003, 04:10 PM

Why is it that 2.0s don't like premium? It ignites at a lower temp.

Posted by: p914 Sep 8 2003, 04:12 PM

WA state has good gas and is regulated. Oregon gas is questionable depending on the station.

Posted by: aufaber Sep 8 2003, 04:34 PM

Octane is a rating of resitance to ignition.

http://auto.howstuffworks.com/question90.htm

The higher the octane the harder to ignite.

-Aaron G.

Posted by: redshift Sep 8 2003, 04:44 PM

Our engines are as hot as fire.

Another thing, you are tossing money away if your local fuel is good, and you are fueling with a higher octane fuel, and I am telling you, it's not a good thing, and you can feel the difference in 87-91-93, nice, flutter, flap like a bird.

Early 1.7 used high test though, did they not?

It's not just something you decide to do one day, engineers worked at all this, they spec the rating in the build, just like cam duration, and valve clearance.

You can change octane, I don't know what the environmental changes to the equation, but your plugs must be in another temp range than stock, and gapped different.

There you go, that is what the difference feels like, bad gap, and that is how you take it up, bad gap.



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Posted by: p914 Sep 8 2003, 04:47 PM

I use a colder plug because I have electronic ignition and the gap is .038. A little wider than normal.

Posted by: Andyrew Sep 8 2003, 04:53 PM

Redshift, your saying use the cheepo stuff?

Andrew

Posted by: redshift Sep 8 2003, 05:04 PM

Look in your owners manual.



And with that, I go nappy.


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Posted by: Andyrew Sep 8 2003, 05:43 PM

Hehe, I have about 5 workshop manuals, but not the factory owners, keeping my eye on ebay for a nice one cheap..

Andrew

Posted by: redshift Sep 8 2003, 05:49 PM

and I can't sleep so...


1.7 (early) 98 RON

1.7 (late) 91 RON

2.0 91 RON

be right back..


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Posted by: redshift Sep 8 2003, 05:52 PM

Googlectomy! There is the whole thing in a page. -whew- (popups crap!) Hold on..

http://www.azcentral.com/arizonarepublic/wheels/articles/0828wheels28click.html


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Posted by: Bleyseng Sep 8 2003, 06:05 PM

Hmm, thats not what I have read before. DD posted a bunch of stuff before of how the ratings are different and how to translate them for todays fuel. I have used regular and hitest in my 2056 engine. Seems to like the good stuff much better, runs smoother.

Geoff

Posted by: Aaron Cox Sep 8 2003, 07:11 PM

you cant use a factory FI cam with carbs. they run like crap apparently....

Posted by: PatW Sep 8 2003, 07:15 PM

Union 76 sells 100 Octane Unleaded here in San Jose right out of the pump.
My 1.7 likes it.

Pat

Posted by: swood Sep 8 2003, 07:25 PM

premium is going for a premium down here right now, almost 2.50/gal.

Posted by: ArtechnikA Sep 8 2003, 07:26 PM

plus or minus a little, add 5 to the (RON+MON)/2 (US pump number)to see the ROZ number called for in the owner's manual.

early 1,7's had an 8,7:1 compression ratio (IIRC) -- later cars had less (!).

my car's owner's manual calls for premium and that's what i'm using.

the left side loves it, the right side hates it, my guess is there's something else going in ...

Posted by: redshift Sep 8 2003, 07:43 PM

I dunno why it so different for everyone else. I've had at least one 914 since 82, and this has always been my experience, except for carbs, oh... and I don't remember the 1.8.



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Posted by: p914 Sep 8 2003, 07:45 PM

according to PP spec sheet, my 2.0 should be running 91 RON. It does run noticeabley smoother with the premium. Occasionally I add in the 104 octane boost. Combined with electronic ignition and wider gap, there is a peppier response.
http://www.pelicanparts.com/914/technical_specs/914_20_tech_specs.htm

I ain't no major mechanic but have worked my way through a number of issues that have come up with my car. I thank my local porsche mechanic (a former 914 racer) and some of the guys here and on PP and Rennlist for insight.

Posted by: kdfoust Sep 8 2003, 08:04 PM

I put prem in my 72 1.7. Never tried regular or medium (what's the middle grade called anyway?). I've been assuming that the engine would detonate it's self to pieces on regular.

Here's a piece for the puzzle: I used to have a '97 F150 which ran "better" on premium but got worse fuel economy. I repeated the experiment over and over switching between reg and prem. Reg~16 Prem~13. I always assumed that the engine controls ran the timing with more advance (less propensity to knock with prem) on premium thus yielding slightly better performance but worse mileage. I wasn't really "into" the truck so I never bothered to investigate the engine control system to verify that idea. How's that apply here? Simplistically would you set the timing slightly retrograde from the spec if you want (insist) to run reg - right?

Have fun,
Kevin

Posted by: redshift Sep 8 2003, 08:08 PM

87 plain old pump gas is roughly 92 RON.

So..




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Posted by: p914 Sep 8 2003, 08:12 PM

Wish they had 100 here in WA at the regular pumps

Posted by: seanery Sep 8 2003, 08:13 PM

I'm gonna hijack a little here:

Will there be a benefit to run premium 92 or race gas 100 in my car's configuration?
2.0 Euro Pistons/Cyls
webcam 494
weber 40's
SSI's
triad
compression bumped to 9-9.5 to 1

Thanks.

Posted by: p914 Sep 8 2003, 08:14 PM

So it should work fine according to the specs eh?

Posted by: SirAndy Sep 8 2003, 08:15 PM

now if i understand the whole thing right (which i might not) then using higher octane rated fuel WITHOUT any engine modifications that increase compression, is a complete waste of money.

the higher the octane number, the more you can compress the gas before it ignites itself (pre-detonation, VERY bad for your car).
but, if you have a stock 1.7 that was rated for 91 from the factory, filling it up with 98 is not going to do you any good. it might even hurt the engine.

going over 100 or using race-gas in a 7.3:1 engine SHOULD NOT make it run better.
anyone?

Andy

Posted by: redshift Sep 8 2003, 08:19 PM

Kevin, your 72 an early one? Spec is 93 octane.

Andy you freak.. Nope.




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Posted by: redshift Sep 8 2003, 08:22 PM

It *is* spec.



The 1.7 I burned to the ground was running 92 octane


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Posted by: p914 Sep 8 2003, 08:28 PM

ahhhhhsooooo redshiftsan.

so you are saying that regular should run fine? but you went ahead and burned premium


Yes...*spec*

Posted by: Bleyseng Sep 8 2003, 08:53 PM

here is the compression ratio chart for all the years


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Posted by: Drums66 Sep 8 2003, 11:05 PM

I agree with this!

Posted by: redshift Sep 9 2003, 06:09 AM

No, the 1.7 that burned was spec'ed for 98 RON.




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