cr limits on pump gas?

[BFB]

whats yalls THOUGHTS on highest compression ratio YOU can run on pump gas?
i know theres a bunch of other factors, and this isnt a specific build question, just wondering what opinions are.
_________________
Forced induction can overcome a lot of obsticles that gets in it's way
"You are the Engineer and the Mechanic.  
Build it your way not the way someone else does it. Their way might not work for you." - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
“ The monkey see monkey do mentality seems to run deep in VW people. "Gene Berg said it was so 30 years ago so thats the way it is" “ - bdkw1

[sled]

varies wildly with cam choice, volumetric efficiency, burn quality, ignition control, etc.

some guys have run REALLY high compression with super squish pistons and premium pump gas, like 12:1 and above.

JPM in Sweden has built some engines with super high compression as well, but usually doesn't mention what fuel he is using.
_________________
drive your split.

[mark tucker]

way tomany variables. Ive run 13.8 cr on pump gas for many years with my 340 mopar. my 2028 ve was 10.4 and was well over 80,000 miles when I sold it running great and probably good for another 80,000 if the new owner dosent let any body eff with it execpt for syn oil changes every 2 years. I ran my 1874 around 11.3 for about a year with no issues other than the bugspary carb wasent big enough.I lowered the cr to 10.5 for another 3 years.no issues other than sonnic noises in the intake witch went away when I put the duel 44'hpmx's on, cam shaft,jetting,timing,head&chamber shape and cooling along with piston to head clearance all come into play as well as exhaust. it's kinda funny how bingo down the road cant make 8:1 cr work but others can make 10.5 work just fine...and how are the oe engines now work ok at 11:1&higher with no issues..... doing it right is what it takes, reguardless of engine type,shape,color,size or make.

[bugguy1967]

The more rpm the setup is built for, the more cr it can handle. The limits are probably around 190 psi.
_________________
"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[oprn]

I have run 9 to 9.4 on 87 octane in the past, no issues. I am running 8.4 on 87 fuel presently with no pinging even at an accidental 16* initial timing. Some guys here claim low 7's is the limit on 87. Not sure where that comes from...

I think bugguy1967 is on to something there. It may be more directly related to your cylinder cranking pressure than anything else.
_________________
We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age)

[UK Luke 72]

10.2:1 on an 86b with 97 uk fuel running fine here. Will be 11:1 with an fk10 very shortly.

Not like that info is much use to you though anyway.
_________________
2276 Beetle build https://www.thesamba.com/vw/forum/viewtopic.php?t=670744&highlight=2276+beetle+daily
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[vwracerdave]

Don't let anybody fool you. 9.5:1 is the limit for 91 Octane pump gas here in the USA.
_________________
2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Featured in Dec. 2001 HOT VW's Magazine page 63

Watch my racing video's http://www.youtube.com/user/okvwracer/videos

[jpaull]

I have been doing fine 10.4 with crappy ca 91 pump gas on the street and track with Adv. Duration 321° /Dur. @ .050" 270° and 180 cranking psi. This might not work with other cams though
_________________
[email protected] MPH 1/4 Mile & 8.1 @ 83.7MPH in 1/8 Mile with Mild Type 1 VW Mag Case 2234cc commuter engine in stock weight bug w/only .491 total lift(CB2292 Cam), 42x37 heads, 48idf's, Street tires, Belt on, Mufflers, Pump gas, video of the run here: https://youtu.be/M3SPqMOKAOg

Transmission by MCMScott:
Rhino case, Klinkenberg 4.12, Superdiff, 002 mainshaft with 091 first idler. Weddle 1.48 Third & 1.14 Fourth.

[BFB]

this is great, it essentially the same as seeing what boost ppl run. there's soooo many variables and possibilities!
ok, so u guys that run 11:1 ish or above , what kinda afr and timing do you run? probably not as retarded as boosted i assume
_________________
Forced induction can overcome a lot of obsticles that gets in it's way
"You are the Engineer and the Mechanic.  
Build it your way not the way someone else does it. Their way might not work for you." - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
“ The monkey see monkey do mentality seems to run deep in VW people. "Gene Berg said it was so 30 years ago so thats the way it is" “ - bdkw1

[croSSeduP]

[oprn]

And we have a 7.1/1 guy!!! I knew they would come crawling out of the woodwork! Even VW didn't go that conservative on the BUS!

It ended up being the hottest running shortest valve life engine ever too... any guesses why?
_________________
We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age)

[King_vw61]

Under 10 to 1 with 91 in Cali would be safe if tuned right.

We are getting more and more E85 stations around here, that's 106 octane, So 10 to 1 would be safe if you dare to run it.

I will be switching over to it in the next 2 weeks. Mainly for cooling issues and the station next to me just started selling it. I am going to a 14.5 gallon tank to I can still get 100 miles per tank.

I will keep the jet stack for gas in my glovebox in case I need fuel and can't find E85 where i'm at.

I have Tuned 2 cars now and They both like the E85, Just changing the main fuel jet and the Idle jet. not the pump jet or Fuel pressure. So going back to gas would take 5 min.
_________________
1961 Ragtop, Autocraft 2783cc for street/strip 10k miles and counting...230.84 HP to the wheels thru Muffler 13.4 to 1 on E85
https://www.instagram.com/king_vw61/?hl=en

[mark tucker]

[Alstrup]

This was discussed in another thread not long ago. The same people came forward and bashed the "high compression" for being wrong, myself included. But, once again, you cannot determine max compression ratio from a default of say 9,5. The max static compression is solely determined by octane, ambient temp and cam bleed off (duration) We are talking purely sea level here.

With E 85 you can run rather high static compression without getting into trouble, since it cools significantly more, and has more octane. In general you can add 1 to the CR if you run E85 over 91 us pump gas.
Over here there are racers that run 13,5-1 static with regular FK89 cams and E85. I know, thats racing, but it gives you a good hint.
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https://www.thesamba.com/vw/forum/viewtopic.php?t=435993

[evanfrucht]

Some people in hot southern California will run 10.5 - 11 CR with very radical cams. They can fill it up at the gas station w/ 91 if they wanted. These are very serious and often high maintence engines tho.

It depends on enough factors that it's pretty much impossible to answer the question. What's the most compression that is possible to run on a type 1 vw engine if you had unlimited money and could aquire any of the parts or do any mods you wanted? Maybe 14-15+ static, who knows... I'm sure there are examples out there of some insane aircooled engineering feats such as this. Maybe in the Alps, lol!

Generally the average hot street engine you run into will be running 8.5 - 10 CR. That is very common to see. But probably mainly because the W110, W120, FK8/86B type cams are very popular and work well in that range respectively.
_________________
1967 Bug ( the daily rod )
1964 Fury Wagon ( the pavement shredder )

[Alstrup]

[bugguy1967]

For anyone who cares to learn: very long read, but worth it. https://www.hotrod.com/articles/0606em-understanding-compression-ratio/
_________________
"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[bugguy1967]

[Brian_e]

[vwracerdave]

It won't do any good to explain my opinion. People are gonna disagree no matter what. We might as well argue about which oil to use.

Build whatever you want. Listen to whomever you want. I guarantee you get to keep all the broken pieces.

You can't read a Chevy book and build a VW engine.
_________________
2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Featured in Dec. 2001 HOT VW's Magazine page 63

Watch my racing video's http://www.youtube.com/user/okvwracer/videos