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Ohio Tom
Samba Member
Joined: February 09, 2006
Posts: 1660
Location: Marshallville Ohio
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 Posted: Tue Apr 20, 2021 10:19 am Post subject: Re: cr limits on pump gas? |
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| Sheesh... Sure am glad I stayed out of this one.. |
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bugguy1967
Samba Member
Joined: January 16, 2008
Posts: 4343
Location: Los Angeles, CA 90016
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| Posted: Tue Apr 20, 2021 10:23 am Post subject: Re: cr limits on pump gas? |
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My wife drives a Hyundai with an "Atkinson" engine, but it's not really an Atkinson, as a true Atkinson completes all its' events in one crankshaft revolution. Her engine actually just has a very late intake closing period, which is revived old technology. Hot Rod Magazine used to carry an ad from Comp Cams in the 70's where they had a 'Fuel Saver" cam kit. The cam delayed the intake closing period so late that VE was down by about 30%. You regained some drivability by boosting your static compression up to the high 10s/low 11s. The design was sound, but trying to run such an engine at cruising speeds with a carburetor was a nightmare. The signals to the carb were so erratic that it was hard to get a good tune. These closing periods work best by injecting near the valve.
The same principles apply to the larger 8,000+rpm camshafts we use. Erratic idles with carburetors, but they sing at upper rpm . It's not too hard to understand really, you lose some gases back up the intake tract before closing, so you compensate with static compression to boost low end torque. You can leave the static alone, if you wish, but your bottom end power will suffer.
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"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" |
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ac509
Samba Member
Joined: September 20, 2012
Posts: 160
Location: moved
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| Posted: Tue Apr 20, 2021 11:07 am Post subject: Re: cr limits on pump gas? |
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| [email protected] wrote: |
| ac509 wrote: |
e85 is widely available and comes from a pump...
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Yes but we’re talking about pump gas, not pump fuel. 85% C16 mixed with pump gas could run a little higher compression as well. |
yeah, but doesn't e85 have "gas" in it?
_________________
Dumber people are doing harder things everyday.
No one questions a 73' Volkswagen?
I have a '73 Volkswagen and it is nowhere near 73' long! |
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King_vw61
Samba Member
Joined: February 03, 2018
Posts: 1383
Location: Southern California
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| Posted: Tue Apr 20, 2021 12:40 pm Post subject: Re: cr limits on pump gas? |
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20%. +- suppose to be 85% ethanol and 15% gas.
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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 |
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BFB
Samba Member
Joined: November 03, 2014
Posts: 1762
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| Posted: Tue Apr 20, 2021 6:40 pm Post subject: Re: cr limits on pump gas? |
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just for you ppl that are confused and think i started this post for your help in building an engine, i primarily enjoy boosted vw's and the ones ive built run an effective cr of around 15 to 16ish:1 on pump gas. so like i said, i dont need your advice. i just thought this would be a fun topic to talk about because i was on page 1,320 something of this forum and kept seeing posts from early 2000's ( some from you guys that have posted in this thread ) about compression ratio's and thought itd be cool to see some of the same guy's opinions 20 years later. and just see how much things may have changed, with more ppl using FI and programmable ignition youd think cr's would come up and they seem to have. i didnt see many old posts where ppl were pushing more than 10:1. pretty interesting to me.
_________________
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 |
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[email protected]
Samba Member
Joined: May 17, 2003
Posts: 4863
Location: Harmony, PA
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| Posted: Tue Apr 20, 2021 7:28 pm Post subject: Re: cr limits on pump gas? |
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| richardcraineum wrote: |
| just for you ppl that are confused and think i started this post for your help in building an engine, i primarily enjoy boosted vw's and the ones ive built run an effective cr of around 15 to 16ish:1 on pump gas. so like i said, i dont need your advice. i just thought this would be a fun topic to talk about because i was on page 1,320 something of this forum and kept seeing posts from early 2000's ( some from you guys that have posted in this thread ) about compression ratio's and thought itd be cool to see some of the same guy's opinions 20 years later. and just see how much things may have changed, with more ppl using FI and programmable ignition youd think cr's would come up and they seem to have. i didnt see many old posts where ppl were pushing more than 10:1. pretty interesting to me. |
Be it good, or bad, a lot has changed in the exchange of information in 20 years. Before the Samba, or active use of the internet, info was first hand, or from magazines. One of the greatest things I’ve learned in racing, or info from the internet is, most likely someone is doing something better than you with more knowledge/experience. It’s your choice to say it’s bullshit, or have an open mind to find out what they know that you don’t. I’ve been fortunate enough to put enough pieces together to eventually figure out everything I’ve wanted to know so far. The Samba/internet has simply helped supply the puzzle pieces at a quicker rate. Unfortunately, it’s also added a lot of useless pieces that don’t fit anywhere. |
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vwracerdave
Samba Member
Joined: November 11, 2004
Posts: 15309
Location: Deep in the 405
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| Posted: Tue Apr 20, 2021 8:28 pm Post subject: Re: cr limits on pump gas? |
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| richardcraineum wrote: |
| i just thought this would be a fun topic to talk about because i was on page 1,320 something of this forum and kept seeing posts from early 2000's ( some from you guys that have posted in this thread ) about compression ratio's and thought itd be cool to see some of the same guy's opinions 20 years later. and just see how much things may have changed, with more ppl using FI and programmable ignition |
As far as CR goes, nothing has changed. Not one single thing has changed in the last 20 years and the young people refuse to understand or accept it. Nothing has changed in the last 20, or 30, or 40 years. No matter what you think new technology brings, nothing has changed. As gkeeton above pointed out the only difference is the lightening speed of how fast information is passed around the globe, but the information has not changed.
Young people today will never understand the Bow and Arrow theory. Carbs and distributors is the only reason I still drive a VW. The only reason I still race a VW is because I love shifting gears.
_________________
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 |
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croSSeduP
Samba Member
Joined: June 13, 2004
Posts: 1106
Location: Western Washington State
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| Posted: Tue Apr 20, 2021 9:37 pm Post subject: Re: cr limits on pump gas? |
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| oprn wrote: |
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? |
Wow. You're kind of coming across like a jerk, and I'm sure you aren't. "Crawling out of the woodwork..." Hmm. What creatures could this be referring to here? See what I mean? Here's what I said:
"If it's a bone stock motor that you want to run 100,000 miles, and use the cheapest 87 octane fuel, I'd run 7:1 CR."
In that kind of motor, what CR would you recommend? I can tell you that I once had a 1756cc (90x69) that was otherwise totally stock, and it pinged like a mother. It had about 8.5:1 CR. Ran hot, too. After that motor went belly up I slapped together a stock motor (it did have dual Solex carbs, however) with 7:1 CR, and it ran great, got great mileage, didn't run hot, etc. I could say more from my experience, but I'd honestly like to hear your opinion on the kind of CR a bone-stock 1585 should run, using the cheapest 87 octane gas available. Thank you.
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Please check my '67 sedan project progress!
http://www.thesamba.com/vw/forum/viewtopic.php?t=502253&highlight= |
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buguy
Samba Member
Joined: November 17, 2003
Posts: 4915
Location: Port Orange, FL
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| Posted: Wed Apr 21, 2021 4:22 am Post subject: Re: cr limits on pump gas? |
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| I ran 8:1 on my basically stock 1600 at 30 psi of boost. Same 8:1 with it and a Web 163. I now have a 2054 with 9:1 and that same Web 163, but have only boosted around 12 psi. I broke an axle soon after putting the 2054 in so i haven't been able to turn the boost up yet to see how it likes it. Both run on E85 primarily. I do have a flex fuel controller but usually just run on the 12 psi waste gate with 91 octane. |
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[email protected]
Samba Member
Joined: May 17, 2003
Posts: 4863
Location: Harmony, PA
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| Posted: Wed Apr 21, 2021 5:24 am Post subject: Re: cr limits on pump gas? |
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I think in terms of pushing cr limits in n/a engines.
You boosted guys, what are you running for timing when you’re running 15, and 30psi? It’s not the common 30-32 degrees that a n/a engine is running.
If you want to play devils advocate, Top Fuel engines with 7.0:1 compression, and 60psi of boost run on pump gas....
I’m beginning to see why Ohio Tom was glad he didn’t participate.... |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12740
Location: Western Canada
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| Posted: Wed Apr 21, 2021 5:50 am Post subject: Re: cr limits on pump gas? |
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| croSSeduP wrote: |
| oprn wrote: |
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? |
Wow. You're kind of coming across like a jerk, and I'm sure you aren't. "Crawling out of the woodwork..." Hmm. What creatures could this be referring to here? See what I mean? Here's what I said:
"If it's a bone stock motor that you want to run 100,000 miles, and use the cheapest 87 octane fuel, I'd run 7:1 CR."
In that kind of motor, what CR would you recommend? I can tell you that I once had a 1756cc (90x69) that was otherwise totally stock, and it pinged like a mother. It had about 8.5:1 CR. Ran hot, too. After that motor went belly up I slapped together a stock motor (it did have dual Solex carbs, however) with 7:1 CR, and it ran great, got great mileage, didn't run hot, etc. I could say more from my experience, but I'd honestly like to hear your opinion on the kind of CR a bone-stock 1585 should run, using the cheapest 87 octane gas available. Thank you. |
My apologies! It was written in a moment of disgust and I shouldn't have worded it that way. It seems there are subjects that bring out extremes in opinion and this is one of them.
VW abandoned the 7/1 CR mentality way back in the early days of the 40 HP engine. All 40 HP engines from '61 and on were higher. Why you would build one this way today is totally beyond me. Yes it would run ok but so does my old '46 McCormick tractor at 5/1 CR but is has very little power for it's displacement and is a fuel hog!
Back in the mid '70s I build an engine for my '71 SB all stock 1600 but with a 9/1 CR and it ran fine with a recurved distributor on 87 octane. Then I built an engine for my Rabbit at 9.4/1 and added a turbo with a reworked timing curve. I used 87 octane on it too and it ran into pinging above 8 psi boost in the summer and would go well over 15 psi in the winter with no issues on the same fuel.
My present air cooled engine is a type 4 that I asked for C/R advice for on this forum thinking that I was in unfamiliar territory with never having to run a type 4 and all the noise about modern fuels being so bad. The advice for the most part here was to stay with the stock 7.4/1 especially since 87 octane is the only fuel available locally. I didn't and ended up at 8.4/1. Yes is runs good but I cannot find a ping anywhere unless I go 16* BTDC on initial timing, lug it down to 600 rpm and stand on it hard!
Now I am struggling to get the fuel mileage up where it should be on a car this light. I deeply regret not going 9/1 again!
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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)
Last edited by oprn on Wed Apr 21, 2021 6:02 am; edited 1 time in total |
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ac509
Samba Member
Joined: September 20, 2012
Posts: 160
Location: moved
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| Posted: Wed Apr 21, 2021 5:55 am Post subject: Re: cr limits on pump gas? |
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| vwracerdave wrote: |
As far as CR goes, nothing has changed. Not one single thing has changed in the last 20 years and the young people refuse to understand or accept it. Nothing has changed in the last 20, or 30, or 40 years. No matter what you think new technology brings, nothing has changed. |
i stopped visiting the samba for a while because i got bored with it. i got bored with the other sites and came back to the samba recently. your posts are why i always come back. this is goood stuff. thank you.
back on topic, 11.2:1 is what i am running with e85 and a small FK cam. i have no idea what my timing is. timing is just a number. my engine knows what it likes and that's what i give it.
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Dumber people are doing harder things everyday.
No one questions a 73' Volkswagen?
I have a '73 Volkswagen and it is nowhere near 73' long! |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12740
Location: Western Canada
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| Posted: Wed Apr 21, 2021 6:19 am Post subject: Re: cr limits on pump gas? |
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| vwracerdave wrote: |
| As far as CR goes, nothing has changed. Not one single thing has changed in the last 20 years and the young people refuse to understand or accept it. Nothing has changed in the last 20, or 30, or 40 years. No matter what you think new technology brings, nothing has changed. |
Oh wow!
My Brother bought a Ford Fiesta 14/1 C/R, ran one 87 octane, made lots of power and he claimed would do a bit over 50 mpg. My daughter and husband bought a new VW TSI. Again over 14/1 C/R, 1400 cc engine twin turbo, lots of power and high 40s mpg. Mazda has a similar engine for what? 8 years now? What about variable valve timing? Were ethanol blended fuels common 20, 30, 40 years ago? There are camshaft options available today that we could have only dreamed of then. Check out what some of the guys here are doing with crank trigger and FI!
Time to open up your mind and acknowledge that things are indeed changing... big time!
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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) |
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bugguy1967
Samba Member
Joined: January 16, 2008
Posts: 4343
Location: Los Angeles, CA 90016
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| Posted: Wed Apr 21, 2021 11:23 am Post subject: Re: cr limits on pump gas? |
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| vwracerdave wrote: |
| richardcraineum wrote: |
| i just thought this would be a fun topic to talk about because i was on page 1,320 something of this forum and kept seeing posts from early 2000's ( some from you guys that have posted in this thread ) about compression ratio's and thought itd be cool to see some of the same guy's opinions 20 years later. and just see how much things may have changed, with more ppl using FI and programmable ignition |
As far as CR goes, nothing has changed. Not one single thing has changed in the last 20 years and the young people refuse to understand or accept it. Nothing has changed in the last 20, or 30, or 40 years. No matter what you think new technology brings, nothing has changed. As gkeeton above pointed out the only difference is the lightening speed of how fast information is passed around the globe, but the information has not changed.
Young people today will never understand the Bow and Arrow theory. Carbs and distributors is the only reason I still drive a VW. The only reason I still race a VW is because I love shifting gears. |
Yes and no. Air's principles have not changed. Larry Widmer figured how to run 14:1 compression, get excellent fuel mileage, make more power, and run cooler in a VR6 in the 70s. Over the years, modern automotive industries and hobbyists have figured out how to extract more power from their mixtures while we only make very small gains.
What has changed is control over ignition - the ability to move away from gear-driven allows us to set up the spark table howevercwe choose, better camshaft profiles, if we're willing to pay for them (Jurgen Novak, JPM), our ports are shrinking, and chamber shapes are being revised. All of these play an essential role in increasing our expansion ratios.
You hinder growth and creativity with your statements, and if you would be succesfful in your attempt, you could leave the hobby and come back in 20 years and everything would be exactly the same. Who would want that?? I encourage everyone here to keep pushing. Try and see.
Advantages of running more compression (when making an equal comparison to a low compression engine):
Reduced pumping losses during exhaust stroke
Faster, more complete burn
Less ignition advance required
Increased thermal efficiency
Higher torque throughout powerband
Better fuel economy
Higher expansion ratio - allows more energy to be extracted from the charge
Smaller exhaust valves can be used
You progress the sport
_________________
"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" |
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buguy
Samba Member
Joined: November 17, 2003
Posts: 4915
Location: Port Orange, FL
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| Posted: Wed Apr 21, 2021 11:34 am Post subject: Re: cr limits on pump gas? |
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| [email protected] wrote: |
I think in terms of pushing cr limits in n/a engines.
You boosted guys, what are you running for timing when you’re running 15, and 30psi? It’s not the common 30-32 degrees that a n/a engine is running.
If you want to play devils advocate, Top Fuel engines with 7.0:1 compression, and 60psi of boost run on pump gas....
I’m beginning to see why Ohio Tom was glad he didn’t participate.... |
I run from about 40 degrees down to 25 degrees at full boost at 30 psi. Again this is on E85. Never heard any hint of detonation, but was too scared to chance running any more than that. |
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Alstrup
Samba Member
Joined: July 12, 2007
Posts: 7219
Location: Videbaek Denmark
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| Posted: Wed Apr 21, 2021 11:38 am Post subject: Re: cr limits on pump gas? |
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| bugguy1967 wrote: |
Advantages of running more compression (when making an equal comparison to a low compression engine):
Reduced pumping losses during exhaust stroke
Faster, more complete burn
Less ignition advance required
Increased thermal efficiency
Higher torque throughout powerband
Better fuel economy
Higher expansion ratio - allows more energy to be extracted from the charge
Smaller exhaust valves can be used
You progress the sport |
Add to that:
less emissions
No loss in engine life if done right.
Almosty always better ring life.
| buguy wrote: |
I run from about 40 degrees down to 25 degrees at full boost at 30 psi. Again this is on E85. Never heard any hint of detonation, but was too scared to chance running any more than that. |
At some point there is no idea in advancing the timing. That is when the burn is 80% done at 20 degrees ATDC which incidently is also where you get max power, - and best fuel efficiency on a lean burn.
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https://www.thesamba.com/vw/forum/viewtopic.php?t=435993 |
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vwracerdave
Samba Member
Joined: November 11, 2004
Posts: 15309
Location: Deep in the 405
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| Posted: Wed Apr 21, 2021 12:32 pm Post subject: Re: cr limits on pump gas? |
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I understand the advantages of increasing CR. I also understand you CAN NOT change the science or chemistry of gasoline. You can not change the amount of oxygen in the air. You can not change the burn rate of the air/fuel mixture. When you increase CR you also need to increase octane.
By advancing or retarding the timing, all you are doing is changing when the light switch comes on.
Nothing has changed the last 20 years.
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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 |
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[email protected]
Samba Member
Joined: May 17, 2003
Posts: 4863
Location: Harmony, PA
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| Posted: Wed Apr 21, 2021 1:12 pm Post subject: Re: cr limits on pump gas? |
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| vwracerdave wrote: |
I understand the advantages of increasing CR. I also understand you CAN NOT change the science or chemistry of gasoline. You can not change the amount of oxygen in the air. You can not change the burn rate of the air/fuel mixture. When you increase CR you also need to increase octane.
By advancing or retarding the timing, all you are doing is changing when the light switch comes on.
Nothing has changed the last 20 years. |
EXACTLY......
There are modern engines with variable valve timing, variable ignition timing, and even variable compression ratios with the crankshaft center on a counter shaft that raises/lowers the pistons as load is increased/decreased. If there are no set perimeters of conditions when cr is too high this whole thread is useless. I only asked what the timing was under boost figuring it would be 22-26 degrees. A n/a race motor with 13.0:1 normally ran on race gas at 30+ degrees will run on pump gas at 22-26 degrees timing. And although E85 is available at a lot of pumps, it’s not gas, it’s 85% ethanol. Last time I spoke with someone running it in a street car, they mentioned it was about the equivalent to 104 octane gas, so its irrelevant in this thread unless the op changes the opening request to pump FUEL. |
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Brian_e
Samba Member
Joined: July 28, 2009
Posts: 3293
Location: Rapid City, SD
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| Posted: Wed Apr 21, 2021 1:16 pm Post subject: Re: cr limits on pump gas? |
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Dave,
You don't think new modern chamber designs allow for more compression, and more power because of detonation resistance, increased burn quality, or more complete burn?
Same with new modern cam designs, or better cooling heads that weren't available 10 years ago?
How is it guys like JPM can safely run 12:1 on the street with pump gas and make gobs of power that were hardly attainable 15 years ago with all the fanciest available parts?
Brian
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gprudenciop
Samba Member
Joined: July 06, 2008
Posts: 606
Location: portland or
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| Posted: Wed Apr 21, 2021 1:32 pm Post subject: Re: cr limits on pump gas? |
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| buguy wrote: |
| [email protected] wrote: |
I think in terms of pushing cr limits in n/a engines.
You boosted guys, what are you running for timing when you’re running 15, and 30psi? It’s not the common 30-32 degrees that a n/a engine is running.
If you want to play devils advocate, Top Fuel engines with 7.0:1 compression, and 60psi of boost run on pump gas....
I’m beginning to see why Ohio Tom was glad he didn’t participate.... |
I run from about 40 degrees down to 25 degrees at full boost at 30 psi. Again this is on E85. Never heard any hint of detonation, but was too scared to chance running any more than that. |
14 degrees at 26 psi 8.2 to 1 compression on 93. 2276
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