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bugguy1967
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Joined: January 16, 2008
Posts: 4343
Location: Los Angeles, CA 90016
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 Posted: Wed Apr 21, 2021 1:39 pm Post subject: Re: cr limits on pump gas? |
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Oh! Let's not forget about cooling! Any strives we can make in lowering cylinder temps will allow more compression. Also, adding another plug in some cases can allow more compression too.
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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 1:54 pm Post subject: Re: cr limits on pump gas? |
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| Alstrup wrote: |
| 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. |
So what is the best course of action if there is no detonation? Put it on a dyno and tune for Max hp/tq? |
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mark tucker
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Joined: April 08, 2009
Posts: 23937
Location: SHALIMAR ,FLORIDA
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| Posted: Wed Apr 21, 2021 2:35 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. |
sorry dave but you are dead rong. perhaps you need to come out of the dark ages and step away from the how to hot rod vw's book. |
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Alstrup
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Joined: July 12, 2007
Posts: 7221
Location: Videbaek Denmark
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| Posted: Wed Apr 21, 2021 2:43 pm Post subject: Re: cr limits on pump gas? |
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Buguy
Something like that. but that way you can most likely only tune for best power. It depends heavily on the dyno and the operator.
If you are not affraid of investing in some hardware I have found the PLEX knock monitor to be very usefull, especially when you have access to the AFR levels and ignition map.
Another simpler, but more time consumonig way to find the sweet spot is to monitor cylinder head temperatures along with EGT and the tune for lean best cruise.
I am not too familiar with E85 so I can´t give any solid hints as to proper timing for that. Only can I say that - usually - the timing for lean best cruise is not so much different on E85 versus regular E10. On boost however it is a different game. Often 4-5 degrees more dependant on boost of course.
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buguy
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Joined: November 17, 2003
Posts: 4915
Location: Port Orange, FL
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| Posted: Wed Apr 21, 2021 5:01 pm Post subject: Re: cr limits on pump gas? |
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| Thank you for the insight. I have only tuned on the street so far and i have just tried to make it where it feels and sounds happy. |
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modok
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Joined: October 30, 2009
Posts: 26790
Location: Colorado Springs
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| Posted: Wed Apr 21, 2021 6:09 pm Post subject: Re: cr limits on pump gas? |
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I can see where Racerdave is coming from
You could build a more radical combo that CAN run pump gas..... but why would you?
Does it make sense? Besides just doing it for it's own sake. |
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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 9:19 pm Post subject: Re: cr limits on pump gas? |
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| modok wrote: |
I can see where Racerdave is coming from
You could build a more radical combo that CAN run pump gas..... but why would you?
Does it make sense? Besides just doing it for it's own sake. |
Why does anyone do anything? We only NEED as much power as it takes to pull a grade and keep up with traffic. Let's all put 1600s back in.
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modok
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Joined: October 30, 2009
Posts: 26790
Location: Colorado Springs
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| Posted: Wed Apr 21, 2021 10:45 pm Post subject: Re: cr limits on pump gas? |
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Dual plug, 11-1 compression 1600?
Whatever floats your boat.  |
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evanfrucht
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Joined: July 24, 2016
Posts: 2180
Location: Laurel Canyon, CA
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| Posted: Thu Apr 22, 2021 12:05 am Post subject: Re: cr limits on pump gas? |
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| modok wrote: |
Dual plug, 11-1 compression 1600?
Whatever floats your boat. |
I'll raise that to a destroked 1500
...at 11.2
And don't forget to try to force feed it 
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1967 Bug ( the daily rod )
1964 Fury Wagon ( the pavement shredder ) |
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oprn
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Joined: November 13, 2016
Posts: 12744
Location: Western Canada
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| Posted: Thu Apr 22, 2021 3:59 am Post subject: Re: cr limits on pump gas? |
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I'm pretty sure that someone somewhere will be, if they haven't already, modifying a set of heads to go direct injection just like the major car companies are. Then yes that will all happen.
Why would they? For the same reason all you guys push the limits of 50 year old air cooled technology to try and reach 200 HP when you can go out and buy what you are trying to achieve right off the showroom floor... with a warrantee!
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Alstrup
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Joined: July 12, 2007
Posts: 7221
Location: Videbaek Denmark
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| Posted: Thu Apr 22, 2021 5:27 am Post subject: Re: cr limits on pump gas? |
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| evanfrucht wrote: |
| modok wrote: |
Dual plug, 11-1 compression 1600?
Whatever floats your boat. |
I'll raise that to a destroked 1500
...at 11.2
And don't forget to try to force feed it |
Hehe 
But if we take a step back and look at more conventional "easy to build" SI engines, a simple change in combustion chamber shape/design (NOT SH) can improve flame travel a good deal, like 5% or so, which will allow the use of higher static CR and give especially more torque without increasing head temperature. I have noted that some head manufacturers- and head porters have seen the light.
I/we messed with it 15 years ago, but did´nt have the tools, funds and knowledge to finish what we started back then.
Dual plugs are intreaging and can really boost midrange power and add some 6-10 hp on top, the larger the bore the higher the potential bvenefit) but it is not as simple as it sounds. And even with todays access to fairly decent stand alone ignitions it is still a little costly. And if you want full potential of it you HAVE to have a programmable ignition or you will loose 50% of the potential improvement below approx 2500 rpm.
To my knowledge there are 2 maybe 3 companies that have attempted to make a direct injection ACVW engine, but none of them came further than the experimental stage due to un expected problems. I am not sure what was the issues though
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Wreck
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Joined: July 19, 2014
Posts: 1218
Location: Brisbane
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| Posted: Thu Apr 22, 2021 5:52 am Post subject: Re: cr limits on pump gas? |
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why don't more people use water/meth injection to raise compression on NA street engines running pump gas ?
I have first hand evidence of both fixing detonation on a lean idle to main transition on a 10.5 comp engine and also lowering CHT on a mild 2300 bus engine under full load for a long sustained time.
Thats the nozzle in the manifold , just a squirt of 50/50 water ,denatured alcohol , I use a cheap RV 12v high pressure water pump trigger by the megavolt ignition on one car and just a simple switch on the other when the engine is under sustained load .
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oprn
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Posts: 12744
Location: Western Canada
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| Posted: Thu Apr 22, 2021 6:09 am Post subject: Re: cr limits on pump gas? |
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Dad used to talk about water injection on the 1940s tractors. They just used water from the cooling system (most farmers back then didn't use antifreeze - too expensive) and they just added it during the day to maintain the same power that the tractor had at night due to the cooler air. No methanol, just water. It seems the evaporation of the water in the intake and combustion chamber had enough cooling effect.
The gain in power I am sure was not large but enough to be noticeable. I'm sure it would help with pinging too. That is definitely an under utilized idea on N/A engines.
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vwinnovator
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Joined: July 11, 2005
Posts: 1555
Location: Still doing it in the back of your VW
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| Posted: Thu Apr 22, 2021 7:11 am Post subject: Re: cr limits on pump gas? |
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| [email protected] wrote: |
| 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. |
Let do it! we can add in diesel CR's
80's rabbits had 23:1 on 1.6(1600cc)
let's make a 23:1 air-cooled diesel type1 |
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Alstrup
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Joined: July 12, 2007
Posts: 7221
Location: Videbaek Denmark
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| Posted: Thu Apr 22, 2021 8:54 am Post subject: Re: cr limits on pump gas? |
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| vwinnovator wrote: |
Let do it! we can add in diesel CR's
80's rabbits had 23:1 on 1.6(1600cc)
let's make a 23:1 air-cooled diesel type1 |
Has been done, - for experiment only though. 2 engineers from Deutz built a 1776 diesel, maybe 25 years ago.
Wreck, the water meth injection is very efficient, also on N/A engines. We have used it here and there, but only twice on an ACVW. One of them was a turbo. However, a customer of mine is planning on using it on his 2,5l type4. That decission was made something like three years ago, and from the fact that high octane fuel was getting scarce around here due to Shell selling their franchise service stations to CircleK who decided that they would rather sell the overhyped Statoil miles fuel rather than proper 99 octane. In the meantime another company has - luckily seen the light and is now selling 100 octane, so it is now available almost everywhere. Due to this I don´t know if he will proceed or just go buy 100 octane.
I think that at least one of the reasons to why it is not used much is the complexity of a boxer and space restraints in a VW engine compartement. In most water cooled engine bays there is significantly more room to work with.
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Ohio Tom
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Joined: February 09, 2006
Posts: 1660
Location: Marshallville Ohio
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| Posted: Thu Apr 22, 2021 1:17 pm Post subject: Re: cr limits on pump gas? |
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In Brazil, they make an aircooled VW based Diesel for farm and utility use.
Otherwise, I'm staying out of this discussion. |
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Wreck
Samba Member
Joined: July 19, 2014
Posts: 1218
Location: Brisbane
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| Posted: Thu Apr 22, 2021 2:30 pm Post subject: Re: cr limits on pump gas? |
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| vwinnovator wrote: |
| [email protected] wrote: |
| 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. |
Let do it! we can add in diesel CR's
80's rabbits had 23:1 on 1.6(1600cc)
let's make a 23:1 air-cooled diesel type1 |
Deutz diesel cylinders have been a very common big bore solution for type 4's for a very long time , these are 103mm with 6mm wall thickness .
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oprn
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Joined: November 13, 2016
Posts: 12744
Location: Western Canada
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| Posted: Thu Apr 22, 2021 4:49 pm Post subject: Re: cr limits on pump gas? |
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I have seen several VW history books that have pictures and text about VW's foray into diesel in the early days of the Beetle. There were even cross section drawings of them that showed the injector lay out. The whole project was abandoned due to low power and extreme noise.
My brother had 2 Deutz tractors and they were bloody loud! Water jackets dampen noise big time.
There are a couple of diesel air cooled engines for aircraft use out in the experimental stages. I cannot imagine sitting behind one for any length of time.
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Wreck
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Joined: July 19, 2014
Posts: 1218
Location: Brisbane
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| Posted: Thu Apr 22, 2021 5:51 pm Post subject: Re: cr limits on pump gas? |
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| oprn wrote: |
I have seen several VW history books that have pictures and text about VW's foray into diesel in the early days of the Beetle. There were even cross section drawings of them that showed the injector lay out. The whole project was abandoned due to low power and extreme noise.
My brother had 2 Deutz tractors and they were bloody loud! Water jackets dampen noise big time.
There are a couple of diesel air cooled engines for aircraft use out in the experimental stages. I cannot imagine sitting behind one for any length of time. |
I worked for a few years as a mechanic for a gas pipeline pressure testing crew , we had a few Duetz’s hooked up to water pumps , the high pressure pump was a V10 powering 2 mega sized pumps like a water pressure washer , just with 1” hoses . 12 hour shift you need ear protection all the time . It was a great job . Can’t remember now but I think test pressures were up near 5000psi . The V10 was working hard ! |
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