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RailBoy
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Joined: March 10, 2008
Posts: 2904
Location: Virginia
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 Posted: Thu Oct 30, 2014 1:13 pm Post subject: 5-7 HP, what it is...... |
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Compression Ratio......
Why do I say this, 5-7 HP is all the difference on a Street Motor that has been seen on average at Sea Level....
Is is worth a shorter engine life and higher temps?
Be the judge of your own engine, $6,500 at the pump @ 1,000,000 miles on a street engine worth the Compression to Say to your Friends it is a 9.1 CR?
Be the judge of what you want for street, now, if you are into drag nights, that is a different explination, like Ratio Rockers and Loft....
But is 5-7HP worth the hassle on a Daily Driver over Conversation to run 7.5 vs. 9.1 or even 9.3 CR? Price at the pump is what it is, and will be mandatory.. RB
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[quote="smitty24"]"HELP, I ported my own heads and now have fire coming out my ass" .[/quote]
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
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| Posted: Thu Oct 30, 2014 2:30 pm Post subject: Re: 5-7 HP, what it is...... |
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| RailBoy wrote: |
Compression Ratio......
Why do I say this, 5-7 HP is all the difference on a Street Motor that has been seen on average at Sea Level....
Is is worth a shorter engine life and higher temps?
Be the judge of your own engine, $6,500 at the pump @ 1,000,000 miles on a street engine worth the Compression to Say to your Friends it is a 9.1 CR?
Be the judge of what you want for street, now, if you are into drag nights, that is a different explination, like Ratio Rockers and Loft....
But is 5-7HP worth the hassle on a Daily Driver over Conversation to run 7.5 vs. 9.1 or even 9.3 CR? Price at the pump is what it is, and will be mandatory.. RB |
That really depends on what engine and how its fed.
For instance with the type 4 1.7l......the Calipornia D-jet injected version with 7.8:1 compression....all else is identical....pumps out about 72hp. The identical 49 states D-jet injected engine with 8.2:1 compression pumps out 82 hp, better torque and better gas mileage by about 2 mpg.
This is because at 7.8:1 the efficiency is down and the MAP controlled fuel system is less fine tunable. The engine duration of just about a standard 100-120k miles nominal with good care....is unchanged.
In the same cars (the 411 and 412)....the Euro and South Africa only twin carbed version...not to be confused with the bus version which is virtually the same except for camshaft...put out 68 hp due to fuel system changes alone with the same 7.8:1 compression ratio as the Calipornia D-jet injected smog model. Fuel mileage with twin carbs was also down.
Engine lifespan was unaffected by any of these changes.
Typical city fuel mileage in well tuned version of this engine
California D-jet: 21-22 mpg
49 states D-jet: 23-24 mpg
Twin Carbs: 20-21 mpg
All of these were manual trans numbers. With Automatic....they were all virtually the same at around 21-22 mpg.
So you see.....gearing and engine load also effect economy and wear pattern.
Also...from my experiences over about 300k miles on the same engine (D-jet injected 1.7l) with only tuning improvements, bigger valves, slightly better than stock cam (web # 73 which is stock timing and lobe center with slightly better lift and duration) and 8.5:1 compression.....I average about 25 mpg in city, better cooling due to the ability to run lower timing advance, cleaner engine due to more complete combustion....an improvement in highway mileage (documented over two identical engine builds) of about 5 mpg.
The stock D-jet injected engine with 8.2:1 compression and 82 hp.....which is a 10 hp increase over the 7.8:1 compression version...got 27-28 mpg on highway. With 8.5:1 compression and related tuning....it got 32-33 mpg.
I refurbed both engines around 150K miles. There is no greater issue with wear or life span.
You need to do the tuning required with compression changes.
Along with this...the rise in compression got rid of an inefficient deck height. Even with the factory domed pistons the effective deck height at the edge of the piston is .079".
When raising the compression that deck moved to .040". This dropped cylinder temps and allowed lowering max advance while raining at idle initial timing from about 8-9 BTDC to around 12 BTDC.
Also bear in mind....that virtually any modern vehicle you find on the road runs compression between 9.0 and 11.0:1. Yes...they accomplish living with regular pump gas with knock sensors....but they did the same in the late 80s and early 90s without knock sensors on most Watercooled VW.
Its in the tuning, gearing and combination. Ray |
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GTV
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Joined: March 27, 2004
Posts: 2084
Location: Si'ahl
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| Posted: Thu Oct 30, 2014 2:55 pm Post subject: |
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This is the performance forum, not the longevity/mileage forum.
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Howard 111
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Joined: July 09, 2005
Posts: 1827
Location: Virginia
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| Posted: Thu Oct 30, 2014 3:03 pm Post subject: |
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midtravelmidengine
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Joined: August 06, 2009
Posts: 861
Location: Riverside, Ca
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| Posted: Thu Oct 30, 2014 3:22 pm Post subject: Re: 5-7 HP, what it is...... |
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| RailBoy wrote: |
| Is is worth a shorter engine life and higher temps? |
How can you determine this?
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| modok wrote: |
| And I know you don't know because if you did you would know the reason for my knowing you didn't. |
| youngnstudly wrote: |
I just wasn't sure if I should recommend the 1/3 race cam, the 1/2 race cam, or the 5/8 race cam instead...guess it depends on how much of the race he wants to lead???
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RailBoy
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Joined: March 10, 2008
Posts: 2904
Location: Virginia
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| Posted: Thu Oct 30, 2014 3:54 pm Post subject: |
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Just basic combustion temps..... But yea, from all the R & D question regarding CR and Dyno's , you get just that out of the CR differences... RB
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[quote="smitty24"]"HELP, I ported my own heads and now have fire coming out my ass" .[/quote]
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raygreenwood
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Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
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| Posted: Thu Oct 30, 2014 4:53 pm Post subject: |
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| GTV wrote: |
This is the performance forum, not the longevity/mileage forum.
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Yeah...whatever. 
If it were a performance related question that could not be answered with what I just posted.....then 5-7hp was not a worthwhile question in the first place.....unless he was actually speaking of moving from 200 to 205 or 207hp.
The last set of mods with tuning, cam, valves, exhaust and moving to 8.5:1 compression took me from 82 to right at 90 rwhp...which was just over 100 on the dyno.
Thats a pretty high percentage of increase in performance even though the engine is "stockish".
Ray |
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Alstrup
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Joined: July 12, 2007
Posts: 7214
Location: Videbaek Denmark
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| Posted: Thu Oct 30, 2014 5:17 pm Post subject: |
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What Ray said.
- 5-7 hp,... on what size engine? with what cam and carbs etc. On say a main stream 1600 youre not that far off. On the other hand, the torque increases rapidly along with raised CR.
Say the same 1600 with the ever so popular W110 cam decent heads carbs etc and 7,5 CR will have a hard time pulling 90 hp and 130 Nm torque.
Same 1600, same heads, timed cam and 9,3-1 CR will be very close to 100 hp (I´ve pulled 104 a few times with that cam) and about 150 Nm torque with a MUCH better pick up and overall power.
On a 2275 set up for some power there can easily be 20 even 25 hp difference.
T |
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miniman82
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Joined: March 22, 2005
Posts: 9515
Location: Southern Maryland
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| Posted: Thu Oct 30, 2014 5:17 pm Post subject: |
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People have been known to run 12:1 on the street with pump gas and the right pistons... Like Jake is so fond of saying: it's all in the combo. I would say it's all in your tuning ability, but the parts help out a little too. If you can't tune a Briggs engines, you probably shouldn't be driving a VW either.
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| satterley_sr wrote: |
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vugbug68
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Joined: June 25, 2006
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Location: sacramento
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| Posted: Thu Oct 30, 2014 7:28 pm Post subject: |
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My 2109cc has 9.2:1 compression and I cant tell any difference with 87, 89, or 91 gas, not in performance or mpg.
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Joel
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Posts: 11099
Location: NSW Australia
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| Posted: Thu Oct 30, 2014 11:55 pm Post subject: |
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| vugbug68 wrote: |
| My 2109cc has 9.2:1 compression and I cant tell any difference with 87, 89, or 91 gas, not in performance or mpg. |
What have you got for an ignition system?
You cant just change fuel octane and off to grandmas we go, the timing needs to be optimized for whichever fuel you run.
if you set the timing for regular then stick a tank of premium in its gonna run like a bag of shit, you are not going to get the benefit of higher octane fuel, its a slower burn and needs to more advance
Modern cars ECUs can compensate by altering the timing but youll need to time a vw for max advance with no knock on whichever fuel you run.
I always ran mine on 95 which I think is equivalent to 91 in the US, better mpg than on regular so the price at the bowser balanced out
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earthquake
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Joined: January 10, 2008
Posts: 3984
Location: SANDY VALLEY, NEVADA
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| Posted: Fri Oct 31, 2014 12:08 am Post subject: |
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5-7 HP would be about a 10% increase on a stock 1600, I would see it on a dyno or a 0-50 mph test.
Casey
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Quokka42
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Joined: December 02, 2010
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Location: Melbourne, Australia
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| Posted: Fri Oct 31, 2014 2:57 am Post subject: |
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The main problem with running too high a compression ratio for your configuration is you usually end up running rich and/or backing off the advance to compensate. Running optimum CR will allow you to run leaner and produce a crisper more efficient engine behaviour.
9:1 is fine on some engines - disastrous on a stocker.
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vugbug68
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Joined: June 25, 2006
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Location: sacramento
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| Posted: Fri Oct 31, 2014 8:03 am Post subject: |
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| Joel wrote: |
| vugbug68 wrote: |
| My 2109cc has 9.2:1 compression and I cant tell any difference with 87, 89, or 91 gas, not in performance or mpg. |
What have you got for an ignition system?
You cant just change fuel octane and off to grandmas we go, the timing needs to be optimized for whichever fuel you run.
if you set the timing for regular then stick a tank of premium in its gonna run like a bag of shit, you are not going to get the benefit of higher octane fuel, its a slower burn and needs to more advance
Modern cars ECUs can compensate by altering the timing but youll need to time a vw for max advance with no knock on whichever fuel you run.
I always ran mine on 95 which I think is equivalent to 91 in the US, better mpg than on regular so the price at the bowser balanced out |
I have the CB magnaspark distributor and the coil that goes with it. I'm not saying to just run whatever gas, but I've tried several different timings and tuning with each type of gas and I really cant tell the difference. My friends squareback with a 1600 and dual carbs needs to run 91 or it will ping. My 1760cc spare engine runs best on 89 gas and 29 btdc. The 2109 has a nice powerband and gets 25mpg so I cant complain
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mark tucker
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Joined: April 08, 2009
Posts: 23937
Location: SHALIMAR ,FLORIDA
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| Posted: Fri Oct 31, 2014 10:12 am Post subject: |
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I have around that 100000 miles on 10.4 cr. is it worth it????? I dont realy know I havent run it at a lower cr.  but I am in LA on the west coast where things are a bit different than most of the rest of the country. |
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miniman82
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Joined: March 22, 2005
Posts: 9515
Location: Southern Maryland
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| Posted: Fri Oct 31, 2014 2:19 pm Post subject: |
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We know, the dynos are very generous over there.
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| Glenn wrote: |
| satterley_sr wrote: |
I just wanted to bitch but I'm getting no sympathy. |
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Alstrup
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Joined: July 12, 2007
Posts: 7214
Location: Videbaek Denmark
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| Posted: Fri Oct 31, 2014 4:27 pm Post subject: |
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1600 sgl port. Stock cam, stock heads apart from a 3 angle valve job and a 30 degree cut back on intake valves. 8,3-1 CR. 34 mm Pict3 on US sgl port manifold. NOS stock VW Germany exhaust.
Almost 10 hp over stock. It is rated 46 hp DIN IRL they typically pull 46-48 hp.
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RailBoy
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Posts: 2904
Location: Virginia
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| Posted: Fri Oct 31, 2014 6:38 pm Post subject: |
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Rather have a Bronze Lifter Bores and a Whapping Cam and then I consider the 5-7 HP Hype of the compression ratios...
Thing is Then for Sure you are into H-Beams and Big Heads......
All I am saying is for the street, most do it for talk, I know one thing, most don't dare the roads, they just do it for the strip...
Cal Lookers...... Go Straight.....
Love to do this Engine above for a German Looker, Engine run gas, motors run amps..... 
Shalimar, you know what I am getting at here...... Ever done a German Looker? RB
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[quote="smitty24"]"HELP, I ported my own heads and now have fire coming out my ass" .[/quote]
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Quokka42
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Joined: December 02, 2010
Posts: 3117
Location: Melbourne, Australia
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| Posted: Fri Oct 31, 2014 7:13 pm Post subject: |
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Nice engine, Torben. What octane do you run in that? I've run 8.2 in a "stock" engine, but with 95RON and a little work on the chambers.
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Alstrup
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Location: Videbaek Denmark
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| Posted: Fri Oct 31, 2014 7:18 pm Post subject: |
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95 octane Euro fuel. About equivallent to 91 US fuel.
One thing I did not menthion above, more or less deliberately, was that I machined the cylinders 0,5 mm to get 1,05 mm deckheight, which is also part of the reason for the torque and a cool running engine.
T |
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