2110 Compression Ratio Suggestions

Matt Harris · Post by **Matt Harris** » Sun Oct 21, 2001 10:19 pm

I don't know. Those 36's w/ 34 vents would be OK I guess. I'm not sure. But with a 2110 and the 40x35.5 heads, you have displacement and headwork on your side to combat the bigger cam and smaller carbs. I have a 2007cc with 42 dcnf's and they have 34 vents and I have an engle 120 cam which is just a little smaller than a 109 I think. Use what cam you would feel more comfortable using.

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Matt Harris
78 x 90.5
2007cc
1971 Super

[This message has been edited by Matt Harris (edited 10-21-2001).]

JohnConnolly · Post by **JohnConnolly** » Sun Oct 21, 2001 10:54 pm

If anyone is intersted, we are experimenting with a new piston/head combination, that I feel will allow relatively HIGH compression. These custom pistons are NOT CHEAP (plan on $600/4, including rings), but are a true forged piston.

I'm not releasing any details, but my "test crew" will be pretty small and select, and secrecy is paramount until development is over. I don't want pics getting out before we are done, or we'll have unqualified Taiwan/Chinese copies in 3 mos, and my efforts will be squished (pun intended).

No guarantees, but I expect 12:1 on pump gas no problem, though ignition timing requirements will be vastly different than "conventional AC VWs".

The only thing I'll reveal is they require a deck of .040" or so (I know one guy running .028" to 7500, NO PROBLEM), NO MORE or detonation can result.

Contact me via e-mail if you are interested, AND if you have the $ to play with these things.

John Connolly
Aircooled.Net Inc.

James2 · Post by **James2** » Mon Oct 22, 2001 5:26 am

Well, here's my last two cents. my motor was built with 7-1 CR. I went to 7.6-1 soon after I installed the motor.

It runs the same temp, gets slightly better MPG and has more power.

CLKWRK · Post by **CLKWRK** » Fri Oct 26, 2001 3:05 pm

Im reading all this talk of compression ratios, and im thinking "I must be nuts" cause im running 10.5:1 on the street in my 2180, with no ping. Im lovin the power

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Fri Oct 26, 2001 6:35 pm

Clark, you are not nuts, you are a smart man, that does not believe everything he reads, and thinks for himself....Power on, man!

BergRace · Post by **BergRace** » Sat Oct 27, 2001 11:01 am

It seems that some of our American friends have forgotten the fact that VW designed the AN T4 engine with a 8.6:1 C.R.
This for the rather big 412 S, a family estate wagon.
Yes, there are different qualitys of gazoline, but not to make up for this hysteria of running less than 7.5:1 in a standard T1.

Jørn Berg.

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Sat Oct 27, 2001 1:53 pm

Berg Race thats correct and it was the strongest aircooled engine ever offered by VW, proof that CR is a factor for performance..I'm not afraid of CR, it has been my friend.

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Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com

Bruce2 · Post by **Bruce2** » Sat Oct 27, 2001 1:54 pm

The current Mexican engines are at 7.75:1 as Dan stated above, but this is not achieved with tons of deck height. They get it with domed hi-comp pistons.
"you only have to look at the history of factory c.r. settings to see what your limits are... it's ranged from something like 5.8:1 to 7.3:1, to the 6.6:1 that mexico used for their dual-port motors... that was where gene berg got his low c.r. recommendations in the '80's... kids, he didn't pull those numbers out of a hat."
The 6.6:1 CR in the older Mexican engines is a big red herring. Its completely irrelevant to anyone north of the Rio Bravo. The reason they used such a low CR was their poor fuel way back. It was somewhere around 75 octane. Today the pumps in Mex read 87 for Magna, and 93 for Premium. These numbers are accurate since my 8:1 2 liter was just as happy as on 87 up here. Gene quoted this irrelevant CR info knowing most Americans wouldn't know the real reason.
If you read his CR ramblings carefully, you will also see he says the min octane for a stock Bug is 91, it says so on the gas filler door. Again he clouds the true facts in favour of his rediculous low CR. The number on the gas door is measured on the RON scale, which comes out to 87 on today's scale. So no, Gene, you don't need to use hi octane in a stock 7.5:1 Bug.
IMO the reason Gene preached silly low CRs is so your engine makes very little power and lives a very long life. This makes most customers happy.

danimal · Post by **danimal** » Sat Oct 27, 2001 2:05 pm

>>>It seems that some of our American friends have forgotten the fact that VW designed the AN T4 engine with a 8.6:1 C.R.<<<

"For most cars run on the street, I recommend running the 7.3:1 compression ratio that most Type 4 motors were setup from the factory. This CR should not cause detonation under 99.9% of the driving conditions. The Transporters came with this CR and they run quite strong and cool if not driven at low rpms. The high end of my suggestion is the 8.3:1 CR in the early 411s and 914s." -tunacan.net

it seems that some of our european friends are not posting the entire truth regarding type 4 compression ratios.

it's not relevant anyway, because even with people claiming things like "24% more fin area" and much greater cooling fan volume, type 4 heads still have a bad rep in the vw industry for cracking.

one other bit of info regarding semi-hemi vw heads: not all semi-hemi cutters are the same... i have seen two different styles of cut, and i have heard of three different cutters being used... the variations revolve around how deep the cut is, vs. the diameter.

356 heads notwithstanding, i'd be looking for the cut that leaves the most squish area, if i was running semi-hemi again.

dan
oceanstreetvideo.com

BergRace · Post by **BergRace** » Sun Oct 28, 2001 11:20 pm

"it seems that some of our european friends are not posting the entire truth regarding type 4 compression ratios" ???
I specified the AN engine, any official VW tech will confirm its C.R. of 8.6:1.
Even the Haynes manual on the 411 & 412 (#091) will tell you this.

Jørn Berg.

danimal · Post by **danimal** » Tue Oct 30, 2001 5:01 pm

>>>The 6.6:1 CR in the older Mexican engines is a big red herring. Its completely irrelevant to anyone north of the Rio Bravo. The reason they used such a low CR was their poor fuel way back. It was somewhere around 75 octane.<<<

the '80's beetles that had 6.6:1 c.r. were factory-recommended to run 88 octane fuel.

and yes, mexican gas has always been lousy, but it did get better in 1990, when they went to magna sin, and most recently with the new premium gas.

i have lived in carlsbad since 1976, i used to make numerous surf trips to mexico, i do not ever recall seeing 75 octane posted at the pumps... so you are just speculating... but you are right about the gas being lousy.

>>>Gene quoted this irrelevant CR info knowing most Americans wouldn't know the real reason.<<<

gee, bruce tweedle(?), do you think gene was part of some giant conspiracy?

>>>If you read his CR ramblings carefully, you will also see he says the min octane for a stock Bug is 91, it says so on the gas filler door. Again he clouds the true facts in favour of his rediculous low CR. The number on the gas door is measured on the RON scale, which comes out to 87 on today's scale<<<

if you had read his cr ramblings carefully, you'd know that he is lamenting the fact that lead is no longer used as an octane enhancer... very few people understand how octane really works, and what effect things like oxygenated gas have on our carbed acvw engines... instead, they blindly claim that 87 octane equals 91 ron.

>>>I specified the AN engine, any official VW tech will confirm its C.R. of 8.6:1.
Even the Haynes manual on the 411 & 412 (#091) will tell you this.<<<

i believe you.

but my point is that one bastard high c.r. figure, used in very low volume, is hardly relevant... try this: which type 4 heads crack the worst, which car were they run in, and at what factory c.r.?

perhaps you could try finding used, uncracked porsche 2.0 heads... then ask yourself where they are screwed up; it certainly wasn't the 23% extra fin area, or the high-volume cooling fan, or even the lightweight car that they were run in.

what's left? either an awful design parameter(s), and/or too high of a c.r...

dan
oceanstreetvideo.com

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Tue Oct 30, 2001 6:17 pm

which is worse?

(1) A performance without enough punch to burn the fuel it can induct, it may last a while, but runs rich, gets crappy mileage and takes one of every size jet made to tune it.

(2) A performance engine that may have a SLIGHTLY shorter life, make gobs of CLEAN power and dials right in with a couple of tweeks of the carbs?

If you want to run something with low CR, grab a 36HP and go for it...One thing is for sure the starter will outlast the car if ran at 6.6:1 CR, sad thing is that it probably makes more power than the engine does!

The world is so gullible to waht is printed within the pages of a book!

jmillheiser · Post by **jmillheiser** » Tue Oct 30, 2001 9:52 pm

that 2110 seems really REALLY mild.

on a 2110 id run a engle 120 or web cam with similar specs. and i would certainly run bigger carbs than 36 dells. id run 45 dells or 48 IDFs on an engine that big. from what ive herd the 120 on a 82 stroke engine will produce a tourque monster that will pull to 6500RPM and will drive just fine with stock gear ratios i.e. great steet engine. a more aggressive cam will likely require a close ratio gearbox to stay in its powerband and will have an 8000RPM powerband i.e. great race engine not so good on the street.

of course you want good heads with a good porting job(have somone who has a good rep for their porting jobs on VW heads do it).

if you look at those WC semi-hemi heads and compare taht to a semi-hemi cut acvw head you will notice some major differences.

on the semi-hemi cut acvw heads the head is cut above the valves to your sticking the valves toward the bottom of the combustion chamber instead of keeping them at the top(where they should be). on the WC engines that you showed pics of the head was designed to be a semi-hemi from the factory so the valves are in the right place. chrysler has actually run semi-hemi heads on most of its v6 engines since the early 90s. it is done to keep the CR at a reasonable level on those engines while keeping the production tolerances tight. and remember these engines are very different from an acvw engine. all the chrysler semi-hemis have small bores and long strokes like most newer engine designs.

the explination of the semi-hemi on acvws that i have herd over and over again was it was a cheap way to lower CR without running excessive deck heights.

yeahmag · Post by **yeahmag** » Wed Oct 31, 2001 12:05 pm

Ok... Here is the update on the engine.

2276 (82x94)
Scat I Beam rods
WebCam 121/125
Fancy pants lifters with the hole in 'em
around 9.0:1 CR
AJ Simms heads 42x37 full p&p matched manifolds
New Case (RIMCO machine work)
Dog house
Full flowed
1.5 deep sump
(external cooler by summer time)
Still the 36 Dells until more $ is available

[This message has been edited by yeahmag (edited 10-31-2001).]

JohnConnolly · Post by **JohnConnolly** » Wed Oct 31, 2001 12:20 pm

that things' gonna haul arse.

John